Evaluation on the full-scale testbed performance of lightweight foamed soil using railroad loading system

초록

The accumulated critical settlement usually occurs at the railway bridge approach zone due to the sudden variation in track stiffness and the difference in foundation property. This problem leads to the fast degradation of the whole track structure. Therefore, this research aims to develop a novel backfill material that helps improve the displacement resistance of the track's supporting layer. The new flowable fill material is designed to gain the advantage of self-leveling, lightweight, and strong stress-bearing capacity through utilizing of local excavated soil, cement, and preformed foam. To cope with this objective, three full-scale testbed sections were constructed including a controlled section (conventional cement treated base), lightweight clay soil section (CL), and lightweight silty soil section (SM). Using the railroad loading system (RSL) to replicate actual trainload behaviour, a static wheel load (0-120kN) and dynamic wheel load (600,000 cyclic sinusoidal loads, 5 Hz) are applied on the surface to record the internal roadbed pressure, elastic, and plastic displacement of the backfill layer. Test results indicate significant improvement of both novel backfill materials compared to conventional cement treated base. With an average reduction for roadbed pressure and displacement of >35% on static loading, and >30% on dynamic loads. Track stiffness was also improved by up to 40% after 300,000 cyclic loads. Overall, all three sections meet the Korea roadbed design standards having a plastic settlement < 3 mm after 1 million dynamic trainloads. This promising solution can be applied in multiple regions to promote the develof sustainable backfill at transition.

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