Evolutionary characteristics of microcracks in rocks under weak dynamic disturbance and disaster prevention and control
[Objective]High stress with superimposed weak dynamic disturbance serves as a critical factor including rock bursts.However,the microcrack propagation characteristics and energy dissipation pattern of rocks under different disturbance amplitude,frequencies,and unloading ranges remain unclear,leading to a lack of technical support for rock burst prevention and control.[Methods]Based on the true triaxial unloading dynamic disturbance tests,this study ana-lyzed the instability failure patterns of deep surrounding rocks under different disturbance amplitude(5,10 MPa),fre-quencies(4,10 Hz),and triaxial stress unloading(0,12 MPa).Moreover,this study examined the characteristics of mi-crocracks in rocks using scanning electron microscopy(SEM).Through bolt pull-out tests,this study enhanced the en-ergy-absorbing support effects of bolts by optimizing the rib spacing and height of bolts.Accordingly,it proposed a combined support technique integrating energy-absorbing bolts,low-impedance concrete grouting,guniting,and screen-ing.Additionally,the pressure and vibration data of roadways before and after treatment were obtained through long-term monitoring using sensors.[Results and Conclusions]Key findings are as follows:(1)With an increase in disturb-ance amplitude and frequency,cracks increased significantly and irregularly,and the fractal dimension of rock fracture direction decreased.In the case of disturbance of 10 MPa and 10 Hz,the fractal dimension decreased to the lowest value of 0.62,with the orientation frequency of pores at angles ranging from 80° to 120° reaching the maximum value of 52%,which was about 1.68 times that of the original rocks.This finding suggests that the uneven stress distribution of rock particles after disturbance led to stress concentration and pronounced fracture direction.(2)With an increase in disturb-ance amplitude and frequency,the micropore areas revealed by SEM images shifted from a rapid growth to a slow growth,with the increasing amplitude decreasing gradually.Every increase of 2 Hz in disturbance frequency correspon-ded to an approximately 24.13%increase in the area of microcracks in rocks.(3)Field tests indicate that as the rib spa-cing and height of bolts increased,the pull-out curve pattern transitioned gradually from the elastoplastic,failure,and re-sidual stages sequentially to elastoplastic,microyield,extensive yield reinforcement,failure,and residual stages success-ively.Threaded steel bolts with a rib spacing of 48 mm and a rib height of 2 mm exhibited the optimal energy-absorbing effect.Field monitoring indicates that the roadway pressure can be stabilized at about 36 N and the peak ground acceler-ation can be controlled at less than 8 000 mm/s2.This study reveals the surrounding rock failure and energy release pat-terns under unloading dynamic disturbance and proposes the combined support technique integrating energy-absorbing bolts,low-impedance concrete grouting,guniting,and screening,serving as a theoretical guide for similar deep engineer-ing.
true triaxial testrock burstscanning electron microscopy(SEM)microcrackenergy-absorbing boltweak dynamic disturbance
万方数据
维普
