Experimental Investigation On Laws Of Particle Crushing About Frozen Sand Under High Stress

With the quantity of projects in frozen soil rises at this stage,the mechanical properties of frozen soil under multiple stress states values more than before and some research have been made.The most apparent difference between frozen soil and unfrozen soil in composition is the existence of ice,which contributes to,unlike melting soil,unique four phase soil condition.Therefore the mechanical characteristics are related to testing situation:arrangement of grain,void ratio,temperature,confining pressure and shearing rate.The study subject of this paper is China ISO Standard Sand,it is sifted with three groups of ideal sand:d1（0.25～0.5mm）,d2（0.50～1.0mm）,d3（1.0～2.0mm）,then frozen rapidly under saturated and vacuum condition,finally made for specimens.Triaxial shearing tests about group d2 are conducted under confining pressure 0.1MPa,3MPa,5MPa,8MPa,at the temperature of-1℃,-2℃,-5℃to investigate the temperature effects on shearing properties of frozen sand,and under confining pressure 3MPa,5MPa,at the temperature of-2℃,-5℃,with the shear rate of 0.01mm/min,0.1mm/min,1mm/min to investigate how shearing rate influences shearing properties respectively.three groups of ideal sand are selected for triaxial shearing tests at the temperature-5℃,under the confining pressure 0.1MPa,3MPa,5MPa,8MPa,and with the shear rate of 0.1mm/min to evaluate the properties of particle crushing with three groups of ideal sand.The modified concept of particle crushing ratio Br from Einav is introduced to explore the influence of temperature,grain size,confining pressure and shear rate on B_r and mechanical properties of frozen sand,conditions of particle crushing about frozen sand are obtained at half peak point,peak point and residual point to evaluate the evolution law during shearing process.The main conclusions are as follows:1)The effects of temperature on frozen sand shearing characteristics are analyzed by tests results that the strength of frozen sand without pressure melting at temperature of-1℃,-2℃,-5℃increases with confining pressure,but will decrease due to the pressure melting when the confining pressure meets the criteria.2)The strength of frozen sand increases along the shearing rate,the peak strength under the same confining pressure but different shear rate have the same trend that rises with confining pressure.3)Particle crushing ratios of three groups increase with confining pressure nonlinearly,a platform period of the ratio would emerge with the pressure grows until the critical ratio comes out.The following small amplitude of pressure increase would not induce significant change in the crushing ratio.4)The evolution law about particle crushing of frozen sand is investigated by testing group d2 at three ending points:the half peak,the peak and the residual（ε₁=20%）.The results indicate that the crushing varies with axials.