Study On The Advanced Forecast And Strengthening Techniques For Karst Cave Filled With Mud In Tunnel Engineering

Along with the infrastructure constructions gradually pushed to the southwest mountainous region, more and more tunnels have been built in karst region, but during tunnel construction in karst region, more geological hazards problems such as sudden inflow of mud and water been happened, which caused much influences to the construction safety of the tunnel. Karst cave filled with mud is one of the most common and dangerous typical karst hazards, it is extremely easy to lead to the karst hazards such as sudden inflow of mud, roof fall if the detection or the treatment measures is inappropriate. Therefore, the key technical issues into the tunnel design and construction section is how to accurately and effectively detect the scale and the relative location of the Karst cave filled with mud in frontage of the tunnel face, and establish create the forewarning model of the safe laccolith thickness between tunnel face and karst cave, and selection which advanced pre-reinforced project can ensure that the tunnel smoothly through the cave section.Based on taking the Xianrendong tunnel of Xuda Railway as typical example, summary analysis the field application of the tunnel advanced forecast technology and combined with the core idea of "Analysis of Controlled Deformation in Rock and Soils (ADECO-RS)", establish create the forewarning model of the safe laccolith thickness between tunnel face and karst cave, analysis the reinforcing effect of the different treatment measures into the large Karst cave filled with mud. The main research results are as follows:(1)Comparative and analysis the advantages, disadvantages and applicability of the common advanced geological forecast technology, and combined with its field application achievements in Xuda railway, analysis the application effect of the Ground Penetrating Radar (GPR) and Tunnel Seismic Prediction System (TSP) which probe into the Karst cave filled with mud to get its response characteristics and provide the guidance significance for other similar projects.(2) Based on the scale and the relative location of the Karst cave filled with mud in frontage of the tunnel face by advanced geological forecast, and combined with the theoretical basis of safe laccolith thickness, like instability mechanism, factors, etc. Select means of numerical simulation, and using orthogonal test program analysis of four influencing factors (rock comprehensive quality indicators, physical and mechanical of filling cave, caverns diameter and caverns filled mud height) when the Karst cave filled with mud in frontage of the tunnel face to get the forewarning model of the safe laccolith thickness between tunnel face and karst cave. Finally, the resulting formula applied engineering examples, and comparing the numerical simulation results and the actual results of excavation to verify the reliability of the formula.(3) Based on the forewarning model of the safe laccolith thickness between tunnel face and karst cave, and combined with the core idea of "Analysis of Controlled Deformation in Rock and Soils (ADECO-RS)", mean pre-reinforcement the advanced core mud of working face and surrounding rock of tunnel. Authors use numerical simulation software calculation the Pipe-shed support and advanced small pipe, analysis and comparison the stress-strain law of dome, sidewall and invert in the tunneling process to get the best program.