A roof fall hazard is still one of the major threats in the underground mining industry. Each such type of event always brings great risk to miners and causes serious interruptions in the process of rock excavation. In general, the possibility of roof fall hazard occurrence is directly related to the local geology, the presence of horizontal stresses as well as the type of excavation method and the efficacy of the utilized roof support. Due to the complexity of this process, it is important to continuously evaluate the roof fall risk, especially in long life-time places where a mining crew is often present. Within this article, a detailed review of the current methods of monitoring and evaluating roof fall risk was presented. Based on the extensive literature survey, different types of devices were described, and their advantages and disadvantages were pointed out. Furthermore, new trends in the area of roof fall risk monitoring were described and discussed.
The paper presents the results of long-term continuous measurements of the deflection of the roof layers in the underground copper mine Polkowice-Sieroszowice, Poland belonging to KGHM Polska Miedź S.A. The measurements were performed with the use of the inclinometric method consisting of continuous registration of changes in the angle of inclination of the roof strata. The measurements were carried out using an inclinometer sensor fixed to the end of a rockbolt in the roof. Measurements presented in the article were made in various regions of the underground mine. The monitoring covered: The exploitation front, machinery chamber and the region of the experimental longwall mining of copper ore. The obtained results proved the usefulness of the developed method in the process of the evaluation of the stability of mining excavations. The sensors were highly sensitive and performed the measurements in a simple way; highly accurate and reliable results were obtained.
Proper monitoring of seismic risk and reliable evaluation of destress blasting efficiency requires a well-developed seismic network surrounding the analyzed area. Unfortunately, the construction of a dense seismic monitoring system using standard types of seismometers and accelerometers is associated with high costs of seismic network development and maintenance. Significant improvements in this regard may be potentially achieved by replacing expensive monitoring devices with other cost-effective sensors such as MEMS-based accelerometers. Nevertheless, this topic has not been sufficiently investigated yet, and the usefulness of such devices for monitoring seismicity in deep underground mines has not been recognized. The goal of this paper was to perform preliminary measurements of blasting-induced seismicity in the near-wave field with the use of a single three-axial MEMS-based accelerometer and three uniaxial seismometers. The collected seismic records induced by multi-face blasting were compared in time and frequency domains. In the time domain, the values of 3D peak motion plots were analyzed, and the possibility of identification of subsequent delay times in recorded waveforms was investigated. In the case of frequency distribution, the Power Spectrum Density plots were calculated and compared. The results of the analysis proved that MEMS-based accelerometers provide reliable results and may be successfully implemented for regular use in underground seismic monitoring systems.
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