特殊软岩软化的微观机制研究

RESEARCH ON SOFTENING MICRO-MECHANISM OF SPECIAL SOFT ROCKS

软岩软化的机制问题是涉及到软岩力学变异性和工程设计的重要问题。针对华南地区广为分布的“红层”——红色砂岩、泥岩以及炭质泥岩等特殊软岩,结合广东省东深供水改造工程建设,设计了该类软岩的系列饱水试验。通过扫描电镜、偏光显微镜、能谱分析、粉晶X射线衍射以及岩石的物理力学测试等手段测定软岩微观结构、矿物成分、物理力学性质、水溶液的化学成分及其随时间的变化特点,揭示软岩性质软化的动态变化规律,探讨其软化微观机制。研究表明,该类软岩的软化主要是由于粘土矿物吸水膨胀与崩解机制、离子交换吸附作用、易溶性矿物溶解与矿物生成、软岩与水作用的微观力学作用机制、软岩软化的非线性化学动力学机制的综合作用造成的。分析认为,粘土矿物吸水膨胀与崩解机制、离子交换吸附机制及软岩与水相互作用的微观力学作用机制在该类软岩软化中起主导作用。而软岩软化的非线性动力学机制是软岩软化定量研究的重要方向之一。

Softening mechanism of soft rocks is the basis of the mechanical characteristics of soft rocks and engineering design. Combined with the Dongjiang to Shenzhen Water Supply Reconstruction Project in Guangdong Province, a series of experiments on saturated soft rocks including red sandstones and mudstones, which are widely distributed in South China, are designed and conducted. By some testing methods, such as scanning electron microscope, polarizing microscope, energy spectrum analysis, X-ray diffraction, physicomechanical experiments of soft rocks, as well as chemical analysis of water sample, the research obtains a series of data, such as microstructures, mineral composition, physicomechanical properties of soft rocks, and chemical composition of water solution. Then, more attention is paid to the softening mechanism of the soft rocks. The research results show that the softening mechanisms of soft rocks include water-absorbing expansion of clay mineral, disintegrating mechanism, ionic exchanging and absorbing action, mineral dissolution and creation of fusible mineral, micro-mechanical mechanism of the interaction between soft rocks and water, and the nonlinear chemical dynamics mechanism. The main causes of softening of soft rocks are water-absorbing expansion of clay mineral, ionic exchanging, and absorbing action and micro-mechanical mechanism under the interaction between soft rocks and water. Mechanism of nonlinear dynamics can explain the dynamic chemical process, and it is one of the important directions of quantitative research on softening of soft rocks in the future.