软岩软化的水岩界面动力学模型及其演化规律

Dynamic model for water-rock interface of softening of soft rock and its evolution law

软岩的软化机制本质上是水岩界面改变引起的微细观结构的劣化,对水岩界面的研究具有十分重要的意义。考虑到软岩的一般性特征,从胶结成岩过程的逆过程出发,对不同浸水时间的粉砂质泥岩浸泡液进行了化学元素测试。利用偏光显微薄片研究了软岩微细观结构的演化过程,提出了界面胶结连接结构的概念,建立了软岩软化过程的水岩界面演化模型。基于扩散理论,推导了描述水岩界面演化的理论方程,并与试验结果进行比对。推导和提出了软岩细观软化损伤因子,并将其引入块体离散元数值计算中。研究表明:软岩软化过程中伴随着颗粒的脱落和悬浮以及可溶性物质的溶解,软岩的软化具有明显的非线性动力学特征,理论计算值与试验结果的拟合程度较高,验证了理论方程的可靠性和合理性。数值模拟结果与试验结果吻合度较高。

The softening mechanism of soft rock is essentially the deterioration of microstructure caused by change of water-rock interface.The research on the water-rock interface is of great importance.Considering the general characteristics of the soft rock,from the idea of the inverse process of cemented diagenesis,the chemical element analysis of silty mudstone soak solution with different immersion time is carried out.The evolution process of microstructure of the soft rock is studied by using the polarized light micro-section.The concept of interfacial cemented bonding structure is proposed to investigate the established model for evolution of water-rock interface.Based on the diffusion theory,the theoretical equation describing the evolution of water-rock interface is derived and compared with the experimental results.The meso-softening damage factor of soft rock is proposed and deduced,and introduced into block discrete element simulation.The results show that the softening process of the soft rock is accompanied by the shedding and suspension of particles and the dissolution of soluble substances.Besides,the softening of the soft rock has obvious nonlinear dynamic characteristics.The fitting degree between the calculated values and the experimental results is relatively high,which verifies the reliability and rationality of the theoretical equation.The numerical results are in good agreement with the experimental ones.