孟巴矿厚松散含水层下协调保水开采模式

孟巴矿的地质采矿条件具有近地表松散富含水层厚、煤层顶板厚、煤层厚的"三厚"特征,开采煤层覆岩中含有多个含水层组,矿井水害是威胁矿井安全生产的主要因素。在覆岩多水体条件下,为了有效防止近地表厚松散UDT含水层进入井下,导致淹井灾害发生,提出上保下疏的开采水害防治模式。一分层安全开采的关键技术是控制复合关键层的结构稳定,应用初始后屈曲理论解析其稳定性,得出结构关键层的极限破坏长度,通过线性回归给出分层开采覆岩导水裂缝带发育高度预计计算公式,分析确定了一分层开采工作面宽度不超过150 m,限高开采3 m;依据对UDT含水层防护的安全煤岩柱高度确定二分层开采高度,二分层开采后覆岩结构关键层发生破坏,既能够有效疏放LDT隔水层以下含水层水,又能够保证LDT隔水层的完整性,达到UDT水体不发生下泄的目的,保障了矿井安全开采;根据工作面协调减损开采原理,确定开采分层合理错距约为82 m,下分层的巷道布置在上分层开采采空区下的厚煤层分层错距协调限高开采布置模式,实现有效降低了覆岩应力的叠加效应,减轻LDT隔水层的变形破坏程度。开采结果表明:厚煤层分层协调布置开采方法,有效减轻了UDT含水层下LDT隔水层应力叠加损伤程度,保护了隔水层的完整性;一分层限高综采,二分层限高综放开采分次疏放了煤层顶板至LDT底板2个含水层组,解决了矿井排水能力较小条件下的水害防治问题;分层工作面错距协调布置开采方法,有效降低了开采边界导水裂缝带发育高度,减小了LDT变形破坏程度,同时释放了一分层区段煤柱应力,实现了覆岩整体下沉,不但有效地降低了覆岩破坏高度,而且减小了冲击矿压冲击强度,开采期间UDT水位变化幅度稳定保持在一定范围内,实现了多水体条件下上保下疏的厚煤层分层安全开采模式。

Coordinated waterproof mining mode under thick loose sand stratum in Barapukuria coal mine

The geological mining conditions of Barapukuria coal mine are characterized by “three thick” features of strata structure,namely the aquifer with thick unconsolidated formation near the surface,the special thick coal seam and thick roof.There are many aquifer groups in the overburden strata above coal seams.Water hazard in the coal mine is the main factor that threatens safe mining.Under the condition of overburden and multi-water body,in order to prevent the water in the loose UDT aquifer near the surface entering the underground longwall face,and avoid the water outburst disaster in the mine,the prevention and control mode of mining water hazard is put forward to protect the upper aquifer and drain the lower aquifer.The key technology of one-layer safe mining is to control the structural stability of compound key stratum.The initial post-buckling theory is used to analyze the stability of compound key stratum,and the ultimate failure length of key stratum is obtained.Under stratified mining condition,the formulas for predicting the development height of water conducted fracture zone in overlying strata are given by linear regression,and the width of working face in stratified mining is not more than 150 m and the mining height is limited to 3 m.According to the safe height of coal pillar to protect UDT aquifer,the mining height of second-layer mining is determined.After second-layer mining,the key stratum of overburden structure is destroyed,which can not only effectively drain the aquifer water below the LDT aquiclude,but also ensure the integrity of the LDT aquiclude,and it can achieve the purpose of UDT water body with no leaking,which ensures the safe mining of the coal mine.According to the principle of coordinated and damage reduction mining in working face,it is determined that the reasonable offset of mining layers is about 82 m.Layout pattern of stratified thick coal seam and limited mining height with rational offset is put up.The roadway of lower seam is located under the upper goaf,which can reduce the superposition of overburden stress and the deformation and damage of LDT aquiclude.The mining results show that the method of layered coordinated mining in thick seam can effectively reduce the stress superposition damage of LDT aquiclude under UDT aquifer and protect the integrity of aquiclude.In one-layer limited-height fully mechanized mining and two-layer limited-height fully mechanized caving mining,two aquifer groups from coal seam roof to LDT floor are separately drained,which solves the problem of water hazard prevention and control under the condition of small drainage capacity of mine.The staggered coordinated layout mining method of stratified working face effectively reduces the development height of water conducted fracture zone at mining boundary,reduces the degree of LDT deformation and damage,releases the stress of coal pillar in a stratified section,and realizes the overall subsidence of overburden.It not only effectively reduces the height of overburden failure,but also reduces the impact strength of rock burst.During the mining,UDT water level changes within a certain range,which realizes the safe mining mode of thick seam with upper and lower sparse seams under the condition of multi-water body.