A simplified model for vibro compaction of granular soils

In many applications dealing with the foundation of structures on loose granular soils deep vibro compaction measures in the vibro flotation form are needed for the densification of the soil formation. An additional beneficial effect of this densification method is the increase of the resistance against liquefaction especially under seismic loading. One of the challenging questions refers to the size of the compaction grid points on ground surface in order to achieve a certain densification degree prior to the application of the foundation loads. In the majority of the known cases especially for the spacing between densification points empirical rules were applied based on the knowledge of the executing specialized company under similar site conditions. The empirical rules may in some cases be sufficient for the design but not always. In the present paper a method is outlined how the spacing of the densification points can be estimated using an analytical or a numerical approach in combination with the high cycle accumulation model (HCA) which is well known and can be used for a realistic estimation of the densification zone. The method can also be used in construction sites where the amplitude of vibration in the sandy soil can be measured in the vicinity of the rod vibrator and the HCA-model is used for the estimation of the densification intensity and area around the vibrating tube.