Laboratory experiments on HMC coupling mechanisms in innovative clean foundation treatments for Zn-contaminated dredger fills

Jianxiu Wang; Linbo Wu; Tianliang Yang; Xuexin Yan; Xiangjun Pei; Xinlei Huang; Guanhong Long; Rui Xue

doi:10.1016/j.scitotenv.2019.134939

Laboratory experiments on HMC coupling mechanisms in innovative clean foundation treatments for Zn-contaminated dredger fills

Sci Total Environ. 2020 Feb 1:702:134939. doi: 10.1016/j.scitotenv.2019.134939. Epub 2019 Nov 2.

Authors

Jianxiu Wang¹, Linbo Wu², Tianliang Yang³, Xuexin Yan³, Xiangjun Pei⁴, Xinlei Huang³, Guanhong Long⁵, Rui Xue⁵

Affiliations

¹ College of Civil Engineering, Tongji University, Shanghai 200092, China; Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China. Electronic address: wang_jianxiu@163.com.
² College of Civil Engineering, Tongji University, Shanghai 200092, China; Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China. Electronic address: 26linbowu@tongji.edu.cn.
³ Key Laboratory of Land Subsidence Monitoring and Prevention, Ministry of Land and Resources, Shanghai 201204, China; Shanghai Institute of Geological Survey, Shanghai 200072, China.
⁴ State Key Laboratory of Geohazard Prevention and Geo-environmental Protection, Chengdu University of Technology, Chengdu 610059, China. Electronic address: peixj0119@tom.com.
⁵ College of Civil Engineering, Tongji University, Shanghai 200092, China.

PMID: 31733561
DOI: 10.1016/j.scitotenv.2019.134939

Abstract

Large-scale contaminated dredger fills have comprehensively resulted from human activities and geological deposition processes, and their disposal is a worldwide challenge. Innovative soil remediation coupling foundation treatment methods, namely, clean foundation treatment methods (CFTMs), were proposed and verified using a hydraulic-mechanical-chemical coupling triaxial testing system. The CFTM exploration triaxial tests on undisturbed clayey, silty, and sandy dredger fills showed that the critical injection significantly dilated soil volume even after the soil was vacuum pumped. Critical injection-vacuum soil flushing (CIVF), critical injection soil flushing (CIF), and vacuum soil flushing (VF) were proposed to perform clean foundation treatment for clayey silt, sandy silt, and silty sand of 1900-2300 ppm Zn. EDDS, HCl + CaCl₂, and HCl were selected as the three chelating agents. Orthogonal tests on three factors (CFTM, soil type, and eluent) showed that CIF with 5:1 EDDS aq. of pH 3.8 was the best CFTM scheme for the three soil types at a depth of 2.5-10 m. CIF with HCl aq. of pH 3.8 also reached a high comprehensive clean foundation treatment efficiency for silty sand at a depth of 2.5 m. The deep depth and heterogeneous texture resulted in low Zn contamination extraction efficiency.

Keywords: Clean foundation treatment; Dredger fill; EDDS; HMC coupling laboratory experiment; Zn contamination.