Design and Calculation Method for Composite Foundation Using Large-diameter Rigid Piles in Pebble Bearing Soil

Abstract

In the composite foundation using rigid piles, large pile-soil stress ratio often results in insufficient exploitation of bearing capacity of soil among piles. The rigid piles bear most of the vertical loads which makes the stress mechanism similar to that of pile foundation and fails to save cost. Based on the test and study of pile shaft resistance and tip resistance in the composite foundation using large-diameter rigid piles in pebble bearing soil and the stress monitoring of pile top and soil among piles, the pattern of variation in pile-soil stress ratio of composite foundation using large-diameter rigid piles was achieved. Furthermore, according to field test, use of cushion would lower the stress in rigid piles and exert bearing capacity of soil among piles which leaded to higher bearing capacity of composite foundation and smaller differential settlement. In contrast to “Technical Code for Ground Treatment of Buildings” (JGJ79-2012), a new design and calculation method for composite foundation using large-diameter rigid piles in pebble bearing soil was proposed based on the results from field test, numerical simulation and theoretical analysis. This improved and practical method has fully considered the potential bearing capacity of soil among piles and has been verified through practical engineering cases.