Investigation of soil arching evolution in piled embankments with three-dimensional trapdoor tests

This study focused on the mobilisation and degradation of three-dimensional soil arching by adopting a matrix trapdoor test device with 144 individually and electrically controlled movable plates to simulate unreinforced piled embankments at different coverage ratios and fill heights. Movable and fixed plates simulated subsoil settlement and pile behaviour, respectively. The results show that the vertical load on the piles increased rapidly during subsoil settlement due to the mobilisation of soil arching, and stress concentration occurred on the edges of the piles. Soil arching on the strip of the subsoil between adjacent piles was more mobilised than on the central subsoil zone between adjacent four piles. Increase of the fill height increased the ratio of the vertical stress on the piles to the overburden stress. Increase of the pile coverage ratio reduced the ratio of the vertical stress on the piles to the overburden stress and the degradation rate of soil arching. The ground reaction curve showed two segments of stress recovery at a coverage ratio ≤25% due to the asynchronous development of soil arching between side and central subsoils. The Concentric Arches model showed better agreement with the average measured vertical stress on the subsoil at the maximum soil arching state than other analytical models.