Development of KOCED geotechnical centrifuge and its shear wave velocity tomography testing system

Abstract

In geotechnical engineering, reduced scale physical modeling is often conducted within a large centrifuge in order to simulate correct scaling effect of self-weight stresses in soil material. Geotechnical centrifuge is useful for reduced scale modeling of geotechnical systems and the behavior of the model can be similar with full scale performance of the structures. The first large scale geotechnical centrifuge facility in Korea has been recently developed at KAIST under Korea Construction Engineering Development (KOCED) Collaboratory program and this dissertation presents detailed information of the centrifuge facility. A 5m platform radius, 240g-tons geotechnical centrifuge has been installed in a new facility. It has a unique feature of automatic balancing system and includes parts for general testing purpose such as fluid rotary joints, slip rings, fiber optic rotary joint and Ethernet network system. In this centrifuge, a four degree-of-freedom in-flight robot can be equipped to simulate complex testing construction or in-situ testing process during centrifuge flight. In order to simulate earthquake motion during operation, a self balancing type biaxial shaking table has been also developed. Since the KOCED program promotes collaboration and remote use, tele-presence and tele-participation environment has been implemented in this facility. It is important to evaluate soil properties in flight condition because of stress dependency of soil. Especially, measurement of shear wave velocity or shear modulus of soil can provide a key information for deformation analysis and a new testing system to evaluate shear wave velocity distribution in testing model has been developed in this study. To evaluate two-dimensional distribution of deformation characteristic of soil in centrifuge testing model, a testing system for shear wave velocity tomography within centrifuge testing model has been developed. A series of piezoelectric bender elements have been utilized a...