The Movement Process Analysis Of Xintan Landslide

A large landslide can turn into a high-speed moving mass when it starts to slide due to the energy released. With the properties of long distance movement and huge impact force, it can destroyed houses, fields, roads, even lead to huge surge when sliding into river, making operational impact on the channel, the slope material accumulated can also clog waterways. With the Three Gorges Reservoir impounding water, many landslide disasters appeared in the reservoir area, the persistent scheduling operations of the Three Gorges Reservoir will endanger landslide disasters. So the research of landslide movement prediction has important significance.By data collection and Summary, this paper has a brief introduction to Xintan landslide, such as the geological characteristics of research area, landslide location, geological conditions, topography, lithology and deformation monitoring, etc., and based on these the formation mechanism of Xintan landslide is been studied. We discuss some research about the landslide velocity calculations, and mainly focuses on the basic theory and research process of landslide mechanics model which is used in the paper. According to profile of Xintan landslide, we establish the model slice profile, and then select calculation parameters on previous’studies, and consider the resistance of upstream face to slice in water, the velocity of Xintan landslide is calculated. Tsunami Squares basic core theory is introduced. In the numerical simulation, a plan model with the area of 4km x 4km where Xintan landslide located in the centre is established, we can simulate the sliding mass’s movement process. Then we conducted simple analysis of landslide simulation in the conditions of different parameters, such as the basal friction coefficient μb, the Movement friction coefficient μd, the response angle φ and its impact on the results. The comparative analysis of two methods (the landslide mechanics model and the Tsunami Squares simulation) in the aspects of model、theory、result presentation、workload is done in the end. The conclusions are as follows:1、The internal factors affecting Xintan landslide are mainly topography and lithology, the continuous collapse in the trailing edge accumulated the loading forces, pushing the mass to slide, and the dual structure of the slope mass also make sliding easier to occur, rainfall is the main external factor.2、The mechanics model results showed that a total of 23 slices of Xintan landslide slide into the water, that is almost 3/4 full body of Jiangjiapo slide into the river, and landslide reaches maximum velocity at 18m/s when the fourteenth slice slides to the river in the 40 seconds, and that’s the acceleration reaches Om/s2, since then it slide into the deceleration phase. When the 23th slice slides to the river, the moving process comes to the end. The max sliding time of Xintan landslide is 66s.3、The simulation results show that the maximum velocity for landslide overall slide reaches 8m/s, the maximum velocity for moving mass reaches lOm/s, the whole moving process last about 6min, where fast-moving process last 220s. The sliding process can be divided into 3 phases:1) Starting-accelerated motion stage (0-16s):when the landslide comes into the whole movement, landslide gravitational potential energy starts to release, a sharp increase in speed appears in 16s for the average speed of the slope increases rapidly from Om/s to over 10m/s and the slope thickness changes obviously. Affected by the terrain of slope border, the landslide material movement turns its direction from south-east to south-west direction by the mountain barrier effect, also a certain amount of overflow arises after steering in Huangtubao.2) Deceleration motion stage (16-220s):When the movement lasts for some time, the release of the gravitational potential energy has not met the loss of energy caused by the friction resistance for landslide movement required, the slip mass will come into a deceleration phase slip. In the 16-220s stage, the resistance affecting sliding mass movement continues to increase, decrease the velocity from lOm/s to about 0.5m/s, the sliding mass keeps moving forward. The earliest part of the trailing edge of the sliding body began to deposit, slide the front and the middle of the body gradually accumulate stagnant with the lower velocity, and the front of the comes first.3) Accumulate stagnant stage (220-380s):This stage, landslide material has sufficient long-distance movement, the gravitational potential energy is nearing completion, landslide movement speed has been greatly reduced, the overall average speed has been reduced to 0.5m/s or less, a partial central landslide remaining a relatively large velocity, most of the slide mass has come to the slow accumulation state. A total sliding distance of front edge is about 100m, moving to the middle of the river bed with the deposited thickness over 40m.4、The growth of the basal friction coefficient μb. the Movement friction coefficient μd, the response angle φ will reduce the velocity, but the velocity is less sensitive to the basal friction coefficient μb, more sensitive to the Movement friction coefficient μd, the response angle φ. Effect of water level is mainly depended on the area of sliding mass below water.5、The Tsunami Squares simulation is more coincidence with the actual situation, but in general the accuracy requirements, the choice of mechanical calculation will be more convenient.