Acoustic Emission Test And Numerical Simulation Of Limestone Triaxial Compression

In order to further study the fracture regularity of limestone in the right side slope of S203 highway K43+090~K43+240 in Shanyang county,Shanxi province,it provides reliable theoretical support for acoustic emission technology application in its stability analysis and monitoring and early warning,in this paper,a three-axis compression acoustic emission test is carried out for the limestone samples collected from the slope of the highway,and obtain the parameters such as stress-strain curve,ultimate compressive strength,acoustic emission ringing count and energy count,etc of limestone under triaxial compression,as well as the internal rules and relations,after that using the particle flow program PFC~2DD based on the discrete element to construct the constitutive model of the actual test of the limestone rock sample under triaxial compression,the microscopic parameters of the constitutive model were calibrated according to the actual macroscopic parameters of the rock,compared with the laboratory test results,the numerical model is considered to reflect the indoor test.Test results can be obtained from indoor acoustic emission:(1)In the triaxial compression state,the ultimate compressive strength of the rock sample is increased due to the existence of confining pressure,but the acoustic emission activity in the compaction and elasticity phase is relatively reduced;(2)Rock fractures undergo compaction-elastic-fracturing during triaxial compression,but not every rock sample has the plastic stage,it is determined by the nature and internal structure of limestone itself,from the test results,there is a greater probability of plasticity in fractured rock samples;(3)The acoustic emission activities of rock samples in the three-axis state including the crack closure period-the development period-the fracture period,but only the SH8 rock sample shows a period of calm,calm period can serve as a precursor to rock fracture;(4)Due to the existence of confining pressure in the triaxial state,the schedule of the maximum occurrence of the acoustic emission activity of some limestone samples appears to be hysteresis,that is,the maximum value of ae signal occurs after the rock sample is broken.The following results were obtained from numerical simulation tests:(1)The simulation of mechanical characteristics of dense and fractured rock samples includes calculation of peak stress,fitting of stress-strain curve,and fitting of each fracture phase of rock sample;(2)The simulation of rock fracture surface is consistent with the experimental results,the actual and simulated final fracture morphology of the compacted rock sample SH5 is both oblique and penetrating,both the actual and simulated fracture morphology of the fractured rock sample SH7 are both"one long and one short"double crack damage;(3)The trend simulation of acoustic emission signal of rock samples includes the development process fitting and hysteresis of the signal,which is consistent with the actual test.In addition to,this study also plays an important role in the early warning of instability and failure of rock slope.