Relationship between spatial variability of rock strain and b value under splitting condition

In order to understand the fracture process of rock more deeply,the relationship between the spatial difference of rock deformation and the fractal dimension of acoustic emission under the condition of Brazilian splitting is presented in this paper. Because the rocks have the characteristics of heterogeneity and anisotropy,granite particles are large,complex fabric can better show the anisotropy of rocks,gray greenstone fabric is more exquisite and granite can be compared. As a kind of sedimentary rock,sandstone verifies the correctness of the test conclusions and increases the universality of the test conclusions. Granite,diabase and sandstone are investigated with the help of Brazilian splitting test. Through the arrangement of strain gauges in the upper,middle and lower regions of the disk splitting axis,the strain spatial variation coefficient is defined by using the discreteness statistics of the measured values of three groups of strain gauges. At the same time,combined with the AE monitoring data,the fractional dimension b value of AE amplitude is obtained. Compared with the two values,it is found that the relationship between the spatial variability of rock strain and the fractal dimension of AE amplitude is as follows:①In the process of rock splitting,the variation trend of strain spatial variation coefficient with loading process is opposite to that of AE amplitude fractal dimension b,and the Pearson correlation coefficient is between -0.756 and 0.931 8. By means of experiments,it is proved that there is a significant negative correlation between the fractal dimension of AE amplitude and deformation dispersion. ②The b value is the manifestation of the deformation disharmony between the rock regions in the fracture release energy. The stage of local rupture or global rupture with the increase of coefficient of variation corresponds to the stage of decrease of b value,and the stage of basic invariance of coefficient of variation corresponds to the stage of basic stability and invariance of b value,which indicates that the spatial deformation is in the stage of adaptive coordination and consistency. The decreasing stage of coefficient of variation corresponds to the rising stage of b value,which indicates that the deformation of each region is in the stage of transformation from incoordination to coordination and consistency. ③Limited by the statistical method,the b value is often the average result in a period of time. Before each large rupture vibration,there will always be a quiet period,so the improper selection of time window can easily lead to the ups and downs of the statistical results of b value,and the beating trend of b value often brings confusion. The coefficient of variation of deformation is a real-time monitoring value,and its changing trend is stable,which can achieve the same monitoring effect as the b value,and avoid the statistical defects of the b value. ④The b value and spatial variability of strain between rock regions confirm each other,and both of them can be used as a representation of rock fracture to reflect the homogeneity of rock fabric and the process of rock fracture. In theory,the variation of b value in earthquakes and mine microearthquakes should also be related to the coordination of deformation between seismogenic regions,so the monitoring of interregional deformation coordination can also be used as one of the indexes of large earthquake prediction and can reflect the rupture process in real time.