冠梁对既有-新增双层排桩支护结构工作特性的影响

Influence of crown beam on working characteristics of existing-new double-layer row pile supporting structure

以既有建筑增层开挖为研究背景,采用室内模型试验的方法建立地下空间向下增层既有-新增双层排桩支护结构模型,对地下空间向下增层过程中既有-新增双层排桩支护结构的工作特性进行研究,重点分析冠梁对既有-新增双层排桩支护结构桩顶水平位移和桩身弯矩的影响。研究表明,有冠梁约束时既有支护桩桩顶水平位移曲线比无冠梁约束时更平缓,增设冠梁能够明显减少空间效应对支护结构的影响;增设冠梁后,前后排桩的桩顶水平位移差由10.43 mm减少为0.06 mm,有效提高了前后排桩的整体性;既有支护桩桩顶增设冠梁后,既有支护桩桩身弯矩明显增大,而新增支护桩桩身弯矩变小。

Taking the excavation of existing buildings as the background,this paper first established a model for the existing-new double-layer row pile supporting structure by means of indoor model experiment.It then studied the working characteristics of the existing-new double-layer row pile supporting structure with downward storey increase in underground space.Finally,it emphatically analyzed the influence of crown beam on the horizontal displacement of pile top and bending moment of pile body of the existing-new double-layer row pile supporting structure.The research shows that the horizontal displacement curve of the top of the existing support pile with crown beam restraint is much smoother than that without crown beam restraint,and that the addition of crown beam can significantly reduce the influence of spatial effect on the supporting structure.After the crown beam is added,the difference of pile top horizontal displacement between the front row piles and the back row piles is reduced from 10.43 mm to 0.06 mm,which effectively improves the integrity of the front row piles and the back row piles.After the crown beam is added to the top of the existing supporting pile,the bending moment of the existing supporting pile increases obviously,while the bending moment of the newly added supporting pile decreases.