scholarly journals A Study on the Mechanism of Dynamic Pressure during the Combinatorial Key Strata Rock Column Instability in Shallow Multi-coal Seams

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Jie Zhang ◽  
Bin Wang ◽  
Wenyong Bai ◽  
Sen Yang
Keyword(s):  
Dynamic Load ◽  
Dynamic Pressure ◽  
Coal Pillar ◽  
Mine Pressure ◽  
Key Strata ◽  
Column Type ◽  
Type Fracture ◽  
Mining Face ◽  
Rock Column ◽  
Overlying Strata

In order to study the pressure changes and support failure in mining face under concentrated coal pillar in shallow coal seam, the concentrated coal pillar in 30105 working face of Nan Liang Coal Mine was selected as the research object. In this study, the mechanism of dynamic mine pressure in mining face under concentrated coal pillar was investigated through multiple simulation experiments, numerical simulations, and theoretical analysis. The results of similar simulation experiment indicate that the dynamic mine pressure occurred at 25 m under the concentrated coal pillar and 7 m beyond the coal pillar. The strata roof was observed with sliding down, resulting in collapse and severe fractures commonly seen in rock column. The overlying strata caused the overall subsidence and collapse synchronously, resulting in the sudden increase of the resistance of the support in the working face, and the dynamic load coefficients reach 3.4 and 3.5. The theoretical analysis indicates that the two hard strata in the overlying strata of 3−1 coal meet the theoretical criterion of the combined key strata with the concentrated coal pillar of 2−2 coal in the weak interlayer of the combined key strata. The combined key strata bear the load of the whole overlying strata. The sliding instability featured with the rock column-type fracture located in the combined key strata is considered as the primary trigger of the abnormal resistance of the support and the dynamic mine pressure in the mining face under the concentrated coal pillar. The dynamic pressure model of “combination key strata—immediate roof-support” was established, along with the dynamic load coefficient calculation related to the rock column-type fracture and instability. The characteristics of dynamic load coefficient of the rock column-type fracture and instability under different overlying rock structure conditions were analyzed, providing references and insights into mining under similar geographic conditions.

scholarly journals Movement Laws of Overlying Strata above a Fully Mechanized Coal Mining Face Backfilled with Gangue: A Case Study in Jiulishan Coal Mine in Henan Province, China

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Zhengkai Yang ◽  
Zhiheng Cheng ◽  
Zhenhua Li ◽  
Chunyuan Li ◽  
Lei Wang ◽  
...  
Keyword(s):  
Coal Mining ◽  
Main Roof ◽  
Surrounding Rock ◽  
Surface Subsidence ◽  
Key Strata ◽  
Key Stratum ◽  
Mining Face ◽  
Failure Depth ◽  
Gangue Backfilling ◽  
Overlying Strata

The aim of this study is to obtain movement laws of overlying strata above a fully mechanized coal mining face backfilled with gangue and solve the problem of surface subsidence during coal mining. This study was carried out based on gangue backfilling mining of Jiulishan Coal Mine (Jiaozuo City, Henan Province, China) from the perspectives of deformation of backfilled gangue under compaction, surrounding rock of a stope, and activities of key strata. The method combining with rock mechanics, viscoelastic mechanics, control theory of rock mass under mining, and numerical simulation was used based on physical and mechanical characteristics of backfilled gangue. On this basis, the research analyzed the temporal-spatial relationships of activities of surrounding rock of the stope, compressive deformation of backfilling body, failure depth of the floor, deformation characteristics of the main roof with laws of surface subsidence. The movement characteristics of overlying strata above the fully mechanized coal mining face backfilled with gangue and the traditional fully mechanized mining face were compared. It is found that, under the same conditions of overlying strata, movement laws of overlying strata are mainly determined by the mining height of coal seams and the heights of a caving zone and a fracture zone are nearly linearly correlated with the mining height. Through analysis based on thin-plate theory and key stratum theory, the location of the main roof of the fully mechanized coal mining face backfilled with gangue in coal seams first bending and sinking due to load of overlying strata was ascertained. Then, it was determined that there are two key strata and the main roof belongs to the inferior key stratum. By using the established mechanical model for the main roof of the fully mechanized coal mining face backfilled with gangue and the calculation formula for the maximum deflection of the main roof, this research presented the conditions for breaking of the main roof. In addition, based on the theoretical analysis, it is concluded that the main roof of the fully mechanized coal mining face backfilled with gangue does not break, but bends. The numerical simulation results demonstrate that, with the continuous increase of strength of backfilled gangue, the stress concentration degree of surrounding rock reduces constantly, so does its decrease amplitude. Moreover, the compressive deformation of backfilling, failure depth of the floor, and bending and subsidence of the main roof continuously decrease and tend to be stable. The mechanical properties of backfilling materials determine effects of gangue backfilling in controlling surface subsidence. Gangue backfilling can effectively control movement of overlying strata and surface subsidence tends to be stable with the increase of elastic modulus of gangue.

scholarly journals Research on Fault Activation Law in Deep Mining Face and Mechanism of Rockburst Induced by Fault Activation

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Lyu Pengfei ◽  
Bao Xinyang ◽  
Lyu Gang ◽  
Chen Xuehua
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Coal Pillar ◽  
Fault Structure ◽  
Fault Activation ◽  
Fault Type ◽  
Stress Behavior ◽  
Mining Face ◽  
And Control ◽  
The Impact

To effectively monitor and control the severe mining-induced rockburst in deep fault area, the fault activation law and the mechanical essence of rockburst induced by crossing fault mining were studied through theoretical analysis, microseismic monitoring, field investigation, and other methods; numerical simulation was employed to verify the obtained fault activation law and the mechanical nature. First, the distribution of microseismic sources at different mining locations and the fault activation degree were analyzed. According to the microseismic frequency and the characteristics of the energy stage, the fault activation degree was divided into three stages: fault stress transfer, fault pillar stress behavior, and fault structure activation. It was determined that the impact disaster risk was the strongest in the stage of the fault pillar stress behavior. Based on the periodic appearance law of microseisms in fault area, three types of conceptual models of fault-type rockburst were proposed, and the rockburst carrier system model of “roof-coal seam-floor” in the fault area was established. The mechanical essence of fault-type rockburst was obtained as follows: under the action of fault structure, the static load of the fault coal pillar was increased and superimposed with the active dynamic load of the fault, leading to high-strength impact disaster. Finally, the prevention and treatment concepts of fault-type rockburst were proposed. The monitoring and prevention measures of fault-type rockburst were taken from two aspects: the monitoring and characterization of fault rockburst and weakening control of the high static load of the fault coal pillar and dynamic load of fault activation. The proposed concepts and technical measures have been verified in the working face 14310 of Dongtan Coal Mine with sound results. The research results have a guiding significance for the prevention and control of rockburst in a similar mining face under crossing fault mining.

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

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Haifeng Zhou ◽  
Qingxiang Huang ◽  
Yingjie Liu ◽  
Yanpeng He
Keyword(s):  
Coal Pillar ◽  
Coal Extraction ◽  
Mine Pressure ◽  
Prevention Measures ◽  
Overburden Pressure ◽  
Load Pressure ◽  
Working Face ◽  
Coal Wall ◽  
Numerical Simulation Methods ◽  
Mining Face

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.

scholarly journals Stability Analysis of Roadway Groups under Multi-Mining Disturbances

2021 ◽  
Vol 11 (17) ◽  
pp. 7953
Author(s):  
Yuantian Sun ◽  
Ruiyang Bi ◽  
Qingliang Chang ◽  
Reza Taherdangkoo ◽  
Junfei Zhang ◽  
...  
Keyword(s):  
Coal Mining ◽  
Coal Pillar ◽  
Stability Control ◽  
Surrounding Rock ◽  
Key Strata ◽  
Working Face ◽  
Roadway Stability ◽  
Mining Disturbance ◽  
Mining Face ◽  
The Stability

The roadway stability has been regarded as the main challenging issue for safety and productivity of deep underground coal mines, particularly where roadways are affected by coal mining activities. This study investigates the −740 m main roadway in the Jining No. 2 Coal Mine to provide a theoretical basis for the stability control of the main deep roadway affected by disturbances of adjacent working activities. Field surveys, theoretical analyses, and numerical simulations are used to reveal mechanisms of the coal mining disturbance. The field survey shows that the deformation of roadway increases when the work face advances near the roadway group. Long working face mining causes the key strata to collapse based on the key strata theory and then disturbs the adjacent roadway group. When the working face is 100 m away from the stop-mining line, the roadway group is affected by the mining face, and the width roadway protection coal pillar is determined to be about 100 m. Flac3D simulations prove the accuracy of the theoretical result. Through reinforcement and support measures for the main roadway, the overall strength of the surrounding rock is enhanced, the stability of the surrounding rock of the roadway is guaranteed, and the safe production of the mine is maintained.

scholarly journals Characteristics of Stratum Structure and Fracture Evolution in Stratified Mining of Shallow Buried High-Gas-Thick Coal Seam by Similarity Simulation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Qin Guangpeng ◽  
Cao Jing ◽  
Wang Chao ◽  
Wu Shuo ◽  
Zhai Minghua
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Coal Pillar ◽  
Structure Evolution ◽  
Thick Coal Seam ◽  
Fracture Structure ◽  
Working Face ◽  
Rock Structure ◽  
Type Fracture ◽  
Overlying Strata

The stratified mining of super thick coal seam is a process of repeated disturbance of the top roof, especially in the lower stratification, the upper complex rock layer has a greater settlement space, resulting in great changes in the strata structure and fissure distribution. The main coal seam thickness of Rujigou Coal Mine exceeds 20 m, due to the high gas content of the coal seam, it is prone to spontaneous combustion, and the stratified mining method is adopted. When a small-size section coal pillar (less than 10 m) is used, the complex rock structure evolution and fissure development characteristics during the stratified mining of shallow buried thick coal seam will directly affect the movement of gas transportation between the working face and the goaf and will directly affect the safety of the working face. Taking Rujigou coal mine as engineering background, this paper analyzes the breaking structure, fracture development, and evolution law of overlying strata in different layers and different sections of coal seam when the buried depth is shallow, and the extra-thick coal seam is stratified mining. The results show that in the process of stratified mining, the overlying strata break, in addition to the whole trapezoidal failure structure, will also form a local F type fracture structure, and with the stratified downward mining, the F type fracture structure will continue to move up and disappear until it is compacted. The “V” type and “U” type subsidence characteristics of different strata overburden are presented after mining in stratified working face of extra-thick coal seam, and the subsidence amount is approximately symmetrical distribution along the middle line of goaf. In the mining process of the lower part of the layer, the end broken rock block is easy to slip along the hinge point by the hinged rock beam structure, and the sliding instability occurs. In the process of stratified mining of ultrathick coal seam, the main fissure of overburden is mainly longitudinal fissure, and it is very easy to form through with the upper layer and will finally connect with the surface under the condition of shallow buried depth. The inclined cracks connected with the adjacent goaf are formed above the coal pillar of the section, which becomes the passage of gas migration in the goaf. The research conclusion shows that for the stratified mining of high gas thick coal seam, special attention should be paid to the treatment of the gas on the stratified working face. In addition to the conventional gas treatment measures such as coal seam prepumping, the buried pipe pumping in the mining area can also be adopted, which can effectively reduce the gas concentration of the working surface.

scholarly journals Physical Modeling of the Controlled Water-Flowing Fracture Development during Short-Wall Block Backfill Mining

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Yun Zhang ◽  
Yongzi Liu ◽  
Xingping Lai ◽  
Jianming Gao
Keyword(s):  
Coal Pillar ◽  
Similarity Criterion ◽  
Test Results ◽  
Control Effect ◽  
Physical Similarity ◽  
Wall Block ◽  
Fracture Development ◽  
Backfill Mining ◽  
Backfill Materials ◽  
Overlying Strata

Abstract Short-wall block backfill mining (SBBM) technology is an effective method to solve the environmental problems in the mining process. Based on the technical characteristics of SBBM technology and the physical similarity criterion, the physical similarity models for comparing the control effects of water-flowing fracture (WFF) development using short-wall block cave mining (SBCM) and SBBM were established, and the deformation and the WFF development of overlying strata above gob were monitored. The test results determined that the composite materials of 5 mm thick pearl sponge+5 mm thick sponge+10 mm thick paper+6 mm thick board were adopted as the similar backfill materials by comparing the stress-strain curves between the similar backfill materials and the original gangue sample. When the backfilling body was filled into the gob, it would be the permanent bearing body, which bore the load of the overlying strata accompanied with the protective coal pillar. At the same time, the backfilling body also filled the collapse space of overlying strata, which was equivalent to reduce the mining height, and effectively reduced the subsidence and failure height of the overlying strata. Compared with SBCM, the test results showed that the maximum vertical deformation, the height of water-flowing fractured zone, and activity range of overlying strata using SBBM were reduced by 91.4%, 82.5%, and 64.9%, respectively. SBBM had a significant control effect on strata damage and WFF development, which could realize the purpose of water resource protection in coal mines.

scholarly journals Study on Occurrence Mechanism of Coal Pillar in L-Shaped Zone during Fully Mechanized Mining Period and Prevention Technology

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zeng-qiang Yang ◽  
Hong-mei Wang ◽  
De-quan Sun ◽  
Xian-jian Ma ◽  
Ming-bao Xu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Rock Burst ◽  
Dynamic Load ◽  
Static Load ◽  
Coal Pillar ◽  
Simulation Software ◽  
In Situ Investigation ◽  
Simulation Results ◽  
Occurrence Mechanism

In order to study the occurrence mechanism of rock burst in L-shaped zone during a fully mechanized mining period, the No. 705 working face which is located in Baojishan Colliery is taken as a typical engineering background. By means of in situ investigation, theoretical analysis, numerical simulation, in situ tests, and relevant monitoring methods, the occurrence mechanism of rock burst and corresponding prevention technology are studied. The results show that a coal pillar with some confining pressure in the L-shaped zone is established by FLAC3D numerical simulation software, and the numerical simulation results indicate that the change in static load has a greater effect than dynamic load on coal pillar unstable failure; the static load plays a role in storing energy, and dynamic load plays a role in inducing rock burst; the bolt-mesh-cable support and high-pressure water jet unloading combined technology is put forward to prevent rock burst in roadways, and the numerical simulation results show that stress distribution of surrounding rock meets the model of strong-soft-strong (3S) structure, and the moment distribution is reasonable. In the follow-up mining, a limit value of coal fines is used to determine that this measure is a reasonable method to prevent rock burst. The study conclusions provide theoretical foundation and new guidance for preventing rock burst by synergistic effect technology in roadways.

scholarly journals New Method to Design Coal Pillar for Lateral Roof Roadway Based on Mining-Induced Stress: A Case Study

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Feng Wang ◽  
Shaojie Chen ◽  
Jialin Xu ◽  
Mengzi Ren
Keyword(s):  
Stress Distribution ◽  
Coal Pillar ◽  
In Situ Stress ◽  
New Method ◽  
Maximum Deformation ◽  
Induced Stress ◽  
Stress Contour ◽  
Longwall Panel ◽  
Overlying Strata

The traditional method to design coal pillar for lateral roof roadway was established based on the mining-induced strata movement contour which is considered as a straight line, while ignoring the variations of the internal strata deformation law as well as stress distribution characteristics. In order to make up for this deficiency, in this study, evolution of mining-induced stress in the overlying strata was simulated using physical and numerical simulations, and a method to design coal pillar for lateral roof roadway based on mining-induced stress was proposed. The results indicate that the stress of the overlying strata is redistributed during excavation, and the stress distribution can be divided into a stress-relaxation area, a stress-concentration area, and an in situ stress area. The contour line of 1.05 times the in situ stress is used to define the mining-induced stress contour. Stress inside the contour is redistributed while outside the contour the overlying strata are still within the in situ stress area. Mining-induced stress contour presents a concave-upward type from coal seam to the overlying strata that cannot be merged into a straight one due to their different characteristics of movement and deformation. With this in mind, this study proposed a method to design the width of coal pillar for lateral roof roadway according to the mining-induced stress contour. According to mining-induced stress contour, the width of coal pillar for lateral roof roadway of longwall panel 31100 is 160 m, and the maximum deformation of the roadway is 270 mm. The new method can definitely meet engineering demands.

Sign in / Sign up

Export Citation Format

Share Document