Centrifuge modeling of seepage and pollutant migration of suspended cutoff walls in saturated soils

This study presents an investigation of seepage and pollutant migration in a site with suspended cutoff walls through centrifuge model tests with the advantages of reduced scale in time and size at 80 g, employing an independently designed control system. The experimental setup simulated and reproduced the long-term effects of site seepage and continuous non-point source pollution release under a hyper-gravity environment for the first time. It enables in situ and real-time monitoring of variations in pollutant concentration at the base of the downstream cutoff wall. The distribution of seepage and pollutant migration patterns in two types of suspended cutoff wall sites, namely shallow wall (12 m) and deep wall (24 m), was investigated by means of numerical simulations, with the goal of complementing and comparing to the testing data. Results indicate that the suspended cutoff wall prolongs the contaminated seepage path and delays the downstream wall's failure, extending its service life by causing diversion effects of the site and ongoing variations in seepage direction. Although the containment impact on pollutants is greatly improved by deeper walls, the efficiency does not rise in a linear fashion with depth. Numerical simulations were also used to assess and validate the dispersion pattern of the contaminated plume and consequences of site diversion. This study provides a valuable reference for the design of suspended vertical cutoff walls at contaminated sites.