Influences Study of Loading Rate on the Failure Characteristics of Crack Grouting Mass

In order to study the influences of excavation rate on the failure mechanism of grouted rock mass, loading and monitoring tests were carried out on sandstone fractured grouts by using rock rigidity testing machine and acoustic emission equipment, and the mechanical properties of grouts and the temporal and spatial evolution characteristics of acoustic emission under the influence of different loading rates and different fracture inclination angles were studied. The results show that: with the increase of loading rate, the peak strength of grouted specimens with the same crack inclination gradually increases, and the peak strength of grouted specimens is lower than that of intact specimens. When the dip angle of the crack is 15°~45°, the peak strength of the grout specimen is mainly affected by the increase of loading rate. When the crack inclination angle is 60°, the peak strength is mainly affected by the crack inclination angle, and the change law with the increase of loading rate is opposite. The deformation modulus of grouting body is basically consistent with the change characteristics of peak strength, and the elastic modulus generally shows a downward trend, and the influence of crack inclination angle on the elastic modulus of grouting body specimen is greater than the loading rate. Taking the fracture dip angle of 45° as an example, the corresponding relationship between acoustic emission ringing count and loading curve is analyzed. It can be found that the sudden drop of stress corresponds to the sudden increase of acoustic emission ringing count, but vice versa. The loading rate is closely related to the occurrence and duration of the "quiet period" before the peak. Acoustic emission incident points are mainly concentrated in the grouting consolidation body, and with the increase of loading rate, the number of incident points decreases gradually. This phenomenon can provide disaster prediction and theoretical guidance for the corresponding crack grouting rock mass engineering construction.