Study On The Whole Process Of Rock Slope Failure Based On Strength Reduction Hybrid Finite-discrete Element Metho

With the rapid development of economy in China,considerable rock slope failure cases occur due to an increasing number of human activities.It not only leads to serious economic loss,but also threats the safety of public.Therefore,it makes sense of deeply researching entire process of rock slope failure.At present,there are two common numerical methods to analyze the slope problems,which are continuum methods and discontinuum methods.Continuum methods in which rock material is regarded as continuum body can be used to reflect the stress and strain and identify the place of failure face before the failure of rock slope.With the further development of failure,rock would be discretized to be tons of rock blocks.In this case,discontinuum methods in which rock material is regarded as discontinuum body are more suitable to simulate the interaction between rock blocks.However,because of different assumption to rock material,continuum and discontinuum methods have their own limitations in handling the entire process of rock slope failure.Therefore,in order to reliably simulate the failure process of rock slope,based on the strength reduction method,the general-purpose graphic-processing-unit(GPGPU)-parallelized Hybrid Finite-Discrete Element Method(HFDEM)is proposed.The specific research contents are concluded as follow:(1)The achievement of different functions in HFDEM.In order to really simulate the change process of rock from continuum to discontinuum,3 types of rock failure mode are set in the HFDEM.The energy release rate of the 3 failure modes can be regarded as factors to determine the situation of rock and further achieve the transition from continuum to discontinuum.In addition,the algorithms of contact detection and interaction were embedded in the HFDEM in order to identify and handle interactional rock blocks efficiently.Furthermore,the strength reduction method based on tensile and shear failure was employed in the HFDEM to reduce rock mass strength and achieve rock slope failure.(2)Verification of the HFDEM.Several granite samples were used in rock mechanism tests,including Uniaxial compression test,Brazilian tensile strength(BTS)test,and Direct shear test.The properties of granite obtained in tests were input in the HFDEM in order to simulate the BTS test.The simulating results of the HFDEM were compared with experimental tests and theory results.From macro and micro perspectives,the comparing results verified that the proposed method has the ability to capture the entire fracture process of rock.(3)Simulation and comparison of homogeneous rock slope’s typical planar sliding failure entire process.At first,The HFDEM was used to simulate entire process of a homogeneous rock slope with a slope angle of 85°,from the beginning situation under gravity,through the generation,coalescence and propagation of rock cracks,to the fracture,sliding,rotation,rebound and interaction of rock blocks as well as finial shape and size of fragment piles.In addition,several monitoring points were arranged to study the movement speed and displacement magnitude of rock blocks in different parts.Finally,through comparing the modelling results of the HFDEM with experimental result and results of other methods,it was verified that the strength reduction method can be applied in the HFDEM well and the proposed method has superiorities in simulating the entire process of rock slope failure.(4)Analyzing the effects of discontinuity on the stability and failure process of rock slope.Two 75° angle’s rock slopes model are built and compared,one slope has a discontinuity and another has not discontinuity.The HFDEM based on the strength reduction method was used to simulate the failure process of above two slopes,including the beginning situation,failure face shape,safety factor,movement speed and displacement magnitude of rock blocks as well as shape and size of fragment piles.The results showed that the exist of a discontinuity can affect the stability of a slope obviously,even directly change its failure behavior.(5)Analysis of actual engineering cases.Take abandoned mine slopes as examples,4 slopes with different shapes and sizes were built.The HFDEM based on strength reduction method was employed to simulate 4 slopes’ beginning situation,failure face and safety factor,movement speed and displacement of rock blocks as well as the size of fragment piles.The comparing results showed that the stability of No.1 slope is best,and its effect after failure is relatively minimal.No.4 slope has the worst stability and has the largest impact on the downstream area after failure.Thus it can be seen that the proposed HFDEM based on strength reduction method can be used in engineering.It can not only determine stability of slopes,but also predict seriousness after slopes failure.