In-Situ Experiment and Analysis on Well Resistance of Gravel Drains

ABSTRACT A series of in-situ experiments was performed to evaluate the well resistance of gravel drains, and to quantitatively define the preventative effects of such gravel drains on increasing pore water pressure due to earthquake motion in liquefiable sandy deposits. This paper confirms that the well resistance of the drains is extremely large although the permeability coefficient of the drain material is more than 400 times that of the deposit. Disregarding well resistance is also clarified to be impractical in the spacing pitch design of drain piles. The values of the measured pore pressure ratio during vibration are found to be easily predicted by calculation using a simple equation.