Study On Diffusion And Reinforcement Law Of High Pressure Jet Grouting In Dense Ultracataclasite Strata

With the implementation of the western development strategy and the advancement of major infrastructure construction in China.A large number of tunnels and underground projects in the fields of water conservancy and transportation in southwest region are or will be carried out.The complex geological conditions in southwest of China,such as fault fracture zone,water-rich soft rock and other unfavorable geology widely distributed,which have brought great challenges to engineering safety.For example,the Dianzhong Diversion Project in Central Yunnan Province is currently the largest and most invested water resource allocation project under construction in the southwestern area of China,and the Xianglushan tunnel is one of the project that passes through the ultracataclasite strata.Under the coupling effect of high geostress,high seepage pressure,strong construction disturbance and other factors,the geological disasters such as collapse,water and mud inrush were induced in the ultracataclasite strata.The ultracatalasite particles have the characteristics of fine particle size,strong dense and weak stability.Therefore,the ordinary cementum grouting id hardly to inject into ultracataclasite strata and the strength of grouting reinforced body is low in the process of grouting treatment of major geological disasters,resulting in poor grouting effect and difficult to effectively prevent and control disasters.Based on the existing problems,the high pressure jet grouting technology was proposed to solve the grouting reinforcement in ultracataclasite strata,which is formed grouting reinforced body by cutting and replacing the dense ultracataclasite strata around the tunnel,in order to improve the strength,stability and disaster response efficiency of the surrounding rock.The physical and mechanical parameters testing,physical simulation test and discrete element numerical simulation were carried out to analyze the physical and mechanical parameters of the ultracataclasite,and investigate the diffusion and reinforcement laws of high pressure jet grouting,which verify the feasibility and effectiveness of high pressure jet grouting in ultracataclasite strata.A suitable plan for high pressure jet grouting in dense ultracataclasite strata was proposed,which can provide theoretical basis and reference for the disasters control in similar weak strata such as collapse,water and mud inrush.The main research contents are as follows:(1)Based on the ultracataclasite samples obtained from the Xianglushan tunnel 5#construction adit of the Dianzhong Diversion Project,the physical and mechanical parameters tests were carried out to analyze the properties,such as density,water content,particle size,porosity,cohesion,internal friction angle,permeability coefficient and others.The phase composition of ultracataclasite was obtained based on XRD diffraction experiments.(2)The physical simulation tests of high pressure jet grouting in ultracataclasite strata were carried out to investigate the influence of grouting pressure,rotational speeds,lifting speeds and other key control factors on the diffusion modes,diffusion range,grouting reinforced body strength characteristics.The dynamic change law of stress at key positions of ultracataclasite was studied during the jet grouting.(3)The discrete element software PFC3D was used to carry out the numerical simulation of high pressure jet grouting in ultracataclasite strata,and the effects of the pressure,rotation speed and lifting speed on the diffusion mode and range of the jet grouting slurry were analyzed.The reliability of the numerical model was verified by comparing with the physical simulation test results,and then the evolution law of the stress and displacement of ultracataclastie under different working conditions was explored.(4)Based on the geological disaster treatment project of the 5#construction adit,the largescale discrete element numerical simulations of the ultracataclasite strata were carried out.The jet grouting technical parameters were obtained based on engineering experience.The diffusion range of the high pressure jet grouting slurry,change laws of the stress and porosity were investigated.The design scheme of high pressure jet grouting in ultracataclasite strata was proposed according to the most favorable working condition.