大断面切眼主应力差转移规律及支护技术

为解决厚煤层大断面切眼支护难题,选取某煤矿5206切眼为研究对象,采用UDEC模拟研究了切眼宽度为6¹0 m的过程中,围岩主应力差、变形、裂隙场的响应特征,结果表明:顶、底、两帮主应力差分布形态均呈浅部逐渐升高、深部降低特征;随着切眼宽增加,顶板主应力差峰值呈先恒定后降低,底板主应力差呈先降低再恒定,而两帮主应力差逐渐升高的趋势;主应力差峰值向深部转移幅度:两帮>顶板>底板。顶板和两帮深部位移曲线呈指数关系向深部递减,而底板深部变形曲线有明显拐点,呈台阶式降低,表面最大位移呈顶板>两帮>底板;围岩裂隙场分3个区:裂隙贯通区、裂隙发育区、微裂隙区,半椭圆状分布,裂隙贯通程度呈中间大于两侧、浅部大于深部。认为:高性能锚杆可以更有效地限制裂隙滑移,双桁架锚索可锚固在顶板肩角无裂隙区和深部预应力叠加区,可有效加强支护顶板,抵消部分主应力差。基于此,提出了高强、高预紧力锚带网和双桁架锚索联合控制技术,支护完成后10 d自稳,顶板累计离层3 mm,顶底板相对移近量125 mm,两帮相对移近量94 mm。

Principal stress difference transfer law and support in large-section open-off cut

In terms of surrounding rock control in large section open-off cut, open-off cut No. 5206 in a mine is selected as study case. The principal stress difference, deformation and fracture field are studied in the process of width from 6 m to 10 m with UDEC. Research results show that: the principal stress differences increase gradually in shallow part and decrease in depth. With the width increasing, the maximal principal stress difference maintains a constant level at first, then decreases gradually in the roof, and decreases at first, then remains constant in the floor, and increases gradually in the rib. The moving range of peak: rib>roof>floor. The curve of displacement in roof decrease exponentially, but has obvious inflection point, which decrease terracedly in the floor. The maximal surface displacement: roof>side walls>floor. The fracture field is divided into three areas: fracture transfixion area, fracture area and microfracture area, which are all distributed as semi-ellipse, the extent of cut through:middle part>two sides and shallow part>deep part. It is believed that high-performance bolt hold the slippage of fracture effectively. The double truss cable can be anchored in the shoulder angle area, which has no fracture, and pre-tension overlays the area. Also, the double truss cable can close the shallow part of roof and reduce principal stress difference. Based on above, a high strength and high pre-tension bolting support scheme of band net and double truss anchor are proposed. The open-off cut achieves self-stabilization after 10 days when it is dug out, the total roof separation is 3 mm, and the roof-to-floor relative convergence is 125 mm, both sides relative convergence is 94 mm.