摘要
Measured values of pore water pressure in soil under vacuum preloading were analyzed. Action process of vacuum preloading was compartmentalized three phases. They were seepage consolidation in the upper part of the soil and "surcharge load" effect in deep soil by vacuum suction, consolidation stabilization in the upper part of the soil and transformation of "surcharge load" effect to "negative pressure" effect in deep soil, seepage consolidation in deep soil under"negative pressure"effect and to balance. Action mechanism root of vacuum preloading was not negative pressure difference solely,which was produced by seepage field.The root was "positive pressure" action and "negative pressure" action together during different period. Settlement calculation method was obtained and applied to calculating soil settlement.