Study On Creep Characteristics Of Grouting Reinforcement Under Dry-Wet Cycle And Tunnel Operation Stability

With the development of many geotechnical engineering,water stress coupling has become an important research field in geotechnical engineering.Under the action of water immersion,the rock will expand,soften and disintegrate,and the shrinkage and crack will occur when the saturated rock is dehydrated and dry.The process of dry-wet cycle is the important cause of geotechnical engineering diseases.For example,the slope of the reservoir bank where the water level fluctuates,the tunnel with seasonal rainfall,and other projects.The process of saturation and water loss,that is,the dry and wet cycle action will damage the material and cause degradation.The damage caused by the wet-dry cycle does not cause sudden disasters,but is the result of long-term mechanical effects.Creep refers to the phenomenon that the strain increases with time when the stress is unchanged.In tunnels and other long-term service projects related to rock mass,the time-dependent deformation caused by creep cannot be ignored,such as slope Instability,roadway collapse,tunnel lining deformation and cracking are all caused by large deformation caused by rock creep.The creep effect of rock has a controlling effect on engineering stability.The object of this study is not rock mass,but grouting-reinforced body by grouting engineering.The grouting project is currently the mainstream method of controlling underground engineering disasters and diseases.As a combination of injected medium and slurry,grouting-reinforced body has complex mechanical properties.Especially for the study of creep characteristics under long-term loading of solids,it is the key to ensuring the long-term stability of tunnel operation.The research theme of this paper is the creep characteristics of grouting reinforcement under dry-wet cycle.The specific research results are as follows:(1)The mechanical properties test of grouting reinforcement under different injected media,different grouting pressures and different dry-wet cycles were carried out.According to the uniaxial test results,a uniaxial compression creep test with stage loading was carried out to analyze the creep characteristics of grouting reinforcement,and the damage effect of dry-wet cycling on the mechanical properties of reinforcement.(2)A nonlinear viscoplastic body is connected on the basis of Burgers model to characterize the change characteristics of strain nonlinear growth after entering accelerated creep stage.Based on the principles of damage mechanics,the damage modulus of creep parameters in the model is derived.A "nonlinear viscoelastic-plastic creep model considering the damage of dry-wet cycles" describing the creep behavior of grouting reinforcement is proposed.(3)The creep equation of model in the three-dimensional state and the central difference format in the three-dimensional state of the stress increment required for secondary development is derived.Based on the FLAC3D software,using the VS2010 development platform,the dynamic link file of the modeluserGRNB creep model was compiled and generated,and the custom creep model was programmed in the software.(4)According to the supporting project-Nanshibi Tunnel in Jiangxi Province,a typical grouting section was selected to establish a calculation model.After the grouting was completed,a creep calculation of 20 years was carried out,and a dry-wet cycle was carried out every year.The variation law of the displacement of characteristic points around the tunnel during the calculation process is analyzed.A command program for calculating the safety factor of the tunnel lining was compiled in fish language,and the change in the safety factor of the lining in the 20-year calculation was calculated.