CONSTITUTIVE MODEL AND STRUCTURAL PARAMETER FOR UNLOADING DEFORMATION OF CLAY SOILS AT HIGH PRESSURE FROM TRIAXIAL TESTING

Undisturbed clay samples were taken from the Juye coal mine of 300 to 600 m below the ground surface in Shandong province.These undisturbed sample and their re-mould samples are tested in triaxial apparatus under unloading test with high pressures.The different deformation characteristics between the undisturbed and the re-mould clay samples are analyzed.A method and a structural parameter to describe the change in the deformation and strength properties of deep soil during unloading process at high pressure are put forward.Based on the results of triaxial unloading test of the clays,the structural parameter is determined.The structural constitutive model which can describe the high pressure unloading process is set up.