Liu Lei, Ge Zhaolong, Zhou Zhe, Li Zhongtan, Deng Qinglin
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China; School of Resources and Safety Engineering, Chongqing University, Chongqing 400044, China.
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China; School of Resources and Safety Engineering, Chongqing University, Chongqing 400044, China.
Sci Total Environ. 2024 Nov 20;952:175944. doi: 10.1016/j.scitotenv.2024.175944. Epub 2024 Aug 31.
The microstructure and mechanical properties of coal measure rocks (CMR) are critical factors in the successful geological storage of CO. While previous research has predominantly focused on coal seams, the overlying and underlying bedrock strata are equally significant yet often overlooked. This study addresses this gap by selecting coal and adjacent strata from the Twelve Mine as representative samples. A comprehensive suite of analyses was conducted, including thin section identification, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), uniaxial compression, and acoustic emission tests. These analyses were used to determine the mineralogical composition and pore structure characteristics of the CMR, elucidate the mechanical failure mechanisms of different CMR types, and explore the relationships between rock strength, mineral composition, and pore characteristics. The findings indicate that the primary minerals in coal are clay minerals, while mudstone is composed predominantly of clay minerals and quartz, sandstone is rich in quartz and feldspar, and limestone contains significant amounts of calcite. The porosity of CMR varies between 1.73 % and 10.12 %, with 82.72 % of the pores being micro- to mesopores and the remaining 17.28 % being macropores. The pore structures exhibit fractal characteristics, with the fractal dimension of mesopores ranging from 2.581 to 2.902, and that of macropores from 2.968 to 2.997. Coal predominantly fails through a combination of tensile and shear failure mechanisms, mudstone and limestone through tensile failure, and sandstone through shear failure. Furthermore, the results suggest that rock strength is positively correlated with quartz content and negatively correlated with kaolinite content and porosity. In terms of their influence on coal rock strength, the factors in descending order of impact are kaolinite, quartz, calcite, microporosity, macroporosity, dolomite, and mesoporosity. Thus, while the mechanical properties of these rocks are primarily governed by their mineralogical composition, the pore structure also plays a significant role.
煤系岩石（CMR）的微观结构和力学性能是二氧化碳地质封存成功的关键因素。虽然先前的研究主要集中在煤层，但其上覆和下伏基岩地层同样重要却常常被忽视。本研究通过选取十二矿的煤及相邻地层作为代表性样本，填补了这一空白。进行了一系列综合分析，包括薄片鉴定、X射线衍射（XRD）、核磁共振（NMR）、单轴压缩和声发射测试。这些分析用于确定CMR的矿物组成和孔隙结构特征；阐明不同类型CMR的力学破坏机制；并探索岩石强度、矿物组成和孔隙特征之间的关系。研究结果表明，煤中的主要矿物是粘土矿物，而泥岩主要由粘土矿物和石英组成，砂岩富含石英和长石，石灰岩含有大量方解石。CMR的孔隙率在1.73%至10.12%之间，其中82.72%的孔隙为微孔至中孔，其余17.28%为大孔。孔隙结构呈现分形特征，中孔的分形维数在2.581至2.902之间，大孔的分形维数在2.968至2.997之间。煤主要通过拉伸和剪切破坏机制组合破坏，泥岩和石灰岩通过拉伸破坏，砂岩通过剪切破坏。此外，结果表明岩石强度与石英含量呈正相关，与高岭石含量和孔隙率呈负相关。就其对煤岩强度的影响而言，各因素的影响程度从大到小依次为高岭石、石英、方解石、微孔率、大孔率、白云石和中孔率。因此，虽然这些岩石的力学性能主要受其矿物组成控制，但孔隙结构也起着重要作用。
