盐冻耦合侵蚀作用下寒旱地区渡槽劣化机制

Mechanism of aqueducts in cold and dry areas under effect of salt-frozen coupling erosion

为探究西北盐渍寒旱地区渡槽的服役性能,首先,运用顺序耦合热应力分析方式对渡槽槽身进行冻融循环有限元模拟分析;然后,开展基准、加防冻剂和加早强减水剂3种类型的混凝土试件在4种质量浓度的Na2SO4溶液侵蚀下的冻融循环试验。结果表明:有限元模拟中,随着冻融循环次数的增加,渡槽槽身的应力应变值也相应增大,且集中在渡槽槽身受冻区的交界处;试验中,混凝土试件的质量损失率和抗压强度损失率随着盐冻次数增加而增大,且试件的破坏程度也均逐渐加剧;在同种质量浓度盐溶液侵蚀下,不同类型试件的破坏程度由大到小依次为添加防冻剂组、基准组、添加早强减水剂组。盐冻作用会导致渡槽槽身产生破坏,长此以往则会造成渡槽结构的强度与稳定性下滑,影响输水工程的使用寿命。

In order to explore service performance of aqueduct in saline cold and arid areas of Northwest China,firstly,finite element simulation analysis of freezing and thawing cycle of aqueduct body was carried out using sequential coupled thermal stress analysis method.Then,freeze-thaw cycle tests were conducted on 3 types of concrete specimens,including reference,antifreeze and early strengthening water reducer,under erosion of Na2SO4 solutions at 4 mass concentrations.The results show that in finite element simulation,as number of freeze-thaw cycles increases,stress and strain values of aqueduct body also increase correspondingly which are mainly concentrated at junction of frozen areas.It is found through tests that quality loss rate and compressive strength loss rate of concrete specimens increase with rise in number of salt freezing,and their damage also gradually intensifies.Under erosion of salt solution at same mass concentration,damage degree of specimen ranks in descending order as antifreeze,reference and early strengthening water reducing agent group.Moreover,salt freezing will cause damage to aqueduct body,and in a long run,it will lead to decline of strength and stability of its structure,therefore affecting service life of water delivery project.