Study On The Hazard Analysis Of Water Inrush And The Prediction Of Water Inflow In Hongyashan Karst Tunnel

As an underground structure in highway construction,tunnels play an important role in improving transportation efficiency.During the construction of karst tunnels,accidents of a large amount of groundwater suddenly rushing into the tunnel are prone to occur,which seriously threatens the safety of construction personnel.This paper takes the Hongyashan Tunnel as the research objective,and establishes the Hongyashan Tunnel Water Inrush Hazard Evaluation System by analyzing the hydrological and geological characteristics of the study area,and conducts the water inrush hazard evaluation on the tunnel section.Based on the existing hydrogeological data On the basis,numerical simulation method and traditional empirical theory method are used to predict the water inflow.The research results provide scientific suggestions for the safe construction of the tunnel project.The main research contents and results of this paper are as follows:(1)According to the special hydrogeological conditions of the tunnel site and the disaster factors of karst tunnel water inrush,8 evaluation indicators were selected from four aspects:surrounding rock grade,rock solubility,geological structure,and topography.The Analytic Hierarchy Process(AHP)was used to determine the index weights,and the attribute discrimination model was used to construct the Hongyashan Tunnel Water Inrush Hazard Evaluation System.(2)Based on the Hongyashan Tunnel Water Inrush Hazard Evaluation System,the tunnel section is evaluated for water inrush hazard.The results show that the Hongyashan Tunnel has a particularly significant risk(I)tunnel section,which accounts for 8.81%of the length;1 major risk(The length of the tunnel section ofⅡ)accounts for 13.38%;the length of 6 medium～risk(Ⅲ)tunnel sections is 65.02%;the length of 2 tunnel sections of general risk(IV)accounts for 12.79%.The results show that the medium～risk tunnel section accounts for the largest proportion.(3)Establish the hydrogeological conceptual model of the study area of the tunnel site,import the conceptual model into the 3D grid module for spatial discretization,and perform fitting and verification of the model;study the effect of different hydraulic conductivity coefficients on the tunnel when the tunnel is completely unblocked The results show that as the hydraulic conductivity of the tunnel increases,the water head on the left side gradually decreases and the water head on the right side gradually increases around the tunnel;the simulation and analysis of the impact range of different water inflows on the seepage field when water inrush occurs,The results show that with the increase of water inflow,the range of influence changes from"bundle"to"fan".(4)Prediction of the water inflow of the Hongyashan Tunnel by using numerical simulation method,groundwater runoff modulus method and atmospheric rainfall infiltration method.The calculation results under each method show that the fluctuating trend of the water inflow in different tunnel sections is basically the same,but the maximum water inflow predicted by the groundwater runoff modulus method and the atmospheric precipitation infiltration method are 16988.59 m~3/d and 10250 m~3/d,respectively.The water inflow section is concentrated in ZK70+850～ZK71+640,and the maximum water inflow of Hongyashan Tunnel calculated by numerical simulation method is 10591.67 m~3/d,and the maximum water inflow section is in ZK72+380～ZK72+900.