Hao Yuxin, Song Xuepeng, Huang Yucheng, Zhang Bao, Dong Zilin, Wang Hao
School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China.
Technical and Economic Research Institute of National Energy Group, Beijing, 102211, China.
Environ Sci Pollut Res Int. 2022 Dec;29(60):90686-90702. doi: 10.1007/s11356-022-22154-1. Epub 2022 Jul 23.
The cemented paste backfill (CPB) has a significant loading rate (LR) effect. The damage evolution process of CPB is closely related to the characteristics of acoustic emission (AE). This paper analyzes the damage evolution law of the filling body under different loading rates using indoor test and numerical simulations. We introduce the moment tensor theory to simulate the AE characteristics of the whole process of filling loading and explore the LR effect of the backfill with the help of the energy conservation. The results indicate the following: (1) when LR increases from 0.1 to 2 mm/min, the UCS of the backfill first increases and then decreases, contributing to the occurance of the critical LR. (2) There are no microcracks occurred in the backfill at the initial stage of loading, and the microcracks increase slowly, which is not obviously affected by LR. After the peak value, the microcracks in backfill expand and propagat rapidly to form mesoscopic cracks. (3) The mesoscopic AE events based on the moment tensor theory are in good agreement with the laboratory tests results, which can be divided into the initial period, quiet period, slow raising period, rapid raising period, and rapid falling period. (4) The temporal and spatial distribution characteristics of AE are consistent with the evolution law of microcracks. There are fewer AE events before the peak value, and AE events increase significantly and frequently with large magnitude events after the peak value. AE events dense zone and AE events with larger magnitude increase under higher LR. (5) Besides, the boundary energy and dissipation energy also gradually increased; at the same time, the strain energy first increased and then decreased. The results can provide a reference for understanding the damage evolution characteristics of backfill by different LR and AE mesoscopic simulation.
胶结膏体充填体（CPB）具有显著的加载速率（LR）效应。CPB的损伤演化过程与声发射（AE）特性密切相关。本文通过室内试验和数值模拟分析了不同加载速率下充填体的损伤演化规律。引入矩张量理论模拟充填加载全过程的AE特性，并借助能量守恒探讨充填体的LR效应。结果表明：（1）当LR从0.1mm/min增加到2mm/min时，充填体的单轴抗压强度（UCS）先增大后减小，出现了临界LR。（2）加载初期充填体内未出现微裂纹，微裂纹缓慢增加，受LR影响不明显。峰值后，充填体内微裂纹迅速扩展并形成细观裂纹。（3）基于矩张量理论的细观AE事件与室内试验结果吻合良好，可分为初期、平静期、缓慢上升期、快速上升期和快速下降期。（4）AE的时空分布特征与微裂纹演化规律一致。峰值前AE事件较少，峰值后AE事件显著增加且频繁出现大震级事件。较高LR下AE事件密集区和较大震级AE事件增多。（5）此外，边界能量和耗散能量也逐渐增加；同时，应变能先增加后减小。研究结果可为理解不同LR下充填体损伤演化特征及AE细观模拟提供参考。
