Deformation Mechanism And Control Technology Of Deep Buried Soft Rock Underground Engineering Working Faces

With the excavation of many high ground stress,large burial depth and underground projects,more requirements are put forward for the control of extrusion displacement and pre-convergence displacement of the inevitable soft rock stratum palm face,and the study of the deformation law and control of the working face during construction is of great significance to the excavation of deep underground projects.In this paper,firstly,the mechanical parameters change law,energy evolution law,acoustic emission characteristics and rock damage characteristics of rocks under uniaxial compression,triaxial compression,Brazilian splitting and shear tests in different water-bearing states were studied by using indoor tests to provide mechanical parameters for the numerical calculation model.Subsequently,numerical calculation models were established by FLAC ^3D software to carry out the change laws of working face extrusion displacement and working face pre-convergence displacement and control measures under different surrounding rock levels,burial depth,lateral pressure coefficient and water content,etc.The main research results are as follows.（1）The longitudinal wave velocity of mudstone increases with the increase of water content,and its uniaxial compressive strength,triaxial compressive strength,shear strength,tensile strength and elastic modulus decrease with the increase of water content of mudstone.As the water content increases,the total energy and elastic strain energy（before the peak）absorbed by the specimen decreases,with the total energy and elastic strain energy absorbed by the specimen at the peak being greatest in the dry state,followed by the natural state and least in the submerged state.（2）The acoustic emission event rate of uniaxially water-saturated rocks is almost zero,and the acoustic emission rate of mud rocks with different water contents increases compared with the compaction stage,but is still very low;the acoustic emission signal increases significantly after entering the plastic stage;uniaxially compressed rocks undergo oblique cross-sectional shear damage at low water contents,and brittle tension damage and oblique cross-sectional shear damage together at high water contents;while all triaxially compressed conditions are oblique The water content has almost no effect on the shear damage of the rock.（3）The area of the plastic zone,the extrusion displacement and the preconvergent displacement of the working face are simulated to increase with the decrease of the surrounding rock level,the increase of the burial depth,the increase of the lateral pressure coefficient and the increase of the moisture content.Grade III surrounding rock only has tensile damage or pull shear damage in the arch waist and local areas of the working face;The tensile damage and pull shear damage areas of grade IV surrounding rock are mainly concentrated in the arch shoulders,arch feet,and the edge of the working face,and most of the working face is subject to shear stress.（4）By simulating different overrunning support methods,it is concluded that overrunning grouting can reduce the pre-convergence displacement more effectively than other two overrunning supports;Control extrusion displacement by simulating step method excavation and working face anchor rod,the excavation by step method is better than the working face anchor to control the working face extrusion displacement;by comparing the working face extrusion displacement and pre-convergence displacement under the combination of control measures,the method of"spray layer+anchor rod+steel arch+overrunning grouting By comparing the extrusion displacement and pre-convergence displacement of the working face under the combined control measures,the"spray layer+anchor rods+steel arch frame+over-grouting"method is proposed.This paper contains 58figures,24 tables and 60 references.