Quantitative Analysis Of Bolt Support Effect Considering Interaction Of Surrounding Rock And Support

Convergence-confinement method is a design method of tunnel support structure that can directly reflect the interaction between surrounding rock and support structure.It is widely used in support structure design and surrounding rock stability analysis.Longitudinal displacement profiles(LDP),ground response curve(GRC)and support characteristic curve(SCC)are the three core components of the convergence-confinement method.The ground response curve reflects the relationship between the ground pressure and the ground convergence,and is an important basis for the design of the supporting structure.Tunnel engineering shows that bolt support can significantly improve the strength of surrounding rock and enhance the ground's stability.At the same time,the use of bolt for support can save the materials and reduce the weight of the supporting structure.Therefore,the bolt is widely used in geotechnical engineering.Now,the neutral point theory and surrounding rock reinforcement theory of bolt support is an accepted support theory.However,the previous research on bolt support is at the level of qualitative research,and there is little quantitative analysis of bolt support effect.The research on the influence of bolt support on surrounding rock characteristic curve is almost blank.This paper will combine the theoretical derivation and numerical simulation to study the influence of bolt support effect on the surrounding rock characteristic curve based on the Hoek-Brown strength criterion and the Mohr-Coulomb strength criterion.Firstly,based on the existing research results,the paper introduced the development process and basic principles of the convergence-confinement method The research on the mechanism of bolt support is introduced.The theory of surrounding rock reinforcement is described in the surrounding rock characteristic curve.Secondly,based on the Mohr-Coulomb strength criterion and the Hoek-Brown strength criterion,the paper using the analytical method derived the analytical formula of the surrounding rock characteristic curve.At the same time,using FLAC3 D software,the process of obtaining the characteristic curve of surrounding rock using numerical method is demonstrated.Then,using the method of homogenization,the support of the bolt is equivalent to the enhancement of the rock mass parameters within its support ran ge.The influence of bolt support on surrounding rock stiffness and surrounding rock strength is studied.Using bolt density indicates the various arrangements of bolts,quantify its support effect,and analyzes the impression of bolt arrangement on the st iffness and strength parameters of surrounding rock.At the same time,the relationship between bolt density and surrounding rock parameters is established.Based on the Mohr-Coulomb strength criterion and the Hoek-Brown strength criterion,the surrounding rock characteristic curves considering the role of bolt support are derived.Under the same conditions,the characteristic curve of surrounding rock is established by numerical method,and the analytical formula is modified by comparing the difference between analytical method and numerical method,so that the analytical formula has more practical application value.Finally,the effectiveness and practicability of the derivation formula was verified by an actual tunnel project in Xiangxi,Hunan.