Implications of physical and chemical changes in volcanic ash soils related to road construction

Abstract

Soils derived from weathered pyroclastic material in a humid tropical environment, known as volcanic ash soils, cover a low portion of the Earth’s surface. However, its unique characteristics, such as high porosity, low unit weight, high water content, and susceptibility to change in properties by drying and remolding, justify its study due to the impact of these characteristics in the construction of embankments and road subgrades, particularly on the compaction characteristics. The urban settlements located in the tropical zone, close to areas of volcanic activity, develop their road infrastructure on this type of soil. Under laboratory conditions, these soils’ chemical and physical changes, particularly on the particle arrangement or fabric, create a gap between their expected and actual behavior at the construction site. This article presents some problems in road construction related to these unique features and how to deal with them on the construction site, applying conventional classification and compaction tests in the lab and construction site. The particularities of the soils in these conditions are explained using unconventional tests to assess the microscopic effects of compaction on the soil fabric.