高速滑坡–碎屑流颗粒反序试验及其成因机制探讨

采用室内物理模型试验对滑坡碎屑流在运动过程的颗粒分离问题进行研究,主要考虑小颗粒含量、粒径差以及滑床糙率等因素的影响。试验结果表明:碎屑物质在运动中的分离程度受粒径差影响较大、受小颗粒含量的影响较小,增加滑床糙率可以使得颗粒分离现象更加明显。结合现场调研、物理模型试验及已有研究成果对高速滑坡–碎屑流运动过程中颗粒反序的成因机制进行探讨:碎屑物质在高速运动过程中,由于小颗粒等效摩擦系数较大,碎屑物质在运动方向上出现大颗粒在前小颗粒在后的分离现象;进入减速堆积阶段,小颗粒先停积,后续大颗粒可越过小颗粒堆积物继续向前运动,而小颗粒则多被阻挡在堆积物末端,最终堆积物形成前端以大颗粒为主、末端以小颗粒为主,中部大颗粒在上小颗粒在下的堆积物结构。

PHYSICAL MODELING TESTS ON INVERSE GRADING OF PARTICLES IN HIGH SPEED LANDSLIDE DEBRIS

Laboratory experiments were carried out to study the particle segregation of rock fragments during the movement of debris avalanche. The influence of small particle contents，size differences and bed roughness were considered during the experimental process. Experimental results showed that the degree of segregation was greatly influenced by the size difference of particles and was less sensitive to the content of small particles. The particle segregation became more obvious with the increasing of the roughness of sliding bed. The formation mechanism of inverse grading during the movement of landslide was studied based on the field investigation，physical modeling tests and past studies. During the process of high speed landslide，the energy loss(relatively) of small particles was found to be larger than that of large particles，the segregation phenomenon of the larger particles in front of the small particles at the movement direction existed. After the debris avalanche entered into the stage of deceleration and accumulation，the small particles were stopped earlier than the large particles，resulted in that the large particles were moved on top of the deposits of small particles，while most of the small particles were blocked at the end of the landslide deposits. Finally，the inverse grading structure of landslide deposits was formed，where most of the larger particles were at the front of landslide deposits and most of the small particles were at the rear of landslide deposits，while the larger particles stay on top of the small particles at the middle section.