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1.
This study presents a numerical investigation on the dynamic mechanical state of a coal pillar and the assessment of the coal bump risk during extraction using the longwall mining method. The present research indicates that there is an intact core, even when the peak pillar strength has been exceeded under uniaxial compression. This central portion of the coal pillar plays a significant role in its loading capacity. In this study, the intact core of the coal pillar is defined as an elastic core. Based on the geological conditions of a typical longwall panel from the Tangshan coal mine in the City of Tangshan, China, a numerical fast Lagrangian analysis of continua in three dimensions (FLAC3D) model was created to understand the relationship between the volume of the elastic core in a coal pillar and the vertical stress, which is considered to be an important precursor to the development of a coal bump. The numerical results suggest that, the wider the coal pillar, the greater the volume of the elastic core. Therefore, a coal pillar with large width may form a large elastic core as the panel is mined, and the vertical stress is expected to be greater in magnitude. Because of the high stresses and the associated stored elastic energy, the risk of coal bumps in a coal pillar with large width is greater than for a coal pillar with small width. The results of the model also predict that the peak abutment stress occurs near the intersection between the mining face and the roadways at a distance of 7.5 m from the mining face. It is revealed that the bump-prone zones around the longwall panel are within 7–10 m ahead of the mining face and near the edge of the roadway during panel extraction.  相似文献   

2.
The paper presented the research on the dynamic advanced abutment stress induced by longwall mining with borehole stress meters on mining side coal mass. Twenty vibrating wire borehole stress meters were installed into the extracting coal mass wall of a first mining roadway of 910 m depth in Zhuji Coal Mine, China, and were used to monitor dynamic changes in vertical and horizontal stresses. Three months of continuous monitoring and further analysis showed that the impacting distance of advanced abutment stress induced by mining in the strike of the working face along its central axis was the farthest, greater than 250 m (the face length is 220 m); it gradually decreased in the radial direction of the face from its central axis outward; the pressure peak was located within 24 m in the front of the mining coal wall; non-synchronous caving of the layered mudstone roof at the stope occurred. Comparison between vertical and horizontal stress increments indicated that the horizontal stress was much smaller than the vertical stress in the coal mass of mining side, while the latter’s magnitude determined the drastic degree of mine pressure manifestation. The study has been applied to determine the advanced support length of the working face and further provide a reliable basis to forecast such dynamic disasters as rock burst, coal and gas outburst, etc., as well as to design the asymmetric supports on both sides of a gateway.  相似文献   

3.
Goaf-side entry driving in underground coal mines could greatly improve coal recovery rates. However, it becomes more difficult to maintain stability, especially in deep coal mines. Pillar width plays a pivotal role in the stability of goaf-side entry driving. To obtain a reasonable and appropriate narrow pillar width, theoretical calculations of the widths of mining-damaged zone and limit equilibrium zone in the pillar are derived according to limit equilibrium theory. Based on the stability issues of goaf-side entry driving in the first island longwall coal face (LCF) at a depth of 800 m below the surface in Guqiao Coal Mine in China, a numerical model is established by FLAC software to analyze the stability of the surrounding rock of goaf-side entry driving during excavation, using various coal pillar widths and support schemes. The results obtained from theoretical calculations, numerical simulation, and engineering practice indicate that an 8-m-wide coal pillar is relatively reasonable, appropriate, and feasible. Field measurements show that deformations of the surrounding rock could be efficiently controlled 31 days after the support schemes were implemented in goaf-side entry driving with an 8-m-wide narrow pillar along the adjacent goaf side with a compaction duration of 10 months. The mining influence range of the overlying LCF on the stability of goaf-side entry driving is found to be the area from 50 m ahead of the LCF to 70 m behind the LCF as it passes over the measurement point.  相似文献   

4.
Intensive strata behaviors are generated when the No. 8707 working face of the 8# coal seam in a coal mine is advanced by way of the pillars left over of the upper part of 7# close distance coal seam. The theoretical analysis, numerical simulation and filed measurement were utilized to obtain the rule of the stress change when the 8707 working face of the 8# coal seam passes the pillars left over of the 7# coal seam. Meanwhile, a pressure-relief mining (PRM) technology was put forward. According to the research results, when the 8707 working face in the 8# coal seam was advanced to the position that was 20 m in front of the pillar left over, the abutment pressure reached the maximum for 26 MPa and the stress concentration factor was 3.25, which was likely to give rise to the rock burst. With the advance of the working face, the abutment pressure was reduced slowly. As the 8707 working face advanced 15 m away the pillar left over, the transfixed shear failure region of 45° was found in the bedrocks of the upper and lower coal seams, which was readily to give rise to the shear rupture, leading to the rock burst. Based on the aforementioned research, this research carried out the PRM by applying the hydraulic fracturing technology on the coal roof and pillar, which can ensure the safety and efficient mining of working faces.  相似文献   

5.
Some villages and bridges are located on the ground surface of the working district no. 7 in the Wanglou Coal Mine. If longwall mining is adopted, the maximum deformation of the ground surface will exceed the safety value. Strip mining is employed for the working district no. 7 which is widely used to reduce surface subsidence and the consequent damage of buildings on the ground surface. To ensure the safety of coal pillars and improve the recovery coefficient, theoretical analysis and numerical simulation (FLAC 3D) were adopted to determine the coal pillar and mining widths and to discuss the coal pillar stress distribution and surface subsidence for different mining scenarios. The results revealed that the width of coal pillars should be larger than 162 m, and the optimized mining width varies from 150 to 260 m. As the coal seam is exploited, vertical stress is mainly applied on the coal pillar, inducing stress changes on its ribs. The coefficient of mining-induced stress varies from 2.02 to 2.62 for different mining scenarios. The maximum surface subsidence and horizontal movement increase as the mining width increases. However, when the mining width increases to a certain value, increasing the pillar width cannot significantly decrease the maximum subsidence. To ensure the surface subsidence less than 500 mm, the mining width should not be larger than 200 m. Considering the recovery coefficient and safety of the coal pillar, a pillar width of 165 m is suggested.  相似文献   

6.
Summary Results of instrumentation, test mining and computer aided stability analyses were combined to design the most stable gate road layout for two-seam longwall mining at the Plateau Mining Company. Five layouts were evaluated; these layouts used a combination of yield and/or large pillars with either three-entry or two-entry development systems.A layout which used a yield pillar within a two-entry development system resulted in the most stable gate roads for two-seam mining. Another layout using a yield and large pillar was shown to be most stable for single-seam mining of the top seam, but it was unsuitable for two-seam mining because of seam interaction problems.The size of the yield pillar was determined by satisfying several design requirements, as well as by limited test mining; test results showed good, medium-term stability for the yield pillars, with a possible need for rib control. It was shown that the yield pillars might be effective in controlling the floor heave, and could minimize interaction problems in two-seam mining.  相似文献   

7.
张广超  何富连 《岩土力学》2016,37(6):1721-1728
确定合理的区段煤柱宽度及巷道支护型式和参数,对于提高资源回采率和巷道安全性及实现综放开采高产高效意义重大。以王家岭煤矿20103区段运输平巷为工程背景,采用FLAC3D数值分析了不同煤柱宽度下围岩主应力差、变形及破坏演化规律,认为合理煤柱宽度为6～10 m,并结合实际地质和生产条件确定试验巷道煤柱宽度为8 m。采用理论分析和现场钻孔窥视方法综合确定基本顶断裂线位于距采空区约7 m处,认为由于综放沿空巷道围岩性质结构和应力分布沿巷道中心线呈明显非对称性,将引发煤柱侧顶板严重下沉和肩角部位煤岩体错位、嵌入、台阶下沉等非对称破坏特征,靠煤柱侧顶板及肩角部位是巷道变形破坏的关键部位。在此研究基础上,针对性地提出了以高强锚梁网、不对称锚梁、锚索桁架为主体的综合控制技术,详细阐明了具体支护措施的控制机制,并进行现场应用。工程实践表明,8 m煤柱宽度合理,该支护技术能够保证窄煤柱沿空巷道围岩稳定,并已在王家岭煤矿大面积推广应用,对类似工程条件的支护技术具有一定的理论意义和实用价值。  相似文献   

8.
Most coal mines in China use the longwall mining system. High stresses are frequently encountered around development entries at deep mines. This paper presents an alternate longwall mining layout for thick coal seams to minimize ground control problems. In a conventional longwall panel layout, development entries on both ends of the panel are located along the floor, and a coal pillar (chain pillar) is left between adjacent panels to ensure stability. Gateroads on either end of a longwall panel using the layout proposed in this paper are located at different vertical levels within a thick coal seam or in a geologically split coal seam for improved stability. The headgate entry/ies are driven along the floor while the tailgate entry/ies are driven along the roof. Therefore, a longwall face has a gradually elevated or curved section on one end of the panel. For the adjacent panel, the development entry may be located directly below the development entry of the previous panel or may be offset horizontally with respect to it. Based on physical and numerical modeling approaches, it is demonstrated that the stress environment for development entries employing the longwall layout is significantly improved; ground control problems are therefore minimized.  相似文献   

9.
In this paper, based on the field test of No.S3012 working face of Shan Mushu Coal Mine in Sichuan Coal Group, monitoring the abutment pressure and gas drainage flow during the mining process, studying the change law of the abutment pressure and gas drainage flow of the coal seam, and using the numerical simulation method research on the evolution of abutment pressure and displacement of coal seam during the mining process. The results shown that: with the advance of coal mining face, the abutment pressure of coal seam can be divided into stress decreasing area, stress increasing area and original stress area, and the stress state of coal seam and the pore, crack structure and permeability of coal body are obviously changed. With the advance of the mining face, the abutment pressure in front and back of the coal mining face is the moving abutment pressure, and the coal mining face to be in the pressure relief area, the front abutment pressure peak value deep into the coal body 5–10 m, the influence scope reaches the front coal mining face to 90–100 m, this area is the stress increasing area. And the evolution law of the roof displacement of goaf is similar to the elliptical with the axial ratio changes, when the ratio is close to 1, the roof subsidence affected area is similar to the shape of “O”.  相似文献   

10.
侧向支承压力分布、资源回收率以及煤柱和巷道的稳定性是大采高综放面区段煤柱宽度留设要兼顾的因素,为了确定大采高综放面区段煤柱宽度,以某矿8103面为工程背景,首先,采用理论计算和现场应力监测等方法确定大采高综放工作面倾向支承压力分布规律,得出应力降低区宽度约为8 m,原岩应力区为巷帮侧28 m外。其次,采用工程类比方法确定大采高综放工作面巷帮外侧煤体严重破裂区宽度约为4 m。最后,采用FLAC3D数值软件分析了下区段工作面回采时窄煤柱（6、8 m）和宽煤柱（28、30 m）的应力场、位移场及塑性区特征,获得不同煤柱宽度时巷道和煤柱力学特征。研究表明：当煤柱宽度6 m和8 m时,在采动支承压力下煤柱几乎无承载能力,且巷道变形量较大;当煤柱宽度28 m和30 m时,在采动支承压力下煤柱中央仍有一定的弹性核,煤柱保持稳定且巷道变形量较小。综合考虑资源回收、巷道稳定性、次生灾害控制等因素,确定大采高综放工作面区段煤柱宽度为28 m。  相似文献   

11.
Low recovery of longwall top coal caving (LTCC) remains one of the most difficult engineering problems in this mining method and impedes its application. The top coal left in the gob at face end accounts for a large portion of the total coal loss, and the instability of the leftover triangle coal at face end has long been a threat to the safety of miners and the mining equipment. In this paper, based on the engineering background of Ruilong mine, we explore the stability of the roof at the end of the face by using theoretical analysis, numerical simulation, and field measurement. Results reveal that in the inclined longwall top coal caving face, the immediate roof forms an “arch” structure, and the basic roof forms a “masonry beam” structure after the roof collapses; working resistance of the support calculated by the method of ultimate bearing capacity was adequate to meet the requirement of roof load; roof load of coal pillar was related to the length of key block and fracture position; and increasing the size of coal pillar could ensure the stability of both coal pillar and roof.  相似文献   

12.
Measurement of Longwall Mining Induced Strata Permeability   总被引：1，自引：0，他引：1  
The paper summarizes the findings of the underground permeability measurements (using inflatable packers) undertaken at a mine site in New South Wales in Australia and highlights the difficulties encountered during packer testing. The research project was supported by the Australian Coal Association Research Project. Within this project, systematic sub-surface and underground hydrogeological monitoring and measurements were carried out e.g. underground packer tests and piezometer, extensometer, and water inflow monitoring during mining. The project was aimed at investigating the effects of longwall mining on strata pore pressure, permeability, and water inflow to facilitate prediction of mining induced aquifer interference and mine water inflow. This paper presents only the results of underground permeability tests conducted at the mine site. The tests show that the drivage of main headings (roadways) can induce a significant change in permeability into the solid coal barrier. Permeability can be seen to increase by as much as 50 times at a distance of 11.2–11.5 m from the roadway rib. The measured permeability values varied widely and strangely on a number of occasions; for example the test conducted from the main headings at 8.2–8.5 m test section in the solid coal barrier showed a decline in permeability value compared to that at 11.2–11.5 m section contrary to the expectations. The tests conducted in the roof strata near (above) the longwall goaf indicated a possibility of more than 1,000 fold increase in permeability. Though the underground packer testing appears to be a good technique for measuring in situ permeability of rocks and coal seams, the study highlighted that (1) boreholes for packer testing need to be drilled with extreme care so as to avoid any undue damage or smearing of the borehole wall and (2) a sufficient number of tests at a number of locations needs to be conducted to cater for the possible variations of the test results.  相似文献   

13.
Surface subsidence can cause many environmental problems and hazards (including loss of land area and damage to buildings), and such hazards are particularly serious in coal mining districts. Injecting grout into the bed separation in the overburden has been proposed as an effective control measure against surface subsidence during longwall mining. However, no field trials of this technique have been implemented in mines under villages in China, and thus, its ability to control subsidence in such areas has yet to be demonstrated. In this study, field trials using this technique were carried out during longwall mining under villages in the Liudian coal mine, China. The maximum surface subsidence observed after the extraction was only 0.298 m, which accounts for 10 % of the mining height and is 79 % less than the predicted subsidence. Moreover, no damage occurred to the village buildings either during or after extraction and these buildings remain stable. Thus, this study represents the first successful attempt to control surface subsidence under villages in China using grout injection during longwall mining.  相似文献   

14.
To master the laws of strong strata behavior of Tashan coal mine under Carboniferous coal mining process, the laws of strong strata behavior in 8107 working face was measured and analyzed. It was shown that the average initial weighting step of 8107 working face was 59.4 m. The average periodic weighting step of main roof was 16.2 m. The maximum working resistance during periodic weighting was 14,711.1 kN. The maximum working resistance during non-periodic weighting was 11,339.9 kN. The average dynamic load factor K during periodic weighting was 1.31. The stress of coal column on the side of the goaf could be divided into four zones (stress stabilization zone, stress slow-increasing zone, significant—increasing stress zone, stress reduction zone) along the strike of 8107 working face. There was a peak of lateral support pressure along the trend of 8107 working face. And the peak position was biased to the side of return airway roadway. With the increase of the distance from the down-side of return airway, the pressure peak of the inner coal body along the strike of 8107 the working face increased and the peak position decreased from the coal wall. The peak stress of coal column tended to be close to the up-side of return airway. And the distance from the down-side of return airway for the peak of inner coal was larger than that for the peak of coal pillar. The peak position of abutment pressure of hard roof was in the range of 10–25 m in front of 8107 working face under full mechanized mining extra thickness coal seam conditions. The relative stress concentration coefficient of k was 1.3–6.5. The range of 10–25 m from the front of the working face to coal wall was stress reduction zone. And the influence range of abutment pressure was about 80 m. It was of great significance to the control and practice of the surrounding rock of the stope for the mining of the hard extra-thick coal seam.  相似文献   

15.
In this work, a shortwall block backfill mining (SBBM) technique is proposed for the recovery of residual corner coal pillars and irregular blocks left behind during the exploitation of coal mines, and a solution is provided for the risks associated with gangue piling and the loss of water resources owing to coal mining. Based on the theory of beams on elastic foundations, a mechanical analysis model was established for calculating the height of a water-conducting fracture zone (WCFZ) in the overlying strata of coal mines exploited using the SBBM technique. It was found that the key factors influencing the development of the WCFZ are the mining height, width of the protective coal pillars, backfill percentage, block length, and number of mining blocks. The relationships between these factors and the height of the WCFZ were obtained by incorporating the relevant parameters in the above-mentioned model. In the field experiment site, it was discovered that the minimum coal pillar width and goaf backfill percentage required to prevent the development of water-conducting fractures that could reach an aquifer are 5 m and 65%, respectively. Based on this result, the protective pillars of the site were designed to be 5 m wide, while the goaf backfill percentage was set as 80%. The borehole fluid method was used to measure the height of the WCFZ, which was found to be 26.8 m. This is consistent with the theoretical calculations (27.0 m) of this study, and thus, validates the reliability of the proposed mechanical model. The findings of this work will improve the recovery rate of residual coal resources in coal mining areas, and they are significant for the refinement of water conservation mining theories.  相似文献   

16.

Equipment recovery passage (ERP) is being widely employed in longwall panel for the purpose of recovering heave mining equipment at the end of mining stage. The stability of the ERP, however, is always difficult to control although powerful supporting structures are employed, which restricts its further promotion. In the present paper, we focused on the ERP’s stability control through reducing the abutment stress imposed on the ERP’s surroundings rather than solely increasing roadway support intensity, based on a rigorous case study in China. First, the dynamic evolution of the abutment stresses, corresponding plastic zone and deformations in the surrounding rock of the ERP were analyzed through a meticulously validated FLAC3D numerical simulation, as the longwall face moved with different velocity. The simulated results indicate that the faster the longwall face moved, the lower the abutment stresses, the narrower the plastic zone and the smaller the deformations were. In terms of these analyses, two suggestions were proposed, including increasing longwall face moving velocity and roof structure optimization, and corresponding technologies were introduced, and potential effect were verified as well. Conclusions and suggestions of this paper might be helpful for increasing the flexibility of the ERP in similar geotechnical conditions.

  相似文献   

17.
闫书缘  杨科  廖斌琛  涂辉 《岩土力学》2013,34(9):2551-2556
为研究深部近距离煤层群下向卸压开采高应力演化的特征,根据潘二煤矿深部近距离煤层群8煤和6煤地质与开采技术条件,设计了下向卸压开采的二维相似材料模拟试验模型,对8煤和6煤开采引起的采动应力进行监测。系统分析了8煤下向开采与6煤开采后的采场围岩采动应力、岩层运移及不规则煤柱对采动应力演化的影响,获得了近距离煤层群8煤下向卸压开采的顶底板采动高应力演化特征及6煤回采期间覆岩运移、采动应力裂隙演化和来压特征,得出了下向卸压开采不规则煤柱对采动应力、裂隙分布的影响规律。研究不仅为以采动高应力演化为主导作用的煤岩动力灾害防治提供了理论基础,也为卸压开采采场参数设计与优化提供了技术支撑。  相似文献   

18.
镇城底矿工作面的回采巷道一条沿顶板掘进,一条沿底板掘进,相邻两工作面在端头搭接,沿底板掘进的巷道形成巷顶沿空掘巷。通过理论分析、相似模拟、数值模拟及现场实测对巷顶沿空掘巷围岩结构及应力环境进行了研究。得到如下结论：该巷道不受超前和固定支承压力影响,大结构下方的矸石垫层可起到能量和应力耗散的作用,避免了动载和冲击影响,应力低且稳定;岩层移动形成的垮落角对采空区应力大小和分布（尤其采空区边缘）有重要影响;垮落角越小,采空区应力越小,该巷道围岩应力越小,采空区恢复至原岩应力的距离越大;垮落角对岩体塑性区发育方向起控制和导向作用;该巷道围岩应力大幅低于原岩应力,卸压程度大;实测该巷道竖向和横向位移均比非沿空巷道小,即顶底板和两帮应力环境均得到改善。研究对维护具有冲击倾向的高应力巷道具有一定意义。  相似文献   

19.
In this paper a geometric computational model (GCM) has been developed for calculating the effect of longwall face on the extension of excavation-damaged zone (EDZ) above the gate roadways (main and tail gates), considering the advance longwall mining method. In this model, the stability of gate roadways are investigated based on loading effects due to EDZ and caving zone (CZ) above the longwall face, which can extend the EDZ size. The structure of GCM depends on four important factors: (1) geomechanical properties of hanging wall, (2) dip and thickness of coal seam, (3) CZ characteristics, and (4) pillar width. The investigations demonstrated that the extension of EDZ is a function of pillar width. Considering the effect of pillar width, new mathematical relationships were presented to calculate the face influence coefficient and characteristics of extended EDZ. Furthermore, taking GCM into account, a computational algorithm for stability analysis of gate roadways was suggested. Validation was carried out through instrumentation and monitoring results of a longwall face at Parvade-2 coal mine in Tabas, Iran, demonstrating good agreement between the new model and measured results. Finally, a sensitivity analysis was carried out on the effect of pillar width, bearing capacity of support system and coal seam dip.  相似文献   

20.
In order to find the relationship between the shaft lining stability and the coal extraction operation, a 3D numerical model of strata layers and shaft lining was established for simulating the influence of coal extraction operation on shaft lining. Certain factors including mining depth, safety pillar width, mining width and mining height were taken as the influence factors in the simulation. The results indicated that the coal extraction could lead to the initiation of the failure in the aquifer and rock layers. As the mining depth increases, the shear strain increment in aquifer becomes small. In this case, the distance between mining panel and aquifer should be larger than 220 m and the safety pillar width should not <70 m. The maximum principal stress in aquifer had a little relation to mining operations. The mining panel width should not exceed 50 m without any support.  相似文献   

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