P-y Model Describing Interactions of Piles and Saturated Degradation Sands

Abstract

Saturated strata will degrade if residual pore water pressures in strata are less than the overburden pressures of strata under seismic loads. Because it is not better understood how to describe the p-y relationships of strata with residual pore water pressures so far, interactions of laterally loaded piles and degradation strata were researched in this paper. Saturated degradation strata were simulated by applying backpressures to strata that overburden pressures were acted on. Fifteen model tests were conducted to research effects of relative densities and residual pore water pressures on p-y relationships of saturated degradation sands. Results showed that lateral resistances of strata gradually decreased with the increase of residual pore water pressures and ultimate lateral resistances decreased by 80-90% for post-liquefaction strata. The method determining the ultimate lateral resistances was developed by defining the equivalent strength of saturated degradation strata and the reduced factor of residual pore water pressure of saturated degradation strata. Subgrade reaction modulus coefficients of saturated degradation strata were analyzed based on model test results, which showed that they also decreased with the increase of residual pore water pressures. Effects of pile-diameter on coefficients were further analyzed using the method of combined the 3D finite element and the Winkler foundation beam. Results showed that coefficients increased with increase of pile-diameter when the diameter was less than 0.4m and approached to constant results suggested in API Code when the diameter was greater than 0.4m. The formula determining coefficients of saturated degradation strata using the equivalent strength was developed. A method determining hyperbola p-y curves of saturated degradation strata was finally developed.