Potassium chloride wells used as quick-clay landslide mitigation: installation procedures, cost–benefit analysis, and recommendations for design

Abstract

Retrogressive development of landslides in highly sensitive clays (quick clays) may extend several hundred metres upslope from an initial landslide, and liquified slide-debris may impact buildings or infrastructure in the run-out zone. By installing wells filled with potassium chloride (KCl) in quick clays, the salt migrates into the surrounding clay and increases its remolded shear strength, reducing its sensitivity. The salt-stabilized, nonquick clay volume may act as a barrier preventing backward retrogression, thereby contributing to reducing both the area susceptible for being involved in a quick-clay landslide, and the area of the run-out zone. Installation procedures and design guidelines for salt stabilization are examined herein. Installation procedures generating temporary, very small excess pore-water pressures were tested at National Geo-Test Site Tiller–Flotten. Although the benefit-to-cost ratios related to these procedures are small compared to conventional landslide mitigation measures, reducing the installation costs to less than 30 USD per m well and increasing the center distance between the wells may justify salt-stabilization as a landslide mitigation measure. This paper describes experience from testing safe installation procedures, evaluations of cost–benefit and environmental impact, and proposed design guidelines, introducing KCl as an alternative to conventional landslide mitigation-measures in slopes with highly sensitive quick-clay deposits.