| At present,with the development of economy,water conservancy,transportation,mining and other projects continue to extend to the depths of the underground,and marching into the depths of the earth is a strategic scientific and technological problem that we must solve.However,natural disasters such as rock bursts and slab cracks are still frequent geological disasters during the construction of deep underground projects.Therefore,only by grasping the essential failure characteristics of the rock mass and clarifying the failure mechanism of the engineering rock mass under different stress paths can we reasonably predict the strength,deformation and failure characteristics of the engineering rock mass.This paper adopts high voltage servo dynamic rigid real triaxial testing machine to carry out uniaxial compression test,the biaxial compression test and single airport rockburst test,in each of the test based on the analysis of the acoustic emission signal,analyzes in detail the test damage evolution law of rock failure process,constructed based on the acoustic emission of granite under uniaxial and biaxial compression damage constitutive model,and analyzes the granite rupture instability precursor to acoustic emission characteristics,the main research contents and conclusions are as follows:1.A study on the constitutive model of acoustic emission damage of coarsegrained granite under uniaxial compression was carried out.The damage variable is constructed by counting the acoustic emission ringing of granite under uniaxial compression.The damage constitutive of different rocks under uniaxial compression is quantitatively analyzed and compared.On this basis,a more reasonable uniaxial compression is derived with the help of damage mechanics theory.Constitutive model of granite damage.Aiming at the problem that the traditional model fails to consider the impact of the compaction stage on the stress-strain curve,the compaction coefficient is introduced to reflect the "downward bending section" of the stress-strain curve during the initial stage of loading.The acoustic emission damage constitutive model of crystalline granite realizes the accurate characterization of the constitutive relationship of coarsegrained granite under uniaxial compression.2.The constitutive model of acoustic emission damage of coarse-grained granite under biaxial compression was studied.The test results show that the intermediate principal stress has a significant impact on the peak strength and damage evolution process of the rock under biaxial compression.In view of the limitation that the traditional acoustic emission damage constitutive model cannot fully reflect the intermediate principal stress effect,it is proposed to consider the intermediate principal stress.The acoustic emission damage constitutive model of coarse-grained granite under biaxial compression based on stress effect realizes the reasonable acoustic emission characterization of the constitutive relationship of coarse-grained granite under biaxial compression.3.Studies on the precursor of acoustic emission instability of coarse-grained granite have been carried out and the precursor characteristics of plate fracture and rockburst of coarse-grained granite have been found.Single airport true triaxial test results show that the buckling model for rockburst or coarse-grained granite plate crack,among them,the instability of rockburst based on acoustic emission precursor is: once the number of AE hit or ringing count rate index rises abruptly after a sudden drop again,such as a "quiet period","quiet period" during a small hit to the low frequency and high amplitude shear fracture acoustic emission signal(AF/RA < 10)continue to increase.The precursor of plate fracture instability based on acoustic emission is: while the fractal dimension of AE impact number time and AE b-value show a continuous decline trend,there is an intermittent sudden increase of high-frequency impact point or ringing count rate. |
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