Effects of Providing Drainage Ability to Sheet Piles on Settlement Reduction of Embankment Resting on Liquefiable Sand

Abstract

The sheet pile with drainage ability installed at embankment toes is a liquefaction countermeasure technique that had been extensively employed for river levees. Combined effects of providing lateral confinement to liquefied sand below the levee and drainage ability that accelerates the excess pore pressure dissipation are expected to reduce levee settlement. Since the L2 earthquake was stipulated in the design standards, the technique has not been used because of the difficulties to restrain excess pore pressures below the liquefaction level. However, case histories were reported where deformation was smaller for ground with drains implemented even though the ground liquefied. In this study, a series of centrifuge tests was conducted to investigate the effects of the drainage ability attached to sheet pipes to reduce levee subsidence due to foundation liquefaction. It is confirmed that the effectiveness of the drainage ability in reducing settlement depends largely on the hydraulic conductivity of sand, and that there is a range of hydraulic conductivity within which the effectiveness of the countermeasure increases rapidly. The drainage members on the sheet piles significantly reduce shear deformation around sheet pipe and levee toes even though the soil liquefied.