The Experts below are selected from a list of 1884 Experts worldwide ranked by ideXlab platform
Hao Zheng - One of the best experts on this subject based on the ideXlab platform.
-
the study of Frost Heave mechanism of high speed railway foundation by field monitored data and indoor verification experiment
Acta Geotechnica, 2020Co-Authors: Fujun Niu, Hao ZhengAbstract:Due to the rigid deformation limit of high-speed railways, the anti-Frost Heave design has become a critical concern in seasonally frozen regions. In this study, the authors explained the Frost Heave mitigation techniques adopted for the high-speed railway between Harbin and Dalian in northeast China and then presented the thermal, deformation, and water content data monitored on the Gongzhuling test site. According to these data, the authors proposed the possible Frost Heave mechanisms of the high-speed railway foundation. The foundation is composed of well-graded gravel with cement and A/B group fill, which are treated as non-Frost-susceptible materials in general. Based on the monitored data, the authors found that the surface layer (0–0.5 m) contributed most to the total Frost Heave and this might be caused by local water accumulation inside the foundation (0.6–1.2 m). In order to demonstrate the Frost Heave ability of these “non-Frost-susceptible” materials, the authors conducted an indoor Frost Heave test with a mixture of gravel and 3% Kaolinite clay. Through this experiment, it was demonstrated that, with sufficient water supply, gravel with a limited amount of fine material can produce significant Frost Heave. Accordingly, we can conclude that the accumulated water inside high-speed railway foundation causes the Frost Heave deformation. Therefore, the treatment of the water accumulation within the fills needs to be considered for Frost Heave elimination or prevention.
-
delamination Frost Heave in embankment of high speed railway in high altitude and seasonal frozen region
Cold Regions Science and Technology, 2018Co-Authors: Jing Luo, Fujun Niu, Zhanju Lin, Hao Zheng, Z J ShaoAbstract:Abstract The Lanzhou-Xinjiang high-speed railway is the first and the longest high-speed railway built in the high altitude and seasonally frozen areas in the North-west China. Frost Heave is a basic problem need to be studied and prevented for the safe operation of the railway. In this paper, Frost Heave was monitored in four sections along the railway from 2015 to 2017. The result show that the largest Frost Heave occurs in the middle layer (0.5–1.5 m) with the maximum Frost Heave ratio of 2.52%. However the coarse filling material of the layer is considered to be unsusceptible to Frost Heave. In laboratory, grain size tests and Frost Heave tests were conducted, showing that there exists an increasingly linear relationship between the fine content (size smaller than 0.25 mm, P0.25) and the Frost Heave ratio. However, P0.25 is suggested to be less than 11.3%. The monitored results also show that the frozen depth increases as an exponential function of time and the maximum frozen depth in embankment ranges from 3.0–3.2 m, while in the natural frozen depth, it was only 1.8 m, recorded in 2016–2017. The increased frozen depth might promote the development of Frost Heave, which was observed at three layers in different depths (0–0.5 m, 0.5–1.5 m, and 1.5–2.7 m), along with the variations of the moisture content and the ground temperature. For a few study results can be refereed, the Frost Heave characteristic of embankment filled with coarse-grained soil, and the relationships among of the ground temperature, water content, P0.25 content and Frost Heave amount, can provide a better understanding of the Frost Heave mechanism of high-speed railway embankment, so that to benefit high speed railway designing in high altitude and seasonally frozen regions.
-
experimental measurement and numerical simulation of Frost Heave in saturated coarse grained soil
Cold Regions Science and Technology, 2017Co-Authors: Fujun Niu, Zhanju Lin, Hao Zheng, Satoshi Akagawa, Jing LuoAbstract:Abstract A series of 1-D freezing experiments were conducted to simulate Frost Heave in saturated coarse-grained soil (CGS) with variable fines content. Visible Frost Heave occurred in CGS that contained a considerable fraction of fines when supplied by an external water source. Near the beginning of the experiments, a small amount of water was expelled, likely due to consolidation of the thawed portion of the sample. As time elapsed, the total amount of Frost Heave was proportional to the intake of water. Furthermore, Frost Heave increased linearly as the fines content increased. At higher fines content, Frost Heave occurred mainly due to water migration and segregated ice lensing. Finally, a simple finite element model that combined thermal and mechanical analyses based on Takashi's equation was developed. The model accurately reproduced experimental results and therefore can be used to simulate and predict Frost Heave in CGS.
-
application of practical one dimensional Frost Heave estimation method in two dimensional situation
Soils and Foundations, 2016Co-Authors: Fujun Niu, Hao Zheng, Shunji Kanie, Satoshi AkagawaAbstract:Abstract Most of the presently available practical Frost Heave prediction methods were derived from and for one-dimensional (1D) situations. However, the real desire of engineers is a multi-dimensional Frost Heave analysis. It is convenient to simply accumulate numerous experimental data on original 1D practical methods and then expand them for multi-dimensional applications. However, when such equations are applied to multi-dimensional situations, the first issue encountered is how to deal with the distribution of Frost Heave. To solve this issue, the authors propose one simple, but effective, method for allocating the Frost Heave ratio in multi-dimensional spaces. Takashi׳s equation is taken as an example to demonstrate this proposed distribution method. The equation was originally derived from 1D indoor Frost Heave experiments. It can predict the Frost Heave ratio in the freezing direction based on the freezing rate and the constraining stress. To obtain these two factors, thermal and mechanical analyses are combined together. With respect to the heat transfer process, the latent heat produced by the phase change of water is carefully evaluated by the equivalent heat capacity method. Concerning the distribution of the Frost Heave ratio, anisotropic parameter β is proposed to assign the Frost Heave ratio in the freezing direction and its transverse direction. By adjusting the value of β, the simulation results can very closely reflect the situation in reality. In addition, the authors discuss the relationship between Frost Heave and anisotropic parameter β in detail. Based on this assumption, the results of indoor Frost Heave tests and a large-scale field experiment are illustrated to verify this method, which simultaneously provides valuable examples for a multi-dimensional Frost Heave evaluation.
-
combined thermal hydraulic mechanical Frost Heave model based on takashi s equation
Journal of Cold Regions Engineering, 2015Co-Authors: Hao Zheng, Shunji KanieAbstract:AbstractThe purpose of this study is to establish a numerical simulation model that addresses the combined thermal-hydraulic-mechanical process of Frost Heave. Of the several practical Frost Heave estimation theories, the authors adopt Takashi’s equation, which has been successfully applied to one-dimensional Frost Heave estimation. In this paper, Takashi’s equation is used to assess the Frost Heave ratio during freezing. Takashi’s equation is expanded for a two-dimensional evaluation by introducing an anisotropic parameter to distribute the Frost Heave ratio in different directions. This model couples Fourier’s law for heat transfer and Darcy’s law for unfrozen water flow. Latent heat is seriously evaluated by equivalent heat capacity method. For the thermal and hydraulic processes, this model considers temperature- and pressure-dependent hydraulic conductivity by an empirical equation. Both saturated and unsaturated conditions are addressed in this model. A finite-element method is adopted, and the time...
Fujun Niu - One of the best experts on this subject based on the ideXlab platform.
-
the study of Frost Heave mechanism of high speed railway foundation by field monitored data and indoor verification experiment
Acta Geotechnica, 2020Co-Authors: Fujun Niu, Hao ZhengAbstract:Due to the rigid deformation limit of high-speed railways, the anti-Frost Heave design has become a critical concern in seasonally frozen regions. In this study, the authors explained the Frost Heave mitigation techniques adopted for the high-speed railway between Harbin and Dalian in northeast China and then presented the thermal, deformation, and water content data monitored on the Gongzhuling test site. According to these data, the authors proposed the possible Frost Heave mechanisms of the high-speed railway foundation. The foundation is composed of well-graded gravel with cement and A/B group fill, which are treated as non-Frost-susceptible materials in general. Based on the monitored data, the authors found that the surface layer (0–0.5 m) contributed most to the total Frost Heave and this might be caused by local water accumulation inside the foundation (0.6–1.2 m). In order to demonstrate the Frost Heave ability of these “non-Frost-susceptible” materials, the authors conducted an indoor Frost Heave test with a mixture of gravel and 3% Kaolinite clay. Through this experiment, it was demonstrated that, with sufficient water supply, gravel with a limited amount of fine material can produce significant Frost Heave. Accordingly, we can conclude that the accumulated water inside high-speed railway foundation causes the Frost Heave deformation. Therefore, the treatment of the water accumulation within the fills needs to be considered for Frost Heave elimination or prevention.
-
Comparing Frost Heave characteristics in cut and embankment sections along a high-speed railway in seasonally frozen ground of Northeast China
Cold Regions Science and Technology, 2020Co-Authors: Qi Miao, Jing Luo, Fujun Niu, Zhanju Lin, Minghao LiuAbstract:Abstract The Harbin–Dalian Passenger Dedicated Line (HDPDL) is the first high-speed railway in deep seasonally frozen ground in China. Frost Heave is among the most difficult problems in roadbed deformation control in such area. In this study, the ground temperatures and Frost Heave in a road cut section (K865) and an embankment section (K866) along the HDPDL were analyzed based on monitoring data in situ. From 2012 to 2018, the maximum Frost Heave in the cut section ranged from 4.52 mm to 9.18 mm, while in the embankment section this value ranged from 1.86 mm to 5.28 mm. The data clearly show that Frost Heave in the cut section was much more serious than that in the embankment section, although the frozen depth of the road cut was approximately 20 cm shallower than that of the embankment. The Frost Heave ratios of the roadbed filling materials in the well-graded gravel layer (0–0.5 m), non-Frost susceptibility A/B group fill layer (0.5–1.5 m), and A/B group layer (1.5–2.7 m) were 1.20%, 0.14%, and 0.08% on average in the cut section and generally higher than 0.63%, 0.04%, and 0.02% in the embankment over six freezing seasons, respectively. The investigation of Frost Heave in different soil layers at 24 monitoring sites indicated that most Frost Heave occurred in the top well-graded gravel layer (0–0.5 m), account for averagely 66% of the total deformation. The Frost Heave of the subgrade along the HDPDL mainly developed during the early period of each freezing season and an abrupt increase typically occurred during the initial period of the thawing process.
-
delamination Frost Heave in embankment of high speed railway in high altitude and seasonal frozen region
Cold Regions Science and Technology, 2018Co-Authors: Jing Luo, Fujun Niu, Zhanju Lin, Hao Zheng, Z J ShaoAbstract:Abstract The Lanzhou-Xinjiang high-speed railway is the first and the longest high-speed railway built in the high altitude and seasonally frozen areas in the North-west China. Frost Heave is a basic problem need to be studied and prevented for the safe operation of the railway. In this paper, Frost Heave was monitored in four sections along the railway from 2015 to 2017. The result show that the largest Frost Heave occurs in the middle layer (0.5–1.5 m) with the maximum Frost Heave ratio of 2.52%. However the coarse filling material of the layer is considered to be unsusceptible to Frost Heave. In laboratory, grain size tests and Frost Heave tests were conducted, showing that there exists an increasingly linear relationship between the fine content (size smaller than 0.25 mm, P0.25) and the Frost Heave ratio. However, P0.25 is suggested to be less than 11.3%. The monitored results also show that the frozen depth increases as an exponential function of time and the maximum frozen depth in embankment ranges from 3.0–3.2 m, while in the natural frozen depth, it was only 1.8 m, recorded in 2016–2017. The increased frozen depth might promote the development of Frost Heave, which was observed at three layers in different depths (0–0.5 m, 0.5–1.5 m, and 1.5–2.7 m), along with the variations of the moisture content and the ground temperature. For a few study results can be refereed, the Frost Heave characteristic of embankment filled with coarse-grained soil, and the relationships among of the ground temperature, water content, P0.25 content and Frost Heave amount, can provide a better understanding of the Frost Heave mechanism of high-speed railway embankment, so that to benefit high speed railway designing in high altitude and seasonally frozen regions.
-
characteristics and controlling factors of Frost Heave in high speed railway subgrade northwest china
Cold Regions Science and Technology, 2018Co-Authors: Zhanju Lin, Jing Luo, Fujun Niu, Minghao Liu, Zhujie ShaoAbstract:Abstract Frost-Heave of the subgrade significantly influences the stability of transportation infrastructure. In particular, small amounts of Frost Heave in coarse-grained subgrade fill may pose challenges to the safe operation of high-speed railway lines in cold regions. In this study, Frost Heave, ground temperatures, and soil moisture contents were examined at 15 test sections along Lanzhou-Xinjiang high-speed railway (LXHR), and the factors controlling the observed Heave are discussed. The development of Frost Heave in three subgrade layers (0–0.5, 0.5–1.5, and 1.5–2.7 m depth) was examined at each section over two freezing seasons (October 2015 to September 2017). The Frost depth in the subgrade reached 220–400 cm, significantly deeper than in surrounding natural ground. The Frost penetrated 2.3 m of A/B group fill, a special fill material for high-speed railways. The Frost Heave in some sections is greater than the allowable total deformation limit of 19 mm. Most of the total Frost Heave (40–50%) occurred in the 50 cm thick subgrade surface layer. Residual deformation developed over the two years, which has likely resulted in increased porosity and decreased compaction and strength. Frost heaving is mainly controlled by supplies of water from the surface, from below, and laterally from adjacent ground, and the fines content of the material. The data presented provide valuable information on the construction and performance of high-speed railways in regions with seasonally-frozen ground.
-
experimental measurement and numerical simulation of Frost Heave in saturated coarse grained soil
Cold Regions Science and Technology, 2017Co-Authors: Fujun Niu, Zhanju Lin, Hao Zheng, Satoshi Akagawa, Jing LuoAbstract:Abstract A series of 1-D freezing experiments were conducted to simulate Frost Heave in saturated coarse-grained soil (CGS) with variable fines content. Visible Frost Heave occurred in CGS that contained a considerable fraction of fines when supplied by an external water source. Near the beginning of the experiments, a small amount of water was expelled, likely due to consolidation of the thawed portion of the sample. As time elapsed, the total amount of Frost Heave was proportional to the intake of water. Furthermore, Frost Heave increased linearly as the fines content increased. At higher fines content, Frost Heave occurred mainly due to water migration and segregated ice lensing. Finally, a simple finite element model that combined thermal and mechanical analyses based on Takashi's equation was developed. The model accurately reproduced experimental results and therefore can be used to simulate and predict Frost Heave in CGS.
Mingyi Zhang - One of the best experts on this subject based on the ideXlab platform.
-
a generalized model for calculating the thermal conductivity of freezing soils based on soil components and Frost Heave
International Journal of Heat and Mass Transfer, 2020Co-Authors: Mingyi Zhang, Yuanming Lai, Wansheng Pei, Zhilang YouAbstract:Abstract Thermal conductivity of freezing soils is an important parameter for the geotechnical engineering in cold regions. During a freezing process, unfrozen water freezes into ice. It changes soil components and induces Frost Heave, which will significantly increase the thermal conductivity of freezing soils. This study presents a generalized model for calculating the thermal conductivity of freezing soils with a consideration of soil components and Frost Heave. The generalized model for freezing soils was developed by different connections (e.g. series connection and parallel connection) between soil pores and solid grain and between unfrozen water and ice in the pores. This model was a function of unfrozen water content, Frost Heave, porosity, and initial water content. The proposed model was verified by measured data of eight silty clay samples with different dry densities and initial water contents. Results show that the calculated thermal conductivities agree well with measured data.
-
investigation on Frost Heave of saturated unsaturated soils
Acta Geotechnica, 2020Co-Authors: Ruiqiang Bai, Yuanming Lai, Wansheng Pei, Mingyi ZhangAbstract:Frost Heave is a process of coupled heat–water–mechanics, which refers to heat transfer, water migration, water–ice phase change, deformation, etc. The mechanism of the Frost Heave for saturated–unsaturated soils was investigated to establish a Frost Heave model. As the freezing continues, for saturated soils, because all pores are filled with pore water, the total increased volume due to water migration and water crystallization will separate soil particles and induce Frost Heave. For unsaturated soils, because of the existence of unsaturated pores, volume expansion generates by water and vapor migration and water–ice transition will firstly fill into the unsaturated pores until a critical state is reached. After that, further increased volume will separate soil particles and induce Frost Heave. Therefore, effective strain ratio was introduced to establish the relationship between Frost Heave strain of unsaturated soils and the fields of moisture and temperature. Tests were carried out for silty soil. Then, based on the inverse theory, a simplified criterion was proposed to determine the effective strain ratio, and the effective strain ratio was back-calculated according to the test results. Finally, an innovative universal Frost Heave model for saturated–unsaturated soils was proposed.
-
centrifuge and numerical modeling of the Frost Heave mechanism of a cold region canal
Acta Geotechnica, 2019Co-Authors: Yuanming Lai, Mingyi Zhang, Wansheng Pei, Chen ZhangAbstract:In cold regions, frozen soil is common and causes various forms of Frost damage to engineering projects, particularly canals constructed in seasonally frozen ground. The freezing and Frost Heave processes are complicated, involving heat transfer, water migration, water–ice phase change, ice accumulation and Frost Heave deformation. To study the Frost Heave mechanism of cold-region canals, a centrifuge model of a canal in a freezing environment was constructed and used to simulate canal temperature, water and deformation changes. The experimental and numerical results show that the canal temperature decreases rapidly, forming a substantial temperature gradient in the ground. Driven by the temperature gradient, a portion of the pore water migrates, while other pore water in the freezing zone becomes ice. These phenomena are responsible for the Frost Heave deformation of the canal model. Generally, the vertical displacement at the top of the canal and the horizontal deformation in the middle-low part of the canal slope are larger than those in other zones, and Frost damages occur more easily in these zones. Therefore, to ensure safe operation, these zones should be closely monitored. This study is expected to help the engineer understand the Frost Heave mechanism of cold-region canals and to design a scientific anti-Frost canal. Additionally, the centrifuge and numerical models and results in this study may serve as references for further research.
-
experimental study of the hydro thermal characteristics and Frost Heave behavior of a saturated silt within a closed freezing system
Applied Thermal Engineering, 2018Co-Authors: Xiyin Zhang, Mingyi Zhang, Wansheng PeiAbstract:Abstract Frost Heave behavior during soil freezing process is an important issue of concern in cold regions, which is influenced by the hydro-thermal characteristics including the freezing point and water migration. The Frost Heave is caused by the freeze of water from different sources, i.e. pristine water, migrated water or both; however, it is difficult to identify the contributions of the different water sources to the Frost Heave, especially for a closed freezing system. Therefore, the calculation method to evaluate the Frost Heave induced by different water sources still need to be developed. Definitely, freezing experiments under controlled laboratory conditions can help to give a detailed description of the soil freezing process. Therefore, a large-scale one-directional freezing experiment within a closed system was carried out to investigate the hydro-thermal characteristics and Frost Heave behavior of a saturated silt. The research results showed the effect of the hydro-thermal behavior on the Frost Heave of the silt within a closed freezing system, and a calculation method was presented to evaluate the Frost Heaves from pristine water and migrated water, respectively.
-
effect of hydro thermal behavior on the Frost Heave of a saturated silty clay under different applied pressures
Applied Thermal Engineering, 2017Co-Authors: Xiyin Zhang, Mingyi Zhang, Wansheng Pei, Zhongrui YanAbstract:Abstract Civil engineering buildings are often damaged by Frost Heave of ground soils in cold regions. The hydro-thermal behavior is a key factor in determining Frost Heave of soils during freezing process. Moreover, the Frost Heave is also strongly affected by overburden pressure and external water source. Here, a series of one-directional freezing experiments with a water supply under different applied pressures were carried out to study the effect of hydro-thermal behavior on the Frost Heave of a saturated silty clay. Four different pressures were applied on the top of each soil sample, respectively, i.e. 50, 150, 300 and 500 kPa. The experimental results indicate that the Frost Heave of the supplied water is the main component of the total deformation for each soil sample with a water supply. However, the increased applied pressure can restrict water migration, and reduce Frost Heave during soil freezing process. Furthermore, for the saturated silty clay under different applied pressures, only when the advance rate of the freezing front drops to a critical value, the water intake begins. The start time of the water intake is also delayed with the increased applied pressure. Besides, the shut-off pressure of the saturated silty clay, at which no water flow into or out of the soil sample, is obtained based on the relationship between the critical advance rate of freezing front and the applied pressure.
Wansheng Pei - One of the best experts on this subject based on the ideXlab platform.
-
a generalized model for calculating the thermal conductivity of freezing soils based on soil components and Frost Heave
International Journal of Heat and Mass Transfer, 2020Co-Authors: Mingyi Zhang, Yuanming Lai, Wansheng Pei, Zhilang YouAbstract:Abstract Thermal conductivity of freezing soils is an important parameter for the geotechnical engineering in cold regions. During a freezing process, unfrozen water freezes into ice. It changes soil components and induces Frost Heave, which will significantly increase the thermal conductivity of freezing soils. This study presents a generalized model for calculating the thermal conductivity of freezing soils with a consideration of soil components and Frost Heave. The generalized model for freezing soils was developed by different connections (e.g. series connection and parallel connection) between soil pores and solid grain and between unfrozen water and ice in the pores. This model was a function of unfrozen water content, Frost Heave, porosity, and initial water content. The proposed model was verified by measured data of eight silty clay samples with different dry densities and initial water contents. Results show that the calculated thermal conductivities agree well with measured data.
-
investigation on Frost Heave of saturated unsaturated soils
Acta Geotechnica, 2020Co-Authors: Ruiqiang Bai, Yuanming Lai, Wansheng Pei, Mingyi ZhangAbstract:Frost Heave is a process of coupled heat–water–mechanics, which refers to heat transfer, water migration, water–ice phase change, deformation, etc. The mechanism of the Frost Heave for saturated–unsaturated soils was investigated to establish a Frost Heave model. As the freezing continues, for saturated soils, because all pores are filled with pore water, the total increased volume due to water migration and water crystallization will separate soil particles and induce Frost Heave. For unsaturated soils, because of the existence of unsaturated pores, volume expansion generates by water and vapor migration and water–ice transition will firstly fill into the unsaturated pores until a critical state is reached. After that, further increased volume will separate soil particles and induce Frost Heave. Therefore, effective strain ratio was introduced to establish the relationship between Frost Heave strain of unsaturated soils and the fields of moisture and temperature. Tests were carried out for silty soil. Then, based on the inverse theory, a simplified criterion was proposed to determine the effective strain ratio, and the effective strain ratio was back-calculated according to the test results. Finally, an innovative universal Frost Heave model for saturated–unsaturated soils was proposed.
-
centrifuge and numerical modeling of the Frost Heave mechanism of a cold region canal
Acta Geotechnica, 2019Co-Authors: Yuanming Lai, Mingyi Zhang, Wansheng Pei, Chen ZhangAbstract:In cold regions, frozen soil is common and causes various forms of Frost damage to engineering projects, particularly canals constructed in seasonally frozen ground. The freezing and Frost Heave processes are complicated, involving heat transfer, water migration, water–ice phase change, ice accumulation and Frost Heave deformation. To study the Frost Heave mechanism of cold-region canals, a centrifuge model of a canal in a freezing environment was constructed and used to simulate canal temperature, water and deformation changes. The experimental and numerical results show that the canal temperature decreases rapidly, forming a substantial temperature gradient in the ground. Driven by the temperature gradient, a portion of the pore water migrates, while other pore water in the freezing zone becomes ice. These phenomena are responsible for the Frost Heave deformation of the canal model. Generally, the vertical displacement at the top of the canal and the horizontal deformation in the middle-low part of the canal slope are larger than those in other zones, and Frost damages occur more easily in these zones. Therefore, to ensure safe operation, these zones should be closely monitored. This study is expected to help the engineer understand the Frost Heave mechanism of cold-region canals and to design a scientific anti-Frost canal. Additionally, the centrifuge and numerical models and results in this study may serve as references for further research.
-
experimental study of the hydro thermal characteristics and Frost Heave behavior of a saturated silt within a closed freezing system
Applied Thermal Engineering, 2018Co-Authors: Xiyin Zhang, Mingyi Zhang, Wansheng PeiAbstract:Abstract Frost Heave behavior during soil freezing process is an important issue of concern in cold regions, which is influenced by the hydro-thermal characteristics including the freezing point and water migration. The Frost Heave is caused by the freeze of water from different sources, i.e. pristine water, migrated water or both; however, it is difficult to identify the contributions of the different water sources to the Frost Heave, especially for a closed freezing system. Therefore, the calculation method to evaluate the Frost Heave induced by different water sources still need to be developed. Definitely, freezing experiments under controlled laboratory conditions can help to give a detailed description of the soil freezing process. Therefore, a large-scale one-directional freezing experiment within a closed system was carried out to investigate the hydro-thermal characteristics and Frost Heave behavior of a saturated silt. The research results showed the effect of the hydro-thermal behavior on the Frost Heave of the silt within a closed freezing system, and a calculation method was presented to evaluate the Frost Heaves from pristine water and migrated water, respectively.
-
effect of hydro thermal behavior on the Frost Heave of a saturated silty clay under different applied pressures
Applied Thermal Engineering, 2017Co-Authors: Xiyin Zhang, Mingyi Zhang, Wansheng Pei, Zhongrui YanAbstract:Abstract Civil engineering buildings are often damaged by Frost Heave of ground soils in cold regions. The hydro-thermal behavior is a key factor in determining Frost Heave of soils during freezing process. Moreover, the Frost Heave is also strongly affected by overburden pressure and external water source. Here, a series of one-directional freezing experiments with a water supply under different applied pressures were carried out to study the effect of hydro-thermal behavior on the Frost Heave of a saturated silty clay. Four different pressures were applied on the top of each soil sample, respectively, i.e. 50, 150, 300 and 500 kPa. The experimental results indicate that the Frost Heave of the supplied water is the main component of the total deformation for each soil sample with a water supply. However, the increased applied pressure can restrict water migration, and reduce Frost Heave during soil freezing process. Furthermore, for the saturated silty clay under different applied pressures, only when the advance rate of the freezing front drops to a critical value, the water intake begins. The start time of the water intake is also delayed with the increased applied pressure. Besides, the shut-off pressure of the saturated silty clay, at which no water flow into or out of the soil sample, is obtained based on the relationship between the critical advance rate of freezing front and the applied pressure.
Daichao Sheng - One of the best experts on this subject based on the ideXlab platform.
-
Modelling Frost Heave in unsaturated coarse-grained soils
Acta Geotechnica, 2020Co-Authors: Jidong Teng, Jianlong Liu, Sheng Zhang, Daichao ShengAbstract:Coarse-grained soils were considered not susceptible to Frost Heave. However, substantial Frost Heave has been observed in unsaturated coarse fills in high-speed railway embankments. Recent experimental results in the literature show that vapour transfer has a considerable influence on the Frost heaving of coarse-grained soil. However, vapour transfer has rarely been considered in modelling Frost Heave. This study presents a new Frost Heave model that considers vapour transfer and its contribution to ice formation. An updated computer program (PCHeave) is developed to account for the vapour transfer in unsaturated coarse-grained soils, where the rigid ice theory is applied to initiate ice lens formation in the frozen fringe. The results of the proposed model are compared with laboratory test results, which show reasonable agreement. The Frost Heave data monitored in 2013–2014 along the embankment of the Harbin–Dalian Passenger Dedicated Railway are also used to validate the proposed model. The prediction of the model agrees well with the measured results of Frost Heave and Frost depth. This indicates that the proposed model can reasonably reflect the process of Frost Heave caused by vapour transfer in unsaturated coarse-grained soils.
-
A Frost Heave model of unsaturated coarse-grained soil considering vapour transfer
'EDP Sciences', 2020Co-Authors: Jianlong Liu, Jidong Teng, Sheng Zhang, Daichao ShengAbstract:Substantial Frost Heave has been observed in coarse fills in high-speed railway embankments. These coarse fills have low fine contents and very low water content. The groundwater table is located below the coarse fills. The coarse fills were considered not susceptible to Frost Heave. Recent experimental results in the literature showed that vapour transfer has a considerable influence on the Frost heaving of unsaturated coarse-grained soil. But vapour transfer has been rarely considered in the modelling of Frost Heave. This study presents a new Frost Heave model with considering vapour transfer and its contribution to ice formation. The rigid ice theory is applied to initiate an ice lens formation in the frozen fringe. An updated computer programme PCHeave is developed by considering the vapour transfer. The results of the proposed model are compared with laboratory test results, which show reasonable agreement. The prediction of the model agrees well with the measured Frost Heave and Frost depth, which indicates that the proposed model can reasonably reflects the process of Frost Heave in unsaturated coarse soil
-
analysis of Frost Heave mechanisms in a high speed railway embankment
Canadian Geotechnical Journal, 2016Co-Authors: Sheng Zhang, Daichao Sheng, Guotang Zhao, Fujun NiuAbstract:The Harbin–Dalian high-speed railway in northeastern China has a significant portion of track foundation built on seasonally frozen ground. Wide-spread Frost Heave was observed during the first win...
-
a potential new Frost Heave mechanism in high speed railway embankments
Geotechnique, 2014Co-Authors: Daichao Sheng, Sheng Zhang, F Niu, G ChengAbstract:Substantial Frost Heave has been observed in coarse fills in high-speed railway embankments. These coarse fills have very low water contents, and are located above the groundwater table. In an attempt to explain the unexpected Frost Heave, it is proposed that cyclic train loads cause the development of excess pore water pressure in the underlying subgrade soil, and hence ‘pump' up the water table to the Frost front, which in turn feeds the formation of ice and results in continuous Frost Heave. A simple quantitative model is then developed to simulate the pumping-enhanced Frost Heave. The numerical results show that the proposed mechanism can indeed provide a rational explanation for the otherwise unexpected Frost Heave. The engineering implications of this new Frost Heave mechanism are also discussed, in the context of designing Frost Heave mitigation measures in seasonally frozen regions.
