Deformation and failure of deep clay samples are closely related to energy changes.Investigating the energy conversion and damage behavior of deep clay during loading and unloading tests has important significance for...Deformation and failure of deep clay samples are closely related to energy changes.Investigating the energy conversion and damage behavior of deep clay during loading and unloading tests has important significance for prevention-control of soil destabilization damage caused by mine shaft excavation.In the present work,triaxial tests of consolidated clay under different stress paths and stress rates were conducted.The results reveal that the mechanical properties of soils have strong stress rate effects and the samples mainly experience energy storage in the elastic stage,after that,the energy conversion mainly undergoes an increase of dissipative energy and release of elastic energy,which is also confirmed by the results of the analysis in the subsequent CT tests.Two damage indicators were compared,finding that the indicator based on dissipative energy has more obvious differences in two stress paths and can be used as a better indicator to describe the damage evolution of soils.Finally,in the triaxial shear test,due to the unloading effect of confining pressure,the damage of soils increased more rapidly near breaking than in the triaxial compression test,which indicates that the damage caused by unloading on deep soil is more abrupt than that caused by loading.展开更多
The geological and physico-mechanical properties characterization of deep soft rocks is one of the critical scientific issues for deep soft rock engineering. In the present study, X-ray diffraction(XRD) analysis,scann...The geological and physico-mechanical properties characterization of deep soft rocks is one of the critical scientific issues for deep soft rock engineering. In the present study, X-ray diffraction(XRD) analysis,scanning electron microscope(SEM), and mercury intrusion porosimetry experiments were carried out to investigate the mineral compositions, microstructure and porosity characteristics of the 13 claybearing soft rock samples collected from a deep coal mine in China. Water vapor absorption and uniaxial compressive experiments were also performed to examine water absorption characteristics and waterinduced strength degradation effect of the investigated deep soft rock samples. The results show that the dominant mineral components in mudstone, coarse sandstone and fine sandstone samples were calcite, quartz and clay respectively. The contents of clay minerals in all samples were relatively high and ranged from 12.3%(N-4) to 56.5%(XS-1). Water vapor absorption processes of all the soft rock samples follow an exponential law which is very similar to the water vapor absorption behavior of conglomerate samples reported in our earlier study. Correlation analyses also suggested that there were good positive correlation relationships between water absorptivity and clay minerals for both mudstone and sandstone samples. Furthermore, it was found that vapor absorption was not correlated with the porosity for mudstone, however, positive correlation relationship was found between them for sandstone. Correlation analysis between UCS, modulus of elasticity and water content demonstrated that both of them tend to decrease with the increase of their water content due to water absorption.展开更多
A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a...A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.展开更多
【Title】【Author】【Addresses】1The tree root distribution pattern and biomass of seventeen year old trees of Grewia optiva, Morus alba, Celtis australis, Bauhinia variegata and Robinia pseudoacacia were studied by e...【Title】【Author】【Addresses】1The tree root distribution pattern and biomass of seventeen year old trees of Grewia optiva, Morus alba, Celtis australis, Bauhinia variegata and Robinia pseudoacacia were studied by excavation method. B. variegata roots penetrated to a maximum depth of 4.78 m, whereas, M. alba roots were found down to 1.48 m depth. Lateral spread was minimum in B. variegata （1.10 m）and maximum inR. pseudoacacia （7.33 m）. Maximum root biomass of 6.30 kg was found in R. pseudoacacia and minimum （2.43 kg） was found in M. alba. For four species viz.,G. optiva, M. alba, C. australis andR. pseudoacacia, 68%-87% root biomass occurred within top 0-30 cm soil depth, but forB. variegata this was only45%. The soil binding factor was maximum in G. optiva and minimum in B. variegata. Soil physico-chemical properties also showed wide variation. The study suggests thatB. variegata with a deep root system is the most suitable species for plantation under agroforestry systems. R. pseudoacacia and G. optiva with deep root systems, more lateral spread and high soil binding factor are suitable for plantation on degraded lands for soil conservation.展开更多
Shanghai is located in eastern China and is built on overburden soil layers. It can be seen from the Mexico M S=8.1 earthquake on September 19, 1985 and the Hanshin M S=7.4 earthquake on January 17,1995 that heavy cas...Shanghai is located in eastern China and is built on overburden soil layers. It can be seen from the Mexico M S=8.1 earthquake on September 19, 1985 and the Hanshin M S=7.4 earthquake on January 17,1995 that heavy casualties and property losses have a direct relationship with overburden soil layers. Ground motions caused by earthquakes are significantly amplified when passing through the soil layers. Under the influence of these amplified motions, building structures, whose nature frequency is within the frequency band of soil amplification response, will experience more severe damage than those built on bedrock. Therefore, engineering seismologists have paid considerable attention the amplification responses in the Shanghai overburden soil layers. The amplification responses of soil and sand layers in this paper are given by the M L=4.1 earthquake in Nantong, Jiangsu Province on December 25, 2001 at 31.8° N, 120.9° E. It can be seen that the responses of soil and sand layers are very different. That is important.展开更多
基金Project(2016YFC0600904)supported by the National Key Research and Development Program of ChinaProject(BK20200653)supported by the Natural Science Foundation of Jiangsu,ChinaProject(2020M681768)supported by the China Postdoctoral Science Foundation。
文摘Deformation and failure of deep clay samples are closely related to energy changes.Investigating the energy conversion and damage behavior of deep clay during loading and unloading tests has important significance for prevention-control of soil destabilization damage caused by mine shaft excavation.In the present work,triaxial tests of consolidated clay under different stress paths and stress rates were conducted.The results reveal that the mechanical properties of soils have strong stress rate effects and the samples mainly experience energy storage in the elastic stage,after that,the energy conversion mainly undergoes an increase of dissipative energy and release of elastic energy,which is also confirmed by the results of the analysis in the subsequent CT tests.Two damage indicators were compared,finding that the indicator based on dissipative energy has more obvious differences in two stress paths and can be used as a better indicator to describe the damage evolution of soils.Finally,in the triaxial shear test,due to the unloading effect of confining pressure,the damage of soils increased more rapidly near breaking than in the triaxial compression test,which indicates that the damage caused by unloading on deep soil is more abrupt than that caused by loading.
基金provided by the National Natural Science Foundation of China (No. 51134005)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20130023120016)the Fundamental Research Funds for the Central Universities of China (No. 2010QL07)
文摘The geological and physico-mechanical properties characterization of deep soft rocks is one of the critical scientific issues for deep soft rock engineering. In the present study, X-ray diffraction(XRD) analysis,scanning electron microscope(SEM), and mercury intrusion porosimetry experiments were carried out to investigate the mineral compositions, microstructure and porosity characteristics of the 13 claybearing soft rock samples collected from a deep coal mine in China. Water vapor absorption and uniaxial compressive experiments were also performed to examine water absorption characteristics and waterinduced strength degradation effect of the investigated deep soft rock samples. The results show that the dominant mineral components in mudstone, coarse sandstone and fine sandstone samples were calcite, quartz and clay respectively. The contents of clay minerals in all samples were relatively high and ranged from 12.3%(N-4) to 56.5%(XS-1). Water vapor absorption processes of all the soft rock samples follow an exponential law which is very similar to the water vapor absorption behavior of conglomerate samples reported in our earlier study. Correlation analyses also suggested that there were good positive correlation relationships between water absorptivity and clay minerals for both mudstone and sandstone samples. Furthermore, it was found that vapor absorption was not correlated with the porosity for mudstone, however, positive correlation relationship was found between them for sandstone. Correlation analysis between UCS, modulus of elasticity and water content demonstrated that both of them tend to decrease with the increase of their water content due to water absorption.
基金Project(SWJT11ZT04)supported by the Central College Foundation of ChinaProject(2008g032-A)supported by the Major Projects S&T Foundation of China’s Ministry of Railways,China
文摘A new measurement technique is used to determine the settlement of bridge pile foundation and the thickness of deep compressed soft layer. The finite element Plaxis 3D foundation program is used in the analysis with a proposed empirical equation to modify the input parameters represented by the soil compression modulus. The results of the numerical analysis using the proposed empirical equation provide insight to the settlement analysis of pile groups in soft clayey soils; consequently, the finite element Plaxis 3D program can be a useful tool for numerical analysis. The numerical analysis is modified by adjusting the calculation of compression modulus from those obtained under pressure between 100-200 kPa by which the results of the settlement are modified and thus matching the realistic measurements. The absolute error is 3 mm which is accepted compared with the last researches. This scenario can be applied for the similar problems in the theoretical applications of deep foundations.
基金Indian Council of Agriculture Research, New Delhi for supporting the study through All India Coordinated Research Project on Agroforestry (AICRP)
文摘【Title】【Author】【Addresses】1The tree root distribution pattern and biomass of seventeen year old trees of Grewia optiva, Morus alba, Celtis australis, Bauhinia variegata and Robinia pseudoacacia were studied by excavation method. B. variegata roots penetrated to a maximum depth of 4.78 m, whereas, M. alba roots were found down to 1.48 m depth. Lateral spread was minimum in B. variegata （1.10 m）and maximum inR. pseudoacacia （7.33 m）. Maximum root biomass of 6.30 kg was found in R. pseudoacacia and minimum （2.43 kg） was found in M. alba. For four species viz.,G. optiva, M. alba, C. australis andR. pseudoacacia, 68%-87% root biomass occurred within top 0-30 cm soil depth, but forB. variegata this was only45%. The soil binding factor was maximum in G. optiva and minimum in B. variegata. Soil physico-chemical properties also showed wide variation. The study suggests thatB. variegata with a deep root system is the most suitable species for plantation under agroforestry systems. R. pseudoacacia and G. optiva with deep root systems, more lateral spread and high soil binding factor are suitable for plantation on degraded lands for soil conservation.
文摘Shanghai is located in eastern China and is built on overburden soil layers. It can be seen from the Mexico M S=8.1 earthquake on September 19, 1985 and the Hanshin M S=7.4 earthquake on January 17,1995 that heavy casualties and property losses have a direct relationship with overburden soil layers. Ground motions caused by earthquakes are significantly amplified when passing through the soil layers. Under the influence of these amplified motions, building structures, whose nature frequency is within the frequency band of soil amplification response, will experience more severe damage than those built on bedrock. Therefore, engineering seismologists have paid considerable attention the amplification responses in the Shanghai overburden soil layers. The amplification responses of soil and sand layers in this paper are given by the M L=4.1 earthquake in Nantong, Jiangsu Province on December 25, 2001 at 31.8° N, 120.9° E. It can be seen that the responses of soil and sand layers are very different. That is important.
