Evaluation of lightweight aggregate to reduce vertical stresses and improve load transfer in pile-supported embankments

Abstract

Lightweight aggregate has unique characteristics of light self-weight, high friction angle, and good interaction with geosynthetics, and may be used as a fill material in load transfer platforms (LTP) over piles to support embankments on soft soils. This study included five plane-strain trapdoor tests to evaluate the use of lightweight aggregate to improve the performance of load transfer platforms over piled beams to support embankments on soft soils. These model tests consisted of trapdoor downward movement (settlement) and surface loading to investigate the mobilization and degradation of soil arching above the trapdoor. The surface loading was applied locally using a hydraulic jack through a footing. The vertical stresses on the trapdoor and the stationary supports were measured using earth pressure cells and the settlement of the footing was measured using a displacement transducer. Test results showed that soil arching mobilized with the settlement of the trapdoor and degraded with the footing loading. The geosynthetic reinforcement hindered the degradation of soil arching and increased the bearing capacity of the embankment under footing loading. Overall, the lightweight aggregate had favorable soil arching behavior with low vertical stresses on the trapdoor and the stationary supports as compared with the river dand. Lightweight aggregate is proven to be a good alternative material for load transfer platforms in pile-supported embankments.