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为探讨泥岩在遇水–风干循环作用下断裂的微观机制,采用粉晶X射线衍射、力学性能测试和激光共聚焦显微镜等手段对泥岩进行表征,得到泥岩遇水后的成分变化、强度特征和遇水–风干循环作用下泥岩三维形貌的变化规律,分析泥岩在遇水–风干循环作用下断裂的微观机制。结果表明:泥岩遇水后部分钾长石变为高岭石;单轴抗压强度从5.31 MPa降为0 MPa;试样表面的裂纹数目、宽度随遇水–风干次数的增加而增加;伊利石黏粒遇水后水分子进入黏粒晶胞之间,引起晶格膨胀;黏粒表面吸附的水膜导致黏粒间距增加;泥岩遇水过程中在水的物理、化学作用下内部产生大量次生孔隙并且体积膨胀;风干过程中泥岩表层风干速度大于内部风干速度,表层局部黏粒富集区域体积收缩产生裂纹,随着遇水–风干循环次数的增加,泥岩内部裂纹的数量和尺寸逐渐增加,当裂纹贯穿试样时试样断裂。
In order to investigate the microscopic mechanism of fracture of mudstone under water-air-drying cycle, the characteristics of mudstone were characterized by X-ray powder diffraction, mechanical properties test and laser scanning confocal microscopy. Under water-air-dry cycle, the variation of mudstone three-dimensional topography was analyzed, and the microscopic mechanism of mudstone fracture under water-air drying cycle was analyzed. The results show that part of K - feldspar changed into kaolinite after mudstone metamorphism, the uniaxial compressive strength decreased from 5.31 MPa to 0 MPa, the number and width of cracks on the sample surface increased with the increase of water - The water molecules in the stone clay particles enter the space between the clay particles and cause the lattice expansion; the water film adsorbed on the surface of the clay particles leads to an increase in the distance between the clay particles; and the mudstone encounters a large amount of internal volume under the physical and chemical action of water Secondary pores and volume expansion. During the air-drying process, the surface air-drying rate of mudstone is higher than the internal air-drying speed, and the volume shrinkage in the local clay-enriched area produces cracks. With the increase of water-air drying cycles, the number and size of internal cracks Increase, when the crack through the specimen when the sample fracture.