Simplified design method for pressure reduction and anti-floating of blind drains of underground structures

At present, the numerical analysis methods are mainly used for the design of blind drains in pressure reduction and anti-floating systems, and there is no simple and practical simplified method. Based on the assumption that a blind drain has an equal water head boundary and the infiltration amount is uniformly distributed in the blind drain unit, a simplified model for the blind drain grid is established. The analytical solution of the water head distribution of the blind drain unit with a rectangular layout is obtained. The water head distribution within the blind drain unit can be calculated by providing the parameters such as the infiltration amount and the geometric size of the unit. A model for calculating the distribution of bottom plate infiltration is proposed under both uniform and non-uniform infiltration conditions. Through numerical examples, it is verified that the simplified method is applicable if there is a hydrophobic layer with permeability much greater than the soil at the bottom of the blind drain and structural bottom plate. The relative error between the simplified algorithm and the finite element results is small and the results tend to be conservative, which can be used for the design of layout of blind drains. By comparing typical soil layers, it is found that if the lower layer of the bottom plate is a weakly permeable one with a layer of strongly permeable layer, the infiltration amount of the bottom plate will be evenly distributed, and blind drains can be evenly arranged at equal intervals. If there is no strongly permeable layer in the lower strata, the infiltration amount is mostly concentrated within the range of 1 to 1.5 times the thickness of the aquifer at the bottom of the pit from the curtain. The distance between blind drains should be reduced within this range and increased in the middle of the bottom plate.