注浆改造厚含水砂层提高开采上限技术及应用

Technology of raising upper limit of mining by grouting reconstruction in thick water-bearing sand layer and its application

为了实现在厚松散含水砂层下留设防塌煤(岩)柱以提高开采上限,研究厚含水砂层区域注浆改造技术。以安徽淮北五沟煤矿1010-1工作面第四含水层(简称四含)下提高上限开采为目标,通过理论计算、注浆材料配比实验和原位注浆试验,对改造范围和层位、注浆材料的适用性、不同深度的浆液配比、钻孔布置方式和注浆方法进行分析,并通过取心测试、水文地质试验和井下钻孔验证对注浆效果进行检验。结果表明:五沟煤矿四含改造区域松散含水砂层底部无黏土,且在有含水风化基岩条件下,提高上限开采需同时注浆改造松散砂层和风化基岩;粉煤灰–水泥浆较石膏–水泥浆具有更好的体积稳定性,粉煤灰掺量20%~50%的粉煤灰–水泥浆结石率大于98%,且有较稳定的凝结强度,能够满足砂层劈裂注浆的需求,风化基岩采用纯水泥浆或10%以内掺量的粉煤灰–水泥浆,基岩之上2倍采高的砂层注入10%~20%掺量的粉煤灰–水泥浆改造后充当保护层,上部采用20%~50%掺量的粉煤灰–水泥浆进行充填压密,粉煤灰掺量随注浆深度递减;注浆终压可在最浅部砂层注浆劈裂压力的基础上,按地层压力和孔隙水压力梯度0.3 MPa/10 m增加;泄压诱导注浆可有效控制浆液的劈裂扩散方向,浆液最大扩散距离达到89.5 m;注浆后砂层和风化基岩完整性显著提高,岩(土)体试块强度提高2~5倍,注浆将砂层改造为富水性弱、极微–微透水的隔水层,可实现留设防塌煤(岩)柱提高上限开采。

In order to set anti-collapse coal(rock)pillars in the thick loose water-bearing sand layer to raise the upper limit of mining,the grouting transformation technology of thick water-bearing sand layer was studied.Aiming at raising the upper limit of mining in the fourth aquifer in working face 1010-1 of Wugou Coal Mine in Huaibei,Anhui.The ana-lysis is conducted through theoretical calculation,experiments on of grouting materials ratio,and in-situ grouting test,with a focus on the scope and horizon of transformation,the applicability of grouting materials,the mix ratio of grout at different depths,the arrangement of drilling holes and the grouting methods.Meanwhile,the effect of grouting was veri-fied by core test,hydrogeological test and underground drilling.The results indicate that:The loose sand layer and the weathered bedrock were modified by grouting while the upper limit mining was raised under the conditions without clay but with water-bearing weathered bedrock on the bottom of loose water-bearing sand layer in the“quaternary aquifer”modification area of Wugou Coal Mine.Besides,the fly ash-cement slurry has better volume stability than the gypsum-cement slurry.Definitely,the fly ash-cement slurry with 20%‒50%fly ash has the hardening rate greater than 98%,and has a relatively stable condensation strength,which could meet the requirements of splitting grouting in the sand layer.In terms of the weathered bedrock,the pure cement slurry or the fly ash-cement slurry with less than 10%fly ash were ad-opted.Specifically,the sand layer twice the thickness of mining above the bedrock was grouted with fly ash-cement slurry at the fly ash content of 10%‒20%to act as a protective layer.The upper layer was filled and compacted with the fly ash-cement slurry at the fly ash content of 20%‒50%.Generally,the fly ash content decreases with the grouting depth.The final grouting pressure can be increased by the formation pressure and pore water pressure gradient+0.3 MPa/10 m on the basis of the grouting splitting pressure in the shallowest sand layer.The grouting induced by pressure relief can effectively control the splitting diffusion direction of grout,and the maximum diffusion distance of grout reaches 89.5 m.After grouting,the integrity of the sand layer and the weathered bedrock is improved significantly,the strength of rock(soil)test block is increased 2‒5 times,and the sand layer is transformed into water barrier layer with poor water richness and extremely low to low water permeability,capable of raising the upper limit of mining by setting anti-collapse coal(rock)pillars.