Fractured Rock Mass Destruction Based On AE-DIC Monitoring Study On The Precursor Identification Test

As a typical heterogeneous and anisotropic material,it is difficult to establish a uniform destruction standard for rocks under different conditions.In view of the complex and changeable conditions of coal seam occurrence in China,the geological environment,mining technology,technical equipment and management level of different mines are different,and the disaster types,occurrence laws,influencing factors and precursor modes of mines have their own characteristics.Many mines with the expansion of mining scale and mining depth increase,mining conditions change,the form of disaster also change.Single signal monitoring has been unable to meet the needs of complex geological and mining environment,need to apply a variety of a variety of monitoring means joint analysis of multiple precursor factors,based on acoustic emission signal characterization of rock internal damage and DIC technology characterization of rock surface damage,a comprehensive understanding of rock internal crack initiation,accumulation and expansion process,the diversity of precursor information to provide accurate early warning of disaster significance.Local should change as a precursor of rock damage,its evolution process can effectively reveal the new crack gestation,expansion process,as the loading stress continuous strain field with the deepening of stress concentration of strain localization belt more significantly,and with the emergence of cracks and widening and extension,digital image related technology from the fine level to realize the quantitative description of rock microscopic damage evolution.Considering the load of rock deformation and damage is energy driven progressive damage process,the stress and the deformation can not reflect the evolution of the rock internal damage problem,this paper combined with the advantages of DIC technology and acoustic emission technology to monitor the crack rock damage process under different loading rates,the main research results are as follows:(1)Under different loading rates,the mechanical properties of the test have certain significant differences,and the stress strain curve falls periodic after the low load rate,namely "unloading platform";under the high load rate,the test shows brittle damage,and the peak stress drop shows "cliff" drop,with the possibility of rock explosion.(2)Under the low load rate,the specimen can transfer the load to the end of the specimen in time,and has various kinds of new cracks,which is conducive to elastic strain energy storage.However,with the increase of the loading rate,the form of specimen failure is mainly shear failure,and the elastic strain energy storage rate is reduced,and the elastic strain energy is characterized by concentrated release.(3)In the whole process of specimen failure,the acoustic emission energy rate and ringing counting rate from energy and signal activity degree of specimen internal damage,with the increase of the loading rate of specimen damage form from plastic dissipation to brittle damage,stress-strain curve from peak after "stage unloading" to "transient discharge" the corresponding acoustic emission signal from "group shock" type to "solitary shock" type.By comparing the corresponding relationship between the acoustic emission signal and the stress curve under the influence of different loading rates,it is found that the acoustic emission signal "frequency period" and the stress peak point have a time sequence relationship,which has a precursor characteristic for predicting rock mass instability and destruction.(4)The distribution and evolution of the local area should change band have a good intuition in the gestation and expansion of the positioning cracks,and the local tip finger should change in the band(5)The standard deviation is an element reflecting the dispersion degree of the array,and the global strain dispersion degree is calculated during the strain field evolution by extracting the original data of the strain field,and the standard deviation and differentiation coefficient are introduced to describe the temporal dispersion degree of the strain field.The differentiation coefficient CV has the trend of accelerated rise before the stress curve falls,which can realize the early warning of rock mass disaster in time.At the same time,the similar degree between the standard deviation curve and the separation coefficient curve can effectively determine the type of stress field that is the dominant rock mass damage.(6)The DIC technology is used to arrange the observation points at the prefabricated crack end.Compared with the traditional stress gauge measurement,the non-contact measurement avoids the constraint influence.By monitoring the change of the stress of the observation point at the fissure end in real time,the cracking position and damage type of the prefabricated crack end can be timely determined.This method has strong sensitivity and is earlier than the warning of "frequency period" and separation coefficient warning in the warning time.(7)Using the personality characteristics of crack rock fracture precursor factor under different loading rates,according to the corresponding relationship between signal characteristics such as acoustic emission signal activity,strain field dispersion and the specimen damage process,the AE-DIC precursor information chain warning rock damage for loading rate effect,jointly monitors the whole process of rock damage evolution,improve the accuracy of rock disaster warning,and solve the one-sidedness of single signal monitoring.Figure 35 Table 4 Reference 94...