软土地区基坑前排倾斜双排桩支护现场试验及工作机理

Field Experiment and Working Mechanism of Foundation Pit Excavation Retained by Front-row Inclined Double Row Piles in Soft Soil Area

基坑倾斜桩支护大幅提高了无支撑支护结构的适用深度,具有造价低、施工便捷、绿色低碳、变形控制好等特点,然而目前研究多集中在单排倾斜桩,对前排倾斜双排桩支护的试验、理论与应用的研究均较少。针对前排倾斜双排桩支护基坑开展了现场试验,同时采用有限元方法分别从前排斜桩、桩顶连梁及桩间土体作用3个方面深入探究了前排倾斜双排桩支护的工作机理,进一步分析了直斜桩长度和排距对前排倾斜双排桩支护结构受力变形性能的影响。结果表明,相比传统竖直双排桩,前排倾斜双排桩支护结构的支护性能显著提升,前排斜桩主要发挥“斜撑”作用,连梁主要起到将直斜桩及冠梁连接成一个空间刚架的作用,桩间土体能够提高桩土摩阻力,进而有效减小前排倾斜双排桩变形。研究成果有助于前排倾斜双排桩的推广和应用。

Inclined pile support has notably extended the applicable depth of unsupported retaining structures,boasting advantages such as cost-effectiveness,ease of construction,environmental friendliness,and precise deformation control.However,current researches focus on single row inclined piles,while research on the testing,theory,and application of inclined double-row pile support remains limited.We conducted field experiments to assess excavation supported by double-row piles with the front row inclined.Additionally,employing the finite element method,we investigated the underlying working mechanisms from three aspects:the front-row inclined double-row piles,the connecting beam on top of piles,and the soil interaction among piles.We further examined the impact of pile length and row spacing on the deformation characteristics of inclined double-row piles.Our findings indicate a marked enhancement in the supportive capabilities of front-row inclined double-row pile compared to traditional vertical double-row piles.The front-row inclined double-row piles primarily serve as diagonal bracing,while the beams connect the piles and the crown beam into a spatially rigid frame.Soil between the piles enhances pile-soil friction,effectively mitigating deformation in inclined double-row piles.