考虑粗糙度的黏性土-结构接触面力学特性试验

目前土与结构接触面的粗糙度定义未达成统一认识，不利于量化分析粗糙度对结构接触面力学性质的影响。同时，粗糙度对粘性土与结构接触面相互作用影响的研究也有待深入。为此，基于对灌砂法的修正，提出了一种测定土-结构接触面粗糙度的方法。针对试验自制的混凝土试块的半圆凹槽状粗糙表面和其他学者设计的齿形粗糙表面，使用修正后的灌砂法、常规灌砂法和试验常用的峰谷距测定法测定它们的粗糙度，并进行对比。利用大型直剪试验仪对红粘土-混凝土试块接触面进行了直剪试验，定量分析了粗糙度对接触面剪切破坏、变形等的影响，并探讨了粗糙度的影响机理。研究成果表明：针对接触面粗糙度的测定，修正后的灌砂法比常规灌砂法或峰谷距测定法都有效。接触面剪切破坏满足摩尔-库伦剪切破坏准则。粗糙度对接触面摩擦角影响不大。接触面抗剪强度和粘聚力的增长速率随粗糙度的增大而降低。随着粗糙度的增大，接触面粘聚力增大且逐渐趋近红粘土的粘聚力，此时剪切破坏可能发生在接触面上或接触面附近土体内。随着法向应力的增大，临界粗糙度减小且粗糙度对接触面抗剪强度的影响降低。粗糙度较小时，接触面剪切破坏后出现较为明显的应力跌落现象。

Experimental Research on Mechanical Characteristics of Cohesive Soil-structure Interface by Considering Its Roughness

As yet there is no consensus worldwide on the definition of the soil-structure interface roughness, which is inconducive to quantitatively analyzing the influences of roughness on mechanical properties of soil-structure interface. The further study of roughness influence on the interaction between cohesive soil and structure still needs to be implemented. To this end, a method to measure the soil-structure interface roughness was proposed through modifying conventional sand filling method. The modified sand filling method, conventional sand filling method and peak-valley distance measurement method were used to measure and compare the roughness of the surfaces with semi-circle grooves made by the authors and the surfaces with tooth grooves made by other scholars. The direct shear tests on the interface of red clay-concrete samples were carried out using the large-scale direct shear apparatus. The effects of roughness on the interface characteristics, such as shear failure and deformation, were quantitatively analyzed and the mechanism of the effect of roughness was discussed. The research results indicate that, for the measurement of interface roughness, the modified sand filling method is more effective than both the conventional one and the peak-valley distance measurement method. The shear failure of interface agrees well with the Mohr-Coulomb strength failure criterion. The roughness has a few effects on interface friction angle .The growth rates of the shear strength and the cohesion of the interface decrease with the increment of roughness of interface. Meanwhile, the cohesion of interface increases until it approaches to the cohesion of red clay, and the shear failure may occur on the interface or in the soil near the interface. With the increment of the normal stress, the critical roughness decreases, and the effects of roughness on shear strength of interface reduces. When the interface roughness is low, the stress-dropping phenomenon can be observed after the shear failure occurs.