Analysis Of Influence Of Tunnel Excavation On Slope Stability Of Yangjiashan Based On Non-contact Measurement Technology

The stability of rock slope is an important subject in the construction of human engineering.The slope instability caused such as the slope itself or the blasting excavation by human factors is unaffordable.Therefore,it is especially important to predict the slope stability in advance.This paper studies the influence of tunnel excavation process and distance on the stability of Yangjiashan slope by numerical simulation method.At present,the widely used numerical simulation methods include finite element method,finite difference method,etc.,but the lack of numerical simulation software pre-processing modeling greatly restricts the development of numerical simulation calculation.Therefore,We apply the method of inverse modeling of 3D point cloud to the numerical simulation software pre-processing problem,which can greatly improve the efficiency and accuracy of numerical modeling.In actual engineering,due to the influence of slope joints and other factors,the way of slope failure and damage is complex and variable.Therefore,We use the constitutive model of fractured rock mass in the calculation of the slope stability of Yangjiashan slope,which can reflect the influence of discontinuities on the stability of rock slope.In view of the above aspects,we have done the following work:1.Non-contact measurement technology includes digital photogrammetry technology and laser scanning technology.The non-contact measurement technology is used to scan the geographic information data of the slope surface of Yangjiashan,then two complete slope surface point cloud data are obtained respectively,and the convenience and integrity of the point cloud data acquired by the two are compared.Finally,the point cloud data acquired by the UAV tilt photography technology is selected for subsequent modeling operations.2.After performing pre-processing such as denoising filtering,streamlining and smoothing on the point cloud data,and then preparing for the subsequent modeling by generating a triangular mesh and a surface piece with a small amount of data.Finally,the slope solid model is generated by Boolean operation in Midas software,and meshing is performed.The data conversion program is written in C++ language,and the unit node data derived from Midas is converted into a language recognizable byFLAC3 D,so that the slope model can be quickly imported into FLAC3 D and subjected to subsequent numerical simulation calculation.3.In the FLAC3 D finite difference numerical simulation software,a new constitutive model-fractured rock constitutive model is introduced to reflect the influence of the discontinuities.The statistical model of stress-strain relationship of fractured rock mass is based on the statistical parameters of rock mass fracture network,combined with continuous mechanics,fracture mechanics and strain energy addition theory.The stress-strain relationship can truly reflect the weakening and anisotropy of rock mass mechanical parameters.Based on the constitutive model,the influence of the structural parameters of the fractured rock mass on the elastic modulus is studied.The results show that the discontinuities is the main factor that weakens the elastic modulus of the rock mass and produces anisotropy.The derived elastic modulus of rock mass is distributed as a ‘U' curve according to the changes in axial stress and the normal angle of the discontinuities,and the elastic modulus reaches the lowest value when the angle is the ?/4+?/2.The elastic modulus of rock mass is positively related to the friction angle and cohesion of the discontinuities,and inversely related to the average radius and density of the discontinuities.However,the influence of discontinuities parameters on the elastic modulus of rock mass is limited.When the average radius and discontinuities normal density exceed a certain range,the elastic modulus of rock mass will not change.4.Firstly,by comparing the influences of the different construction procedures of the CRD on the deformation and stress distribution of the surrounding rock of the tunnel,the results show that in the bias tunnel,the rock mass with the shallower side should be excavated first,and the initial support is carried out at the same time.Finally,the slope stress and displacement changes caused by tunnel excavation at different distances are simulated to analyze the influence of tunnel excavation on the slope stability.The results show that the excavation of the tunnel at a distance of 80 m from the bottom of the slope has little effect on the stability of the slope.During the construction,the construction can be carried out 80 m or more according to the actual geological conditions,and the protection work should be carried out for the convex surface of the slope.