Geocomposite induced consolidation of clayey soils under stepwise loads

The consolidation behavior as well as the strength increment of clayey soil induced by drainage geocomposite has been investigated by large scale model tests (0.3 m × 0.6 m × 1.0 m) and theoretical analyzes. The test results indicate that (1) a geocomposite with a high confined in clay discharge capacity (qw) can provide a sufficient drainage path for accelerating the self-weight induced consolidation of an embankment with clayey backfill with and without small amount cement or lime additives; and (2) the consolidation induced by geocomposite can reduce the void ratio of the clayey soils and increase undrained shear strength (su) of the soil considerably. Considering the scenario of embankment construction, a semi-theoretical method for predicting the value of su in an embankment is described. A comparison of the measured and calculated su values of the model tests shows that the proposed method is useful. Then the method is applied to a case history of embankment construction with clayey backfill in Japan, and the slip circular analysis indicates that the geocomposite induced consolidation increased the su value of the backfill and therefore the factor of safety (FS) of the embankment significantly.