Centrifuge testing on the global stability of geosynthetic-reinforced and pile-supported embankment

Abstract

The global stability of geosynthetic-reinforced and pile-supported (GRPS) embankments on soft foundations is one of the great concerns for geotechnical engineers in design and construction process. The current analysis theories for the stability of GRPS embankment are essentially based on the two-dimensional limit equilibrium method under various assumptions. However, up till now, there still lack of enough consensus on the failure modes of the foundation piles as well as the geosynthetic reinforcement in GRPS embankment. Furthermore, the assumptions of the circular slip surface shape in the current methods might raise disputes over the safety factor evaluations. In order to investigate the failure mode and load transfer mechanism of GRPS embankment, a series of centrifuge model tests were conducted in this study. Results revealed that the GRPS embankment showed a progressive sliding failure pattern in the model test condition. The sliding surface in GRPS embankment presented a composite shape instead of a circular shape. For the model piles with relative low strength in the current study, bending failure obviously took place instead of shear failure. The model piles near the toe side of the embankment experienced failure firstly, followed by the piles beneath the embankment shoulder and center. The positive effect of the geosynthetic reinforcement on the embankment stability was effectively proved as the critical centrifugal acceleration of the global instability of the model embankment N_{f, global} without basal reinforcement was 22.8 g, which increased to 30.9 g and 38.7 g for other two cases involving basal reinforcement. The critical centrifugal acceleration of the model geogrid, which was larger than N_{f, global}, also increased from 32.6 to 41.6 g when the tensile strength of geogrid increased from 1.87 to 3.24 kN/m.