酸性冻融循环条件下砂岩力学特性及损伤研究

Study on Mechanical Properties and Damage of Sandstone under Acidic Conditions and Freeze-thaw Cycles

为研究水化学—冻融循环耦合作用下的砂岩力学特性变化及损伤劣化规律,通过水化学溶液浸泡和冻融循环作用获得不同损伤程度的砂岩试样,进行单轴压缩试验,分析其力学特性,并通过SEM扫描电镜从微细观角度讨论了砂岩损伤劣化机理。研究结果表明:①随着冻融循环次数增加,砂岩在酸性溶液下的纵波波速衰减程度与质量损失率较中性溶液下更大,且酸性溶液pH值越低响应幅度越大;②峰值应力与冻融循环次数呈负相关,与浸泡溶液pH值呈正相关,砂岩呈现出由脆性向延性转化的趋势;③从微细观结构角度分析得出砂岩损伤劣化是交替进行并不断积累的;④以弹性模量定义砂岩损伤变量,拟合建立了损伤变量规律函数模型,表明浸泡溶液pH值越低、冻融循环次数越高的砂岩损伤劣化程度越大。研究成果可为受酸侵蚀环境下寒区工程建设、矿山地下开采提供参考。

In order to study the change of sandstone mechanical properties and the law of damage and deterioration under the action of hydrochemistry-freeze-thaw cycles,sandstone samples with different damage degrees were obtained by immersion in hydrochemical solution and freeze-thaw cycles,and then uniaxial compression experiments were carried out to discuss their mechanical properties,the damage and deterioration mechanism of sandstone was analyzed from a microscopic point of view by scanning electron microscope.The study results show that:①With the increase of freeze-thaw cycles,the longitudinal wave velocity attenuation and mass loss rate of sandstone in acidic solution are greater than those in neutral solution,and the lower the pH value of acidic solution is,the greater the response range is.②The peak stress is negatively correlated with the number of freeze-thaw cycles,and positively correlated with the pH value of soaking solution.The sandstone presents a tendency of transformation from brittleness to ductility.③From the perspective of microscopic structure analysis,it is concluded that the damage and deterioration of sandstone is alternately and continuously accumulated.④The elastic modulus was used to define the damage variable of sandstone,and the law function model of the damage variable was established by fitting,which showed that the lower the pH value of soaking solution,the higher the number of freeze-thaw cycles,the greater the damage deterioration degree of sandstone.The study results can provide references for engineering construction in cold areas and underground mining in the acid-eroded environment.