陕西泾河南岸大堡子高速远程黄土滑坡运动过程模拟

SIMULATION OF PROPAGATION PROCESS FOR THE DABAOZI RAPID LONG RUN-OUT LOESS LANDSLIDE IN THE SOUTH BANK OF THE JINGHE RIVER,SHAANXI PROVINCE

高速远程滑坡具有速度快、运程远的特点,一旦发生,人员逃离十分困难,往往造成严重灾难,因此对这类滑坡展开研究具有重要意义。对已发生滑坡运动过程进行参数反演和模拟可为潜在高速远程滑坡的预测提供借鉴。因此本文以陕西泾河南岸大堡子高速远程黄土滑坡为例,在野外调查测绘和室内试验的基础上,利用Sassa的滑坡运动模型对该滑坡运动过程进行模拟分析。结果表明,滑坡体最大平均速度为9.56m·s^(-1),具有高速运动特点,运动持时为24.5s,滑坡运动过程可分为启动加速阶段(0~5.7s)和运动减速阶段(5.7~24.5s),加速阶段平均加速度为1.68m·s(-2),减速阶段加速度为-0.51m·s(-2),加速过程比减速快3倍左右。滑坡区高陡地形和黄土高结构强度为滑坡高速运动提供条件,开阔阶地地形以及阶地砂砾石层近饱和含水条件决定滑坡远程运动特点。

Rapid long run-out landslide usually moves in high speed and travels for a long distance,therefore it trends to cause catastrophic effects on its overlong travelling path. In the study area of the Jingyang south loess tableland in this paper,this kind of landslide occurred frequently in last few decades and resulted in serious disasters. Since the destructive properties of this kind of landslide,to study its moving process and mechanism is necessary and of great significance for both study and construction purpose. Spatial prediction is a sort of effective methods to prevent landslide hazards. To make spatial prediction for rapid long run- out landslides accurately,making back analysis of the previous events is indispensable. For above reasons,this article choose a typical rapid long run-out loess landslide named＂Dabaozi＂in the south bank of Jinghe river,Shanxi,as study target to simulate its moving process and analyze its moving mechanism. Detailed field surveying was conducted,which reveals the landslide＇s matter source is mainly made up of loess stratum from L1 to L9in the slope and sand gravel in terrace infront of the slope. Sand gravel layer was apparently entrained by the original loess landslide mass which is shown by the over-thrust of sand gravel in the front of the landslide,so it was regarded as potential landslide mass in order to take entrainment into account in building the Digital Elevation Model（ DEM） of the landslide and simulation. In addition,2groups of undisturbed loess and sand gravel samples were taken from the landslide area to conduct consolidated undrained（ CU） triaxial tests and ring shear tests and some common indoor tests to get the physical and mechanical parameters needed in the simulation. On this basis, we utilized a software LS-RAPID which is developed from Sassa＇s geotechnical model to study the kinematic behaviors of this landslide. As a results,the moving speed,travelling path,thick of deposition mass and some other important kinematic indexes of the landslide were obtained. The simulation results show that the max average velocity of the landslide is about 9. 56m·s-1when it has moved 5. 7s,and the whole moving process lasts about 24. 5 seconds,and the topography obtained by simulation shows good accordance with fact in respect of the travelling distance and depositional forms. The moving process can be divided into two stage according to the transformation of motion state based on average velocity obtained from simulation,one is the starting accelerated stage（ 0s-5s） which has an acceleration of 1. 68m·s-2,the other one is the moving decelerated stage which has an acceleration of-0. 51m·s-2,and the topography of simulation shows that the transformation occurs when the whole landslide mass just reaches the terrace in front of the slope. By summarizing,we find that the initial steep topography condition in the study area and Q2loess＇ s high constructive strength play pivotal roles in making the landslide moves fast,and the landslide surface liquefaction occurred in the horizon terrace which mainly makes up of saturated sand-gravel contributes to a long travel distance,and this article can provide beneficial reference to the later study of loess rapid long run-out landslide.