淤泥土与新填土接触面抗剪强度试验研究

Experimental Study on Shear Strength of Contact Surface between Silt Soil and New Fill

在坝前淤泥面加坝中,淤泥坝基和新填筑坝体的接触面是整个加坝体的薄弱部位。以宁夏南部山区西吉县南川水库坝前淤泥面加坝工程为研究对象,在参考该工程勘察报告和施工组织设计的基础上,通过改进常规应变式直剪仪测定了在不同工况下淤泥土和新填土接触界面的抗剪强度参数,分析了淤泥土的含水率和压实度对接触面的抗剪强度、黏聚力和内摩擦角的影响。试验结果表明:淤泥新填土接触面剪切特性受淤泥土的含水率和压实度共同影响;压实度相同时,随着淤泥含水率的增加,接触面抗剪强度先小幅度减小再快速减小,黏聚力先增大再快速减小,接触界面内摩擦角小幅度减小;含水率相同时,随着压实度的增加,界面抗剪强度增大,内摩擦角增大,黏聚力先缓慢增加,再快速增加,具有明显阶段性。

The contact surface of the silt soil and the new fill in the raising earth dam from upstream is the weak part of the whole dam body.The Nanchuan reservoir in Xiji County,the southern mountainous area of Ningxia,was taken as the object of study.On the basis of the engineering investigation report and construction organization design,the shear strength of the interface between silt and new fill under different conditions was measured by using the modified direct shear apparatus.The effects of water content and compactness of the soil on the shear strength,cohesion and internal friction angle of the interface were analyzed.The test results show that the shear characteristics of the contact surface are affected by the water content and the degree of compaction of the silt soil.With water content increasing,the shear strength of the contact surface decreasing by a small extent and then decreasing rapidly,the cohesion force increasing first and then decreasing,and the internal friction angle decreasing by a small extent when the compactness remains the same.With compactness increasing,the shear strength of the contact surface increasing,the internal friction angle increasing,and the cohesion increasing slowly at first and then increasing rapidly when water content remains the same.