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.

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.

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.

The correct assessment of slope stability under seismic loading requires not only the magnitude of ground acceleration to be considered but also its frequency content. In this study, a hybrid finite element/limit equilibrium (FEM–LEM) approach is used to quantify how the dominant frequency of harmonic ground motion affects the dynamic factor of safety, FSdyn, of a large homogeneous slope. Dynamic stresses are computed in QUAKE/W and transferred to SLOPE/W, where a FS calculation is performed at each time step to obtain FS_dyn(t). A design-of-experiment framework is applied to explore combinations of peak ground acceleration and dominant frequency. The results show that FS_dyn is much more sensitive to dominant frequency than to acceleration amplitude within the analyzed ranges, with the strongest reduction in stability occurring with the low input frequencies. Comparison with conventional pseudo-static analysis demonstrates that pseudo-static factors of safety can significantly overestimate stability at low dominant frequencies, and frequency thresholds are identified above which pseudo-static results become closer to the hybrid solution for the studied configuration. Although the model is intentionally simplified (homogeneous, drained conditions and single-frequency excitation), the findings highlight that dominant frequency is a decisive control parameter and should not be neglected in the seismic assessment of large earth structures.

There has been growing interest in using underground locations for applications in various fields, including research. In Poland, for several years, attempts have been made to build an underground laboratory. For this purpose, selecting an appropriate location requires a detailed analysis of the level of natural radioactivity. The present study presents detailed characteristics of the natural background radiation in close vicinity to shaft L-VI of the Lubin mine, at the depth of 910 m (2275 m w.e.). The in situ measurement of the photon flux in the 7–3150 keV energy range was equal to 8.08 ± 0.90 cm⁻²s⁻¹, and the gamma-ray dose rate of 0.070 ± 0.010 µSv/h with the highest contribution from ⁴⁰K and ²¹⁴B isotopes. The thermal neutron flux measured using helium counters was equal to 4.2 ± 0.9 × 10⁻⁶ cm⁻²s⁻¹. The radon concentration in the air measured with the RAD7 monitor showed low values ranging from 0 to 15.3 Bq/m³. Laboratory measurements of rocks using alpha and gamma spectrometry techniques showed a significant variation in the concentration of ²²⁶Ra and ^234,238U isotopes, and the highest concentration values were recorded for shales. The ⁴⁰K, ^234,238U and ²²⁶Ra isotopes make the greatest contribution to the natural radioactivity of analyzed rocks.

Measurements of seismic activity induced by mining operations are a basic tool for assessing the level of dynamic load associated with the occurrence of tremors. Knowledge of the location of the source of vibrations and the nature of seismicity is the basis for the safe planning of operations and design of both underground and surface infrastructure. The key parameter influencing the quality and reliability of seismic measurements is the coverage density of the analysed area with measurement stations. Unfortunately, the cost of seismic networks using standard devices is so high that in most cases the density of the network is much lower than needed for a good resolution and low event detection threshold. A certain breakthrough in this area may be the introduction of cost-effective measuring devices based on MEMS technology. This study compares the seismic data collected with the use of MEMS-IMU accelerometers with standard accelerometers for field seismic monitoring. The basis for the comparison was the analysis of data recorded by both devices located on the same site for two months. The comparison was carried out in terms of the characteristics of seismic waveforms, their amplitude distribution, frequency characteristics and effective duration of vibrations. Based on the results of the analysis, it was shown that MEMS-IMU accelerometers can be successfully used to monitor seismicity induced by mining activities in the near wave field.