Evolutionary characteristics of microcracks in rocks under weak dynamic disturbance and disaster prevention and control

Authors

JIANG Mingwei, China Coal Research Institute, Beijing 100013, China; CCTEG Shenyang Research Institute, Fushun 113000, ChinaFollow
LIANG Yuntao, China Coal Research Institute, Beijing 100013, ChinaFollow
FENG Wenbin, CCTEG Shenyang Research Institute, Fushun 113000, China
LI Haitao, Deep Mining and Rock Burst Research Branch, Chinese Institute of Coal Science, Beijing 100013, China
ZHOU Rui, CCTEG Shenyang Research Institute, Fushun 113000, China
GUO Baolong, College of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266000, China
LIU Yang, Deep Mining Laboratory of Shandong Gold Group Co., Ltd., Yantai 266000, China
MA Ju, School of Resources and Safety Engineering, Central South University, Changsha 410083, China

Abstract

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 analyzed the instability failure patterns of deep surrounding rocks under different disturbance amplitude (5, 10 MPa), frequencies (4, 10 Hz), and triaxial stress unloading (0, 12 MPa). Moreover, this study examined the characteristics of microcracks in rocks using scanning electron microscopy (SEM). Through bolt pull-out tests, this study enhanced the energy-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 screening. 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 disturbance 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 disturbance 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 corresponded to an approximately 24.13% increase in the area of microcracks in rocks. (3) Field tests indicate that as the rib spacing and height of bolts increased, the pull-out curve pattern transitioned gradually from the elastoplastic, failure, and residual stages sequentially to elastoplastic, microyield, extensive yield reinforcement, failure, and residual stages successively. 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 acceleration can be controlled at less than 8000 mm/s². This study reveals the surrounding rock failure and energy release patterns 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 engineering.

Keywords

true triaxial test, rock burst, scanning electron microscopy (SEM), microcrack, energy-absorbing bolt, weak dynamic disturbance

DOI

10.12363/issn.1001-1986.24.04.0277

Recommended Citation

JIANG Mingwei, LIANG Yuntao, FENG Wenbin, et al. (2024) "Evolutionary characteristics of microcracks in rocks under weak dynamic disturbance and disaster prevention and control," Coal Geology & Exploration: Vol. 52: Iss. 10, Article 16.
DOI: 10.12363/issn.1001-1986.24.04.0277
Available at: https://cge.researchcommons.org/journal/vol52/iss10/16

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