浅埋深孤岛工作面下行开采过上覆遗留煤柱强矿压特征及防治技术

Strong ground pressure characteristics and prevention technology when shallow buried island working face goes down through overlying residual coal pillar

神东矿区大柳塔煤矿22314孤岛工作面受采空区侧煤柱和巷道上区段回采工作面的采动影响,矿压显现强烈,底鼓严重,帮部移近量大,巷道变形量较大,严重影响工作面安全生产。为控制矿压、确保安全生产,通过矿压分析、上覆煤柱分析、数值模拟分析、地表塌陷分析、工作面底鼓分析、水预裂弱化顶板、补强支护及控制效果分析,得到工作面基本顶初采来压在35~40 MPa,来压范围30~110号架,底鼓最大移近量达1.4 m,造成26根推拉杆破断,煤壁片帮深度500~1000 mm,工作面首次周期来压位置距基本顶初次来压位置28 m,距工作面基本顶二次来压位置22 m;上覆煤柱大量存在,导致工作面部分地段出现应力集中现象;在工作面在推进100 m的情况下,超前支撑压力的变化趋势是由急剧上升到应力峰值转而下降,最后趋于稳定,且煤柱的塑性破坏范围可达6m;在采动压力、上覆集中煤柱已经倾倒但未完全垮落以及上覆岩层单轴抗压强度的作用下地表塌陷超前于工作面;基本顶临近破断前,顶板弯曲下沉形成铰接梁结构,底板相对完整,超前顶板破断后形成剪切面,对底板形成集中破坏区,出现严重底鼓现象;实施水力压裂初次放顶,采空区垮落及时,没有大面积空顶现象,支架后方充填严实;采用锚杆锚索钢带铅丝网支护、选用更大工作阻力的支架、回风巷超前区域用大阻力门式支架,可以有效控制矿压显现;最后实体煤帮最大变形量约为76 mm,巷道回采帮最大变形量约为102 mm,顶底板最大变形量约为106 mm,从巷道整体变形量来看,控制效果良好。

In order to control mine pressure and ensure safe production,through mine pressure analysis,overlying coal pillar analysis,numerical simulation analysis,face floor heave analysis,water pre-splitting weakening roof,strengthening support and control effect analysis,it is obtained that the initial mining pressure of the main roof of the working face is 35 MPa,the pressure range is 15 MPa,the maximum movement of bottom drum is 1.4 m,26 push-pull rods are broken,and the slope depth is 500 mm.The distance between the first cycle pressure distance of the working face and the first pressure step of the main roof is 28 m,and the second pressure distance between the working face and the main roof is 22 m.There are a large number of overlying coal pillars,which leads to the phenomenon of stress concentration in some parts of the working face;in the case of advancing 100 m in the working face,the changing trend of the leading support pressure is from sharp rise to peak stress to decrease,and finally tends to be stable,and within 6 m from the roadway wall,the plastic failure of the coal pillar occurred.The surface collapse is ahead of the working face under the action of mining pressure,overlying concentrated coal pillar has been dumped but not completely collapsed,and the uniaxial compressive strength of overlying strata is ahead of the working face.Before the old roof is nearly broken,the roof bends and sinks to form a hinged beam structure,the floor is relatively complete,and a shear plane is formed after the leading roof is broken,which forms a concentrated failure area on the floor,resulting in a serious floor heave phenomenon;hydraulic fracturing is carried out for the first time,the goaf collapses in time,there is no large area empty roof phenomenon,and the rear filling of the support is tight.Adopting anchor anchor cable steel belt lead wire mesh support,selecting support with greater working resistance and using large resistance portal support in the leading area of return can effectively control the mine pressure behavior,finally,the maximum deformation of solid coal slope is about 76 mm,the maximum deformation of roadway mining slope is about 102 mm,and the maximum deformation of roof and floor is about 106 mm.From the overall deformation of roadway,the control effect is good.