黄土?砂浆块界面剪切特性试验及本构模型研究

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、300 kPa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。

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

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.