Basic properties of non welded basaltic lapilli and influence on their geotechnical behaviour

Abstract

In the Canary Islands there are hundreds of volcanic cones and extensive blankets of lapilli and civil works are very frequently undertaken in areas containing this material. Furthermore, basic lapilli (of basaltic, basanitic, or tephritic composition) are common in many volcanic regions of the world. They are small pyroclastic fragments (2 to 64 mm in diameter) emitted by Strombolian-type eruptions, very irregular in shape and with many open and closed voids. As a whole it is a light and quite loose granular material. The article covers two related aspects: (1) basic properties, such as texture, unit weight and geochemical composition; and (2) geotechnical parameters and behaviour under different situations: on slopes, under foundations and as granular layer for roads. We conclude that, resulting from their low density, high porosity and angular shape, lapilli particles have a quite different geomechanical response from other granular natural materials.