浅埋薄表土层薄基岩综放工作面覆岩结构及顶板控制

Overlying strata structures and roof control of working face under thin topsoil and thin bedrock in shallow seam

针对表土层厚度小于卸荷拱最低成拱高度时的浅埋工作面液压支架选型问题,以牛山煤矿为研究对象,采用离散元软件3DEC与多元非线性回归分析手段,对此条件下工作面表土层应力分布、基本顶岩块受力状态以及控顶区顶板下沉量发展规律进行研究。结果表明,基本顶岩块较小的台阶下沉即可引起表土层显著的卸荷效应,使支架-围岩结构趋于稳定,所需支护强度降低,初次来压卸荷系数仅受台阶下沉量和表土内摩擦角影响;初次来压时,基本顶A,B块受力不对称,B块对A块作用有垂直向下的分力;周期来压时,D块对C块作用有垂直向上的分力,达2.8 MPa;可根据允许顶板下沉量确定支护强度。建立了塑性铰连杆模型,给出了适用于此条件的液压支架工作阻力计算公式。

According to the selection of hydraulic support at working face in shallow seam when the thickness of soil layer is less than the lowest arching height of unloading arch,taking Niushan Coal Mine as an example,using the distinct element software 3 DEC and nonlinear multiple regression analysis,the stress distribution in topsoil,the basic roof rock stress state and the working face roof subsidence law were studied. The results show that a small bench convergence of basic rock block can lead to the significant unloading effect in soil layer,which results in the support-surrounding rock structure more stable,and the required support intensity reduced,and first weighting unloading coefficient is only affected by bench convergence and internal friction angle of soil; during initial weighting,the force of A and B block is asymmetric,B block applies a downward vertical component of force to A block; during periodic weighting,D block applies a upward vertical component of force to C block,up to 2.8 MPa; can determine support intensity according to allowed roof subsidence.In addition,the plastic hinge connecting rod model was established.A formula was given for calculating the working resistance in this case.