The Experts below are selected from a list of 7518 Experts worldwide ranked by ideXlab platform
Caichu Xia - One of the best experts on this subject based on the ideXlab platform.
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Analytical solution of Frost Heaving force and stress distribution in cold region tunnels under non-axisymmetric stress and transversely isotropic Frost heave of surrounding rock
Cold Regions Science and Technology, 2020Co-Authors: Zhitao Lyu, Caichu Xia, Weiping LiuAbstract:Abstract Accurate evaluation of the Frost Heaving force and stress distribution plays an essential role in Frost damage prevention design of cold region tunnels. To ensure the safe operation of tunnels in cold regions and develop new practical method for their design, an analytical solution of Frost Heaving force and stress distribution in cold region tunnels under non-axisymmetric stress and transversely isotropic Frost heave of surrounding rock is established. The solution is of urgent demand because the tunnel sites with significant difference between horizontal and vertical initial ground stresses are frequently encountered. In analysis, the mechanical process is considered as two steps based on the linear superposition principle of elasticity theory. In step 1, the frozen zone freezes and expands without constraint first, and in step 2 the Frost Heaving displacement of the frozen zone is then inhibited by lining and unfrozen surrounding rock to reach a final balance state. The stress and displacement distributions of the above two steps are derived first, and then the solution of Frost Heaving force and stress is determined by boundary conditions. The analytical solution is verified with the existing solution under the axisymmetric stress condition. Furthermore, the stress distribution and the increment of stress in lining and surrounding rock induced by Frost heave are analyzed. Finally, the influence of the related factors on stress distribution is analyzed. Results show that the increment of the stress in lining and surrounding rock significantly vary with the lateral pressure coefficient and the anisotropic Frost heave coefficient, which demonstrates that the non-axisymmetric stress and the transversely isotropic Frost heave of surrounding rock have considerable impact on the stress distribution and should be considered.
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Analytical elasto-plastic solution of Frost Heaving force in cold region tunnels considering transversely isotropic Frost heave of surrounding rock
Cold Regions Science and Technology, 2019Co-Authors: Caichu Xia, Yuesong Wang, Jing LuoAbstract:Abstract Numerous cold region tunnels have been constructed in recent decades. To prevent Frost damage, problem of Frost Heaving force calculation is to be solved urgently. During the freezing process of cold region tunnels, temperature gradient occurs mainly in radial direction, whereas the temperature gradient in circumferential and axial directions is negligibly gentle. Hence, the surrounding rock of cold region tunnels freezes unidirectionally along the radial direction, which results in the transversely isotropic Frost heave of surrounding rock. Therefore, an analytical elasto-plastic solution of Frost Heaving force is proposed, in which an anisotropic Frost heave coefficient k is introduced to consider the transversely isotropic Frost heave. And the surrounding rock is considered as ideal elasto-plastic material conforming to Mohr-Coulomb yield criterion in the solution. Moreover, the method to determine the elastic or plastic state of the surrounding rock after Frost heave is proposed. For the condition that the frozen surrounding rock doesn't reach the plastic state, an elastic solution of Frost Heaving force considering the transversely isotropic Frost heave is also established. Then, the analytical elasto-plastic solution is verified with the existing solutions and a model test, and proved to be reasonable and applicable. Finally, the influence of the related factors, such as the Frost Heaving property (the anisotropic Frost heave coefficient and the volumetric Frost Heaving strain) of surrounding rock, the initial ground stress, and the mechanical parameters of surrounding rock on the Frost Heaving force and plastic zone radius is analyzed. Results show that as the anisotropic Frost heave coefficient k increases, the Frost Heaving force increases significantly, which demonstrates that the transversely isotropic Frost heave of surrounding rock has considerable impact on the Frost Heaving force and should be considered.
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Transversely isotropic Frost heave of saturated rock under unidirectional freezing condition and induced Frost Heaving force in cold region tunnels
Cold Regions Science and Technology, 2018Co-Authors: Caichu Xia, Jihui Huang, Xueying BaiAbstract:Abstract A series of freezing experiments has been conducted to investigate the Frost Heaving property of saturated rock under unidirectional freezing condition. Results show that the Frost heave parallel to the freezing direction is considerably larger than that perpendicular to the freezing direction, and the Frost heave is isotropic on the plane perpendicular to the freezing direction. Thus, the transversely isotropic Frost Heaving property of saturated rocks under unidirectional freezing condition is proposed, in which the plane perpendicular to the freezing direction is the plane of transverse isotropy and the line parallel to the freezing direction is the axis of transverse isotropy. In cold region tunnels, the inflow of cold air leads to the unidirectional freezing of the surrounding rock along the radial direction of tunnels. Hence, the Frost heave of the surrounding rock is transversely isotropic during the freezing process. The cylindrical surface constituted by the circumferential and axial directions is the surface of transverse isotropy and the line along the radial direction is the axis of transverse isotropy. Furthermore, an analytical solution for Frost Heaving force in cold region tunnels is derived, in which an anisotropic Frost heave coefficient k is used to consider the transversely isotropic Frost heave of the surrounding rock. The calculated results of the solution are compared with in situ measured data to prove the reasonability of the solution. Finally, the solution is used to optimize the design of the thermal insulation layer of a cold region tunnel.
Guoqing Zhou - One of the best experts on this subject based on the ideXlab platform.
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Frost heave and Frost Heaving induced pressure under various restraints and thermal gradients during the coupled thermal hydro processes in freezing soil
Bulletin of Engineering Geology and the Environment, 2019Co-Authors: Guoqing Zhou, Matthew R HallAbstract:Studies of Frost Heaving-induced pressure (FHIP) have been gaining increasing attention for applications using the freezing method to strengthen soils. This paper demonstrates a technique for measuring the FHIP when Heaving is constrained. A series of freezing tests were conducted under various restrained stiffnesses and associated with a thermal gradient. The evolution of Frost heave and the FHIP during coupled hydro–thermal interaction were examined. From this study, it was found that restraint prevents Frost heave by impeding formation of the ice lens. A thermal gradient is a necessary condition for both water flow and Frost heave, since pore water solidifies into ice and thus causes suction (negative pore water pressure) at the base of the ice lens. The pore structure and flow properties of freezing soil vary, since ice crystals progressively block the flow of water, whilst discontinuous ice lenses result in variation of water distributions. The increase of the FHIP appeared to cease when the ice pressure reached a maximum value, based on the microscopic analysis of equivalent water pressure. Moreover, the stable stage for the FHIP lagged behind the stabilization temperature. A macroscopic analysis of the different FHIPs under various different restraints was also carried out. It was found that increased restrained stiffness caused increased deformation and resulted in an increase of the observed FHIP. The coupled hydro–thermal behaviors analyzed in this study enable a better understanding of heat transfer and fluid flow in freezing granular media (soils).
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a separate ice based solution for Frost Heaving induced pressure during coupled thermal hydro mechanical processes in freezing soils
Cold Regions Science and Technology, 2018Co-Authors: Guoqing Zhou, Yang Zhou, Matthew R Hall, Xiaodong ZhaoAbstract:Abstract A Frost Heaving-induced pressure (FHIP) solution is developed in this paper based on the proposed separate-ice Frost heave model. A coupled thermal-hydro-mechanical (THM) model, describing the growth of a single ice lens under the restraint, is firstly constructed by considering the relationship between soil porosity and effective stress. The new ice lens formation criterion indicates that the formation of a new ice lens occurs when the disjoining pressure at the ice-water interface exceeds the summation of the external pressure and the critical pressure of soil strength. With consideration of the influence of the external pressure on the deformation of unfrozen soil, equivalent water pressure and critical separation pressure for ice segregation, the FHIP model is established by combining the growth model of a single ice lens and the formation criterion of new ice lenses. The freezing tests of Xuzhou (China) silty clay under different restraints were conducted to verify our numerical results, and the observed consistency thus validates the FHIP model. Our numerical results demonstrate the stress induced deformation of the soil column and indicate that the FHIP increases with the restrained stiffness. Particularly, with the decrease of the restrained stiffness, the FHIP decreases following an exponential function. The prediction of the FHIP using the proposed method improves our understanding of the characterized behavior of the FHIP under various restraints, and thus contributes to the analysis of the coupled thermal-hydro-mechanical processes in freezing soils.
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Frost-Heaving pressure in geotechnical engineering materials during freezing process
International Journal of Mining Science and Technology, 2018Co-Authors: Pingsheng Wang, Guoqing ZhouAbstract:Abstract Energy and resources including coal, oil, and gas are in demand all over the world. Because these resources near the earth’s surface have been exploited for many years, the extraction depth has increased. As mining shafts in the coal extraction process become deeper, especially in western China, an artificial freezing method is used and is concentrated in the fractured rock mass. The Frost-Heaving pressure (FHP) is directly related to the degree of damage of the fractured rock mass. This paper is focused on FHP during the freezing process, with emphasis on the Frost-Heaving phenomenon in engineering materials. A review of the Frost phenomenon in the geotechnical engineering literature indicates that: (1) During the soil freezing process, the ice content that is influenced by unfrozen water and the freezing rate are the determining factors of FHP; (2) During the freezing process of rock and other porous media, the resulting cracks should be considered because the FHP may damage the crack structure; (3) The FHP in a joint rock mass is analyzed by the joint deformation in field and experimental tests and can be simulated by the equivalent expansion method including water migration and joint deformation.
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Frost-Heaving pressure in geotechnical engineering materials during freezing process
Elsevier, 2018Co-Authors: Pingsheng Wang, Guoqing ZhouAbstract:Energy and resources including coal, oil, and gas are in demand all over the world. Because these resources near the earth’s surface have been exploited for many years, the extraction depth has increased. As mining shafts in the coal extraction process become deeper, especially in western China, an artificial freezing method is used and is concentrated in the fractured rock mass. The Frost-Heaving pressure (FHP) is directly related to the degree of damage of the fractured rock mass. This paper is focused on FHP during the freezing process, with emphasis on the Frost-Heaving phenomenon in engineering materials. A review of the Frost phenomenon in the geotechnical engineering literature indicates that: (1) During the soil freezing process, the ice content that is influenced by unfrozen water and the freezing rate are the determining factors of FHP; (2) During the freezing process of rock and other porous media, the resulting cracks should be considered because the FHP may damage the crack structure; (3) The FHP in a joint rock mass is analyzed by the joint deformation in field and experimental tests and can be simulated by the equivalent expansion method including water migration and joint deformation. Keywords: Frost Heaving pressure, Fractured rock, Low temperature, Freezing process, Water and ice conten
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on the Frost Heaving induced pressure response and its dropping power law behaviors of freezing soils under various restraints
Cold Regions Science and Technology, 2017Co-Authors: Guoqing Zhou, Xiaodong Zhao, Jianzhou Wang, Tao Wang, Zejin LaiAbstract:Abstract A one-dimensional Frost heave testing system is developed in this paper to investigate the Frost Heaving-induced pressure (FHIP) of Frost susceptible silty clay under various restraints and thermal gradients. The evolution of the Frost heave, the moisture migration, and the FHIP are examined from the conducted freezing tests, as well as the effects of restrained stiffness and thermal gradient. The development of Frost heave can be divided into four stages, i.e. the constant temperature stage, the rapid development stage, the transition development stage, and the stable stage. For tests with − 20 °C at the cold end of the tested samples, the ultimate heave is 5.88 mm, 4.86 mm and 4.31 mm, and the FHIP is 65.0 kPa, 71.1 kPa and 92.1 kPa, corresponding to the restrained stiffness of 11.06 kPa/mm, 14.62 kPa/mm and 21.36 kPa/mm, respectively. It can be found that the Frost heave decreases gradually with the restrained stiffness, whereas the FHIP shows an increase with the retrained stiffness. The results indicate that the FHIP drops rapidly with the relaxation of restraints, while this downward trend slows down as the Frost Heaving ratio increases. It is found that the FHIP decreases following an exponential function with the increase of Frost Heaving ratio, and the FHIP shows a dropping power-law behavior with an exponent of approximately 8/5.
Xiaolin Bian - One of the best experts on this subject based on the ideXlab platform.
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impact of sodium sulfate on soil Frost Heaving in an open system
Applied Clay Science, 2007Co-Authors: Hui Bing, Chengsong Yang, Yehui Shi, Shuping Zhao, Xiaolin BianAbstract:Abstract The existence of solutes and their redistribution during freezing have a deep influence on the process of soil freezing. We performed unidirectional freezing experiments in an open system with red clay collected at the Beiluhe test site along the Qinghai–Tibet Railway. The groundwater supply of the soil was simulated in the laboratory experiment by attaching a liquid replenishment system to the bottom of the sample container. In order to see the influence of the salt on the evolution of the sample during unidirectional freezing, two types of experiments were performed. (i) The soil samples were supplied with a sodium sulfate solute of 5% concentration, and (ii) only distilled water without any salty component was added. Based on the freezing temperature measurements of salty soil, migration of sodium sulfate solution towards a lower temperature zone during freezing 0 °C isotherm in the soil moved gently towards deeper layers, but Frost depth of the soil ascended slightly with time when the sample was constantly cooled. Compared to the distilled water replenishment, the amount of Frost-Heaving was smaller in the soil column with sodium sulfate solution replenishment. Based on the Frost depth curve, the solubility curve of the Na 2 SO 4 –H 2 O system and the amount of Frost Heaving and salt expansion in the soil column we have calculated the amount of Frost Heaving and salt expansion. In an early stage of the experiment deformation of the soil column was mainly caused by Frost Heaving, while in a later phase crystallization of the sodium sulfate played a lager role. This conclusion is confirmed by the results of the dry density measurement after the experiments.
Matthew R Hall - One of the best experts on this subject based on the ideXlab platform.
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Frost heave and Frost Heaving induced pressure under various restraints and thermal gradients during the coupled thermal hydro processes in freezing soil
Bulletin of Engineering Geology and the Environment, 2019Co-Authors: Guoqing Zhou, Matthew R HallAbstract:Studies of Frost Heaving-induced pressure (FHIP) have been gaining increasing attention for applications using the freezing method to strengthen soils. This paper demonstrates a technique for measuring the FHIP when Heaving is constrained. A series of freezing tests were conducted under various restrained stiffnesses and associated with a thermal gradient. The evolution of Frost heave and the FHIP during coupled hydro–thermal interaction were examined. From this study, it was found that restraint prevents Frost heave by impeding formation of the ice lens. A thermal gradient is a necessary condition for both water flow and Frost heave, since pore water solidifies into ice and thus causes suction (negative pore water pressure) at the base of the ice lens. The pore structure and flow properties of freezing soil vary, since ice crystals progressively block the flow of water, whilst discontinuous ice lenses result in variation of water distributions. The increase of the FHIP appeared to cease when the ice pressure reached a maximum value, based on the microscopic analysis of equivalent water pressure. Moreover, the stable stage for the FHIP lagged behind the stabilization temperature. A macroscopic analysis of the different FHIPs under various different restraints was also carried out. It was found that increased restrained stiffness caused increased deformation and resulted in an increase of the observed FHIP. The coupled hydro–thermal behaviors analyzed in this study enable a better understanding of heat transfer and fluid flow in freezing granular media (soils).
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a separate ice based solution for Frost Heaving induced pressure during coupled thermal hydro mechanical processes in freezing soils
Cold Regions Science and Technology, 2018Co-Authors: Guoqing Zhou, Yang Zhou, Matthew R Hall, Xiaodong ZhaoAbstract:Abstract A Frost Heaving-induced pressure (FHIP) solution is developed in this paper based on the proposed separate-ice Frost heave model. A coupled thermal-hydro-mechanical (THM) model, describing the growth of a single ice lens under the restraint, is firstly constructed by considering the relationship between soil porosity and effective stress. The new ice lens formation criterion indicates that the formation of a new ice lens occurs when the disjoining pressure at the ice-water interface exceeds the summation of the external pressure and the critical pressure of soil strength. With consideration of the influence of the external pressure on the deformation of unfrozen soil, equivalent water pressure and critical separation pressure for ice segregation, the FHIP model is established by combining the growth model of a single ice lens and the formation criterion of new ice lenses. The freezing tests of Xuzhou (China) silty clay under different restraints were conducted to verify our numerical results, and the observed consistency thus validates the FHIP model. Our numerical results demonstrate the stress induced deformation of the soil column and indicate that the FHIP increases with the restrained stiffness. Particularly, with the decrease of the restrained stiffness, the FHIP decreases following an exponential function. The prediction of the FHIP using the proposed method improves our understanding of the characterized behavior of the FHIP under various restraints, and thus contributes to the analysis of the coupled thermal-hydro-mechanical processes in freezing soils.
Hui Bing - One of the best experts on this subject based on the ideXlab platform.
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impact of sodium sulfate on soil Frost Heaving in an open system
Applied Clay Science, 2007Co-Authors: Hui Bing, Chengsong Yang, Yehui Shi, Shuping Zhao, Xiaolin BianAbstract:Abstract The existence of solutes and their redistribution during freezing have a deep influence on the process of soil freezing. We performed unidirectional freezing experiments in an open system with red clay collected at the Beiluhe test site along the Qinghai–Tibet Railway. The groundwater supply of the soil was simulated in the laboratory experiment by attaching a liquid replenishment system to the bottom of the sample container. In order to see the influence of the salt on the evolution of the sample during unidirectional freezing, two types of experiments were performed. (i) The soil samples were supplied with a sodium sulfate solute of 5% concentration, and (ii) only distilled water without any salty component was added. Based on the freezing temperature measurements of salty soil, migration of sodium sulfate solution towards a lower temperature zone during freezing 0 °C isotherm in the soil moved gently towards deeper layers, but Frost depth of the soil ascended slightly with time when the sample was constantly cooled. Compared to the distilled water replenishment, the amount of Frost-Heaving was smaller in the soil column with sodium sulfate solution replenishment. Based on the Frost depth curve, the solubility curve of the Na 2 SO 4 –H 2 O system and the amount of Frost Heaving and salt expansion in the soil column we have calculated the amount of Frost Heaving and salt expansion. In an early stage of the experiment deformation of the soil column was mainly caused by Frost Heaving, while in a later phase crystallization of the sodium sulfate played a lager role. This conclusion is confirmed by the results of the dry density measurement after the experiments.
