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
Thawed permafrost could cause a serious stability problem for foundations and oil-wells in cold regions. A non-damage testing procedure, employing the Bender Element Method, was used for permafrost samples collected f...Thawed permafrost could cause a serious stability problem for foundations and oil-wells in cold regions. A non-damage testing procedure, employing the Bender Element Method, was used for permafrost samples collected from a continuous frozen core obtained from the North Slope of Alaska, USA. The wave velocity and modulus of thawed permafrost were investigated on various isotropic confining pressure from 0 kPa to 400 kPa per 100 kPa. The received shear wave propagation was recorded, and the elastic wave theory was used to calculate shear modulus. Finally, the shear modulus affected by confining pressure, water content and dry density were analyzed and discussed, and a regression formulation of shear modulus based on the Janbu Model for thawed silty and sandy permafrost were proposed and validation.展开更多
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.
基金the financial support from Conoco Phillips Alaska, Inc., BP Alaska, Exxon Mobil and Chevron
文摘Thawed permafrost could cause a serious stability problem for foundations and oil-wells in cold regions. A non-damage testing procedure, employing the Bender Element Method, was used for permafrost samples collected from a continuous frozen core obtained from the North Slope of Alaska, USA. The wave velocity and modulus of thawed permafrost were investigated on various isotropic confining pressure from 0 kPa to 400 kPa per 100 kPa. The received shear wave propagation was recorded, and the elastic wave theory was used to calculate shear modulus. Finally, the shear modulus affected by confining pressure, water content and dry density were analyzed and discussed, and a regression formulation of shear modulus based on the Janbu Model for thawed silty and sandy permafrost were proposed and validation.
