UPWARD-SEEPAGE EFFECTS ON BOTH EXCESS PORE-WATER PRESSURE AND SHALLOW-FOUNDATION STABILITY ABOVE SATURATED SAND

Abstract

Upward seepage of water is indicated by the presence of Excess Pore Water Pressure (EPWP),
and liquefaction occurs. In this paper, the effects of upward seepage are discussed based on observations of
the physical model in the laboratory. The samples of sand are collected from two areas in Padang City,
Indonesia. The gradation (sieve analysis) tests are then carried out to obtain sand fraction based on the United
Soil Classification System (USCS). The present experimental results show that upward seepage in saturated
fine-sand causes an increase in the EPWP so that the effective stress decreases. Consequently, the shallow
foundation above it becomes unstable. While the addition of coarse sand on saturated sand can reduce the
EPWP so that the effective stress increases and the shallow foundation becomes stable.