Numerical Simulation Of Tunnel Collapse Treatment And Its Optimization Analysis

Mountains in southwest China are widely distributed. Terrain conditions are very complex.Tunnels projects often account for a large proportion when roads or railways are built in theseplaces. Rock stability problems have become increasingly prominent in the process of constructionof the tunnel. Tunnel collapse is one of the most common phenomenon among disaster. It has ahigh-risk，high-frequency，and high burst characteristics. If mismanagement，collapse not onlydelayed period，and increased construction costs，but also left significant security risks. Therefore，summarying collapse accident factors and Treatment method has great practical significance forthe safe construction of the tunnel.In this paper，the type of tunnel collapse，treatment methods typical measure mechanism ofaction，and the mechanical behavior of tunnel collapse in treatment construction process arestudied by using theoretical analysis and numerical simulation.Finally，the basic principles oftunnel collapse treatment design and optimization approaches are summarized，the main resultsobtained are as follows：（1）Through the many cases of tunnel collapse accident analysis，this paper summarizes themain factors of tunnel collapse such as adverse geological conditions，groundwater，designconsiderations，construction and management factors. And from the size，mechanism，controllingfactors and landslides position classification system for the tunnel collapse.And tunnel collapsewas classified from the size，mechanism，controlling factors and landslides position.（2）Combined with the advance guard theory of tunnel collapse，this paper studied themechanism of action ahead of the small pipe grouting，and jet pipe roof support and other typicalanchor support measures by theoretical analysis and mechanical derivation methods.Pipe roofmechanical model of the tunnel excavation was built.Rock stress and displacement in differentconditions under the steel arch support were analyzed by FLAC3D software.The conclusions areas follows：1）Steel arch can inhibit stress concentration of the foot arch，while the dome appearsto reduce the scope of the low stress areas，and can effectively inhibit the vertical displacement ofthe vault and floor；2）The maximum axial force and bending moment were increased with theincrease in the arch steel arch spacing；3）The maximum axial force steel arch occurs mainly at thecrown，while the maximum bending moment occurs mainly in the arch and vault at the waist，andarch at the moment is very small.（3）Combined with Shenjiashan tunnel collapse accident in Guanggan highway，the paper analyzes the construction simulate the mechanical behavior of rock collapse segment caused stressfield，displacement field and variation of the plastic zone calculated by FLAC3D numericalsoftware.The conclusions are as follows：1）The maximum principal stress tensile stress occurs inthe vault60°range and the central backplane while the maximum principal stress of compressivestress occurs in the middle part of the foot of the tunnel arch；2）Vault subsidence maximumdisplacement is mainly distributed in the range of60°vault，floor uplift maximum displacement ismainly distributed in the1/3of the central bottom.3）As the excavation proceeds，the central cavitycollapse began to appear plastic zone（tensile yield based），the arch plastic zone（shear yieldbased） significantly increased the scope and depth of rock to develop.If unchecked，the arch partof shear failure may occur.4）The results showed that treatment measures played an active role inthe collapse of governance throughout the process，and the arch and vault60°range are the focusof the site in support of this collapse treatment construction.（4）Treatment of tunnel collapse should generally follow the basic principles“first flood，after reinforcement，anti expanded reprocessing”.In order to achieve safe，fast，economicalengineering purposes，treatment measures should be conditional premise sooner rather thanlater.And the basic way to optimize the design is elaborated from choosing the excavationmethods， support method selection， construction of information technology， improvingconstruction management level.