Effects of geometric arrangement on the interaction behaviour and settlement performance of varying-length rigid inclusions

Abstract

This article deals with the effect of configuration on the load-settlement performance of column-type sub-structural elements with varying lengths, which have been widely used in geotechnical applications to provide cost-effective foundation solutions in weak soil areas. The numerical analysis results show that resting a footing/raft over 5 × 5 cushioned varying-length rigid inclusions (RIs) with an A-shape arrangement pattern (Configuration I) reduces raft settlement by about 12% compared with uniform short RIs and by 4.3% compared with uniform long RIs under the same distributed load. Furthermore, synergistic interactions between the cushion layer, soil and RIs in variable-length RI configurations, particularly those that concentrate longer RIs centrally, outperform uniform groups by enhancing the composite modulus and optimising load transfer to deeper strata. In addition, the farther the RI is from the group centre, the greater the proportion of the applied load it bears. Finally, a simplified load transfer analysis method is proposed using hyperbolic load transfer functions by employing the concepts of traditional pile group analysis, which approximately considers the cushion-RI-soil interaction and the mutual interactive effects of neighbouring varying length RIs in the group. The proposed method produces satisfactory results.