黄土-砂浆块界面剪切特性试验及本构模型研究

Experimental analysis of interfacial shear behavior of loess-mortar block and construction of constitutive model

构筑物与土体接触面力学行为是岩土工程研究的热点之一。基于一系列直剪试验,研究不同法向压力、土体含水率条件下黄土-水泥砂浆块界面剪切特性。结果表明,(1)在土体含水率为9.2和13.1%条件下,法向压力为50、100 kPa时黄土-沙浆块界面剪切应力-位移曲线表现为应变软化型,且可分为峰值前、峰值后及残余阶段三部分,在法向压力为200、300k Pa时表现为应变硬化型;在土体含水率为17.1、20.8%条件下,不同法向压力时黄土-砂浆块界面剪切应力-位移曲线均为应变硬化型;(2)黄土-砂浆块界面的抗剪强度包络线符合摩尔-库仑准则,随着含水率的增大,界面黏聚强度降低显著,摩擦强度略有增加,整体抗剪强度降低。当土体含水率由9.2%增加至20.8%时,界面黏聚力由41.5 kPa下降至3.6 kPa,界面摩擦系数由0.50增大至0.58。用非线性模型对界面剪切应力-位移曲线关系进行拟合,结果表明非线性模型可较好反映黄土-砂浆块界面的剪切特性。

The mechanical behavior of the interface between the structure and soil has become one of the hotspots in geotechnical engineering.A series of direct shear tests on the loess-cement mortar interface was carried out to study the interfacial shear properties under different normal stresses and water contents of soil.The results show that:(1)the shear stress-horizontal displacement curve of the loess-cement mortar interface presents strain-softening characteristics,including the pre-peak,post-peak and residual strength regions,with the normal stress of 50 and 100 kPa and the water content of 9.2%and 13.1%.While it presents a strain-hardening state when the normal stress is 200 and 300 kPa.When the water content of the soil is 17.1%and 20.8%,the shear stress-displacement curves at the loess-cement mortar interface show the strain-hardening effect with different vertical stresses.(2)The shear strength envelope of the loess-cement mortar interface is in accordance with the Mohr-Coulomb criterion.The shear strength of the loess-sand block interface meets the Mohr-Coulomb criterion.As the water content increases,the interface cohesive strength decreases significantly,while the frictional strength increases slightly,and the overall shear strength decreases.When the soil moisture content increased from 9.2%to 20.8%,the interface cohesion decreased from 41.5 to 3.6 kPa,and the interface friction coefficient increased from 0.50 to 0.58.The nonlinear model is used to fit the shear stress-displacement curve of the interface.The results show that the nonlinear model can better reflects the shear behavior of the loess-mortar block interface.