Study On Deformation Mechanism And Safety Measures Of Surrounding Rock In Strongly Weathered Granite Tunnel

The southwestern region is an area where granite is widely distributed.Due to the perennial hot and rainy climate in these areas,the weathering of granite is obvious.After the granite is strongly weathered,it will have the characteristics of reduced strength,poor cementation,easy to soften and disintegrate in contact with water,and poor engineering characteristics.When the tunnel construction passes through the strong weathered granite surrounding rock,especially when there is rich water in the tunnel site area,It is extremely prone to geological disasters such as water inrush,mud outburst,and collapse and instability of the tunnel face.In order to ensure the safety of the tunnel during the construction process,this article relies on the Lianghe Tunnel on the Tenglong Expressway as a background,and uses indoor tests,numerical tests and field tests to study the hydraulic properties,fracture size effects,deformation mechanisms and reinforcement effect evaluation of granite.,The main research contents are as follows:(1)Aiming at the engineering characteristics of strongly weathered granite that are easy to soften and disintegrate in contact with water,and the strength characteristics are greatly reduced,the physical and mechanical characteristics and hydraulic characteristics of the sample rock samples are tested,and the density,water content,particle size,and mineral The study of basic physical indicators such as composition,based on the basic macroscopic physical and mechanical parameters,studies the influence of different water content and mineral content on the compressive strength of granite specimens and rock mechanical parameters.(2)The deformation and failure of the tunnel surrounding rock has a significant size effect.The RFPA software is used to establish different specimen size models,analyze the deformation and failure characteristics and strength characteristics of the specimens of different sizes,and the acoustic emission law,and then study the excavation span of the tunnel model The effect and the inclination effect on the change law of rock mass mechanical parameters,and determine the effective size effect range based on this,and provide a basis for engineering support.(3)Tunnel excavation is a constantly changing process in time and space.Establish the vault displacement and maximum principal stress diagram of each section of the tunnel,study the excavation space range of the surrounding rock of the strongly weathered granite tunnel,and analyze the different construction procedures.The deformation law of surrounding rock and the change characteristics of stress,the thickness of the reinforcement ring is determined according to the collapse arch theory,and the thickness of the grouting reinforcement ring is optimized and analyzed,and the optimal thickness of the reinforcement ring is obtained.(4)In view of the soft rock characteristics and physical and mechanical properties of strongly weathered granite,the safety reinforcement measures adopt advanced small pipe support.The displacement and stress of the sub-surface are analyzed to find the best support length,and the monitoring and measurement methods are used to evaluate the reinforcement effect.