软岩回采巷道底臌破坏机制与支护技术

Failure mechanism of floor heave and supporting technology of soft rock roadway

软岩巷道底臌治理一直是软岩支护中重点攻关的难题之一,作为受采动压力影响的软岩回采巷道来说,巷道的底臌问题尤为突出。针对山东能源临矿集团上海庙矿区软岩大变形技术难题,首先从巷道底臌变形的力学机制入手,根据巷道围岩本构关系及应力作用模式,在结合朗肯压力理论的基础上建立了剪切错动型巷道底臌力学模型,导出了巷道底臌力源P0的计算方程。计算分析知,当底臌压力P0大于底板岩体的强度极限时,巷道底板岩体将发生剪切和扩容变形挤入巷道空间,随时间效应的加大最终导致巷道底臌;其次,结合建立的底臌力学模型,提出了一种与剪切错动型巷道底臌力学机理相适应的新型反底拱底臌控制技术,对反底拱伸出段、底板预应力锚杆和反底拱主体段3部分在底臌控制过程中的作用进行理论分析,揭示了其“控底-助帮”的底臌控制机理,并综合数值计算和正交实验的方法对新型反底拱结构的3个主要参数进行试验优化,模拟显示影响巷道底臌量指标的主要因素为底板超挖深度和反底拱伸出段长度,影响巷道两帮移近量指标的主要因素为反底拱伸出段长度;最后,通过对榆树井矿13803工作面回风巷原始支护条件下底板压力的验算,确定了底板围岩压力与矿井水的耦合作用是造成该巷道底臌的主要原因,并根据优化后的底板治理方案在榆树井煤矿13803工作面回风巷返修段进行工业性试验。工程实践表明,该项新技术控制软岩回采巷道底臌及两帮变形效果较好,有效保证了工作面回采期间巷道的稳定性。

Control of roadway bottom heave in soft rock is always one of the key problems in soft rock support system.The problem of roadway bottom heave affected by mining pressure is particularly prominent in mining roadway.This research was conducted by aiming the technical problem of large deformation of soft rock in Shanghaimiao mining area of Shandong Energy Linyi Mining Group.Firstly,the mechanical model of roadway floor heave with shear dislocation was established based on the constitutive relation of surrounding rock and the stress action mode by using Rankine pressure theory,and then an analytical formula for calculating the force source P 0 which caused the roadway bottom heave was derived.According to the calculation of the model,it was found that the rock mass of roadway floor will have shear expansion and dilatational deformation,which makes roadway floor squeezes into the roadway space when the pressure P 0 of bottom heave is greater than the ultimate strength of floor rock mass,which eventually leads to floor heave with the increase of time effect.Secondly,combined with the mechanical model of bottom heave,a new type of anti-bottom arch control technology which is suitable for the mechanics mechanism of bottom heave in the shear- staggered roadway was developed,and the theoretical analysis was made on the functions of three parts,including the overhang of anti-bottom arch,floor prestressed bolt and the main section of anti-bottom arch in the process of bottom heave control which reveals the controlling mechanism of bottom heave.By using the numerical calculation and orthogonal experiment,three main parameters of the new inverted arch structure were optimized.Simulation results show that the main factors affecting the index of floor heave are the overbreak depth of the floor and the length of the overhang of the anti-bottom arch,and the main factors affecting the index of convergence of two ribs of the roadway is the length of the overhang of the anti-bottom arch.Finally,based on the stress checking of the floor under the original support condition for track gateway at the13803 working face of Yushujing coal mine,it was determined that the coupled effect of the rock pressure of floor and mine drainage was the main reason which caused the bottom heave.Then,according to the optimized floor treatment scheme,a field industrial test was carried out in the track gateway repair section of13803 working face of Yushujing coal mine.The engineering practice shows that the new technology has a good effect on controlling the roadway bottom heave and walls deformation in soft rock and it effectively guarantees the roadway stability during the working face extraction.