The Genetic Mechanism And Motion Characteristics Research On Mogangling Landslide Induced By The Violent Earthquake

The middle reaches of Dadu River which located in xianshuihe fault,Longmenshan fault and Anninghe fault consisting of “Y” fracture intersection is thehigh intensity seismic zone and historical earthquakes have caused a great loss tohere.This article take the Mogangling landslide induced by the magnitude7ofKangDing earthquake in1786as an example. On the basis of the collection ofinformation and the field geological investigation and study,combined with drillingexploration achievement, to detailedly analyze of engineering geological conditionslandslide, landslide district characteristics and, structural characteristics of theslope.Based on the previous analysis and summary work,further research will beconducted on the landslide`s genetic mechanism, restoring the landslide evolutionprocess and initisting departed under strong earthquake action, and the whole processof movement, calculating the velocity at different stages. Finally, to reproduce thewhole process of the dynamic action of the slope by three-dimensional discreteelement, numerical simulation. This article gets the following results:(1) Considering the landslide, factors, topography morphological characteristicsand accumulation body characteristics,landslide is initially divided into the three mainparts:Landslide source area,colluvial slope area and slope debris flow area. Besides,according to the drilling data, it reveals and,describes in detail the structure andcharacteristics of the3subzones main accumulation zones,and the results are:Landslide accumulation rock`s lithology is mainly the Jinningian-Chengjiang periodplagiogranite and inclusions of quartz diorite,and Inclusion diabase near the river.Accumulation body is not chaotically, distributed, there is still a certain regularity.By the river at the drilling reveals the phenomenon that landslide accumulation bodysubstances covered above the riverbed alluvium. Landslide band feature is not obvious,accumulation body covering the bedrock. ZK2revealed only near the interface of thebedrock and accumulation body cover from the Clastic rocks and gravel consisting ofthe small crushed, material, probably due to after Landslide hit bedrock. Bedrock affected by strong tectonism and weathering and unloading, controlled by four groupsfaceted structure, showing broken fracture. The physical and mechanical experimentsallow us to understand the mechanical properties of the landslide.(2) Based on the analysis and summary of field work, the further study will beconduced on landslide formation conditions, the evolution and development process.The sloping hill landslide formation mechanism can be summarized as: Since thepleistocene strong neotectonic movement made dadu river incised, Mogangling forms athin ridge; High energy storage of granite rock mass under the action of regional tectonicstress and unloading function in the process of incised valley formed high and steepslope; under the river stress field time-dependent action, the slope began the slip-crackin tension by the action of structural planes and the slope surface; when the DaduheRiver cut through the Detuo fault, plastic deformation happened in the fault zone, andcompression dilatancy deformation emerged in the slope upon the fault;Historical strongearthquake action intensifies progressive damage of slope surface, make the potentialfailure surface formation. Eventually kangding earthquake was triggered in1786, andform a high landslide damming of the dadu river.(3) The strong earthquake triggered landslide to lose its balance and block river’swhole process: it could be divided into vibration cracking stage, high speed startup stage,collapse sliding mass ejection stage, hitting the dispersed stage and damming river stage.According to the movement process stage, through calculating whole stroke speedoverall startup speed, landslide, debris flow movement speed, stone mass ejection speed,to get the result: Landslide departure velocity Veo30.8m/s; After the collapse of theprojectile,the velocity of reaching the lower part of the mountain rock V71.06m/s; thevelocity after collapsing V`52.75m/s; maximum velocity of debris flow vmax48.94m/s;initial velocity of the projectile flying stone V079.48m/s.(4) Discrete element simulation results show: Landslide movement and the wholeprocess of analysis and site seeing basically consistent with geological phenomena.displacement of each monitoring point, velocity response also reflects the decline ofthe overall characteristics of a one-time occurrence and movement during the collapseslip projectile Features.