考虑粗糙度影响的不同土与混凝土界面大型直剪试验研究

土与结构接触界面的力学特性对于土体与结构相互作用系统的研究具有重要意义，结构周围土体性质与结构表面粗糙度是影响接触面力学性质的重要因素。为研究结构表面粗糙度对不同土体与结构接触面的剪切力学特性的影响，采用大型直剪试验仪进行了3种土体（红黏土、砂土与碎石土）与混凝土接触面剪切试验。通过在混凝土表面预制不同数量的规则半圆型凹槽来改变表面粗糙度，并采用灌砂法对混凝土表面粗糙度进行定量评价，研究粗糙度对不同类型接触面的剪切应力与剪切位移曲线以及强度参数的影响。结果表明：土体类型对接触面的剪切应力与剪切位移曲线形态具有较大的影响，红黏土与混凝土接触面剪切曲线表现为剪切软化型，砂土与混凝土接触面剪切曲线表现出理想弹塑性特征，碎石土与混凝土接触面剪切曲线主要表现为应变硬化型。粗糙度对接触面的剪切强度有着显著的影响，不同土体与混凝土接触面的剪切强度随粗糙度的增大均有明显提高，但法向应力的增大会弱化粗糙度对接触面剪切强度的影响。不同粗糙度条件下接触面的剪切强度与法向应力之间均存在着良好的线性关系，表明接触面的剪切破坏符合摩尔-库伦准则。粗糙度的增大能显著提高接触面的表观黏聚力，但对接触面内摩擦角的影响较小。

Large-scale Direct Shear Tests of Interfaces Between Different Soils and Concrete Considering Roughness Effect

The mechanical properties of the soil-structure interface are of great significance for the study of the interaction system between soil and structure. The properties of surrounding soils and the surface roughness of the structure are important factors affecting the mechanical properties of the contact surface. To investigate the influence of surface roughness of concrete structure on shear behavior of soil-structure interface, a series of large scale direct shear tests were performed for interfaces between different soil types (red clay, sand and gravelly soil) and concrete. The surface roughness was changed by prefabricating different numbers of regular semicircular grooves on the concrete surface, and the surface roughness of the concrete was quantitatively evaluated by sand filling method. Based on the results of tests, the influence of surface roughness on shear stress-shear displacement curves and shear strength parameters of different types of interface were discussed. The test results indicated that three types of shear stress versus shear displacement curves were observed for interface between different soils and concrete, including strain softening for red clay-concrete interface, perfect plasticity for sand-concrete interface and strain hardening for gravelly soil-concrete interface. The shear strength of different types of interface increased obviously with increasing roughness. But the benefit of surface roughness was weakened under a higher normal stress. A clear linear relationship between interfacial shear strength and normal stress was observed under different roughness conditions, indicated that the shear failure of interface agreed well with the Mohr-Coulomb strength criterion. The increasing roughness could remarkably increase the apparent cohesion of interface, but had little influence on internal friction angle of interface.