锚索布置对长短双排桩的受力影响分析研究

Analysis and research on the influence of anchor cable arrangement on the stress of long and short double-row pile

双排桩支护结构作为一空间组合支护结构,受力复杂,影响其支护性能的因素较多,将原单排锚拉桩方案调整为“前桩短,后桩长”的双排桩支护结构形式,为研究基坑支护中不同锚索竖向间距布置对长短双排桩桩身受力的影响及桩身传力规律,通过极限有限元分析法对结构支护体系进行了分析计算,结论如下:(1)双排桩与单排桩支护结构桩身弯矩图存在明显不同,后排桩弯矩图朝坑内方向变形,呈“反C”型,桩身最大弯矩位于在0.45H~0.55H范围内,桩身受力以基坑内方向受拉为主。前排桩弯矩图受锚索分布影响呈“WW”型,桩身最大弯矩位于0.3H~0.6H范围内,桩身受力以基坑外方向受拉为主。(2)后排桩呈受的弯矩是前排桩的1.5~2倍。后排桩主要呈受承载土压力的作用,前排桩起到挡土和传递土压力的作用;(3)采用不同的锚索布置方案时,前排桩嵌固深度不足时,应采用锚索加密布置的方案有利于桩身的整体变形稳定,也有利于基坑开挖安全。

As a spatial composite retaining structure,the double-row piles retaining structure has complex stress,and there are many factors affecting its supporting performance.The original single-row anchor pile scheme is adjusted to the double-row piles retaining structure of"the front pile is short,the back pile is long",in order to study the influence of different vertical spacing arrangement of anchor cable on the stress of long and short double-row piles and the load transfer law of piles in foundation pit supporting.The limit finite element analysis method is used to analyze and calculate the structural support system,and the conclusions are as follow(1)The bending moment diagram of double-row piles is obviously different from that of single-row piles.The bending moment diagram of the rear row piles is deformed towards the pit,which is in the shape of"reverse C".The maximum bending moment of the pile body is in the range of 0.45 H~0.55 H,and the pile body is mainly stressed in the direction of the foundation pit.The bending moment diagram of the front row of piles shows"WW"type due to the influence of anchor cable distribution,the maximum bending moment of the pile body is in the range of 0.3 H~0.6H,and the main force of the pile body is tension in the direction outside the foundation pit.(2)The bending moment of the rear piles is 1.5~2 times of that of the front piles.The back row piles are mainly subjected to the bearing earth pressure,and the front row piles play the role of retaining earth and transferring earth pressure;(3)When different anchor cable layout schemes are adopted and the embedded depth of the front row of piles is insufficient,the scheme of dense anchor cable layout should be adopted,which is conducive to the overall deformation stability of the pile body and the safety of foundation pit excavation.