红黏土防渗土料在心墙坝设计中的静动力特性研究

Research on the static and dynamic characteristics of red clay anti-seepage soil materials in the design of core wall dams

摘要

红黏土在我国的南方地区分布较为广泛，是一种独特的地区性土壤类型。因为其形成环境的复杂性，导致红黏土的工程地质性质十分特殊，在工程建设中的实际应用较为复杂困难。尤其在心墙坝防渗设计等方面鲜有将红黏土用作心墙坝的防渗土料，相关方面缺乏科学的试验理论作为参照指导。因此，以滇西地区某水库工程为基础，对该水库用于作为心墙坝防渗土料的红黏土开展详细的物性试验、固结排水剪切试验、静力三轴压缩试验以及共振柱试验等，分析该红黏土土料的静动力特性。研究结果显示，研究区围内可用红黏土级配不均匀，液塑限以及塑性指数较大，工程性质较差。试验结果表明：当应力处在较大的范围内时，随着应力的逐渐升高，红黏土的抗剪强度却慢慢降低，若用摩尔强度包线表示，则呈向下弯曲的曲线。此时采用线性强度指标，通常会有出现一定的黏聚力。在固结比一定时，围压力越大，动剪模量比G/G_max随动剪应幅γ增大而衰减越慢，同时动剪应幅γ下，阻尼比D越小。

Abstract

Red clay is widely distributed in the southern regions of China and is a unique regional soil type. Due to the complexity of its formation environment, the engineering geological properties of red clay are very special, making its practical application in engineering construction rather complex and difficult. Especially in the design of core wall dams for seepage prevention, there are few cases where red clay is used as the seepage prevention material for core wall dams, and there is a lack of scientific experimental theories for reference and guidance in this regard. Therefore, based on a certain reservoir project in the western part of Yunnan Province, this study conducted detailed physical property tests, consolidated undrained shear tests, static triaxial compression tests, and resonant column tests on the red clay used as the seepage prevention material for the core wall dam of this reservoir, to analyze the static and dynamic characteristics of this red clay material. The research result show that the gradation of the available red clay within the study area is uneven, with relatively large liquid limit, plastic limit, and plasticity index, and poor engineering properties. The test result indicate that when the stress is within a relatively large range, as the stress gradually increases, the shear strength of the red clay gradually decreases. If expressed by the Mohr strength envelope, it shows a downward-bending curve. At this time, when using linear strength indicators, there is usually a certain cohesion. When the consolidation ratio is constant, the larger the confining pressure, the slower the attenuation of the dynamic shear modulus ratio G/G_max with the increase of the dynamic shear strain amplitude γ, and at the same time, the smaller the damping ratio D under the dynamic shear strain amplitude γ.

关键词

红黏土 / 心墙坝 / 三轴压缩试验 / 动剪模量 / 阻尼比

Key words

red clay / core wall dam / triaxial compression test / dynamic shear modulus / damping ratio

基金资助

国家自然科学基金地区科学基金项目(42267020)

悬臂式抗滑桩嫁接微型群桩组合加固滑坡的承载机理研究