硫酸锌胶结珊瑚砂渗透特性试验及工程应用探讨

Permeability test of zinc sulfate bonded coral sand and discussion on its engineering application

对松散珊瑚砂进行胶结处理以降低岛礁地层渗透性是促进生态岛淡水涵养的重要手段之一。为此,开展了硫酸锌胶结珊瑚砂的渗透试验,分析了不同浸泡时长、硫酸锌溶液浓度及初始干密度对胶结珊瑚砂渗透性的影响,采用干湿循环试验验证其耐久性,通过X射线衍射(X-ray diffraction,简称XRD)、扫描电镜(scanning electron microscope,简称SEM)、能量色散X射线光谱(energy dispersive spectrometer,简称EDS)及计算机断层扫描(computed tomography,简称CT)扫描研究微观胶结机制。结果表明:(1)硫酸锌胶结可将珊瑚砂渗透系数降低70.17%~95.79%;(2)干湿循环16次后,胶结处理36 h的珊瑚砂样品质量损失率不超过4%,渗透系数变化不超过1.0×10^(-3)cm/s,表明样品耐久性良好;(3)珊瑚砂和硫酸锌反应生成二水石膏与菱锌矿填充样品孔隙,使孔喉平均半径、配位数均减小,孔隙连通性显著下降。该技术可应用于岛礁吹填初期固砂防侵蚀、提高地基承载力、降低渗透性以促进地下淡水涵养和生态岛建设,具有重要的工程应用价值。

Cementing loose coral sand to reduce the permeability of island reef formations is one of the key approaches to enhancing freshwater retention in ecological islands.To this end,a permeability test was conducted on zinc sulfate-bonded coral sand,analyzing the effects of varying immersion durations,zinc sulfate solution concentrations,and initial dry densities on its permeability.The durability was verified through dry-wet cycling tests,while the microscopic cementation mechanism was investigated using XRD(X-ray diffraction),SEM(scanning electron microscope),EDS(energy dispersive spectrometer)and CT(computed tomography)scanning.The test results show that:(1)the permeability coefficient of coral sand is reduced by 70.17%to 95.79%after cementation with zinc sulfate.(2)After undergoing 16 dry-wet cycles and 36 hours of cementation,the mass loss rate of the cemented coral sand samples does not exceed 4%,and the variation of permeability coefficient is less than 1.0×10^(−3) cm/s,indicating excellent durability of the samples.(3)Additionally,the reaction between coral sand and zinc sulfate produces dihydrate gypsum and smithsonite,filling the pores of the samples,resulting in a decrease in the average pore-throat radius and coordination number,and a significant reduction in pore connectivity.This technology holds significant engineering application value,as it can be applied to sand fixation and erosion prevention in the initial stage of island reef reclamation,improving foundation bearing capacity and reducing permeability to promote groundwater conservation and eco-island construction.