短壁块段式采煤覆岩导水裂隙发育力学特性分析

Analysis on the mechanical properties of water-conducting fractures development during the shortwall block mining

短壁块段式采煤技术作为一种绿色开采技术,可以有效地兼顾煤炭安全高效开采和水资源保护,但在开采过程中会造成一定范围的导水裂隙带,对含水层的稳定性造成潜在的影响。因此,短壁块段式采煤覆岩导水裂隙发育力学特性的研究对科学预防、控制和治理煤炭开采所引起的水资源流失问题具有重要意义。为了计算短壁块段式采煤造成的覆岩导水裂隙带发育高度,在分析覆岩移动特征的基础上,确定影响短壁块段式采煤覆岩导水裂隙发育的主控因素。并基于弹性地基梁理论,结合短壁块段式采煤工作面布置特殊性,建立了一种计算短壁块段式采煤覆岩导水裂隙带发育高度的弹性地基叠合梁力学模型,给出岩层产生导水裂隙的判定方法,计算获得岩层破坏层数(导水裂隙带高度)随不同主控影响因素的变化规律,揭示了短壁块段式采煤覆岩导水裂隙发育的力学机理及规律。研究结果表明:随着采高和块段长度增大,岩层破坏高度呈阶梯状上升;随煤柱宽度的增加,岩层破坏高度呈降低趋势。同时,当影响因素参数在一定范围内时,岩层破坏层数不变,因此,在保证水资源不发生流失的前提下,可选择范围内最大采高、块段长度以及最小煤柱宽度作为开采指标来提高回收率。现场短壁块段式采煤实验工作面采用钻孔冲洗液漏失量观测和钻孔电视探测的方法,测试得到采动造成的覆岩导水裂隙带高度约为50.06 m,与理论计算结果(50.3 m)基本吻合。

Although shortwall block mining technology had become a kind of green mining technology who was effective in considering the production rate of coal resources and the protection of water resources,a certain range of water-conducting fractured zone would be also created by shortwall block mining,which would have potential effect on the aquifer stability.In this circumstance,it is necessary to reveal the mechanical properties of water-conducting fractures development during the shortwall block mining,which is helpful for the scientific prevention and control of the water loss problems caused by coal mining.In order to calculate the development height of water-conducting fractured zone after the shortwall block mining,based on the analysis on the movement characteristics of shortwall block mining overlying strata,the key affected factors of the development height of water-conducting fractured zone were confirmed.In addition,according to the elastic foundation beam theory,a mechanical model of elastic foundation laminated beam was established for calculating the development height of water-conducting fractured zone in shortwall block mining,and the method for assessing the generation of water-conducting fractures was given.Furthermore,the variation of the number of failure layers(height of water-conducting fractured zone)with the mining height,the width of the protection pillar and block length was obtained by the mechanical model.The results shows that the height of failure layers increases in stepped style with the increase of mining height and block length,and the height of failure layers decreases gradually with the increase of coal pillar width.Moreover,when the parameters of shortwall block mining working face varies within certain ranges,the number of failure layers are unchanged.Therefore,the maximum mining height,block length and minimum pillar width of the certain ranges could be chosen as the mining index to enhance the recovery rate under the premise that the water resources is not lost.The engineering practice of shortwall block mining experimental working face showed that the height of the water-conducting fractured zone was approximately 50.06 m,which was measured through the methods of drilling TV imaging and washing fluid loss.The measurement is basically consistent with the theoretical calculation result(50.3 m).