重复冲击特厚煤层巷道围岩裂隙演化及破坏特征

Fracture evolution and failure characteristics of roadway surrounding rock in extra-thick coal seams subjected to multiple coal bursts

针对特厚煤层巷道围岩在重复冲击动载作用下发生大变形甚至垮冒堵巷的控制难题,基于深部巷道围岩破坏机理与岩石冲击动力学理论,研究了多次冲击扰动下特厚煤层巷道裂隙演化及围岩破坏特征,建立了重复冲击巷道围岩弹塑性理论破坏模型,阐明了动静载叠加条件下特厚煤层巷道围岩弹塑性区及破碎区的动态演化规律,计算了某典型巷道重复冲击载荷下围岩松动破坏的极限范围.推导了在动静载叠加作用下巷道围岩弹塑性区、破碎区范围平衡方程,得到了破碎区与塑性区范围均与巷道半径、覆岩压力及冲击震动强度呈正相关,与巷道围岩支护强度呈负相关,巷道断面半径对围岩松动圈范围影响较大;分析了围岩裂隙演化及破坏特征,张拉裂隙的衍生是浅部破碎区发育的重要原因,剪切滑移裂隙的扩展是深部塑性区发展的主导因素;阐明了重复冲击特厚煤层巷道破坏及控制机理,当冲击震动波传递至巷道时,松散脆质煤层中原生发育的大量裂纹迅速扩张,裂隙带相互交错、贯通,瞬间造成巷道围岩承载稳定结构破坏;工程算例某矿巷道围岩破碎区与塑性区深度范围,提出了重复冲击地压巷道防冲支护路径,采用“硬顶预裂+煤体双卸+锚网强支”技术提高了重复冲击震动条件下巷道围岩稳定性.研究结论和成果对重复冲击矿震巷道围岩稳定性控制有积极参考和借鉴意义.

Focusing on the large deformation and roof collapse generally occured for under-ground roadway in extra-thick coal seam affected by the multiple coal burst,both the fracture evolution and damage characteristics of the surrounding rock was investigated upon the de-struction mechanism of surrounding rock and dynamic theory for coal burst.In the present re-search,the elasto-plastic theoretical damage model with the consideration of multiple impact disturbances was initially established and the dynamic evolution law either in terms of the elas-tic-plastic zone or the damage zone of the surrounding rock under the combined dynamic and static loads were elucidated.Subsequently,the maximum range of the loose destruction zone of surrounding rock was calculated upon the given coal mine.The theoretical equations of elastic-ity,plasticity and crushing zone were then derived,suggesting that both the range of crushing zone and plastic zone were positively correlated with the radius of the roadway,the pressure of overburden and the intensity of the impact and vibration,whereas the value of which are nega-tively correlated with the strength of the peripheral support.In particular,the influence of the roadway radius is much more significant on the range of peripheral rock looseness zone.The e-volution and destruction characteristics of the fissures within the peripheral rock was indicated that the derivation of tensile fissures is an important reason for the development of shallow crushed zone,while the expansion of shear slip fissures plays the dominant role in the develop-ment of deep plastic zone.The damage and control mechanism of the roadway in this case was also clarified,which demonstrated that a large number of cracks originally developed in the loose and brittle coal seam,when the shock wave is transmitted to the roadway.These cracks expanded quickly and the fracture zones intersect and penetrate each other,which instantly caused structural damage and affect the load bearing stability of surrounding rock.Upon the calculated range of damage area and plastic zone,the technique route for the roadway support featured with the technology of"hard top pre-cracking+coal body double unloading+anchor network strong support"was proposed and put into practice.It is believed that the main find-ings obtained from this research provide a new insight and meaningful reference to maintain the stability of surrounding rock subjected to multiple coal bursts.