细粒含量对冰碛土抗剪强度影响的实验研究

为研究细粒组颗粒在浸水/降雨条件下产生迁移对冰碛土抗剪强度的影响，从西藏林芝市帕隆藏布嘎隆寺沟流域内采取冰碛土样品，进行7种不同细粒（粒径小于2 mm）含量情况下的冰碛土比重和相对密度的测试，开展了不同围压下的大型饱和固结不排水三轴（CU）实验。结果表明：（1）细粒含量对干密度的影响较小，不同细粒含量的冰碛土孔隙比大致相同，细颗粒对孔隙具有改造作用，不同细粒含量会引起孔隙结构的差异，从而导致冰碛土的结构差异，最终导致抗剪强度的不同；（2）细颗粒迁移导致冰碛堤坡脚和内部一定深度细粒含量较高，达到一定的量值时，抗剪强度明显降低，冰碛堤容易发生剪切破坏；（3）细粒含量对抗剪强度参数的变化具有重要影响，从中还可以反映出冰碛土结构控制的变化：粗颗粒控制→粗细颗粒共同控制→细颗粒控制。研究结果对于评价冰碛堤的稳定性具有重要意义。

Experimental study on the effect of shear strength of moraine soil with fine grain content

Inorder to study the effect of migration of fine particles under flood/rainfall conditions on shear strength of moraine soil, moraine soil samples were collectedfrom the Galongsi Gully watershed in the Pallon Tsangpo, Nyingchi City, Tibet. Tests of specific gravity and relative density ofmoraine soil under seven different fine grain (particle size less than 2 mm) content were carried out as well. Large-scalesaturated consolidated undrained（CU）triaxial test under different confiningpressures were also carried out. The results show that: (1) The effect of fineparticles on the dry density is small, the basic pore ratio of different graincontents is basically same; the fine particles have the remodeling effect on the pore, anddifferent fine particles can cause difference in pore structure, leading to structure difference ofmoraine soil, and eventually leading to different shear strength. (2) The migration of fineparticles leads to high content of fine particles in the slopes of the moraineand in its internal,which reaches a certain magnitude, the shear strength will obviously reduce and the moraine dam easy to shear failure; (3) Thecontent of fine particles has an important influence on the shear strengthparameters, reflecting the change of structurecontrol of moraine soil in such a way: coarse particle control→coarse and fine particle control together→fine particle control. The research results are helpful forthe stability evaluation of moraine dams.