黏土岩各向异性轴向延伸试验

Experiment of Anisotropic Axial Extension of Clay Rock

黏土岩具有极低的渗透性、裂缝的自密闭潜力及高吸附性的等优点,被运用于核废料封存主基岩。为了研究层理面对黏土岩的峰值强度、破环模式及弹性模量的影响,针对各向异性的黏土岩,通过实施一系列不同层理角度试样的轴向延伸循环加卸载试验。轴向延伸试验是在恒定的平均应力下同时增加径向应力和减少轴向应力来完成。试验结果表明,黏土岩轴向峰值强度与层理面有关。在与层理平行和垂直的方向达到最大,而在钻样取芯与层理方向的夹角θ=45°方向表现最低,不同层理分布试样的强度曲线呈U形。不同角度的岩石破环准则能较好地描述黏土岩轴向峰值强度特征。黏土岩破坏模式也因层理面而异,试样破坏主要以拉伸断裂为主,而在θ=45°方向表现压缩破坏。弹性模量在不同的层理角度表现出较大差异性,垂直和平行于层理方向的弹性模量数值明显大于其他方向。

Clay rocks have the advantages of extremely low permeability,self-sealing potential of fractures,and high sorption capacity,and are thus chosen as a potential geological barrier for underground disposal of radioactive waste.In order to study the influence of bedding plane on the peak strength,failure mode and elastic modulus of clay rocks,a series of axial extension(AE)cyclic loading and unloading tests were carried out for specimens with different bedding angles.The AE test was performed by increasing the radial stress and decreasing the axial stress at the same time under constant mean stress.The experimental results show that the peak axial strength of clay rocks is related to the bedding plane.The peak strength of clay rocks reaches the maximum in the direction parallel to and perpendicular to bedding,and the lowest in the direction the angle between drilling core and bedding directionθ=45°.The strength curves of specimen with different bedding angles show U shape.The characteristics of the axial peak strength of clay rock can be described well by the rock breaking criteria at different angles.The failure pattern of clay rock also varies with bedding plane,the samples are mainly tensile fracture,while the compressive failure occurs atθ=45°.The elastic modulus shows great difference in different bedding angles,and the parallel and vertical directions of bedding are obviously larger than other directions.