Abstract
Engineering properties of local soil called ‘Polishing sand’ distributed over the southern district of Tsu-shi in Mie Prefecture was examined by performing laboratory tests. Polishing sand at natural state found as a sedimentary soft rock with average strength parameters of qu = 0.2 to 3.4MPa, ccu = 100 to 200 kPa,φcu
3 40 - 50 degrees, it transforms into a homogeneous grayish-white sand when exposed to the surface by excavation. Looking on the average strength parameters of the disintegrated sand, ccu = 10kPa, φcu = 360, a drop in qu to almost 1/10 or smaller level than that at natural state is observed. The difference in properties of these two states of the same material are considered to be due to cementation and crystallization effects between soil particles. When in a natural state, the anisotropy evaluated by triaxial tests with bender elements shows Ghh/Gvh = 1.4 - 1.5 at mean effective confining pressure, p'= 0 - 100kPa and Ghh/Gvh >>1.0 at 100 <p'£ 400kPa. This shows an anisotropic behavior at deposition because of cementation and its destructuration afterwards at higher confining pressure. Additionally, the relation between qu and G has been elaborated by comparing it with cement-treated soil and by discussing physical and chemical aspects of cementation.
