Study On Seepage Mechanical Properties Of Surrounding Rock Of Basalt Water-rich Tunnel And Disposal Technology

Basalt is a kind of basic eruptive rock,which has the characteristics of large porosity and joint development.Therefore,the seepage,stress,strain and supporting structure of basalt tunnel are studied to further analyze the stability of basalt tunnel structure.This paper takes the basalt tunnel in Hainan as the engineering background.The main research contents and conclusions are as follows。(1)Based on the radial shear stress criterion,the formula for calculating the water pressure when the rock is destroyed is deduced.The interaction principle between the seepage field and the surrounding rock stress field is studied.When the stress field interacts with the seepage field,water level line,burial depth and rock weathering is the main controlling factor.(2)Through the establishment of numerical model,the characteristics of seepage,stress,strain and supporting structure of surrounding rock of basalt tunnel under different buried depth,water level and weathering degree are analyzed.The increase of water level leads to the increase of seepage flow,strain,compressive stress and arch tensile stress of surrounding rock,which leads to the cracking of shotcrete;the increase of buried depth leads to the increase of strain,deformation and bolt tensile stress.The decrease of buried depth leads to the cracking of the shotcrete;the higher the degree of weathering of the surrounding rock,the greater the maximum principal strain,deformation and support force of the surrounding rock;the seepage flow of the surrounding rock of the fully weathered basalt tunnel is the highest,it is more affected by groundwater.When the grouting permeability coefficient is 10% of the surrounding rock permeability coefficient,it can effectively limit the water flow and the dome deformation.(3)Establish a numerical model to analyze the seepage,stress,displacement and support characteristics of the surrounding rock of the basalt tunnel in special geological conditions.During the downward excavation process,due to the increase of the high span ratio,the arch waist will be severely deformed,but the deformation can be effectively limited after the cross bracing is applied;the deeper excavation,the greater the deformation of the vault,but the change of the floor bulge is not large;the actual convergence rate of the arch waist is cyclical changes,mainly due to the accumulation of energy and the release of energy from the deformation of the surrounding rock.(4)When the method is converted,the height of the excavation surface will increase,and the water pressure behind the excavation surface will increase and collapse.When the conversion of the method is completed,the seepage field changes,the seepage flow of the surrounding rock decreases,and the water retention of the basalt residual soil plays a role.The soil above the conversion point of the method will have a tensile stress of about 72.3 kPa.If the soil is not sufficiently reinforced,it may cause collapse.(5)Comparatively analyzing the water seepage characteristics of the fully weathered basalt,weakly weathered basalt and basalt residual soil,includ their influence on the construction;according to the seepage characteristics of the basalt tunnel,the seepage control process of the basalt tunnel is designed;according to the geological prediction and the excavation surface characteristics,the precursors,processes and causes of the occurrence of dashes forward the mud are obtained.From the geological prediction as the core,from the geological information acquisition and on-site observation,a process for early warning of dashes forward the mud occurrence is established;this paper proposes measures to prevent and control dashes forward the mud,mainly from strengthen the excavation surface,safe removal of sludge,advanced support and stratum reinforcement.