Reproduction of Array Observation Records by Means of Centrifuge Shaking Table Model

This paper shows the effects of the degree of consolidation of the soft clay layer on the strong motion response. Seismic behavior of the Kobe artificial islands during the 1995 Hyogo-ken Nambu earthquake is studied by using centrifuge shaking table test. At the earthquake, it is known that the liquefaction damage of artificial island was different from each other. Authors consider the reason why is due to the degree of consolidation of clay layer underlying the reclaimed ground. The model grounds used for the centrifuge test are made by the clay and fill material sampled from Kobe artificial island, and each clay layer of models is consolidated as the same degree as the sites. First, from the viewpoint of the reproducibility of in-situ behavior, the seismic response and the ground settlement are compared with observation data. Next, we compare the seismic response of the test results of the different degree of consolidation. It is found that the degree of consolidation and the shear strength of the clay layer significantly affect the ground behavior. The large damage is not always come to being on the ground with soft clay layer

Geotechnical hazards from large earthquakes and heavy rainfalls

This book is a collection of papers presented at the International Workshop on Geotechnical Natural Hazards held July 12–15, 2014, in Kitakyushu, Japan. The workshop was the sixth in the series of Japan–Taiwan Joint Workshops on Geotechnical Hazards from Large Earthquakes and Heavy Rainfalls, held under the auspices of the Asian Technical Committee No. 3 on Geotechnology for Natural Hazards of the International Society for Soil Mechanics and Geotechnical Engineering. It was co-organized by the Japanese Geotechnical Society and the Taiwanese Geotechnical Society. The contents of this book focus on geotechnical and natural hazard-related issues in Asia such as earthquakes, tsunami, rainfall-induced debris flows, slope failures, and landslides. The book contains the latest information and mitigation technology on earthquake- and rainfall-induced geotechnical natural hazards. By dissemination of the latest state-of-the-art research in the area, the information contained in this book will help researchers, designers, consultants, government officials, and academicians involved in the mitigation of natural hazards. The findings and other information provided here is expected to contribute toward the development of a new chapter in disaster prevention and mitigation of geotechnical structures

Effect of 3D water table profile of horizontal drains on slope stability and idealization of 3D-FEM flow modeling to 2D-FEM flow modeling

Horizontal drains (HDs) are commonly used in the groundwater regime management of landslides. The groundwater table (GWT) profile of slopes with HDs have a complicated formation in three-dimensional (3D) space, requiring 3D analyses to obtain accurate results. However, owing to the complexity of 3D simulations, idealized two-dimensional (2D) cross sections are widely used in numerical simulations of such slopes. Unfortunately, stabilities are overestimated by 2D simulations because the 3D variation of the GWT is neglected. Finite element analysis is performed in this study to evaluate the effect of 3D variation of the GWT on the stability of slopes with HDs and to evaluate the effectiveness of 2D idealizations. The results demonstrate that idealized 2D analyses neglect the high pore water pressures between HDs, thereby overestimating the slope stability, especially with high rainfall intensities and large drain spacings. Alternatively, accurate results can be obtained in 2D analyses by manually estimating an average GWT profile using the Crenshaw and Santi method for steady-state conditions. Each method has its own limitations and, therefore, the selection of an appropriate method should be made based on the specific conditions and requirements of the problem

エンシン サイカ モケイ シンドウ ジッケン シュホウ オ モチイタ ジバン ノ ジシン オウトウ トクセイ ニ カンスル ケンキュウ

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Case study on viability of using head-separated micropiles as foundation system for check dams

Check dams constructed in steep mountainous areas require the rationalization of the dam body and foundation system. In general, soil cement replacement or caissons are often adopted for foundations. In such cases, reducing the construction effort is a critical issue. To address this, the authors studied the viability of a new type of check dam foundation consisting of a group of micropiles whose heads are structurally disconnected from the dam body. The system, coined a head-separated micropile group (HMG) foundation, enables the saving of labor and a reduction in the cross-sectional forces applied to the micropiles. Firstly, a full-scale loading test of the HMG was conducted. Then, a finite element model was formulated and its parameters fitted to make it suitable for reproducing the experimental results. Finally, using the FE model, the performance of a typical rigidly connected micropile foundation and that of the HMG system were compared in terms of the bearing capacity and displacement of the check dam body. The results confirmed that, although its displacement was 1.25 times larger than that of the rigidly connected foundation, the HMG system led to a factor of safety of 3.5 against micropile buckling