VARIATION OF HYDRAULIC CONDUCTIVITY IN SANDY SOIL DUE TO UNDRAINED CYCLIC SHEAR LOADING

Abstract

 To investigate the hydraulic conductivity of sandy soil with excess pore water pressure due to undrained cyclic shear, the falling head permeability tests were conducted on the specimens subjected to the undrained cyclic shear. For this objective, a pressurized drainage tank with a double-pipe burette for water injection and a standpipe for drainage were newly installed to the hollow torsional shear apparatus. From the results of the undrained cyclic shear and subsequent permeability tests, the hydraulic conductivities were almost the same as the values after consolidation until the excess pore water pressure ratio increased to about 0.9 due to the cyclic loading. However, the hydraulic conductivity increased rapidly as the excess pore water pressure ratio increased above 0.9 due to the cyclic shear. After the liquefaction, the hydraulic conductivity of silica sand increased by a factor of 3 to 4 compared to the value after consolidation, while that of fine-grained soil increased by a factor of up to 27. Here, we need to pay attention that these test conditions should be limited to be less than the apparent permeability of the whole testing apparatuses.