海水腐蚀对砂岩物理力学特性与微观结构破坏特征的影响研究

Experimental study on the influence of seawater corrosion on the physical and mechanical properties and microstructural failure behavior of sandstone

针对海底隧道围岩在海水腐蚀下物理力学性能劣化的问题,选取典型砂岩作为研究对象,基于深圳海底隧道所在区域海水的取样数据配制不同浓度的模拟海水溶液,对砂岩试样进行不同浓度、不同时间的腐蚀浸泡处理,再进行单轴压缩试验,并结合声发射与扫描电子显微镜(SEM)技术,对海水腐蚀损伤砂岩的物理力学特性、破坏过程和微观结构演化特征进行分析研究。结果表明:随着腐蚀溶液浓度增加,砂岩试样表面越早发生脱落且面积越大,试样密度小幅度增加;峰值应力和弹性模量均随腐蚀时间增加而降低,但二者降低幅度及速率不同;随着腐蚀时间以及浓度的增加,除高浓度组砂岩试样在腐蚀45 d之后声发射事件活跃期有所缩短外,其余组砂岩试样的声发射事件活跃期均有所增长,砂岩试样内部缺陷逐渐发育,结构逐渐疏松,蜂窝状腐蚀区域面积增大,盐离子白色结晶区域逐渐扩大。

In this study,experimental tests were conducted on sandstone specimens to study the influence of seawater corrosion on their physical and mechanical properties as well as failure behavior.Different concentrations of simulated seawater solutions were prepared based on seawater sampling data from the vicinity of the Shenzhen cross-harbor tunnel.Sandstone specimens were first treated with corrosion immersion in these solutions for different times before they were subjected to uniaxial compression tests.The acoustic emission and scanning electron microscope(SEM)techniques were employed to investigate damage and microstructural evolutions of the corroded sandstone.The results show that as the concentration of corrosive solution increases,the surface of sandstone specimens peel off earlier,the area is larger,and there is a slight increase in specimen density.The peak stress and elastic modulus both decrease with increasing corrosion time,but the magnitude and rate of decrease are different.With the increase of corrosion time and concentration,the active period of acoustic emission events increased in all sandstone specimens,except for the ones in the high concentration group,where the active period of acoustic emission events was shortened after 45 d of corrosion.SEM results show that with increase of corrosion time and concentration,the internal microdefects in the sandstone specimens progressively developed,and the microstructures gradually loosened.Furthermore,the area of honeycomb corrosion area increased in size and the area of white crystallization of salt ions gradually expanded.