Study on one-dimension consolidation mechanism, equation and Analytical Solution of soft soil in vacuum preloading

Abstract

Measured values of excess pore water pressure in soil under vacuum preloading were analyzed. Action process of vacuum preloading was compartmentalized three phases. They were seepage consolidation in shallow soil and “surcharge” effect in deep soil by vacuum suction, consolidation stabilization in shallow soil and transformation of “surcharge” 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 stage. The root also included the two pressures superposition under the especial phenomenon of vacuum preloading: water level falling. “Two springs” soil consolidation model of one dimension was established and was applied to analyzing soil consolidation. In early stage of vacuum preloading, “positive pressure” was dominant action in soil consolidation. Effect area of suction was limited and maximal deepness: l <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> was defined. After the early stage, “negative pressure” became dominant action. Soil consolidation equation was established and initial, boundary condition were defined. Analytical Solutions of excess pore water pressure were obtained and discussed.