水岩作用下泥质板岩软化非线性机制研究

水岩作用下泥质板岩表现出明显的软化特征。通过单轴压缩试验分析了泥质板岩软化过程中单轴压缩强度、弹性模量和泊松比与吸水时间之间的关系；借助核磁共振试验研究了水岩作用下泥质板岩软化过程中孔隙的产生、扩展和贯通规律，分析了泥质板岩软化过程中孔隙度与吸水时间之间的关系；采用电镜扫描试验分析了水岩作用下泥质板岩软化过程中微观结构的演变规律，基于分形理论研究了不同浸泡时间下泥质板岩分形维数的变化规律；运用非线性动力学理论，选取微观结构孔隙形状分维值、孔隙度、单轴抗压强度、弹性模量作为描述泥质板岩与水溶液相互作用系统的变量，建立了水岩作用下泥质板岩的软化模型，结合试验数据验证了模型的适用性。结果表明：泥质板岩单轴抗压强度、弹性模量随吸水时间增大而减小，呈负线性相关，而泊松比与吸水时间之间的关系不明显；在浸泡初期，水岩作用强烈，泥质板岩内部微孔隙会发生扩展贯通进而形成更大尺寸的孔隙，孔隙度在浸泡初期增长较快；随着浸泡时间的延长，水岩作用减弱，孔隙度增长速率趋缓；随着吸水时间的推移，泥质板岩内部孔隙相互连通，进而形成复杂网状结构的大孔，泥质板岩分形维数呈对数增长，最终趋于稳定；采用非线性模型计算的结果与试验数据较接近，说明泥质板岩的软化过程具有明显的非线性动力学特征，利用非线性动力学模型可以较好地表征水岩作用下泥质板岩的软化规律。研究成果可为软岩?水相互作用理论研究提供参考。

Nonlinear softening mechanism of argillaceous slate under water-rock interaction

The argillaceous slate obviously shows softening characteristics under water-rock interaction. The relationship between the uniaxial compressive strength (UCS), elastic modulus, Poisson’s ratio and water absorption time in the softening process of argillaceous slate is analyzed by conducting uniaxial compression tests. The laws of pore generation, expansion and breakthrough in the softening process under water-rock interaction are studied by using the nuclear magnetic resonance (NMR). The relationship between porosity and water absorption time in the softening process is analyzed. The evolution rule of microstructure in the softening process of argillaceous slate under water-rock interaction is analyzed by the scanning electron microscope (SEM). Based on the fractal theory, the change rule of the fractal dimension under different soaking time is studied. The fractal dimension value of pore microstructure, porosity, UCS and elastic modulus are selected as the changes of describing the interaction system of argillaceous slate and water solution by using the nonlinear dynamics theory. The applicability of the model is verified with experimental data. The results show that UCS and elastic modulus decrease with the increase of water absorption time, showing a negative linear correlation, but there is no obvious relationship between the Poisson’s ratio and water absorption time. At the early stage of immersion, the water-rock interaction is strong, and the micropores in the slate expand and penetrate to form larger pores, and the porosity increases rapidly. With the increase of water absorption time, the pores in the argillaceous slate are connected with each other to form large pores, which leads to the complex network structure. The fractal dimension of argillaceous slate increases logarithmically and tends to be stable gradually. The results calculated by the nonlinear model are close to the experimental data, which shows that the softening process of argillaceous slate has the obvious nonlinear dynamic characteristics, and the softening law of argillaceous slate under water-rock interaction can be better characterized by the nonlinear dynamic model. The results can provide a reference for the theoretical study of soft rock-water interaction.