Reserch Of Tunnel Rock Classification And Support Measures Underthe Condition Of TBM Construction In JinpingⅡ Hydropower Station

TBM construction method is a new drilling and excavation technology,ithas great advantages in deep long tunnel than drilling and blasting method.It isbecause when the tunnel buried deep,the length long,the hole diameterlarge,TBM has short construction. TBM will be the preferredmethod when the constraints face the problems such asspeed,efficiency,environmental protection,safety.Jinping hydropower tunnel hasthe characteristics of great depth,long hole line,big diameter, high field stressand the high external water pressure. There are4diversion tunnels at JinpingHydropower Station of which1#&3#diversion tunnels are constructed byTBM construction and2#&4#diversion tunnels are constructed by drillingand blasting method. There are much differences between the TBM and the drillblasting methords. The key is the cavity holes which includes rock surfacesmoothness, joints and exposion, extension, open condition and so on.So, it isunsuitable to use the conventional methods to classify the surrounding rocks inTBM tunnel.There is not yet a good rock classification system under theconditions of TBM drilling and tunneling. Useing traditional method of rockclassification methods in drilling and blasting tunnels can not meet theconstruction requirements of the scene. To solve this problem, it is veryimportant to build a applicable tunnel rock classification system for the area ofTBM excavation tunnel and put forward the corresponding support measures.By useing methods of geological information survey, theoretical analysis andnumerical simulation tools,this article mainly research from the followingaspects: (1)TBM construction conditions, respectively, by means of geologicaldata analysis and numerical simulation of deformation and failure characteristicsof rock classification and support measures to provide a theoretical basis. In theanalysis of geological data, the macro-and microscopic features of the structuresurface are analysed. From the comparative analysis we can see it has greatdifference of the surface conditions,the structural surface occurrence in theoriginal system JPHC structural between the two different constructiontechniques.It will bring large errors if the structure of the surface that collectedin the TBM excavated cavern still be the surrounding rock stability factor. Usesoftware based in constitutive model established simulate the TBM constructionsegment surrounding rock then can know the deformation and failurecharacteristics of different parts of surrounding rock in the TBM constructionconditions. Plastic zone is mainly distributed in the top arch, north side of thewall, south end of the side walls and arch,stress of sidewall location is moreconcentrated, the depth of the plastic zone increases more obvious whensurrounding rock excavating. The surrounding rock score score of stressmagnitude,the displacement value, the plastic zone depth has increased in thebusted rock. Through the analysis of deformation and failure characteristics ofthe TBM can prepare tunnel theoretical for the later chapters.(2Use analytic hierarchy process to the weights analysis of important factorsas the occurrence of the environment (including ground stress and groundwaterfactors), geological factors (including saturated uniaxial compressive strength ofrock, the rock mass integrity coefficient and the rock structure of the threefactors).Then the JPHC_Tsystem is established and the applicability is analysed.The results of applicability analysis is more than88%,can meet the engineeringrequirements. In the heights stress fracture more obvious holes segment heightsstress reducted,the applicability of the JPHC_Tis same well.(3) TBM construction method is not sufficient to expose the structuralsurface of the number of joint sets, joint spacing, etc. By reflecting the degree ofrock complete with the RQD/Jn to fix the original JPQ system then canestablish the JPQTsystem and analyse the applicability. The results ofapplicability analysis is more than85%,can meet the engineering requirements.In the heights stress fracture more obvious holes segment heights stressreducted,the applicability of the JPQTis same well. (4)Optimize the design of rock support measures in TBM constructionsegment based on the numerical simulation results. Jinping surrounding rock hasdifferent loose circle thickness in different parts. In the north and south sidesspandrel arch foot loose circle thickness was significantly greater than the end ofthe vault and the arch. The bolt length should be about0.5m longer at arches,spandrel, wall and other parts than the end of the vault and the arch of siteconstruction. To Highland stress such as rockburst fracture segment surroundingrock,the length of the bolt should adjust the site actual base on acrossing theplastic zone,especially at the north side of the spandrel and the south side of thearch of the foot position.