The comparison of the safety zone in the vicinity of marine clay treatment areas with and without surcharge and vacuum preloading

One of the important parameters that should be considered in designation of weak clay and peats treatment systems is the influence zone wherever there are infrastructures or sensitive buildings in the vicinity of the treatment area. Since large vertical and horizontal displacements occur in these treatment systems, the soil around the project undergoes large strains that should be accounted for in project planning prior to finalization of the treatment system. The treatment systems for weak clays and peats are often a combination of prefabricated vertical drains plus vacuum and/or surcharge preloading. For investigation of the impact of preloading agents, and FEM simulation of two case histories were performed. One the project incorporates the combination of surcharge and vacuum preloading while the other one consisted of only vacuum preloading without surcharge embankment. Based on the verified models, different scenarios were introduced for comparison of impact of the vacuum and preloading agents on the magnitude of the influence zone. Regarding the impact of surcharge embankment, it was shown that reducing the height of surcharge can drastically reduce the influence zone in both numerical simulations. The application of vacuum preloading as the only preloading agent has decreased the influence zone drastically and for urban areas or places that sensitive infrastructures exist might be an ideal option for similar cases. Regarding the impact of magnitude of vacuum pressure on the influence zone it was shown that application of a stable high vacuum pressure can significantly reduce the diameter of the influence zone.