centrifuge 1 - Centrifuge modeling of an excavation...

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1 Centrifuge modeling of an excavation stabilized with embedded improved soil berm Thanadol Kongsomboon Department of Civil Engineering, Srinakarinwiroj University, Rangsit-Nakornayok Rd, Nakornayok 26120, THAILAND thanadolk@yahoo.com Tan Thiam Soon, Yong Kwet Yew Department of Civil Engineering, National University of Singapore 10 Kent-ridge Crecent, Singapore 10680,SINGAPORE cvetants@nus.edu.sg , cveyky@nus.edu.sg Warakorn Maireing Department of Civil Engineering, Kasetsart University 50 Pahonyothin Rd, Bangkok 10900, THAILAND maireing@yahoo.com Abstract: The main aim of this paper is to introduce how a test on excavation stabilized with an embedded improved soil berm can be carried out in a centrifuge and to examine the results obtained. This type of soil improvement is usually carried out before the start of an excavation and the improvement is done below the final excavation level, hence the term, embedded. An in-flight excavator and an image processing system were used under 100g (gravities) environment during the tests. These two developments provide the key technologies to study in the centrifuge the correct mechanisms in a stabilised excavation. The centrifuge tests were conducted using kaolin clay and the tests were carried out at the National University of Singapore (NUS) geotechnical centrifuge. The experiments were performed to provide high quality data on the behaviour of the embedded berm, which could not be obtained in actual instru- mented field study. 1 GUIDELINES 1.1 Introduction Centrifuge testing concerns the study of geotechnical events us- ing small-scale models which are subjected to acceleration fields many times Earth’s gravity. In using this technique, self-weight stresses and gravity dependent processes are correctly modeled and thus observations from small-scale model experiments can be related to the full-scale prototype situation using well established scaling laws. This is extremely important as soil is a highly non- linear and history dependent material. A significant advantage in using a centrifuge model is that it provides good control over the way soil models are prepared. In this way, it provides a practical approach to determine the relative significance of certain soil pa- rameters to the overall behaviour. This is not possible with other forms of analyses, such as numerical analyses which depends on soil models used and the associated material properties chosen, construction sequence and, most importantly, uncertainties due to imperfect knowledge of the true soil profile and conditions. Thus data from centrifuge test provide a good compliment to careful instrumented field case studies and associated numerical analy- ses. Development of geotechnical centrifuge facilities and re- search projects since 1970 has been rapid and well documented ( Craig, 1984, Kimura et al., 1998 and Thanadol et al.,2000). Re- cently, a new image processing system was implemented in the NUS Geotechnical Centrifuge Laboratories. This image process- ing system fulfils the requirement of live capturing of the in- flight soil movement during a centrifuge model test.
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centrifuge 1 - Centrifuge modeling of an excavation...

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