冻融干湿循环下硫酸盐渍土的微观孔隙研究  

Study of Microscopic Pores in Sulfate Saline Soils under Freeze-Thaw-Dry-Wet Cycles

作　　者：张卫兵[1,2] 李晓 雷过 刘臻祥 周鑫磊 Zhang Weibing;Li Xiao;Lei Guo;Liu Zhenxiang;Zhou Xinlei(College of Civil and Hydraulic Engineering,Ningxia University,Yinchuan 750021,P.R.China;Ministry of Education Engineering Research Center of Efficient Use of Water Resources in Arid Modern Agriculture,Yinchuan 750021,P.R.China)

机构地区：[1]宁夏大学土木与水利工程学院,银川750021 [2]旱区现代农业水资源高效利用教育部工程研究中心,银川750021

出　　处：《地下空间与工程学报》2023年第2期465-473,共9页Chinese Journal of Underground Space and Engineering

基　　金：宁夏自然科学基金项目(2021AAC03067);宁夏高等学校一流学科建设项目(NXYLXK2021A03);宁夏大学创新试验项目(S202210749102)。

摘　　要：为研究冻融干湿循环对宁夏地区硫酸盐渍土微观孔隙结构的影响,在6次冻融干湿循环后,对试样进行SEM和MIP试验,借助ImageJ2X图像处理技术,从表观孔隙率、孔隙分布和孔隙分形维数3个角度分析其微观孔隙结构。结果表明:(1)经历6次冻融干湿循环后,含盐量较低(S≤1%)时,不同压实度下硫酸盐渍土的表观孔隙率随含盐量的增加均呈现先增大后减小的变化趋势,并在0.5%时达到峰值,1%时处于低谷;含盐量大于1%时,低压实度(K<95%)土体表观孔隙率随含盐量增加持续增大,而高压实度(K≥95%)土体则呈现先小幅增大后减小的变化趋势;(2)相较于未经冻融干湿循环的情况,土体最终表观孔隙率均有所增大。为提高工程的耐久性,建议硫酸盐渍土地基的压实度宜大于等于95%。(3)随含盐量的增加,孔隙孔径的变化主要集中在3~40 um区间内,孔隙分布的变化也主要体现在大孔隙、中孔隙上,且表观孔隙率与大孔隙体积百分含量变化基本一致;(4)基于MIP数据拟合得到土体孔隙分形维数随含盐量的增加呈上下波动,且其与表观孔隙率、大孔隙体积百分含量变化趋势相反。本研究有助于丰富硫酸盐渍土的微观理论,为硫酸盐渍土地区的工程建设提供理论支撑。In order to study the effect of freeze-thaw-dry-wet cycles on the microscopic pore structure of sulphate saline soil in Ningxia,SEM and MIP tests were carried out on the samples after six freeze-thaw-dry-wet cycles.With the help of ImageJ2X image processing technology,the microscopic pore structure was analyzed from the apparent porosity,pore distribution and pore fractal dimension.The results show that:(1)After six freezethaw cycles and dry-wet cycles,for lower salt content(S≤1%),the apparent porosity of sulfate saline soil increased first and then decreased with the increase of salt content under different compaction degrees,and reached the peak at 0.5%,and was at the trough at 1%.When the salt content is higher 1%,the apparent porosity of the lower compaction soil(K<95%)continued to increase with the increasing of salt content,while the higher compaction soil(K≥95%)showed a change trend of slightly increasing first and then decreasing.Compared with the unfreeze-thaw-dry-wet cycle,the final apparent porosity has increased.In order to improve the durability of the project construction,it is recommended that the compaction degree of sulphate saline soil foundation should not be less than 95%.(2)With the increase of salt content,the change of pore size is mainly concentrated in the range of 3~40 um,and the changes in pore distribution are mainly reflected in large pores and medium pores,and the apparent porosity is basically consistent with the change of the percentage content of large pore volume.(3)Based on MIP data,the fractal dimension of soil pores fluctuates up and down with the increase of salt content,and it is contrary to the change trend of apparent porosity and macropore volume percentage.This study is helpful to enrich the microscopic theory of sulfate saline soil and provide theoretical support for the construction of projects in sulfate saline soil areas.

关 键 词：硫酸盐渍土 冻融干湿循环 电镜扫描 压汞试验 微观孔隙结构 

分 类 号：TU448[建筑科学—岩土工程]