Research On Hydraulic Coupling And Grouting Reinforcement Law Of Surrounding Rock Based On Discrete Fracture Networ

Large-scale underground infrastructure construction often encounters fractured rock mass with complex geological structure and rich groundwater,which is easy to induce tunnel leakage,water and mud outburst and other engineering disasters^[1].In order to ensure the smooth development of underground engineering construction,we need to study the seepage characteristics of fractured surrounding rock,the stress-strain characteristics of lining under the action of external water pressure and the grouting blocking law.Proving the characteristics of underground seepage,establishing the diffusion model of grout in rock mass fracture network and effectively predicting the reinforcement effect of grouting are important links in tunnel surrounding rock engineering research.In this paper,the fractured surrounding rock of diversion tunnel is generated based on the three-dimensional discrete fracture network method,and the stress-seepage coupling model of fractured rock mass is established.The influences of fracture density,opening degree,in-situ stress,external water pressure and other factors on the water inflow of fractured surrounding rock are studied,and the stability of tunnel lining under adverse conditions such as dynamic load and high external water pressure are analyzed.A two-dimensional discrete fracture network model was established based on the characteristics of the fractured surrounding rock of the water delivery tunnel,and the two-phase flow constitutive of Bingham fluid in the single saturated fracture was extended to the fracture network.The flow diffusion process of grout in the fractured rock was simulated,and the formation law of grouting ring was obtained under different grouting time,different crack angles,different grouting pressures and different crack opening degrees.The distribution characteristics of stress,deformation and water pressure of surrounding rock under the influence of different grouting rings were studied based on hydraulic coupling calculation.The results show that the water inflow is most significantly affected by crack opening degree,followed by crack density,in-situ stress and external water pressure,and the in-situ stress is inversely proportional to the water inflow.The deformation caused by external water pressure can be effectively controlled after the lining support is applied to the seepage model of surrounding rock.After the dynamic load is applied,the surrounding rock will mismove along the direction of the fault,and the stress concentration will occur on the side of the tunnel,increasing by 2～6MPa.The geometry of the grouting ring in surrounding rock is affected by the distribution characteristics of the crack,and the expansion of the grouting ring is anisotropic by the direction of the main crack,and the grouting speed is first fast and then slow.The grouting ring can effectively reduce the stress of surrounding rock and the external water pressure,and has relatively little effect on the tunnel displacement.This paper can provide theoretical basis for the stability of related rock mass engineering under the coupling effect of seepage field and stress field and the grouting plugging and reinforcement research,and provide scientific basis and technical support for the reinforcement design of deep earth engineering such as tunnels and underground caverns in water-rich rock mass.