The Research Of The Mechanism And The Treatment Of The Water Bursting And Mud Surging In The Pipeline Karst Tunnel

The Karst conduit is produced by enlarged dissolute fissures and thus shows converged pipeline characteristics,and the Karst pipeline is functioned as the water diversion path in the groundwater circulation system,and thus has a wide supply network and sufficient water supply,which could cause serious disasters once the water bursting and mud surging occurs.This paper is based on the new project of Da-Zhai tunnel,which is located at the Express way from Bijie to Erlongguan(provincial boundaries).For the research of the mechanism and the treatment of the water bursting and mud surging in the pipeline karst tunnel.First of all,through the establishment of the revised Karst pipe filling medium seepage mechanics model of sliding instability,and the tunnel excavation when the surrounding rock of computing the minimum thickness of outburst prevention;Second,three-dimensional finite element model is established using FLAC3 D,analyzing Karst piping seepage mechanism of water inrush and precursors rule,finally,the applications of the results of the analysis to da-zhai tunnel.The main conclusions are as follows:(1)Through the characteristics and mechanism analysis of the water bursting and mud surging,the relevant mechanical model is set up,it is concluded that:(1)tunnel inflow flood mud surrounding rock when the minimum thickness of outburst prevention of boundary conditions;(2)filling medium penetration,the stability factor K of sliding instability when filling body,water bursting and mud surging to determine whether it happen.(2)Analysis of the basic law of seepage,stress field and seepage field interaction mechanism,a three-dimensional numerical model is established using FLAC3 D,the four aspects of research:(1)Before and after the analysis of fluid-structure interaction of surrounding rock stress,pore water pressure and the change of the vertical displacement,found that because of the influence of hydraulic permeability,pore water pressure and effective stress of surrounding rock,settlement of tunnel increases.(2)The status of the surrounding rocks under different lateral pressure coefficient(?)was modeled.The results demonstrated that with the ? increase,the plastic zone of surrounding rock increase,and water and mud inrush occurs eventually.(3)The variations of stress,displacement and plastic zone between filling medium and tunnel were analyzed with the change of the cavity water pressure(P).It showed that with the increase of P,the stress,displacement and plastic zone also increase,which leaded to the occurrence of water and mud inrush in the end.(4)Finally,the influence of different filling thickness on the tunnel was analyzed.The investigation of the surrounding plastic zone and internal displacement showed that the tunnels are safer with more filling materials,and the opportunity occurrence of water inrush and mud disasterwould decrease greatly.(3)Through the mechanism of Karst tunnel inflow flood disasters mud and simulation analysis,put forward da-zhai tunnel inflow flood disasters of mud treatment technology.This study not only provides insights into the investigation of the seepage failure mode of the filling medium in the Karst pipeline tunnel,but also puts forward the condition of failure.The results further reveal the disaster mechanism of Karst conduit in consideration of the disturbance factors and water pressure together during the construction.The prediction methods adopted in early stage of tunnel construction are also proposed,as well as the treatment measures for water inrush and mud disaster.This provides some important guidance for the further similar projects on the prevention of water bursting and mud surging.