Research On Rock AE Kaiser Effect Under Point Loading Via Ae Test And Numerical Simulation

In-situ stress is the main factors used in the designing of underground mining,a large amount of researches have been carried out on the testing of in-situ stress.However,there is still a lack of a simple and convenient in-situ stress measurement method at present.Based on the theory of acoustic emission measurement method,this paper have a research on the rock Kaiser effect under point loading via home testing and numerical simulation in order to verify its feasibility.The conclusions are followed:(1)According to the “suggesting method” of point loading testing made by the international rock mechanical academy,red sandstone specimens have been made and the wave velocity has been tested.Then,based on the uniaxial testing result.,2MPa~24MPa are determined for the stress classification of the Kaiser existing test.(2)Verifying the existing of rock Kaiser effect in red sandstone.The cyclic loading and unloading testing have been carried out and the AE signals have been analyzed.The results show that there existing Kaiser effect in red sandstone.(3)Analyzing the variation of AE count and energy during the progress of point loading after different plane loading.Under the same loading rate,it shows that the larger the plane loading,the mutation point of AE count and energy appears later and on the contrary,earlier.(4)Using the numerical simulation software PFC built the testing model of the same size with red sandstone specimen.And the corresponding physical and mechanical parameters of the wall unit,the particle unit and the contact element are given respectively.(5)Verifying the feasibility of the simulation model.Firstly,the uniaxial testing was simulated and it showed that its peak stress was 50 MPa,according with the home testing result.Secondly,point loading testing was simulated and it showed that it appeared tensile failure,according with the home testing result.The simulation results show the model is feasible.(6)On the elastic range,the point loading after different plane loading was simulated and had a research on the model of its internal fractures' development and its stress variation.The simulated result shows that: from the view of time,the larger the previous plane stress,the later of the fracture account' mutation point appeared.And from the view of stress,the larger the previous plane stress,the larger the uniaxial stress needed for the fracture's mutation.