煤矿地下水库煤柱坝体宽度设计

Design on the width of coal pillar dam in coal mine groundwater reservoir

地下水库储水技术已成为西部矿区实现煤炭高效开采与水资源保护并重的重要途径之一,而煤柱坝体的稳定性是地下水库设计中极其重要的部分,对地下水库稳定性起决定性作用。煤柱坝体既要保证煤炭安全开采,也要保障地下水库安全运行。地下水库煤柱坝体的稳定不仅与埋深、采动应力、地质构造等工程地质条件有关,也与水作用下的弱化作用密切相关。为研究煤矿地下水库煤柱坝体在水作用下强度弱化规律,选取西部矿区麻地梁矿5煤为研究对象,开展煤样无损浸水试验和不同含水率及反复浸水条件下单轴压缩试验。研究得到:不同含水率的煤样在0～20 h内,含水率快速增长; 20 h之后,含水率增长变缓,在20～70 h,含水率慢速增长;在70～140 h,煤样含水率增长接近稳定;煤样含水率随着浸水时间的增加而增加,但增幅逐渐减少,最终趋于稳定;随着含水率(浸水次数)的增多,煤样单轴抗压强度逐渐降低,峰值应变逐渐增大,弹性模量逐渐降低。相较于干燥煤样,初次饱水煤样、浸水3次煤样单轴抗压强度分别降低了27.1%,50.0%,弹性模量分别降低34.6%,58.5%。结合实验室试验结果,运用弹塑性力学理论探讨了煤柱坝体在不同含水率下破坏区、塑性区宽度,开展了考虑覆岩压力、水压力以及水的弱化作用下煤柱坝体宽度设计研究,并结合麻地梁矿的工程地质条件,对其地下水库坝体的宽度进行了设计。同时,进一步分析了煤柱坝体宽度的影响因素,得到含水率、埋深、煤层采厚均对煤柱坝体宽度有很大影响。

Groundwater reservoir technology is a vital way to achieve both efficient mining and water conservation in western coalfields in China.The stability of coal pillar dam is an emphasis of reservoir design,which plays an important role in the stability of groundwater reservoirs.Coal pillar dam should ensure the safety of coal mining,as well as the safe operation of groundwater reservoirs.The stability of coal pillar dam is closely related to water weakening and engineering geological conditions,such as buried depth,mining stress,geological structure and so on.In order to study the strength weakening law of coal pillar dam of groundwater reservoirs under water,this paper took Madiliang mine No.5 in western mining area as the research object,carried out a non-destructive water immersion test on coal sample and a uniaxial compression test on coal sample under various water content and repeated soaking.The results show that the water content of coal samples with various water content increased rapidly within 0-20 h;after 20 h,the grew rate slowed down;and in 20-70 h,the water content grew slowly;in70-140 h,the growth of water content of coal sample was nearly stable.In conclusion,the water content of coal sample increases with the soaking time,but the increase rate gradually decreases,and finally tends to be flat.With the increase of water content (the number of times of soaking),the uniaxial compressive strength of coal sample decreases gradually,but the peak strain increases gradually,and the elastic modulus decreases gradually.Compared with the dry coal sample,the uniaxial compressive strength of the first water-saturation coal sample and the coal sample with the third soaking decreased by 27.1% and 50.0% respectively,and the elastic modulus decreased by 34.6% and 58.5% respectively.Combined with the above results and the elastic- plastic mechanics theory,this paper discussed the damage zone and plastic zone width of coal pillar dam under various water content,carried out the research of coal pillar dam width considering overburden rock pressure,water pressure and water weakening,and designed the width of the groundwater reservoir combining with the engineering geological conditions of Madiliang mine.At the same time,the paper further analyzed the influencing factors of the width of coal pillar dam,concluding that the width of coal pillar dam is closely affected by water content,buried depth,and mining thickness.