摘要
基质吸力是引起土体中水分迁移的驱动力,对探究土体中水盐迁移动态具有重要的意义。为研究由温度变化诱发的盐渍土孔隙溶液相变对土体基质吸力的影响,用pF meter测试了不同NaCl和Na_(2)SO_(4)比例的盐渍土在不同温度条件下的基质吸力。试验结果表明:在水盐相变发生前,盐渍土基质吸力随温度的降低呈线性增加;而当降温过程中有水盐相变发生时,土体基质吸力随温度的变化趋势会发生明显突变。NaCl和Na_(2)SO_(4)对土体水盐相变规律影响不同,使得含不同比例NaCl和Na_(2)SO_(4)的复合盐渍土基质吸力呈现较大的区别。2%NaCl+4%Na_(2)SO_(4)的盐渍土在19和-9℃附近发生盐结晶相变和二次相变,而4%NaCl+2%Na_(2)SO_(4)的盐渍土两次相变分别发生在11和-16℃附近。水盐相变导致土体液态含水率明显降低,进而引起复合盐渍土基质吸力在两个相变阶段均有明显增加。NaCl抑制土体中液态水发生冰水相变,Na_(2)SO_(4)容易在正温结晶,故Na_(2)SO_(4)主要影响土体正温时的盐结晶规律,NaCl则主要影响土体在负温条件下的冰晶产生规律;二者比例不同造成土体盐结晶温度和二次相变温度有明显差异,使得复合盐渍土的水盐相变规律更加复杂,其基质吸力随温度的变化更加难以预测。此外,该研究进一步探究了冰、盐结晶量对基质吸力变化的贡献,为深入理解盐渍土的相变过程和基质吸力之间的关系提供了有效参考。
The matric suction of saline soil is the driving force that causes water migration,and it is of great significance for exploring the mechanism of water and salt migration in saline frozen soil.In order to investigate the effect of phase transition of soil pore solution induced by temperature on the matric suction of saline soil,the matric suction of different types of saline soils was measured by pF meter under different temperature conditions.The natural soil was first washed to obtain the desalinized soil,then different salt mass ratios of sodium chloride and sodium sulfate(0:6,4:2,2:4,6:0)were added into the desalinized soil to model the composite saline soil,the salt content and water content were set to 6%and 20%,respectively.Subsequently,the remolded saline soil was compacted into the test chamber(0.37 m×0.25 m×0.22 m),and its dry density was controlled at 1.6 g/cm^(3).Hydra Probe II and pF meter were embedded at 11cm of the sample to measure the liquid water content and matric suction versus temperature.Freezing-thawing box(TMS 9018-R30),produced by Zhejiang Tomos company,was employed to control the experimental temperature by step cooling method.The temperature range was from 30 to-24℃,and the temperature interval was 3℃.The data was collected by CR300 at an interval of 6 h.When the experiment was complete,the temperature effect of saline soil matric suction was analyzed and the effect of water/salt phase transition was explored.The experimental results reveal that the matric suction of saline soil increases almost linearly with the decrease of temperature when no phase transition occurs,which is caused by surface tension and wetting coefficient.Different types of saline soils have different effects on the phase transition process of pore solution,resulting in significant differences in the matric suction of different types of saline soils.The mirabilite crystallizes at 19℃ and the second phase transition occurs at-9℃ for the composite saline soil with 2%NaCl+4%Na_(2)SO_(4),and the phase transit
作者
肖泽岸
段杰云
李康良
王启航
郭茂亮
XIAO Ze'an;DUAN Jieyun;LI Kangliang;WANG Qihang;GUO Maoliang(College of Civil Engineering,Taiyuan University of Technology,Taiyuan,030024,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2024年第15期287-292,共6页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(42271137)。
关键词
盐渍土
基质吸力
水盐相变
液态含水率
温度效应
saline soil
matric suction
water/salt phase transition
liquid water content
temperature effect
