预留土对非饱和基坑支护结构的影响

INFLUENCE OF EARTH BERM ON RETAINING STRUCTURE FOR UNSATURATED PIT EXCAVATION

基于《建筑基坑支护技术规程》的相关规定和非饱和土强度理论,建立了考虑预留土的嵌固和水平支撑双重作用和非饱和特性时支护结构嵌固深度、位移和内力的计算方法。研究表明,预留土的作用可以概括为两个方面:①虽然能提供的水平抗力不是很大,但由于其合力力臂较大,因此对支护结构有明显的嵌固作用,从而可以缩短支护结构的嵌固深度;②能在支护结构上部形成弹性支承,从而减小支护结构的水平位移和内力。算例分析表明,采用预留土并降水的施工方法能大幅度缩小支护结构的嵌固深度、位移和内力。因此,在条件适当的条件下,用基坑内侧预留土并降水的施工方法不仅可以省去水平支撑、降低支护结构嵌固深度,同时还可以节约投资和缩短工期,具有良好的经济效益、社会效益和环境效益。

Based on the technical specification for retaining and protection of building foundation pit and strength theory for unsaturated soils,computational methods are constructed for embedded depth,displacement and inner force determination of retaining structure for unsaturated pit.The mechanical studies show that the functions of earth berm for unsaturated pit include two aspects.The first one is that the necessary embedded depth of the retaining structure can be reduced because of the longer force arm of the horizontal resisting force.And the second one is that the displacement and inner force of the retaining structure can be reduced for its horizontal elastic ssupporting.Analysis on an example illustrates that the construction method using earth berm in pit excavation together with lowering groundwater can decrease the embedded depth,displacement and inner force of retaining structure remarkably.Therefore,the construction method is economical due to sparing horizontal supporting structure as well as reducing project time.