Shear strength characteristics of compacted soils generated from Tsunami deposit

Abstract

An enormous amount of disaster debris and tsunami deposits were generated by the 2011 Great East Japan Earthquake and Tsunami, and the soil fractions separated from them were required to utilize as geomaterials for disaster reconstruction. However, the utilization had difficulty because the soils contained wood chips that could not have been sufficiently removed in treatment process. In this study, for the purpose to assess applicability of the soils for general earthwork materials, sources of the wood chips in the soils sampled at disaster sites were classified and a series of laboratory tests were conducted to evaluate the influence of wood chip inclusion on compaction and shear strength characteristics. It was clearly seen from the compaction test results that the maximum dry density decreased and the optimal water content increased with the increase in wood chip content. From the results of large-scaled direct box shear tests conducted on the compacted soil specimens, it was seen in some soils that shear strength decreased and dilatancy reduced with increase in wood chip content. Regarding the soils having wood chip content with less than approximately 3 %, the general tendency was that the influence of wood chips on strength and deformation properties did not appear clearly and suggested that they could be used for general geomaterials.