应力状态下含黏粗粒土渗透变形特性试验研究

含黏粗粒土的渗透变形问题是水电工程中常见的渗透稳定性问题之一。对于含黏粗粒土来说,黏粒含量、颗粒级配及应力状态是影响渗透变形最重要的3个因素。为研究应力状态大小对含黏粗粒土渗透变形特性及临界水力梯度的影响,利用大直径渗透变形仪加载系统,完成了侧限条件下某含黏粗粒土在0.1,0.3,0.6,0.9 MPa铅直应力作用下的渗透变形试验。试验结果表明：不同应力状态下黏粒含量值的大小直接影响到含黏粗粒土的渗透变形破坏类型；试件中附加应力值越大,产生渗透变形时的临界水力梯度也越大。通过对渗透变形试验过程中渗透系数的演化过程研究,提出了利用渗透系数与水力梯度关系曲线的突变关系来判断临界水力梯度的新方法。

Experimental study on influence of stress state on seepage failure characteristics of coarse grained soil with cohesive particles

The seepage failure problem of coarse grained soils with cohesive particles is one of the important issues in hydro-electric engineering. For the coarse grained soils with cohesive particles, the content of cohesive particles, particle size distribution and stress state are the most important factors affecting the characteristics of seepage failure. To explore the influence of stress state on the characteristics and critical hydraulic gradient of seepage failure of the coarse grained soils with cohesive particles, seepage failure experiments on some samples of coarse grained soils with cohesive particles are performed. During the experimental process, the vertical stresses of 0.1, 0.3, 0.6 and 0.9 MPa are exerted on the top of the soil samples by using a loading system. The results indicate that the type of seepage failure of the coarse grained soils with cohesive particles is determined by the content of cohesive particle under different stress states. The larger the added stress value is, the higher the critical hydraulic gradient of the soils will be. Based on the evolution process of coefficient of permeability during the experiment of seepage failure process, a new method is proposed for the determination of the critical hydraulic gradient by use of the relation curve of coefficient of permeability and test hydraulic gradient. .