Rock Burst Accidents Research Articles

Research on risk management and prevention and control system of major disasters in coal mine based on fish-bone diagram and STAMP/STPA model

Fishbone diagram and STAMP/STPA model is a problem of control safety from the perspective of system theory, caused by the lack of sufficient control and safety-related constraints. There is a certain relationship between the model and coal mine construction projects. Based on the introduction of the basic concepts of the fishbone diagram and the STAMP /STPA model, this paper combines the construction of coal mine projects in China with frequent accidents, and based on the fishbone diagram model, establishes a coal mine stamping accident cause model. At the same time, the empirical analysis of typical rock burst accidents is carried out, and the starting point of the analysis is the theoretical point of view caused by system accidents. According to the fishbone diagram and STAMP /STPA model, the accident process is analyzed, the cause of the accident is analyzed, the accident disaster is described, and the safety constraints and fault behaviors are identified. Finally, the basic causes of the accident are analyzed and compared. The results show that the fishbone diagram and the STAMP /STPA model can be well used in the risk management of major disasters in coal mines. Through the safety control structure of the risk control model, the constraints and failure behaviors of each control level can be effectively identified. According to the interaction and feedback at all levels, the cause of the accident can be analyzed and obtained, which is of great significance for preventing and controlling major disasters in coal mines. <br/>

Crack Propagation Mechanism of Hydraulic Fracturing in Thick-Bedded Sandstone Coal Mine Roof

The thick-bedded sandstone roof of the Bayangaole coal mine is at risk of rock burst accidents. Hydraulic fracturing technology has been used to prevent these accidents by controlling coal seam roof collapse. To research the crack propagation mechanism of hydraulic fracturing in thick-bedded sandstone roof, hydraulic fracturing experiments are conducted on thick roof sandstone with a hole drilled in the center, and RFPA2D-Flow software is adopted to conduct numerical simulations of the formation mechanism and spatial distribution of hydraulic fracture cracks in bedded sandstone. The physical experiments reveal that cracks are generated from the weak parts and stress-concentration area of the hole wall due to hydraulic pressure; main cracks either form along the bedding or spread toward the bedding. Numerical simulations show that the crack propagation mechanism for specimens without preset slotting is consistent with the experimental results. For the preset-slot specimens, micro-cracks generate in the region where tensile stress is applied, which gradually increase and penetrate the preset slotting tip; the specimen continues to crack until failure occurs. When the main crack encounters the bedding, it turns and propagates along the bedding when the bedding angle is small, which results in tensile failure. However, when the angle is large, the crack passes directly through the bedding, forms a new hydraulic crack, and continues to propagate forward, which results in the tensile failure of the cutting bedding.

Energy Variation Law and Rockburst Characteristics of Coal under Cyclic Loading

Coal mining involves numerous challenges and safety risks owing to the complex engineering properties of coal bodies, which include discontinuities, heterogeneity, and anisotropy. In this paper, the strain energy during the coal deformation process is redivided in combination with cyclic loading and unloading tests to determine the energy evolution law and discuss the rockburst tendency characteristics. The results show that the elastic strain energy, and particularly the base-material strain energy, consistently dominates during the energy adjustment process, which is an important indicator of rockburst tendency. The elastic energy index and rebound deformation index also show that moderate plastic deformation (e.g., crack expansion and local penetration) can reduce the rockburst tendency level and prevent rockburst accidents. On the basis of the obtained results, precracking and pressure relief measures of blasting are adopted on site in advance of the working face, and good safety and economic benefits are achieved. These findings, thus, provide an important engineering reference for mines under similar conditions.

Prediction of rockbursts in a typical island working face of a coal mine through microseismic monitoring technology

Coal has dominated the energy structure in China for a long time. In recent years, dynamic disasters such as rockbursts have affected the safety of coal mine in production with the increase of coal mining depth. Microseismic monitoring is a non-intrusive monitoring technique that can be used to collect much key information: it has been widely applied in coal mine safety monitoring. In this paper, the failure mechanism and energy conversion in a coal-rock mass during mining were investigated, revealing the controlling effect of the surrounding rock mass on the coal seam. microseismic events during mining were monitored by using a self-built high-precision microseismic monitoring system, a variety of analytical methods have been used to quantify the monitoring results, and two rockburst accidents have been identified. The responses of different parameters before the rockburst were analyzed, and the response characteristics of different parameters to rockburst were summarized. The functional relationship between microseismic energy and rock damage was established by classical Benioff strain theory. Combined with the microseismic energy, strain, the degree of damage and the damage, the model of coal-rock mass was verified and modified through physical experiments. A new parameter for rockburst prediction (the energy rockburst warning (ERW) index) was defined and the numerical relationship between ERW and microseismic energy was deduced. The monitoring data were analyzed using this model and results showed that compared with other analysis, the new model can effectively assess the stability of coal-rock mass to a certain extent.

A New Theoretical Model of Rock Burst-Prone Roadway Support and Its Application

A rock burst usually causes a roadway collapse or even an instant blockage. When the deformation energy accumulated in the surrounding rock exceeds the minimum energy required for the dynamic destruction of the surrounding rock of a roadway, a rock burst accident will occur. According to statistics, 85% of rock burst accidents occur in roadways. This paper establishes a strong-soft-strong structural model for the rock burst stability control of the surrounding rock of a roadway, and the anti-impact and antiseismic mechanisms of the mechanical model are analysed. The strength, stress transfer, deformation, and energy dissipation characteristics of the strong-soft-strong structure are studied. The stress criterion and energy criterion of rock burst failure in small internal structures are derived for roadway support design. The support scheme of “anchor cable active support + hydraulic lifting support + soft structure energy absorption” is proposed. A steel pipe can be inserted into a borehole drilled into the small internal structure to realize the proposed innovative protection technology for small internal structures by creating a soft structure that can release, absorb, and transfer the pressure by repeatedly cracking the coal and rock mass. The innovation of cracking technology for soft roadway structures has been realized. The roadway tested with this strong-soft-strong enhanced surrounding rock control technology met the production requirements during the mining period. The field test was successful, and the expected support effect was achieved. This work provides a reference for roadway support under similar conditions and can be popularized and applied.

Quantitative mechanism of roadway rockbursts in deep extra-thick coal seams: Theory and case histories

Rockbursts are globally recognized as one of most severe dynamic disasters in mines. Generally, rockbursts can be divided into self-initiated bursts type and remotely triggered bursts type in terms of their occurrence mechanism. In recent years, various remotely triggered roadway rockburst accidents (induced by seismic disturbance) in deep extra-thick coal seam have been reported in China. In this study, using stability theory, seismic disturbance factor was involved with in-situ stress, mechanical properties of the coal and rock mass, support strength, and roadway size to establish a mechanical model for rockburst and to obtain critical indexes of the surrounding rock fracture and rockburst occurrence. Accordingly we achieved the quantitative description of a remotely triggered roadway rockburst in extra-thick coal seams. In detail, using a rock fracture criterion, the critical ground stress indexes and corresponding formulas of surrounding rock softening and fracture occurrence were determined. Moreover, using an instability criterion, critical indexes of the roadway rockburst initiation were established, including the critical radius of the fracture zone, the critical radius of the softening zone, critical stress, maximum allowable disturbance stress, magnitude, and energy. The main influencing factors and laws of rockbursts were determined quantitatively. The critical indexes were quantitatively calculated using some typical case histories of roadway rockbursts in coal mines in China, which would lay a foundation for the development of quantitative criterion of rockbursts.

Study on Reasonable Layout of Upper Protective Layer for Prevention Rock Burst under Coal Seam Group with Close Quarters Conditions

To study the reasonable layout of upper protective layer for the prevention rock burst under coal seam group with close quarters conditions, a panel 3203 that belong to Zhongxing Colliery is taken as a typical engineering background. By means of on‐site survey, theoretical analysis, numerical simulation, and on‐site industrial applications, the reasonable layout of upper protective layer for prevention rock burst is studied. The results show that the overall stress environment of the floor under gob of upper protective layer is good, and the overall stress environment of the floor under the upper side of gob is also good, but the overall stress environment of the floor under the lower side of gob is bad. According to numerical simulation results, an L‐shaped stress superposition area is formed in the lower end of panel 3203 under the original layout scheme conditions, and the maximum stress concentration coefficient is about 2.8 in stage I and 4.0 in stage II. A new stress superposition area is formed at the middle to lower end part of advance mining face of panel 3203 for the stage II under the optimal layout scheme conditions, and the maximum stress concentration coefficient is about 2.4; the original L‐shaped stress superposition area is gone due the transfer and release of stress, and the optimal layout scheme has a very significant effect on the prevention and control of the subsequent rock burst accidents; the monitoring results of working resistance of hydraulic supports and surrounding rock deformation indicate that the overall pressure relief of the surrounding rock in advanced segment of 3205 tailgate can be effectively realized. The study conclusions provide theoretical foundation and a new guidance for preventing rock burst with similar engineering geological conditions.

Mechanical Properties and Control Rockburst Mechanism of Coal and Rock Mass with Bursting Liability in Deep Mining

In order to study the mechanism of the dynamic disaster of rockburst in a deep coal mine and the prevention and control measures of weakening shock, the MTS815.03 servocontrolled rock mechanics test system is used to test the coal, rock, and combined specimens with the buried depth of nearly 1200 m in Xinwen Mining Area. And their mechanical properties, energy evolution, and bursting properties are studied and analyzed. The rationality of the test results is also verified by the in-situ engineering practice. The key conclusions are as follows: (1) There is a relation between the ratio of elastic modulus Ee before peak strength to descending modulus Ed after peak strength and the bursting properties. For the fractured coal, the descending modulus Ed is relatively small, and the Ee/Ed is relatively large and presents progressive ductile failure with low probability and risk of rockburst. For the less fractured rock, the descending modulus Ed is relatively large, and the Ee/Ed is relatively small and presents brittle failure, which is very similar to the characteristics of rockburst. (2) For the same type of rock, with the increase of confining pressure, the Ee/Ed gradually increases, indicating the reduction of rockburst strength. Therefore, the greater the support strength provided to the surrounding rock surface of the roadway, the smaller the failure degree of rockburst. (3) With the increase of confining pressure, after peak strength, the elastic energy of coal specimens decreases slowly, and the dissipated energy increases slowly, indicating that the increase of confining pressure can effectively limit the energy dissipation and release after coal specimen failure. So, in the in-situ engineering practice, it is an important measure to improve the surface restraint and support strength of the coal roadway for reducing the occurrence intensity and probability of rockburst. (4) The combined measures of “the mining of double liberating seam + the implementation of large-diameter pressure relief borehole in advance of working face” is the very effective way to eliminate the rockburst accidents of working face in a protected coal seam and has an important guiding significance for the safe mining of rockburst mine.

Research on the Source Mechanism and Source Prevention and Control System of Deep Rock Burst

Deep rock burst accidents occur frequently and become increasingly serious. Further improving the effectiveness and accuracy of the prevention and control of rock burst, ensuring the safe and efficient production of mines, clarifying the basic causes of disasters, and refining the type of deep rock burst are the most important key links. Aiming at the problems such as unclear incentives and types and the lack of effective and targeted prevention measures of deep rock burst, taking Xin’an Mine as the research background, based on the energy theory, the coal and rock mass multisource energy unified equation was established to analyze coal and rock mass instability mechanism. According to the different degrees of participation of various factors, the types of deep rock burst are determined as three categories and four types, and the corresponding judgment criteria are proposed. The precise prevention and control system for the source of rock burst with Xin’an characteristics is proposed, successfully applied to the 8101 working face, which not only guarantees the safe production of the working face, but also achieves good economic benefits. The research results lay the foundation for improving the accuracy and precision of the prevention and control of deep rock burst and provide theoretical guidance for the safe and efficient mining of the mine.

Study on the Evolution Law of Overburden Breaking Angle under Repeated Mining and the Application of Roof Pressure Relief

Aiming at the serious problems caused by coal mine mining activities causing the rock burst accidents, this paper is based on rock mechanics and material mechanics to establish the key layer breaking by the double-key layer beam breaking structural mechanics model of a single working face and double working face under repeated mining. The theoretical calculation formula of the angle was used as the theoretical basis for the elevation angle of the pre-reloading hole of the hard roof. The rationality and reliability of the formula were verified by the physical similarity simulation experiment and the 3 Dimension Distinct Element Code numerical simulation experiment, revealing the rock formation under the influence of repeated mining. The results show that the derived key layer breaking angle formula is suitable for the theoretical calculation of the breaking angle of the key layer of a single coal seam when the repeated disturbance coefficient is λ = 1; when it is λ = 2, it is suitable for the repeated mining of the short-distance double-coal mining. The rationality and reliability of the theoretical formula of the breaking angle of the double key layer of single coal seam and double coal seam were verified by the physical similarity simulation experiment. Through the 3DEC numerical simulation results and theoretical calculation results, the W1123 working face hard top pre-cracking pressure relief drilling elevation angle was 78°. The drilling peeping method was used to verify the results. The results show that the theoretical formula of the critical layer breaking angle is well applied in engineering practice.

Research on monitoring and prevention technology of rock burst in junde coal mine

Rock burst, a dynamic phenomenon in coal mine, is a special manifestation form of the rock pressure. In brief, rock burst is a kind phenomenon of catastrophic failures of the coal and rock mass. Without any obvious macroscopic premonitory symptoms, a large amount of energy is released when the rock burst occurs, thus causing enormous casualties and equipment damages. Since 2004, rock burst accidents have occurred many times in Junde Coal Mine, resulting in damages of mining roadways, suspension of mining activities, or worse still, abandonment of mining roadways and casualties. Over these years, Junde Coal Mine has formed a set of systematic methods and measures which have achieved good result in filed practice.

Numerical Analysis of Roadway Rock-Burst Hazard under Superposed Dynamic and Static Loads

Microseismic events commonly occur during the excavation of long wall panels and often cause rock-burst accidents when the roadway is influenced by dynamic loads. In this paper, the Fast Lagrangian Analysis of Continua in 3-Dimensions (FLAC3D) software is used to study the deformation and rock-burst potential of roadways under different dynamic and static loads. The results show that the larger the dynamic load is, the greater the increase in the deformation of the roadway under the same static loading conditions. A roadway under a high static load is more susceptible to deformation and instability when affected by dynamic loads. Under different static loading conditions, the dynamic responses of the roadway abutment stress distribution are different. When the roadway is shallow buried and the dynamic load is small, the stress and elastic energy density of the coal body in the area of the peak abutment stress after the dynamic load are greater than the static calculations. The dynamic load provides energy storage for the coal body in the area of the peak abutment stress. When the roadway is deep, a small dynamic load can still cause the stress in the coal body and the elastic energy density to decrease in the area of the peak abutment stress, and a rock-burst is more likely to occur in a deep mine roadway with a combination of a high static load and a weak dynamic load. When the dynamic load is large, the peak abutment stress decreases greatly after the dynamic loading, and under the same dynamic loading conditions, the greater the depth the roadway is, the greater the elastic energy released by the dynamic load. Control measures are discussed for different dynamic and static load sources of rock-burst accidents. The results provide a reference for the control of rock-burst disasters under dynamic loads.

Study on Properties of Grouting Materials and Reinforcement Effect in Coal Roadways Influenced by Dynamic Pressure

In order to study the occurrence mechanism of rock burst in coal roadways under the influence of mining activities, the study took five main coal roadways in Yuwu Colliery as an engineering background. The occurrence mechanism of rock burst was analyzed by theory of dynamic and static combined load. Furthermore, based on the prevention mechanism of weak-strong structure, this paper puts forward to use a hierarchical coupled grouting method to reinforce the cataclastic surrounding rock of main coal roadways, and the laboratory test results show that slurry properties of superfine cement is better than that of regular cement. The numerical simulation law of slurry diffusion shows that the water-cement ratio and fracture aperture have obvious influence on the final diffusion distance, but the grouting pressure almost has no effect on it. A bolt-mesh-cable and grouting combined reinforcement method was applied in the five main coal roadways, and the borehole observation and deformation monitoring results show that the control effect of surrounding rock is satisfactory and the rock burst accidents caused by mining disturbance are effectively prevented. The study conclusions provide theoretical foundation and a new guidance for preventing rock burst in coal roadways.

Application of Data Mining in an Intelligent Early Warning System for Rock Bursts

In view of rock burst accidents frequently occurring, a basic framework for an intelligent early warning system for rock bursts (IEWSRB) is constructed based on several big data technologies in the computer industry, including data mining, databases and data warehouses. Then, a data warehouse is modeled with regard to monitoring the data of rock bursts, and the effective application of data mining technology in this system is discussed in detail. Furthermore, we focus on the K-means clustering algorithm, and a data visualization interface based on the Browser/Server (B/S) mode is developed, which is mainly based on the Java language, supplemented by Cascading Style Sheets (CSS), JavaScript and HyperText Markup Language (HTML), with Tomcat, as the server and Mysql as the JavaWeb project of the rock burst monitoring data warehouse. The application of data mining technology in IEWSRB can improve the existing rock burst monitoring system and enhance the prediction. It can also realize real-time queries and the analysis of monitoring data through browsers, which is very convenient. Hence, it can make important contributions to the safe and efficient production of coal mines and the sustainable development of the coal economy.

Assessing Rockburst Hazards Using a Self-Developed Real-Time Microseismic Monitoring System in a Deep-Sea Goldmine

Deep-sea mining extracts ores on the ocean floor. During this process the sea water may flood into the mine due to rockburst hazards. This study proposes an effective method to assess rockburst hazards using a self-developed real-time microseismic monitoring system in Sanshandao goldmine (the first undersea mine in China). In addition, the wave dissimilation patterns of this mine have been elucidated by analyzing the signals obtained by the geophones embedded in a similar material model. The monitoring work started in December 2014 and ended in March 2015 in Sanshandao goldmine. To assess rockburst hazards, this study proposes several indexes including spatial-temporal distribution of microseismic events, microseismic activity rate, energy release rate, continuity index, and average daily energy. The results show that the surrounding rock went through the stationary, active, secondary stationary, and secondary active periods before rockburst occurrence. Compared with the stationary period, a sudden change of the continuity index and average daily energy can be observed in the active period in which minor rockbursts constantly occurred. Rockburst accidents are very likely to occur in the secondary active period. However, before this period, there usually exists a secondary stationary period without rockburst risk. This study proposes a workflow for designing and applying microseismic monitoring systems.

Prevention of rock burst by protective seam mining in high-depth strata: a case study

Several rock burst accidents occurred during the excavation of the 4th seam in a mine. Based on the geological and mining conditions of the mine, numerical simulation methods was adopted to analysis the protective effect of the upper and lower protective seam mining on the 4th seam, and the causes of rock burst occurring in the roadway of LW 1410 was explained. Further, the characteristics of stress distribution in 6th seam and 1th seam was discussed, this is the bases for determining the protective effects of upper and lower protective seam mining, as well as the critical pressure relief angle and the critical pressure relief point location in the 4th seam. These parameters would provide meaningful information for optimizing the roadway layout and preventing rock burst in the subsequent face mining of 4th seam.

The Influence of the Backfilling Roadway Driving Sequence on the Rockburst Risk of a Coal Pillar Based on an Energy Density Criterion

The rockburst hazard has always been an important issue affecting the safety production of coal mines in China. The unreasonable sequencing of roadway driving can lead to the dynamic instability of coal pillars, which subsequently causes rockburst accidents in roadway backfilling mining engineering and poses a serious threat to the safety of the mines. Roadway backfilling mining technology is an effective approach with which to mine corner residual coal resources under buildings, railways, and rivers. An energy density criterion is established and programmed with FISH language using numerical analysis software for the rockburst risk evaluation of coal pillars. On this basis, a numerical simulation model is established based on four scheme types, namely, the sequential mining, one-roadway interval mining, two-roadway interval mining, and three-roadway interval mining schemes. The influence of the backfilling roadway driving sequence on coal pillar stability is investigated, and the change law of vertical stress and energy density factor of coal pillars in different driving sequences in roadway backfilling mining technology are analyzed. According to the research results, the maximum energy density factor value of 21,172 J/m4 for coal pillars in one-roadway interval mining is the lowest among the different schemes. Therefore, the one-roadway interval mining scheme is the optimal choice in roadway backfilling mining technology. The results can be treated as an important basis for the prevention and treatment of coal pillar instability and rockburst in roadway backfilling mining technology.

Gas-solid coupling laws for deep high-gas coal seams

A better understanding of gas-solid coupling laws for deep, gassy coal seams is vital for preventing the compound dynamic disasters such as rock burst and gas outburst. In this paper, a gas-solid coupling theoretical model under the influence of ground stress, gas pressure, and mining depth is established and simulated by using COMSOL Multiphysics software. Research results indicate that under the influence of factors such as high ground stress and gas pressure, the mutual coupling interaction between coal and gas is much more significant, which leads to the emergence of new characteristics of gas compound dynamic disasters. Reducing the ground stress concentration in front of the working face can not only minimize the possibility of rock burst accidents, which are mainly caused by ground stress, but also can weaken the role of ground stress as a barrier to gas, thereby decreasing the number of outburst accidents whose dominant factor is gas. The results have a great theoretical and practical significance in terms of accident prevention, enhanced mine safety, disaster prevention system design, and improved accident emergency plans.

Rockburst mechanism in soft coal seam within deep coal mines

A number of rockburst accidents occurring in soft coal seams have shown that the rockburst mechanism involved in soft coal seams is significantly different from that involved in hard coal seams. Therefore, the method used to evaluate rockburst in hard coal seams is not applicable to soft coal seams. This paper established an energy integral model for the rockburst-inducing area and a friction work calculation model for the plastic area. If the remaining energy after the coal seam is broken in the rockburst-inducing area is greater than the friction work required for the coal to burst out, then a rockburst accident will occur. Mechanisms of “quaking without bursting” and “quaking and bursting” are clarified for soft coal seams and corresponding control measures are proposed as the optimization of roadway layouts and use of “three strong systems” (strong de-stressing, strong supporting, and strong monitoring).