水化学作用下砂岩力学特性劣化试验研究

日益严重的环境污染加剧了水化学环境对工程岩体和露天石像的腐蚀作用,尤其是最为敏感的砂性岩体。研究长期水化学腐蚀作用下砂岩的宏观力学特性的劣化情况及微观作用机理对预防及评价水化学环境对砂岩腐蚀具有重要意义。采用三点弯曲、薄片鉴定、扫描电镜和能谱分析等测试方法对比研究了砂岩在不同pH、Na_2SO_4溶液浓度及浸泡时间后的力学特性和微观结构特征。试验结果表明:水化学作用对砂岩胶结质溶蚀劣化影响显著,酸性增强和作用时间增长会进一步加剧砂岩劣化,酸性减弱对砂岩试样的劣化有抑制作用;砂岩的腐蚀劣化宏观上表现为强度、模量和断裂韧度减小,脆性特征逐渐减弱,延性特征增加;在微观上除矿物成分的改变外,其颗粒大小及形状,孔隙、裂隙等微细观结构也发生明显改变。

Experimental study on mechanical properties degradation of sandstone under hydrochemical action

Serious environmental problems aggravate the corrosive effect of hydrochemical environment on engineering rock mass and outdoor sculpture, especially the most sensitive sandy rock mass. It is necessary to study the deterioration of macroscopic mechanical properties and microscopic mechanism of sandstone under long-term hydrochemical corrosion, which is of great significance to prevent and evaluate hydrochemical environment for sandstone corrosion. In this paper, the mechanical properties and microstructure of sandstone at different pH values, Na2SO4 solution concentration and soaking time were studied by means of three-point bending, microscopic section identification, scanning electron microscope and energy spectrum analysis. The results show that the hydrochemical action has a significant effect on the erosion or degradation of the cemented sandstone, and the increase of acidity and action time will further aggravate the degradation of the sandstone. On the macro level, the corrosion degradation of sandstone shows that the strength, modulus and fracture toughness decrease, the brittleness weakens gradually, while the ductility increases; On the micro level, except the change of mineral composition, the size and shape of particles, pores, fractures and other micro-structures also changed significantly.