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1
Le Vine, D. M., L. Gesell i Michael Kao. "Radiation from lightning return strokes over a finitely conducting Earth". Journal of Geophysical Research 91, nr D11 (1986): 11897. http://dx.doi.org/10.1029/jd091id11p11897.
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Cooray, Vernon, Marcos Rubinstein i Farhad Rachidi. "A Self-Consistent Return Stroke Model That Includes the Effect of the Ground Conductivity at the Strike Point". Atmosphere 13, nr 4 (6.04.2022): 593. http://dx.doi.org/10.3390/atmos13040593.
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A current generation type return stroke model which can take into account the possible modifications of the return stroke properties by the soil conductivity at the strike point of the lightning flash is introduced. The model is also capable of incorporating the reflection of the current at the ground end of the return stroke channel. In this paper, this return stroke model is used to investigate (a) the effect of the ground conductivity at the strike point on the source electromagnetic fields generated by return strokes and (b) the effect of current reflection at ground level on the electromagnetic field generated by return strokes. The source electromagnetic fields are the electromagnetic fields generated by lightning flashes calculated in such a way that they are not distorted by propagation effects. The results obtained show that the ground conductivity at the strike point does not significantly influence the return stroke current peak or the radiation field peak for ground conductivities higher than about 0.001 S/m. However, strike points with very poor conductivities (lower than 0.001 S/m) would result in a decrease of the peak electric field. In contrast to the peak values of the lightning current and the electric field, the peak values of the time derivatives of the lightning current and electric field are significantly reduced when the strike point of the lightning flash is located over a finitely conducting ground. The inclusion of the current reflection at ground level influences significantly the saturation of the close electric fields. The current reflection also gives rise to residual electric fields, a difference in the field levels generated by the dart leader and the return stroke. The residual field decreases as the fraction of the reflected current decreases.
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Jun, Sang Hyun, i Hyuk Jae Kwon. "Constitutive Relationship Proposition of Marine Soft Soil in Korea Using Finite Strain Consolidation Theory". Journal of Marine Science and Engineering 8, nr 6 (11.06.2020): 429. http://dx.doi.org/10.3390/jmse8060429.
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This paper proposes representative constitutive relationship equations of dredging and reclamation soft soil in Korea. The marine soft soils were sampled at 23 dredged-reclaimed construction sites in the Busan, Gwangyang, and Incheon regions in Korea; then, laboratory tests were carried out. The consolidation property was classified as LL = 60% for Busan and Gwangyang marine soft soil and LL = 30% for Incheon marine soft soil by conducting basic physical property tests and consolidation tests. Busan soft soil showed a slightly higher consolidation settlement property than Gwangyang soft soil. Incheon soft soil showed the lowest consolidation settlement property among the three regions. In particular, 77 consolidation simulations were carried out at a high void ratio using the centrifugal experiment to realize high water content and in-field stress conditions. The constitutive relationship equations of each of the 23 specimens were analyzed with regard to the void ratio–effective stress and void ratio–permeability coefficient through the back analysis of finite consolidation theory from the experimental results. The constitutive relationship equation for Korean soft soil was determined to be a reasonable power function equation. The representative constitutive relationships for soft soils in the three regions were estimated using six equations, which were classified by physical and consolidation properties. The representative constitutive equations were compared to those in previous studies on high void ratio conditions of marine soft soil, and the results showed a similar range.
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Rasouli, Habib, Hana Takhtfirouzeh, Abbasali Taghavi Ghalesari i Roya Hemati. "Bearing Capacity Improvement of Shallow Foundations Using Cement-Stabilized Sand". Key Engineering Materials 723 (grudzień 2016): 795–800. http://dx.doi.org/10.4028/www.scientific.net/kem.723.795.
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In order to attain a satisfactory level of safety and stability in the construction of structures on weak soil, one of the best solutions can be soil improvement. The addition of a certain percentage of some materials to the soil may compensate for its deficiency. Cement is a suitable material to be used for stabilization and modification of a wide variety of soils. By using this material, the engineering properties of soil can be improved. In this study, the effect of soil stabilization with cement on the bearing capacity of a shallow foundation was studied by employing finite element method. The material properties were obtained by conducting experimental tests on cement-stabilized sand. Cement varying from 2% to 8% by soil dry weight was added for stabilization. The effect of reinforced soil block dimensions, foundation width and cement content were investigated. From the results, it can be figured out that by stabilizing the soil below the foundation to certain dimensions with the necessary cement content, the bearing capacity of the foundation will increase to an acceptable level.
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Pang, Ying Bo. "Seismic Response Analysis of Soil-Structure Interaction on Base Isolation Structure". Advanced Materials Research 663 (luty 2013): 87–91. http://dx.doi.org/10.4028/www.scientific.net/amr.663.87.
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As an effective way of passive damping, isolation technology has been widely used in all types of building structures. Currently, for its theoretical analysis, it usually follows the rigid foundation assumption and ignores soil-structure interaction, which results in calculation results distortion in conducting seismic response analysis. In this paper, three-dimensional finite element method is used to establish finite element analysis model of large chassis single-tower base isolation structure which considers and do not consider soil-structure interaction. The calculation results show that: after considering soil-structure interaction, the dynamic characteristics of the isolation structure, and seismic response are subject to varying degrees of impact.
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Zhang, Hui, i Jing Zhang. "The Application of Finite Element Method in Calculating Two-Dimensional Heat Conduction in the Ground". Advanced Materials Research 988 (lipiec 2014): 479–82. http://dx.doi.org/10.4028/www.scientific.net/amr.988.479.
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This thesis simulated the principle of the fast heat conductivity testing instrument, introduced how to use the finite element method to calculate two-dimensional unstable heat conduction condition. When establish the mathematical model, the article simplifies the soil temperature field as the two-dimensional non-stable heat conduction problem. Through computation it can get the soil temperature field at any moment in the running time and the plan uniform temperature lines, that also may obtain the change of temperature about one point in the process. The method is simple and credible. These solutions of these questions are the foundation of research the heat conduction in the ground and the temperature field.
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Dumais, Simon, i Jean-Marie Konrad. "One-dimensional large-strain thaw consolidation using nonlinear effective stress – void ratio – hydraulic conductivity relationships". Canadian Geotechnical Journal 55, nr 3 (marzec 2018): 414–26. http://dx.doi.org/10.1139/cgj-2017-0221.
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A one-dimensional model for the consolidation of thawing soils is formulated in terms of large-strain consolidation and heat-transfer equations. The model integrates heat transfer due to conduction, phase change, and advection. The hydromechanical behaviour is modelled by large-strain consolidation theory. The equations are coupled in a moving boundary scheme developed in Lagrangian coordinates. Finite strains are allowed and nonlinear effective stress – void ratio – hydraulic conductivity relationships are proposed to characterize the thawing soil properties. Initial conditions and boundary conditions are presented with special consideration for the moving boundary condition at the thaw front developed in terms of large-strain consolidation. The proposed model is applied and compared with small-strain thaw consolidation theory in a theoretical working example of a thawing fine-grained soil sample. The modelling results are presented in terms of temperature, thaw penetration, settlements, void ratio, and excess pore-water pressures.
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MANZARI, MAJID T., i KARMA YONTEN. "ON IMPLEMENTATION AND PERFORMANCE OF AN ANISOTROPIC CONSTITUTIVE MODEL FOR CLAYS". International Journal of Computational Methods 11, nr 02 (marzec 2014): 1342009. http://dx.doi.org/10.1142/s0219876213420097.
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Numerical implementation of an anisotropic constitutive model for clays (SANICLAY) is presented. Moreover, a case study in which a soil embankment is placed on a K0-consolidated over-consolidated clay is analyzed by conducting an elastoplastic fully-coupled finite element analysis. It is shown that anisotropy has significant impact on the ground settlement caused by the placement of soil embankment and on the pore pressure generation and dissipation within the foundation soil. The simulations using SANICLAY favorably compare with the field measurements of ground settlement and pore pressure. The drawbacks of the use of an isotropic elastoplastic model (Cam Clay) are also demonstrated.
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Lv, Qing Feng, Peng Fei Liu i Yan Xu Zhao. "Finite Element Analysis of Rainfall Infiltration in a Compacted Loess Embankment". Advanced Materials Research 936 (czerwiec 2014): 1511–17. http://dx.doi.org/10.4028/www.scientific.net/amr.936.1511.
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Because of evapo-transpiration, compacted loess road embankments were considered to be in a partially saturated state in both arid and semi-arid regions. Based on previous studies and the theory of unsaturated soil mechanics, a numerical analysis of rainfall infiltration in a compacted loess road embankment was conducted. The transient seepage characteristics and moisture migration patterns of the moisture in the embankment were analysed. The results showed that after precipitation, the moisture profile of the compacted loess could be separated into three zones .The data also showed that: under the effect of gravity, the water continued to migrate into the embankment after the rainfall had ended. In time, the saturated zone became partially saturated as the moisture content decreased, whereas the moisture content in the conducting and humid zones increased and the wetting front moved downward. The data also showed that the depth of the conducting and humid zones increased in time, but that the moisture content in the conducting zone increased along a linear gradient with depth, while the moisture content in the humid zone decreased in a similar manner.
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Rysbaiuly, B., i S. D. Alpar. "Nonlinear inverse problem of finding thermophysical characteristics". Bulletin of the National Engineering Academy of the Republic of Kazakhstan 85, nr 3 (15.09.2022): 148–57. http://dx.doi.org/10.47533/2020.1606-146x.183.
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In this paper, a method has been developed for determining the nonlinear heat-conducting characteristics of the soil. Two-layer container complexes were created, the side faces of which are thermally insulated, so the 1D thermal conductivity equation is used. The temperature sensor is placed at the junction of two media, and a mixed boundary value problem is solved in each region. In order to provide the inverse coefficient problem with initial data, two temperature sensors are used: one sensor was placed at the open boundary of the container and recorded the soil temperature at this boundary, and the second sensor was placed a short distance from the boundary, which recorded the air temperature. The measurements were carried out in the time interval (0,4tmax). First, the initial-boundary problem of heat conduction with nonlinear coefficients is studied by the finite difference method. Two types of difference schemes are constructed: linearized and nonlinear. The linearized difference scheme is implemented numerically by the scalar Thomas method, and the nonlinear difference problem is solved by the Newton method. The solution of a linearized difference problem was taken as the initial approximation of Newton’s method. To find the thermophysical parameters, the corresponding functional is minimized using the gradient descent method. In addition, all thermophysical characteristics (8 coefficients) were found for a two-layer container with sand and chernozem.
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Rysbaiuly, B., i S. D. Alpar. "Nonlinear inverse problem of finding thermophysical characteristics". Bulletin of the National Engineering Academy of the Republic of Kazakhstan 88, nr 2 (30.06.2023): 72–81. http://dx.doi.org/10.47533/2023.1606-146x.7.
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In this paper, a method has been developed for determining the nonlinear heat-conducting characteristics of the soil. Two-layer container complexes were created, the side faces of which are thermally insulated, so the 1D thermal conductivity equation is used. The temperature sensor is placed at the junction of two media, and a mixed boundary value problem is solved in each region. In order to provide the inverse coefficient problem with initial data, two temperature sensors are used: one sensor was placed at the open boundary of the container and recorded the soil temperature at this boundary, and the second sensor was placed a short distance from the boundary, which recorded the air temperature. The measurements were carried out in the time interval (0,4tmax). First, the initial-boundary problem of heat conduction with nonlinear coefficients is studied by the finite difference method. Two types of difference schemes are constructed: linearized and nonlinear. The linearized difference scheme is implemented numerically by the scalar Thomas method, and the nonlinear difference problem is solved by the Newton method. The solution of a linearized difference problem was taken as the initial approximation of Newton’s method. To find the thermophysical parameters, the corresponding functional is minimized using the gradient descent method. In addition, all thermophysical characteristics (8 coefficients) were found for a two-layer container with sand and chernozem.
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Xu, Shi Liang. "Inverse Heat Conduction Problem of the Temperature Field with Artificial Ground Freezing Method". Advanced Materials Research 243-249 (maj 2011): 89–92. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.89.
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The Artificial Ground Freezing (AGF) Method play an important role in the geotechnical engineering and the back analysis of thermal conductivity of frozen soil is the main inverse heat conduction problem of temperature field. In this paper the physical modelling test of AGF is carried out with double-row-pipe freezing in the lab. According to the measured temperature, the back analysis of thermal conductivity of frozen soil is solved based on the two-dimensional finite element simulation and the least square principle. It is helpful to investigate the freezing process and determine the frozen wall thickness.
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Wang, Jun, Hong Guang Ji, Chuan Qing Wang i Kaiyun Luan. "Numerical Analysis for Displacement Law of Deep Alluvium Frozen Wall in Thousand Metres Vertical Well". Advanced Materials Research 243-249 (maj 2011): 2634–37. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2634.
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During freezing sinking, the displacement and affecting factors of deep alluvium frozen soil wall was a technical problem which need to be resolved. Based on designing frozen soil wall in deep alluvium in thousand metre vertical wall, making use of mathematic simulation software of FLAC after selected ten samples from exceeding 400metres depth as calculation model, which the frozen clay creep parameters with finite transformation considered, the maximum radial displacement was obtained. The factors affecting it such as frozen soil thick, height of deep alluvium, segment height, exposure time and excavated radius were utilized. The mathematic formula was acquired with regression analysis through fifty datas, and detected with in-situ measurement data. The result of two types coincids, which indicates it can provide conducting in designing frozen soil wall under similar geoloical projects.
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N. K. PETROSIAN i O. L. TIUTKIN. "EXPRESS-ANALYSIS OF THE STRESS-STRAIN STATE OF THE UNFASTENED EXCAVATION ON THE BASIS OF MODEL WITH SINGLE PARAMETERS". Bridges and tunnels: Theory, Research, Practice, nr 11 (9.12.2017): 59–66. http://dx.doi.org/10.15802/bttrp2017/158791.
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Purpose. Bases of conducting of the express-analysis of the stress-strain state of the unfastened excavation of certain diameter on the basis of finite elements analysis of model with single parameters (closeness of soil and his module of resiliency) are developed in the article. Methodology. To achieve this goal, the authors, from the standpoint of the theory of elasticity and the fundamentals of the finite element method, carried out a justification for the development of the stress-strain state around the excavation of a circular outline. A finite element model for the excavation of a circular shape has been developed. The numerical analysis of the developed model is carried out. Findings. The parameters of the stress-strain state of a finite-element model for excavation of a circular outline with single parameters, as well as with specific values of the density of the soil and its elastic modulus, are obtained. A comparative analysis was carried out, which allowed to determine the dependencies between the two models. Originality. The regularities of the stressed and deformed states of a finite-element model with single parameters are established, formulas relating its SSS parameters to a model with specific parameters are proposed. (soil density, its modulus of elasticity). Practical value. The formulas for the transition from the SSS of a finite-element model with single parameters for specific cases of soil density and its modulus of elasticity are proposed for express analysis of the stress-strain state of the unfastened excavation.
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Deru, Michael P., i Allan T. Kirkpatrick. "Ground-Coupled Heat and Moisture Transfer from Buildings Part 2–Application". Journal of Solar Energy Engineering 124, nr 1 (1.05.2001): 17–21. http://dx.doi.org/10.1115/1.1435651.
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In this paper, the effects of moisture on the heat transfer from two basic types of building foundations, a slab-on-grade and a basement, are examined. A two-dimensional finite element heat and moisture transfer program is used to show the effects of precipitation, soil type, foundation insulation, water table depth, and freezing on the heat transfer from the building foundation. Comparisons are made with a simple heat conduction model to illustrate the dependency of the soil thermal conductivity on moisture content.
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Zhang, Zechao, Hongbo Liu i Zhihua Chen. "Lateral Buckling Theory and Experimental Study on Pipe-in-Pipe Structure". Metals 9, nr 2 (4.02.2019): 185. http://dx.doi.org/10.3390/met9020185.
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With the increasing depth of marine oil and gas exploitation, more requirements have been proposed on the structure of deep-sea oil pipelines. The influencing factors of lateral buckling of a pipe-in-pipe (PIP) structure containing initial imperfections and its critical force were investigated in this study by conducting an experiment, a finite element analysis, and a theoretical derivation. The change laws on the influence of initial imperfections of the PIP structure during thermal loading were revealed through an experimental study by using imperfection amplitude and wavelength as parameters. Appropriate finite element models were established, and the influences of initial imperfections, pipe-soil interaction, and the height and the number of centralizers on the global buckling critical force of the PIP structure were analyzed. The formulas of global buckling critical force of inner and outer pipes and that under pipe-soil interaction was obtained by using a theoretical derivation method. A comparative verification with experimental and finite element (FE) models result was conducted, which provided a corresponding basis for steel pipeline design.
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Deru, Michael P., i Allan T. Kirkpatrick. "Ground-Coupled Heat and Moisture Transfer from Buildings Part 1–Analysis and Modeling*". Journal of Solar Energy Engineering 124, nr 1 (1.05.2001): 10–16. http://dx.doi.org/10.1115/1.1435652.
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Ground-heat transfer is tightly coupled with soil-moisture transfer. The coupling is threefold: heat is transferred by thermal conduction and by moisture transfer; the thermal properties of soil are strong functions of the moisture content; and moisture phase change includes latent heat effects and changes in thermal and hydraulic properties. A heat and moisture transfer model was developed to study the ground-coupled heat and moisture transfer from buildings. The model also includes detailed considerations of the atmospheric boundary conditions, including precipitation. Solutions for the soil temperature distribution are obtained using a finite element procedure. The model compared well with the seasonal variation of measured ground temperatures.
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Li, Ye Xu, Farid Paul Dawalibi i Jin Xi Ma. "Grounding System Analysis and Design Considerations for Large Hydroelectric Power Plant". Advanced Materials Research 516-517 (maj 2012): 1359–66. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.1359.
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Grounding system analysis and design considerations for large hydroelectric power plant are analyzed and discussed in this paper. The main work that has been carried out includes: constructing adequate soil structures and analyzing the effects of the finite heterogeneous soil structure, the modeled river length and the water reservoir levels; conducting accurate fault current distribution calculations and studying the influence of circulating current on the touch and step voltages. The paper discusses the design of the grounding system and its safety performance while considering the impact of the circulating current and inductive coupling from cables and long parallel conductors inside the plant. Two practical examples have been provided in this paper. Furthermore, the paper demonstrates the effectiveness of using heterogeneous finite soil volumes to analyze large hydroelectric power stations and confirms that accurate grounding software packages are required to account for large circulating currents within the ground conductors and strong inductive coupling that exists between metallic elements within the substation. The results and discussions presented here can be used as a reference for engineers to analyze extensive grounding systems and to design appropriate grounding systems for large hydroelectric power plant.
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Asensio, Gabriel, Eduardo Faleiro, Jorge Moreno i Gregorio Denche. "Electromagnetic Fields from Cloud-to-Cloud Horizontal Lightning Channel on Perfect Conducting Soil: Induced Potentials in Flying Aircraft". Applied Sciences 13, nr 17 (24.08.2023): 9584. http://dx.doi.org/10.3390/app13179584.
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Calculation expressions for the electric and magnetic fields produced by a horizontal cloud-to-cloud lightning channel, assuming a perfectly conducted ground, are proposed in this paper. These expressions depend on the current model traveling through the channel and serve as the starting point to calculate the induced fields and potentials at any point in space. The derived expressions for the fields are used to calculate the induced potentials by the channel on metallic structures such as vertically driven rods in the ground and aircraft in flight. The influence of soil with finite conductivity is discussed, and an estimation of the induced potentials in this situation is proposed.
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Shen, Guo Min, Chun Fang Lu i Yi Wang. "The Influence of Heat and Moisture Transfer in Soil on the Performance of the Ground Heat Exchanger". Advanced Materials Research 594-597 (listopad 2012): 2120–27. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.2120.
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In this paper, a numerical heat and moisture transfer model (HMTM) and a pure conduction model (PCM) were established separately for unsaturated soil around the ground heat exchanger (GHE) and were numerically solved by finite volume method. The simulation results indicate that rejecting heat into soil can reduce moisture content in the vicinity of the borehole wall. When the initial moisture content is high, moister transfer has little effect on soil thermal properties. In this case, the results of the HMTM and the PCM are basically identical. On the contrary, when the initial moisture content is low, the thermal effect has significant influence on moisture transfer around the borehole wall, and the soil thermal properties will change correspondingly. In this case, there is a large difference between the results of these two models.
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Xiong, Run, Qin Yin, Wen Yang, Yan Liu i Jun Li. "Improvement of Shaped Conductive Backfill Material for Grounding Systems". Applied Computational Electromagnetics Society 36, nr 4 (10.05.2021): 442–49. http://dx.doi.org/10.47037/2020.aces.j.360410.
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In this paper, some improvements have been proposed for low resistance shaped conductive backfill material (SCBM) based on finite-difference time-domain (FDTD) simulations in grounding systems. It is found SCBM can be produced by conjunction of several layers with conductivity decreasing gradually from inner layer to outer layer, and smooth conductivity reduction between layers would lead to a better grounding performance. It is also found cuboid shape is a much more efficient shape than cube and cylinder shapes for SCBM, and holes can be made on the SCBM’s main body. It suggested to bury SCBM vertically when ground soil permits, otherwise bury SCBM horizontally and deeper burying depth would result in smaller grounding resistance. Results show it is not needed to connect the SCBMs one by one tightly in series SCBM, and some distances is allowed without dramatically increasing grounding resistance.
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Liu, Guo Dan, Fu Sheng Liu, Dan Meng, Xu Quan Li, Zhi Gang Shi i Gang Wang. "Studied on Return Water Temperature of Buried Pipe and Soil Temperature Field of Soil-Source Heat Hump System by the Finite-Element Method". Advanced Materials Research 171-172 (grudzień 2010): 163–66. http://dx.doi.org/10.4028/www.scientific.net/amr.171-172.163.
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Heat transfer model of buried pipe heat exchanger is established first, and solved by the ANSYS finite element simulation software. Model is verified by experiment, average error is 6.4%. On the above basis, return water temperature of buried pipe and soil temperature are analyzed during whole operation. Through whole cooling season, outlet water temperature of buried pipe increased by 6.7°C, up to 21.2°C. After 45 days on transition season, temperature reduced 3.2°C, up to 18°C. Within one year, temperature difference is above 1.1°C before-and-after heating and cooling operation. It reveals that soil temperature cannot fully recover only by natural heat conduction and soil heat storage appears, which should be paid more attention in the project.
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Higa, Yoshikazu, Kohei Uehara, Hirofumi Iyama, Tatsuhiro Tamaki i Shigeru Itoh. "A Computational Simulation for Explosive Ordnance Disposal". Materials Science Forum 767 (lipiec 2013): 74–79. http://dx.doi.org/10.4028/www.scientific.net/msf.767.74.
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In order to clarify the characteristic behavior such as shockwave propagation, dispersion of sand and the crater depth due to explosive ordnance disposal, the finite element models of soil, surrounding air and explosive have been constructed based on HyperWorks-RADIOSS (®Altair) software. By conducting a series of numerical simulations, it has been observed the effect of explosion on the crater depth and diameter, overpressure exerted on sand and the surrounding air. These results based on the computational mechanics are useful data for setting the evacuation area and its distance associated with an explosive ordnance disposal.
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Rui, Yi, i Mei Yin. "Investigations of pile–soil interaction under thermo-mechanical loading". Canadian Geotechnical Journal 55, nr 7 (lipiec 2018): 1016–28. http://dx.doi.org/10.1139/cgj-2017-0091.
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Thermo-active piles that couple load bearing with ground source heat pump systems are one of the new technologies in geotechnical engineering. This paper investigates the pile–soil interaction behaviour of a thermo-active pile in overconsolidated London clay by conducting a thermo-hydro-mechanical finite element analysis using an advanced soil constitutive model. Negative and positive excess pore pressures are computed around the pile during cooling and heating, respectively. However, the difference in the radial effective stress acting on the pile–soil interface between the cooling and heating stages is small, and the pile–soil interaction is governed by the shear mobilization associated with thermally induced cyclic movements of pile expansion and contraction. During the first cooling stage, the shear stress at a small portion in the upper part of the pile reaches close to the yield values, which leads to an additional settlement about 3 mm from the original mechanical load–induced settlement of 2 mm. The shear stresses in subsequent heating and cooling cycles are much smaller than the ultimate shear stress values, because of the heavily overconsolidated nature of the London clay.
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Thomas, H. R. "On the development of a model of coupled heat and moisture transfer in unsaturated soil". Canadian Geotechnical Journal 29, nr 6 (1.12.1992): 1107–12. http://dx.doi.org/10.1139/t92-128.
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The salient characteristics of a model of coupled heat and mass transfer in unsaturated soil are presented as a subset of a more complex model of the thermal–hydraulic–mechanical behaviour of unsaturated soil currently under development. Liquid and vapour flow continuity are considered separately before combining the two into a conservation of mass equation. Heat transfer by means of conduction, latent heat of vaporisation effects, and sensible heat transfer are included. A numerical simulation of the complete formulation is achieved via the use of the finite element method for spatial discretisation, with the time varying behaviour accommodated by a finite difference technique. An application of the model to the simulation of well-controlled laboratory experiments of heat and mass transfer in nondeforming medium sand is presented. Good correlation is obtained. Confidence in the approach developed is therefore achieved before proceeding to simulate the combination of the above flow processes with the deformation of engineered clay barriers. Key words : temperature, heat transfer, moisture flow, unsaturated soil, numerical model, experimental results, numerical simulation.
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Krarti, Moncef, i David E. Claridge. "Two-Dimensional Heat Transfer From Earth-Sheltered Buildings". Journal of Solar Energy Engineering 112, nr 1 (1.02.1990): 43–50. http://dx.doi.org/10.1115/1.2930758.
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This paper describes use of the Interzone Temperature Profile Estimation (or ITPE) technique, an analytical calculation procedure to predict heat transfer within earth in contact with a structure. The solutions governing steady-state and steady-periodic heat conduction are derived for rectangular earth-sheltered buildings. The procedure accepts continuously variable values of geometric dimensions, insulation levels, and constant soil thermal characteristics and considers the presence of a finite water table level. Soil temperature profiles are shown for both steady-state and steady periodic conditions. The effects of insulation and water table depth on the heat losses from an earth-sheltered building envelope are discussed.
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Rui, Yi, i Mei Yin. "Thermo-hydro-mechanical coupling analysis of a thermo-active diaphragm wall". Canadian Geotechnical Journal 55, nr 5 (maj 2018): 720–35. http://dx.doi.org/10.1139/cgj-2017-0158.
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Thermo-active diaphragm walls that combine load bearing ability with a ground source heat pump (GSHP) are considered to be one of the new technologies in geotechnical engineering. Despite the vast range of potential applications, current thermo-active diaphragm wall designs have very limited use from a geotechnical aspect. This paper investigates the wall–soil interaction behaviour of a thermo-active diaphragm wall by conducting a thermo-hydro-mechanical finite element analysis. The GSHP operates by circulating cold coolant into the thermo-active diaphragm wall during winter. Soil contraction and small changes in the earth pressures acting on the wall are observed. The strain reversal effect makes the soil stiffness increase when the wall moves in the unexcavated side direction, and hence gives different trends for long-term wall movements compared to the linear elastic model. The GSHP operation makes the wall move in a cyclic manner, and the seasonal variation is approximately 0.5–1 mm, caused by two factors: the thermal effects on the deformation of the diaphragm wall itself and the thermally induced volume change of the soil and pore water. In addition, it is found that the change in bending moment of the wall due to the seasonal GSHP cycle is caused mainly by the thermal differential across the wall during the winter, because the seasonal changes in earth pressures acting on the diaphragm wall are very limited.
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Zhang, Liang, Tiehang Wang, Zaikun Zhao i Xin Jin. "Research on Bearing Difference between Single-Pile Composite Foundation Field Test and Group-Pile Composite Foundation of High-Rise Buildings". Buildings 13, nr 9 (22.08.2023): 2127. http://dx.doi.org/10.3390/buildings13092127.
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The reliability of high-rise buildings’ rigid-pile composite foundations primarily relies on the load test results of single-pile composite foundations. Field load tests were conducted for a high-rise building in the loess area of China, the results conformed to the design requirements. Nevertheless, the buildings experienced significant settlement after construction, which was quite different from the test results. Investigating bearing disparities between the single-pile and group-pile composite foundations in high-rise structures was necessary. Firstly, conducting an indoor interface shear test to propose a pile–soil hyperbolic contact model and integrate it into the numerical model. Subsequently, a finite element model was employed that accounts for pile–soil interactions in order to analyze discrepancies in bearing. The results show that the settlement difference rises by 56.4% as the load escalates by 100 kPa from the initial level and increases by 28.9% as the load ascends by 100 kPa to the final level. The settlement difference changes with an increasing load in a hardened curve pattern. Furthermore, differences in pile bearing characteristics and pile–soil interaction were analyzed. Negative friction occurs within 1/4 of the pile length within group-pile composite foundations, while in single-pile composite foundations, the range contracts to 1/10.
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Teixeira, F. L., Weng Cho Chew, M. Straka, M. L. Oristaglio i T. Wang. "Finite-difference time-domain simulation of ground penetrating radar on dispersive, inhomogeneous, and conductive soils". IEEE Transactions on Geoscience and Remote Sensing 36, nr 6 (1998): 1928–37. http://dx.doi.org/10.1109/36.729364.
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Ahmed, Asif, Sadik Khan, Sahadat Hossain, Tural Sadigov i Prabesh Bhandari. "Safety Prediction Model for Reinforced Highway Slope using a Machine Learning Method". Transportation Research Record: Journal of the Transportation Research Board 2674, nr 8 (9.06.2020): 761–73. http://dx.doi.org/10.1177/0361198120924415.
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Recycled plastic pin (RPP) has been proved to be an effective and inexpensive solution for shallow slope stabilization. Current practice suggests conducting numerical modeling to find out the desired factor of safety (FS) using RPP in the design of landslide repair. While the slope stability is heavily dependent on soil strength parameters and slope geometry, RPP length and spacing can also play a significant role in reaching the target factor of safety for the highway slope. During this study, a safety prediction model was developed using both statistical and machine learning (ML) approaches to use RPP in slope stabilization. Initially, parametric study was conducted using five different soil strengths, six slope heights, three slope ratios, three RPP lengths, and five RPP spacing configurations. Using the strength reduction techniques of Finite Element Modeling Software PLAXIS 2D, FS was determined for more than 1,000 combinations. Afterwards, a statistical approach was undertaken to determine a safety prediction model containing all possible parameters. Finally, an ML approach was conducted for safety model. The ML approach was found to be more accurate than the classical statistical approach with 85% accuracy of predicting the FS for an RPP reinforced highway slope. The developed model was validated against the values obtained from the numerical modeling, which indicated that the SF obtained from the developed model was in good agreement with those from finite element method (FEM) analysis.
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Zhang, Yunfeng, Erchun Zhang i Jialiang Gu. "Evaluation of Horizontal Electric Field from the Lightning Channel by Electromagnetic Field Equations of Moving Charges". International Journal of Antennas and Propagation 2019 (14.12.2019): 1–8. http://dx.doi.org/10.1155/2019/4091586.
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The horizontal electric field from the lightning return-stroke channel is evaluated by the electromagnetic field equations of moving charges in this paper. When a lightning flash strikes the ground, the charges move upward the lightning channel at the return-stroke speed, thereby producing the electromagnetic fields. According to the electromagnetic field equations of moving charges, the detained charges, uniformly moving charges, and decelerating (or accelerating) charges in each segment of the channel generate electrostatic fields, velocity fields, and radiation fields, respectively. The horizontal component of the sum is the horizontal electric field over the perfectly conducting ground. For the real soil with finite conductivity, the Wait formula is used here for the evaluation of the horizontal electric field over the realistic soil. The proposed method can avoid the oscillation of the fields in the long distance by the FDTD method and the singularity problem of the integral equation by the Sommerfeld integral method. The influences of the return-stroke speed, distance, and soil conductivity on the horizontal electric field are also analyzed by the proposed method. The conclusions can be drawn that the horizontal electric field decreases with the increasing of the return-stroke speed; the negative offset increases with the increasing of horizontal distance and with the decreasing of the soil conductivity, thereby forming the bipolar waveform. These conclusions will be practically valuable for the protection of lightning-induced overvoltage on the transmission lines.
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Pan, Lin, Xuelei Cheng i Jinhong Xia. "Similarity Criterion of Freezing Model Test considering Nonlinear Variation of Thermal Parameters with Temperature". Mathematical Problems in Engineering 2020 (7.10.2020): 1–11. http://dx.doi.org/10.1155/2020/7468034.
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The significant differences in specific heat and thermal conductivity of ice and water lead to the changes of specific heat and thermal conductivity of soil during the freezing process. This makes it hard for the temperature field similarity criterion based on constant thermal parameters to accurately reflect the temperature field evolution of soil mass caused by nonlinearity of thermal parameters in the process. Based on heat conduction differential equation considering nonlinear changes of thermal parameters, this paper uses similarity transformation method to derive the similarity criterion of the temperature field in the frozen soil model test and arrives at the conclusion that the prototype soil and model soil should meet when the original soil is used for the model test. At the same time, given the impact of the third boundary condition on the similarity criterion, the thermal physical similarity conditions for the model soil are derived. On this basis, ABAQUS finite element software is used to numerically simulate the linear and nonlinear prototype and model temperature fields. The third boundary condition considered the temperature evolution of the characteristic points during the freezing process is analyzed. The calculation results indicate that the nonlinear thermal conductivity similarity criterion established herein can correctly reflect the evolution process of the prototype frozen soil temperature field. It is also suggested that the model soil thermal parameters are reasonably calculated. At the same time, it shows that the nonlinear freezing similarity criterion of the soil, when the third boundary condition is satisfied, has clear physical meaning and higher practical value. The research results provide a practical and reasonable parameter calculation method for the model soil preparation in the frozen soil model test and a theoretical basis and technical support for the design and implementation of the water-heat-force coupling model test on frozen soil.
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Kalatehjari, Roohollah, Ali Arefnia, Ahmad Safuan A Rashid, Nazri Ali i Mohsen Hajihassani. "Determination of three-dimensional shape of failure in soil slopes". Canadian Geotechnical Journal 52, nr 9 (wrzesień 2015): 1283–301. http://dx.doi.org/10.1139/cgj-2014-0326.
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This paper presents the application of particle swarm optimization (PSO) in three-dimensional (3D) slope stability analysis to determine the shape and direction of failure as the critical slip surface. A detailed description of adopted PSO is presented and a rotating ellipsoidal shape is introduced as the possible failure surface in the analysis. Based on the limit equilibrium method, an equation of factor of safety (FoS) was developed with the ability to calculate the direction of sliding (DoS) in its internal process. A computer code was developed in Matlab to determine the 3D shape of the failure surface and calculate its FoS and DoS. Then, two example problems were used to verify the applicability of the presented code, the first by conducting a comparison between the results of the code and PLAXIS-3D finite element software and the second by re-analyzing an example from the literature to find the 3D failure surface. In addition, a hypothetical 3D asymmetric slope was introduced and analyzed to demonstrate the ability of the presented method to determine the shape and DOS of failure in 3D slope stability problems. Finally, a small-scale physical model of a 3D slope under vertical load was constructed and tested in the laboratory and the results were re-analyzed and compared with the code results. The results demonstrate the efficiency and effectiveness of the presented code in determining the 3D shape of the failure surface in soil slopes.
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Sodha, Mahendra Singh, Ashutosh Sharma i Sujeet Kumar Agarwal. "Focusing of electromagnetic beams in ionosphere with finite thermal conduction". Journal of Geophysical Research: Space Physics 112, A3 (marzec 2007): n/a. http://dx.doi.org/10.1029/2006ja012067.
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Sivtsev, Petr V., Piotr Smarzewski i Sergey P. Stepanov. "Numerical Study of Soil-Thawing Effect of Composite Piles Using GMsFEM". Journal of Composites Science 5, nr 7 (28.06.2021): 167. http://dx.doi.org/10.3390/jcs5070167.
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During construction works, it is advisable to prevent strong thawing and an increase in the moisture content of the foundations of engineering structures in the summer. Since the density of water and ice differ, due to the difference bulging of the foundation sections can occur when it freezes back in winter. In this work, the effect of fiber-reinforced piles on the thermal field of the surrounding soil is investigated numerically; that is, the study of the influence of aggregates with high and low thermal-physical properties on the temperature of frozen soils is conducted. Basalt and steel fiber reinforcement are compared. The difficulty of this work is that the inclusions inside piles are too small compared to the pile itself. Therefore, to solve the Stefan problem, a generalized multiscale finite element method (GMsFEM) was used. In the GMsFEM, the usual conforming partition of the domain into a coarse grid was used. It allowed reducing problem size and, consequently, accelerating the calculations. Results of the multiscale solution were compared with fine-scale solution, the accuracy of GMsFEM was investigated, and the optimal solution parameters were defined. Therefore, GMsFEM was shown to be well suited for the designated task. Collation of basalt and steel fiber reinforcement showed a beneficial effect of high thermal conductive material inclusion on freezing of piles in winter.
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Zhang, Linlin, Zhonghua Shi i Tianhao Yuan. "Study on the Coupled Heat Transfer Model Based on Groundwater Advection and Axial Heat Conduction for the Double U-Tube Vertical Borehole Heat Exchanger". Sustainability 12, nr 18 (8.09.2020): 7345. http://dx.doi.org/10.3390/su12187345.
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In this paper, a dynamic heat transfer model for the vertical double U-tube borehole heat exchanger (BHE) was developed to comprehensively address the coupled heat transfer between the in-tube fluid and the soil with groundwater advection. A new concept of the heat transfer effectiveness was also proposed to evaluate the BHE heat exchange performance together with the index of the heat transfer rate. The moving finite line heat source model was selected for heat transfer outside the borehole and the steady-state model for inside the borehole. The data obtained in an on-site thermal response test were used to validate the physical model of the BHE. Then, the effects of soil type, groundwater advection velocity, inlet water flow rate, and temperature on the outlet water temperature of BHE were explored. Results show that ignoring the effects of groundwater advection in sand gravel may lead to deviation in the heat transfer rate of up to 38.9% of the ground loop design. The groundwater advection fosters the heat transfer of BHE. An increase in advection velocity may also help to shorten the time which takes the surrounding soil to reach a stable temperature. The mass flow rate of the inlet water to the BHE should be more than 0.5 kg·s−1 but should not exceed a certain upper limit under the practical engineering applications with common scale BHE. The efficiency of the heat transfer of the double U-tube BHE was determined jointly by factors such as the soil’s physical properties and the groundwater advection velocity.
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Hromadka, T. V. "Analyzing Numerical Errors in Domain Heat Transport Models Using the CVBEM". Journal of Offshore Mechanics and Arctic Engineering 109, nr 2 (1.05.1987): 163–69. http://dx.doi.org/10.1115/1.3257005.
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Besides providing an exact solution for steady-state heat conduction processes (Laplace-Poisson equations), the CVBEM (complex variable boundary element method) can be used for the numerical error analysis of domain model solutions. For problems where soil-water phase change latent heat effects dominate the thermal regime, heat transport can be approximately modeled as a time-stepped steady-state condition in the thawed and frozen regions, respectively. The CVBEM provides an exact solution of the two-dimensional steady-state heat transport problem, and also provides the error in matching the prescribed boundary conditions by the development of a modeling error distribution or an approximate boundary generation. Consequently, this error evaluation can be used to develop highly accurate CVBEM models of the heat transport process, and the resulting model can be used as a test case for evaluating the precision of domain models based on finite elements or finite differences.
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Rysbaiuly, Bolatbek, i Sultan Alpar. "Nonlinear Inverse Heat Transfer Problem". Journal of Physics: Conference Series 2224, nr 1 (1.04.2022): 012039. http://dx.doi.org/10.1088/1742-6596/2224/1/012039.
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Abstract In this work, a method for finding nonlinear heat-conducting characteristics of soil is developed. Two-layer complexes of containers were created, the side faces of which are thermally insulated, so the 1D thermal conductivity equation is used. A temperature sensor is placed at the junction of the two media, and a mixed boundary value problem is solved in each area. In order to provide the inverse coefficient problem with initial data, two temperature sensors are used: one sensor was placed at the open border of the container and recorded the soil temperature at this border, and the second sensor was placed at a short distance from the border, which recorded the air temperature. The measurements were carried out in the time interval (0,4t max ). First, the initial-boundary value problem of thermal conductivity with nonlinear coefficients is investigated by the finite difference method. Two types of difference schemes are constructed: linearized and nonlinear. The linearized difference scheme is implemented numerically by the scalar Thomas method, and the nonlinear difference problem is solved by the Newton method. The solution of the linearized difference problem was taken as the initial approximation of the Newton method. To find the thermophysical parameters, the corresponding functional is minimized using the gradient descent method. In addition, all thermophysical characteristics (8 coefficients) were found for a two-layer container with sand and chernozem.
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Akimov, M., S. Mordovskoy i N. Starostin. "ESTIMATION OF THERMAL INSULATION THICKNESS AND DEPTH OF UNDERGROUND POLYETHYLENE HEAT SUPPLY PIPELINES IN REGIONS WITH PERMAFROST". Bulletin of Belgorod State Technological University named after. V. G. Shukhov 5, nr 11 (4.12.2020): 48–56. http://dx.doi.org/10.34031/2071-7318-2020-5-11-48-56.
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The process of thawing and freezing of the host soil of an underground polyethylene heat supply pipeline with thermal insulation, operated in areas of permafrost distribution, is considered. The task is to determine the thickness of the thermal insulation of the pipeline and the size of its depth based on the analysis of the temperature field in the ground during long-term cycle. The temperature field in the "insulated pipe-ground" system, which changes over time, is proposed to be determined by solving the heat conduction equations in polar coordinates. In this case, a bundle of pipes is considered as one pipe of equivalent radius. This approach allows to simplify the interface conditions of the pipe, thermal insulation, polyethylene shell and the host soil, as well as to use a simple numerical method for solving the equation – the finite difference method. The results of calculations of the maximum depth of soil thawing from the depth of the heat supply pipe at different thicknesses of thermal insulation are presented. It is proposed to determine the optimal depth of the underground heat supply pipeline from the condition of annual establishment of the zero isotherm of the host soil at the level of the boundary of the active soil layer by the beginning of the heating season. The possibility of finding a zero isotherm at this level is illustrated by calculations of isotherms by the beginning of the heating season (September) at various depths and thicknesses of thermal insulation. Based on the results of calculations the method of estimation the insulation thickness and depth of the pipeline from the condition of minimizing the functional that characterizes the measure of deviation of the ordinates of the zero isotherm on the left-hand boundary of the region from the depth of the active soil layer at the beginning of the heating season.
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Wang, Zong Gang, i Zhen Wei. "Finite Element Simulation of Freezing Technology for Borehole Stability of Gas Drilling". Advanced Materials Research 962-965 (czerwiec 2014): 415–18. http://dx.doi.org/10.4028/www.scientific.net/amr.962-965.415.
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The gas drilling mainly relies on the high speed air flow to carry the cuttings. The formation water or oil mixed with the cuttings and then they stick together in clumps after the formation water or oil went into the hole annulus, the clumps stick on the drill string and the borehole. The clumps may block the hole annulus and cause the stick or bury the drill string and many other complex accident. It could stop the cuttings from sticking with the liquid through freezing the formation fluid with the liquid nitrogen. And the natural geotechnical becomes into the frozen soil, and forms the temporary solid which is intact, high strength and low-permeability. This paper utilize the ANSYS finite element program to simulate the 3D model of borehole and hole wall to calculate the freezing radius of the steady state, heat loss, temperature of the freezing point and the conductive heat time of the unsteady state. And this study has provided the basis of the freezing technology for borehole stability of gas drilling.
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Adjali, M. H., M. Davies i J. Littler. "A numerical simulation of measured transient temperatures in the walls, floor and surrounding soil of a buried structure". International Journal of Numerical Methods for Heat & Fluid Flow 9, nr 4 (1.06.1999): 405–23. http://dx.doi.org/10.1108/09615539910266585.
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Presents the results of a numerical simulation of measured heat transfer through a region surrounding a buried structure. The model applied in the study is a widely used whole building thermal simulation program of a type which predicts the thermal response of structures for building services requirements. A multi‐dimensional numerical conductive heat transfer module has been added to this program but this does not specifically address earth‐contact heat flows. This work attempts to assess the accuracy of the overall package when predicting earth‐coupled heat transfer. It is common practice in the field of building services not to use specific earth‐contact models and so it is important to assess the likely errors thus involved. The predictions of the finite‐volume model are compared with one year of data from a basement test facility. The results are analysed using the Differential Sensitivity Analysis method and an attempt is made to correlate predictive errors with periods of rainfall and snow coverage. It seems that a purely conductive model may be capable, given accurate input data, of satisfactorily predicting the transient temperature variations in the soil/concrete envelope surrounding this structure for the period of the year when no snow coverage is present. However, if one is to accurately model regions of earth‐contact (particularly at shallow depths) in a climate in which rainfall and snow are significant then these influences should be explicitly modelled.
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La Fata, Alice, Martino Nicora, Daniele Mestriner, Riccardo Aramini, Renato Procopio, Massimo Brignone i Federico Delfino. "Lightning Electromagnetic Fields Computation: A Review of the Available Approaches". Energies 16, nr 5 (3.03.2023): 2436. http://dx.doi.org/10.3390/en16052436.
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Lightning represents one of the most critical issues for electrical infrastructure. In dealing with overhead distribution line systems, indirect lightning strikes can lead to induced voltages overcoming the critical flashover value of the line, thus damaging the insulators. The computation of lightning-induced voltages requires the modeling of the lightning current, the evaluation of the lightning electromagnetic fields and the solution of the field-to-line coupling equations. The numerical calculation of the lightning electromagnetic fields is time-consuming and is strongly dependent on the lightning channel modeling and soil properties. This article presents a review of the most widely adopted methods to calculate the lightning electromagnetic fields, starting from the classical formulation, which requires numerical integration, and highlighting the most effective approaches that have been developed to reduce computational effort. This is done first for the case of a perfectly conducting ground, then the available formulations to account for the ground finite conductivity are presented together with their possible implementations in both the frequency and time domains.
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Narsilio, Guillermo A., Jeremy Kress i Tae Sup Yun. "Characterisation of conduction phenomena in soils at the particle-scale: Finite element analyses in conjunction with synthetic 3D imaging". Computers and Geotechnics 37, nr 7-8 (listopad 2010): 828–36. http://dx.doi.org/10.1016/j.compgeo.2010.07.002.
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Lucazeau, F., i F. Rolandone. "Heat-flow and subsurface temperature history at the site of Saraya (eastern Senegal)". Solid Earth 3, nr 2 (20.08.2012): 213–24. http://dx.doi.org/10.5194/se-3-213-2012.
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Abstract. New temperature measurements from eight boreholes in the West African Craton (WAC) reveal superficial perturbations down to 100 m below the alteration zone. These perturbations are both related to a recent increase in the surface air temperature (SAT) and to the site effects caused by fluid circulations and/or the lower conduction in the alterites. The ground surface temperature (GST), inverted from the boreholes temperatures, increased slowly in the past (~0.4 °C from 1700 to 1940) and then, more importantly, in recent years (~1.5 °C from 1940 to 2010). This recent trend is consistent with the increase of the SAT recorded at two nearby meteorological stations (Tambacounda and Kedougou), and more generally in the Sahel with a coeval rainfall decrease. Site effects are superimposed to the climatic effect and interpreted by advective (circulation of fluids) or conductive (lower conductivity of laterite and of high-porosity sand) perturbations. We used a 1-D finite differences thermal model and a Monte-Carlo procedure to find the best estimates of these site perturbations: all the eight borehole temperature logs can be interpreted with the same basal heat-flow and the same surface temperature history, but with some realistic changes of thermal conductivity and/or fluid velocity. The GST trend observed in Senegal can be confirmed by two previous borehole measurements made in 1983 in other locations of West Africa, the first one in an arid zone of northern Mali and the second one in a sub-humid zone in southern Mali. Finally, the background heat-flow is low (31±2 mW m−2), which makes this part of the WAC more similar with the observations in the southern part (33±8 mW m−2) rather than with those in the northern part and in the Pan-African domains where the surface heat-flow is 15–20 mW m−2 higher.
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Farid, Arvin, Holly Gunderson, Rakesh Acharya i Jim Browning. "Electromagnetic Waves’ Impact on Hydraulic Conductivity of Granular Soils". Geotechnics 3, nr 3 (30.06.2023): 561–83. http://dx.doi.org/10.3390/geotechnics3030031.
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Electromagnetic (EM) waves, traditionally used for purposes such as geophysical characterization, impact properties to be measured. This paper describes the effects of radio frequency (RF) waves on the hydraulic conductivity of glass beads and natural sand. A series of tests was conducted using a customized, rigid-wall, cylindrical permeameter inside a resonant cavity made of Plexiglas covered with electrically conductive transparent films. Constant-head ASTM-D2434 tests were performed to measure the samples’ hydraulic conductivity. RF stimulation was performed using a magnetically coupled loop antenna at various frequencies and input RF-power levels. The hydraulic conductivity of both natural sand and glass-bead samples increased with RF stimulation. Furthermore, the measurement of the electric field component of RF waves was also performed to illustrate the pattern of the electric field, as well as evaluate RF’s impact on the hydraulic conductivity tests. The electric field was numerically simulated and validated against experimentally measured electric fields. A finite-difference numerical model was developed in MATLAB to analyze the seepage flow, which was then validated against the experimental results. An optimization scheme was then used to develop a governing equation for RF’s impact on hydraulic conductivity.
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Blattner Martinho, Lucas, i Viviane Cristine Silva. "Effects of External Currents and Soil Heterogeneities on an Approximate Boundary Condition for the 3-D Finite Element Analysis of Subsurface Conductive Coupling Problems". IEEE Transactions on Magnetics 51, nr 3 (marzec 2015): 1–4. http://dx.doi.org/10.1109/tmag.2014.2347354.
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Robert, D. J., P. Rajeev, J. Kodikara i B. Rajani. "Equation to predict maximum pipe stress incorporating internal and external loadings on buried pipes". Canadian Geotechnical Journal 53, nr 8 (sierpień 2016): 1315–31. http://dx.doi.org/10.1139/cgj-2015-0500.
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Pipelines used for water and other services are very important lifelines in modern society. Commonly, these buried pipes are subjected to significant stresses due to external (traffic and earth) and internal (water pressure) loads. As many of these pipelines were laid sometime in the last century or earlier, in most cases their condition has deteriorated primarily by electrochemical and (or) microbiological corrosion. Corrosion activity (internal and external) can manifest in various forms, but in many cases will lead to reduced pipe thickness, which in turn leads to an increase in pipe stresses induced by the external and internal loads. Currently available analytical procedures to estimate pipe stresses are based on oversimplifications such as the two-dimensional (2-D) analysis based on Winkler springs, limiting their application to general pipe burial conditions. This paper describes the application of a three-dimensional (3-D) finite element method to analyse a buried pipe subjected to external and internal loads. Firstly, the finite element model is validated against the data from field tests conducted on the basis of a cast iron pipe that was laid in 1930 at Strathfield, Sydney, Australia. The results of these 3-D finite element analyses are then used to develop a closed-form expression to predict maximum stresses in pipes of different sizes buried in different soil types. Having obtained a good agreement between the proposed model outcomes and the 3-D finite element analysis results, the proposed model has been validated against the field test data under different internal and external loadings. The verified outcomes of the model reveal that it can be used to predict maximum stresses without conducting a full-scale finite element analysis, which often requires specific computational resources and computational skills. Furthermore, the proposed model can be used in probabilistic analyses, where a large number of calculations need to be carried out to account for the uncertainty of the input variables. The applications of the model are also discussed in relation to the assessment of pipe performance and remaining safe life.
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Zheng, Gang, Yu Diao i C. W. W. Ng. "Parametric analysis of the effects of stress relief on the performance and capacity of piles in nondilative soils". Canadian Geotechnical Journal 48, nr 9 (wrzesień 2011): 1354–63. http://dx.doi.org/10.1139/t11-043.
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To provide support to superstructure and substructure, piles are often installed beneath a deep basement prior to its excavation. However, the effects of stress relief on the performance and capacity of piles due to deep excavation are rarely reported in the literature. In this study, two different types of pile load tests were simulated with and without considering excavation effects by conducting parametric axisymmetric finite element analyses. The first test was a pile load test on a sleeved pile from the ground surface prior to deep excavation, and the other is a load test on an unsleeved pile at the final excavated level. It is found that an excavation could reduce the pile capacity by up to 45% and pile stiffness by up to 75%. The effects of stress relief due to an excavation increase with normalized excavation depth (H/L) and excavation radius (R/H). Moreover, the maximum tension induced in a pile by excavation varies with H/L, and it has a peak value when 1 < H/L < 1.25. The value of maximum tension increases with the pile–soil modulus ratio (Ep/Esm). When Ep/Esm = 100, peak tension develops at 0.5H. On the other hand, tension reaches a peak at 0.7H when Ep/Esm = 20.
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KONDRATENKO, Andrei. "Technological aspects of cased wells construction with cyclical-flow transportation of rock". Journal of Mining Institute 246 (23.01.2021): 610–16. http://dx.doi.org/10.31897/pmi.2020.6.2.
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A high-performance technology for constructing cased wells is proposed. Essence of the technology is the advance insertion of the casing pipe into the sedimentary rock mass and the cyclical-flow transportation of the soil rock portions using the compressed air pressure supplied to the open bottomhole end of the pipe through a separate line. Results of mathematical modeling for the process of impact insertion of a hollow pipe into a soil mass in horizontal and vertical settings are considered. Modeling of the technology is implemented by the finite element method in the ANSYS Mechanical software. Parameters of the pipe insertion in the sedimentary rock mass are determined - value of the cleaning step and the impact energy required to insert the pipe at a given depth. Calculations were performed for pipes with a diameter from 325 to 730 mm. Insertion coefficient is introduced, which characterizes the resistance of rocks to destruction during the dynamic penetration of the casing pipe in one impact blow of the pneumatic hammer. An overview of the prospects for the application of the proposed technology in geological exploration, when conducting horizontal wells of a small cross-section using a trenchless method of construction and borehole methods of mining, is presented. A variant of using the technology for determining the strength properties of rocks is proposed. Some features of the technology application at industrial facilities of the construction and mining industry are considered: for trenchless laying of underground utilities and for installing starting conductors when constructing degassing wells from the surface in coal deposits. Results of a technical and economic assessment of the proposed technology efficiency when installing starting conductors in sedimentary rocks at mining allotments of coal mines are presented.
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van der Linden, Steven J. A., Peter Baas, J. Antoon van Hooft, Ivo G. S. van Hooijdonk, Fred C. Bosveld i Bas J. H. van de Wiel. "Local Characteristics of the Nocturnal Boundary Layer in Response to External Pressure Forcing". Journal of Applied Meteorology and Climatology 56, nr 11 (listopad 2017): 3035–47. http://dx.doi.org/10.1175/jamc-d-17-0011.1.
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AbstractGeostrophic wind speed data, derived from pressure observations, are used in combination with tower measurements to investigate the nocturnal stable boundary layer at Cabauw, the Netherlands. Since the geostrophic wind speed is not directly influenced by local nocturnal stability, it may be regarded as an external forcing parameter of the nocturnal stable boundary layer. This is in contrast to local parameters such as in situ wind speed, the Monin–Obukhov stability parameter (z/L), or the local Richardson number. To characterize the stable boundary layer, ensemble averages of clear-sky nights with similar geostrophic wind speeds are formed. In this manner, the mean dynamical behavior of near-surface turbulent characteristics and composite profiles of wind and temperature are systematically investigated. The classification is found to result in a gradual ordering of the diagnosed variables in terms of the geostrophic wind speed. In an ensemble sense the transition from the weakly stable to very stable boundary layer is more gradual than expected. Interestingly, for very weak geostrophic winds, turbulent activity is found to be negligibly small while the resulting boundary cooling stays finite. Realistic numerical simulations for those cases should therefore have a comprehensive description of other thermodynamic processes such as soil heat conduction and radiative transfer.