Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring
Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring
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DOI：
10.1785/0120130286
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发表时间：
2014-08
影响因子：
3
通讯作者：
D. Becker;B. Cailleau;D. Kaiser;T. Dahm
中科院分区：
文献类型：
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作者：
D. Becker;B. Cailleau;D. Kaiser;T. Dahm
采矿活动可能引起不同类型的地震活动和岩石破坏。典型的地震事件包括：（1）由于高应力集中（边界断裂），在靠近廊道和人类活动的地方完全诱发的微震;（2）在距离应力扰动源（内部断裂）较远的岩体内触发的地震。类型1对于了解岩爆的发展和评价矿井的稳定性是重要的。第2类可能与释放预先存在的应力并由采矿作业引起的应力变化触发的较大事件有关。它们对评估与采矿活动有关的地震危险性很重要。为了分析这些不同的故障过程，我们使用了一个废弃盐矿中监测到的高频声发射（AE）事件数据集。岩体中裂隙的形成过程因孔洞的存在而增强。通过有限元方法模拟由热应力操作引起的热应力，并使用观察到的AE活动来量化库仑失效模型中的事件触发机制。有两点意见值得注意。首先，检测到增强活动的瞬时触发以及距离回填空腔相对较远的内部裂缝的缓慢生长。在再填充开始之前，结构已经显示出AE活动，并由牵引样应力转移触发。其声发射活动与计算的库仑应力变化在开始的蠕变。其次，观察到回填廊道处突然发生宏观诱发边界断裂，其方向与作用应力场一致。虽然内部断裂处的AE活动是由微小的库仑应力变化触发的，表明结构已经处于临界状态，但边界断裂的形成需要显著更大的应力，暗示先前完整的岩石体积。在线材料：描述不同前角值下内部裂缝上静态库仑应力变化的可变性的图。
Abstract Mining activity may cause different types of seismicity and rock failure. Typical events include (1) fully induced microearthquakes in close proximity to galleries and human activity due to high‐stress concentrations (border fractures) and (2) triggered earthquakes within the rock mass at larger distance to the source of the stress perturbation (inner fractures). Type 1 is important to understand the development of rock bursts and evaluate the stability of the mine. Type 2 may be associated with larger events releasing pre‐existing stress and being triggered by stress changes due to the mining operation. They are important to assess the seismic hazard related to mining activity. To analyze these different failure processes, we use a dataset of high‐frequency acoustic emission (AE) events monitored in an abandoned salt mine. The process of fracture formation in the rock mass was enhanced by the backfilling of a cavity. Thermal stresses induced by the backfilling operation are modeled with a finite‐element approach, and observed AE activity is used to quantify the mechanism of event triggering in terms of a Coulomb failure model. Two observations are outstanding. First, the instantaneous triggering of enhanced activity and the slow growth of an inner fracture in relatively far distance to the backfilled cavity is detected. The structure already showed AE activity before the refilling started and was triggered by traction‐like stress transfer. Its AE activity correlates well with the calculated Coulomb stress changes at the beginning of backfilling. Second, the sudden occurrence of a macroscopic, induced border fracture at the backfilled gallery which is oriented in agreement with the acting stress field is observed. Although AE activity at the inner fracture was triggered by tiny Coulomb stress changes, indicating a structure already in critical state, formation of the border fracture required significantly larger stresses, hinting at a previously intact rock volume. Online Material: Figure depicting the variability of the static Coulomb stress changes on the inner fracture for different rake values.