考虑坑侧堆载基坑开挖土体应力路径试验研究

Experimental Study on the Mechanical Behavior of Foundation Pit Soil Considering the Loading at Pit Side

基坑开挖过程中,基坑坑侧各区域土体受到不同程度的卸荷或堆载作用,从而呈现出复杂的应力路径。因此,开展了常规三轴固结不排水剪切试验、K_0固结不排水剪切试验、K_0固结侧向卸荷试验和K_0固结侧向卸荷轴向加荷试验等不同的应力路径试验,来研究基坑开挖前后基坑坑侧土体的不同应力路径变化情况,比较分析了各应力路径条件下土体的抗剪强度、应力应变的变化情况,归纳了基坑开挖前后复杂应力路径条件下土体的应力变形及强度特征。研究表明,在不同的应力路径条件下,土体所对应的应力变形及强度参数,具有明显的差异性;软黏土在不同的侧向卸荷应力路径情况下,应力应变曲线均呈现应变软化型,且侧向卸荷对土体强度影响较大,坑侧堆载引起的轴向加荷对土体强度变化也有一定影响。

The lateral soil of foundation pit is subjected to unloading or loading effect during excavation,which results in a complex stress path.In order to research the stress change of the lateral soil during the excavation,the four types of tests,including triaxial consolidated undrained shear test,K0-consolidation undrained shear test,the lateral unloading K0-consolidation test and the lateral unloading axial loading K0-consolidation test,were carried out.The stress-strain curves and shear strength were studied.The test results show that the stress-stain curves and the parameters of strength under different stress paths tests obviously different.The stress-strain curves of the soft clay under different lateral unloading stress paths show strain softening.Both the lateral unloading and the axial loading have a great influence on the strength of soil.