Research On Revival Mechanism And Stability Of Dalixi Landslide Under Excavation

The Three Gorges area has steep mountain slopes and deep valleys.The geological structure is developed,the lithology combination is complex and diverse,and the rainstorms are frequent.It has always been a geological disaster-prone area.The Triassic Badong Formation and the Jurassic Shaximiao Formation are easily distributed in the area,which is easy to form large-scale bedding rock landslides,which have brought great vitality to people's lives and property and national important infrastructure.Threats and damage.The Dalixi landslide is a bedded rock landslide developed in this area.The administrative division belongs to Group 3 of Dali Village,Zhaojun Town,Xingshan County.The main sliding direction is 225°,the total volume is about 1465×10~4m~3,is a large landslide.The landslide is an ancient landslide formed during the geological history.After long-term stress adjustment,the slope is in a stable state.However,due to the implementation of the Dalixi Tablet Infrastructure Project of Xingshan County Ecological Industrial Park,the toe of slope was excavated in October 2015.Due to the excavation effect and the heavy rainfall during the flood season,the landslide was revived and deformed in 2017,giving the people in the disaster area Brought serious threats to life and property.Therefore,taking the Dalixi landslide as a typical case,studying the evolution law and internal mechanism of the resurrection deformation can provide a reliable theoretical basis for the early warning and prediction of similar bedding rock landslide.This paper takes the Dalixi landslide as the research object.Through the detailed field geological survey and landslide deformation feature record,combined with the basic geological data and monitoring data,the spatial and temporal distribution characteristics of the macroscopic deformation of the landslide,the mechanism of resurrection deformation and the stability evolution under excavation are carried out.Regular research,after careful study,mainly draws the following conclusions:1)Because the Dalixi landslide has the characteristics of chair-like landform,large-scale fractured rock mass and layer scratches,and the slope structure has the characteristics of soft and hard joint development,it is considered that the landslide is an ancient landslide developed during geological history.And its deformation failure mode is"sliding and bending".2)According to the temporal and spatial distribution characteristics of landslide surface cracks,the characteristics of the surface cracks of the Dalixi landslide are studied,and the cumulative displacement curves of the landslide monitoring points are analyzed.It is found that the resurrection deformation has a progressive backward characteristic from the leading edge to the rear.The sliding mode is a"multilayer shear slip"that extends from shallow to deep.3)Through the analysis of the macroscopic deformation characteristics of the landslide and the numerical simulation study,the main influencing factors of the resurrection deformation of the Dalixi landslide are the artificial excavation slope,and the rainfall is the secondary factor that promotes the resurrection deformation of the landslide.It is the time required to adjust the stress adjustment of the landslide under the action of excavation.Therefore,the geomechanical model of the Dalixi landslide is summarized as:“Excavation-induced landslides with soft layers and bedding rocks”.4)By simulating the characteristics of stress,strain and displacement field under landslide excavation,it is found that the overall disturbance of the landslide from the surface and the excavation is smaller than the excavation of the slope from the outside and inside,especially during the excavation to the middle and later stages.Combined with the deformation of the observation points of various parts of the landslide,the cumulative displacements of the observation points at the leading,middle and trailing edges of the landslide reached 575.37mm,270.77mm and 106.52mm,respectively.Compared with the cumulative displacement of each observation point under the actual excavation conditions,the landslide The displacements of the leading edge,middle and trailing edge observation points are reduced by 255.97mm,204.57mm and 91.51mm,respectively,which indicates that the excavation of the slope from the outside and inside is more disturbing to the landslide,and the deformation damage is more serious,especially The back of the landslide.Therefore,it is more reasonable to excavate the top of the slope from the surface of the slope.The innovation of this paper:1)Through the study of the basic characteristics of the Dalixi landslide,the evolution law of the resurrection deformation and the internal mechanism,the geomechanical model of the landslide is proposed as follows:“Excavation-induced landslide with soft layer bedding rock”.The deformation and failure characteristics are as follows:(1)has a"gradual backward retreat"deformation failure feature developed from the leading edge to the rear;(2)due to the existence of the weak zone between the layers,it causes"multilayer shearing"which extends from shallow to deep.Sliding"damage.2)By simulating the characteristics of stress and strain and displacement field under the excavation of Dalixi landslide,the deformations of the landslide slope from the top and bottom of the landslide are compared under the conditions of excavation and excavation.The optimal excavation scheme for excavation and excavation can effectively avoid the resurrection of the landslide.