富水环境下泥质板岩膨胀演变各向异性特征研究

Anisotropy of argillaceous slate swelling evolution in water-rich environment

针对富水环境下含结构面的泥质板岩在膨胀过程中所表现的各向异性特征,制备含不同角度结构面的泥质板岩重塑样,开展膨胀特性试验、核磁共振试验和扫描电子显微镜试验,分析泥质板岩膨胀各向异性宏观演变规律和微观结构变化特征;基于试验结果,建立含结构面倾角的泥质板岩三维膨胀本构模型和膨胀应力细观表达式。结果表明:在富水环境中,在结构面倾角的影响下,重塑样膨胀率–膨胀荷载呈非线性关系,与天然泥质板岩曲线趋势表现一致;在相同轴向荷载下,轴向极限膨胀率与结构面倾角呈负相关;含不同倾角结构面泥质板岩的侧向约束轴向极限膨胀率、恒体积下轴向极限膨胀应力表现出明显的各向异性,二者均与结构面倾角呈负相关;膨胀稳定后以小孔隙和中孔隙为主,大孔隙较少;泥质板岩微观基本单元以片状颗粒为主,部分为块状颗粒,且颗粒空间排列定向性较明显,颗粒之间主要为片状体的面面接触,叠聚呈塔状;随结构面倾角的增大,孔隙数量、孔隙面积和面孔率逐渐减小,孔隙边缘趋向于复杂化;含结构面的泥质板岩三维膨胀本构模型和膨胀应力细观表达式从宏–细–微观尺度定量表征了富水环境下泥质板岩膨胀演变的各向异性特征。研究成果可为软岩膨胀机制研究和软岩膨胀问题处治提供参考。

In order to study the anisotropic characteristics of argillaceous slate with structural planes during swelling in water-rich environment,the remolded argillaceous slate samples with different dips of structural planes were prepared to carry out swelling characteristics test,nuclear magnetic resonance test and scanning electron microscope test to analyze the macroscopic evolution law and microstructure change characteristics of argillaceous slate swelling anisotropy. Based on the tests results,the three-dimensional swelling constitutive model and the meso expression of swelling stress of argillaceous slate with structural plane dig are established. The results show that under the influence of the dip of the structural plane in water-rich environment,the swelling rate-swelling load of remolded argillaceous slate shows a nonlinear relationship,which is consistent with the natural argillaceous slate. Under the same axial load,the axial limit swelling rate is negatively correlated with the dip of the structural plane. Due to the structural planes with different dips,argillaceous slate’s lateral limit swelling ratio and the axial limit swelling stress under constant volume show obvious anisotropy,which are negatively correlated with the dip of structural plane.The pores of argillaceous slate after swelling are mainly small and medium pores;The microscopic basic unit of argillaceous slate is mainly composed of flake particles,and the part of the particles is massive particles. The orientation of spatial arrangement of particles is obvious. The contact mode between particles is mainly surfacesurface contact and they are stacked in tower shape. With the increase of dip of structural plane,the number of pores,pore area and surface porosity gradually decrease,and the edge of pores tends to be complicated. The threedimensional swelling constitutive model and meso expression of swelling stress of argillaceous slate with structural plane dip quantitatively characterize the anisotropic characteristics of swelling evolution of argillaceous slate in water-rich environment from macro-meso-micro scale. The research results can provide reference for the study of soft rock swelling mechanism and the treatment of soft rock swelling problem.