水电工程坝基砾卵石层工程地质特性研究——以金沙江上江-其宗河段河床砾卵石层为例

Engineering geological characteristics of gravel layer at dam foundation of hydropower projects: case of gravel layer in riverbed of Shangjiang-Qizong reach of Jinsha River

砾卵石层是水电工程坝基经常遇到的地层之一,取砾卵石层原状样品进行室内物理力学性质试验比较困难,其工程地质特性指标通常是通过现场原位试验获得。以金沙江上江-其宗河段为例,开展了砾卵石层的工程地质特性研究。研究表明:金沙江上江-其宗河段砾卵石层整体上较均匀,粗颗粒在砾卵石层中起骨架作用,强度主要取决于粗颗粒的强度,砾卵石层的密实度随深度增加而逐渐增大,砾卵石层属于低压缩性土,具中等-强透水性,承载力、抗剪强度、变形模量、弹性模量等参数均较高,渗透破坏形式主要为管涌。砾卵石层坝基主要工程地质问题为沉降变形、渗漏及渗透稳定。

The gravel layer is often encountered in dam foundation of hydropower projects, undisturbed samples - taking for testing physical and mechanical properties in lab is difficult, and the indicators of engineering geological characteristics are usual- ly obtained through on - site and in situ test. Taking Shangjiang - Qizhong section of Jinsha River as example, the geological en- gineering characteristics of gravel layer is studied. The study shows that the gravel layer is relatively uniform on the whole, and coarse particles play a significant role in it. Its strength depends mainly on the strength of coarse particles, and its compactness increases with the depth gradually. The gravel layer is classified as a kind of soil with low compressibility and moderate to strong water permeability. Moreover, the carrying capacity, shear strength, deformation modulus, elastic modulus and other parameters are higher; piping is the main seepage destruction form. Settlement and deformation, seepage and permeable stability are the main engineering geological problems of dam fi3undation of the gravel layer.