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Study of movement characteristics of a hard–thick stratum (HTS) affected by a fault in a coalmine is significant to predict the dynamic hazards (i.e., rock bursts and shock bumps) because of the particular structural and mechanical properties of the HTS and the fault. Hence, using UDEC numerical simulation, the movement characteristic of HTS and fault-slipping law with different mining directions towards the fault were studied. Then, two different inducing modes and corresponding mechanisms of rock burst were obtained. The results show that the structure of overlying strata on two fault walls is different because of fault cutting and fault dip; it results in the HTS of two fault walls presenting different movement stage characteristics. From analysis of fault plane stress and fault slipping, we obtain that footwall mining has higher risk of rock burst than hanging wall mining. Finally, summarizing two different inducing modes of rock burst affected by the HTS and the fault: one that mainly resulted from the strain energy release caused by the HTS obvious bending and failure (i.e., hanging wall mining) and one that notably affected by fault slipping and HTS failure subsidence (i.e., footwall mining). A field case regarding microseismic monitoring is used to verify the numerical simulation results. Study results can serve as a reference for predicting of rock bursts and their classification into hazardous areas under similar conditions.

The paper presents the study of the deformation processes development in unstable rocks of the hanging wall during mining a thick steeply dipping ore deposit in the example of the Yuzhno-Belozerskyi deposit. In the studied field, there are problems of stability of hanging wall rocks, represented by low-resistant shale rocks that do not withstand significant outcrops in time. A decrease in stability is manifested in the form of failure of the hanging wall rocks into the stope. Based on a detailed study of the ore deposit geological structure and the performance of the stopes mining, according to the survey data, an area of the deposit has been identified where the ore failure and dilution reach 4%–8% with a maximum value of 12%. This also makes it possible to determine the most important averaged source data for performing physical modeling on equivalent materials. It has been determined that the deformation value of the hanging wall rocks with subsequent failure into the stope and ore mass deformation in the sloping bottom change exponentially with an increase in the depth of the stope location, and the dynamics of increasing rock deformations in the hanging wall is noticeably higher than in the sloping bottom of the stope. This reduces the quality of the mined ore and increases the probability of rock failure area propagation to the hanging wall drifts with their subsequent destruction. The results of physical modeling are characterised by acceptable reliability and are confirmed by a high similarity with the actual data on ore dilution with broken rocks during the stopes development. It has been found that during the formation of a steeply dipping outcrop of stopes with an area of 1200 m2, unstable rocks of the hanging wall are prone to failure of significant volumes. For successful mining and achieving stope element stability, it is recommended to optimise its parameters, the height, width and the value of a steeply dipping outcrop, as well as to preserve the ore pillar in the hanging wall until the ore is broken and drawn from the rest of the stope.

Fault activation is a primary cause of rockburst in working faces of coalmines. To reveal the full-cycle impact gestation process, a numerical model consisting of a normal fault is established using FLAC 3D . The spatio-temporal evolution laws of the displacement field, stress field, strain field, and energy field of coal seam during the advance from hanging wall to footwall are obtained. Additionally, the energy level frequency division characteristics and the spatio-temporal distribution of the energy levels of microseismic signals during the working face crossing the fault are analyzed. The relationship between the risk level of fault-slip burst and microseismic information, stress field, strain field, and energy field around the fault region are established. This lays a foundation for implementing fault-slip burst risk classification control in deep working faces mining through faults. The results show that the distance between the working face and the fault significantly influences the energy concentration of the coal pillar, the rocks in footwall exhibiting a higher energy concentration than that in hanging wall. The spatial position relationship between the working face and the fault affects the failure mode of the coal and rock mass. The stress field, strain field, and displacement field of the coal seam and its roof or floor in the fault region show significant differences in sensitivity to the distance between the working face and the fault. Microseismic events indicate that fault activation can be divided into three stages: stress development, energy storage, and structural activation. During stress development and structural activation, there are more microseismic events and higher energy values. The microseismic energy of the working face is primarily concentrated within 10–20 m from hanging wall and throughout footwall of the fault. In addition, the pre-evaluation results of the impact risk of the working face prove that the evaluation model can effectively distinguish the leading role of different working face distances from fault. This provides reference and guidance for risk assessment of fault-slip bursts in deep working face mining through faults.

Structural analysis, petrochronology and metamorphic petrology enable identification and bracketing of the timing of a newly mapped high-temperature ductile shear zone (Jagat Shear Zone (JSZ)) in the Himalayan metamorphic core in Central-Western Nepal. In situ U-Th-Pb monazite petrochronology constrains the timing of top-to-the-S/SW shearing between 28-27 Ma and 17 Ma. Burial and prograde metamorphisms in footwall rocks were linked to thrust-sense movement along the JSZ, while the hanging wall rocks were retrogressed and exhumed. The identification and age of the JSZ (as part of a regional system of shear zones: the High Himalayan Discontinuity (HHD)) coupled with the localization and timing of activity of the Main Central Thrust (MCT) (i) fills a gap in tracing the HHD along orogenic strike, (ii) supports the identification of the position and timing of the long-debated MCT and (iii) helps to place the boundaries of the Himalayan metamorphic core and its internal architecture. Thus, our study is a significant step towards a precise identification of the burial, assembly and exhumation mechanisms of the Himalayan metamorphic core.

Deep coal mining activities close to a fault generally cause shear stress concentration and slipping of the fault. This increases the risk of coal bumps and severely endangers miners’ lives as well as the effectiveness and productivity of mines. In this study, seismicity distribution resulting from fault slipping induced by mining in the graben structural area and the coal bump seismic precursors are investigated using high-precision seismic monitoring technology. Subsequently, the evolution of stresses in rock masses and fault reactivation characteristics during the mining process is analysed via numerical simulation. With the advancement of the working face, the maximum principal stress difference between the two sides of the fault gradually increases, resulting in shear slipping of the fault (i.e., fault reactivation). Seismicities occur frequently because of the repeated release of accumulated elastic energy. The number and total energy of mining-induced seismicities in the hanging wall of the fault are higher than those in the footwall. The frequency and number of mining-induced seismicities decrease before the occurrence of the coal bump. Additionally, the mechanism of the coal bump induced by fault slipping, caused by the superposition of static and dynamic stresses during coal mining, is investigated.

We investigated rare earth element (REE) minerals in low- to medium-grade metapelites sampled in two nappes of the Austroalpine Unit (Eastern Alps, Austria). Combining microstructural and chemical characterization of the main and REE minerals with thermodynamic forward modeling, Raman spectroscopy on carbonaceous material (RSCM) thermometry and in situ U–Th–Pb dating reveal a polymetamorphic evolution of all samples. In the hanging wall nappe, allanite and REE epidote formed during Permian metamorphism (275–261 Ma, 475–520 °C, 0.3–0.4 GPa). In one sample, Cretaceous (ca. 109 Ma) REE epidote formed at ∼440 °C and 0.4–0.8 GPa at the expense of Permian monazite clusters. In the footwall nappe, large, chemically zoned monazite porphyroblasts record both Permian (283–256 Ma, 560 °C, 0.4 GPa) and Cretaceous (ca. 87 Ma, 550 °C, 1.0–1.1 GPa) metamorphism. Polymetamorphism produced a wide range of complex REE-mineral-phase relationships and microstructures. Despite the complexity, we found that bulk rock Ca, Al and Na contents are the main factor controlling REE mineral stability; variations thereof explain differences in the REE mineral assemblages of samples with identical pressure and temperature (P–T) paths. Therefore, REE minerals are also excellent geochronometers to resolve the metamorphic evolution of low- to medium-grade rocks in complex tectonic settings. The recognition that the main metamorphic signature in the hanging wall is Permian implies a marked P–T difference of ∼250 °C and at least 0.5 GPa, requiring a major normal fault between the two nappes which accommodated the exhumation of the footwall in the Cretaceous. Due to striking similarities in setting and timing, we put this low-angle detachment in context with other Late Cretaceous low-angle detachments from the Austroalpine domain. Together, they form an extensive crustal structure that we tentatively term the “Austroalpine Detachment System”.

The Fenwei Basin, which has 612 developed ground fissures, is the most concentrated and severe area in China and even the world for ground fissure hazards. The Jiaocheng ground fissure in the Taiyuan Basin is known for being the longest length and causing the most damage and impact in China. To discover the origin of the Jiaocheng ground fissure, surveying, trenching, and geophysical exploration were used to study its geological basis, developmental characteristics, and genetic processes. With a total length of 46 km and an impact bandwidth of 80–120 m, it is one of the longest ground fissures found in the world. The fissure is located on the hanging wall of the Jiaocheng fault, and the NE strike is quite consistent with this fault. Houses, roads, fields, and other structures have all been damaged to varying degrees by the fissure. The most common movements are vertical slip, horizontal tension, and right-lateral slide. According to trenching and shallow seismic profiling, this fissure has synsedimentary features. The Jiaocheng ground fissure was formed due to the interaction of several forces. First, the Jiaocheng fault shifted because of regional extension, creating a rupture system in the surface strata. Pumping activity contributed to the formation of the current ground fissure. This research has significant implications for understanding fissure mechanics and preventing and mitigating ground fissures.

To study the hydrochemical characteristics of main aquifers in Jiaojia gold mine area and their changing regularities, exploring the main sources of mine water, 244 water samples from the main aquifers and mine water were collected. The principal components were extracted by factor analysis and shows that with the increase of depth, the concentration of Na+ and Cl− increased significantly, the water–rock interaction becomes stronger, the water quality develops towards salinization, the total water quality, hydrodynamic conditions, and the connection between groundwater and surface water becomes worse. We extracted the main influential discriminant indexes using principal component analysis (PCA), that is, pH, MH4+, NO3−, NO2−, total hardness, TDS, Fe3+, SO42−, Cl− and F−. We weighted the extracted discriminant indexes using entropy weight method (EWM), that is in turn, 0.0002, 0.1883, 0.1272, 0.2061, 0.0680, 0.0613, 0.1461, 0.0573, 0.0844, and 0.0613. 55 water samples from each aquifer in the last 5 years were analyzed by hierarchical cluster analysis (HCA), and the relational degree between the main aquifers and mine water was judged by the distance between them; result shows that the main source of mine water is from the hanging wall of fault aquifer, followed by the footwall of fault aquifer. The mine water has little connection with bedrock weathered fractured aquifer, and almost no connection with Quaternary porous aquifer. The PCA–EWM–HCA model established in this paper provides a theoretical basis for identification of mine water inrush source and protection of underground water resources.

A 2D discrete element model is adopted to study the impact of a Strong Inclined Wall (SIW) on reverse fault rupture-soil-foundation interaction in cohesionless soils with different densities. DEM simulation is validated with centrifuge results. Significant improvement in performance is observed when the in-plane orientation of the SIW is aligned with the fault plane and the fault plane intersects the bottom of the SIW. If the SIW inclination is higher than 30°, the SIW breaks the continuity of the fault rupture and results in soil heave at the footwall corner of the foundation. This causes the foundation to rotate towards the hanging wall. In some models with a low SIW inclination, SIW leads to an increase in foundation rotation. The SIW better minimizes foundation rotation in dense soil and increases the amount of fault dislocation required to rupture the ground surface. In models with a fault dip angle equal to 75° and a SIW inclination greater than 30°, multiple ruptures develop and create a failure wedge beneath the foundation. Using an SIW changes the micro-mechanism of failure. The dual pressure generated from faulting and SIW causes the soil particle contacts under the SIW to break which results in rupture deviation.

The object of the study is a rock massif represented by complex-structured ore bodies mined by underground systems with open stoping or systems with bulk caving. Deposits of Kryvyi Rih iron ore basin are represented by different types of ferruginous quartzite, which enables application of a great number of mining systems to mining blocks. There are also barren rock inclusions within the block which are extracted from the block along with ore, and this reduces the iron content of the mined ore mass. Findings of the comprehensive study enable concluding that application of the selective method when mining a deposit can enhance recovery rates. Analysis of methods for determining rock stability results in ascertaining that in case of a 4–7 m thick inclusion of barren rocks it is advisable to use a system with bulk caving at a single stage, and in case of a 7–12 m thick inclusion – in two stages. The first stage involves mining the hanging wall reserves, the footwall reserves are mined at the second stage. This method is distinguished by leaving a barren rock inclusion in the block. The developed options of the mining system allow increasing the iron content in the mined ore mass by 2–4% and obtaining the expected economic effect from 3.0 M to 30.2 M USD depending on mining and geological conditions.