Internal Erosion in Volcanic Soils—Challenges for Infrastructure Projects in New Zealand

Abstract

Internal erosion is a well-documented process in the geotechnical literature. Whilst the process is typically associated with water-retaining structures, it can also occur in natural terrain. Internal erosion and sinkholes have historically posed significant challenges for infrastructure projects in New Zealand. This paper discusses some historical and recent examples of these challenges. Volcanic soils, in particular those associated with pyroclastic environments, such as the central segment of the Taupo Volcanic Zone in the North Island of New Zealand, are particularly prone to internal erosion. The potential risks arising from internal erosion should not be underestimated for projects in volcanic areas, in particular for projects involving water retaining structures and/or stormwater disposal by soakage. A robust design, supported by a detailed geotechnical investigation specifically targeted at identifying internal erosion potential is recommended to better manage these risks.