Some Aspects of Surcharge Precompression on Ground with Sand Drains

According to engineering practice of surcharge precompression on Ningbo Airport and Wenzhou Airport etc.,consolidation analysis of ground with sand drains under preloading by FEM is discussed in this paper. The deformation characteristics of normally consolidated soils are studied in laboratory and field preloading tests, which demonstrate that there are positive effects for surcharge precompression to reduce the deformation resulting from secondary consolidation and to delay the occurrence of secondary compression. A method of calculating deformation after unloading of the surcharge is developed. Furthermore, a so called effective stress area ratio is proposed, which may be used to determine the amounts of surcharge and the preloading period.