Study On Mechanics Principle And Countermeasures Of Adjacent Excavation In Up-down Cross Tunnels

This dissertation carried out a study on static,dynamic influence and countermeasures for up-down cross mountain tunnels(mining method), which are orthogonal or wide-angle,deep,newly-build/after-constructed tunnels crossing over or being underpass of existing/before-constructed tunnels, depending on diversion tunnel adjacent project for BaiShuiJiang third class power station in YanJin county of YunNan province, underpass of ShouBaYan tunnel of NeiKun Railway, by using methods of investigation,numerical analysis,in-situ test and analog.The following achievement and outcome was gained:1 .This dissertation predicts settlement threshold based on Peck settlement curve empirical formula,existing railway allowable displacement and existing structure allowable stress; Stress increment threshold based on existing structure intensity criterion combined with existing railway tunnel health status grade are given; Control standards for various research methods are given based on idea of risk management.2.This dissertation concludes that influential scope of railway tunnel by the construction of diversion tunnel is not symmetrical by tunnel axes and torsional deformation is generated, based on study of diversion tunnel underpass of railway tunnel and analysis of stress increment,settlement disciplinarian by the use of three-dimensional finite element method(3D-FEM); Mutual influence scope and degree of two cross tunnels are given based on control standards of settlement and stress, then safety check for existing tunnel and newly-build diversion tunnel are given and validated by jobsite monitoring: Feasibility and precision of 3D-FEM to simulate this kind of approaching excavation are proved.3.Blasting dynamical influence is studied by the use of Dynamic Explicit FEM, conclusions are: Vibration speed when excavation face is approaching existing tunnel is bigger than that when leaving existing tunnel at the same distance; The critical angle for vibration speed control direction is 45°,which is the separation angle between viewpoint-hypocenter line and horizon plane. Information-based construction of blasting excavation is realized by the use of blasting vibration monitoring, vibration speed is well controlled, and tallies numeric analysis.4.Vertical displacement and stress of underpass diversion tunnel reaches maximum value when the first bogie bolster of train in railway tunnel is just upward the diversion tunnel, then dynamical response like simple harmonic wave appears; Simulation result of cases shows that static stress is the control load and fatigue strength meets needs.5.Acting on seismic wave of single direction, the direction of maximum value of vibration speed and acceleration is coherent to loading direction; the maximum response takes place on the crown result from horizontal vibration upright of tunnel axes, the others take place on side wall; Vibration speed and acceleration attenuates to a big extent after tunnel is finished, but stress concentration occurs; Seismic response of cross section of existing tunnel is meliorated after tunnel is finished.6.Disciplinarian of tunnel stress increment influenced by single parameter change in existing tunnel is given, based on stress increment of existing tunnel and by changing radius,distance,depth,wall rock grade of two adjacent tunnels, mutual influential scope of two cross tunnels is given according to influence threshold; Matter element model of Extenics Theory is introduced to study the influence of tunnel approaching excavation, puts forward grading for up-down cross tunnels approaching influence degree, besides, influence scope is given by the use of interpolation method.7. This dissertation gives the relation between existing tunnel increment and arch crown subsidence of newly-build tunnel based on the research of newly-build tunnel countermeasure,middle stratum countermeasure and existing tunnel countermeasure, puts forward its relation with discount rate of preformed deformation; Curve for relation between existing tunnel stress increment and newly-build vault subsidence is given by weaving work condition of subsections. Criteria to choose countermeasure,jobsite monitoring item and monitoring point is given.8.This dissertation researches relational expression for detonator powder dose,distance from viewpoint to hypocenter, wall rock grade with vibration speed by changing radius of newly-build tunnel,clear distance of two tunnels, footage,priming method and wall rock grade, and puts forward formula to calculate blasting vibration speed of tunnel excavation; Vibration speed,allowable footage and safe distance are changed based on the transformed formula. The dissertation develops orbit curve according to the relationship of vibration speed,principal stress,relation curve of newly-build tunnel excavation face and control standard, and puts forward scope of application of various blasting parameter; This dissertation puts forward criteria to choose countermeasure,blasting vibration monitoring item,section and monitoring point.9. This dissertation develops prediction model for up-down cross adjacent tunnels and realizes predicting static,dynamical influence degree and influence scope for up-down cross tunnels by the use of programming, and puts forward method to choose countermeasure.