桩与土钉或挡土墙联合使用时设计理论探讨

Discussion on Design Theory on Joint Use of Pile and Soil-nailing or Retaining Walls

研究目的:路堑预加固桩与桩间土钉墙或挡土墙联合使用时设计计算方法尚不成熟,特别是对其"土拱效应"对桩间土钉墙或挡土墙有何影响未见报道过。传统设计时未能很好考虑这一问题,一般按经验进行设计。本文结合南昆铁路某科研试验工点,对该问题进行了深入的理论探讨,提出了一些较新的观点,供同行参考。研究结论:为了使两桩之间形成"土拱效应",应使桩间支挡物的刚度较小,使其后土体具有形成卸荷土拱的松动条件,此时桩身土压力与挡土墙上并不一致,桩上大、桩间墙上则较小,这种受力模式要求我们不必将桩间的土钉墙或挡土墙做得太强;同时由于土拱的拱矢在跨中最大(一般不超过3m),而靠近桩边时较小,故建议土钉长度跨中的要比两边的长3m左右,边上土钉长度也不宜太长。

Research purposes：The design and calculation method are unsatisfactory for joint use of the pre-reinforcement pile and soil-nailing or retaining walls for reinforcing embankment.Especially there is no a report on the influence of the soil-arch effect on the soil-nailing or retaining wall between piles.Generally,the traditional design of it is made according to the experience without full consideration.Combining the research and experiment for the Nanning-Kunming Railway,this paper discusses this issue in theory and presents the new views on it for providing the reference.Research conclusions：For forming a soil-arching effect between two piles,the stiffness of the retaining structure between piles must be lower to make the soil behind the retaining wall forming a loosing condition for unloading the soil-arch.At this moment,the soil pressure on the pile is different than the retaining wall.Namely,the soil pressure on the pile is bigger than the retaining wall.This loading mode requires no very strong soil-nailing wall and retaining wall between piles.At the same time,as the max.arch rise is in the middle of span with no more than 3m and the arch rise near the pile is small,it is proposed the nail length in the middle of span is 3m longer than those on two besides,and the nails length on besides should not be too long.