Optimization Coal Pillar Size of Top Coal Caving Face with Dynamic Pressure Impact

2014 ◽  
Vol 675-677 ◽  
pp. 1395-1400 ◽  
Author(s):  
Wen Zhou Li

AH Wilson coal pillar was used widely as it’s simply, but it’s appeared large error for field implementation as its difference assume conditions, mine depth H and mine thickness m. AH Wilson coal pillar formula was studied precisely by in-site stresses test and numerical simulation analysis for N3-5 top coal caving working face of CHANGCUN coal mine in Lu’an coal district of China, then modified AH Wilson formula was put forward as L = 0.008mH + 8.4,then the precise coal pillar size 18m was used in filed implementation, filed testing proved coal pillar size was reasonable.

2012 ◽  
Vol 152-154 ◽  
pp. 1097-1101
Author(s):  
Zhong Dong Yang

Because of deep mining and the serious dynamic pressure appearance in Zhaogezhuang coal mine, this paper has statistical and analyzed phenomena of dynamic pressure appearance, and proposed the engineering defects method to relief the pressure for high stress zone of working face and roadway according to the actual situation, which can transfer the stress distribution of coal rock and release impact energy. Based on the numerical simulation analysis of pressure relief on cavity defects, it has analyzed the feasibility of pressure relief using engineering defect, acquired good effect of pressure relief and achieved the safety of coal mining in the 2337E working face.


2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Wenhao Guo ◽  
Anye Cao ◽  
Chengchun Xue ◽  
Yang Hu ◽  
Songwei Wang ◽  
...  

Coal mine pillar burst frequently occurs in Western China, which seriously restricts safe production. This paper takes the 35 m coal pillar of the 3102 working face of MKQ coal mine as the engineering background. The mechanism and evolution control of pillar bursts in multithick key strata are studied using field investigation, theoretical analysis, and numerical simulation. The mechanism of dynamic and static stress-induced pillar bursts was revealed combining the “O-X” broken features for key strata and numerical simulation of pillar stress evolution. A prevention scheme is put forward for strata presplit blasting and adjusting coal pillar width to minimize the dynamic and static stresses. The results demonstrate the following. (1) In the multithick strata, the first and second near-field subkey strata have perpendicular “O-X” broken features, whereas the third far-field subkey has parallel “O-X” broken features. The working face has three kinds of periodic weighting phenomena: long, medium, and short. (2) The simulated vertical stress curve of 35 m coal pillar goes through three states: two-peak, asymmetric trapezoidal and symmetrical trapezoidal shape with the different advancing position of working face. The stress concentration is extensively promoting a high-risk area for rock burst. (3) The coal pillar burst was induced by the superposition of energy released by the key strata breaking and the elastic energy accumulated in the wide coal pillar. (4) The monitoring data showed that the long, medium, and short periodic weighting steps of multithick key strata are 141.6 m, 43.2–49.6 m, and 17.6–27.2 m, respectively. The microseismic events energy, frequency, and stress of hydraulic support increment are the highest during the long periodic weighting, and the spatial distribution of microseismic events coincides with the stress concentration area. The theoretical analysis is confirmed with the field practice.


Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 211 ◽  
Author(s):  
Xiaoping Shao ◽  
Xin Li ◽  
Long Wang ◽  
Zhiyu Fang ◽  
Bingchao Zhao ◽  
...  

During strip backfilling mining in coal mines, the backfilling material is the main support structure. Therefore, studying the pressure law of the backfilling material is essential for the safe and efficient mining of coal resources. Based on research into strip backfilling mining at working face number 3216 of the Shanghe Coal Mine, and to smooth transition of overlying strata loads to the backfilling material, this study proposes a three-stage strip backfilling mining method. Based on thin-plate theory, an elastic thin-plate model, a reasonable spacing of strip mining is constructed, and the reasonable mining parameters of “mining 7 m to retain 8 m” at working face number 3216 of the Shanghe Coal Mine are determined. The law of backfilling pressure in three-stage strip backfilling mining is studied through numerical simulation and physical simulation experiments. The results show that field measurement results are basically consistent with the experimental results and numerical simulation results. When three-stage strip backfilling mining is adopted, the stage-one backfilling material is the main bearing body to which the overlying rock load transfers smoothly and gradually, and the structure of the “overburden-coal pillar (or backfilling strip)” in the stope remains stable. In three-stage strip backfilling mining, the overlying rock load is ultimately transferred to the stage-one backfilling material, the stage-two backfilling material is the auxiliary bearing body, and the stage-three backfilling material mainly provides long-term stable lateral support for the stage-one backfilling material.


2013 ◽  
Vol 807-809 ◽  
pp. 2288-2293 ◽  
Author(s):  
Xiang Qian Wang ◽  
Xiang Rui Meng ◽  
Zhao Ning Gao

Based upon the engineering background of IV315 coal mining face of Mengzhuang Coal Mine, the numerical simulation software UDEC is used to analyze rational packing width under the conditions of different filling widths on the driving roadway. The rational coal pillar size is initially decided as 2.0 meters through simulating and analyzing. On this basis, the influence of second mining on the retaining roadway was analyzed by numerical simulation. Combined with the field measurement, the support parameters and the 2.0 meters packing width are proven to be rational, which provides a reference for the coal mining faces with similar conditions.


2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Dongdong Chen ◽  
Chunwei Ji ◽  
Shengrong Xie ◽  
En Wang ◽  
Fulian He ◽  
...  

Aiming at the problem of large deformation and instability failure and its control of soft coal and soft roof roadway under intense mining, laboratory experiments, theoretical calculations, Flac3D numerical simulation, borehole peeping, and pressure observation were used to study the deflection characteristics of the deviatoric stress of the gas tailgate and the distribution and failure characteristics of the plastic zone in the mining face considering the strain softening characteristics of the roof and coal of roadway, and then the truss anchor cable-control technology is proposed. The results show the following: (1) The intense mining influence on the working face will deflect the peak deviatoric stress zone (PDSZ) of the surrounding rock of the gas tailgate. The influence distance of PDSZ is about 20 m in advance and 60 m in lag; the PDSZ at the gob side of the roadway is located in the range of 3–5.5 m from the surface of the coal pillar, while the coal wall side is mainly located in the range of 3–4.5 m at the shoulder corner and bottom corner of the solid coal. (2) The intense mining in the working face caused the nonuniform expansion of the surrounding rock plastic area of the gas tailgate. The two shoulder angles of the roadway and the bottom of the coal pillar have the largest damage range, and the maximum damage location is the side angle of the coal pillar (5 m). Angle and bottom angle of coal pillar are the key points of support control. (3) The plastic failure line of the surrounding rock of the gas tailgate is always between the inner and outer contours of the PDSZ, and the rock mass in the PDSZ is in a stable and unstable transition state, so the range of anchor cable support should be cross plastic failure line. (4) The theoretical calculations and numerical simulation results agree well with the drilling peep results. Based on the deflection law of the PDSZ and the expansion characteristics of the plastic zone, a truss anchor cable supporting system with integrated locking and large-scale support function is proposed to jointly control the roof and the two sides, which effectively solves the problem of weak surrounding rock roadway under severe mining deformation control problems realizing safety and efficient production in coal mines under intense mining.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yalong Li ◽  
Mohanad Ahmed Almalki ◽  
Cheng Li

Abstract For the comprehensive mechanised coal mining technology, the support design of the main withdrawal passage in the working face is an important link to achieve high yield and efficiency. Due to the impact of mining, the roof movement of the withdrawal passage is obvious, the displacement of the coal body will increase significantly, and it is easy to cause roof caving and serious lamination problems, and even lead to collapse accidents, which will affect the normal production of the mine. In this paper, the mining pressure development law of the main withdrawal passage support under the influence of dynamic pressure is designed, the most favourable roof failure form of the withdrawal passage is determined, and the action mechanism and applicable conditions of different mining pressure control measures are studied. The pressure appearance and stress distribution in the final mining stage of fully mechanised coal face are studied by numerical simulation. The deformation and failure characteristics and control measures of roof overburden in the last mining stage of fully mechanised coal face are analysed theoretically. Due to the fact that periodic pressure should be avoided as far as possible after the full-mechanised mining face is connected with the retracement passage, some auxiliary measures such as mining height control and forced roof blasting are put forward on this basis. The relative parameters of the main supporting forms are calculated. The main retracement of a fully mechanised working face in a coal mine channel is put forward to spread the surrounding rock grouting reinforcement, reinforcing roof, and help support and improve the bolt anchoring force, the main design retracement retracement channels in the channel near the return air along the trough for supporting reinforcing surrounding rock control optimisation measures, such as through the numerical simulation analysis, the optimisation measures for coal mine fully mechanised working face of surrounding rock is feasible. Numerical simulation results also show that the surrounding rock control of fully mechanised working face of coal mine design improvements, its main retreat channel under the roof subsidence, cribbing shrank significantly lower, and closer, to better control the deformation of surrounding rock, achieved significant effect, to ensure the safety of coal mine main retracement channel of fully mechanised working face support.


2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Qingwei Bu ◽  
Min Tu ◽  
Baojie Fu

Due to the change of ground stress environment caused by underground coal mining, the intense lateral mining stress concentration is formed around the stope; so section coal pillar is generally set up to bear the mining pressure, but the different sizes of coal pillars have obvious influence on the bearing capacity of those pillars and the characteristics of mining pressure. Mastering the mechanism characteristics by which coal pillars bearing capacity and mining stress distribution is crucial to identify the reasonable coal pillar size and give full play to the bearing role of section coal pillar, given their importance for the safety and bearing stability of engineering rock mass in underground coal mining. Therefore, the bearing characteristics of section coal pillar and the redistribution of mining stress are achieved with a mechanical model analysis on the basis of the analysis of coal pillar bearing and mining influence characteristics. Moreover, applying the elastic-plastic mechanics theory revealed the mechanical equations of the effective bearing size of coal pillar and redistribution of mining stress in longwall face. Combined with the analysis of a specific engineering example, the research results are as follows. During a roadway excavation, the continuous mining stress transfer occurs “stress redistribution” and the mechanical failure of bearing coal pillar consists of lateral mining and roadway side failures. The bearing coal pillar has two critical dimensions (i.e., the critical dimension W e of the self-bearing stability coal pillar and the critical dimension W p of failure through the coal pillar). The mechanical state of the lateral mining stress redistribution and bearing coal pillar is divided into the three situations: ① when the width of coal pillar W  <  W p , only one stress concentration area exists, the bearing capacity of the coal pillar is invalid at this stage, and the lateral mining stress concentration transfers to the roadway solid coal side; ② when the width of the coal pillar W e  ≥  W  ≥  W p , two stress concentration areas appear at this stage, and the coal pillar is in the critical state of self-bearing stability; ③ when the width of the coal pillar W  >  W e , three stress concentration areas are present, and the coal pillar at this stage is in a self-bearing stable state. Among all these factors, only the size of coal pillar is completely controllable, so the aspects of safe bearing and reserved size design of coal pillar, after estimating the critical size of coal pillar, the coal pillar size design is carried out according to the mine pressure control needs of mining engineering, and the cohesion, internal friction angle, interlayer friction coefficient, and coal seam mining height are improved by artificial technology, so as to realize the resource safe and efficient mining of all kinds of coal seam mining conditions; in the calculation of wide coal pillar size, the advance mining stress concentration at the end of the self-working face should be taken as the mining load condition, and the reserved size meets the condition of W  >  W e , thereby ensuring the stable bearing of the wide coal pillar despite the advanced mining stress concentration during the self-working face mining; in the calculation of narrow coal pillar size, the lateral mining stress concentration before mining should be taken as the mining load condition and the reserved size meets the condition W  <  W p , thereby realizing the effective transfer of mining stress concentration to the roadway solid coal side.


2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Bing-Jun Sun ◽  
Xin-Zhu Hua ◽  
Yan Zhang ◽  
Jiadi Yin ◽  
Kai He ◽  
...  

The mechanical model of the basic roof fracture structure is established on the basis of key block theory to study the roof breaking mechanism of gob-side entry retaining under roof cutting and pressure relief, and the analytical formula of roof support resistance is derived when the key block of the basic roof is stable. The influence of roof cutting angle and cutting height on roof support resistance is also analyzed. Determining the cutting seam parameters of the retained roadway roof is necessary to identify the support resistance of the roadway roof due to the correlation between the roof cutting parameters and the support resistance. Taking the II 632 haulage drift of the Hengyuan coal mine as the engineering background, FLAC3D numerical simulation is used in this paper to analyze the influence of different roof cutting angles and cutting heights on the surrounding rock structure evolution of retained roadways. Results show that the roof cutting angle and cutting height respond to the support resistance of the retained roadway roof, and the support resistance required by the roof increases with the roof cutting angle and cutting height. This condition ensures that the side roof of the gob can be cut off smoothly, and the support resistance required by the roof of retained roadways is within a reasonable range. Through theoretical and numerical simulation analysis, the reasonable roof cutting height of II 632 haulage drift is 8 m and the roof cutting angle is 15°. The theoretical analysis and numerical simulation results reveal that the required support resistance to maintain the stability of the roadway roof is 0.38 MPa. The supporting scheme of the roof of the II 632 haulage drift in the Hengyuan coal mine is then designed. Finally, the field industrial test is used for verification. The borehole imaging results show that the overall line of the retained roadway roof is small based on the description of field monitoring results. The deformation of the surrounding rock surface of the retained roadway is less than 100 mm, and the roadway is 40 m from the lagging working face. The deformation rate of surrounding rock decreases with the increase in distance from the working face. The integrity of the retained roadway roof is good, and the deformation of the surrounding rock is effectively controlled.


2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Xie Fuxing

The gob-side roadway of 130205, a large-mining-height working face in the Yangchangwan coal mine, was investigated in terms of the mine pressure law and support technology for large mining heights and narrow coal pillars for mining roadways. The research included field investigations, theoretical analysis, numerical simulation, field tests, and other methods. This paper analyzes the form of movement for overlying rock structure in a gob-side entry with a large mining height and summarizes the stress state and deformation failure characteristics of the surrounding rock. The failure mechanism of the surrounding rock of the gob-side roadway and controllable engineering factors causing deformation were analyzed. FLAC3D numerical simulation software was used to explore the influence law of coal pillar width, working face mining height, and mining intensity on the stability of the surrounding rock of the gob-side roadway. Ensuring the integrity of the coal pillar, improving the coordination of the system, and using asymmetric support structures as the core support concept are proposed. A reasonably designed support scheme for the gob-side roadway of the working face for 130205 was conducted, and a desirable engineering effect was obtained through field practice verification.


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