Time-dependent Deformation And Frature And Microscopic Evolution Mechanism Of Marble Of Jinping Ⅰ Hydropower Station

The time-dependent deformation and fracture of rock has been one of the veryimportant and complicated research subjects in the field of civil engineering and related.Engineering practices and researches show that in many cases，damage and instability ofrock engineering is not occured immediately after excavation，the stress and deformationof rock mass is changing with time development and constantly adjusting，deformationstability often continues a long time，such as time-lagging rock burst、time-dependentlarge deformation and so on. Deformation and fracture of rock mass，is closely related tothe microscopic evolution mechanism of time-dependent deformation and fracture ofbrittle rock under complex stress，but research on time-dependent deformation andfracture and microscopic evolution mechanism is still in infancy，a new technical meansand theoretical approach is needed to further the understanding. In view of this，based onindoor tests of marble of Jinping I hydropower station，with three-dimensional particlecode computation theory，and BPM model、PSC model and clump units，this paperestablishes microscopic mechanical model of marble with mineral granular. Throughresearch on time-dependent mechanical properties of marble under different stress levelsand stress strength ratios，this paper explores in-depth time-dependent deformation andfracture and microscopic evolution mechanism of brittle rock. In this paper，worksmainly focused on the following several aspects：1．The three-dimensional computation theory of PSC model is introduced in thispaper，this theory is based on microcopic parallel-bond model of three-dimensionalparticle code and linear elastic fracture mechanics theory，by introducing exponentialdamage rate of microscopic internal stress drived，forming microscopic parallel-bondtime-dependent model with time effect of stress-corrosion particle fracture，used todescribe time-dependent fracture of rock in microscopic level.2．Through sensitivity analysis of rock microscopic mechanical parameters，thispaper explores in-depth the influence of microscopic mechanical parameters onmacroscopic mechanical responses and creep deformation. Results show that: elasticmodulus is controlled by the Young’s modulus at each particle-particle contact、theYoung’s modulus of each parallel bond、the ratio of particle normal to shear stiffness and the ratio of parallel-bond normal to shear stiffness，peak strength depends on theparallel-bond normal and shear strengths，creep frature time is controlled by1、2andwhether rock creep occurs depends on a.3．Based on three-dimensional particle code、BPM model、PSC model and clumpunits，and with mineral ingredients of SEM testing of marble of Jinping I hydropowerstation，this paper establishes microscopic mechanical model of marble with mineralgranular. On the basis of sensitivity analysis of microscopic mechanical parameters，withresults of indoor compression and creep test and identification methods of microscopicmechanical parameters， the transient and time-dependent microscopic mechanicalparameters of marble are determined，microscopic mechanical model of marble is alsoestablished.4．Through numerical creep test of microscopic mechanical model of marble underdifferent stress levels and stress strength ratios single-stage loading，this paper studies theaffect of stress level and stress strength ratio on time-dependent deformation and fractureof marble，and microscopic evolution mechanism of marble. Results show that: thelong-term stress strength ratio is controlled by stress level，and the higher confiningpressure，the lower the effect of time-dependent deformation and fracture of rock，thelonger the time of fracture or not fracture，and the higher stress strength ratio，the higherthe effect of time-dependent deformation and fracture of rock，the shorter the time offracture. The above results show that，with the increasing of confining pressure or stressstrength ratio，microscopic time-dependent evolution mechanism of rock is essentiallycharacterized by tensile crack control mechanism and shear crack friction controlmechanism，the more tensile cracks， the less shear cracks，or the less tensile cracks，the more shear cracks.5．Through numerical creep test of marble under different gradations loading，thispaper studies the affect of different gradations on time-dependent deformation andfracture of rock. Results show that: the more gradations，the lowerer the effect oftime-dependent deformation and fracture of rock，the longer the time of fracture.