Journal of Natural Disaster Science

PORE PRESSURE AND EFFECTIVE STRESS IN A HIGHLY SATURATED SAND BED UNDER WATER PRESSURE VARIATION ON ITS SURFACE

Hiroshi NAGO
Professor, Department of Civil Engineering, Okayama University, Okayama
and
Shiro MAENO
Research Associate, Department of Civil Engineering, Okayama University, Okayama

(Received 10 March, 1987 and in revised form 30 June, 1987)

Abstract

The behavior of pore pressure and effective stress in a highly saturated sand bed under variations in the water pressure on its surface were investigated to determine the mechanism of the collapse of hydraulic structures during flooding or when attacked by storm waves. The vertical, one-dimensional model was used as a basic model to clarify the effect of water pressure variation on only to the vertical direction. The theoretical results show that a sand bed under variations of water pressure is weakened by an increase in excess pore pressure and that under certain conditions the sand bed will liquefy.

Although many factors related to water pressure variation and property of the material determine this phenomenon, the most important factor seems to be the small amount of air present in the sand bed. The theoretical results reported are verified by experiments.

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