Bearing capacity and stiffness of pile group foundation

Abstract

Pile group foundations are widely employed in geotechnical design. Bearing capacity increment/reduction of pile group (PG) foundation in design practice often described via empirical efficiency factor (EF), a multiplier to sum of single piles (SP) resistances, when they act isolated. The magnitude of EF depends on spacing of SP in PG, soil parameters, configuration of piles, friction of soil-pile, etc. Proposed predictions for choosing the EF magnitude are contradictory. The tests of displacement SP and PG tests conducted in laboratory conditions for 2 spacing cases, ground stress-strain evolution of PG analyzed. The EF magnitude reproduced from tests results compared with proposed by different authors predictions. The pronounced effect of installation sequence to displacement SP response measures, when acting in PG estimated during the tests. From practical point, this phenomenon if ignored for certain connection case of superstructure with PG cap and that of SP with PG cap may cause unexpected PG foundation movements, subsequently resulting the additional stressing of superstructure and foundation. SP installation effect for displacement PG foundation measures of ground response should be properly evaluated in design of constructional elements of superstructure and foundation.