采煤地裂缝MICP修复规律及影响因素实验研究

Experimental study on MICP restoration law and influencing factors of coal mining ground fissures

  • 摘要: 西北黄土覆盖区采煤地裂缝造成浅表水资源漏失和土体失稳,为此开展黄土覆盖区采煤地裂缝微生物诱导碳酸钙沉淀(Microbial Induced Carbonate Precipitation,MICP)修复实验研究。以陕北柠条塔煤矿为研究背景,对采煤地裂缝特征进行观测,揭示采煤地裂缝发育特征。结合矿山压力观测,划分黄土采煤地裂缝类型。基于采煤地裂缝分类和特征,采用无侧限抗压实验、三轴抗压实验、变水头渗透实验及三轴渗透实验,对比测试了2类裂缝黄土MICP修复样品的力学和水理参数。基于修复体pH值、MICP碳酸钙产量和扫描电镜测试结果,剖析采煤地裂缝MICP修复影响因素。结果表明:黄土覆盖区采煤地裂缝可分为边界地裂缝和内部地裂缝2种类型。边界地裂缝条件下,菌液和胶结液的最佳比例为1.2:1。内部地裂缝条件下,裂缝充填物中风积沙与黄土的最佳比例为1:1,菌液和胶结液的最佳比例为1.0:1。黄土覆盖区不同类型采煤地裂缝的开度差异,造成碳酸钙产率相差31.2%,因此边界地裂缝较内部地裂缝最佳MICP修复液中胶结液成分所占比例更大。裂缝充填物中风积沙与黄土为1:1时,充填物与修复液混合体的pH值为9.2。该pH值环境碳酸钙产率可达88%,促进了MICP高效运行。研究成果为黄土覆盖区采煤地裂缝修复提供了参考。

     

    Abstract: The coal mining ground fissures in the northwest loess covered area cause shallow water resource leakage and soil instability. Therefore, the experimental study on MICP (micro induced carbon precision) restoration of coal mining ground fissures in the loess covered area were conducted. Taking the Ningtiaota Coal Mine in northern Shaanxi as the research background, the characteristics of mining ground fissures were observed and the development characteristics of mining induced ground fissures were revealed. Based on the observation of mine pressure, the types of ground fissures in loess mining were classified. Based on the classification and characteristics of coal mining ground fractures, the mechanical and hydraulic parameters of two types of fractured loess MICP restoration samples were compared and tested using unconfined compression tests, triaxial compression tests, variable head permeability tests, and triaxial permeability tests. Based on the pH value of the restoration body, MICP calcium carbonate production, and scanning electron microscopy test results, analyze the influencing factors of MICP restoration for coal mining loess ground fissures. The results indicate that coal mining ground fissures in loess covered areas can be divided into two types: boundary ground fissures and internal ground fissures. Under the condition of boundary ground fissures, the optimal ratio of bacterial solution to cementitious solution is 1.2:1. Under the conditions of internal ground fissures, the optimal ratio of sand and loess to fill the fissures is 1:1, and the optimal ratio of bacterial solution and cementitious solution is 1.0:1. The difference in the opening of different types of coal mining ground fissures in loess covered areas results in a 31.2% difference in the yield of calcium carbonate. Therefore, the optimal MICP repair solution for boundary ground fissures accounts for a larger proportion of the cementitious fluid components compared to internal ground fissures. When the ratio of windblown sand and loess in the crack filling material is 1:1, the pH value of the mixture of filling material and repair fluid is 9.2. The yield of calcium carbonate in this pH value environment can reach 88%, promoting the efficient operation of MICP. The research results provide a reference for the repair of coal mining ground cracks in loess covered areas.

     

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