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1
Xu, Qingyun, Jian-Biao Bai, Shuai Yan, Rui Wang, and Shaoxu Wu. "Numerical Study on Soft Coal Pillar Stability in an Island Longwall Panel." Advances in Civil Engineering 2021 (January 29, 2021): 1–13. http://dx.doi.org/10.1155/2021/8831778.
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Roadway support and management of longwall panels in an island soft coal panel are always difficult work. In a test mine, stress distribution, deformation characteristic, and plastic zone distribution around the roadway and coal pillars in the development and mining periods were investigated with respect to the widths of different coal pillars using theoretical and simulation methods. The most reasonable width of coal pillars was comprehensively determined, and the field test was conducted successfully. The results show that a reasonable width of coal pillars is 7.0–8.2 m using the analytical method. The distribution of vertical stress in the coal pillars showed an asymmetric “double-hump” shape, in which the range of abutment pressure was about 26.0–43.0 m, and the roadway should be laid away from stress concentration. When the coal pillar width is 5.0–7.0 m, deformation of the roadway is half that with 8.0–10.0 m coal pillar in the development and mining period. The plastic zone in the surrounding rock firstly decreases and increases with increasing coal pillar width; the smallest range occurs with a coal pillar width of 5.0 m. Finally, a reasonable width for coal pillars in an island panel was determined to be 5.0 m. Industrial practice indicated that a coal pillar width of 5.0 m efficiently controlled deformation of the surrounding rock, which was an important basis for choosing the width of coal pillars around gob-side entries in island longwall panels with similar geological conditions.
2
Zhang, Ming, Chen Cao, and Bingjie Huo. "Ground Stress Distribution and Dynamic Pressure Development of Shallow Buried Coal Seam Underlying Adjacent Room Gobs." Shock and Vibration 2021 (August 6, 2021): 1–11. http://dx.doi.org/10.1155/2021/8812933.
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The condition of the coal pillars remained in the room-and-pillar gobs is complicated. The stresses loaded on the pillar floor may be transmitted and overlapped. It changes the stress environment of the lower coal seam roof, leading abnormal periodic weighting. In the procedure of coal seam 3−1 mining in the Huoluowan Coal Mine, the ground stress is high while the working face passing through the room pillars of overlying coal seam 2−2, leading to hydraulic shield being broken. In this paper, theoretical analysis, numerical calculation, and similar material simulation were used to analyse the stress environment of lower seam and the effect of coal pillars remained in close-distanced upper seam. The stress transfer model was established for the room pillars of coal seam 2−2, and the stress distribution of underlying strata was obtained based on theoretical analysis. The joint action of dynamic pressure of high stress-coal pillar with movement of overlying rock strata in the working face 3−1 under the coal pillar was revealed. The results showed that the horizontal stress and vertical stress under the large coal pillar of the room gob in coal seam 2−2 were high, being from 9.7 to 15.3 MPa. The influencing depth of vertical stress ranged from 42 m to 58 m. The influencing depth of horizontal stress ranged from 10 to 23 m. The influencing range of the shear stress was from 25 to 50 m. When the working face 3−1 was mined below the coal pillar of 20 m or 50 m, abutment pressure was relatively high. The stress concentration coefficient reached 4.44–5.00. The dynamic pressure of the working face was induced by the stress overlying of the upper and lower coal seams, instability of the inverted trapezoid rock pillar above the coal pillar, and collapsing movement of the roof. The studying results were beneficial for guiding the safety mining of the coal seam 3−1 in the Huoluowan Coal Mine.
3
Le Quang, Phuc, Vladimir Zubov, and Thang Pham Duc. "Design a Reasonable Width of Coal Pillar Using a Numerical Model. A case study of Khe Cham basin, Vietnam." E3S Web of Conferences 174 (2020): 01043. http://dx.doi.org/10.1051/e3sconf/202017401043.
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Problems in surrounding rock displacement, roadway deformation and complex support are the hallmarks of the long wall mining system. Such problems seriously affect the safety and efficient production of coal mines. To control the deformation of the rocks around the roadway next to the goaf, to reduce the support pressure, in Vietnamese underground mines often leave supporting coal pillars. Identification of a reasonable design for roadway supporting pillars by a numerical simulation study was conducted under the geological and technical foundation of I-10- 2 working faces at the Khe Cham coal mine, Vietnam . The characteristics of stress and pressure distribution of roof layers on coal pillars are modeled under different pillar widths. The results show a great linear increase of the vertical stress on the narrow coal pillar and as the width of the coal pillar increases, the area of the elastic core area also increases and the level of stress increase tends to be stable without any apparent uptrend. Coal pillar deformation decreases with increasing coal pillar width, but it leads to large coal loss and waste of resources. Therefore, with the current supporting solutions to increase the stability of the coal pillar, the size range of a coal pillar is determined to be 6-8 m through numerical simulation. The conclusions obtained may provide a certain reference number to choose the logical location of the furnace lines under similar geological conditions.
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Zhou, Zong Hong, Ke Peng Hou, and Feng Yu Ren. "Numerical Simulation of Ground Pressure Activity Caused by Orebody Mining under Road." Advanced Materials Research 462 (February 2012): 407–12. http://dx.doi.org/10.4028/www.scientific.net/amr.462.407.
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There is the Jinggu-Minle road to cross through the No. 3 ore clusters in Songjiapo copper mine. The surface ground deformation and strata movement caused by underground mining will threaten the road transportation safety, which doesn’t allow collapse. Using numerical simulation method, the ground pressure activity and deformation, movement mechanism of strata were analyzed under different mining methods. Moreover, some control measures such as reserving insulating pillar and point pillars were put forward to maintain the stability of mined-out areas and the surface road. An optimal mining scheme was recommended. The results showed that the mining process of No. 3 ore clusters can’t cause direct failure to road, and the failure of hanging wall rock will have indirect influence to the road with the lapse of time. Reserving the insulating pillar, top pillar and point pillars can effectively reduce the plastic area range of hanging wall and strata failure in the mining process. The results can provide theoretical basis for the actual mining design and rock strata control.
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Sun, Binyang, Pingsong Zhang, and Haifeng Lu. "Study on Reasonable Size of Coal and Rock Pillar in Dynamic Pressure Roadway Segment of Fully Mechanized Face in Deep Shaft." Advances in Civil Engineering 2020 (October 10, 2020): 1–10. http://dx.doi.org/10.1155/2020/8822175.
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The deformation mechanism of the protective coal and rock pillar area outside a stope is an important parameter for setting a reasonable size. In this paper, based on the geological condition of working face 1231(1) in a mine in Huainan, a method that combines the use of a borehole and Brillouin optical time domain reflectometry (BOTDR) was proposed to analyze the stress variation laws of coal and rock pillar areas, and the parameters of the monitoring borehole and installation technique of the sensing optical cables were designed. Based on the monitoring data, the strain distribution characteristics of the sensing optical cables and their relationship with the rock strata were analyzed, the development law of coal and rock strata deformation during the mining process was revealed, and the transverse influence range of the coal and rock pillar affected by mining was reasonably divided. According to the results, the sensing optical cables show an overall trend of tensile strain, with a maximum value of 1800 με, and the main areas of rock strata deformation occur near the interface of rock strata. The range of rock strata disturbance along the borehole direction was approximately 38 m, and the maximum deformation of rock strata after the disturbance, namely, the displacement, was 24.87 mm. A numerical model was constructed to acquire the strain variation characteristic within 100 m in the outer floor of the working face. The transverse range of the floor disturbance was analyzed to be 30–36 m. The field test had good correspondence with the numerical simulation results, which indicates that the optical fiber testing technology can effectively describe the stress variation in the coal and rock strata. The test results can provide technical support for the rational setting of coal and rock pillars and disaster prevention and control. The research direction of deep rock mass testing is discussed, and optical fiber testing in boreholes is considered an effective method for studying deep dynamic disaster control.
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Zhang, Hai Bo, and Ya Jie Chen. "Study on the Mechanism of Backfill and Surrounding Rock of Open Stope during Subsequent Backfill Mining." Advanced Materials Research 753-755 (August 2013): 452–56. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.452.
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In order to analyze the mechanism of backfill and surrounding rock of open stope during subsequent backfill mining, take M1 ore body mining in a mine as engineering background, and simulate the mechanism of surrounding rock and backfill by using FLAC3D numerical software. Results show that the backfill can effectively alleviate or transfer the stress concentration state of the room floor and pillar, apparently restrain the displacement of the cavity plate and pillar, and improve the plasticity distribution range in a limited degree.
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Zhao, Shu Guo, Wei Dong Song, Wen Bin Xu, and Huan Hu Song. "Simulation Study on the Stability of Mining Thin Flat-Grade Iron Ore Body with Hydraulic Support Longwall Method." Applied Mechanics and Materials 170-173 (May 2012): 3706–10. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.3706.
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This paper proposed hydraulic support longwall method for mining glacis thin orebody. The DaZhuang ore section of Guandian Ore Mining whose orebody in the line of -8＇—-16＇was chosen as the research object. It applied the FLAC numerical simulation method to study the changes of surrounding rock stress in the mining face, displacement and plastic zones, and put forward the changing law of the rock stress, displacement and plastic zones in the mining process. Besides, it proved that the mechanical condition of the roofs changed in different stages. When the distance between pillar and mining face was in the range of 4m—8m, the state was relatively stable, and the pillar and surrounding rocks were in small range of shearing and tensile yield. When distance was 12m, the roof suffered from compression. When it was up to 16m, the roof and bottom rock displayed tension. However，the appreciation of stress changed very little at different stages. The stress concentration circle formed between the top and bottom of the pillar, and the unloading appeared in the top and bottom gap. The nearer to the coal face, the more powerful of stress concentration, and the influence of pillar’s position on stress concentration degree is very little in the front of coal face. The structure would be in stable equilibrium when the distance between single stent and coal face is 12m. In such circumstances, the security of roof would be improved if more stents are added
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Jiang, Li-li, Zeng-qiang Yang, and Gang-wei Li. "Research on the Reasonable Coal Pillar Width and Surrounding Rock Supporting Optimization of Gob-Side Entry under Inclined Seam Condition." Advances in Civil Engineering 2021 (May 19, 2021): 1–13. http://dx.doi.org/10.1155/2021/7145821.
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In order to study the optimal coal pillar width and surrounding rock control mechanism of gob-side entry under inclined seam condition, the 130205 return air entry adjacent to 130203 gob in Yangchangwan No. 1 well is taken as a typical engineering background. By means of engineering background analysis, theoretical analysis based on inside and outside stress field, numerical simulation by FLAC3D software, and in situ industrial test and relevant monitoring methods, the optimal coal pillar width and surrounding rock control technology are obtained. The results show that the influence range of inside stress field is about 12.2∼12.8 m based on theoretical calculation result; under the influence of 10 m coal column, the overall deformation of the roadway is relatively small and within the reasonable range of engineering construction, so the width of the coal pillar along the return air roadway is set to 10 m which is more reasonable; the cross-section characteristics of special-shaped roadway lead to asymmetric stress distribution and fragmentation of surrounding rock, and then the asymmetric surrounding rock control technology under the coupling effect of roof prestressed anchor + high-strength single anchor cable + truss anchor cable support is proposed. The monitoring results of this support method are effective for the maintenance of gob-side entry, and the study conclusions provide new guidance for the surrounding rock control mechanism of gob-side entry under inclined seam conditions.
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He, Fulian, Zheng Zheng, Hengzhong Zhu, and Bo Yang. "Research on Failure Mechanism and Strengthening of Broken Roadway Affected by Upper Coal Pillar." Advances in Civil Engineering 2019 (April 1, 2019): 1–13. http://dx.doi.org/10.1155/2019/8132817.
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The principal stress difference is introduced as a new evaluation index in order to better understand the failure mechanism of roadways affected by upper coal pillars and characterize failure of rock mass. Compared with traditional methods, it facilitates quantitative analysis. Moreover, we combine the semiplane theory and we obtain the stress distribution on the coal pillar’s bedrock and the strengthening control area from the “change point” position along a 21 m horizontal line. The influence of multiple stresses induced from mining on a roadway is analyzed. It is found that rock failure is most likely while mining the 051606 working face, followed by mining the 051604 working face, and the stress influence on the upper pillar has the lowest failure probability. In addition, based on the asymmetry of the surrounding rock stress distribution, this study proposes strengthening control technology of surrounding rock on the basis of a highly stressed bolting support and anchor cable, adding to the steel ladder beam, steel mesh, and shed support’s protective function to the roadway’s roof and ribs. Finally, through field observations, it is concluded that the roadway deformation is within the controllable range.
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Skrzypkowski, Krzysztof. "Decreasing Mining Losses for the Room and Pillar Method by Replacing the Inter-Room Pillars by the Construction of Wooden Cribs Filled with Waste Rocks." Energies 13, no. 14 (July 10, 2020): 3564. http://dx.doi.org/10.3390/en13143564.
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The article presents methods of securing mining excavations using wooden cribs. For the underground room and pillar method used to excavate zinc and lead ore body in the Olkusz-Pomorzany mine in Poland, model tests for the replacement of rock pillars by wooden cribs are presented. In the first stage of research, the results of laboratory strength tests carried out on models of four-point, six-point and eight-point cribs made of wooden beech beams at a 1:28 scale arranged horizontally were determined. For the first time, a concave round notch connection was used to connect the beams of the wooden cribs. The maximal capacity of cribs consisting only of beams and filled with waste rocks taken from underground mining excavations was determined. In addition, the vertical deformations of the cribs at maximal loading force and their specific deformations are presented. Additionally, on the basis of load-displacement characteristics, the range in variability of the stiffness of empty cribs and those filled with waste rocks was calculated as a function of their compressibility. In the second stage of research, the room and pillar method was designed in the Phase2 numerical program. The aim of the study was to determine the stresses in the inter-room pillars. Based on the results of laboratory and numerical tests, a factor of safety was determined, indicating that it is possible to reduce mining losses while maintaining the safe exploitation conditions of the ore body.
11
Skrzypkowski, Krzysztof. "The Influence of Room and Pillar Method Geometry on the Deposit Utilization Rate and Rock Bolt Load." Energies 12, no. 24 (December 13, 2019): 4770. http://dx.doi.org/10.3390/en12244770.
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In this article, a model of ore deposit in form of a lense carried out in the MineScape program, is presented. The lense had a thickness of 30 m, length along the strike 200 m, and the depth buried was for 80 m to 110 m below the surface. In the first layer, counting from the lowest level, a room and pillar method with variable geometry was designed. The width and length dimensions for rooms and pillars were: 4 m, 5 m and 6 m, respectively. For the selected part of the deposit, three variants of the system with variable geometry of rooms and pillars were designed, for which the deposit utilization coefficient was determined. The next stage of the research was to determine the influence of the geometry of the pillars and rooms on the range of the rock destruction zone around room excavations. For this purpose, numerical calculations using the three-dimensional Examine 3D program, based on the boundary element method, were made. The results of numerical tests were used to calculate the load of the rock bolt support, which is currently used in the zinc and lead underground mine “Olkusz-Pomorzany” in Poland. Currently in the mine, the bolt spacing is 1 m × 1 m, and the technology for fixing the bolt rod is based on resin cartridges that completely fill the bolt hole. In order to spread the spacing of the rock bolt support and to apply segmental fixing of the bolt rod, in the laboratory tests, rock bolt supports with increased strength were tested. Based on the results obtained, it was found that the rock bolt can be installed segmentally, using a cement grout, and its spacing can be increased to 2 m.
12
Chen, Dongdong, Chunwei Ji, Shengrong Xie, En Wang, Fulian He, Qiong Cheng, and Qing Zhang. "Deviatoric Stress Evolution Laws and Control in Surrounding Rock of Soft Coal and Soft Roof Roadway under Intense Mining Conditions." Advances in Materials Science and Engineering 2020 (June 22, 2020): 1–18. http://dx.doi.org/10.1155/2020/5036092.
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Aiming at the problem of large deformation and instability failure and its control of soft coal and soft roof roadway under intense mining, laboratory experiments, theoretical calculations, Flac3D numerical simulation, borehole peeping, and pressure observation were used to study the deflection characteristics of the deviatoric stress of the gas tailgate and the distribution and failure characteristics of the plastic zone in the mining face considering the strain softening characteristics of the roof and coal of roadway, and then the truss anchor cable-control technology is proposed. The results show the following: (1) The intense mining influence on the working face will deflect the peak deviatoric stress zone (PDSZ) of the surrounding rock of the gas tailgate. The influence distance of PDSZ is about 20 m in advance and 60 m in lag; the PDSZ at the gob side of the roadway is located in the range of 3–5.5 m from the surface of the coal pillar, while the coal wall side is mainly located in the range of 3–4.5 m at the shoulder corner and bottom corner of the solid coal. (2) The intense mining in the working face caused the nonuniform expansion of the surrounding rock plastic area of the gas tailgate. The two shoulder angles of the roadway and the bottom of the coal pillar have the largest damage range, and the maximum damage location is the side angle of the coal pillar (5 m). Angle and bottom angle of coal pillar are the key points of support control. (3) The plastic failure line of the surrounding rock of the gas tailgate is always between the inner and outer contours of the PDSZ, and the rock mass in the PDSZ is in a stable and unstable transition state, so the range of anchor cable support should be cross plastic failure line. (4) The theoretical calculations and numerical simulation results agree well with the drilling peep results. Based on the deflection law of the PDSZ and the expansion characteristics of the plastic zone, a truss anchor cable supporting system with integrated locking and large-scale support function is proposed to jointly control the roof and the two sides, which effectively solves the problem of weak surrounding rock roadway under severe mining deformation control problems realizing safety and efficient production in coal mines under intense mining.
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Skrzypkowski, Krzysztof, Waldemar Korzeniowski, Krzysztof Zagórski, and Anna Zagórska. "Adjustment of the Yielding System of Mechanical Rock Bolts for Room and Pillar Mining Method in Stratified Rock Mass." Energies 13, no. 8 (April 21, 2020): 2082. http://dx.doi.org/10.3390/en13082082.
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The article presents a novel yielding mechanism, especially designed for the rock bolt support. Mechanical rock bolts with an expansion head and equipped with one, two, four and six dome bearing plates were tested in the laboratory conditions. Furthermore, in the Phase2D numerical program, five room and pillar widths were modeled. The main aim of numerical modeling was to determine the maximal range of the rock damage area and the total displacements in the expanded room. The models were made for a room and pillar method with a roof sag for copper ore deposits in the Legnica-Głogów Copper District in Poland. Additionally, in the article a load model of the rock bolt support as a result of a geomechanical seismic event is presented. Based on the results of laboratory tests (load–displacement characteristics), the strain energy of the bolt support equipped with the yielding device in the form of dome bearing plates was determined and compared with the impact energy caused by predicted falling rock layers. Based on the laboratory tests, numerical modeling and mathematical dynamic model of rock bolt support, the dependence of the drop height and the corresponding impact energy for the expanded room was determined.
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Yang, Hengze, Zhongping Guo, Daozhi Chen, Chao Wang, Fuyu Zhang, and Zhaowen Du. "Study on Reasonable Roadway Position of Working Face under Strip Coal Pillar in Rock Burst Mine." Shock and Vibration 2020 (November 2, 2020): 1–21. http://dx.doi.org/10.1155/2020/8832791.
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It is of great significance to study the reasonable position of mining roadway under strip coal pillar for increasing the stability of mining roadway, reducing the waste of resources, and realizing the safety production of working face. Based on the research background of the working face under the strip coal pillar in Jinqiao Coal Mine of Jining, Shandong Province, through theoretical analysis, similar material simulation experiment, and numerical simulation experiment, the stress distribution law, plastic failure range, and rationality of coal pillar setting in different width sections are systematically studied. Finally, the tailentry of working face is determined at the position of 5 m from the bottom of strip coal pillar to 1308 goaf. During the mining period of 1310 working face, the peak value of side abutment pressure is at the position of 3∼4 m; beyond 25 m in front of the coal wall, the deformation of the surrounding rock on the tailentry surface is small. After entering the advanced support section, the deformation of the two sides is mainly longitudinal crack expansion and local shallow small flakes; however, the roof is complete and stable. Therefore, the selection of tailentry location and coal pillar width has played a good role. The research results of this study can provide some reference for similar mine with similar geological and production technical conditions.
15
Talbot, Joy M., A. F. Mark, and J. Bastow Wilson. "Vegetation-environment relations in snowbanks on the Rock and Pillar Range, Central Otago, New Zealand." New Zealand Journal of Botany 30, no. 3 (July 1992): 271–301. http://dx.doi.org/10.1080/0028825x.1992.10412908.
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Wu, Quansen, Peng Kong, Quanlin Wu, Xinggang Xu, Xingyu Wu, and Tao Guo. "Study on Overburden Rock Movement and Stress Distribution Characteristics under the Influence of a Normal Fault." Advances in Civil Engineering 2020 (September 19, 2020): 1–16. http://dx.doi.org/10.1155/2020/7859148.
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Fault activation triggers local deformation and dislocation, releasing a large amount of energy that can easily cause mining disasters, such as rock bursts and roadway instability. To study the changing characteristics of overburden structures and the evolution law of mining-induced stress as panel advances towards a fault from a footwall, two similar models were established, namely, a simulation experimental model and a numerical simulation model. In addition, the relationship among mining, mining stress, and rock bursts induced by fault activation was investigated. The results of this study reveal that when the working face is 30 m away from the fault, the high-position rock mass near the fault turns to the goaf where the fault is activated, and the two walls display relatively obvious dislocation. During the process of footwall panel mining to the fault, the abutment stress of the coal pillar tends to increase initially, followed by a decrease. When the working face is 20 m away from the fault, the abutment stress ahead of the working face reaches its maximum. When the width of the coal pillar is within the range of 10–40 m, the coal pillar accumulates a large amount of energy, and the working face affected by the fault easily induces a rock burst. Before fault activation, disturbances arising from the mining activities destroy the equilibrium stress environment of the rock system surrounding the fault, and the fault continuously accumulates energy. When the accumulated energy reaches a certain threshold, under the action of normal stress or shear stress, the fault will be activated, and a large amount of energy will be released, which can easily induce a rock burst. The research results in this paper provide a scientific basis for the classification, prediction, and prevention of rock bursts under similar geological conditions.
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Skrzypkowski, Korzeniowski, Zagórski, and Zagórska. "Flexibility and Load-Bearing Capacity of Roof Bolting as Functions of Mounting Depth and Hole Diameter." Energies 12, no. 19 (September 30, 2019): 3754. http://dx.doi.org/10.3390/en12193754.
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This paper presents the results of laboratory tensile testing of segmentally-installed glue-in roof bolting. We studied roof bolting of the type Olkusz-16A (Boltech Sp. z o.o., ZGH Bolesław S.A., Bukowno, Poland), additionally equipped with a steel rod coil, which was mounted in steel cylinders filled with a concrete mixture using multi-part resin cartridges with a diameter of 0.024 m and length of 0.045 m. The mounting depths were 0.1 m and 0.2 m, respectively. Our main purpose was to determine the effect of the bolt hole diameter, which assumed the values 0.028 m, 0.032 m, 0.035 m, and 0.037 m, respectively, on the load-bearing capacity of the roof bolting in relation to the mounting depth. We found that the mounting depth of 0.2 m was sufficient for the roof bolting to exhibit its full load and displacement properties for all four diameters of the bolt hole. To determine whether the roof bolting was capable of transferring the load in situ, we presented the results of the predicted load on the roof bolting applied in a room and pillar mining method in an underground mine of zinc and lead ore deposits. Our objective was to determine the influence of the room and pillar mining method geometry on the range of the fault zone of rocks around pits. We designed the deposit excavation model using the Examine3D numerical modeling software, which is based on the boundary element method. We created three-dimensional models for three variants of working space opening widths: featuring two, three, and four rows of rooms. The geometry of rooms and pillars corresponded to the mine conditions; the width, height, and length parameters were all 5 m. We determined the strength, strain, and structural parameters of the rock mass on the basis of laboratory studies of the drill core and rock forms collected from the room longwall. We used the strength factor to specify the maximum range of the fault zone of rocks around pits. In the last stage of research, we compared the load value obtained based on numerical testing with the maximum load obtained in the tensile strength tests of the roof bolting and determined the safety factor of the segmentally-installed roof bolting.
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Li, Genwei, Shuaifeng Lu, Sifei Liu, Jing Liu, Peng Shi, and Bowen Fan. "Application and Effect of Loading Rates on Coal Sample Failure." Shock and Vibration 2021 (March 17, 2021): 1–12. http://dx.doi.org/10.1155/2021/6681082.
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In order to evaluate the coal pillar stability in recovery of residual room pillars under different mining rates, this paper studies the influence of loading rate on the mechanical properties of the coal body. The uniaxial compression tests of coal samples in Yangcheng area at different loading rates were carried out with the MTS815 electrohydraulic servo rock mechanics test system. The stress-strain curves and the evolution characteristics of AE signals were analyzed. At same time, the mechanism of damage and failure of specimens are also discussed. The results show the following. (1) With the increase in loading rate, the ultimate stress and ultimate strain of specimens decrease first and then increase. (2) Loading rate has a significant effect on the stability adjustment of specimens. With the decrease in loading rate, the earlier the stress adjustment is, the larger the adjustment range is, and the failure mode changes from shear failure to tensile failure. (3) In addition, when the loading rate increases, the AE evolves from continuous dense to discrete catastrophe, which indicates that the failure of the sample at a larger loading rate is sudden, which is not conducive to the maintenance of the stability of the coal pillar. (4) Finally, the failure mechanism of the specimen structure under different loading rates is obtained, and the improvement measures for the effect of mining velocity of working face on the stability of coal pillar are put forward. The results reveal the loading rate effect of mechanical properties of coal and provide a reference for controlling the stability of the residual coal pillar.
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Derraik, José G. B., Barbara I. P. Barratt, Phil Sirvid, Roderick P. Macfarlane, Brian H. Patrick, John Early, Alan C. Eyles, et al. "Invertebrate survey of a modified native shrubland, Brookdale Covenant, Rock and Pillar Range, Otago, New Zealand." New Zealand Journal of Zoology 28, no. 3 (January 2001): 273–90. http://dx.doi.org/10.1080/03014223.2001.9518270.
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Skrzypkowski, Krzysztof. "Case Studies of Rock Bolt Support Loads and Rock Mass Monitoring for the Room and Pillar Method in the Legnica-Głogów Copper District in Poland." Energies 13, no. 11 (June 10, 2020): 2998. http://dx.doi.org/10.3390/en13112998.
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The article presents the impact of geological and mining factors on the stability of room excavations in the Legnica-Głogów Copper District (LGOM) in Poland. In underground mining, the primary task of bolting of mining excavations is to ensure their stability as an essential condition of work safety. Appreciating the role and importance of the rock bolting in Polish ore mining; rock bolt load sensors were designed, manufactured and tested under laboratory conditions. The purpose of the research was to characterize the sensors and determine the elastic range of the bearing plate, which are an integral part of the sensor. The sensors have been verified in industrial conditions. The tests were carried out in the underground copper ore mine in Poland. Three rooms in the exploitation field were selected for testing, where exploitation was carried out at a depth of 809–820 m below the ground surface with the application of room and pillar with roof deflection and maintaining the central part of the field. The exploitation field included 60 rooms and pillars. The effectiveness of the mechanical load sensor of the expansion rock bolt support has been experimentally confirmed. Based on mine research, it was found that the largest increases in the load of the rock bolting, vertical stress and convergence occur in the middle of the mining field.
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Gao, Baobin, Chuangnan Ren, Qun Dong, and Liwei Chen. "Study on Dynamic Behavior Law and Microseismic Monitoring in Stoping Process of Roadway with High Gas and Wide Coal Pillar." Shock and Vibration 2021 (June 25, 2021): 1–14. http://dx.doi.org/10.1155/2021/5135964.
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In order to study the dynamic characteristics and microseismic distribution in the mining process of roadway with high gas and wide coal pillar, combined with the two dynamic events of N2105 working face in Yuwu Coal Industry, theoretical analysis and field measurement research were carried out. According to the theory of structural mechanics and geomechanics, the causes of dynamic appearance are analyzed. Combined with the specific situation, the influence of mining depth, coal pillar width, gas pressure, and content on the dynamic performance is analyzed. Stress monitoring and microseismic monitoring are carried out on one side of coal seam. The results show that, with the increase of the mining distance, the backside roof of the goaf is prone to unbalanced fracture due to the lack of lateral stress, and the impact pressure generated is used for the reserved protective coal pillar behind the goaf, causing the floor heave of coal seam. The combined stress generated by the anticlinal structure below the working face interacts with the abutment pressure of the working face to produce superposition effect, which promotes the occurrence of dynamic appearance. The critical depth of rock burst in Yuwu Coal Industry is about 600m. The increase of coal elastic energy caused by roof subsidence is more uniform with the increase of coal pillar width. The decrease of gas pressure in coal seam promotes the rock burst disaster. The vertical stress of coal seam at one side of the working face shows different evolution characteristics along the trend and strike. The vertical stress of coal seam in the lateral range of 53 m is adjusted to different degrees and tends to be stable until 300 m behind the working face. The active microseismic area in the middle of the working face was located 50 m in front of the working face, and the microseismic activity continued to 30–50 m behind the working face. The active microseismic area at the side of the roadway was located 30 m in front of the working face, and the microseismic activity continued to 100–180 m behind the working face. The inflection point, where the stress in the elastic area of coal pillar increases sharply, corresponds to the active microseismic area, which indicates that the dynamic characteristics in the mining process of roadway with high gas and wide coal pillar are related to the distribution law of microseismic. This study has a certain guiding significance for optimizing the width of reserved coal pillar, monitoring the coal seam stress/microseismic, and understanding the dynamic disaster of coal and rock under complex conditions.
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Grab, Stefan W., Katharine J. M. Dickinson, Alan F. Mark, and Tania Maegli. "Ploughing boulders on the Rock and Pillar Range, south‐central New Zealand: Their geomorphology and alpine plant associations." Journal of the Royal Society of New Zealand 38, no. 1 (March 2008): 51–70. http://dx.doi.org/10.1080/03014220809510546.
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Chen, Dongdong, En Wang, Shengrong Xie, Fulian He, Long Wang, Qing Zhang, Xiaoyu Wu, Zaisheng Jiang, Yubo Li, and Songhao Shi. "Roadway Surrounding Rock under Multi-Coal-Seam Mining: Deviatoric Stress Evolution and Control Technology." Advances in Civil Engineering 2020 (November 23, 2020): 1–18. http://dx.doi.org/10.1155/2020/9891825.
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Multi-coal-seam mining creates surrounding rock control difficulties, because the mining of a coal face in one seam can affect coal faces in another. We examine the effects of multi-coal-seam mining on the evolution of the deviatoric stress distribution and plastic zone in the roadway surrounding rock. In particular, we use numerical simulation, theoretical calculation, drilling detection, and mine pressure observation to study the distribution and evolution characteristics of deviatoric stress on Tailgate 8709 in No. 11 coal seam in Jinhuagong mine when the N8707 and N8709 coal faces in No. 7-4 coal seam and the N8707 and N8709 coal faces in No. 11 coal seam are mined. The evolution laws of deviatoric stress and the plastic zone of roadway surrounding rock in the advance and behind sections of the coal face are studied, and a corresponding control technology is proposed. The results show that the peak value of deviatoric stress increases with the advance of the coal face, and the positions of the peak value of deviatoric stress and the plastic zone become deeper. The deflection angle of the peak stress after mining at each coal face and the characteristics of the peak zone of deviatoric stress and the plastic zone of the roadway surrounding rock under the disturbance of multi-coal-seam mining are determined. In conclusion, the damage range in the roadway roof in the solid-coal side and coal pillar is large and must be controlled. A combined support technology based on high-strength and high pretension anchor cables and truss anchor cables is proposed; long anchor cables are used to strengthen the support of the roadway roof in the solid-coal side and coal pillar. The accuracy of the calculated plastic zone range and the reliability of the combined support technology are verified through drilling detection and mine pressure observation on site. This research can provide a point of reference for roadway surrounding rock control under similar conditions.
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Schmitt, Douglas R., Catherine Smither, and Thomas J. Ahrens. "In‐situ holographic elastic moduli measurements from boreholes." GEOPHYSICS 54, no. 4 (April 1989): 468–77. http://dx.doi.org/10.1190/1.1442673.
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We have developed a unique technique employing optical holography to measure the static Young’s modulus (E) from a borehole. In the experiment, a known point force induces micron scale displacements on the borehole wall which are recorded by a double‐exposure hologram. Raw data consist of dark fringes superimposed on the three‐dimensional image whose pattern is modeled to find E directly. In the laboratory, the holographic technique determined E on rock and metal samples to an uncertainty better than 10 percent. For example, double exposure holograms of a saw‐cut sample of dolomitic marlstone gave an E of 16.8 ± 2.8 GPa in agreement with 17.2 ± 2.0 GPa predicted by published density‐modulus relationships. Field tests of a holographic tool in a horizontal mine pillar borehole gave in‐situ Es which range from 26.9 to 36.0 GPa. Although these data could be interpreted as localized elastic heterogeneity within the rock mass, elastic anisotropy of the rock is a possible explanation for this variation.
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Mark, Alan F., Ulf Molau, Peter Whigham, Lorna Little, and Jacqueline Nielsen. "Periglacial tarn on the Rock and Pillar Range crest, south-central South Island, New Zealand, and its surrounding snowbank community." Austral Ecology 41, no. 3 (September 20, 2015): 282–90. http://dx.doi.org/10.1111/aec.12310.
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Sadovenko, I., V. Bondarenko, I. Salieiev, and A. Zagrytsenko. "Substantination of hydromechanical parameters of water regulation using mine pillars during mines closure." Collection of Research Papers of the National Mining University 64 (2021): 55–67. http://dx.doi.org/10.33271/crpnmu/64.055.
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Purpose. Substantiation of hydromechanical parameters that make it possible to control the safe ratio of hydrodynamic levels in a mine shaft and a rock mass when closing mines using submersible pumps. Research methodology. An experimental-analytical method was used, which consists in the formation and analysis of data from field tests of fractured porosity, permeability and the position of groundwater levels in hard sandstones around mine shafts with concrete support. Research results. It has been established that the hydromechanical state around a mine shaft in stable water-bearing rocks is characterized by the development of mutually competing processes of nonlinear decrease in the permeability of the loaded rock contour and hydrogeomechanical unloading of structural elements of water-bearing rocks and filter attachment. The values of the hydrogeomechanical unloading of the shaft attachment in the range of 0.054 - 6.125105 Pa are close to the tensile strength limit of the "concrete-water-bearing rock" contact, which indicates the danger of its collapse. Scientific novelty. The problem of combining the elastic viscometric load of the rock mass attachment and the hydrodynamic planar-radial flow to the wellbore is solved, where the hydrogeomechanical state in stable water-bearing rocks is characterized by the development of mutually competing processes of nonlinear decrease in the permeability of the loaded rock contour and hydrostatic unloading of structural elements of the water-bearing rocks and filters. Practical value. The obtained solutions and their analysis explain the discrepancy between the calculated (standard) loads on the fastening, which is known from practical experience, and actually measurable values, and also have significant practical significance. The established fact of the approximation of the value of hydrogeomechanical unloading of the stovol attachment to the tensile strength of the contact "concrete - water-bearing rock" is dubious and requires a decrease in the hydrodynamic deflection to the mine stovol when controlling the process of flooding with submersible pumps.
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Jia, Housheng, Luyao Wang, Kai Fan, Bo Peng, and Kun Pan. "Control Technology of Soft Rock Floor in Mining Roadway with Coal Pillar Protection: A case study." Energies 12, no. 15 (August 4, 2019): 3009. http://dx.doi.org/10.3390/en12153009.
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This study considered the mining roadway with coal pillar protection in the fully mechanized caving face of the Dananhu No.1 Coal Mine, China. Theoretical analysis, numerical simulation, and field tests were conducted, and the stress environment, deformation, and failure characteristics of the mining roadway in the fully mechanized caving face were analyzed. The results revealed that the intrinsic cause for the large asymmetrical floor deformation in the mining roadway is the asymmetrical phenomenon of the surrounding rock’s stress environment, caused by mining. This also results in the non-uniform distribution of the mining roadway floor’s plastic zone. The degree of asymmetrical floor heave is internally related to the thickness of the caving coal. When the thickness of the caving coal was in the range of 5.9 m, the deformation of the asymmetrical floor heave, caused by the plastic failure in the floor, became more obvious as certain parameters increased. As the rotation angle of the principal stress direction increased, the maximum plastic failure depth position of the floor gradually moved toward the middle of the roadway. This caused a different distribution for the maximum deformation position. The control of the floor heave deformation was poor, and it was not feasible to use high-strength support under the existing engineering conditions. Hence, the control should mainly be applied to the floor heave deformation. When the thickness of the caving coal was more than 5.9 m, the main roof strata was prone to instability and being cut along the edge of the coal pillar; the rock stress environment surrounding the roadway tended to revert back to the initial geostress state. The proposed floor heave control strategy achieved good results, and as the deformation of the floor heave decreased, the workload of the floor heave was also greatly reduced.
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Liu, Xudong, Wenlong Shen, Jianbiao Bai, Rui Wang, Jizhong Kang, and Xiangyu Wang. "Mining-Induced Redistribution of the Abnormal Stress under the Close Bearing Coal Pillar for Entry Design." Advances in Civil Engineering 2021 (April 8, 2021): 1–13. http://dx.doi.org/10.1155/2021/5595372.
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Underground space is vulnerable to large deformation influenced by the abnormal stress induced by the bearing coal pillar. A numerical simulation model was established to determine the redistribution of the abnormal stress induced by the mining activities. The double-yield model, the strain softening model, the interface model, and the Mohr–Coulomb model were determined to simulate the gob compaction effect, the pillar strength reduction effect, the structure plane discontinuity effect, and the rock mechanical behavior, respectively. This numerical simulation model is reliable to predict the abnormal stress under the bearing coal pillar by the comparison of the abutment stress from this model and the existing theoretical model as well as the entry roof surface displacement from this model and the field measuring method. The results from the validated numerical model indicate that the abnormal stress including stress concentration coefficient, stress gradient, and lateral pressure coefficient will redistribute to another state that the stress concentration coefficient and stress gradient increase gradually and then decrease, and the lateral pressure coefficient decreases gradually, then increases, and finally decreases sharply with the approach of the mining working face. Their maximum increasing rates are calculated as 121.05%, 198.56%, and 236.82%, respectively. This predicted mining-induced redistribution of the abnormal stress is available for designing the underground entry layout in the determination of the entry position, determination of the driving operation time, mining disturbing range warning, and the prediction of the strengthening support area.
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Cui, Feng, Chong Jia, Xingping Lai, Yanbing Yang, and Shuai Dong. "Study on the Law of Fracture Evolution under Repeated Mining of Close-Distance Coal Seams." Energies 13, no. 22 (November 19, 2020): 6064. http://dx.doi.org/10.3390/en13226064.
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The western region of China is rich in mineral resources. The vigorous development of mineral resources has exacerbated the environmental and safety problems in the region. One of the important links to solve this problem is to control the development laws and distribution characteristics of the overburdened cracks in the mining of this area. In this paper, the Xiashijie coal mine 3-2 coal seam and 4-2 coal seam are examples of repeated mining, and are examined as the background, through theoretical analysis to optimize the size of the coal pillars in the lower section, using the 3DEC numerical simulation experiment method and the rise of the cracks in the short-distance coal seam. Repeated mining monitoring and analysis of the development law are used to ascertain distribution characteristics of overburdened cracks caused by the repeated mining process of the working face. The results show that: (1) By establishing a mechanical model of the overlying strata structure under short-distance coal seam group mining, and carrying out the force analysis of the double section coal pillar under repeated mining, the reasonable size of a lower section coal pillar was determined to be 70 m. (2) As the development height of a fracture progresses with the working face, its expansion rate undergoes four obvious changes: fluctuations within a certain range, the expansion rate reaches the peak after the rock formation is concentrated and broken, the cyclical change gradually decreases, and the expansion rate is zero after complete mining. (3) The fracture zone height of 222 and 224 face under repeated mining in the 4-2 coal seam was 19.56–22.31 times and 22.38–24.54 times larger, respectively, and the post-mining fracture extension of the face with larger width and deeper burial under repeated mining was higher than that of the adjacent face. This study provides scientific guidance for the rational division of coal pillars and the solution of the problem of water conservation mining under repeated mining in the adjacent face of a short-distance coal seam.
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Li, Lifeng, Gan Li, Weili Gong, Jiong Wang, and Huilin Deng. "Energy Evolution Pattern and Roof Control Strategy in Non-Pillar Mining Method of Goaf-Side Entry Retaining by Roof Cutting—A Case Study." Sustainability 11, no. 24 (December 9, 2019): 7029. http://dx.doi.org/10.3390/su11247029.
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This article focuses on the energy density alteration during non-pillar mining method of goaf-side entry retaining by roof cutting (GERRC) and adjacent working face mining. We also studied the support control strategy of goaf-side roadway. Numerical calculation model is established, and the parameters of the model are verified by the measured advance abutment pressure and numerical solution. Based on the numerical model, the energy density during mining is studied. It is found that the whole energy evolution pattern of the goaf side entry during the two adjacent working face mining includes: the original rock energy, the advance energy of the current working face, the dynamic lateral abutment energy caused by strata movement, the lateral abutment energy of the adjacent working face. The support body failure and surrounding rock large deformation phenomenon often occur in goaf side roadway, which is influenced by multiple energy disturbances. Research shows that strong stress disturbance of surrounding rock generates in front of the working face 23 m and behind of working face 60 m in GERRC method. In the second goaf-side entry retaining, the range is in front of the working face 47 m. The evolution law of energy field puts forward the strategy of using the high constant resistance and large deformation (CRLD) anchor cable and procured preferable effect.
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Zhang, Buchu, Dequan Sun, and Ruiliang Zheng. "Evolution Law of Coal Seam Abutment Pressure under the Influence of Shallow Buried Complex Strata: A Case Study." Shock and Vibration 2021 (March 15, 2021): 1–13. http://dx.doi.org/10.1155/2021/6670175.
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The evolution law of lateral abutment pressure under the condition of fully mechanized mining in shallow coal seam is studied using the change process of coal pillar stress in disturbed section as the research object. The results of physical simulation experiment show that, after coal mining, due to the collapse of coal seam roof, the overlying strata of key layer will disturb the section coal pillar to different degrees, and the sudden change of degrees of abutment pressure near the coal wall reaches the maximum. Affected by the energy released by the fracture of key stratum, the stress mutation area shifts to the coal wall at a deeper level and the range of plastic zone increases. From the perspective of the numerical simulation, according to the change characteristics of coal pillar abutment pressure in the mining process, the dynamic load process of complex roof strata is divided into three stages: the stage not affected by mining, the stage of dynamic load action, and the stage of static load. In the first stage, the lateral abutment pressure is only affected by the roadway mining, causing stress concentration in the coal body. The stress concentration coefficient is small, and the supporting stress is stable. In the second stage, with the advance of the working face, the coal seam load changes continuously owing to the movement of overlying rock in the goaf, and the lateral abutment pressure changes evidently under the influence of dynamic load. In the third stage, the overlying load forms stress concentration in the coal seam and continuously transfers to the coal wall at a deeper level, which increases the limit equilibrium area of coal body. During this period, the range of plastic zone still increases at a certain rate for a period of time and finally tends to be stable.
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Jiang, Pengfei, Peng Xiao, Fanbao Meng, Suolin Jing, Jingkai Zhang, Ge Wang, and Peng Zhao. "Application Study on Active Advanced Support Technology in Deep Roadway under Mine Goaf." Geofluids 2020 (November 24, 2020): 1–13. http://dx.doi.org/10.1155/2020/8865238.
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To solve the problems of the rapid advance of the working face was delayed by complicated working procedure and high labor intensity, and the severe damage of roof bolt (anchor cable) induced by advanced hydraulic support, the deformation characteristics of surrounding rock, and the supporting principle of grouting truss anchor cable were analyzed theoretically by taking the roadway of 3_(down) coal seams 2326# working face in Sanhekou coal mine as the research object; then, the mechanical model of supporting structure of roadway under goaf was established. Based on this model, the optimal supporting scheme was determined, and the active advanced support technology scheme of “advanced grouting truss anchor cable” was proposed to take the place of the existing single pillar. The deformation and failure characteristics of surrounding rock of the working face leading roadway were observed and analyzed on-site. Within the allowable range of reading error, the results showed that the maximum displacement of medium-deep base point and shallow base point of two roadways was 15.2 cm and 10.9 cm, respectively; the pressure value had a more obvious jump increase when the distance between each measuring point and the working face was about 35 m, which means the range is strongly affected by the advance mining, and the area affected by advanced mining was 35 m ahead of the working face. It was observed that the lowest position of roof separation development ranged from 0.71 m to 2.73 m. The separation layer was generally distributed in the range of 0.73 m-2.49 m, and the fracture area was roughly distributed in the range of 0.01 m-0.62 m. Under the condition of overlying goaf, there was a complete stress structure, which can meet the requirements of suspension support.
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Geng, Jiabo, Qihang Li, Xiaoshuang Li, Tao Zhou, Zhifang Liu, and Yulin Xie. "Research on the Evolution Characteristics of Rock Mass Response from Open-Pit to Underground Mining." Advances in Materials Science and Engineering 2021 (August 9, 2021): 1–15. http://dx.doi.org/10.1155/2021/3200906.
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This study is based on the engineering background of pit no. 2 in Jinning Phosphate Mine, China. In order to systematically analyze the movement, deformation, and failure laws of surrounding rocks in underground stopes. The room and pillar method is used to excavate and stop the ore bodies in the mining area. Combined with the similar physical model experiments and discrete element MatDEM numerical simulations, it reveals the deformation and failure laws and evolution characteristics of the surrounding rock of the stope in the process of converting from open-pit to underground mining. The results show the following: (1) Along the inclination of the ore body, the farther the horizontal and vertical displacements are from the underground stope, the less the impact of mining stress. On the other hand, along the inclined vertical direction of the ore body, the farther the measuring point is from the stope, the smaller the range of mining influence will be. (2) In the process of ore body recovery, the rupture of the overlying strata of the stope has an obvious layered structure, with collapse zones, fissure penetrating zones, and microfracture loosen zones appearing from the bottom to top. In addition, the movement and destruction of the overlying strata of the entire stope is an “elliptical arch.” Therefore, the results of similar simulation experiments and numerical simulation are basically consistent.
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Guo, Xiaofei, Yongen Li, Guangdong Zhou, Zengji He, Haoran Yu, and Yichang Xu. "Stability Analysis and Reasonable Layout of Floor Drainage Roadway above Confined Water and under Mining Influence." Geofluids 2021 (March 12, 2021): 1–11. http://dx.doi.org/10.1155/2021/5578717.
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The surrounding rock failure range of floor drainage roadway under the mining influence and its effect on the aquiclude are the key to determine the aquiclude thickness of the floor. This paper studied the distribution characteristics of the surrounding rock plastic zone by the numerical simulation when the floor drainage roadway was located at different positions under the working face and determined the rational position. Results show that (1) when the floor drainage roadway is staggered inward, the floor surrounding rock is prone to appear the butterfly plastic zone under single work face mining. And the butterfly plastic zone increases sharply after being affected by secondary mining of adjacent working face. (2) When the floor drainage roadway is staggered outward, the floor surrounding rock plastic zone extends gently affected by a single working face. And the depth of the plastic zone has no obvious change after being affected by secondary mining of adjacent working face. (3) According to the risk of water inrush, the three layout schemes can be ranked as follows: stagger inward 25 m > stagger inward 80 m > stagger outward 15 m . (4) Considering the floor stress environment, gas extraction efficiency, and water prevention and control, the reasonable location of floor drainage roadway below the No. 11060 working face of Zhaogu No. 2 Coal Mine was finally determined. It was arranged in the sandy mudstone layer on the upper part of L9 limestone under the middle part of coal pillar and was drived along the seam floor.
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SOKOLOV, Igor, Yury ANTIPIN, and Artem ROZHKOV. "MODERNIZATION OF THE MINING SYSTEM OF SMALL DEPOSITS OF RICH COPPER PYRITE ORES." Sustainable Development of Mountain Territories 12, no. 3 (September 30, 2020): 444–53. http://dx.doi.org/10.21177/1998-4502-2020-12-3-444-453.
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The purpose work. Substantiation and selection of a safe and effective option of mining technology of the experimental block in the pilot industrial mining of the Skalistoe deposit. Method of research. Analysis and synthesis of project solutions, experience in mining inclined low-thickness ore bodies, economic and mathematical modeling and optimization of the parameters of options mining systems in the conditions of the experimental block. Results of research. As a result of research it was established: - the sublevel caving mining system with the parameters adopted in the project does not guarantee the completeness of the extraction of reserves and the effectiveness of mining operations. Project indicators of extraction by sublevel caving technology with frontal ore drawing are overestimated and difficult to achieve in these geological and technical conditions (combination of low thickness and angle of ore body); project scheme for the delivery and transportation of rock mass seems impractical due to the significant volume of heading workings and increased transportation costs; - eight technically rational options of various mining systems were constructed, most relevant to the geological and technical conditions of the deposit. Five variants of the sublevel chamber system and pillar caving, a project variant of sublevel caving technology with frontal ore drawing and two options flat-back cut-and-fill system were considered; - for mining the Skalistoe deposit, according to the results of economic and mathematical modeling, optimal by the criterion of profit per 1 ton of balance reserves of ore is a option of the technology of chamber extraction with dual chambers, frontal drawing of ore by remote-controlled load-haul-dump machine and subsequent pillars caving, as having the greatest profit; - the calculations justified stable spans of dual chambers (25.3 m) and the width of panel pillars (3 m). With an allowable span of 25.3 m, the roof of the dual chambers will be stable with a safety factor of 1.41, and a panel pillar with a width of 3 m has a sufficient margin of safety (more than 1.6) in the whole range of ore body thickness variation; - the proposed scheme of delivery and transportation of rock mass, which allows to reduce the volume of tunnel works by 26% and the average length of transportation by 10-15% compared with the project. Findings. Developed in the process of modernization the technology sublevel chamber system with double-chamber, compared with the project technology, it is possible to significantly increase the efficiency of mining of the low thickness deposit of rich ores Skalistoe by reducing the specific volume of preparatory-rifled work by 34%, the cost of mined ore by 12%, losses and ore dilution – by 2 and 2.9 times, respectively.
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d’Obyrn, Kajetan, and Joanna Hydzik-Wiśniewska. "Assessment of Rock Mass Stability in the Historic Area of Levels IV-V of the “Wieliczka” Salt Mine." Archives of Mining Sciences 62, no. 1 (March 1, 2017): 189–202. http://dx.doi.org/10.1515/amsc-2017-0014.
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Abstract As a result, of more than 700 years of exploitation in the Wieliczka Salt Mine, a network of underground workings spreading over eleven levels was created. All mine workings of significant historic and natural qualities and the majority of functional mine workings designated to be preserved are located on levels I to V. The most precious of them, available to tourists, are located in the central part of the Mine on levels I-III. The Mine is not anticipating to make levels IV, Kołobrzeg and V available for a wider range of visitors, even though there are historically and naturally precious workings in those areas as well. The most valuable of the mine workings come from the eighteenth and nineteenth centuries and were exploited mainly in a bed of fore-shaft salt, Spiza salt and the oldest ones. The characteristic feature of these excavations, distinguish them from the chambers located on the levels I-III, is the room-and-pillar system that had been used there. Mine workings exploited in this system measure up to 100 metres in length, and the unsupported pillars standing between the chambers measuring 4-10 metres in width were remained. The described above levels, including levels of VI-IX are to provide a stable support for the workings located higher up. The remaining part of the mine, with the exception of the function workings, is designated for liquidation by backfilling. The article presents an assessment of stability of the mine workings, located on levels IV-V, and their impact on the surrounding rock mass and the land surface. The analysis was based on geodetic measurements and numerical calculations for strain state of rock mass surrounding the mine workings, in actual conditions and after partial backfilling, and forecast of the rock stability factor after the end of backfilling. The assessment stability factor in the vicinity of excavations at levels IV-V was based on the results of spatial numerical analysis covering the entire central area of the mine from the surface to level V. Numerical calculations were performed using FLAC programme based on the finite difference method, allowing to observe the mechanisms and processes of destruction and deformation. The calculations were performed for the elastic-plastic medium with the Mohr-Coulomb failure criterium. The choice of this computational model was dictated by a very diverse geological structure of the Wieliczka rock mass and a complex system of excavations.
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King, T. M., G. P. Wallis, S. A. Hamilton, and J. R. Fraser. "Identification of a hybrid zone between distinctive colour variants of the alpine weta Hemideina maori (Orthoptera: Stenopelmatidae) on the Rock and Pillar range, southern New Zealand." Molecular Ecology 5, no. 4 (August 1996): 583–87. http://dx.doi.org/10.1046/j.1365-294x.1996.00118.x.
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KING, T. M., G. P. WALLIS, S. A. HAMILTON, and J. R. FRASER. "Identification of a hybrid zone between distinctive colour variants of the alpine weta Hemideina maori (Orthoptera: Stenopelmatidae) on the Rock and Pillar range, southern New Zealand." Molecular Ecology 5, no. 4 (August 1996): 583–87. http://dx.doi.org/10.1111/j.1365-294x.1996.tb00350.x.
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CHAPPLE, DAVID G., TRENT P. BELL, STEPHANIE N. J. CHAPPLE, KIMBERLY A. MILLER, CHARLES H. DAUGHERTY, and GEOFF B. PATTERSON. "Phylogeography and taxonomic revision of the New Zealand cryptic skink (Oligosoma inconspicuum; Reptilia: Scincidae) species complex." Zootaxa 2782, no. 1 (March 3, 2011): 1. http://dx.doi.org/10.11646/zootaxa.2782.1.1.
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The New Zealand skink fauna is highly diverse and contains numerous cryptic, undescribed or hitherto undiscovered species. We completed a taxonomic revision of the cryptic skink (Oligosoma inconspicuum) species complex using molecular (550 bp of the ND2 mitochondrial gene) and morphological analyses. Four new species are described, with each diagnosable by a range of morphological characters and genetic differentiation from several closely related species: O. inconspicuum (sensu stricto), O. notosaurus, O. maccanni, O. stenotis and O. grande. Oligosoma tekakahu sp. nov. is restricted to Chalky Island in Fiordland, and is most closely related to O. inconspicuum and O. notosaurus. The other three new species are restricted to particular mountainous regions in central and western Otago (O. burganae sp. nov., Lammermoor and Rock and Pillar Ranges; O. toka sp. nov., Nevis Valley; O. repens sp. nov., Eyre Mountains) and are most closely related to O. stenotis and O. grande. We also re-described O. inconspicuum. Two proposed new taxa, the ‘Big Bay’ skink and ‘Mahogany’ skink, were found to represent Westland/Fiordland populations of O. inconspicuum rather than distinct taxa. We discuss the evolutionary and phylogeographic implications of cryptic and ‘anti-cryptic’ species within the O. inconspicuum species complex, and suggest that morphologically aberrant populations are the result of local adaptation to novel selective regimes.
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Wang, Yajun, Haosen Wang, Manchao He, Qi Wang, Yafei Qiao, and Jun Yang. "Mine Pressure Behavior Characteristics and Control Methods of a Reused Entry that Was Formed by Roof Cutting: A Case Study." Shock and Vibration 2020 (February 27, 2020): 1–15. http://dx.doi.org/10.1155/2020/4276730.
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Noncoal pillar mining with automatic formation of a roadway is a new coal mining method that is tailored to improve the coal resource recovery rate and reduce the investment in roadway tunneling. Using this proposed method, a reuse entry is formed by roof cutting instead of tunneling. In this paper, the S1201-II working face of the Ningtiaota Coal Mine was used as a case study. The stress distribution of surrounding rock and the roof deformation characteristics of the reused entry during the mining process of the second working face were studied through FLAC3D numerical simulations combined with field measurements. The results indicate that the zone close to the reused entry led to higher stress in advance. If this stress is superimposed with the lateral pressure of the adjacent mined working face, it will be more difficult to maintain the reused entry. In the engineering case study described here, the reused entry created a stress increase zone and a severe deformation zone in the range of 0–80 m in front of the working face, and its range was approximately 37.5% larger than an ordinary entry. The stress peak in the stress increase zone increased by approximately 34.7% over that of an ordinary entry. The maximum amount of deformation within the severe deformation zone increased by 94.4% over that of an ordinary entry. To properly control the surrounding rock stress and deformation of the reused entry, a dynamic pressure bearing support in front of the working face with adaptability to the large roof deformation and high support strength is proposed here. Field application results showed that the final roof deformation with the dynamic pressure bearing support can be satisfactorily controlled within 110∼130 mm. These findings can provide a reference for researchers and field engineering technicians when engaging in the support work of reused entry.
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Pearson, D. J., and J. E. Kinnear. "A Review of The Distribution, Status and Conservation of Rock-wallabies in Western Australia." Australian Mammalogy 19, no. 2 (1996): 137. http://dx.doi.org/10.1071/am97137.
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Western Australia has five species of rock-wallabies. Petrogale brachyotis, Petrogale burbidgei and Petrogale concinna occur in wet-dry tropical habitats in the Kimberley region. Petrogale rothschildi is a Pilbara region endemic, while Petrogale lateralis has the largest distribution, extending from the south-west Kimberley to islands off the southern coastline. There have been few collections of the three species restricted to the Kimberley. Their small size, secretive disposition and variable pelage have hampered field identification, and thus, understanding of their distribution and status. The populations of all three are currently believed to be stable and their status is considered secure. Petrogale rothschildi is known from the Hamersley and Chichester Ranges, the east Pilbara, the Burrup Peninsula and four islands in the Dampier Archipelago. It is abundant on three of these islands but has declined on Dolphin island. The status of the mainland populations is uncertain. Petrogale lateralis is a diverse species, with two subspecies and two chromosomal races occurring in WA. Petrogale lateralis hacketti is restricted to three islands in the Archipelago of the Recherche. Petrogale lateralis lateralis has declined throughout its mainland range, with extant populations known from six localities in the Wheatbelt; Cape Range; the Calvert Range; and Barrow and Salisbury Islands. It may still be extant in Kalbarri National Park. Petrogale lateralis West Kimberley race has a restricted distribution but appears secure, while P. lateralis MacDonnell Ranges race has declined markedly in recent years. Fox predation has been implicated in the decline of some populations of P. lateralis and P. rothschildi. The impact of factors such as competition from introduced grazers (stock, rabbits, goats), fire and habitat clearing have not been examined. Increased control of exotic predators, taxonomic research to clarify the identity of unsampled populations and field surveys are needed to improve the conservation outlook for WA rock-wallabies.
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Wang, Hong-Sheng, Hai-Qing Shuang, Lei Li, and Shuang-Shuang Xiao. "The Stability Factors’ Sensitivity Analysis of Key Rock B and Its Engineering Application of Gob-Side Entry Driving in Fully-Mechanized Caving Faces." Advances in Civil Engineering 2021 (May 24, 2021): 1–11. http://dx.doi.org/10.1155/2021/9963450.
Full textAbstract:
To reveal the critical factors of the main roof influencing stability of surrounding rocks of roadways driven along goaf in fully-mechanized top-coal caving faces, this paper builds a structural mechanics model for the surrounding rocks based on geological conditions of the 8105 fully-mechanized caving face of Yanjiahe Coal Mine, and the stress and equilibrium conditions of the key rock block B are analyzed, and focus is on analyzing rules of the key rock block B influencing stability of roadways driven along goaf. Then, the orthogonal experiment and the range method are used to confirm the sensitivity influencing factors in numerical simulation, which are the basic main roof height and the fracture location, the length of the key rock block B, and the main roof hardness in turn. It is revealed that the basic main roof height and its fracture location have a greater influence on stability of god-side entry driving. On the one hand, the coal wall and the roof of roadways driven along goaf are damaged, and the deformation of surrounding rocks of roadways and the vertical stress of narrow coal pillars tend to stabilize along with the increase of the basic main roof height. On the other hand, when the gob-side entry is located below the fracture line of the main roof, the damage caused by gob-side entry is the most serious. Therefore, on-site gob-side entry driving should avoid being below the fracture line of the main roof. At last, industrial tests are successfully conducted in the fully-mechanized top-coal caving faces, 8105 and 8215, of Yanjiahe Coal Mine.
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D’Obyrn, Kajetan, and Antoni Tajduś. "Geomechanical Numerical Analysis as a Guidance for Preservation Works of the “Wieliczka” Salt Mine Site." Studia Geotechnica et Mechanica 39, no. 2 (June 27, 2017): 25–34. http://dx.doi.org/10.1515/sgem-2017-0013.
Full textAbstract:
Abstract Salt was excavated at the “Wieliczka” Salt Mine for over 700 years. Underground mining operations terminated in 1996, by which time almost 2,400 chambers and 245 km of galleries had been created underground, situated on 9 levels and a few interlevels. In 1978, the mine was included in the UNESCO World Heritage List, which stated that parts of the mine with historical value had to be preserved for future generations. In order to preserve the most valuable chambers and galleries, activities aimed at establishing a protection pillar for excavations were conducted in the conservation area on Levels I-V. The need of large scope preserving works created the necessity to conduct a new and truly comprehensive geomechanical analysis. Such an analysis could only be done by means of advanced numerical modelling codes. Three-dimensional calculations were performed by means of FLAC 3D finite difference code. Rock mass stability assessment in the vicinity of excavations was carried out on the basis of the distribution and range of the so called failure zones. This comprehensive geomechanical analysis allows for verification and give the directions for future preservation and closure works in the “Wieliczka” mine.
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Barratt, B. I. P., and G. Kuschel. "Broad‐nosed weevils (Curculionidae: Brachycerinae: Entimini) of the Lammermoor and Rock and Pillar Ranges in Otago, with descriptions of four new species ofIrenimus." New Zealand Journal of Zoology 23, no. 4 (January 1996): 359–74. http://dx.doi.org/10.1080/03014223.1996.9518096.
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Deng, D. Q., N. Jiang, and Y. Duan. "Sampling and Mechanical Testing of Backfill in Large Mined-Out Area." Geofluids 2021 (January 29, 2021): 1–8. http://dx.doi.org/10.1155/2021/6686385.
Full textAbstract:
To investigate the physicomechanical properties of stope backfill and to explore the mining conditions for an adjacent pillar, four boreholes, namely, GZK1, GZK2, GZK3, and GZK4, were constructed for taking the backfill core in the test stope. During borehole sampling, it is found that the strength of backfill is usually lower than that of the rock and ordinary concrete, and its resistance to tensile and compressive loads is limited. Therefore, the drilling speed should not be too fast, and a small amount of water is needed to continue drilling smoothly. For backfill with high strength, the sampling process is relatively smooth, and the backfill samples are relatively complete. GZK1 is located on the upper part of the stope near the footwall of the orebody, and the test results show that the backfill quality of this part is poor; thus, a complete backfill core cannot be obtained. GZK2 is located at the bottom of the stope close to the footwall of the orebody, GZK3 is located at the bottom of the stope close to the hanging wall of the orebody, and GZK4 is located at the top of the stope close to the hanging wall of the orebody. The average compressive strength and average tensile strength of the backfill samples obtained from the three boreholes, namely, GZK2, GZK3, and GZK4, are 2.928 to 3.583 MPa and 0.328 to 0.523 MPa, respectively, indicating that the backfill near the upper part and bottom close to the hanging wall of the orebody is good, while the backfill near the upper part close to the footwall of the orebody is poor. Special attention should be paid to the backfill with the range of GZK1 in the future second-step pillar mining process, and the sublevel method can be adopted to ensure the safety of the mining process. The backfill samples in the large goaf of No.17 room were obtained by geological drilling. Segregation occurred in the upper part of the No.17 room near the area of the footwall. The concentration and flow rate of the filling slurry were reasonably adjusted and controlled with the improvement of backfill quality. Therefore, the backfill strength of the No.17 room is generally good, which can meet the requirements of pillar mining, and also creates a good condition for the resource utilization of waste tailings of Caolou Iron Mine.
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Duan, Hongfei, and Lijuan Zhao. "Prevention Technology for Strong Mine Pressure Disaster in the Hard-Roof Large-Mining-Height Working Face." Shock and Vibration 2020 (October 21, 2020): 1–15. http://dx.doi.org/10.1155/2020/8846624.
Full textAbstract:
The movement and destruction of the hard roof in a stope is an important reason for the occurrence of strong ground pressure disasters at the working face. Considering Tongxin Coal Mine as the engineering background, the stress distribution law of the surrounding rock and the overburden rock damage characteristics of a large-mining-height working face under the hard roof were investigated. To solve the problem whereby the stope’s hard roof is difficult to collapse, the hard rock key stratum of the roof was hydraulically fractured to weaken the mechanical properties of the roof rock stratum. Additionally, microseismic monitoring technology was used to monitor the cracking effect of the rock stratum. The theoretical calculation and numerical simulation results reveal that, after hydraulic fracturing, a crack with a more consistent trend formed inside the hard rock stratum and a large area of the rock stratum was damaged. According to the monitoring results of the stope stress after hydraulic fracturing, the law governing the occurrence of the leading bearing pressure was in effect. In contrast, the influence range and peak strength of the leading bearing pressure were considerably reduced at the working face after hydraulic fracturing. After performing hydraulic fracturing on the roof of the working face, the bearing pressure of the working face can satisfy the production requirements better. Finally, the results obtained through this study can be used as a reference for determining the width of coal pillars under similar mining conditions.
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Li, Yizhe, Shankun Zhao, Qingxin Qi, Pengzhi Pan, Xiangzhi Wei, Yin Wang, Ningbo Zhang, Yang Zhao, Haitao Chai, and Qilin Hao. "Mechanism of Coal Bump among Mine Group under the Control of Large Geological Body: A Case Study of Yima Mining Area, China." Advances in Civil Engineering 2021 (July 7, 2021): 1–12. http://dx.doi.org/10.1155/2021/8890651.
Full textAbstract:
Coal bump often occurs in coal mining among many working faces in mine group under the control of large geological bodies. In order to study the coal bump mechanism between adjacent working faces under the conditions of large fault and huge thick overburden conglomerate, this paper regards Yima mining area as a practical engineering background and theoretically analyzes the mechanical behavior of overlying rock in the spatial structure. Then, the deep-ground and whole-space measurement is carried out in the 13230 working face of Gengcun mine and 21121 working face of Qianqiu mine. The results show that the basic structural unit in Yima mining area is composed of two goafs, middle coal pillar, and overlying conglomerate. Under the condition of nonsynchronous mining in adjacent working faces, there is a comovement effect similar to lever’s “prying” phenomenon in thick conglomerate beam—the conglomerate strata above larger goaf side induce an overall uplift movement of the corresponding strata above smaller goaf side, and uplift length of the conglomerate strata is related to the mining length, coal pillar width, caving angle, and coal-conglomerate distance. The results of surface subsidence, microseism, and stress in the two working faces verify the conglomerate’s phenomenon of comovement effect and disturbance range and further explain the role of active movement of F16 fault and overall causes of huge thick conglomerate on the coal bump. The vertical stress of the 13230 face is relatively low at the beginning, and high horizontal stress by fault activation causes typical bump accident with the horizontal sliding of coal body. With the increasing development of 13230 face, the intensity and frequency of coal bump in horizontal direction decrease obviously, but with high proportion in vertical direction. The results provide a theoretical basis for the study on the mechanism of coal bump between two adjacent working faces under the conditions of huge thick conglomerate and large thrust fault.
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Yang, Yongkang, Yanrong Ma, Chunxu Ji, Tianhe Kang, and Xingyun Guo. "Effect of Mining Thickness on Overburden Movement and Underground Pressure Characteristics for Extrathick Coal Seam by Sublevel Caving with High Bottom Cutting Height." Advances in Civil Engineering 2018 (November 25, 2018): 1–15. http://dx.doi.org/10.1155/2018/6871820.
Full textAbstract:
Because the coal seam is particularly thick and the mining intensity is large, the mining of extremely thick coal seams often causes a wide range of disturbed fractures, which in turn induces the phenomenon of strong underground pressure such as induced support crushing and water inrush. Through theoretical analysis, laboratory similarity simulation test, and other methods, this paper studies the effect of mining thickness on overburden movement and underground pressure characteristics for extremely thick coal seams by sublevel caving with high bottom cutting height. Some conclusions can be drawn as follows: (i) under the “beam-hinged cantilever beam rocks” structure theory, the rock pillar thickness which needs to be controlled increases linearly as a function of mining thickness is achieved, and the reason of increased of support resistance in full-mechanized caving mining in extremely thick seams is explained in the theory; (ii) based on the results of the theoretical analysis and the lab simulation tests, the law of the abutment pressure peak is inverse to the full-seam mining thickness, and the distance between abutment peak and working face is proportional to the full-seam mining thickness, that is to say that the damage range of overlying strata increased; (iii) there are three working states of loading support in extrathick coal seams, such as normal circumstance, lower main roof pressure, and higher main roof pressure, meanwhile these states keep changing; (iv) under the guarantee of stope safety conditions, due to lower support strength, it will benefit the special thick seam top-coal caving under normal circumstance; (v) increasing the supporting strength can balance the impact loading under the lower main roof pressure, guaranteeing valid support for roof strata; (vi) by releasing high pressure, due to lower production, lower recovery rate of coal and other measures guarantee the stability of the stope support in the case of the higher main roof pressure.
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Zhu, Daoyong, Weili Gong, Yi Su, and Aipeng Guo. "Application of High-Strength Lightweight Concrete in Gob-Side Entry Retaining in Inclined Coal Seam." Advances in Materials Science and Engineering 2020 (January 22, 2020): 1–20. http://dx.doi.org/10.1155/2020/8167038.
Full textAbstract:
Gob-side entry retaining (GSER) is a popular no-pillar mining technology that can increase coal recovery rate. We propose the application of high-strength lightweight (HSLW) concrete to construct the gob-side support body (GSSB) in NO. 411 inclined working face of Jingang Coal Mine. Firstly, the mechanical model of retained roadway was established, and the calculation for limit angle of GSSB stability and support resistance was mathematically derived. Using the performance test, the optimal proportion of LC50 concrete was determined as follows: the water-binder ratio was 0.3; the silica fume dosage was not more than 10%; the fly ash dosage was 10–20%; and the sand ratio was 0.45–0.50. Based on theoretical deduction and laboratory analysis, the width of GSSB was obtained to be 0.75 m, and the optimal arrangement of concrete blocks with “two longitudinal and one horizontal, crisscross, and staggered joints” was determined. FLAC3D software was used to study the influence of different widths and material strengths on the surrounding rock deformation and verify the reasonable width and strength of the designed GSSB. Finally, field monitoring of retained roadway shows that the deformation is controlled in a small range, and the retained roadway effect is better, thus proving the feasibility of HSLW for constructing the support body for GSER. Our findings can serve as a theoretical guide for safety and effective implementation of HSLW as GSSB.
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Yu, Bin, Yang Tai, Rui Gao, QiangLing Yao, Zhao Li, and Hongchun Xia. "The sustainable development of coal mines by new cutting roof technology." Royal Society Open Science 7, no. 6 (June 2020): 191913. http://dx.doi.org/10.1098/rsos.191913.
Full textAbstract:
China consumes more than 3.6 billion tons of coal every year. In the meanwhile, coal accounts for over 60% of the energy consumption sector. Therefore, the sustainable development of coal mines is a problem that needed to be solved by the Chinese government. During the coal resources recovery process, the protective coal pillars between the adjacent working faces lead to a vast waste of coal resources. In order to mitigate the resource-wasting issue, a new technology of roof cutting with chain arm retaining roadway was put forward in this paper. First, the procedures of retaining roadway, roof-cutting parameters and the damage ranges of roadway surrounding rock induced by roof cutting with chain arm were analysed. Then, the working resistance of the temporary support equipment is given when using the new technology to retain the roadway. Next, the roof-cutting height, the temporary support equipment selection, working resistance of portal support and support parameters of the bolt and anchor cables were optimized based on the numerical calculation. The industrial experiment of retaining roadway by roof cutting with chain arm was carried out in a working face. The surrounding rock damage was lowered and controlled with the application of chain arm roof-cutting technology. Also, it was found that the variation range of the uniaxial compressive strength was only 5%, resulting in the roof damage range of 82 mm. The new technology has proved a potentially wide application in the coal mining industry with prosperous economic and safety improvement.