Analysis On Shear Properties Of Through Discontinuity And Stability Of Slope With Through Discontinuity

Rough discontinuity can be often seen in the hard rock natural slope andexcavation slope, whose shear properties have an important effect on slope stability. Butfor the moment, the direct shear tests and site sampling are difficult to implement, largesize shear tests of discontinuity are hard to achieve. This paper relied on the YouthScience Fund(No.41172243) of National Natural Science Foundation, based on fieldinvestigation and survey and high precision of3D laser scan of fracture plane ofunloading tests, the micro-macro surface roughness of discontinuity is investigated;Based on the theory of particle flow, the influence of inclination angle of saw-tooth andnormal stress for saw-tooth discontinuity and the influence of ratio of height to length ofstep for step-shaped discontinuity on shear deformation and strength for throughdiscontinuity is investigated using2D particle flow code (PFC2D) simulation. Theempirical equation from research are applied to slope stability limit equilibriumcalculation. The research results have enriched shear properties of discontinuity andparameter selections and can aslo function as important reference for estimated strengthparameters of saw-tooth and step-shaped discontinuity. The major research findings aredescribed as follows:①The morphology of discontinuity is classified as saw-tooth、step-shaped、flatand wavelike. The roughness of discontinuity is a system with variance self-similaritywhich can be described by its variance σ2Dand σ3D. The roughness of discontinuity isproportional to its variance and variance is a quantitative index for the roughness ofdiscontinuity. The frequency histogram of marble roughness height shows that thedistribution law of marble roughness height is similar to normal distribution law, theskewness of roughness height is almost negative，roughness height distribution is moreon the right.②For saw-tooth discontinuity, the shear deformation modes include three basictypes: climbing along saw-tooth, climbing-gnawing and shearing-gnawing. The modesgradually evolve from climbing and climbing-gnawing to shearing-gnawing with theinclination angle and normal stress increasing, and the conversion of these modesapproximately presents symmetric matrix distribution with their increase. The shearstrength almost linearly increases with inclination angle and normal stress. Takingclimbing and gnawing effects into account at the same time, an empirical equation for shear strength of saw-tooth rock discontinuity is established and checked by an instanceof slope stability calculation.③For step-shaped discontinuity, the damage-failure modes of rock step can beconcluded into two basic types: compression-shear failure, tension-shear failure. Withthe increase of the H/L of the rock step, the damage-failure mode gradually evolvesfrom compression-shear to tension-shear failure. For both modes, macroscopic crackfirst appeared at the root of the rock step, the difference of the crack growth orientationslead to the different models. For the H/L of a rock step in the actual slopes is often smallrelatively, an empirical shear strength equation is established in which the both effectsof climbing along shear surface and the rock step gnawed are considered.④The empirical equation for shear strength of saw-tooth rock discontinuity andstep-shaped rock discontinuity are applied to slope stability limit equilibriumcalculation and parameter selections; Based on strength reduction method of FLAC3Dand limit equilibrium method, slope failure of saw-tooth rock discontinuity andstep-shaped rock discontinuity are simulated; Comparing the calculation results of limitequilibrium method and strength reduction method, the correctness of empiricalequations are testified.