Identification Of Rock Dynamic Damage State Based On Acoustic Emission

In the process of construction and long-term operation of rock mass engineering,the major ground pressure disaster accidents caused by rock damage show a rapid upward trend.Therefore,the dynamic damage simulation experiment of marble was carried out.First,flawing detection imaging in rock internaland and drawing velocity nephogram based on acoustic emission AST function.Then,clustering the signals and selecting the key signals which could describe the damage characteristics well.Finally,based on the damage curve extracted,the relationship between the acoustic emission signal group and the key characteristics of rock dynamic was established.A method of inversion and identification of rock damage evolution state by acoustic emission signal characteristics was proposed,and the main conclusions were as follows.1)AE velocity slice nephogram could better reflect the dynamic evolution process.Damage variable D was calculated by weighting the region with wave velocity threshold.Combining damage variable curve and wave velocity nephogram could effectively quantify the dynamic evolution process of rock fracture process.2)AE signals could be classified into four categories: A,B,C and D by decision tree model.Among them,type A signal corresponds to the extended fracture of rock caused by macro-fracture.Type B signal was cracking and expanding cracking before and after macro-cracking.Type C signal was slip fracture before macro-fracture of rock.Class D signals were small-scale burst signals generated and extended by micro-cracks in rocks.This signal could be eliminated when describing the dynamic damage process of rock.3)The time distribution of A,B and C in rock dynamic damage process had obvious stages.By calculating the time intensities of various key damage signals,the abnormal damage section,fracture compaction and stable damage propagation stage in rock fracture could be effectively identified.The research results provided a new method and basis for the application of acoustic emission in monitoring and early warning of rock dynamic damage.Figure23;Table10;Reference 61...