高瓦斯矿井采空区自燃“三带”分布及防治研究

为了防治魏家地煤矿开采采空区漏风导致的遗煤易自燃现象,以魏家地煤矿西2019工作面为研究背景,采用数值模拟与理论分析相结合的研究手段提出了一项有效的采空区煤自燃防治技术,有针对性地在该工作面上隅角设置留空巷、下隅角设置封堵墙,并且通过COMSOL Multiphysics数值模拟软件模拟和对比上隅角留空巷、下隅角设置封堵墙影响下采空区自燃“三带”的分布范围和原始采空区自燃“三带”的分布范围。结果表明:在采空区上隅角设置留空巷、下隅角设置封堵墙可以减小采空区自燃“三带”的影响范围,能够有效地预防采空区煤自燃。

Ground response and failure mechanism of gob-side entry by roof cutting with hard main roof

This study is the result of long-term efforts of the authors’team to assess ground response of gob-side entry by roof cutting(GSERC)with hard main roof,aiming at scientific control for GSERC deformation.A comprehensive field measurement program was conducted to determine entry deformation,roof fracture zone,and anchor bolt(cable)loading.The results indicate that GSERC deformation presents asymmetric characteristics.The maximum convergence near roof cutting side is 458 mm during the primary use process and 1120 mm during the secondary reuse process.The entry deformation is closely associated with the primary development stage,primary use stage,and secondary reuse stage.The key block movement of roof cutting structure,a complex stress environment,and a mismatch in the supporting design scheme are the failure mechanism of GSERC.A controlling ideology for mining states,including regional and stage divisions,was proposed.Both dynamic and permanent support schemes have been implemented in the field.Engineering practice results indicate that the new support scheme can efficiently ensure long-term entry safety and could be a reliable approach for other engineering practices.

Superposed disturbance mechanism of sequential overlying strata collapse for gob-side entry retaining and corresponding control strategies

Gob-area roof rupture movement is a key disturbance factor for gob-side entry retaining.The characteristics of gob-area sequential roof collapse of overlying strata and superposed disturbance mechanism for gob-side entry retaining are obtained via physical simulation and theoretical analysis,in which the scope of disturbed strata is enlarged from main roof to fracture zone.The experiment reveals that as a working face advances,roof strata sequentially collapse from bottom to top and produce multiple disturbances to gob-side entry retaining.Key strata among the overlying strata control each collapse.Main roof subsidence is divided into three stages:flexure subsidence prior to rupture,rotational subsidence during rupture and compressive subsidence after rupture.The amounts of deformation evident in each of the three stages are 15%,55%and 30%,respectively.After the master stratum collapses,main roof subsidence approaches its maximum value.The final span of the key stratum determines the moment and cycling of gob-side entry retaining disturbances.Main roof subsidence influences the load on the filling wall.The sequential roof collapse of overlying strata results in fluctuations in the gob-side entry retaining deformation.Calculation formulae for the final span of the key stratum and the filling wall load are obtained via theoretical analysis.A control method for the stability of the gob-side entry retaining’s surrounding rock is proposed,which includes 3 measures:a“dual-layer”proactive anchorage support,roadside filling with dynamic strength matching and auxiliary support during disturbance.Finally,the gob-side entry retaining of the Xiaoqing mine E1403 working face is presented as an engineering case capable of verifying the validity of the research conclusions.

Research and application of mechanical models for the whole process of 110 mining method roof structural movement

For the 110 mining method,it is challenging to accurately calculate the support resistance of the roadway due to the lack of understanding of the dynamic movement of the overlying strata in this method.The consequential excessive support results in a significant increase in the cost of roadway support.The authors explored the overlying strata movement and roadway deformation of the gob-entry retaining in the 110 mining method to solve this problem.First,the typical stages of the roof-cutting gob-side entry were defined.Second,the mechanical model and calculation formula of the support resistance on the roof were explored.Then,using numerical simulation software,the starting ranges of the specific supports at different stages were verified and the feasibility of the support scheme was examined.Finally,combined with the field measurement data,the stress and the deformation of the gob roadway at different stages under the influence of two mining processes in the 110 mining method were obtained.The numerical simulation results obtained are consistent with the field test results,providing a theoretical basis for precision support at different stages by the 110 mining method.

Position-optimization on retained entry and backfilling wall in gob-side entry retaining techniques

This study investigates the stability problem of gob-side entry retaining （GER） and backfilling wall which located under the key block B. Based on the combined research of elastic-plastic mechanics, structure mechanics and modern theory of mining-induced pressure, the caving characteristic and roof structure over the GER were analyzed, and the vertical force and the torque on retained entry roof were also derived as the position for the retained entry varies. On the basis of the specific geology in Huainan mining area, the results indicate that a relatively more stable position for retained entry neighbors the hinge point of block A and B, and it also located at a scope ranging from this point to the one-third length of block B in horizontal direction. As to appropriate position for backfilling wall, this study recommends partial- road-in backfilling method for GER. Field trial conducted at panel face 12418 of Xieqiao Mine demonstrates that the recommended width for original entry is 3.6 m and the preferred width proportion between original retained entry and original entry is 75 % or so whereas the avoidable one is 88 % or so. These findings provide qualitative references to the mines which share similar geology as what Huainan mining area characterized.

Study of dynamic pressure roadway supporting scheme under condi- tion of thick composite roof

This paper analyzed the strata behaviors of solid-coal roadway, gob-side entry driving and deformation law of surrounding rock in depth under high stress and thick composite roof based on the dynamic pressure roadway as engineering background in Fengcheng mining area, Jiangxi province. The results, both field measurement and numerical simulation show that gob-side entry driving results the deformation of coal roadway main wall, however, entity-coal roadway driving results deformation of main roof and floor. The maintenance state of gob-side entry driving is better than entity-coal roadway, this situation is relevant to thick composite roof layered and easy collapse characteristics. At the same time, this paper put fox＇ward and proved proper dynamic pressure roadway supporting scheme under the surrounding rock condition and stress environment.

Top-coal deformation control of gob-side entry with narrow pillars and its application for fully mechanized mining face

A mechanical model to control the top-coal deformation is established in accordance with the structural characters of the gob-side entry surrounding rock for the fully-mechanic top-coal caving; the analytical solution of top coal roof-sag curve is deduced with Winkler elastic foundation beam model. By means of a calculating and analytic program, the top coal roof-sag values are calculated under the conditions of different supporting intensities, widths of narrow pillars and stiffness of top coal; meanwhile, the relationship between the roof-sag values and supporting intensity, width of narrow pillars and stiffness of top coal is analyzed as well. With the actual situation of the gob-side entry taken into consideration, the parameters of top-coal control are determined and a supporting plan is proposed for the top-coal control,which is proved to be reliable and effective by on-site verification. Some theoretical guidance and advice are put forward for the top-coal deformation control in gob-side entry for fully mechanized top-coal caving face.

Control of floor heaves with steel pile in gob-side entry retaining

A new approach named as steel pile method is innovatively proposed in this study to control severe floor heaves in gob-side entry retaining. It is required that the steel piles be installed in the floor corners with a certain interval before the influence of the dynamic pressure induced by current panel extraction. Using numerical simulation and theoretical analysis, this study investigated the interaction between the steel piles and the floor rocks during the service life of the steel piles, and revealed the mechanism of the steel piles in controlling floor heaves. The effect of the steel pile parameters on the control of floor heaves was presented and elaborated. It is found that the effectiveness of the steel piles in controlling floor heaves can be enhanced with greater installed dip angle, longer length and smaller interval of the steel piles.Compared with traditional methods, e.g., using floor anchor bolts and floor restoration, the advantages using steel pile were successfully defined in terms of controlling effect and economic benefits. It is hoped that the proposed method can contribute to the development of gob-side entry retaining technique.

NEW TECHNOLOGY OF ROADSIDE ENTRY SUPPORT IN ADVANCING-MINING BY PUMPING HIGHWATER-CONTENT FAST SETTING-SOLIDIFYING MATERIALS

Roadside entry supporting technology by pumping high water-content fast setting-solidifying materials in advancing-mining was industrially tested in Yangzhuang Coal Mine, Huaibei Coal Mining Administration. Roadside packing parameters were determined according to the properties of high water-content fast setting-solidifying materials, as well as geological and mining conditions. A new roadside packing technological system was designed to use pumping-delivery method to transport the materials. With respect to the special conditions in the advancing mining system, effective temporary support systems were designed and tried. The technical and economic benefits from this new industrial experiment were carefully analyzed and evaluated.

Analysis on distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face

The three-dimensional damage constitutive relationship of coal is established and distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face under the effect of given deformation of the main roof is analyzed by the damage mechanics theory. And the relationship between distribution of the abutment pressure and thickness of coal seam is explored. The presented result is of great theoretical significance and practical value to the study on stability control of the surrounding rock of road-in packing for gob-side entry retaining in fully-mechanized caving face.