| In many tunnel construction,because of insufficient research on the mechanism of interaction between karst cave and tunnel,the treatment measures of karst cave are not in place,resulting in tunnel engineering accidents,such as ground collapse,tunnel roof falling,The drop of construction machinery often brings huge economic losses to the construction of the project,and sometimes seriously threatens the lives of the constructors and nearby residents.In this paper,the karst development section of a certain tunnel section of Nanning Metro is selected as the research object,from the geological structure of the site,the groundwater activity,the karst development characteristics,the ancient geographical environment and so on,the karst development law and the development mechanism of the site are discussed,and the geological model of the project area is established.The influence of karst on the stability of tunnel is studied by comprehensive analysis of cave size,groundwater characteristics,strength of surrounding rock mass,in-situ stress of surrounding rock mass,dynamic and dynamic loads and the relationship between karst cave and tunnel.The empirical formula of stability evaluation is put forward.At the same time,the numerical simulation method is used to study the mechanism of cave failure and instability caused by tunnel engineering,and further verify the empirical formula proposed in this paper.Based on the characteristics of karst development in a certain section of Nanning Metro and its influence on tunnel stability,a three-dimensional geological treatment model is established,and a complete set of technologies for tunnel karst treatment is put forward and applied to the actual tunnel karst treatment.This study can effectively reduce or avoid karst geological disasters such as ground collapse,mud inrush,tunnel instability caused by tunnel construction,reduce engineering risk and save engineering cost.The main results of the thesis are as follows:1.Through engineering geological investigation and investigation,the characteristics of karst distribution in subway tunnel field are found out,and the karst development mechanism is revealed by studying geological structure,groundwater activity and palaeogeographic environment.2.According to the size of the karst cave in the tunnel crossing area,the characteristics of the ground water,the strength of the surrounding rock body,the ground stress of the surrounding rock body,the magnitude of the static and static load and the position relation of the karst cave and the tunnel,and the empirical formula for judging the stability of the subway tunnel is put forward.3.The three-dimensional geological model of karst development in engineering area is established by using EVS(Earth Volumetric Studio)three-dimensional geological software.The model accurately describes the characteristics of karst development form,spatial distribution,filling and so on.It provides a reliable basis for the study of karst development mechanism and its treatment design in the field area.4.The numerical analysis model is established by using the OptumG2 software,and the numerical simulation method is used to analyze the effect between the karst cave and the tunnel,and the stress and strain characteristics of the tunnel excavation under different positions and different working conditions of the tunnel and the karst cave are discussed.5.The technical measures of tunnel karst treatment are systematically analyzed,and the tunnel karst treatment process is established.A complete set of technologies for urban subway tunnel treatment in karst area is given,which provides a scientific basis for the fine design of subway tunnel karst tunnel treatment scheme.6.In the aspect of detecting the effect of tunnel karst treatment,this paper puts forward the testing methods of coring drilling,dynamic penetration,water injection test and so on,and applies it to the quality inspection of a tunnel treatment project in the karst area of Nanning City,which is used in the tunnel treatment of a certain tunnel in the karst area of Nanning City.Get better result7.This paper summarizes the treatment methods of karst at home and abroad,and puts forward for the first time the treatment technology of large karst cave with concrete filling sand grouting method,and it is successfully applied to the treatment of large karst cave in a certain section of Nanning subway tunnel. |
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