Study On The Temporal And Spatial Evolutionary Characteristics And Dynamic Mechanism Of Huangnibazi Landslide In Li County

At 11:00 on August 8,2017,a landslide occurred in Huangshanba,Xishan Village,Tonghua Township,Li County,Sichuan Province.This caused a slippery soil mass of 123×10⁵ m³ and destroyed a total of 1 house and buried 2.5 x 10⁴ m2 of fruit trees.The landslide is a typical type of low-speed landslide,from its instability to the final stop,through the constant-speed slip phase,acceleration slip phase,deceleration slip phase,gradually stable slip phase,with a creepage sliding-tension features.According to studies at home and abroad,landslides can be easily divided into three categories:high-speed,medium-speed,and low-speed.Among them,high-speed and long-term landslides have become the main research object,and the attention to low-speed landslides is relatively low.Studies have shown that although most of the low-and medium-speed landslides have low activity intensity and do not like high-speed and long-term landslides that are destructive and catastrophic.However,due to the long time of the deformation and destruction of the low-speed landslide and the large threat area,it has a significant impact on the safety of people's lives and property.Therefore,the in-depth study of the Huangnibazi landslide is of great significance to further strengthen understanding of the low-and medium-speed landslide.In this paper,Huanglibazi Landslide in Li County is taken as an important research object.Based on a large number of geological surveys on the landslide site,the UAV aerial photography,RTK monitoring,surface GPS automatic monitoring,total station 3D measurement,etc.are used synthetically,the corresponding analysis and study of the macroscopic movement characteristics of the Huangniba landslide were carried out.At the same time,the necessary laboratory tests were conducted to obtain the physical and mechanical parameters of the sliding body and sliding zone soil.In combination with the discrete element numerical simulation software,the dynamic mechanism of the landslide was further analyzed.The main research contents and results are as follows:1.By analyzing the regional geological environment in the study area,the engineering geological features of the Huangnibazi landslide was further analyzed.The Huangnibazi landslide is located on the left bank of the Zagunao River in Tonghua Township,Lixian County,Sichuan Province.On the whole,the planar shape is a long strip with a wide front and a narrow back,and the profile shape is downward convex.The lithology of the landslide stratum is phyllite in Silurian and Devonian,and the landslide accumulation is mainly composed of silt-gravel and gravelly soil.The on-site survey results and surface displacement monitoring data show that the landslide destructive movement of Huangnibazi is mainly concentrated in the middle and front of the landslide.The damage in the middle region is the strongest and the movement in the front is the most obvious.At present,the overall landslide is in a gradually stable stage.The landslides are divided into three regions I,II,and III according to the characteristics of the macroscopic motion destruction exhibited in the landslide space.The movement destruction process in the III region is the most obvious.Therefore,further distinguishes III as the main sliding zone?III-1?,the squeeze deformation zone?III-2?,the re-slung zone?III-3?and the accumulation zone?III-4?.2.Analysis of spatio-temporal evolution characteristics of Huangnibazi landslide using aerial imagery of aerial drones and survey of surface destruction characteristics and displacement monitoring data.Analysis result display,The spatial-temporal evolution of the Huangnibazi landslide has obvious characteristics.Spatially,the entire type of destructive movement in Zone I is progressive-back type;the sliding Zone II is reciprocating-gradient-retreating-transition-progressive-reverse-type reciprocating;the sliding zone III is mainly progressive-back type during the destructive movement.The transition process is dominated by a shift.In terms of time,the evolutionary process of landslides has obvious stage characteristics,namely:constant velocity slip phase,acceleration slip phase,deceleration slip phase,and gradually stable slip phase.3.Based on the PFC^2D discrete element simulation and a simple theoretical analysis method,this paper discusses the starting mechanism,the accelerated motion failure process and the final deceleration slip to the gradually stable state of the Huangniba landslide.The results show that the whole process of deformation and failure of Huangnibazi landslide is divided into five stages:progressive deformation stage,start-up stage,dynamic acceleration stage,continuous deceleration stage and gradual stabilization stage.In the whole process of sports destruction,there are many effects:cumulative damage effect;sliding belt movement,static friction resistance approximate effect;sliding body potential dynamic transformation effect;sliding belt?surface?strength self-recovery deceleration effect;sliding body dynamic dissipation reduction effect.