考虑粗糙度的黏性土-结构接触面力学特性试验

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

为深入研究粗糙度对黏性土与结构接触面的相互作用及影响,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其粗糙度,并进行对比。利用大型直剪试验仪对红黏土-混凝土试块接触面进行直剪试验,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。结果表明: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;接触面抗剪强度和黏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,接触面黏聚力增大且逐渐趋近红黏土的黏聚力,此时剪切破坏可能发生在接触面上或接触面附近的土体内;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。

A new method for the definition and measurement of roughness of soil-structure interface was proposed based on reversing the roughness measured by sand filling method. The new method,sand filling method and the method for the measurement of peak-valley distance were used to measure the roughness of the surfaces with semi-circle grooves made by the test and the surface with tooth grooves made by the other research scholars. The comparisons were made according to the results of measurement. The direct shear tests on the interface of red clay-concrete block were carried out using the large-scale direct apparatus. The effects of roughness on the interface characteristics of shear failure and deformation were studied by quantitative analysis and the effect mechanism of roughness were discussed. The results indicated that,for the measurement of roughness of interface,the new method suggested by this paper is more effective than both sand filling method and the method for the measurement of peak-valley distance. The shear failure of interface agrees well with the Mohr-Coulomb strength failure criterion. The roughness has little effects on the internal friction angle. The growth rates of the shear strength and the cohesion reduce with the increment of roughness of interface. With the increment of roughness of interface,the cohesion of interface increases until it approaches to the cohesion of red clay. If the cohesion of interface approaches to that of red clay,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,meanwhile,the effects of roughness on shear strength of interface reduce. When the roughness of interface is low,the stress-dropping phenomenon is shown after the shear failure occurs.