To investigate the influence of drainage conditions on stress relaxation characteristics of warm frozen soil, a series of laboratory tests were carried out under drained and undrained conditions. The results indicate ...To investigate the influence of drainage conditions on stress relaxation characteristics of warm frozen soil, a series of laboratory tests were carried out under drained and undrained conditions. The results indicate that confining pressure obviously influences the relaxation process of warm frozen soil. Under undrained condition, with increase in confining pressure, the critical relaxation du- ration tends to grow as well as instantaneous relaxation. But the relaxation rate is sensitive to confining pressure in the initial stage, and with further development, the effect tends to diminish. Under drained condition, the relaxation rate is greater than that under tmdrained condition in the initial stage but with the development of relaxation, the difference decreases. The volumetric defor- mation of warm frozen clay under drained condition is much larger than that under undrained condition.展开更多
A series of directional shear tests on remolded frozen soil was carried out at 10°C by using a hollow cylinder apparatus to study failure criterion under a directional shear-stress path.Directional shear tests we...A series of directional shear tests on remolded frozen soil was carried out at 10°C by using a hollow cylinder apparatus to study failure criterion under a directional shear-stress path.Directional shear tests were conducted at five shear rates(10,20,30,40,and 50 kPa/min)and five intermediate principal stress coefficients(b=0,0.25,0.5,0.75,and 1),with the mean principal stress(p=4.5 MPa)kept constant.The results show that the torsional strength and the generalized strength both increase with the increase of the shear rates.According to the failure modes of frozen soil under different shear rates,the specimens present obvious plastic failure and shear band;and the torsional shear component dominates the failure modes of hollow cylindrical specimens.A shear rate of 30 kPa/min is chosen as the loading rate in the directional shear tests of frozen soil.The shape of the failure curve in theπplane is dependent on the directional anglesαof the major prin cipal stress.It is reasonable to use the strain-hardening curves to define the deviatoric stress value atγg=15%(generalized shear strain)as the failure criterion of frozen soil under a directional shear-stress path.展开更多
Unconfined uniaxial compressive tests were performed to study the influence of cryostructure on frozen clay's behavior,such as strain-stress,compressive strength,and failure characteristics,at temperatures varying...Unconfined uniaxial compressive tests were performed to study the influence of cryostructure on frozen clay's behavior,such as strain-stress,compressive strength,and failure characteristics,at temperatures varying from-10 to-2°C and strain rates varying from 1.0×10-5to 1.0×10-3s-1.Artificial samples were prepared of three types:(1)integral structure,(2)laminar structure,and(3)reticular structure.The impact of temperature,strain rate,and cryostructure on the mechanical properties is discussed.In general,frozen clay with various cryostructures shows strain-softening behavior in the range of testing temperatures and strain rates.For frozen clay of different cryostructures,the ultimate compressive strength increases with increasing strain rate and decreasing temperature.Under the same testing conditions,the ultimate compressive strengths from high to low are in integral samples,laminar samples,and reticular samples.Failure strain of frozen clay generally increases with increasing temperature and does not indicate any correlation with cryostructure or strain rate.The failure mode of integral and reticular samples was shear failure,while laminar samples showed tensile failure.展开更多
基金supported in part by the National Natural Science Foundation of China (No. 40871039)the 100 Young Talents Project granted to Dr.JiLin Qi
文摘To investigate the influence of drainage conditions on stress relaxation characteristics of warm frozen soil, a series of laboratory tests were carried out under drained and undrained conditions. The results indicate that confining pressure obviously influences the relaxation process of warm frozen soil. Under undrained condition, with increase in confining pressure, the critical relaxation du- ration tends to grow as well as instantaneous relaxation. But the relaxation rate is sensitive to confining pressure in the initial stage, and with further development, the effect tends to diminish. Under drained condition, the relaxation rate is greater than that under tmdrained condition in the initial stage but with the development of relaxation, the difference decreases. The volumetric defor- mation of warm frozen clay under drained condition is much larger than that under undrained condition.
基金supported by the National Natural Science Foundation of China(Nos.U1703244 and 41672310)the National Natural Science Foundation of China(No.41801038)+6 种基金the State Key Laboratory for Geo Mechanics and Deep Underground Engineering,the China University of Mining and Technology(SKLGDUEK1904)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA2003020102)the Major Program of Bureau of International Cooperation,the Chinese Academy of Sciences(131B62KYSB20170012)the National Key Research and Development Program(2017YFC0405101)the Research Project of the State Key Laboratory of Frozen Soils Engineering(Grant No.SKLFSE-ZY-16)the Science and Technology Major Project of Gansu Province(143GKDA007)the Science and Technology Planning Project of Gansu Province(No.18JR3RA376)
文摘A series of directional shear tests on remolded frozen soil was carried out at 10°C by using a hollow cylinder apparatus to study failure criterion under a directional shear-stress path.Directional shear tests were conducted at five shear rates(10,20,30,40,and 50 kPa/min)and five intermediate principal stress coefficients(b=0,0.25,0.5,0.75,and 1),with the mean principal stress(p=4.5 MPa)kept constant.The results show that the torsional strength and the generalized strength both increase with the increase of the shear rates.According to the failure modes of frozen soil under different shear rates,the specimens present obvious plastic failure and shear band;and the torsional shear component dominates the failure modes of hollow cylindrical specimens.A shear rate of 30 kPa/min is chosen as the loading rate in the directional shear tests of frozen soil.The shape of the failure curve in theπplane is dependent on the directional anglesαof the major prin cipal stress.It is reasonable to use the strain-hardening curves to define the deviatoric stress value atγg=15%(generalized shear strain)as the failure criterion of frozen soil under a directional shear-stress path.
基金supported by the Natural Science Foundation of China (41171065 and 51323004)
文摘Unconfined uniaxial compressive tests were performed to study the influence of cryostructure on frozen clay's behavior,such as strain-stress,compressive strength,and failure characteristics,at temperatures varying from-10 to-2°C and strain rates varying from 1.0×10-5to 1.0×10-3s-1.Artificial samples were prepared of three types:(1)integral structure,(2)laminar structure,and(3)reticular structure.The impact of temperature,strain rate,and cryostructure on the mechanical properties is discussed.In general,frozen clay with various cryostructures shows strain-softening behavior in the range of testing temperatures and strain rates.For frozen clay of different cryostructures,the ultimate compressive strength increases with increasing strain rate and decreasing temperature.Under the same testing conditions,the ultimate compressive strengths from high to low are in integral samples,laminar samples,and reticular samples.Failure strain of frozen clay generally increases with increasing temperature and does not indicate any correlation with cryostructure or strain rate.The failure mode of integral and reticular samples was shear failure,while laminar samples showed tensile failure.
