引江济淮试验工程中不同尺寸试样抗剪强度的试验对比研究

Comparison Study on Shear Strength Test with Different Sample Sizes in the Yangtze-to-Huaihe Water Diversion Testing Project

边坡岩土体的抗剪强度是评估边坡稳定性的关键参数,采用较小尺寸试样可能难以反映岩土体的结构性,导致测试结果偏离实际情况。为研究尺寸效应对不同岩土体抗剪强度参数取值的影响,选取引江济淮试验工程的4种典型岩土层,进行现场原位大型剪切试验与室内小尺寸试样的直剪试验。结果表明:受原位地质条件的影响,进行现场大型剪切试验时,岩土体应力-应变曲线的剪应力峰值更突出,达到峰值以后,经历1%~2%剪应变即达残余剪应力,不同岩土体应力-应变曲线表现出明显的差异性;影响岩土体尺寸效应的因素众多,仅从黏粒含量、膨胀性、取样扰动来分析现场与室内剪切试验的差异性是远远不够的,对于不同地质的实际工程,现场原位剪切试验仍然是获取合理强度参数的关键性试验。基于试验结果,给出了该地区采用室内直剪试验所得的强度参数的建议修正比率。

The shear strength of rock and soil mass is the key parameter to evaluate slope stability.Conducting shear strength tests on small size specimens may cause the test results to deviate from the actual situation,since the small size specimen cannot reflect the insitu structural properties of rock and soil mass.In order to study the influence of size effect on the shear strength parameters of different rock and soil mass,large-scale in-situ direct shear test and the conventional laboratory direct shear test were carried out of four typical rock and soil mass from the Yangtze-to-Huaihe Water Diversion Testing Project.The results show that,in the influence of in-situ geology conditions,the large scale in-situ direct shear test has obvious softening characteristics with respect to the stress-strain relations.Residual shear stress occurs after the shear stress reaches the peak value,with shear strain of1%~2%.And different rock and soil masses have distinct stress-strain relations.Only considering clay content,expansibility of soil and sampling disturbance are not enough to analyze the difference between in-situ direct shear test and the conventional laboratory direct shear test because many factors affect the size effect of rock and soil mass.So in-situ direct shear test is an essential way to get the reasonable strength parameters in different areas.Based on the experimental results,a correction factor of the strength index is proposed to be applied to the results of the conventional laboratory direct shear test in the area.