The principle of the drainage consolidation method is to effectively discharge the water contained in soft soil, reducing the voids in the soil layer and indirectly increasing the degree of consolidation of the foundation. At the current stage of construction, this method mainly employs two approaches: vacuum preloading and the sand well method.

　　1. Vacuum Preloading Method
　　When the soil layer contains no permeable stratum, the vacuum preloading method can be used to extract gas. First, sand wells are installed in the soft soil layer, and a sand layer is laid over the surface; then a sealing membrane is placed on top to isolate the sand layer from the air. Next, construction personnel can use vacuum equipment to extract the gas inside, creating a negative pressure state within. The negative pressure allows the water contained in the soil layer to drain away from below, making the soil layer more consolidated.
　　2. Sand Well Method
　　The sand well method is suitable for soil layers with low permeability. By injecting sand into the boreholes formed in the foundation, the drainage channels can be made more consolidated, ensuring the drainage rate of the soil layer. The greatest feature of the sand well method is that it uses fewer materials and has lower costs, so it is widely applied.