Hideo Nagase

A Study On The Mechanism Of The Floatation Of Buried Pipes Due To Liquefaction

The 1993 Kushiro-Oki earthquake brought the floatation of many manholes and sewage pipes due to liquefaction in Japan. To study the mechanism of the floatation, several shaking table tests were carried out under several conditions of soil densities, specific gravities of pipes, water levels and diameters of pipes. Tests were also conducted on the model grounds in which a trench was excavated and then backfilled with loose sands. Test results show that the speed and the height of floatation are affected by soil density, the specific gravity of the pipe or manhole, water level, severity of liquefaction, and width and depth of the trench.

Effects of load irregularity on the cyclic behaviour of sand

Abstract In an effort to investigate the effects of irregular nature of load application on the behaviour of soils during earthquakes, a series of uni-directional irregular loading tests were performed on saturated Fuji river snad under undrained condition using a simple shear test apparatus. The samples prepared to three different densities in this test device were subjected to twelve irregular time histories of shear stress alteration. For comparison purposes, the conventional type of constant amplitude cyclic simple shear tests were also conducted on samples prepared under identical conditions. On the basis of the test results, values of coefficients allowing for the effect of load irregularity were elucidated for the samples with three different densities. It was then suggested that the values of coefficient thus determined be used to facilitate the evaluation of the soil strength under actual seismic loading conditions, on the basis of the cyclic shear strength obtained from the conventional type of constant-amplitude triaxial tests.

ZONING FOR LIQUEFACTION AND ACTUAL DAMAGE DURING THE 2005 FUKUOKAKEN-SEIHO-OKI EARTHQUAKE

On March 20, 2005, an earthquake of magnitude 7.0, which was named as the 2005 Fukuokaken-seiho-oki earthquake, occurred at the northwest part of Fukuoka City. During the earthquake, liquefaction took place mainly in the reclaimed lands of the Hakata Bay area and caused structural damage. In this paper, the distribution of the sites where liquefaction occurred and the characteristics of the grain size of sand boils collected at the sites were clarified. Further, the occurrence of liquefaction in the reclaimed land was discussed with reference to some instances, and the structural damage was summarized. Furthermore, liquefaction analysis was performed using a program called “SHAKE,” and several soil profiles of the reclaimed land and alluvial ground in order to investigate the relationship between the occurrence of liquefaction and the distribution of acceleration, which was estimated from earthquake response analyses and the mechanical and physical properties of the soils.

Eigenspace technique for object characterization in a disaster field

In this paper, we have proposed an application of pattern recognition technique to recognize partially destroyed objects in debris. The study employs an appearance-based eigenspace technique for investigating the representation and recognition of partially destroyed objects, which is one of the severe limitations of this technique. Since the conventional parametric eigenspace technique cannot handle the occluded or even partially destroyed objects, we propose creation of a mean-appearance for representing and recognizing them. The word mean-appearance describes a mean image set, which allows some partially destroyed objects for producing an eigenspace. In the mean image set, averaging of a few destroyed images along with non-destroyed images make a mean appearance, which has less effect of partially destroyed images. In addition, we have proposed to apply eigenspace method to measure lost goods in debris when the conventional method will not be an alternative. The proposed approach is performed using various destroyed objects and experimental results show the effectiveness of the proposed method.