崩落法采空区散体与围岩相互作用的数值模拟

Numerical simulation of interaction between ore-rock granular and surrounding rock in goaf of caving method

崩落式采矿法在覆岩下出矿,将崩落的围岩散体遗留在上部采空区,从而对上下盘围岩起到支撑作用。在不同的矿体形态和岩体强度、矿岩散体流动状态的条件下,崩落散体的支撑作用不尽相同,这导致崩落采空区的垮落范围与地下采场的地压显现也存在差异,其形成的应力集中区和上盘陷落区对后续开采构成较大风险。针对这一问题,基于裂纹尖端存在微裂纹损伤假设,使用离散元数值模拟的方法,对比分析了不同围岩强度、不同矿体采空区倾角条件下,放矿过程中矿岩散体与围岩的相互作用和围岩破坏形式。研究结果表明:竖直或陡倾斜的采空区应力分布相对均匀,但采空区具有一定倾角时在上盘顶部会出现应力降低区,上盘底部出现应力集中区;围岩强度较高时,应力分布较为均匀,而围岩强度低时上盘围岩会较早发生破坏,从而释放应变能,不易产生应力集中区;在围岩强度较低时,可通过及时回填废石以减小围岩变形、迟滞上盘围岩底部产生的应力集中趋势、延后破坏时间。研究结果对采用崩落法开采的矿山控制采场地压具有重要的借鉴意义。

The caving mining method draws ore under the overburden,leaving the collapsed surrounding rock mass in the upper goaf,thus supporting the hanging and footwall surrounding rock.Under the conditions of different ore body shapes,rock mass strengths,and flow states of ore and rock masses,the supporting effect of the ore-rock granular is different,which leads to the difference between the damage scope of the caving goaf and the ground pressure appearance of the underground stope.The stress concentration areas and hanging wall collapse areas will pose significant risks to the subsequent mining.In view of this,based on the assumption of microcrack damage at the crack tip,the discrete element numerical simulation method is adopted to compare and analyze the interaction between the ore body and surrounding rock and the failure mode of surrounding rock in the process of ore drawing under the conditions of different surrounding rock strength,different mined-out area dip angle and whether backfill or not.The results show that the stress distribution in vertical or steeply inclined goafs is relatively uniform,while there is a stress-relaxed area at the top of the hanging wall and a stress concentration zone at the bottom of the hanging wall in the inclined goaf;for the surrounding rock with high strength,the stress distribution is relatively uniform,while the hanging wall surrounding rock will be damaged earlier when the surrounding rock strength is low,thus releasing strain energy and not easy to produce stress concentration areas.For the surrounding rock with low strength,the waste rock can be backfilled in time to reduce the deformation of surrounding rock,delay the stress concentration trend at the bottom of hanging wall surrounding rock,and delay the failure time.The research conclusion has important reference significance for controlling the ground pressure of stopes using caving mining method.