坝前淤泥土与新填坝体接触面抗剪强度试验研究及工程应用

坝前淤泥面与新填筑坝体接触面是"坝前淤泥面加坝"技术的薄弱环节。为了探究不同工况下淤泥坝基、新填筑坝体,以及淤泥土-新填土接触面的剪切强度特性,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,通过常规应变式直剪仪、改进常规应变式直剪仪分别进行剪切试验,分析了淤泥土含水率和压实度变化时,淤泥土、新填土、淤泥土-新填土接触界面的抗剪强度、黏聚力、内摩擦角的变化规律。试验结果表明:新填土抗剪强度最大,不同工况下淤泥土-新填土接触界面的抗剪强度介于淤泥土和新填土的抗剪强度之间;淤泥土含水率在12%~16%之间存在最优含水率,超过该含水率后,淤泥土及淤泥土-新填土接触界面之间的抗剪强度均显著降低;当淤泥土含水率从8%增加至12%、16%时,黏聚力减小8%左右后迅速减小至22%,具有明显的阶段性,而淤泥土-新填土接触界面的黏聚力呈现先增加后减小的趋势;当含水率相同时,随着压实度的增加,淤泥土、淤泥土-新填土接触面的黏聚力、内摩擦角总体呈增大趋势。最后根据试验结果对"坝前淤泥面加坝"工法的工程应用提出了相关建议。

Experimental study and engineering application of the shear strength of the interface between silt soil and new fill soil

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. In order to investigate the shear strength characteristics of the silt dam foundation, the newly filled dam body, and the silt-new fill contact interface under different working conditions, the project of adding the dam in front of the silt surface of the Nanchuan Reservoir in Xiji County, southern Ningxia, is taken as the research object. The conventional and improved strain-type direct shear testers are used in shear tests. The shear strength, cohesion and internal friction angle of the contact interface of silt soil, new fill and silt-new fill are analyzed as the moisture content and degree of compaction change. The results show that: The new fill has the highest shear strength. Under different working conditions, the shear strength of the silt-new fill interface is between the shear strength of the silt soil and the new fill. There exists optimal water content between 12% and 16% of the silt soil water content. When this water content is exceeded, the shear strength between the silt soil and the silt-new fill contact interface is significantly reduced. When the water content of the silt soil increases from 8% to 12% and 16%, the cohesive force decreases by about 8% and then rapidly decreases to 22%, which has obvious stages. The cohesive force of the silt-new fill interface shows a trend of first increasing and then decreasing. When the water content is the same, as the degree of compaction increases, the cohesive force and internal friction angle of the silt and silt-new fill contact surface generally increase. Finally, based on the test results, suggestions are made for the engineering application of the dam adding technology.