Comparison of vacuum consolidation with surcharge load induced consolidation of a two-layer system

Laboratory consolidation tests for a two-layer soil system under oedometer conditions were conducted under both vacuum pressures and surcharge loads. The effects of the order of soil layers on the behaviour of vacuum consolidation of the two-layer soil system have been investigated by comparing vacuum pressure and surcharge load induced consolidations. Under one-way drainage conditions, for both a surcharge load and a vacuum pressure, the order of soil layers only influences the rate of consolidation but not the final settlement. When a layer with a relative lower value of hydraulic conductivity (k) is located immediately adjacent to the drainage boundary, the consolidation rate is slower. However, for vacuum pressure applied under two-way drainage conditions, the order of the soil layers not only influences the rate of consolidation but also the magnitude of settlement.