Mechanical properties of reaction mediums in permeable reactive barriers

Fangmin Yan; Zijun Ye; Benyi Cao; Fei Wang

doi:10.1016/j.scitotenv.2024.171868

Mechanical properties of reaction mediums in permeable reactive barriers

Sci Total Environ. 2024 May 20:926:171868. doi: 10.1016/j.scitotenv.2024.171868. Epub 2024 Mar 21.

Authors

Fangmin Yan¹, Zijun Ye², Benyi Cao³, Fei Wang⁴

Affiliations

¹ Institute of Geotechnical Engineering, School of Transportation, Southeast University, Nanjing 210096, China. Electronic address: 230218908@seu.edu.cn.
² Institute of Geotechnical Engineering, School of Transportation, Southeast University, Nanjing 210096, China. Electronic address: 2489495536@qq.com.
³ School of Sustainability, Civil and Environmental Engineering, University of Surrey, Guildford, Surrey GU2 7XH, UK. Electronic address: b.cao@surrey.ac.uk.
⁴ Institute of Geotechnical Engineering, School of Transportation, Southeast University, Nanjing 210096, China. Electronic address: feiwang@seu.edu.cn.

PMID: 38521278
DOI: 10.1016/j.scitotenv.2024.171868

Abstract

The mechanical properties of reaction media in permeable reactive barriers (PRB) is vital in geoenvironmental applications. Bentonite, activated carbon and zeolite, recognized for their excellent adsorption capabilities, are employed as the main reaction media in PRB for the treatment of contaminated underground water. The compaction test and the undrained and unconsolidated triaxial test were carried out to investigate the compression and shear strength of the activated carbon-zeolite mixture and activated carbon-bentonite mixture at various composition ratios. The impact of compaction degree on samples' shear strength was analyzed. The influence of different composition ratios on the mechanical properties and the permeability of each reaction medium were also evaluated. The results show that the mechanical performance of most activated carbon-zeolite (AZs) is not satisfactory compared to natural soil and activated carbon-bentonite mixtures. Activated carbon‑sodium bentonite (ANBs) and activated carbon‑calcium bentonite (ACBs) present similar compaction characteristics and shear properties. In ANBs and ACBs, the cohesion of mixes with a mass ratio of 1:2 (ANB2 and ACB2) was found lower than that of mixes with mass ratios of 1:1 (ANB1 and ACB1) and 1:3 (ANB3 and ACB3). And in most ANB and ACB mixes, 100 % compaction produced higher moisture content and higher friction angle, but lower cohesion, compared to 92 % compaction degree. And the shear strength behavior of ANBs is dominated by both bentonite and activated carbon. The permeability of ACB1, AZ3 and ACB1-sand are at 1.31 × 10^-6 m/s, 1.37 × 10^-6 m/s and 7.72 × 10^-7 m/s, respectively. These results provide valuable insights into the selection and optimization of reaction media for PRBs in geoenvironmental engineering applications.

Keywords: Compaction; Permeability; Permeable reaction barrier; Shear strength.