An analytical solution for contaminant extraction in a radial flow field using PVD-enhanced system

Abstract

Prefabricated vertical drains (PVDs) are a widely used in situ remediation technology for contaminated fine-grained soil. The current analytical solution that considers the infinite extraction boundary is not suitable for describing the short distance between the injection PVD (IPVD) and the extraction PVDs (EPVDs). The Dirichlet injection boundary proposed by the existing solution cannot meet the requirements for mass conservation. An analytical solution is developed based on the proposed simplified axisymmetric model. Vertical dispersion is considered in the model, and the initial concentration is exponentially distributed along the depth of the drain. The good agreement between the results obtained using the analytical solution and those obtained using the finite-element method validates the proposed solution and indicates that the simplified model can provide a simple and efficient solution to the prediction of the soil flushing process using a PVD-enhanced system. The model with the Dirichlet injection boundary can lead to significantly lower estimated flushing times for cleaning up a contaminant zone. The results show that the flux-type extraction boundary was better than the infinite extraction boundary. The dispersion can significantly affect soil flushing because the contaminant migrates from the highly contaminated zone to the low-contaminant-concentration zone.