真空排水预压加固软基中的孔隙水压力消散规律

Dissipation of pore water pressure in soft foundation reinforced by vacuum drainage preloading

真空排水预压加固软基是通过孔隙水压力的消散来增强土体的强度。本文通过浃里陈大桥试验段实测资料,分析了在真空排水预压过程中孔隙水压力在淤泥及砂井和塑料排水板中的消散规律。试验结果表明,地基中的孔隙水压力消散值可分为两个部分:一为真空度的直接传递导致的孔隙水压力下降值;二为抽真空引起水位线下降进而引起的孔隙水压力消散值。淤泥地基中孔隙水压力消散主要是由于地下水位线的下降引起的,砂井和塑料排水板中的孔隙水压力消散大部分由真空度直接引起,孔隙水压力的消散程度沿深度方向基本不变。真空排水预压塑料排水板中孔隙水压力影响深度可达塑排板下4～5m。塑料排水的真空排水预压效果优于砂井。

The strength of soil can be improved by dissipating the pore water pressure by means of vacuum drainage preloading.In this paper,the in-situ experimental data of a bridge pier foundation is used to analyze the dissipation law of pore water pressure in silt and sand in the process of preloading.The result shows that the dissipation of pore pressure consists of two parts.One is formed by the direct effect of vacuum and the other is due to the lowering of groundwater table.The dissipation of pore water pressure in silt is resulted from lowering of the groundwater table,while in sand well and in the vicinity of plastic drainage plate it is resulted from the effect of vacuum.The degree of dissipation does not change along the depth but the effect of dissipation will be maintained even in the depth of 4～5m below the plastic drainage plate.Consequently,the plastic drainage plate is the best way for reinforcement of foundation.