水泥、石灰固化Zn²⁺污染土的力学特性及微观机制研究

Mechanical properties and microscopic mechanisms of Zn2+-contaminated soil stabilized by cement and lime

摘要

【目的】探究水泥与石灰对Zn²⁺污染红黏土固化效果。【方法】以桂林红黏土为研究对象，通过无侧限抗压强度试验、电导率测试、土柱淋滤试验及微观分析，系统研究不同水泥与石灰掺量对污染土的强度特性、导电行为、重金属迁移规律及微观结构的影响。【结果】结果表明，固化剂掺量的增加显著增强了固化效果，其中水泥6%与石灰6%的掺量为最佳比例，固化处理显著提高了Zn²⁺污染红黏土的无侧限抗压强度，且电阻率与应力-应变呈负相关性。土柱淋滤试验显示，在雨水作用下，Zn²⁺逐渐向下迁移，导致下部土层污染，浸出浓度随雨水量增加而升高。微观结构分析表明，Zn²⁺的固定主要源于水泥和石灰水化反应生成的C-S-H凝胶和Ca(OH)₂,这些产物填充土壤孔隙并与Zn²⁺形成稳定化合物，有效抑制重金属迁移。【结论】水泥与石灰可有效固定Zn²⁺,抑制离子迁移。在桂林地区重金属污染红黏土修复工程中推荐水泥6%+石灰6%配比。研究成果为重金属污染土治理提供了微观机理支撑与工艺参数优化依据。

Abstract

[Objective] The solidification effect of cement and lime on Zn²⁺ contaminated red clay was investigated. [Methods] Taking Guilin red clay as the research object, the effects of different cement and lime contents on the strength characteristics, conductive behavior, heavy metal migration law, and microstructure of contaminated soil were systematically studied through unconfined compressive strength test, conductivity test, soil column leaching test, and microscopic analysis. [Results] The results show that increased curing agent content significantly enhances the curing effect, and the optimum proportion is 6% of cement and 6% of lime. The curing treatment significantly improves the unconfined compressive strength of Zn²⁺ contaminated red clay, and the resistivity is negatively correlated with stress-strain. The soil column leaching test showed that Zn²⁺ gradually migrated downward under the action of rainwater, resulting in pollution of the lower soil layer. The leaching concentration increased with the increase in rainwater volume. The microstructure analysis showed that the immobilization of Zn²⁺ was mainly due to the C-S-H gel and Ca(OH)₂ generated by the hydration reaction of cement and lime. These products filled the soil pores and formed stable compounds with Zn²⁺, effectively inhibiting heavy metal migration. [Concluion] Cement and lime can effectively immobilize Zn²⁺ and inhibit ion migration. The recommended cement 6%+lime 6% ratio is applied in the remediation project of heavy metal-contaminated red clay in Guilin. The research result provide micro-mechanism support and process parameter optimization for the treatment of heavy metal-contaminated soil.

关键词

重金属污染 / 强度 / 水泥 / 石灰 / 红黏土 / 力学特性 / 微观结构

Key words

heavy metal pollution / strength / cement / lime / red clay / mechanical properties / microstructure

基金资助

国家自然科学基金项目“活性氧化镁-微生物协同固化重金属污染土宏微观特性演化规律及机理”(42262030)

“广西岩溶动力学重大科技创新基地开放课题“岩溶区重金属污染土离子迁移规律及固化修复机理”(KDL&Guangxi202303)

河南省科技研发计划联合基金“基于EICP 技术的河南省典型重金属污染土修复研究”(225200810005)

广西岩土力学与工程重点实验室开放课题“纤维-微生物协同固化钙质砂力学特性研究”(桂科岩2023-XT-02)