西藏扎拉水电站倾倒边坡工程地质特性研究

Study on the Engineering Geological Characteristics of the Toppling Slope of Zara Hydropower Station in Tibet

倾倒边坡是一种已发生变形的特殊边坡,最终可能会发展成滑坡、崩塌等严重地质灾害。倾倒边坡工程地质特性研究是进行边坡稳定性分析评价和处理方案设计的基础,目前国内相关研究工作尚不深入、不系统,难以满足新时代工程建设和地质灾害防治需要。扎拉水电站拟建于青藏高原西藏境内怒江一级支流玉曲河,工程区边坡倾倒现象普遍发育,对工程选址和安全运行存在较大影响,区内软岩、硬岩种类多样,倾倒模式齐全,对其开展相关研究具有典型代表性。从初步调查、详细勘察到专题研究历时数年,详细论证了倾倒边坡岩体的工程地质特性。通过探索并运用多项创新技术,解决了倾倒边坡空间范围界定、工程地质分区、抗剪断强度参数取值等工程地质特性研究的难题。采用测绘、洞探、钻探、物探、测试和试验等技术,准确界定了倾倒边坡范围,提出针对性的适宜的综合勘察方法。以岩体结构、变形破坏类型为依据,首次将边坡倾倒岩体分为层状弯曲、碎裂拉张、散体坠覆等3个区,并进一步分析了各区在岩层产状、风化特征、声波波速、透水性等方面的差异。根据倾倒边坡的独特性状,提出倾倒岩体抗剪断强度可在试验值小值平均值~试验值大值平均值范围内进行取值的原则方法,对现行标准规定的取值上限进行了适当拓展。同时,补充研究了顺向坡倾倒过程,进一步完善了边坡倾倒变形破坏的力学机制。

Toppling slope is a kind of special slope which has deformed,and may eventually develop into serious geological disasters such as landslide and collapse.The engineering geological characteristics of toppling slope is the basis of slope stability analysis and evaluation and treatment scheme design,At present,the relevant research work in China is not in-depth and systematic,which is difficult to meet the needs of engineering construction and geological disaster prevention and control in the new era.Zara hydropower station is planned to be built on Yuqu River,the first tributary of Nu River in the Qinghai-Tibet Plateau,and the slope toppling in the project area is generally developed,which has a great influence on the site selection and safe operation of the project.There are various types of soft rock and hard rock in the area,and the toppling mode is complete,which provides a representative engineering case for the relevant researches.It took several years from preliminary investigation,detailed investigation to special research to demonstrate in detail the engineering geological characteristics of the slope rock mass.Through the exploration and successful application of innovative technologies,the problems in the study of the engineering geological characteristics,such as the determination of the spatial scope of the toppling slope,the division of the engineering geological areas and the valuing of the shear strength parameters,were solved.By means of surveying and mapping,hole exploration,drilling,geophysical exploration,testing and testing,the scope of the slope was accurately defined,and the appropriate comprehensive exploration methods were proposed.Based on the rock mass structure and the type of deformation and failure,the dumped rock mass of the slope was divided into three areas,i.e.,the layered bending area,fragmentation and tension area,and the area of falling and covering of loose bodies.Furthermore,the differences of occurrence,weathering characteristics,acoustic wave velocity and water permeability of rock strata at different areas were analyzed.According to the unique characteristics of the dump slope,a principle determining method of the shear strength of dump rock mass was proposed.The upper limit of value specified in the current standard was also properly extended.The mechanical mechanism of slope collapse is further improved by studying the process of slope collapse.