不同化学腐蚀下砂岩冻融力学特性劣化的试验研究

通过研究砂岩试样在酸性Na2SO4溶液、中性Na2SO4溶液和碱性NaOH溶液中浸泡并经历冻融作用后的物理力学特征，分析了砂岩在不同化学溶液中腐蚀30d后及再经历不同冻融循环次数作用后其物理力学特征的变化规律，同时，借助于体视显微镜和SEM扫描电镜对试样微细观结构的损伤劣化进行了观察，并基于孔隙率的变化建立损伤变量来定量的描述试样的损伤劣化程度。试验结果表明：随着冻融循环次数的增加，浸泡在不同化学溶液中砂岩试样的峰值强度及其弹性模量均呈现出指数函数的劣化趋势，而其峰值应变却按指数函数的趋势增加。不同化学溶液下砂岩试样的损伤程度随着冻融循环次数的增加而逐渐加剧，酸性溶液下试样的损伤程度大于中性溶液和碱性溶液下的损伤程度，碱性化学溶液下试样的冻融损伤程度最小。酸性溶液加剧了冻融作用下砂岩试样的损伤劣化程度，而中性至碱性溶液下起冻融损伤程度却得到一定的缓解。化学腐蚀作用与冻融循环作用相互促进、共同影响着砂岩试样的损伤劣化程度。

Laboratory investigations on the mechanical properties of sandstone in chemical corrosion under and freeze-thawing cycles

The physical and mechanical characteristics of sandstone specimens eroded in different chemical solutions （acidic Na2SO4 solution、neutral Na2SO4 solution and alkaline NaOH solution）and subjected to different freeze-thawing cycles is experimentally studied. The variation of physical and mechanical characteristics of sandstone specimens subjected to different chemical solutions for 30ds and then different freeze-thawing cycles is analyzed. Meanwhile the damage of microstructure of sandstone specimens is observed by means of stereo microscope and SEM scanning electron microscope. The damage variable based on the change of porosity was defined to analyze quantitatively damage degree of sandstone specimens. The test results show that for different chemical solutions，the peak strength and elastic modulus of sandstone specimens decrease by exponential function with the increase of freeze-thawing cycles，but its peak axial strain increases by exponential function with the increase of freeze-thawing cycles. With the increase of freeze-thawing cycles，the damage of sandstone specimens increased gradually soaked in different chemical solutions. The damage degree of sandstone specimens soaked in acidic chemical solution is bigger than that in neutral chemical solution and alkaline chemical solution，that is the smallest under alkaline NaOH solution. Acidic chemical solution intensified the damage and degradation degree of sandstone specimens under freeze-thawing cycles，but there has some mitigative effect on that of sandstone specimens soaked in neutral solution and alkaline solution. Chemical corrosion and together with freeze-thawing cycles can give mutual promotion and mutual influence on the degradation and damage of sandstone specimens.