Mine Pressure Research Articles

Research and Application of Low Density Roof Support Technology of Rapid Excavation for Coal Roadway

The mismatch of speed of mining and excavating is the main contradiction of high efficiency production in China, improving the excavating speed of coal roadway is an effective way to solve the problem. According to the engineering geological conditions of the main haulage roadway 21205 in Hulusu Coal Mine, the technical problems existing in the original support scheme were analyzed, increased the excavating speed of roadway through improve support efficiency of single bolt and reducing density of bolt, a rapid excavation technology based on anchoring method of critical high efficiency and low density on roof of coal roadway was proposed. The influence of different bolt length and different pre-tightening force on the stability of roadway roof was studied by FLAC3D simulation, the results showed: (1) increasing the length and pre-tightening force can control the development of the roof vertical strain with a certain range; (2) as the length of bolt increases, the compressive stress zone of the rock layer between the two bolts increases and the compressive stress in the rock layer area of the anchorage section tends to increase; (3) with the increase of pre-tightening force, the effective, compressive stress zones between the two bolts overlap with each other, forming a whole, and the compressive stress values in the near zero stress zone increase. Decided the scheme that, bolt length is 4 m, pre-tightening force is 200 kN, and the support density is 0.5 root/m2, industrial experiments were carried out. The mine pressure monitoring showed that the roof of the roadway has almost no ionosphere, and the deep ionosphere was well controlled. The monthly excavating progress of the roadway was increased from 520 to 825 m, with a rise of 58.7%, the technical and economical effects were significant. It was proved that the scheme is in line with the actual. It can provide reference for roadway rapid excavating support technology for similar conditions.

Study on Overlying Strata Motion Rule of Shortwall Mining Face of Shallow Seam with Simulation Experiment

Taking Shendong mining area as a research object, the roof strata moving law in the shallow buried deep thin bedrock was studied with 3D simulation experiment. The results showed that the surface displacement and roof pressure decrease little, and the roof does not appear the phenomenon of full thickness cutting. As the advancing distance of the working face increases, the displacement of the surface and roof increases. The old roof breaking is not easy to form a hinge structure, the roof when the pressure of mine pressure appearance is very intense.

Study of An Innovative Approach of Roof Presplitting for Gob-Side Entry Retaining in Longwall Coal Mining

Gob-side entry retaining (GER) is a hot issue with regard to saving resources and reducing the drivage ratio in longwall mining. This paper investigates an innovative approach of roof presplitting for gob-side entry retaining (RPGER). RPGER uses the directional cumulative blasting to split the roof in advance. The rock roof within the presplitting range caves in gob after mining. The caved gangue can become the natural rib of the gob-side entry and expands to be the natural supporting body for resisting the upper roof movement. A numerical model of RPGER was established by the discrete element method (DEM), which showed that the supporting effect by the expanded gangue was well functioning. The gob-side entry was in pressure-relief surroundings and featured in the lesser deformation. The roof presplitting design method was presented and validated with a field test. The test illustrated that RPGER reduced the mining pressure on the retained entry side. The expanded gangue on the entry side was gradually compacted. It is the compaction process that played the role of reliving mining pressure, and the compacted gangue became the effective rib of the gob-side entry. The retained entry in the pressure-relief surroundings would stabilize a lagging distance behind the working face. The gob-side entry after stabilization met the entry retaining and the safety production requirements. This work illustrates the mechanism of RPGER and validates its feasibility and efficiency.

Современные математические методы прогноза условий поддержания и крепления горных выработок

The research focuses on mathematical methods of mining pressure forecast to develop rational support patterns for mining tunnels and to ensure safety of mining operations. The purpose of research is to develop the methodology of applying advanced calculation methods and software solutions based on neural networks to reduce dispersion of factors influencing stability of mining tunnels, as well as to define rational parameters of mining tunnel support. The authors review the algorithm of geomechanical process examination, which is divided into several stages. First of all, it is proposed to use cluster analysis to examine location conditions of man-made outcrops, which allows to divide all the diversity of existing conditions for mining tunnel construction. Cluster analysis first allows to reduce the dispersion of factors that influence the stability of mining tunnels in various clusters, and then to determine rational parameters of tunnel support in each cluster. After the problem of cluster analysis is solved, it is proposed to use software programs that allow to study geomechanical processes in each cluster. At this stage, both standard methods (normative techniques, numerical modelling, analogies use, etc.) and the most advanced methods – neural networks – can be applied. Described algorithm of solving geomechanical problems, which utilizes advanced numerical methods and a software package based on neural networks, ensures an individual approach to estimation of mining pressure under varying conditions of man-made outcrop location in the rock mass.

Experimental Research on Dynamic Evolution Characteristics of Roof Movement and Mining-Induced Stress of Superimposed Mining in a Close Distance Coal Seam Group

To obtain the evolution characteristics of roof movement and mining-induced stress, the evolution of roof movement and mining-induced stress are investigated during the mining of close coal seams based on 2# and 3 + 4# coal seams in Shaqu coal mine. The results show that characteristics of macro-migration for overlying strata by superimposed mining in close coal seams are similar to that in a single coal seam. Roof strata present coordinated migration of multiple strata, and the displacements increase progressively. Roof strata can alleviate ground pressure as a cushion due to 2# coal seam mining, which reflects the stress-weakening effect under superimposed mining in close coal seams. Compared with 2# coal seam mining, the interval, support load, and dynamic pressure coefficient are reduced during periodic weighting in the 3 + 4# coal seam, and some parts of the rock undergo step-like sink. Based on above results, the hydraulic supports with high-rated working resistance are selected for superimposed mining. Finally, there was no failure among hydraulic supports or other dynamic disasters because of auxiliary measures implemented, and intensive management attention, during periodic weighting.

Novel Segmented Roadside Plugging-Filling Mining Method and Overlying Rock Mechanical Mechanism Analyses

The no-pillar mining method is widely used in coal mining engineering because of its superiority in resolving mine pressure hazards and protecting natural resources. In view of the geological conditions of stable strata in a coal mine of the Shandong Coal Zone, a novel segmented roadside plugging-filling mining method is proposed by introducing the filling coefficient into roadside filling. The operation process is designed with a new grouting filling forming device. Based on the relationship between the theoretical deflection of a cantilever beam and geometric settlement and parallel settlement models, strength formulas applicable to the segmented roadside plugging-filling (SRPF) method at different migration stages are obtained, and the deformation formulas of a roadway toward a rock slab are solved by an elastic equivalent model. Further, the determination procedure of the filling mode under the mining method is clarified. The SRPF method was implemented on a test stope, and the test results indicated that the theoretical deformation produced by the SRPF method was small and can meet the mining requirements. Through on-site test monitoring, the deformation of surrounding rock was 0–160 mm and the filling body under the SRPF method could maintain its own strength and the stability of the surrounding rock. In addition, entire successful mining been completed in the working stope, which further proves the applicability of this method. The backfilling cost of the gob-side filling was reduced by approximately 50%, and the backfilling efficiency was improved in the mine. The description of the novel mining method may provide theoretical and practical guidance for coal mining in similar geological conditions.

Experimental Study on the Width of the Reasonable Segment Pillar of the Extremely Soft Coal Seam in the Deep Mine

Various dynamic disasters will happen in the extremely soft coal seam mining process of Gob-side entry in the deep mine, including large deformation of roadways, rock burst, gas unusual, floor water invasion, spontaneous combustion of coal seam and so on. Therefore, a reasonable segment pillar will not only avoid the dynamic disasters in the excavating process, but also improve the resource utilization. Taking the goaf working face of extremely soft coal seam in the deep mine in one particular mine of Shandong Province as the engineering example, this paper first analyzes optional locations of the gob-side entry, finding that the gob-side entry should be located in the low stress block and it’s the most favorable to keep small pillars and goafs isolated. Then, it is found that small surrounding rock deformation of gob-side entry takes place in the driving process through the numerical simulation, and the deformation will increase with the increasing width of the chain pillar. The surrounding rock deformation of gob-side entry increases in the stoping stage. Small width of the chain pillar will easily result in the instability of the roadway. As the swivel angle of the basic roof increases, the surrounding rock deformation of gob-side entry will accordingly increase. Finally, the numerical calculation and on-spot mine pressure monitoring illustrate that the width of the segment pillar in the gob-side entry should be 5–7 m, with 6 m the best.

Entry Deformation Law in the Full Life Cycle Under Entry Retaining with Roof Cutting

In roof cutting pressure releasing gob-side entry retaining (RCPRGER) technology, the full life cycle of the retained entry includes two main parts: the entry retaining and retained entry reuse. The existing studies all focus on the process of entry retaining, while the studies of the whole life cycle and reuse process are relatively deficient. To compensate for the deficiency in the existing research and explore the deformation law of the entry in the whole life cycle under entry retaining with roof cutting, this paper takes the 8304 and 8305 working faces of the Tashan Coal Mine as an example, and the entry deformation evolution in the retaining and reuse processes is studied. First, this paper summarizes the technological process of RCPRGER and reuse and then deduces the stress evolution process of entry surrounding rocks, specifically including the analysis of the roof cutting short beam structure model. Subsequently, the monitoring schemes of the entry deformation and mine pressure in the working face within the retaining and reuse processes are proposed. Finally, through the practical examples of test working faces, it is found that the two entry sides move symmetrically between the upper and lower parts. The main deformation in the early stage of the entry retaining is the displacement of the gangue wall, and the main deformation in the later stage and reuse stage is the displacement of the coal wall. The roof and floor move asymmetrically between the left and right parts, the deformation of the roof cutting side is larger at each stage, and the roof subsidence is the main source of deformation.

Mine Pressure Observation and Support Adaptability Analysis of Fully Mechanized Caving Face in Soft Rock Mine

According to the data monitored by the top pressure gauge of the I0128204 fully mechanized caving face in Yannan Mine, the statistical analysis method is used to analyze the adaptability of the hydraulic support. The results show that the ZFS6400-15.7/31 bracket support strength is suitable for soft rock fully mechanized caving. It provides technical guarantee and reference basis for the selection of similar working face brackets.

A General Review on Longwall Mining-Induced Fractures in Near-Face Regions

It is believed that underground longwall mining usually produces fractures in the surrounding rocks. On the one hand, mining-induced fractures not only degrade the strength of the rock mass but also serve as main channels for fluids (e.g., water and methane). Fractures facilitate the failure of the rock mass and fluid inrush into working spaces. Therefore, mining-induced fractures are significant for the safety evaluation of underground structures and finding feasible solutions. On the other hand, the fractures are also beneficial for methane collection and coal fragmentation, which are essential for the successful operation of longwall top coal caving mining. Therefore, determining the characteristics of induced fractures is significant for underground longwall mining. From a global perspective, longwall mining-induced fractures in the overburden have been well studied, which improves the understanding of the mining pressure and ground control. However, induced fractures near the longwall face, which have more significant effects on mining activities, have not been summarized. The goal of this review paper is to provide a general summary of the current achievements in characterizing mining-induced fractures in near-face regions. The characteristics of mining-induced fractures in the coal wall, chain pillar, immediate roofs and top coal, and floors are reviewed and summarized. Remarks are made on the current progress of, fundamental problems with, and developments in methodologies for characterizing mining-induced fractures using methods such as field observations, small-scale laboratory tests, physical modeling, and numerical modeling. Based on a comprehensive analysis, the advantages and disadvantages of each method are discussed, and the ideal conditions for applying each of these methods are also recommended.

Inversion Analysis of Crustal Stress Distribution Law in Gully Geomorphic Mining Area

In order to study the distribution law of crustal stress in gully geomorphic mining area, stress relief method is used to measure the crustal stress at the limited points in the mining area. Based on the measured results of crustal stress at each measuring point, the crustal stress distribution law in the mining area is inversely analyzed by using numerical simulation software. Research shows: The crustal stress of Wangjialing Mine is closely related to its gully geomorphological characteristics. The crustal stress and the mining pressure of shallow-buried gully have great influence on coal mining. Compared with the tectonic stress, the damage of the vertical stress to the underground roadway is not obvious, and the horizontal tectonic stress is the main force source of the roadway instability and deformation. The maximum principal stress, the intermediate principal stress and the minimum principal stress all increase with the increase of burial depth. The difference between the intermediate principal stress and the minimum principal stress is small, and the change of lateral pressure coefficient is not obvious with the increase of burial depth.

Comparative analysis of the mine pressure at non-pillar longwall mining by roof cutting and traditional longwall mining

Abstract Non-pillar coal mining has been developed and implemented in the recent decades in China's coal mining industry. The non-pillar longwall mining by roof cutting without pre-excavated entry (N00 mining method) is one of the latest non-pillar mining methods and this method has the advantages of reduced roadway drivage ratio and increased resource recovery ratio. Previous studies show that the mining pressure during the working face advancing is one of the main factors that affect the stability of underground structures and the safety production. However, there is no evaluation or analysis of the mining pressure at the mining face using entry retaining with roof pre-cutting and an absence of pre-excavated tail entry. In this paper, both field monitoring and numerical simulation approaches are employed in the analysis of the mining pressure distribution characteristics within a range of the whole working face during the face advancing. The results are compared with the field data and simulation results from the traditional mining method performed in the same coal mine. Results supported the idea that the N00 mining method can generate a low-stress area for the retained entry. The stability of the working face and retained entry can be well maintained due to the mine pressure optimization. This paper can aid in the understanding of structural mechanic modeling and mine pressure distribution features, structural mechanic analysis and mine pressure distribution features of the N00 mining method.

Numerical simulation analysis of mine pressure distribution of shallow coal seam by truncated short wall beam theory

Numerical simulation analysis of mine pressure distribution of shallow coal seam by truncated short wall beam theory

Finite element method applied in mine pressure computation within the context of rock massif – support system interaction

This work was developed from a theoretical and experimental study on the stability analysis of underground workings located in strongly metamorphosed andesite and determination of mine pressure in the context of rock – support system interaction. We thank to our colleague dr. Gabriel Babuţ for his assistance and support in developing the mathematical model based on the principle of proper conformity and safety level, according to the main factors that influence the stability of underground workings. We would also like to show our gratitude to the University of Petrosani which provided the necessary equipment to perform all laboratory tests in prior experimental researches leading to the results synthesized in this article.

Influence of Different Propulsion Speeds on the Characteristics of Mine Pressure in the Fully Mechanized Caving Face During Rotary Stage

Owing to the influence of advancing speed, the movement characteristics of roof are special, and there exists a risk of pressure frame and roof fall. To understand the influence of the advancing speed on the strata pressure distribution of the fully mechanized top-coal caving roadway during the transition period, this study takes the 301 fully mechanized top-coal caving face of Changchun Xing coal mine as the engineering background. The influence of the advancing speed on the distribution of the abutment pressure is analyzed on the basis of the elastic foundation beam theory, and the characteristics of strata pressure display are verified by both numerical simulation and field measurement. The results show that when the advancing speed of the working face increases, the value of the bearing pressure at the azimuth position in front of the working face also increases. Within a certain range, the peak value of the bearing pressure at the front of the working face is proportional to the advancing speed, and the position of the peak value of the supporting pressure in advance is closer to the working face. The conclusions obtained can provide technical support for stop and end surrounding rock control measures in similar working faces.

Migration Law of the Roof of a Composited Backfilling Longwall Face in a Steeply Dipping Coal Seam

The artificial-caved rock composited backfilling approach can effectively restrain the dynamic phenomena in the coal seam and the associated roof and floor during mining operations, and can also improve the stability of the system of support and surrounding rock. In this study, based on the analysis of influencing factors affecting the surrounding rock movement and deformation of the composited backfilling longwall face in a steeply dipping coal seam, the roof mechanical model is developed, and the deflection differential equation is derived, to obtain the roof damage structure and the location of the roof fracture for the area without backfilling. The migration law of the roof under different inclination angles, mining depths, working face lengths, and backfilling ratios are analyzed. Finally, mine pressure is detected in the tested working face. Results show that the roof deflection, bending moment, and rotation drop with the increase of the inclination angle and backfilling ratio, whereas these parameters increase with greater mining depth and working face length. The roof failure location moves toward the upper area of the working face as the inclination angle and working face length increases, while it moves toward the center of the non-backfilling area with greater mining depth and backfilling ratio. Results from the proposed mechanical model agree well with the field test results, demonstrating the validity of the model, which can provide theoretical basis for a safe and efficient mining operation in steeply dipping coal seams.

Study on Mechanism of In-Situ Stress Control on the Coal Floor Damage During Deep Coal Seam Mining

In order to study on mechanism of in-situ stress control on the coal floor damage during deep coal seam mining, the internal relationship among ground stress, mine pressure and floor water inrush was analyzed base on the increasing distribution rule of ground stress with the increasing depth of stratum. It is shown that the stress on the deep coal seam has obvious control effect on the depth of the floor damage and failure through the numerical simulation and the statistical analysis of the measured data of the mining damage depth of the coal seam floor. And the calculation formula for the depth of the floor failure in the deep seam mining and the influence coefficient of the ground stress were put forward.

Research on Distribution and Evolution Laws of Surrounding Rock Stress During the Island Panel Mining in Multiple Complex Stope

This paper was to explore distribution and evolution of surrounding rock stress as well as roadway deformation failure during the exploitation of working faces in complex stope. Here, distribution and evolution laws of surrounding rock stress and strata pressure behaviors in the complex island panels 1213(1) in a mine in Huainan Mine during early isolation, overhead mining, normal isolation and stopping in gob were analyzed by combining FLAC3D numerical simulation and field measurement. Results were shown that surrounding rock stress distribution along the strike direction and incline direction, abutment pressure peak value and position as well as surrounding rock deformation in the roadway were different in different mining stages. Different spatial stope layout (left and right gob, lower gob and upper gob) could influence the abutment pressure distribution on working faces, stress concentration range and surrounding rock deformation in roadway significantly. Therefore, professional analysis, reasonable design and safety mining should be performed in advance according to specific engineering geological conditions. Research conclusions could provide certain engineering references and guidance to stope arrangement, optimal design of mining roadway and mine pressure control.

Patrimônio-territorial e saber local

A história de luta pela criação do Projeto de Assentamento (PA) de Reforma Agrária Cafundão está vinculada à historicidade da concentração fundiária brasileira, que dá sentido de existência aos movimentos sociais pelo acesso à terra. Como também, descreve particularmente uma luta pela efetivação de uma política brasileira específica, de forma a reconhecer a posse desta mesma terra – que já era lugar de vida há gerações -, no âmbito de pressões imobiliárias e minerárias que a circundam. Singularmente, a luta do Cafundão retrata o reconhecimento político do saber local (torneamento do esteatito em produção artesanal) como principal vínculo (re)produtivo (n)às terras do Cafundão, o que garante a sobrevivência destas famílias e nutre a validação de suas narrativas de pertencimento. Neste artigo, se dialoga sobre a ativação do patrimônio-territorial por meio do saber local.

Integrated monitoring and control technology for stability of room and pillar goaf

In order to solve the technical problems of prevention and control of dynamic mining pressure in coal seam mining at the lower part of the room and pillar goaf with short distance coal seam, based on the surface movement deformation monitoring, the internal multipoint displacement monitoring of rock mass, the working face support resistance monitoring, the working face micro-seismic monitoring joint undermine and surface, integrated monitoring of stability of room and pillar goaf was realized, and the technical measures for preventing and controlling the dynamic pressure of longwall fully mechanized mining in the lower coal seam under the room and pillar goaf are proposed. The results show that integrative monitoring technology is a comprehensive, real-time and reliable method for monitoring the stability of room and pillar goaf, integrative monitoring technology has a good application effect on guiding the safe production of long wall fully mechanized mining under room and pillar goaf in western mining area and controlling the dynamic mining pressure.