Overburden Strata Research Articles

Characterization of radon gas transmission rate in pore structures of different rock layers by radon daughters inversion calculation

Determining the transmission rate of radon gas in overburden strata is crucial for conducting a comprehensive study of radon gas's longitudinal and long-distance migration mechanisms. This study investigates the mineral components of rocks in the underground strata of the mining area using the X-ray diffraction method. Additionally, it examines the pore structure parameters of the rocks at different depths using the low-temperature nitrogen adsorption method. This research introduces an approach to inversion calculate the radon gas transmission rate through the activity ratio of radon's characteristic daughters based on the decay law and activity balance of 210Po and 210Pb daughters. In addition, it determines the transmission rates of radon gas in overlying strata at various depths through this method. The relationship between the rock's mineral composition and pore structure is investigated, and the effects of pore structure and mineral composition on the radon gas transmission rate are analyzed. The findings indicated that the pore structure exerts a dual impact on radon gas transport: macropores serve as channels for upward radon gas transport, while micropores offer most of the adsorption area. In contrast, the radon gas transmission rate is indirectly influenced by the mineral composition content associated with the medium's adsorption capacity and pore structure. In the studied lithologies, an increase in quartz content promotes radon gas transmission, while an increase in clay mineral content impedes it. Finally, the mechanisms of radon gas transport, daughter adsorption, and the impacts of rock pore structure and mineral composition on the radon transmission rate are discussed.

Grout Ground Leakage Caused by the Development of Separation Layer in a Case Study of Muduchaideng Coal Mine

A lot of grout ground leakage occurred during Muduchaideng coal mine separation layer grout work, resulting in serious pollution. To find the mechanism of grout leakage, this paper carried out indoor experiments and on-site measurements. Through the indoor scale model test, the deformation of overburden stratum was captured, which reflected that the horizontal shear band developed at the depths of 289.67–322.48 m, 386.42–431.18 m, and 474.95–524.07 m. Then, these positions were verified through on-site drilling. It was found that the mud slurry consumption increased, the water level dropped, and the borehole wall was seriously deformed in these disturbed positions. Therefore, the reason for this grout leakage was that the overlying separation layer continued to develop upwards, and the borehole was destroyed in the location where the separation layer developed. Then, the grout pipeline was destroyed, and some grout flew towards the ground surface along the pipeline and the borehole wall. This article reveals a kind of grout ground leakage phenomenon in a case study of Muduchaideng coal mine, which can provide a warning for engineering projects.

Improvement of the separation evolution law and separation position determination method of mining overburden strata

In view of the shortcomings of the traditional method of determining the position of the separation layer, according to the actual movement of the pressure balance arch and the rock layer in the overburden, the concept of the triangular separation domain is proposed, and the relationship between the range of the triangular separation domain and the mining distance and the mining fracture angle is established. The calculation method of rock load is modified. By analyzing the stress mode in the pressure arch of the separation zone, the mechanical model of the deflection calculation of each rock stratum is established. Combining the triangular separation zone with the new mechanical model, the calculation model of the dynamic evolution analysis of the separation zone and the calculation model of the composite beam in the separation zone are established. The traditional method and the improved method are used to determine the separation position in an actual mining example. The field exploration proves that the results of the improved method described in this paper are more accurate. The model predicts the position of overburden separation by comparing the deflection between adjacent strata on the same horizontal contact surface, and can accurately predict the position of separation above the working face.

Experimental investigation on stress distribution and migration of the overburden during the mining process in deep coal seam mining

Coal mining has a significant impact on the movement of the overburden, leading to potential safety hazards in the working face. In this paper, a similarity simulation experiment was conducted to investigate the migration of overburden during the mining process of a specific working face in the Liuzhuang Coal Mine located in southern China. Sand and gravel were used to simulate the geological environment of each rock stratum. The deformation of the stratum was monitored using strain gauges, the fracture and displacement changes of the overburden stratum were recorded using cameras, and the characteristics of roof collapse was monitored using infrared thermal imager. The experimental model fully simulated the situation of the working face, and the actual working face size was obtained by enlarging the model by 100 times. The experiment found that during the initial stage of mining, there was no significant subsidence of the roof. In the course of the advancement of the working face, the primary roof intermittently fractured behind the working face, with subsequent propagation of upper cracks in an upward direction. The overburden rock layer above the goaf experienced continuous compaction, leading to the gradual closure of the separation layer. Simultaneously, new cracks constantly emerged in front of the working face, resulting in the progressive stabilization of the height of the crack zone. The stress measurements at each point exhibit a pattern of initial increased, followed by decrease, and ultimately stabilization. By considering the stress variation law of the overburden rock, the stress changes in key layers of the bedrock during mining could be categorized into four zones: the stress stable zone, stress increasing zone, stress reducing zone, and compaction stable zone. During the initial phase of coal seam mining, the presence of rock layers provided support, resulting in minimal subsidence of the overburden rock. However, as the mining operation progressed, the disturbance force and collapse of the overburden rock leaded to further downward subsidence. When the working face reached the stop line, the collapsed overburden rock gradually consolidates, resulting in a deceleration of energy release and the formation of a pressure relief zone. Consequently, the overburden rock above the working face underwent a slight additional subsidence, reaching its maximum level. A short cantilever rock beam structure was formed in the experiment. This study will provide valuable reference for future coal mining and serve as a vital theoretical basis for roof control in deep coal seam mining.

FEATURES OF GEOMORPHOLOGY STRUCTURE OF THE GNIVAN GRANITE QUARRY (VINNYTSIA REGION)

The Hnivan granite quarry is located in Vinnytsia district of Vinnytsia region. Geomorphologically, territory belongs to the western edge of the Dnieper Upland. Geostructurally, the quarry is located on the western edge of the Ukrainian shield, within the Podilsky megablock. Since the beginning of development, 7 rock horizons have been fully opened. As of today, the 8th horizon is being developed, and the development of the 9th horizon is planned in the future. The Hnivan quarry is a deep polygonal trapezoidal quarry in plan with many steps in profile. Morphometric characteristics of the Hnivan quarry and dump complex: the maximum length from north to south (including dumps of overburden strata) is 1 800 m; the maximum length of the quarry pit from north to south is 1 400 m, the maximum width from west to east is 900 m. The absolute heights within the mining are 230–255 m, the absolute height of the mine floor is 130 m. The depth of the quarry pit is currently about 105 m. The bottom is 97 meters below the level of the Southern Buh river. Quarry landforms are divided into produced relief forms, caused by anthropogenic denudation and bulked relief forms, created as a result of anthropogenic accumulation. The produced relief of the Hnivan quarry is represented by the bottom and walls. The bottom has a complex geometric shape of an elongated polygon from north to south. It consists of the bottom of the seventh developed horizon and the eighth horizon, where mining operations are carried out. Between these horizons, there is a step 15 m high. The surface of the bottom is flat, there are no internal dumps. The walls of the quarry are characterized by a multi-step shape in profile. They are approximately the same in height, steepness and nature of the processes. The structure of the walls in the upper parts, which are represented by ledges of overburden horizons, is different. The ancient steps of the mine walls are significantly disturbed by weathering, water erosion and gravitational processes. The produced relief forms of the quarry are represented by overburden dumps and processing plant dumps. All of them are located outside the quarry and are external dumps. Dumps of overburden strata are recultivated - stable and artificially forested. This example of carrying out reclamation works of a part of the quarry and dump complex can be a model for the improvement of anthropogenically disturbed territories. Key words: granite quarries; geomorphological structure; excavated relief; heaped relief; Hnivan.

Greenhouse gas protection and control based upon the evolution of overburden fractures under coal mining: A review of methods, influencing factors, and techniques

In accordance with the Paris Agreement, many nations have set out a global framework to stabilise and prevent greenhouse gas (GHG) emissions to mitigate climate change. This study reviewed the literature on the GHG protection and control (GHGPC) impacts of overburden fractures in relation to coal mining. Different factors, such as geological conditions, mining conditions, and gas extraction methods, were compared because they influence GHGPC. Carbon emissions, coal mining safety, and environmental protection are crucial parameters. GHGPC can (1) improve the safety and efficiency of mining, (2) reduce GHG emissions, and (3) generate clean gas resources. During mining, cracks appear in overburden strata, causing GHG emissions. Various techniques, including scanning electron microscopy, nuclear magnetic resonance, two-dimensional and three-dimensional physical similarity simulations, permeability testing, and numerical simulations, have been adopted to determine the macroscopic and microscopic features of overburden fractures. Finally, the extraction method of GHG was optimised through field practice, namely, roadway, borehole, and pipe extraction, were analysed, and the comprehensive GHG extraction method was preferred to achieve superior management results. This paper reviewed studies that examine the development of fractures to elucidate the significance of GHGPC. Moreover, this article provides new insights into the achievement of the “dual carbon strategy” with particular reference to coal mining; it also summarises the holistic life cycle of gas management in terms of overburden activity, gas transport patterns, reservoir characteristics and typical technologies. It also summarises the holistic life span of GHGPC management in terms of overburden activity, GHG transport patterns, reservoir characteristics, and typical technologies. Finally, the authors discuss and conclude the article with proposed methods for future research directions.

Numerical simulation study on the evolution characteristics of the stress induced by mining in deep adjacent working faces

BackgroundThe mining-induced stress in the surrounding rock after coal seam mining is the primary cause of damage and failure of the surrounding rock in the mining area. However, the magnitude and direction of the stress field induced by mining in the overburden strata during the excavation process of deep and adjacent coal seams are not yet clear, and it is difficult to determine how adjacent working faces interact with each other.ResultsIn this study, a large-scale numerical model was built using FLAC3D (Fast Lagrange Analysis Continua) to simulate the sequential mining process of three adjacent working faces (No.1, No.2, and No.3) in Liuzhuang Coal Mine located in southern China. The results showed that the maximum height of plastic zone development after mining in the No.1 working face was 41 m, and the maximum height of plastic zone development was 33.8 m away from the 13 coal seam. It did not affect the top and bottom of the No.3 working face. The development height of the plastic zone on the roof of the No.2 working face after mining was 52m, and the top and bottom plates of the No.3 working face remained intact. The plastic zone of the floor of the No.3 working face after mining was not communicated with the plastic zone of the roof of the No.1 and No.2 working faces. There was a complete rock layer between the two coal seams, and there was not the mutual influence of the mining activities. During the mining process of working faces No.1 and No.2, the range of dynamic pressure influence was extended up to 100m ahead of the working face. During the mining process of the No.3 working face, the range of dynamic pressure influence was 120 m ahead of the working face. The No.1 working face goaf and the mining of No.2 working face had not disturbance to the No.3 working face.ConclusionsAfter the mining of No.1 and No.2 working faces, the stress in the goaf significantly decreased, and the lateral support stress concentration area of No.1 and No.2 working faces had a relatively small impact on the 13 coal seam. Therefore, the No.1 goaf and mining of No.2 working faces had not disturbance to No.3 working face.

Deep-learning-based 3D fault detection for carbon capture and storage

Fault analysis plays an important role in determining the location of potential CO2 storage sites in which long-term storage feasibility is critical. The presence of faults and fracture zones can potentially lead to the gradual migration of CO2 from the storage reservoir to the atmosphere through the overburden strata. Traditional methods such as manual picking of faults are time-consuming and labor-intensive tasks, which can be costly for the CO2 storage site assessment process. To help address this concern, we develop a process for automating fault picking using deep neural networks. We implement two different deep neural networks based on the architectures of UNet and Deeplab v3+. We train the networks using synthetic data and labels and augment them using linear transformations and elastic deformations. We implement an ensemble-based approach to improve the generalization ability of our method. We also incorporate uncertainty estimation into the framework to aid in the risk management aspect of the decision-making process. We use data sets from different regions across the globe which help us to improve the methodology, with the ultimate aim to help 3D fault detection in the Smeaheia Field, a potential site for CO2 storage scale-up on the Horda Platform, offshore Norway.

Evolution law of mining-induced overburden stratum stress and fracture fields in inclined coal seam

Purpose This study aims to clarify the evolution law of stress field and fracture field during the mining process of inclined coal seam, to prevent the occurrence of roof burst water and impact ground pressure accident during the advancing process of working face. Design/methodology/approach The evolution law of stress-fracture field under different mining conditions of inclined coal seam was studied by using discrete element method and similar material simulation method. Findings The overburden stress at the lower end of the coal seam was mainly transmitted to the deep rock mass on the left side, and the overburden stress at the upper end was mainly transmitted to the floor direction. With the increase of the inclined length of the mining coal seam, the development of the fracture zone gradually evolves from the “irregular arch” form to the “transversely developed trapezoid” form. The development range of the fracture zone was always in the internal area of the stress concentration shell. Originality/value An original element of this paper is based on the condition that the dip angle of coal seam is 35°, and the evolution law of overburden stress-fracture field during the excavation of coal seam with different lengths was analyzed by UDEC numerical simulation software. The coupling relationship between stress shell and fracture field was proposed, and the development range of fracture zone was determined by stress. The value of this paper is to provide technical support and practical basis for the safety production of a mine working face.

Fracture Evolution of Overburden Strata and Determination of Gas Drainage Area Induced by Mining Disturbance

Overburden strata fracture evolution is critical to dynamic disaster prevention and gas-relief drainage, so it is important to accurately determine the evolution relationships with mining disturbance. In this paper, experiments and numerical simulation were adopted jointly to characterize the time-varying fracture area of overlying strata. The experimental results showed that the roof strata gradually broke and collapsed with coal mining, which indicated the fractures of overburden strata developed in an upward direction. The fracture development causes were explained by numerical simulation, which showed that stress increase exceeded the strength of coal and rock strata, and fractures were formed and expanded. Both experiments and numerical simulation results showed the two sides and the top of fracture areas provided channels and spaces for gas migration and reservoir, respectively. In addition, the breaking angle of overburden strata and the height of fracture areas were analyzed quantitatively. Through microseismic monitoring at the mining site, the fracture scales and ranges of overburden strata were verified by the energy and frequency of microseismic events, which were consistent with the support of maximum resistance. The position of drainage boreholes was considered based on the results of overburden strata fracture evolution. Our study is aimed at promoting coal mining in safety and improving gas drainage with a sustainable approach.

Diversity and Heavy Metal Tolerance of Fungi Associated with Different Coal Overburden Strata of Tikak Colliery, Assam.

Coal mine overburdens are generally highly acidic and contaminated with toxic heavy metals. Here, we studied the culturable fungal diversity associated with different coal overburden strata (OBS) of Assam, India, and assessed their heavy metal tolerance ability against five different heavy metals viz., As3+, Cd2+, Cr6+, Cu2+, and Ni2+. Among 15 distinct coal OBS considered in this study which spans a depth of ~ 35m from the ground surface, the isolation of fungi was successful only from 11 OBS samples and the colony-forming unit (CFU) counts were highly variable among the samples. A total of 66 fungal pure cultures were isolated which belong to 18 genera (17 known and 1 unknown) under 15 families and two divisions i.e., Ascomycota (89.4%) and Basidiomycota (10.6%). Acidiella bohemica was found relatively the most abundant species followed by Rhodotorula toruloides. A good number of fungal isolates was found tolerant to the test heavy metals at concentrations ≥ 1mM. Findings of some multi-metallotolerant fungal isolates along with a tolerance up to 5mM concentration of As3+, and up to 10mM each of Cu2+, Cr6+, Ni2+ and Cd2+ were noteworthy in the present study that could be useful in the management of heavy metal pollution or stress. Cultivable fungal diversity of coal mine overburden strata of Tikak colliery, Margherita, Assam, India. It shows a photograph of the coal mining site as the background, front view of the fungal colonies in the upper section, and a graphical representation of heavy metal tolerance of the isolates at different concentrations of As, Cd, Cr, Cu, and Ni in the lower section.

Overburden Failure Associated with Slicing Mining in a Super Thick Coal Seam under Special Weak Aquifers

With the increasing improvement of national ecological standards, the eco-environmental problems caused by super thick coal seam mining in western China are becoming more and more serious. The failure law of weak overburden stratum is an important factor affecting the safe mining of coal. The failure characteristics of weakly cemented overburden under high-intensity mining in the mining area of western China were studied. For this purpose, a case study was conducted in the 1101 working face of the Baituyao Coal Mine in Ürümqi County. Based on the analysis of geological conditions in the study area, we combined empirical calculations with engineering analogy, physical simulation, and numerical simulation to comprehensively analyze the characteristics of mining-induced overburden failure. The study showed that the overburden in the study area had several unfavorable engineering geological characteristics, including ease of softening in the presence of water. The Middle Jurassic Xishanyao Formation is a directly recharged aquifer with a weak water-retaining property. Overburden failure mainly occurred at the two ends of the open-off cut. During the mining process, vertical fissures and bed-separated fissures were periodically developed and closed, and the fissures were interconnected. The overburden was fractured, and the fractured zone showed a trapezoidal shape, tapering off from bottom to top. The heights of the caving zone and the water-conducting fracture zone were 25 and 280 m, respectively, in the 1101 working face of the Baituyao Coal Mine, and the ratio of fracturing to mining height was 14.0. Due to the weakly cemented overburden and the presence of the Neogene weak aquifer, the risk of water and sand bursts still exists in this working face under high-intensity mining. Our findings shed light on the safe mining and environmental protection of the ground surface in coal mine shafts in western China.

Theoretical analysis of the overburden stratum load on metro tunnel induced by active ground fissure

Ground fissures are the most common urban geohazard in Xi’an, China. The activities of ground fissures often trigger stratum dislocation, which do harm to the built metro tunnels. Thus, tunnel structures must be designed to reasonably withstand the stratum load during ground fissure activity. In this study, a simplified solution was proposed to calculate the stratum load and the vertical stress of metro tunnel under the action of active ground fissure. The stress characteristics of metro tunnel subject to ground fissure dislocation were analyzed and its progression was divided into three stages, the initial elastic stage, the local void area stage, and the maximum void area stage. The vertical stress of the tunnel at each stage was calculated according to the corresponding mechanical characteristics. Compared with results from numerical simulations, the calculation method developed in this study, which accounts for the stratum holding effect and slip plane, is reliable and reasonable. Additionally, according to the variability of stress magnitude and the impacted range, the tunnel is roughly divided into four stress zones, namely, stability and influence zones in the footwall, and deformation and micro deformation zones in the hanging wall of the ground fissure. This theoretical analysis provides a reference for stratum load calculations and engineering design of metro tunnels crossing active ground fissures.

Fracture distribution in overburden strata induced by underground mining

AbstractCoal‐mining activities give rise to a series of ecological environmental problems, such as ground settlement and groundwater pollution. In fact, they are mainly caused by mining‐induced fractures. Hence, it is necessary to study the mining‐induced fracture distribution to identify the behavior of rock mass movement. However, the fractures in overburden strata cannot be directly measured owing to the special condition. Therefore, the majority of previous studies are based on experiments or experience. For this reason, this study first used a discrete element method to simulate the shape of mining‐induced fractures in overburden strata. Then, a geophysical tool of transient electromagnetic method (TEM) was used to investigate the mining‐induced fracture distribution. Based on the low‐resistivity anomaly area, the water‐rich area in overburden strata was analyzed to be mainly caused by fracture seepage. Through the mutual authentication between numerical simulation and TEM results, the mining‐induced fractures in overburden strata were explored. This study can enhance the understanding of mining‐induced fracture distribution on the one hand and guarantee the coal mining safety on the other, thus guiding the coordinated development between coal mining and environmental protection.

Overlying Rock Activity Laws and Influential Ranges of Coal Seam Mining in Stubble Areas

This report applies theoretical analysis, similar material simulations, and numerical simulation methods to study the overburden strata movements and influential range of coal mining under pressure stubble conditions and to elucidate the relationship between adjacent coal seams. The pressure, failure, caving, stress, and displacement of crop conditions during coal seam mining were evaluated. The results show that the overlying W9-10 coal face and underlying J16-17 roof experience a long first pressure step, i.e., close to the periodic weighting distance. The working face of the W9-10 coal seam is located in the bending subsidence zone of the working face of the J16-17 coal seam. With the advance of the working face of the J16-17 coal seam, the development and range of overburden fracture of the W9-10 coal seam gradually increase. The supporting pressure and displacement caused by the mining process at the W coal seam have no impact on the coal seam of the stubble area, whereas the mining of the J coal seam leads to a continuous increase in the overburden displacement of the W coal seam; the latter also induces a shift in the maximum displacement to the rear, which is more significant for the stress concentration at the middle and front regions of the stubble area, thus presenting a superposition effect. The stress caused by mining at the coal seam decreases with increasing vertical distance from the roof or floor. For distant coal seams, the main contributing factor is the effect of vertical stress. The influential range of the vertical stress caused by mining in the overlying working face remains within 90 m, whereas the influential range of the stress caused by mining in the underlying working face is relatively large, i.e., it still affects the roadway at distances up to 160 m. The results and discussion presented herein provide significant practical value in terms of understanding the overburden strata activity and its influential range in adjacent mines’ stubble areas, which can be used to guide group mining efforts.

Similarity Simulation on the Movement Characteristics of Surrounding Rock and Floor Stress Distribution for Large-Dip Coal Seam.

The question of how to mine safely in close multi coal seams is the main concern for coal operators, in particular for large-dip coal seams with complex geological and mechanical conditions. This paper presents a detailed similarity simulation on the movement characteristics of the overburden and the stress distribution of underlying strata in terms of a specific coal mine in the Tielieke mining area of the Kubai coalfield via a three-dimensional photogrammetry system and a high-speed static resistance analyzer. The results show that the overburden strata are asymmetrically deformed around the coal pillar and the fracture area is perpendicular to the longwall with an “M” shape when deeper coal is mined. Moreover, the asymmetric movement of overburden results in the non-uniform distribution of stress on the floor of the coal pillar and ribs. In particular, stress is closely related to the location of the longwall, and stress of the coal pillar is much larger when it is closer to the deep side. The floor stress relief degree of the longwall in the deep zone is higher than that of its counterparts, providing a theoretical foundation for a reasonable layout and a support technique for roadways. The main contribution of this research that it can be used as a reference in maintaining the integrity of surrounding rock for large-dip coal seams with close distances.

Investigation on the Responses of Overburden Stress and Water Pressure to Mining under the Reverse Fault

This paper focuses on the responses of overburden stress and pore water pressure in confined aquifer to mining under the Ordovician limestone aquifer and the reverse fault. Taking 32 coal seam mining in the first eastern mining area of Qianyingzi coalmine in China as engineering background, on the basis of the mining hydrogeological and engineering geological model of the study area, a numerical calculation model considering the fluid-solid interaction is established. Simulation results indicate that the variation characteristics of pore water pressure in confined aquifer and overburden stress are affected by both mining effect and geological tectonics and are closely related to the shear failure of the reverse fault plane caused by mining effect and the failure characteristics of the overburden strata in the stope. According to the variation of pore water pressure before and after the roof water inrush, the reduction range of pore water pressure can be used as one of the early warning indicators for water inrush accidents. These new understandings are of reference value to the mining water inrush under the combined action of reverse faults and confined aquifers and to the establishment of corresponding forecasting and early warning systems.

Subsidence prediction of overburden strata and ground surface in shallow coal seam mining

Shallow coal seam with thick soil layer is widely reserved in the Jurassic Coalfield, Western China, mining-induced subsidence represents complex characteristics. Combining with physical simulation, theoretical analysis and in-situ observation, the overburden strata structure in dip direction were revealed, and the subsidence prediction models were established, based on this, the subsidence equations of overburden strata and ground surface were proposed. The results show that after shallow coal seam mining, based on the subsidence and movement characteristics, the overburden strata structure can be divided into three zones, which are "boundary pillar F-shape zone" (BPZ), "trapezoid goaf zone" (TGZ) and "coal pillar inverted trapezoidal zone" (CPZ). The subsidence of overburden strata depends on the key stratum, while the subsidence of soil layer depends on the bedrock subsidence basin, which is between the bedrock and thick soil layer. The bedrock subsidence is mainly related to mining height and bulking coefficient in TGZ, while it is mainly affected by mining height and distribution load on the key stratum in BPZ and CPZ. According to physical simulation and theoretical model, the maximum surface subsidence of No.1-2 seam mining in Ningtiaota coal mine are 1.1 m and 1.07 m respectively, which is basically consistence with the result of in-situ observation (1.2 m).

Study on the Mine Pressure Law and the Pressure Frame Mechanism of an Overlying Goaf in a Shallow Coal Seam

To study the problems of dynamic load pressure and frame pressure caused by the concentration of stress by coal extraction pillars during the mechanized short-distance mining of goaves in shallow coal seams, a frame pressure accident, in the Shendong Shigetai Coal Mine, during the overlying of a fully mechanized mining goaf is taken as a research example. By applying the field measurement, theoretical analysis, and numerical simulation methods, we throughly analysed the working face coal pillar, got the regular pattern of fully mechanized overburden pressure, summarized a pillar of fully mechanized working face in the overburden strata movement regularity and development characteristics, analyzed the reason and mechanism of broken coal pillar, and put forward the corresponding prevention measures and management method. The results show that when the fully mechanized mining face enters the goaf by about 3 m, the pressure arches of the lower coal face and the upper goaf arising from the extracted coal overlap. When the vertical stress is greater than the supporting force of the hydraulic support and the coal wall, a roof ejection accident may occur.

Evolvement of interpretation capacities of seismic measurements in mining of water-soluble minerals

The current development level of geophysical methods for mining monitoring of water-soluble mineral deposits provides opportunities to control the growing variety of potentially hazardous geological and mining conditions, to identify the critical states of rock mass and to monitor the emergency facilities. Seismic surveys for solving the specified problems have proven to be a highly informative method for studying the structural features and properties of productive and waterprotective overburden strata, which has a high information richness of the recorded data. The main set of parameters for the interpretation stage of seismic exploration has been formed based on the experience in shallow seismic surveys within a potash deposit; it incl udes the target reflection times, effective and interval velocities, amplitudes, frequencies and a number of derivatives from these parameters. Improvement and adaptation of world interpretation practices in relation to the indicated seismic studies conditions provides means for increasing reliability of anomalies identification and expanding the set of typical wave ‘images’ for various kinds of inhomogeneities in a wide range of wave field realizations and its attributes. The analysis of irregular wave field component in the results of scattered waves processing, spectral decomposition and RGB-mixing is considered as an additional techniques of qualitative interpretation. An approach is proposed to determining possible fracturing in rock mass based on the variability of interval velocities. In combination with the AVO-analysis, this approach makes it possible to assess the trend of rock disintegration within the emergency facilities. The interpretation results of the areal (quasi-3D) and spatial (3D) detailed surveys of a shallow potash deposit are presented.