Abstract Mylonite coal is known to be highly tectonically deformed coal and is a result of crushing original coal into fine-grained coal under multiple tectonic events. Because of its granular nature and the resultant inferior mechanical property, the borehole stability during both drilling and gas drainage is challenging due to unpredictable failures. This study explored a potential approach to enhance the bulk strength of mylonitic coal via microbiologically-mediated CaCO3 cementation which effectively increases the cohesion of the fine coal particles through the bio-cementation process. The experimental results indicated that the mechanical strength was significantly enhanced after a short period of biotreatment with 12 cycles of biotreatment yielding a maximum stiffness of 32 KN/mm and maximum uniaxial compressive strength of 9.3 MPa. The strength evolution behavior demonstrated that the macroscopic failure behavior of mylonite coal evolves from plastic failure to brittle failure as the increase of bio-treatments. The results from XRD indicated that the generated CaCO3 crystals mainly occurs in the form of calcite and vaterite. Imaging by SEM further indicated the cementation process for CaCO3. The generated CaCO3 precipitation first occurs on random spots on the particle surfaces, and then occupies the interstitial space until particle-particle bonds are generated.

中文翻译：

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一种通过微生物介导的碳酸盐胶结提高糜棱煤体积强度的新方法

摘要 糜棱煤是一种高度构造变形煤，是原煤在多次构造作用下破碎成细粒煤的产物。由于其颗粒性质和由此产生的较差的机械性能，由于不可预测的故障，钻井和瓦斯抽放过程中的井眼稳定性具有挑战性。本研究探索了一种通过微生物介导的 CaCO3 胶结提高糜棱煤体积强度的潜在方法，该方法通过生物胶结过程有效地增加了细煤颗粒的内聚力。实验结果表明，经过 12 次生物处理周期的短时间生物处理后，机械强度显着提高，最大刚度为 32 KN/mm，最大单轴抗压强度为 9.3 MPa。强度演化行为表明，随着生物处理的增加，糜棱岩煤的宏观破坏行为从塑性破坏演变为脆性破坏。XRD结果表明生成的CaCO3晶体主要以方解石和球霰石的形式存在。SEM 成像进一步显示了 CaCO3 的胶结过程。生成的 CaCO3 沉淀首先发生在颗粒表面的随机点上，然后占据间隙空间，直到产生颗粒-颗粒键。SEM 成像进一步显示了 CaCO3 的胶结过程。生成的 CaCO3 沉淀首先发生在颗粒表面的随机点上，然后占据间隙空间，直到产生颗粒-颗粒键。SEM 成像进一步显示了 CaCO3 的胶结过程。生成的 CaCO3 沉淀首先发生在颗粒表面的随机点上，然后占据间隙空间，直到产生颗粒-颗粒键。