CENTRIFUGE MODELING OF PILE FOUNDATIONS SUBJECTED TO LIQUEFACTION-INDUCED LATERAL SPREADING IN SILTY SAND

摘要

Liquefaction-induced lateral spreading of sloping ground and near waterfronts continues to be a major cause of damage to deep foundations. Even though various foundation analysis and design methods have been proposed,where the soil applies static lateral forces to the pile foundation, there is currently a huge uncertainty associated with the maximum lateral pressures and forces applied by the liquefie d soil, which translates into a similar huge uncertainty in the calculated maximum pile bending moments. Furthermore, recent centrifuge and full-scale 1g shaking table tests of single piles and pile groups indicate that the permeability of the liquefied sand is an extremely important and poorly understood factor, with a suggestion that the pile bending moments in a silty sand may also be much greater than in a clean sand. Previous centrifuge tests at Rensselaer Polytechnic Institute (RPI) of pile groups and single piles, using the same sand, but with water as pore fluid in one of the tests and viscous pore fluid in the other tests, hence simulating two sands of widely different permeability in the field,have shown significant difference in pile foundation response. This article presents preliminary results of two centrifuge tests conducted at the 150 g-ton RPI centrifuge to continue investigating the effect of soil permeability in the response of 2x2 pile groups to lateral spreading, comparing two techniques to simulate the prototype permeability in the field.