| Xinjiang regional strati-graphic distribution was almost complete.Besides the upper Paleozoic Cambrian strata,strata from Ordovician to Cenozoic formation were widely exposed.Strata inPalaeozoic era are before were mainly dark metamorphic rock series and light metamorphic rock series,distribution in plateau mountain areas.Strata in Cenozoic erawere relatively soft rock series,distributed in hilly and plain areas.In this paper,surrounding rock samples from two hydropower station diversion tunnels in xinjiang were selected in the study,i.e.sandy mudstone and granitic gneiss.The three axis of loading and unloading tests,rheological test were carried out,the strength and deformation characteristics of the soft rock were obtained,then the elastoplastic rheological model of soft rock is established.By two development and application to the numerical calculation model,it was applied in the Xinjiang hydropower station tunnel for supporting and surrounding rock stability analysis and parameter optimization,and the constructive solutions to guide the implementation of the project was put forward.The main contents of this paper were as follows:(1)The three triaxial test loading and unloading tests were performed for original andwater damagedsandy mudstone,the complete stress-strain curves were obtained.he elasto plastic rheological model of soft rock considering water softening effect was put forward.The results show that the elastic modulus,peak strength,cohesion and internal friction angle of the original sample and immersion damage sample were significantly different,and the elastic modulus and strength decreased with the saturation time.The research results provide the basic parameters for tunnel surrounding rock support and stability analysis.(2)The three axis unloading rheological properties test of sandstone mudstone with different soaking degree under constant axial pressure unloading confining pressure and axial compression unloading confining pressure were carried out,a constitutive model based on Burgers model was established,and the variation of the parameters of the model with the immersion time was analyzed.(3)Theconventional uniaxis and triaxis and complicated unloading stress path mechanics test were carried out for the hard brittle granite gneiss.The test results show that granite gneiss has obvious brittle characteristics,unloading confining pressure and unloading confining pressure and loading unloading pressure test in shaft speed is,the higher the peak strength,axial strain corresponding to the peak strength decreases.(4)The elastic plastic rheological model was re-developed into FLAC3 D.Based on the Burgers model,the elastoplastic constitutive model of FLAC3 D was developed for two times,and the stability of surrounding rock of a diversion tunnel in Xinjiang was analyzed?Comparison between calculationresults and monitoring results,the trend is consistent;it shows that the first and three principal stress compressive stress decreased with the elevation increased,and there are the stress concentration at the faults.Considering the effect of excavation unloading,the maximum vertical displacement is located at the intersection in the cavern and middle fault parts.After applying anchor and steel support support,the maximum displacement decreased,the maximum tensile stress appeared in supporting concrete,and the fault location is located in the intersection of cavern.In general,the deformation and stress of surrounding rock are improved greatly after the support measures are taken,and the tunnel becomes more stable,which can meet the requirements of various operating conditions. |
PDF Full Text Request