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1
Ye, Wanjun, Yang Bai, Chenyang Cui et Xu Duan. « Deterioration of the Internal Structure of Loess under Dry-Wet Cycles ». Advances in Civil Engineering 2020 (16 juillet 2020) : 1–17. http://dx.doi.org/10.1155/2020/8881423.
Texte intégralRésumé :
To understand the structural damage evolution process of loess under the action of dry-wet cycles, a triaxial test of a dry-wet cycle was performed by considering three influencing factors: initial moisture content, amplitude of the dry-wet cycle, and number of dry-wet cycles. The stress-strain curves of undisturbed loess samples at different cycling times vary under different compacted loess cycles. Under the same axial strain, the stress value of the undisturbed loess is higher than that of the loess sample after a dry-wet cycle, indicating that such cycle can reduce the strength of loess. As the number and amplitude of dry-wet cycles increase, the shear strength of the loess sample and the value of cohesion (c) of the strength index gradually decrease, and the amplitude gradually decreases. With an increase in the number and amplitude of dry-wet cycles, the change in the internal friction angle of the strength index is inevident, indicating that the effect of dry-wet cycles on the internal friction angle of loess is insignificant. Computed tomography (CT) scan experiments were also conducted to obtain the evolution of loess cracks before and after a dry-wet cycle. Studies have shown that as the number and amplitude of dry-wet cycles increase, the mean (ME) value of CT decreases, the standard deviation (SD) value increases, and the ME value is obtained during the initial stage of a dry-wet cycle. Meanwhile, the decreasing trend of ME and the increasing trend of SD values are most evident during the period of a dry-wet cycle. In conclusion, dry-wet cycles promote the development of cracks.
2
Liu, Kai, Tianfeng Gu, Xingang Wang et Jiading Wang. « Time-Dependence of the Mechanical Behavior of Loess after Dry-Wet Cycles ». Applied Sciences 12, no 3 (24 janvier 2022) : 1212. http://dx.doi.org/10.3390/app12031212.
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The structure, time-dependent mechanical deformation, and strength characteristics of loess, which is loose and porous with well-developed vertical joints, are greatly affected by the dry-wet cycles, which are attributed to periodic artificial irrigation, rainfall, and water evaporation. To better understand the creep characteristics of loess under the effect of dry-wet cycles, Q2 loess samples obtained from the South Jingyang County, China, were subjected to different dry-wet cycles (0, 5, 10, 15, 20) and sheared in triaxial creep tests. The experimental results revealed that: firstly, the maximum value of the deviatoric stress corresponding to creep failure gradually decreases with an increase in the dry-wet cycles. Secondly, the long-term strength of the loess after dry-wet cycles were obtained through the Isochronous Curve Method. It is found that the long-term strength and the number of dry-wet cycles showed an exponential decreasing relationship. In addition, the creep damage mechanism of loess due to dry-wet cycles is proposed. This study may provide the basis for understanding the mechanical behavior of the loess under the effect of dry-wet cycles, as well as guidelines for the prevention and prediction of loess landslide stability.
3
Liang-Xiao, Xiong, et Song Xiao-Gang. « Mechanical Properties of Cement Mortar after Dry–Wet Cycles and High Temperature ». Civil Engineering Journal 6, no 5 (1 mai 2020) : 1031–38. http://dx.doi.org/10.28991/cej-2020-03091526.
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The dry–wet cycle and high temperature exposure are important factors affecting the normal use and durability of concrete structures. The objective of this work is to investigate the mechanical properties of cement mortar specimens after combinations of dry–wet cycles and high temperature exposures, uniaxial compressive tests on cement mortar specimens were carried out under the following two sets of conditions: (1) high temperature treatment followed by a dry–wet cycle and (2) a dry–wet cycle followed by high temperature treatment. The results show that the compressive strength of specimens increases with the number of dry–wet cycles. After a dry–wet cycle and then a high temperature treatment procedure, the compressive strength of a specimen will first decrease and then increase with the number of dry–wet cycles. The strain at the peak stress of cement mortar decreases as the number of dry–wet cycles increases. At present, there are few research results about the mechanical properties of concrete first after combinations of dry–wet cycles and high temperature exposures. The work in this paper can enrich the results in this area.
4
Zhu, Rui, Ying-hao Huang, Zhu Song et Feng Zhou. « Volume Changes and Mechanical Properties of Expansive Mudstone below Canals under Wet-Dry/Wet-Dry-Freeze-Thaw Cycles ». Advances in Civil Engineering 2021 (5 juin 2021) : 1–11. http://dx.doi.org/10.1155/2021/3791692.
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The complex environment in northern China is the main reason for degradation of expansive mudstone below the canals, which resulted in instability and damage of canal slopes. In this study, a serial of laboratory tests was conducted to explore the volume changes and mechanical behaviors of expansive mudstone below the canals in Xinjiang. The experimental program includes wet-dry (WD) and wet-dry-freeze-thaw (WDFT) tests, volume measurement, and unconfined compression tests. The test results show that during the WD cycles, the volume changes of expansive mudstones with a higher dry range would be more significant. The freeze-thaw process in the WDFT cycles resulted in a decrease of volume change ranges when the expansive mudstones had a relatively smaller dry range and a slight increase of volume change ranges when the expansive mudstones had a relatively larger dry range. In the meantime, the stress-strain relationships of expansive mudstones with different dry ranges all presented strain softening under the cycles of WD or WDFT. The first cycle resulted in a significant decrease of failure strength. After seven WD/WDFT cycles, the failure strength of expansive mudstones with different dry ranges decreased by 37.2%∼59.1%. In addition, the freeze-thaw process in the WDFT cycles promoted the softening of the stress-strain relationships and aggravated the failure strength attenuation of expansive mudstones. Through this study, we expect to provide a preliminary basis for the construction and maintenance of expansive mudstone canals in Xinjiang.
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Jiang, Ping, Xuhui Zhou, Jian Qian et Na Li. « Experimental Study on the Influence of Dry–Wet Cycles on the Static and Dynamic Characteristics of Fiber-Modified Lime and Fly Ash-Stabilized Iron Tailings at Early Curing Age ». Crystals 12, no 5 (19 avril 2022) : 568. http://dx.doi.org/10.3390/cryst12050568.
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Using fiber, lime and fly ash to modify iron tailings and apply them to a road base is an effective way to utilize iron tailings as resources. To explore the influence of fiber on lime and fly ash-stabilized iron tailings (EIT) under dry and wet cycles at an early curing age, the static and dynamic characteristics of EIT and fiber-modified lime and fly ash-stabilized iron tailings (FEIT) under dry and wet cycles were studied through an unconfined compressive strength (UCS) test, splitting test and dynamic triaxial test. The results show the following. (1) EIT and FEIT still have high UCS and splitting strength after dry–wet cycles, and the dry–wet cycles can promote the static properties of FEIT. (2) The dry–wet cycle is the main factor affecting the change in the dynamic elastic modulus of EIT and FEIT. The dynamic elastic modulus of EIT first increases and then decreases with the increase in dry–wet cycles, and the dynamic elastic modulus of FEIT first decreases and then increases with the increase in dry–wet cycles. The damping ratio of EIT and FEIT decreases with the increase in dry–wet cycles, and then tends to be stable. (3) After seven dry–wet cycles, the compressive performance, tensile performance, deformation resistance and vibration resistance of FEIT are better than those of EIT. This study can provide a reference for the resource application of iron tailings in road engineering.
6
Xu, Jian, Chang Ren, Songhe Wang, Jingyu Gao et Xiangang Zhou. « Permeability and Microstructure of a Saline Intact Loess after Dry-Wet Cycles ». Advances in Civil Engineering 2021 (10 mars 2021) : 1–18. http://dx.doi.org/10.1155/2021/6653697.
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Influenced by both dry-wet cycles and salt weathering, the loess will exhibit significant changes in microstructure and permeability, which threatens the stability of loess slopes. Triaxial permeability tests and industrial computed tomography (CT) scans were carried out on saline intact loess with sodium sulfate. The relationship between permeability and pore structure of the loess after dry-wet cycles was discussed. Results show that the permeability coefficient of loess increases after dry-wet cycles, with the increment declining. After specified dry-wet cycles, the permeability coefficient increases approximately linearly with sodium sulfate content. However, the permeability coefficient significantly declines at higher confining pressures, while its attenuation rate decreases. An empirical relationship based on log 10 1 + e − log 10 k was proposed to estimate the permeability coefficient of saline intact loess considering dry-wet cycles and salt content. Comparisons of measured and calculated results proved its rationality. CT scan images imply the damage to soil microstructure induced by dry-wet cycles and salt weathering, corresponding to the decline of the mean CT value (ME) and the increase of both crack ratio and fractal dimension of crack network.
7
Qi, Yanli, MingZhou Bai, Hao Zhou, Hai Shi, Pengxiang Li et Bohu He. « Study on the Mechanical Properties of Red Clay under Drying-Wetting Cycles ». Advances in Materials Science and Engineering 2021 (15 juin 2021) : 1–16. http://dx.doi.org/10.1155/2021/8665167.
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To study the mechanical properties of red clay under repeated dry and wet cycle test conditions, in this paper, the disturbed red clay in an engineering area in Liuzhou, Guangxi Province, was taken as the research object. By artificially controlling different dry and wet cycles in the laboratory, a direct shear test and triaxial consolidation drainage test were carried out on the red clay samples after different dry and wet cycles. The stress-strain curve and change rule of corresponding c and φ values were obtained. The results showed that, in both the direct shear test and the triaxial test, the shear strength parameters of red clay decreased with an increase in the number of dry and wet cycles and the attenuation was most obvious during the first cycle. With an increase in the number of dry and wet cycles, the attenuation gradually decreased. The constitutive model of the deviatoric stress and strain curve of red clay under dry and wet cycles was a plastic-hardening type. By analyzing the variation in parameters in the P-H model, the relationship between c, φ, and the number of dry and wet cycles n was obtained. The results showed that the parameters had different degrees of attenuation with the action of dry and wet cycles. To explain the above rules, some samples under different drying-wetting cycles were selected for environmental electron microscope scanning, and appropriate assumptions were made based on the microstructure.
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Song, Zhaoyang, Lihui Sun, Shouye Cheng, Zhiqiang Liu, Jie Tan et Fangbo Ning. « Experimental Study on the Property Degradation and Failure Mechanism of Weakly Cemented Sandstone under Dry-Wet Cycles ». Advances in Materials Science and Engineering 2022 (18 janvier 2022) : 1–16. http://dx.doi.org/10.1155/2022/9431319.
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Taking the weakly cemented sandstone of Ordos, China, as the research object, the evolution law between the relative stress of weakly cemented sandstone and the multiparameters of the acoustic emission under different dry-wet cycles was explored, and the critical failure identification mode of weakly cemented sandstone under dry-wet cycle was established. The results show that as the number of dry-wet cycles increases, the wave velocity loss rate gradually increases. Overall, the longitudinal wave loss rate is larger than the shear wave loss rate, indicating that the longitudinal wave is more sensitive to the degradation of weakly cemented sandstone. With an increase in the number of dry-wet cycles, the crack is mainly caused by the main crack penetration failure, and the secondary crack is significantly reduced. The fractal dimension decreases with an increase in the dry-wet cycles and reaches its maximum at 0 dry-wet cycles, which means that 0 dry-wet cycles witness the most complex morphology of fractures within the weakly cemented sandstone. This finding indicates that the dry-wet cycle inhibits the generation and expansion of fractures. The event rate appears to be close to 0 before the rupture, and then the platform oscillates, followed by a sudden increase. The acoustic emission b value is relatively high during the initial stage and then decreases, which is the initial damage process. The elastoplastic phase rises again, the peak stage decreases rapidly, and the weakly cemented sandstone undergoes unstable damage. The change in the acoustic emission entropy value is exactly the opposite of the b value change law. When the weakly cemented sandstone reaches the critical failure state under different dry-wet cycles, the relative stress value is 95%. The test results provide new methods and a basis for the damage evolution mechanism and fracture prediction of weakly cemented sandstone under dry-wet cycles.
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Wang, Linzhi, Mingzhong Gao et Jiqiang Zhang. « Effect of Continuous Loading Coupled with Wet–Dry Cycles on Strength Deterioration of Concrete ». Sustainability 14, no 20 (18 octobre 2022) : 13407. http://dx.doi.org/10.3390/su142013407.
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In practical engineering, concrete is often under continuous stress conditions and there are limitations in considering the effect of wet–dry cycles alone on the strength deterioration of concrete. In order to study the deterioration of concrete strength under the coupling of load and wet-dry cycles, concrete specimens were loaded with 0%, 10%, 20%, and 35% stress levels and coupled to undergo one, three, and seven wet–dry cycles. The strength deterioration of the concrete was obtained by uniaxial compression and the regression equation was established. The strength deterioration mechanism of the concrete under the coupled conditions was analyzed and revealed through an AE acoustic emission technique and nuclear magnetic resonance technique. The results of the study show that, with the same number of wet–dry cycles, there are two thresholds of a and b for the uniaxial compressive strength of concrete with the stress level, and with the progression of wet–dry cycles, the length of the interval from a to b gradually shortens until it reaches 0. The cumulative AE energy of concrete decreases with the progression of wet–dry cycles; using the initiating crack stress as the threshold, the calm phase of concrete acoustic emission, the fluctuating phase, and the NMR T2 spectral peak area show different patterns of variation with the increase in the number of wet–dry cycles.
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Li, S. N., Z. H. Huang, Q. Liang, J. Liu, S. L. Luo et W. Q. Zhou. « Evolution Mechanism of Mesocrack and Macrocrack Propagation in Carbonaceous Mudstone under the Action of Dry-Wet Cycles ». Geofluids 2022 (19 juillet 2022) : 1–8. http://dx.doi.org/10.1155/2022/6768370.
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The crack propagation evolution of carbonaceous mudstone under the action of dry-wet cycles is an important cause of the unstable failure of this type of slope. This paper attempts to reveal the evolution mechanism of mesocrack and macrocrack propagation in carbonaceous mudstone under the action of dry-wet cycles from chemical, physical, and mechanical perspectives. Firstly, the soaking solution of carbonaceous mudstone during the dry-wet cycles was extracted for an ion concentration test to analyze the chemical reactions of carbonaceous mudstone. Then, CT scans were performed on the carbonaceous mudstone samples to study the changing pattern of mesostructure of carbonaceous mudstone during the dry-wet cycles. In the end, the mechanical properties and failure characteristics of carbonaceous mudstone after dry-wet cycles were studied by triaxial compression tests. The results showed that chemical reactions such as calcite dissolution, potassium feldspar hydrolysis, and sodium feldspar hydrolysis occurred during the dry-wet cycle of carbonaceous mudstone. Affected by the dry-wet cycles, the mesostructure of the carbonaceous mudstone gradually changed from face-face contact and edge-face contact to edge-corner contact and corner-corner contact, and the interlayer flake structure was opened and was locally curled and fractured. With the increase in the number of dry-wet cycles, the failure characteristic of carbonaceous mudstone transformed from tensile failure to shear failure, the failure surface of carbonaceous mudstone was deflected from 90° to 60°, and the crack propagation path of carbonaceous mudstone became more complicated. The chemical reaction of carbonaceous mudstone minerals during the dry-wet cycle is an important reason for the initiation and development of pores. The dry-wet cycle aggregates the propagation of mesocracks and structural disorder, transforming the uniform stress state of the rock mesostructure to the concentrated stress state, which is the important reason for the macrocrack propagation evolution of carbonaceous mudstone.
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Zhang, Jun, Yuan Gao et Yudong Han. « Interior Humidity of Concrete under Dry-Wet Cycles ». Journal of Materials in Civil Engineering 24, no 3 (mars 2012) : 289–98. http://dx.doi.org/10.1061/(asce)mt.1943-5533.0000382.
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He, Jun, Lei Zhang et Chi Zhang. « Durability Analysis of Sludge Solidified with Soda Residue Subjected to Dry-Wet and Freeze-Thaw Cycles ». Advances in Civil Engineering 2021 (16 avril 2021) : 1–12. http://dx.doi.org/10.1155/2021/9960416.
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Soda residue (SR), ground-granulated blast-furnace slag (GGBS), and quicklime (QL) were employed for solidifying sewage sludge, which is a technique for sustainable development by transforming industrial solid waste and sludge into engineering fill material such as backfill material in mine or abandoned caverns. The durability of solidified sludge against dry-wet and freeze-thaw cycles was investigated by unconfined compressive strength (UCS), X-ray diffraction, scanning electron microscopy, and nuclear magnetic resonance tests. The results demonstrated that the SR-GGBS-QL solidified sludge had good dry-wet and freeze-thaw durability. In general, UCS increased at first, but then it decreased to some degree with the increase in dry-wet and freeze-thaw cycles. The cycle number for peak UCS depended on the durability test types and SR content. The UCS values after seven dry-wet cycles or ten freeze-thaw cycles were higher than the initial values before cycles. The main products detected in SR-GGBS-QL solidified sludge were ettringite, hydroaluminite, and calcium silicate hydrate (C-S-H). In addition, some pollutants such as copper, arsenic, and chromium were stabilized. The weakening effect on the microstructure of the solidified sludge occurred after dry-wet or freeze-thaw cycles. However, the hydration reaction continued with the increase of dry-wet and freeze-thaw cycles, leading to an increase in the amount of hydration products (especially C-S-H) and compact microstructure. These contributed to high UCS values and good dry-wet and freeze-thaw durability. The strength and failure strain of solidified sludge still met the requirement of filling materials after dry-wet or freeze-thaw cycles.
13
Li, Sheng-Nan, Zhu Peng, Zhong-Hua Huang, Qiao Liang, Jie Liu et Wen-Quan Zhou. « Time-Dependent Deformation and Long-Term Strength of Carbonaceous Mudstone under Dry and Wet Cycles ». Sustainability 14, no 19 (23 septembre 2022) : 12044. http://dx.doi.org/10.3390/su141912044.
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Clarifying the time-dependent strength deterioration characteristics of carbonaceous mudstone under dry and wet cycles is of great significance to the design of expressway cut slopes. In this work, we conducted triaxial compression creep tests on carbonaceous mudstone specimens that had undergone different numbers of dry and wet cycles to investigate their creep properties. A function was established between the steady-state viscoplastic creep rate and axial compression. The threshold stress of the steady-state viscoplastic creep rate was assumed as the long-term strength, and the long-term strength deterioration law of carbonaceous mudstone under dry and wet cycles was studied. The results showed that the transient strain, viscoelastic creep, and viscoplastic creep of carbonaceous mudstone increased with the number of dry and wet cycles, and the creep failure stress and transient elasticity modulus decreased. Based on the steady-state viscoplastic creep rate method, the long-term strength of carbonaceous mudstone after n (n = 0, 3, 6, 9) dry and wet cycles was found to be 74.25%, 64.88%, 57.56%, and 53.16% of its uniaxial compression strength, respectively. Compared with the isochronous curve method and the transition creep method, the steady-state viscoplastic creep rate method can more accurately determine the long-term rock strength. The long-term strength of carbonaceous mudstone under dry and wet cycles decays exponentially, and the long-term strength decay rate during the first three dry and wet cycles is about 215 times the average decay rate.
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Bai, Yang, Wanjun Ye, Yuntao Wu et Yiqian Chen. « Multiscale Analysis of the Strength Deterioration of Loess under the Action of Drying and Wetting Cycles ». Advances in Materials Science and Engineering 2021 (2 avril 2021) : 1–12. http://dx.doi.org/10.1155/2021/6654815.
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To study the strength degradation mechanism of compacted loess during dry-wet cycles, 0–5 dry-wet cycles tests and many triaxial compression tests were carried out on loess with an optimal moisture content. During the dry-wet cycles, the loess samples were analyzed by nuclear magnetic resonance and scanning electron microscopy. Studies have shown that at the macro level, with increasing numbers of wet and dry cycles and increasing cycle amplitude, the cohesive force and internal friction angle of the loess decrease, and the shear strength of the loess deteriorates significantly. At the micro level, with the number of wet and dry cycles increasing, the connection between particles changes from surface-to-surface contacts to point-to-point or point-to-surface contacts. The edges and corners of the particles decrease, the roundness increases, the large pores gradually decrease, the small pores gradually increase, and the fractal dimension gradually increases. In terms of microscopic view, the NMR test shows that with increasing numbers of dry-wet cycles, the T2 peak curve increases, the curve width increases slightly, the peak area gradually increases, and the porosity increases. From the macroscopic, mesoscopic, and microscopic multiscale analysis, the structure of loess is degraded under the action of dry and wet cycles; the strength of the loess is degraded significantly after 0 to 3 cycles and then gradually stabilizes. These research results can provide a certain reference value for the management of loess collapse geological disasters in semiarid climates.
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Liu, Guangcheng, Xin Huang et Jianyong Pang. « The Uniaxial Creep Characteristics of Red Sandstone under Dry-Wet Cycles ». Advances in Civil Engineering 2020 (28 juillet 2020) : 1–13. http://dx.doi.org/10.1155/2020/8841773.
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Water is one of the most important factors that affect the long-term stability of geotechnical engineering structures. Rainfall often results in periodic changes in the water content in underground rock, which is subjected to alternating dry-wet cycles. In this paper, in order to study the short-term and long-term mechanical properties of red sandstone under these dry-wet cycles, a series of uniaxial compressive strength (UCS) tests and multistage creep tests have been carried out on specimens of red sandstone after being treated to different numbers of dry-wet cycles. A scanning electron microscope (SEM) was used to image the different groups of specimens. The test results have shown that the peak strength and the elastic modulus of the red sandstone decreased as the number of dry-wet cycles increased. It is worth noting that the first immersion of the specimens decreased their strength the most, and the negative logarithmic function was able to better reflect the peak strength of the red sandstone and the variation of its elastic modulus in relation to the number of dry-wet cycles. The results of the creep tests have shown that the instantaneous strain and creep strain of the sandstone increased significantly with the increase of the number of dry-wet cycles. A linear function and a negative logarithmic function can be used to describe the instantaneous strain and the creep strain, respectively. The creep duration of the red sandstone in its failure stage decreased with the increase of the number of dry-wet cycles, and the creep rate increased with the increase of the number of dry-wet cycles. Lastly, the failure modes of the red sandstone were observed; the results showed that the angle between the main crack and the axis of creep failure gradually increased with the increase of the number of dry-wet cycles and the angle of the internal friction and the cohesion decreased. In addition, the failure mode of the specimens changed from tensile failure to shear failure. The microstructure of the sandstone showed that the surface of the specimen changed from being compact to being loose, and the mineral particles in the specimen changed from being spherical to being flat and curly; this led to a decrease in the macroscopic mechanical parameters of the sandstone.
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Chen, Xuxin, Ping He et Zhe Qin. « Damage to the Microstructure and Strength of Altered Granite under Wet–Dry Cycles ». Symmetry 10, no 12 (4 décembre 2018) : 716. http://dx.doi.org/10.3390/sym10120716.
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This paper presents an analytical method for surrounding rocks in symmetrically shaped tunnels or roadways, with the symmetrical rise and fall of groundwater over a certain period. The influence of reservoir water level on wet–dry cycles were studied. The changes in the microstructure and strength of altered granite and its evolution were explored using mechanical tests and scanning electron microscopy (SEM). The results showed that: (1) the wet–dry cycles weakened the strength of altered granite. Furthermore, the uniaxial compressive strength, elastic modulus, cohesion, and internal friction angle decreased with the increase of the number of cycles, while the maximum reduction in these parameters reached 50.22%, 63.84%, 93.76%, and 53.90%, respectively. (2) The wet–dry cycles damaged the microstructure of altered granite. The SEM analysis showed that, under wet–dry cycles, the structure of altered granite changed from a smooth and integrated internal structure to the initiation, development, and expansion of pores and cracks. The porosity and fractal dimension of rock were determined using the SEM results. The degree of damage to altered granite under wet–dry cycles was quantitatively analyzed. (3) According to the rock mechanics strength tests and SEM and X-ray diffraction analyses, the damage mechanism of altered granite subjected to wet–dry cycles was discussed. The results provide the basis for a stability analysis of symmetrically shaped tunnels, especially symmetrical tunnels constructed in water-rich areas such as symmetric circular tunnels and symmetric horseshoe tunnels.
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Liu, Xinrong, Zijuan Wang, Yan Fu, Wen Yuan et Luli Miao. « Macro/Microtesting and Damage and Degradation of Sandstones under Dry-Wet Cycles ». Advances in Materials Science and Engineering 2016 (2016) : 1–16. http://dx.doi.org/10.1155/2016/7013032.
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In terms of the degradation of mechanical parameters of rock mass in the hydrofluctuation belt of a reservoir bank slope arising from rainfall and the reservoir level fluctuation, the moderately weathered sandstone in a side slope of the Three Gorges Reservoir Region is selected as a research object to carry out “drying-saturation-drying” tests for disks with two thicknesses (h=25 mm,h=50 mm) in different cycles; a spiral CT machine, an ultrasonic velocity meter, and a light Schmidt hammer are utilzed to conduct nondestructive testing on dry-wet cycles; through the Brazilian splitting test, the uniaxial tensile strength of “dry” and “saturated” sandstones under different dry-wet cycles is obtained. The research shows that, with the increase of the dry-wet circles (n), the longitudinal wave velocity and the rebound strength of sandstones are linearly decreased withn; the uniaxial tensile strength of sandstones and the mean CT number of cross sections are logarithmically decreased withn; the fitting equation of macro/micromechanical parameters and dry-wet cycles (n) of sandstones is raised, which is provided as a reference basis for the weathering process of sandstones under dry-wet cycles.
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Xuebing, Wang, et Guo Shengbo. « Influence of different curing conditions on water absorption of cement-based materials under dry and wet cycles ». Materials Research Express 9, no 9 (1 septembre 2022) : 095203. http://dx.doi.org/10.1088/2053-1591/ac8cd1.
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Abstract As the main structural material of a subway, the precast concrete segment is produced under the steam-curing condition, and frequently experienced dry–wet cycles environment. In this study, steam-curing and dry–wet cycling methods were used to simulate the water absorption process of cement-based materials under special circumstances. The results showed that the water absorption in cement-based materials decreased with an increase in the number of dry–wet cycles. Based on a micro-analysis, the proportion of large capillary pores (dimension >0.1 μm) in the steam-cured mortar increased during the water absorption process with the increase in the number of dry–wet cycles compared with the standard cured mortar. Through thermodynamic and kinetics analysis, the mechanism and model were calculated to explain the component transformation mechanism of cement-based materials under dry and wet cycles.
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Liu, Jianxun, Ning Li, Meirong Chen, Jianping Yang, Biao Long et Zhishen Wu. « Durability of basalt fiber-reinforced polymer bars in wet-dry cycles alkali-salt corrosion ». Science and Engineering of Composite Materials 26, no 1 (28 janvier 2019) : 43–52. http://dx.doi.org/10.1515/secm-2018-0030.
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AbstractBasalt fiber-reinforced polymer (BFRP) bars have been increasingly applied to offshore structures, which are subjected to seawater corrosion and wet-dry cycles during their service time. This study evaluated the alkali-salt resistance performance of BFRP bars with different resin matrix types under wet-dry cycles. The tensile and shear strength of BFRP bars were tested. As a comparison, experiments of BFRP bars under continuous immersion were also conducted. The mechanisms of the two different conditions were analyzed by scanning electron microscopy (SEM). A relationship was established between the degradations under continuous immersion and wet-dry cycling. The results demonstrated that the alkali-salt resistance of vinyl resin matrix BFRP bars was superior to that of epoxy resin matrix BFRP bars under wet-dry cycles. Furthermore, according to the data obtained under continuous immersion, a time shift factor for predicting the durability of BFRP bars under wet-dry cycles was proposed.
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Jiang, Ying-jun, Chen-yang Ni, Hong-wei Sha, Zong-hua Li et Lu-yao Cai. « Deterioration characteristics of cement-improved loess under dry–wet and freeze–thaw cycles ». PLOS ONE 16, no 7 (1 juillet 2021) : e0253199. http://dx.doi.org/10.1371/journal.pone.0253199.
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The effects of cement dosage, compaction coefficient, molding method (vertical vibration method and static pressure method), and dry–wet and freeze–thaw cycles on the mechanical strength of cement-improved loess (CIL) were studied to reveal its strength degradation law under dry–wet and freeze–thaw cycles. Results show that when using the vertical vibration molding method, the strength degradation effect of CIL can be improved by increasing the cement dosage and compaction coefficient; however, it is not obvious. Under the action of dry–wet cycle, damages, such as voids and cracks of CIL, develop continuously. Further, the strength deteriorates continuously and does not decrease after more than 15 dry–wet cycles. Therefore, the dry–wet cycle degradation system is selected by considering the most unfavorable conditions. In the process of freeze–thaw alternation, the pores and fissures of CIL develop and evolve continuously and the strength deteriorates continuously under the joint influence of water and low temperature. The strength tends to become stable after more than 12 freeze–thaw cycles. According to the safety principle, the deterioration coefficient of the freeze–thaw cycles is 0.3.
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Niu, Longlong, et Shiping Zhang. « Performance of Cracked Ultra-High-Performance Fiber-Reinforced Concrete Exposed to Dry-Wet Cycles of Chlorides ». Advances in Materials Science and Engineering 2021 (30 novembre 2021) : 1–11. http://dx.doi.org/10.1155/2021/4625972.
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This paper presents an experimental study on the performance of cracked ultra-high-performance fiber-reinforced concrete (UHPC) exposed to dry-wet cycles of 3.5% NaCl solution under the temperature of 60°C. The results show that the wider the crack, the higher the corrosion degree of steel fibers embedded in UHPC, and the deeper the chloride ion diffusion on both sides of the crack. With the increase of dry-wet cycles, the flexural strength of precracked UHPC first decreases and then increases, and the lowest flexural strength was observed in 60 dry-wet cycles. Although self-healing is hard to cease the corrosion of steel fibers, it can relieve the corrosion of steel fibers and improve the flexural strength exposed to 100 dry-wet cycles.
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Li, Xinming, Haoyang Zhang, Yanrui Guo, Song Yin et Kebin Ren. « Effect of Dry-Wet Cycles on Strength Properties and Microstructure of Lime-Metakaolin-Modified Soil ». Advances in Civil Engineering 2022 (29 septembre 2022) : 1–14. http://dx.doi.org/10.1155/2022/1296288.
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To explore the feasibility of replacing natural hydraulic lime (NHL) with lime-metakaolin (L-MK) in the restoration of soil sites, the samples of L-MK-modified silty sand (hereinafter L-MK-modified soil) underwent 0, 5, 10, and 15 dry-wet cycles and were then tested for mass loss, unconfined compressive strength, and splitting tensile strength. Some samples were tested using XRD, TG and SEM microscopic tests to study the strength mechanism for L-MK- and NHL-modified soil. The results showed that the mass loss ratios of the L-MK- and NHL-modified soils after 15 dry-wet cycles were within 2%. The compressive and tensile strengths of the L-MK-modified soil decreased with more dry-wet cycles, but the tensile strength decreased sharply initially and then to be stable after five dry-wet cycles. The attenuation characteristics were different obviously for the failure mode of compressive and tensile strength and the unevenness of the specimen caused by dry-wet cycles. The compressive and tensile strengths of L-MK-modified soil were significantly higher than those of NHL-modified soil after the same dry-wet cycle, and the decreased range of compressive and tensile strength was smaller than that of NHL-modified soil. The strength formation and attenuation characteristics of L-MK-modified soil are closely related to the influence of dry-wet cycles on the hydration products (e.g., CSH and C4AH13) generated by hydration reaction. The mix proportion of 6% L + 4% MK can effectively replace 8% and 10% NHL to protect soil sites.
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Sun, Wu, Bin Du et Qiangqiang Cheng. « Experimental Study of the Dynamic Mechanical Behavior and Degradation Mechanism of Red Sandstone in Acid Dry-Wet Cycles ». Geofluids 2023 (2 février 2023) : 1–10. http://dx.doi.org/10.1155/2023/5541567.
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In this paper, the slit Hopkinson pressure bar (SHPB) experiments were conducted to investigate the dynamic mechanical characteristics of red sandstone during acid dry-wet cycles. The appearance of the samples was evaluated using scanning electron microscopy, and the process of red sandstone degradation under acid dry-wet cycles was examined. The results reveal that, as compared to neutral solution, acid solution enhances the degree of degradation induced by dry-wet cycles in red sandstone. The dynamic compressive strength and elastic modulus of red sandstone steadily decline as the number of dry-wet cycles increases, and the lower the pH of solution, the greater the reduction. The mechanism of degradation of red sandstone during acid dry-wet cycles may be explained in two ways. First, the chemical interaction between the mineral components in the sample, such as cement and feldspar, and H+ in the acid solution has accelerated the formation of secondary pores and fractures, resulting in a decrease in the cementation capacity between mineral particles. Second, partial breakdown of the major mineral particles softens the mineral skeleton.
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Li, Lingling, Junping Shi et Jialiang Kou. « Experimental Study on Mechanical Properties of High-Ductility Concrete against Combined Sulfate Attack and Dry–Wet Cycles ». Materials 14, no 14 (19 juillet 2021) : 4035. http://dx.doi.org/10.3390/ma14144035.
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Concrete will deteriorate and damage under sulfate attack.In order to study the degradation characteristics of HDC under sulfate attack, the mechanical properties of high-ductility concrete (HDC) were investigated using the uniaxial compressive strength test of HDC specimens soaked in different concentrations of sulfate solution and subjected to different times of dry–wet cycles. The variations in the compressive strength, loss rate of compressive strength, and the max compressive strength under the action of sulfate attack and dry–wet cycles were analyzed. The analytical expressions of damage variables were given. SEM was used to observe the microstructure of the sample, and the microdamage mechanism of the HDC was explored. The deterioration of the HDC was found to be the result of the combined action of sulfate attack and dry–wet cycles and was caused by physical attack and chemical attack. PVA prevented the rapid development of deterioration. On the basis of the change of compressive strength, the damage variable was established to quantitatively describe the degree of damage to HDC. The experimental results showed that with the increase in the number of dry–wet cycles, the compressive strength of HDC generally increased first and then decreased. As the concentration of the sulfate solution increased, the loss rate of the compressive strength of HDC generally increased and the max compressive strength gradually decreased. With the increase inthe number of dry–wet cycles, HDC first showed self-compacting characteristics and then gradually became destroyed. Compared with ordinary concrete (OC), HDC is superior to OC in sulfate resistance and dry–wet cycles. This study provided a test basis for the engineering application of HDC in sulfate attack and dry–wet cycles environment.
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Olshansky, Yaniv, Robert A. Root et Jon Chorover. « Wet–dry cycles impact DOM retention in subsurface soils ». Biogeosciences 15, no 3 (9 février 2018) : 821–32. http://dx.doi.org/10.5194/bg-15-821-2018.
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Abstract. Transport and reactivity of carbon in the critical zone are highly controlled by reactions of dissolved organic matter (DOM) with subsurface soils, including adsorption, transformation and exchange. These reactions are dependent on frequent wet–dry cycles common to the unsaturated zone, particularly in semi-arid regions. To test for an effect of wet–dry cycles on DOM interaction and stabilization in subsoils, samples were collected from subsurface (Bw) horizons of an Entisol and an Alfisol from the Catalina-Jemez Critical Zone Observatory and sequentially reacted (four batch steps) with DOM extracted from the corresponding soil litter layers. Between each reaction step, soils either were allowed to air dry (wet–dry treatment) before introduction of the following DOM solution or were maintained under constant wetness (continually wet treatment). Microbial degradation was the dominant mechanism of DOM loss from solution for the Entisol subsoil, which had higher initial organic C content, whereas sorptive retention predominated in the lower C Alfisol subsoil. For a given soil, bulk dissolved organic C losses from solution were similar across treatments. However, a combination of Fourier transform infrared (FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopic analyses revealed that wet–dry treatments enhanced the interactions between carboxyl functional groups and soil particle surfaces. Scanning transmission X-ray microscopy (STXM) data suggested that cation bridging by Ca2+ was the primary mechanism for carboxyl association with soil surfaces. STXM data also showed that spatial fractionation of adsorbed OM on soil organo-mineral surfaces was diminished relative to what might be inferred from previously published observations pertaining to DOM fractionation on reaction with specimen mineral phases. This study provides direct evidence of the role of wet–dry cycles in affecting sorption reactions of DOM to a complex soil matrix. In the soil environment, where wet–dry cycles occur at different frequencies from site to site and along the soil profile, different interactions between DOM and soil surfaces are expected and need to be considered for the overall assessment of carbon dynamics.
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Huang, Liang, Wenbo Ma, Yujie Hou, Bo Wang et Jiahua Zhu. « Experimental Study on Mechanical Properties of Reinforced Soil Interface under Dry-Wet Cycle ». Advances in Civil Engineering 2021 (20 janvier 2021) : 1–15. http://dx.doi.org/10.1155/2021/8874655.
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The reinforced soil-retaining wall has been widely used in coastal projects, and the dry-wet cycles influence the mechanical properties of the reinforced soil interface. This study conducts macro-micro tests and selects four different water content samples of reinforced soil with five types of overburden pressure conditions and three sets of dry-wet cycles, with a total of 60 working conditions. The pull-out test was used to study the mechanical properties of the reinforced soil interface. The scanning electron microscope was used to observe the microscopic characterization of the particles under different working conditions. Through the analysis of the experimental results, we can draw the conclusion as follows. (1) The friction coefficient of the reinforced soil interface decreases with the increase of the number of dry and wet cycles. (2) The apparent cohesion of soil-reinforcement interface decreases with the increase of the number of dry-wet cycles. After 30 dry-wet cycles, the apparent cohesion of the soil-reinforcement interface with water content of 14% is the maximum 5.91 kPa. The variation law of cohesion derived from microstructure analysis conforms to the laws and conclusions obtained by the experiment. (3) The shear stress of the reinforced soil is linearly related to the normal stress, which is in accordance with Coulomb’s law.
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Zhang, Wei, Xue Zheng Chen, Peng Fei Yin, Zheng Kai Xu, Bing Han et Jia Wang. « EIS Study on the Deterioration Process of Organic Coatings under Immersion and Different Cyclic Wet-Dry Ratios ». Applied Mechanics and Materials 161 (mars 2012) : 58–66. http://dx.doi.org/10.4028/www.scientific.net/amm.161.58.
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Under immersed and we-dry cyclic conditions, the deterioration processes of the organic coating on carbon steel surface have been comparatively studied using electrochemical techniques. The wet-dry cycles were carried out by exposure to 4 h immersion and 4h dryness (4-4h cycles) and 12h immersion and 12h dryness (12-12h cycles) conditions, respectively. The immersion condition was carry out in a 3.5% NaCl solution and drying at 298K and 50% RH. According to the EIS characteristics, the entire deterioration processes under above three mentioned conditions can be divided into three main stages, consisting of the medium penetration, corrosion initiation and corrosion extension. Comparing with the immersed, the 4-4h wet-dry cycles greatly accelerated the entire deterioration process; especially during the corrosion initiation and the corrosion extension periods, leading the paint system lose its anti-corrosive performance in a short period. However, the 12-12h wet-dry cycles decelerated the entire deterioration process, prolonging the coatings anticorrosive ability. The acceleration mechanism of the coatings and underlying metal corrosion under wet-dry cycles was discussed based on the above results.
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Zhao, Yuan, Jiangteng Li et Gang Ma. « Experimental Study on the Damage and Degradation Characteristics of Red Sandstone after Dry and Wet Cycling by Low Magnetic Field Nuclear Magnetic Resonance (NMR) Technique ». Geofluids 2021 (12 avril 2021) : 1–8. http://dx.doi.org/10.1155/2021/8866028.
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To study the damage evolution of rocks under the action of wet and dry cycles, nuclear magnetic resonance (NMR) technology was used to test red sandstone under different times of wet and dry cycles. The T 2 spectral distribution curve, porosity, spectral peak area, and damage distribution curve of the rock were obtained, and the quantitative relationship between porosity, damage degree, and number of cycles was established. The results show that with the increase of the number of wet and dry cycles, the T 2 spectral curve of rock gradually moves to the right, but the moving amplitude gradually decreases. The porosity and spectral area increase with the increase of the number of wet and dry cycles, coupled with a declining growth rate, and the maximum increase in porosity is 18.789%. The damage degree of rock increase with the increase of the number of cycles, but with the continuous increase of the number of cycles, the damage rate decreases, and finally the damage degree of rock tends to be a constant value.
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Wang, Xin-gang, Bao-qin Lian, Jia-ding Wang, Wen-kai Feng et Tian-Feng Gu. « Creep damage properties of sandstone under dry-wet cycles ». Journal of Mountain Science 17, no 12 (12 novembre 2020) : 3112–22. http://dx.doi.org/10.1007/s11629-020-6284-z.
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Jablonowski, Nicolai David, Andreas Linden, Stephan Köppchen, Björn Thiele, Diana Hofmann et Peter Burauel. « Dry–wet cycles increase pesticide residue release from soil ». Environmental Toxicology and Chemistry 31, no 9 (27 juillet 2012) : 1941–47. http://dx.doi.org/10.1002/etc.1851.
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Pinto, Renata, Gabriele Weigelhofer, António Guerreiro Brito et Thomas Hein. « Effects of dry-wet cycles on nitrous oxide emissions in freshwater sediments : a synthesis ». PeerJ 9 (12 février 2021) : e10767. http://dx.doi.org/10.7717/peerj.10767.
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Background Sediments frequently exposed to dry-wet cycles are potential biogeochemical hotspots for greenhouse gas (GHG) emissions during dry, wet and transitional phases. While the effects of drying and rewetting on carbon fluxes have been studied extensively in terrestrial and aquatic systems, less is known about the effects of dry-wet cycles on N2O emissions from aquatic systems. As a notable part of lotic systems are temporary, and small lentic systems can substantially contribute to GHG emissions, dry-wet cycles in these ecosystems can play a major role on N2O emissions. Methodology This study compiles literature focusing on the effects of drying, rewetting, flooding, and water level fluctuations on N2O emissions and related biogeochemical processes in sediments of lentic and lotic ecosystems. Results N2O pulses were observed following sediment drying and rewetting events. Moreover, exposed sediments during dry phases can be active spots for N2O emissions. The general mechanisms behind N2O emissions during dry-wet cycles are comparable to those of soils and are mainly related to physical mechanisms and enhanced microbial processing in lotic and lentic systems. Physical processes driving N2O emissions are mainly regulated by water fluctuations in the sediment. The period of enhanced microbial activity is driven by increased nutrient availability. Higher processing rates and N2O fluxes have been mainly observed when nitrification and denitrification are coupled, under conditions largely determined by O2 availability. Conclusions The studies evidence the driving role of dry-wet cycles leading to temporarily high N2O emissions in sediments from a wide array of aquatic habitats. Peak fluxes appear to be of short duration, however, their relevance for global emission estimates as well as N2O emissions from dry inland waters has not been quantified. Future research should address the temporal development during drying-rewetting phases in more detail, capturing rapid flux changes at early stages, and further explore the functional impacts of the frequency and intensity of dry-wet cycles.
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Su, Xiao Ping, et Hao Yue Sun. « Estimating the Importance Degree of Influence Factors on Concrete Durability Based on Rough Set Theory ». Advanced Materials Research 988 (juillet 2014) : 191–94. http://dx.doi.org/10.4028/www.scientific.net/amr.988.191.
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Under the saline soil environment in the western area of Jilin Province, the concrete durability is affected by a lot of factors, which include wet-dry cycles, freeze-thaw cycles, wet-dry and freeze-thaw cycles, salt soaking time, salts concentration, fly-ash content, air content. These factors impact on the durability of concrete is uncertain, and there may be a problem of duplicate action, with some roughness characteristics. In this article, the rough set theory is used to analyze the degree that these seven factors affect the concrete durability, and to calculate weights. In this article, the loss rate of dynamic elasticity modulus is looked as the evaluation index of concrete durability. The results show that: the importance degrees of 7 factors influencing the loss rate of concrete dynamic elasticity modulus in order are: wet-dry and freeze-thaw cycles > wet-dry cycle > freeze-thaw cycles > multiple salts concentration > air content > long-term soak > fly-ash content.
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Zhao, Laishuan, Tiehai Wu, Shijie Yu et Baogui Rong. « Exploration on mechanical test method of improved loess under dry-wet cycles ». MATEC Web of Conferences 358 (2022) : 01031. http://dx.doi.org/10.1051/matecconf/202235801031.
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The stability of loess subgrade is affected by many factors. Dry-wet cycle is a common factor that causes damage to the strength of loess subgrade. In order to study the influence of dry-wet cycle on the stability of loess subgrade, reveal the mechanism of dry-wet cycle damage to the strength of loess subgrade It is necessary to sample the loess soil samples in this area, and perform compaction test, dry-wet cycle test, unconfined compression test and scanning electron microscope test on the soil sample to analyze the influence of dry-wet cycle on the strength and microstructure of loess soil. . In this way, the potential relationship between the microstructure and the strength of the soil can be obtained. The results show that the loess drywet cycle causes the loess's tensile strength and compressive strength to decrease with the increase of the number of dry-wet cycles. The dry-wet cycle effect gradually reduces the shear structural strength of the undisturbed loess and eventually disappears. Scanning electron microscope tests found that the humidification process caused slight movement of the particles, while the drying process resulted in permanent deformation of small pores.
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Aldaood, Abdulrahman, Amina Khalil, Ibrahim Alkiki et Madyan Alsaffar. « Volume Change and Cracks Behavior of Lime Treated Expansive Soils ». Academic Journal of Nawroz University 7, no 4 (21 décembre 2018) : 81. http://dx.doi.org/10.25007/ajnu.v7n4a274.
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This research work study the influence of cyclic wetting and drying on free swell potential of untreated and lime treated expansive clayey soils. Such a study is required to understand the behavior of these soils during wet-dry cycles. Two expansive soils (a polwhite bentonite and a kaolinite) with different plasticity indexes were used in this study. The soil samples were treated with different lime content in the order of (3, 5 and 7% by the dry weight of soil). The lime treated soil samples were cured at 20ºC for 28 and 180 days. The untreated and lime treated soil samples were subjected to four wet-dry cycles. Free swell potential and cracks propagation were studied during lime addition and wet-dry cycles. Results showed that, the free swell potential of untreated soil samples; in general; decreased with increasing wet-dry cycles, and all of the soil samples reached equilibrium after the second cycle. While the cracks propagation increased with these cycles, especially of bentonite soil samples. Larger cracks propagation has been observed in the bentonite soil samples. Lime addition enhanced the free swell potential values of the two expansive soils and there was a drastic decrease in free swelling potential and cracks propagation of these soils. The beneficial effect of lime treatment to control the swelling values was partly lost by the first wet–dry cycles, and the free swell potential increased at the subsequent cycles.
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Chard, Richard. « The wet dry cycle ». Equine Health 2015, no 21 (2 janvier 2015) : 14–17. http://dx.doi.org/10.12968/eqhe.2015.1.21.14.
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Du, Bin, Haibo Bai et Guangming Wu. « Dynamic Compression Properties and Deterioration of Red-Sandstone Subject to Cyclic Wet-Dry Treatment ». Advances in Civil Engineering 2019 (23 janvier 2019) : 1–10. http://dx.doi.org/10.1155/2019/1487156.
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Rock engineering is usually associated with impact loads induced by blasting, drilling, vibration, or earthquake. In the engineering fields of tunnelling, slopes, dams, and mining, rocks are always subjected to cyclic wet-dry caused by periodical variation in moisture. To study cyclic wet-dry effects on dynamic compression properties and deterioration of red-sandstone, physical tests and dynamic and static tests were conducted after 0, 5, 10, 15, and 20 wet-dry cycles. Changes in physical and mechanical parameters, including P-wave velocity, density, and static and dynamic compression strength, were determined. Deterioration of red-sandstone caused by wet-dry cycles was verified through physicomechanical parameters, and the microscopic features were scanned by SEM techniques. Experimental results showed that the dynamic compression strength increased with the loading rate, but decreased with the increase of wet-dry cycles. In terms of the loading rate, the decay function model was proposed to evaluate the long-term dynamic compression strength of red-sandstone against cyclic wet-dry action. Besides, the function of the loading rate was obtained. Parameters of two models, decay constant and half-life values, were measured accurately.
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Wang, Sheng, Feng Wang, Dawei Yin, Tianqi Jiang et Zhen Zhang. « Experimental Study on Mechanical Properties of Paste Backfill with Flue-Gas Desulphurisation Gypsum under Combined Action of Dry–Wet Cycles and Chloride Erosion ». Minerals 11, no 8 (15 août 2021) : 882. http://dx.doi.org/10.3390/min11080882.
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Flue-gas desulphurisation gypsum—a solid waste from power plants—can be used to prepare paste backfill for reducing costs. Most paste backfills are exposed to dry–wet cycles and chloride salt-rich water in mines. Therefore, the mechanical properties and damage mechanisms of paste backfill with desulphurised gypsum under the coupling action of erosion due to chloride with different concentrations and dry–wet cycles were investigated using methods such as visual observation, mass measurement, uniaxial compression, acoustic emission, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and field-emission scanning electron microscopy. With an increasing number of dry–wet cycles, the mass, elastic modulus, and strength of the paste backfill exhibited the trend of increasing first and then decreasing. The failure mechanism changed from mainly vertical fractures to the alternating development of vertical and horizontal fractures. The surface denudation effect of the specimens in a solution with a higher concentration was more severe under the same number of dry–wet cycles. In this study, the laws governing the mass change, strength change, degree of surface denudation, and failure pattern of desulphurised gypsum-filled specimens under different concentrations of chloride salt and different numbers of dry–wet cycles were derived.
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Zhang, Yan, Zicheng Wang, Guoshao Su, Zhekang Wu et Fengtao Liu. « Experimental Investigation on Influence of Acidic Dry-Wet Cycles on Karst Limestone Deterioration and Damage ». Geofluids 2022 (1 juillet 2022) : 1–12. http://dx.doi.org/10.1155/2022/8562226.
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This study is aimed at the problem of limestone deterioration and damage caused by the combination of acid rain and the dry-wet cycle in Guilin. Samples of limestone were taken to study the influence of acidic dry-wet cycles on limestone deterioration and damage. This was accomplished by performing nuclear magnetic resonance (NMR) measurements and inductively coupled plasma atomic emission spectrometer measurements on the limestone samples. The study found that with an increase in the number of cycles, the T 2 curve of the rock continuously shifts to the right, but the range of movement still decreases with pH increasing values. The T 2 spectrum area, rock porosity, porosity deterioration, mass loss rate, and water absorption rate all increase with an increase in the number of cycles, but the growth rate continues to decrease, and the increase is negatively correlated with pH. After the dry-wet cycles, the mass concentration of each element in the beaker is Ca, Mg, and Fe in order from high to low, and the mass concentration of each main element in the reaction solution increases with the increase in the number of acidic dry-wet cycles.
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Tang, Zhiyu, et Nianchun Deng. « Effect of Salt Solution on the Mechanical Behaviours of Geopolymer Concrete under Dry-Wet Cycles ». Advances in Materials Science and Engineering 2022 (7 juillet 2022) : 1–9. http://dx.doi.org/10.1155/2022/9120821.
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Seawater splashing and frequent rainfall in the coastal area will often cause the concrete members to be affected by dry-wet cycles. In order to investigate the effect of salt solution on the mechanical behaviours of geopolymer concrete under dry-wet cycles, a series of tests on erosion of geopolymer concrete by three different salt solutions were carried out by using the mass loss rate, compressive strength, erosion resistance coefficient, and elastic modulus. The results show that, with the increase of dry-wet cycles, the mass of the specimen increases slightly at 20 dry-wet cycles and then decreases gradually. Then, the stress-strain curve of geopolymer concrete can be divided into three stages: linear growth stage, deceleration growth stage, and slow decline stage, which correspond to the elastic deformation stage, elastic-plastic deformation stage, and crushing stage, respectively. The overall trend of the stress-strain curve is similar under different dry-wet cycles, and the peak stress decreases with the increase of dry-cycle. The relationship between stress and strain of geopolymer concrete samples with different salt solutions is similar, while their strength characteristics have changed obviously. Furthermore, with the increase of dry-wet cycles, the compressive strength and the relative elastic modulus of geopolymer concrete gradually decrease, which reflects that sulfate erosion will lead to the strength loss of geopolymer concrete, causing its internal damage, thus having adverse effects on it. Different salt solutions have the great influence on the mass loss rate, compressive strength, erosion resistance coefficient, and elastic modulus of geopolymer concrete. In detail, the mixed salt solution erosion results in the greatest damage to geopolymer concrete and accelerates the damage. Chloride salt solution erosion causes middle damage to geopolymer concrete. Compared with the other two salt solutions, sulfate solution erosion leads to the least damage to geopolymer concrete and then sulfate has a certain inhibitory effect on the damage of geopolymer concrete. In addition, based on the test results, the constitutive model considering dry-wet cycles damage of salt solution is proposed, and the correctness is verified. This study has a good guiding value for geopolymer concrete engineering in coastal areas.
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Zhao, Zhewei, Wenwei Li, Haiping Shi, Zhongyao Li, Jiahuan Li, Cheng Zhao et Peiqing Wang. « Strength of Coarse-Grained Soil Stabilized by Poly (Vinyl Alcohol) Solution and Silica Fume under Wet–Dry Cycles ». Polymers 14, no 17 (29 août 2022) : 3555. http://dx.doi.org/10.3390/polym14173555.
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To investigate an environmentally benign stabilizer for coarse-grained soil in southeast Tibet, poly (vinyl alcohol) (PVA) and silica fume were used to improve the geotechnical properties of coarse-grained soil. Unconfined compressive strength (UCS) and wet–dry cycle tests were conducted on prepared samples to evaluate the effect of the additive content and curing age on the strength and durability of coarse-grained soil. The results reveal that the UCS of the samples increased with the additive content of PVA solution and the curing age. The optimal value for the additive content of PVA solution and the curing age is 12% and 7 days, respectively. With the optimal PVA solution content, the PVA solution combined with silica fume stabilizer exhibited better reinforcement compared with pristine PVA. The UCS of the samples stabilized by PVA solution and silica fume increased depending on the curing age, and plateaued after 14 days. Samples with 12% PVA solution and 6% silica fume achieved a satisfactory UCS of 1543.17 kPa after curing for 28 days. As the number of wet–dry cycles increased, the UCS of the samples stabilized by the PVA solution and silica fume exhibited an upward trend during the first three wet–dry cycles, owing to the filling of pores by the gel produced by the silica fume, but began to decline as the number of wet–dry cycles increased. All samples retained a high UCS value after 10 wet-dry cycles compared with the samples that were not subjected to wet–dry cycles.
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Wu, Qing, Xuezhong Li, Jun Xu, Gang Wang, Wenhao Shi et Shilin Wang. « Size Distribution Model and Development Characteristics of Corrosion Pits in Concrete under Two Curing Methods ». Materials 12, no 11 (6 juin 2019) : 1846. http://dx.doi.org/10.3390/ma12111846.
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In this paper, the effect of chloride ions on the development of corrosion pits in different reinforced concrete under different environmental conditions is studied. A fitting model for the size distribution of pits in seawater and sea-sand concrete (SSC) under different curing modes is established, and time-dependent fractal features are examined. Under wet/dry chloride cycles, the weight loss rate and corrosion rate of steel bars are higher, and the number of corrosion pits appears to increase on a small scale within 60-day. A majority of the corrosion is metastable pitting, and we propose a model to describe the size distribution of pitting in different periods. The good agreement between the proposed model and the available data illustrates that the proposed model is reliable and accurate. Macroscopic pitting occurs first in wet/dry chloride cycles. With the increase of concrete age, the size distribution of pits under wet/dry chloride cycles is uneven, and the pit sizes in submerged concrete tend to be equal.
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Cai, Jian Jun, Feng Zhang, Wei Cui, Shou Shan Chen et Pu Lun Liu. « Concrete Strength and Deformation Property under Sea Water Erosion Environment ». Advanced Materials Research 446-449 (janvier 2012) : 2554–59. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.2554.
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In order to effectively assess the concrete strength and deformation property under sea water erosion environment, concrete stress and strain curve was researched with the number of wet and dry cycle of 0 times, 10 times , 20 times, 30 times, 40 times, 50 times and 60 times based on the large-scale static and dynamic stiffness servo test set. The stress - strain curves of concrete was tested for the lateral pressure 10.8MPa, 14.4MPa, and 18.8MPa at different dry-wet cycles, The failure modes and superficial cracking characteristics of specimens are reported at different dry-wet cycles. Concrete elastic modulus and compressive strength were researched. Based on concrete mechanical theory , the classic Kufer-Gerstle strength criteria of concrete was used, a large number of test samples of multivariate data were nonlinear regressed, a biaxial concrete strength criterion was established taking into account the stress ratio and the number of dry-wet cycles.
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Du, Bin, et Haibo Bai. « A Damage Constitutive Model of Red Sandstone under Coupling of Wet-Dry Cycles and Impact Load ». Shock and Vibration 2019 (9 mai 2019) : 1–12. http://dx.doi.org/10.1155/2019/7692424.
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In the engineering fields of mining, tunneling, slopes, and dams, rocks are usually subject to the coupling effect of impact load and wet-dry cycles. The deformation rule of rocks under the coupling effects is a symbolic mechanical property, which lays the foundation for the design and evaluation in the rock engineering. In this paper, the coupling damage was classified as mesodamage induced by wet-dry cycles and macrodamage induced by impact load, and the loading rate effect was considered as the load damage. Besides, a constitutive model of coupling damage was concluded based on Lemaitre’s strain equivalent assumption. Consequently, the validity of the model was verified by a series of dynamic compression tests of red sandstone. Results indicated that the proposed damage constitutive model can definitely describe the dynamic stress-strain curves of red sandstone after wet-dry cycles and impact load. The evolution of coupling damage curves showed that wet-dry cycle damage plays a dominant role in the elastic deformation stage, while the yield failure stage is controlled by the load damage in which the loading rate cannot be ignored. Parametric study was also performed to analyze the effect of parameters on dynamic stress-strain curves. The proposed mode has the simple and reliable operation with few parameters and can efficiently predict the long-term deformation behavior of rocks subject to multiple wet-dry cycles.
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Chen, Xuxin, Ping He, Zhe Qin, Jianye Li et Yanping Gong. « Statistical Damage Model of Altered Granite under Dry-Wet Cycles ». Symmetry 11, no 1 (2 janvier 2019) : 41. http://dx.doi.org/10.3390/sym11010041.
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This paper presents a new statistical damage constitutive model using symmetric normal distribution. The broken rock microbody obeyed symmetric normal distribution and the equivalent strain principle in damage mechanics. The uniaxial compression tests of samples subjected to dry-wet cycles were performed. The damage model was established using the equivalent strain principle and symmetric normal distribution. The damage variable was defined by the elastic modulus under various dry-wet cycles. Parameters of the damage constitutive model were identified using MATLAB software, and the proposed model is verified to be in good agreement with uniaxial compression test results. Fracturing of the rock microbody is well described by symmetric normal distribution, and the proposed statistical damage constitutive model has good adaptability to the uniaxial compression stress-strain curve.
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Malasri, Siripong, Mallory Harvey, Robert Moats, James Aflaki, Ali Pourhashemi, Griselda Matos Martinez et Patrick Held. « Effect of Wet-Dry Cycles on Compressive Strength and Impact Properties of New Softwood Pallets ». International Journal of Advanced Packaging Technology 1, no 1 (1 octobre 2013) : 15–21. http://dx.doi.org/10.23953/cloud.ijapt.2.
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Guan, Bo-wen, Jia-yu Wu, Tao Yang, An-hua Xu, Yan-ping Sheng et Hua-xin Chen. « Developing a Model for Chloride Ions Transport in Cement Concrete under Dynamic Flexural Loading and Dry-Wet Cycles ». Mathematical Problems in Engineering 2017 (2017) : 1–13. http://dx.doi.org/10.1155/2017/5760512.
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Chloride ions attack is the main factor leading to the degradation of concrete durability, while the diffusion process would be significantly aggravated under the dynamic flexural loading and dry-wet cycles. In this paper, the influence coefficients of dynamic flexural loading on chloride/water diffusion coefficients were established, based on the relationship between the dynamic flexural loading and the chloride ions diffusion coefficient of concrete. Based on the model of chloride ions transporting in dry-wet cycle environment, the transport model of chloride ions in concrete under the dynamic flexural loading and dry-wet cycles was established. The effects of different factors on the chloride ions transport law in concrete were analyzed through laboratory test. The results showed that the model was in good agreement with the experimental results. The theory and assumptions proposed applied in the model of chloride ions transport in concrete under the dynamic flexural loading and dry-wet cycles had certain rationality and scientificity.
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Lu, Chun-Hua, Hui Li et Rong-Gui Liu. « Chloride transport in cracked RC beams under dry–wet cycles ». Magazine of Concrete Research 69, no 9 (mai 2017) : 453–66. http://dx.doi.org/10.1680/jmacr.16.00364.
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Liang, Hongjun, Shan Li, Yiyan Lu et Ting Yang. « Reliability Study on FRP Composites Exposed to Wet-Dry Cycles ». Applied Sciences 8, no 6 (30 mai 2018) : 892. http://dx.doi.org/10.3390/app8060892.
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Mo, Z. K., D. Hou, C. Yao et C. B. Zhou. « Creep constitutive model of siltstone subjected to wet-dry cycles ». IOP Conference Series : Earth and Environmental Science 861, no 7 (1 octobre 2021) : 072094. http://dx.doi.org/10.1088/1755-1315/861/7/072094.
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Hu, Ming, Yuanxue Liu, Jianbo Ren, Yu Zhang et Linbo Song. « Temperature-induced slaking characteristics of mudstone during dry-wet cycles ». International Journal of Heat and Technology 35, no 2 (30 juin 2017) : 339–46. http://dx.doi.org/10.18280/ijht.350215.
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