冻融砂岩细观损伤演化的各向异性分析

Anisotropy Analysis on Mesoscopic Damage Evolution of Freeze-Thaw Sandstones

针对陕西红砂岩开展冻融循环、力学特性及CT扫描试验,对冻融砂岩的孔隙形貌及各向异性特征进行了表征,明确了砂岩细观结构的演化规律。结果表明:砂岩强度在冻融作用下劣化,冻融40次后砂岩抗压强度损失21.99%;随着冻融循环的进行,似球状、柱状、树杈状孔隙向复杂网状孔隙转化,40次冻融循环后网状孔隙率贡献比由13.4%增长至97.6%;未冻融时砂岩各向异性值为1.06,可视为各向同性体,受孔隙联通性及重力影响孔隙优先横向发育,砂岩的各向异性特征呈先增后减态势;冻融砂岩的孔隙演化可分为“横向缓慢生长—横向快速生长—稳定发育”3个阶段。研究成果可为准确认识寒区岩石破坏机理提供参考。

Freeze-thaw cycles, mechanical properties and CT scanning tests were carried out on a red sandstone in Shaanxi. The pore morphology and anisotropy characteristics of freeze-thaw treated sandstone were characterized, and the evolution law of sandstone microstructure was clarified. The results are drawn as follows. Firstly, the strength of sandstone deteriorates under the freeze-thaw effect, and the compressive strength of sandstone decreases by 21.99% after 40 freeze-thaw cycles. Secondly, with the transformation of spherical, columnar and branch-like pores into complex network pores during the freeze-thaw cycle, the contribution ratio of network porosity increases from 13.4% to 97.6% after 40 freeze-thaw cycles. Finally, the anisotropy value of sandstone before freeze-thaw is 1.06, which can be regarded as an isotropic body. Due to the connectivity of pores and the influence of gravity, pores preferentially develop laterally, and the anisotropy characteristics of sandstone show an increasing and then decreasing trend. The pore evolution of freeze-thaw sandstone can be divided into three stages, including slow lateral growth, rapid lateral growth, and stable development. The research results can provide a reference for accurately understanding the rock failure mechanism in cold regions.