外文翻译综放沿空掘巷卸压技术研究

英文原文Study on destressing technology for a roadway driven along goaf in a fully mechanized top-coal caving face Abstract Based on the deformation characteristics of the roadways driven along goaf in fully mechanized top-coal caving faces,the author considers that it is the key to ensure the stability of surrounding rocks of roadway driven along goaf to control the deformation during the period affected by mining.Considering the characteristics of the roadway layout in fully mechanized top-coal caving faces,a technical scheme of destressing is put forward and the destressing effect is analyzed by using the software of Universal Distinct Element Code 3.0 (UDEC- 3.0).Keywords fully mechanized top-coal caving,gob-side entry driving,roadway layout1Deformation characteristics of the gob-side entry in a fully mechanized top-coal caving face In the light of key stratum theory and the law of overlying strata movement , we know that along the dip direction the main roof broke in coal wall of the lower district sublevel and formed a rock beam structure called big structure of surrounding rocks after the upper district sublevel is extracted forward. At the same time , the peak of side abutment pressure is transferred to the depth away from the periphery along the dip direction and the coal body under the big structure lies in stress-relaxed area where the gob-side entry is laid out , as shown in Fig.1. The stability analysis of the big structure of surrounding rocks and field surveys all show that the deformation law of the roadway driven along goaf in fully mechanized top-coal caving faces obviously differs from other kinds of entries. The main characteristics are listed as follows1,2.Fig.1 The structure relationship between gob-side entry and overlying strata in a fully mechanized top-coal caving face(1)During the period of roadway excavation, the deformation law of the gob-side entry in a fully mechanized top-coal caving face is similar to that of general soft rock roadway.The roadway excavation plays a little effect on the stability of the big structure.The gob-side entry occurscertain value of deformation because the stress around the roadway changes and comes out stress concentration by roadway excavation.(2)During the period after roadway excavation and before mining effect , the big structure of surrounding rocks is stable and the deformation around the roadway is small.(3)When the gob-side entry is affected by the mining of the current fully mechanized top-coal caving face , the main roof broke again and the original equilibrium of overlying strata is badly destroyed. The rock block A and B are in the state of movement and instability. Especially , serious deformation of the surrounding rocks happens in the gob-side entry due to the rotation and subsidence of the key block B and the quantity of deformation during the period affected by mining is 5-6 times as large as that in the period of roadway excavation.2.Destressing mechanism for a gob-side entry in a fully mechanized top-coal caving faceArranging destressing entry in surrounding rocks of a roadway is an effective technical method to forwardly reduce the stress around the roadway and prevent the roadway from occurring severe deformation and damage3 . In China , arranging a destressing entry above a roadway has mostly been adopted to protect some important chambers which serve the mine for a long period. The service period of an entry is relatively shorter and a great deal of capital should be input for the additional excavation of one or two destressing entries which also affects the normal production , so a technical scheme is put forward through reforming the roadway layout in a fully mechanized top-coal caving face to achieve the purpose of destressing. In a fully mechanized top-coal caving face , one or two entries for gas drainage are driven along the roof in the middle part of the mining face (sometimes near the end of the face) . Based on the conditions of thick coal seams in fully mechanized top-coal caving faces , the destressing scheme is put forward as follows. One of the gas drains is laid out.above the gob-side entry (here this gas drain can also be called as destressing entry).Therefore , this entry can both achieve the purpose of gas drainage and destressing. The side abutment pressure induced by the upper face is transferred to the deeper coal body along the dip direction and the stress status of the gob-side entrys surrounding rocks is well improvedStanding shot in coal body of both sides of the destressing entry is adopted ahead of the current mining face to create a destressing zone in enough width above the gob-side entry. This destressing zone can act as a cushion to absorb and lessen the action of high stress induced by the rotation and subsidence of the key block B , so the extent of stress transfer to the gob-side entry decreases and the destressing effect has been achieved for the second time. As a result , the large deformation of the rocks around the gob-side entry during the period affected by fully mechanized top-coal caving face mining is markedly reduced and the purpose to effectively control the deformation of the gob-side entry in a fully mechanized top-coal caving face is accomplished.3.Numerical analysis of the destressing effect4Based on the field test conditions of the destressing technology , the software of UDEC 3.0 is used to analyze the main factors which affect the destressing effect . The test conditions of Xinji Coal Mine are as follows. The average thickness and dip angle of the coal seam are respectively 7.5 m and 12and the Protodyakonov coefficient of the coal seam is 0.7. The immediate roof and floor of the coal seam are both sandy mudstone in lower strength and the thickness of the immediate roof is 2.0 m. The thickness of quartz sandstone main roof is 8.0 m. The buried depth of the tailentry is 371453 m and a narrow coal pillar which is 23 m wide is reserved between the tailentry and the neighboring gob area.Trapezium-shaped supports are used to support the tailentry and the crossbars , legs , set spacing of the supports are 3.2 , 2.8 , 0.5 m respectively.3.1 Influence of destressing entry location on the destressing effectBecause the gob-side tailentry and destressing entry are respectively laid out along the roof and floor of the coal seam, the change of vertical interval between two entries is not considered here. The gob-side tailentry and distressing entry are laid out as shown in Fig.2 to ensure the integrality of the coal roof of the gob-side tailentry and avoid the trans fixion between the destressing zone and the neighboring gob area.Fig.2 Sectional view of roadway layout of the test site1 Headentry; 2 Gob - side tailentry ; 3 Destressing entry ;4 Gas drain ; 5 Standing shot zoneSuppose l represents the horizontal distance between the destressing entry and gob-side tailentry. With a rise of l ,the deformation amount of the gob-side tailentry will increase , and the destressing effect decreases. The deformations of the tailentry at different values of l are shown in Fig.3.Actually , with the shift of the destressing entry into deeper coal body along the coal seam dip , a stable coal pillar above the gob-side tailentry comes to appear and the pillar width will continuously rise , which makes the influence of abutment pressure on the surrounding rocks of the gob-side tailentry obviously intensified and results in its remarkable increase of stress and deformation3.2Influence of the width and intensity of standing shot on the destressing effectThe width values of the standing shot zone in each coal side of the destressing entry are 3,5 and 7m respectively ,are numerically simulated. The calculation results indicate that with the width increase of the standing shot zone, the roof stress and convergence of the gob-side tailentry obviously decrease. The impact of the variation of the standing shot width on stress and deformation of the narrow coal pillar is relatively larger while relatively smaller in the solid coal side. When the standing shot width of each coal side rises from 3 m to 5 m , the deformation amount of the narrow coal pillar decreases by 30.0 %. However , when the standing shot width rises from 5 m to 7 m , the deformation of the narrow coal pillar increases. The results show that if the standing shot width is beyond a certain limit , the top-coal body above the gob-sidetailentry will almost completely lose its supporting capacity to the key block B,so the key block B may furiously rotateand become unstable due to the mining effect,and the deformation and failure situation of the narrow coal pillar is quickly deteriorated. Consequently , the standing shot width should be limited within a reasonable extent so that the deformationof the narrow coal pillar between the gob-side tailentry and neighboring can be effectively controlled.Fig.3 Relationship between l and deformation of the gob-side tailentry1 Convergence between two ribs ; 2 Roof-to-floor convergence near the goaf ;3 Roof-to-floor convergence near the solid coalThe intensity of the standing shot also markedly affects the destressing effect . As shown in Fig4 , in the standing shot zones of both destressing entry sides , the better the standing shot effect , the more discrete and weaker the coal body.Good standing shot can further reduce the stress transference from the overlying strata down to the surrounding coal of theGob-side tailentry and its soft floor strata , and improve the destressing effect of the gob-side tailentrys surrounding strata.Fig.4 Displacement vectors of the gob-side tailentrys surrounding rocks in different intensity of standing shot(a) Strong standing shot intensity; (b) Weak standing shot intensity3.3 Influence of the operation procedure on the destressing effectThere may be three types of available operation sequences as follows. First , the gob-side tailentry is driven at thebeginning of the sequence , then the destressing entry is excavated , and the standing shot is carried out in the end ; Second , the sequence starts with the destressing entry excavation , then the gob-side tailentry is driven , and the standing shot is finally done with the advancing of the mining abutment pressure of the coal face ; Third , the destressing entry is excavated in the outset , then the standing shot is implemented , and the gob-side tailentry is lastly driven. The numerical simulation results indicate that the destressing effect of the first type of the sequences is the worst , the second one is thebest , and the third one is better. The second one begins with the destresssing entry excavation , and then the stress around the gob-side tailentry drops sharply. Under such circumstances , the gob-side tailentry is driven after the destressing entry , and the initial deformation and failure of the gob-side tailentrys surrounding rocks are limited. Eventually ,the standing shot engineering is implemented according to the behaviour of the front abutment pressure of the coal face.Therefore , this operation sequence can lower the combined abutment pressure formed by both the front abutment pressureof the coal face along the seam strike and the side abutment pressure due to the upper neighboring goaf in the opposite direction of the seam dip and its rough deformation and failure effect on the gob-side tailentrys surrounding rocks , an deffectively improve the destressing effect . In actual production , the destressing entry has been driven before the excavation of the headentry and gob-side tailentry , thus the destressing entry can serve as a water entry for the neighboring goaf or an auxiliary haulage entry of the coal face. This accords with the second and the third operation sequences whose destressing effect is relatively better.4.Effect of the applied schemeOn the basis of the practical factors which include the geological conditions of the fully mechanized top-coal caving mining face No.1309 in Xinji Coal Mine , preventing the roof caving in the course of tailentry excavation , eliminating thewater intrusion from the upper neighboring goaf and spontaneous combustion of goaf coal , etc. and the results of numerical simulation , the reasonable practical scheme is determined and tested.After the destressing scheme is applied , the extent of deformation and damage of the gob-side tailentrys surrounding rocks obviously decreased. The deformation curves of the gob-side tailentry before and after destressing technology are shown in Fig15. Within the range of 50 m ahead of the coal face , the roof-to-floor convergence of the gob-side tailentry decreased from 1 300 mm to 386 mmand the convergence between two ribs decreased from 997 mm to515 mm,70.3 % and 48.3 % are respectively cut down.In non-destressed gob-side tailentry , the deformation and damage of the surrounding rocks were still very large and terribly severe even after 35 times of rebuilding work. The section of the gob-side tailentry near the coal face was generally less than 4 m2 and somewhere even less than 0.52.0 m2 . The maintenance status of the gob-side tailentry was improved greatly by using destressing technology. Because the wooden supports were used and the self-stability capability of the coal body was lower , a certain extent of underground pressure behavior appeared in the testing gob-side tailentry. The maintenance status of the gob-side tailentry was invariably in a good condition and the section near the coal face was more than 6 m2 after some partial repairing work.Fig.5 Deformation curves of the gob-side tailentry before and after destressing technology1 Roof-to-floor convergence before destressing ;2 Convergence between two ribs before destressing ;3 Convergence between two ribs after destressing ;4 Roof-to-floor convergence after destressing5.Conclusions(1)To control the deformation of the gob-side entrys surrounding rocks during the period affected by mining is the key to ensure the stability of the gob-side entry and safe production of the coal mine. That the gas drain also serves as a destressing entry for the gob-side entry through reforming the roadway layout in a fully mechanized top-coal caving face can achieve remarkable destressing effect(2)The destressing zone created by the destressing entry and standing shot can observably reduce the transfer of high stress induced by the rotation and subsidence of the key block B to the surrounding rocks of gob-side tailentry and the purpose to reduce the deformation of the gob-side tailentrys surrounding rocks was achieved.(3)The longer the distance l is , the lower the destressing effect of the gob-side tailentry is. The standing shot width in both coal sides of the destressing entry should be limited within a reasonable range. The higher the standing shot intensity is , the better the destressing effect is. The ideal operation procedure of destressing maintenance is as follows.Firstly , a destressing entry is excavated ; secondly , the gob-side tailentry is excavated ; lastly , standing shot is carried out according to the advancing of the mining abutment pressure in the fully mechanized top-coal caving face。(4)Successful application of the destressing technology provides a new thinking to maintain the gob-side entry and lay out the roadways in a fully mechanized top-coal caving face.References1 侯朝炯, 李学华. 综放沿空掘巷围岩大、小结构的稳定性原理J.煤炭学报, 2001 , 26 (1) : 17.Hou Chaojiong , Li Xuehua. Stability principle of big and small structures of rock surrounding roadway driven along goaf in fully mechanized top coal caving face J .Journal of China Coal Society , 2001 , 26 (1) : 17.2 李学华. 综放沿空掘巷围岩大小结构稳定性的研究D . 徐州: 中国矿业大学, 2000.Li Xuehua. Study on the stability of big and small structures of rock surrounding roadway driven along goaf in fully mechanized top coal caving face D . Xuzhou : China University of Mining and Technology , 2000.3 陈炎光, 陆士良. 中国煤矿巷道围岩控制M.徐州:中国矿业大学出版社, 1994.Chen Yanguang , Lu Shiliang. Strata control around coal mine roadways in China M . Xuzhou : Press of China University of Miningand Technology , 1994.4 He Fulian,Qu Qundi,Zou Xizheng,etal. Numerical simulation of destressing maintenance for a tailentry along gob area A . 29th International Symposium on Computer Applications in the Minerals Industries C.20011673676.中文译文综放沿空掘巷卸压技术研究 摘要： 针对综放工作面沿空掘巷巷道的变形特征，作者认为确保沿空掘巷围岩稳定的关键是控制采动影响期间巷道的变形。考虑到综放面巷道布置的特点，提出了卸压技术方案，并且运用离散元3.0 程序（UDEC- 3.0）分析卸压效果。关键字：综采放顶煤，沿空掘巷，巷道布置1 综放沿空巷道变形特征根据关键层理论和上覆岩层运动规律可知，当上区段工作面推过后，沿其倾斜方向，老顶破断在下区段煤柱内，随着工作面的不断往前推进，形成一种稳定的结构，这个结构被称为大结构。与此同时，沿倾斜方向的支承压力峰值向下区段煤体深处转移，沿空巷道应布置在大结构下方的应力降低区域，如图1所示。围岩大结构的稳定性分析与现场调查都表明了综放沿空掘巷与其他类的巷道相比有明显的区别。它的主要特征如下所示（1）巷道开掘期间，综放沿空巷道与大多数的软岩巷道是相似的。巷道开挖对大结构的稳定性影响是非常小的。由于受开掘影响，巷道周围应力改变并且产生了应力集中，沿空巷道出现了一定的变形值。（2）巷道开掘之后和回采影响之前，围岩大结构是稳定的，巷道变形很小。（3）当沿空巷道受到综放工作面的采动影响时，老顶再次发生破坏，原上覆岩层的稳定受到破坏。岩块A与岩块B处于运动的不稳定状态。尤其是采动期间沿空巷道产生严重变形，变形量是巷道开掘期间的5-6 倍，这是由于关键块B的旋转下沉造成的。图1 综放沿空掘巷与上覆岩层的结构关系Fig.1 The structure relationship between gob-side entry and overlying strata in a fully mechanized top-coal caving face2 综放沿空巷道的卸压机理卸压巷道布置在巷道周围岩石中对于减小巷道周围的应力和防止其发生严重的变形和破坏的一种十分有效的技术方案。国内，在巷道之上布置卸压巷道常被大部分煤矿采用以保护一些服务年限较长的重要硐室。巷道服务年限相对较短并且开掘一两条额外的卸压巷道需要投入大量的资金，同时也影响正常的生产，因此，提出了改革综放巷道的布置的技术方案来达到卸压的目的。在综放工作面内，用于瓦斯抽放的一条或两条巷道沿采煤工作面的顶板中部（有时靠近工作面的端部）掘进。针对综放工作面厚煤层的条件，提出了如下的卸压方案：其中的一条瓦斯尾巷（也被称为卸压巷道）布置在沿空巷道的上部。因此，这条巷道同时达到了瓦斯抽放与卸压的目的。由上区段工作面产生的侧支承压力转移到沿倾斜方向的煤体深部，沿空留巷的围岩应力状态得到了很好的改善。采用超前本工作面在卸压巷道两帮的煤体内松动爆破，目的是在沿空留巷的上部产生足够宽的卸压区域。卸压区域能作为缓冲垫层以吸收和减少由关键块B旋转下沉所产生的高压力，因而转移到沿空巷道的应力值降低，再次达到了卸压的效果。最终，在综放采动影响期间的沿空巷道围岩的大变形得到显著的降低，有效控制了综放沿空留巷围岩的变形。3 卸压效果的数值分析针对卸压技术的现场测试条件，运用UDEC3.0程序分析影响卸压效果的主要因素。新集煤矿的条件如下，煤层厚度7.5 m，倾角12，普氏系数为0.7。煤层直接顶为强度较低的泥质砂岩，厚度为2.