| With the continuous expansion of tunnel engineering scale,groundwater seepage has gradually become one of the important factors affecting the stability of tunnel surrounding rock.In the process of tunnel construction,groundwater penetrates into various parts of the underground through micro-cracks in the surrounding rock.After a series of physical and chemical actions,the mechanical properties of the rock mass will be slowly softened.Therefore,the existence of groundwater will seriously affect the stability of tunnel surrounding rock and threaten the safety of engineering construction and construction workers.Therefore,it is of great significance to study the weakening law of rock mechanical properties under hydraulic coupling for tunnel construction safety.In this thesis,the weakening effect of different water content and pore water pressure on the mechanical properties of granite samples is studied through laboratory tests,numerical simulation and theoretical analysis.The elastoplastic rock mass constitutive model considering the hydraulic coupling effect is established.Based on the selfdefined constitutive model,the optimal waterproof and drainage schemes of different surrounding rock tunnels under different waterproof and drainage systems are explored.The main work is as follows :(1)The TAW-1000 D rock rheological disturbance test instrument was used to carry out the indoor test,and the uniaxial compression tests of granite under different contents were carried out.The weakening laws of mechanical properties such as stress-strain curves,uniaxial compressive strength and elastic modulus of granite with different water contents under hydraulic coupling were compared and studied,and the influence law of water content on the fracture form of granite was analyzed.At the same time,the uniaxial and triaxial compression numerical simulation tests of jointed granite specimens under different pore water pressures were carried out by using the control variable method,and the weakening laws of pore water pressure on the peak strength and cohesion of jointed rock mass were summarized.(2)Based on the experimental data of laboratory test and numerical simulation,the weakening function formula of pore water pressure on elastic modulus and cohesion of granite samples is fitted.Based on the Mohr-Coulomb constitutive model,the stress-strain increment equation,yield function and flow rule of rock mass under hydraulic coupling are improved.The constitutive model of water-bearing rock mass considering hydraulic coupling is compiled by using the secondary development plate of FLAC3 D finite difference software and C++ computer language.This constitutive model considers the weakening effect of pore water pressure on mechanical parameters such as cohesion and elastic modulus of rock mass,which can more truly reflect the influence of groundwater on the stability of tunnel surrounding rock during the excavation of tunnel face with rich water.(3)Based on the improved constitutive model of water-bearing rock mass,combined with the investigation report and the II and IV surrounding rock of the mining section of the Shantou Bay subsea tunnel,the complex three-dimensional simulation model of the tunnel is established.Through the excavation of the tunnel face with different waterproof and drainage methods,the variation characteristics of the displacement field,stress field and seepage field of the surrounding rock of the tunnel under water-rich conditions are analyzed,and the reasonable waterproof and drainage design scheme of the mining section of the subsea tunnel is proposed.The optimization of radial grouting thickness of surrounding rock of grade IV tunnel is studied from three angles,and the influence law of grouting reinforcement layer thickness on tunnel stability is analyzed,which provides certain theoretical basis for optimizing tunnel waterproof and drainage design. |
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