考虑时间效应的黑色页岩遇水三向宏微观膨胀力模型研究

Study on time-dependent effect and three-dimensional macro-micro swelling pressure model of black shale under influence of water

为研究黑色页岩遇水膨胀特性,开展物理力学性质、X衍射(XRD)测试以及三向侧限膨胀力试验,进一步基于黑色页岩中亲水性黏土矿物晶层膨胀与双电层理论及宏观物理力学性质,考虑页岩各向异性特征,提出考虑时间效应的分段式黑色页岩三向宏微观膨胀力本构模型,能较完备描述黑色页岩膨胀力发展过程。研究结果表明:黑色页岩遇水膨胀力发展过程服从幂指数关系,在遇水0~2 d内,膨胀力增长迅速,达到最大值70%,膨胀力遵循晶层膨胀关系;当遇水时间2~8 d,膨胀力增长20%,以黏粒扩散双电层膨胀为主;当遇水时间达到8 d后,膨胀力达到最大膨胀力的95%以上,膨胀过程基本达到稳定。同时,膨胀力发展表现出较强的各向异性,层理面法线方向(z方向)膨胀力最大,平行于层理面方向(x,y方向)的膨胀力分别约为法线方向的0.31,0.29倍。研究成果可为黑色页岩地区工程建设中的膨胀问题提供理论参考。

In order to study the swelling characteristics of black shale under influence of water,physical and mechanical properties,X-ray diffraction(XRD)and three-dimensional confined swelling pressure tests were carried out.Based on the theory of crystalline swelling and double layer theory for clay minerals in black shale,considering the anisotropic characteristics of shale,a time-dependent,segmented,and three-dimensional macro-micro swelling pressure constitutive model considering time effect was proposed,which can describe the development process of swelling force of black shale.The research results show that the development process of the swelling pressure for black shale in contact with water obeys the power exponent relationship.Within 0~2 days of contact with water,the swelling pressure follows the crystalline swelling relationship and reaches a maximum of 70%;when the time of contact with water is 2~8 d,the swelling pressure changes mainly because of the increase of the clay diffusion electric double layer and increases by 20%.When the time of exposure to water reaches 8 days,the swelling pressure reaches over 95%of the maximum value,and the swelling process is basically stable.Meanwhile,the swelling pressure shows strong anisotropy.The swelling pressure is the largest in the normal direction of the bedding plane(z direction),and the swelling pressure paralleled to the direction of the bedding plane(x,y direction)is about 0.32,0.29 times the normal direction,respectively.The research results can provide a theoretical reference for the swelling problem in engineering construction in the area of black shale.