Stress redistribution and deformation mechanisms in piled embankments subjected to excavation in clay

This research explores how excavation impacts piled embankments in clayey ground through comprehensive numerical simulations. The study specifically evaluates the role of excavation depth and the relative embedment of diaphragm walls in shaping the response of the system. Three configurations were assessed based on their position in relation to the piles: near the upper part of the piles, close to the base, and entirely below the pile base. Additional simulations were carried out for a geogrid-reinforced piled embankment in the deepest excavation scenario and for an embankment supported by end-bearing piles in the intermediate depth case. The hypoplastic constitutive model for clay was employed to account for nonlinearity in soil behaviour influenced by stress variation, dilation, and stiffness reduction. The hypoplastic clay model parameters were calibrated using laboratory test data, and validated through back-analysis of a centrifuge test reported in earlier research. The results reveal that deeper excavations produce greater settlement, particularly affecting piles situated close to the excavation zone. Settlements ranged from 10 to 28 mm, with lateral deflections of the piles increasing substantially as excavation progressed. Stress redistribution within the embankment altered the load transfer mechanisms, reducing the effectiveness of soil arching and increasing load concentration on the piles. The highest load intensities were observed adjacent to the excavation face. The geogrid-reinforced system displayed better performance by limiting ground deformation and improving load distribution, while end-bearing piles demonstrated superior resistance to excavation-induced settlement and movement compared to floating piles. This study emphasizes the need for careful design and monitoring when excavations are conducted near piled embankments, particularly in soft soils.