综放工作面煤柱巷道软岩底板非对称底臌机理与控制

针对综放工作面煤柱巷道非对称底臌剧烈、支护维护困难、起底工程量大等难题,以大南湖一矿综放工作面煤柱巷道为工程背景,采用理论分析、数值模拟、现场试验等综合研究方法,分析了煤柱巷道围岩周边应力环境特征及其作用下的变形破坏形态。结果表明:煤柱巷道底板强度低下以及在采动影响下围岩应力环境出现非均匀现象,进而导致巷道底板塑性区出现非均匀分布,是造成非对称底臌的内在原因;底臌变形规律监测结果显示,非对称底臌程度与放煤厚度有内在联系,放煤厚度在5.9 m范围内,放煤厚度越大,基本顶岩层破断偏转角度亦越大,巷道围岩周边主应力比值、主应力旋转角度等参数越大,底板塑性破坏引起的非对称底臌变形越剧烈;底板最大塑性破坏深度位置随着主应力方向旋转角度的增加,逐渐向巷道中部位置移动,导致底臌变形最大位置分布不同,同时,煤柱巷道的这种底臌变形可控性较差,现有技术条件下企图采用高强支护是不可行的,控制上应以适应底臌变形为主;然而,当放煤厚度超过5. 9 m,基本顶岩层有沿煤柱边缘失稳切落的可能,巷道围岩应力环境趋于原岩应力状态,巷道围岩塑性区分布范围大幅降低,底臌变形较小。据此,以巷道非对称底臌规律为依据,提出了以调整采掘关系、优化巷道底臌硬化方案为主的底臌控制对策,现场应用效果良好,底臌变形量有效减少的同时,巷道底臌处理工作量亦大幅降低。

Mechanism and control strategy of asymmetrical floor heave of coal pillar roadway in fully mechanized caving face

To study the problems such as dramatic asymmetrical floor heave deformation of coal pillar roadway in fully mechanized caving face,difficulty in support and maintenance,theoretical analysis,numerical simulation and field test were adopted.The stress environment,deformation and failure characteristics of the coal pillar roadway in the fully mechanized caving face at Dananhu No.1 coal mine in China were analyzed.The results demonstrate that the asymmetrical phenomenon of surrounding rock stress environment caused by mining is the intrinsic reason for the asymmetrical floor heave in the coal pillar roadway.It also leads to a non uniform distribution of the plastic zone of floor in coal pillar roadway.The degree of asymmetrical floor heave has internal relations with the thickness of caving coal.When the thickness of caving coal is in the range of 5.9 m,the greater the parameters,such as the thickness of the caving coal,the breaking deflection angle of the strata of main roof,the principal stress ratio and the rotation angle of the principal stress direction in the stress environment of the roadway,the more obvious deformation of asymmetrical floor heave caused by plastic failure in floor.The maximum plastic failure depth position of the floor gradually moves toward the middle of the roadway as the rotation angle of the principal stress direction increases.It causes a different distribution of the maximum deformation position of floor heave.At the same time,the deformation of the floor heave of the coal pillar roadway is poorly controllable.It is not feasible to attempt to use high strength support under the current technical condition.The control should mainly be adapted to the floor heave deformation.When the thickness of caving coal more than 5.9 m,the strata of main roof have the possibility of instability and being cut along the edge of the coal pillar,and the surrounding rock stress environment of the roadway tends to the original rock stress state.Consequently,the distribution range of the surrounding rock plastic zone is greatly reduced in the roadway.The deformation of floor heave is small.Based on the results above,the strategy of floor heave control based on adjusting the relationship of mining and driving,and optimizing the roadway floor heave treatment plan was proposed and good results were obtained.With the decrease of deformation of the floor heave,the working volume of floor heave was also greatly reduced.