Feasible method, utilizing density changes, for estimating in situ dynamic strength and deformation properties of sand samples

摘要

Laboratory tests and design reliability are directly controlled by sample quality. The frozen sampling (FS) method is useful for dynamic strength and deformation tests of undisturbed clean sand. However, it is very expensive and requires considerable equipment. The sample quality of Toyoura sands obtained from 48 mm and 75 mm samplers are scrutinized based on void ratio, dynamic strength and deformation properties through model and cyclic undrained triaxial tests. A conventional method for estimating in-situ dynamic strength and deformation properties of sand samples utilizing density changes is examined and the applicability of the proposed method is discussed for the samples obtained from Niigata sand deposits. The main conclusions obtained from this study are summarized as follows: (1) A conventional method for estimating in-situ void ratio (e_0), Dr, stress ratio (R_(L20))in a 20 cyclic time frame and the initial modulus of rigidity (G_o) of sand samples utilizing density changes is proposed. (2) The in-situ R_(L2o) and G_0 estimated from the proposed method for sand samples from tube samplers were similar to those of frozen sampling and the in-situ modulus of initial rigidity was calculated from the secondary wave velocity for Niigata sand deposits. Therefore, dynamic strength and deformation properties changes, caused by sampling, can be modified appropriately to an in-situ condition by this proposed method.