Physical and mechanical characteristics of pyroclastic soil for the construction of embankments

Abstract

In the framework of wider research activity on the physical and mechanical behaviour of volcanic soils, this paper reports the results of some laboratory tests on this type of geomaterial. The background of this research is the need for a construction company to possibly use pyroclastic material excavated along a tunnel profile to build railway embankments included in the design of a new High-Speed Train Line near the city of Naples, Italy. However, according to the standards of the National Italian Railways Company, pyroclastic soils cannot be employed as construction materials unless they are supported by a specific testing program demonstrating their good performance. The pyroclastic soil, which is widespread in the project area, is the product of Mt. Vesuvius volcanic activity. It is a coarse-graded soil that includes a significant percentage of non-plastic fines. They should be placed under compact conditions. The experimental campaign was aimed at identifying some physical characteristics that can synthesize the homogeneity of the pyroclastic deposit in terms of shearing resistance. The preliminary results obtained in terms of grading curves, modified Proctor compaction curves, and stress-strain curves from conventional drained triaxial tests are presented and discussed in this paper. The latter were executed on fully saturated specimens after compacting the soil at the optimum water content and on the dry and wet sides of the Proctor curve. The overall initial outcomes of the experimental campaign indicated that this material has acceptable characteristics and is suitable for the construction of railway embankments.