砂与粘土接触界面的力学特性试验

Experiment on mechanical behavior of interface between sand and clay

利用DSJ-2型电动四联等应变直剪仪分别进行了不同粒径砂和粘土(方案1)、不同含水量砂和粘土(方案2)的直剪试验,揭示了其接触面的力学特性。试验结果表明:法向应力(σn)、砂粒径大小、砂含水量对接触面的力学特性有着重要的影响。方案1和方案2接触面的抗剪强度和达到剪切应力峰值时的剪切位移随着法向应力的增大而增大,当σn为100 kPa时,粘土和不同粒径砂的接触面剪切应力和水平剪切位移(τ-δ)关系曲线呈现应变软化现象;方案1接触面抗剪强度随砂粒径的减小而降低,方案2在σn为100 kPa时,接触面抗剪强度随砂含水量增加而降低,σn>100 kPa时,接触面抗剪强度随砂含水量增加先降低后变大;方案2在低法向应力下,接触面抗剪强度对应的含水量敏感区间为[10%,15%],且较明显。

The mechanical behaviors of the interface between sands and clay are investigated through direct shear tests on the conditions of sands with different particle size and different moisture contents by a DSJ-2 electric quadruple iso-strain direct shear apparatus.The results indicate that normal stress,particle size and moisture content of sand have important influence on shear strength.As shear stress reaches peak value in scheme 1 and 2,shear strength and shear displacement increase with normal stress increase.Whenσn=100 kPa,τ-δcurve of the interface in scheme 1 shows strain softening phenomenon.The shear strength of the interface of scheme 1 reduces along with the reduction of sand size.When σn=100 kPa,in scheme 2,shear strength of interface decreases with the increase of higher water content of sand,but whenσn100 kPa,it decreases first and then increases with the increase of water content of sand.Under low normal stress in scheme 2,the sensitive interval of water content corresponding to shear strength of the interface is [10%,15],and more obvious.