Cohesive soils by means of shear wave velocity from Bender Element (BE) test under unconfined stress conditions. Results from this evaluation are compared with those using suction (residual effective stress (p'r)) and deformation modulus (E50) obtained from UC test. It is revealed that p'r, E50 and Vs (G) values are closely correlated with each other and G value is mainly governed by p' value, provided that change in void ratio is small.


Sample quality is a very important issue for obtaining reliable geotechnical parameters. Many researchers have tried to establish methods for evaluation of sample quality, in terms of, for example, strain at failure from the unconfined compression test, volume change caused by applying the in-situ effective overburden pressure (σ'v0) and so on. However, these traditional methods are mostly destructive tests: i.e., once these tests are performed, the sample cannot be used again. Instead of these tests, the shear wave velocity (Vs) from the Bender Element (BE) test has recently come to attention, because the test is relatively simple and time required for the Vs measurement is very short. In addition, the test is non-destructive so that the specimen after measuring Vs can be used for other mechanical tests to obtain geotechnical parameters. Authors have reported that Vs can be an index of sample disturbance (Nishida et al (2006)). However, geotechnical parameters of the Yuubari river clay layer tested in their research such as over consolidation ratio (OCR), grain composition vary drastically with depth. Therefore, these varieties may probably have influences on their tests results. In this study, relatively homogeneous clays are collected at the site of Mihara, Japan and UC tests as well as the above nondestructive tests are performed. This paper will examine a possibility in evaluating the sample disturbance, using Vs as well as the residual effective stress (suction (p'r)) and the deformation modulus (E50).

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