超大面积深基坑盆式开挖的工程实例分析

Analysis on Basin-type Excavation Example of Oversized Area Deep Foundation Pit

基坑回弹变形是基坑开挖卸载过程影响基坑安全较大的因素之一。基坑回弹量与卸荷量、基坑面积、支撑和围护结构等方面有关,基坑回弹量过大时,会带动立柱桩上抬,将降低混凝土内支撑的承载力或使钢支撑失稳破坏,超大型基坑回弹变形尤其明显。除对基坑支护结构采取针对性措施外,通过基坑土方开挖工序的优化,也可以达到降低基坑回弹量的目的。结合上海宝山区某全地下污水厂超大面积深对基坑工程实例,分析盆式开挖方式对超大面积深基坑回弹的影响。最终计算及实测数据表明:由于底板提前分块形成,充分发挥了工程抗拔桩的作用,基坑回弹变形量显著减小。

The resilient deformation of foundation pits is one of factors influencing the safety of foundation pit in the process of excavation and unloading.The resilience value of foundation pit is related to the unloading,foundation pit area,support and enclosure structure.The resilience value of foundation pit if too large will drive the column pile up,which will reduce the bearing capacity of the support in concrete or make the steel support instable failure.The resilient deformation of the oversized foundation pit is especially obvious.The optimization of earth excavation process of foundation pit can also reach the purpose of reducing the resilience value of foundation pit besides the targeted measures of support structure for foundation pit.Combined with an oversized area deep foundation pit case of full underground wastewater treatment plant in Baoshan District of Shanghai,the influence of basin-type excavation method on the resilience of oversized area deep foundation pit is analyzed.The final calculation and the measured data show that the baseboard formed by blocks in advance fully plays the role in the engineering anti-uplift pile.The resilient deformation of foundation pit is obviously reduced.