Experimental Research on Triaxial Strength of Polycrystalline Ice

Constant-strain rate triaxial compression tests have been carried out on granular freshwater ice,at five confining pressures in the range of 0.5～2.5 MPa and four temperatures in the range of-2.0 to-15.0 ℃,in order to study the strength characteristics of ice under different confining pressures.The stress-strain curves and relationship between compressive strength and temperature are obtained.The influences of temperature and confining stress on strength characteristics are revealed through using Mohr-Coulomb criterion.The results indicate that the stress-strain curves all manifest the property of strain softening under the strain-rate of 1.67×10-4s-1 with different temperatures and confining pressures,and the maximum elastic strain is no more than 1.6%.The cohesive strength changes with temperature in the range of 1.863 to 1.998 MPa.However,in the range of test temperatures,the compressive strength increases linearly with the decrease of temperature when the confining pressure is constant.When temperature is higher than-4.0 ℃,confining pressures have little influence on the slip resistance as a result of the internal frictional angle near zero.At the temperatures of-7.0 ℃ and-15.0 ℃,the compressive strength increases with the increase of confining pressure and the internal frictional angle increases from 9.54 to 15.4.There is an approximate linear relation between confining pressure and shearing resistance,when the confining pressure is lower than 2.0 MPa,but the relation will be nonlinear when the pressure becomes more.