安全防护下沿海地区淤泥质软土深基坑开挖施工方法

Construction method of deep foundation pit in muddy soft soil in coastal area under safety protection

淤泥质软土的特点强度低、含水量大等,给地基的开挖带来很大的困难,往往被称为开挖禁区。本文结合沿海地区淤泥质软土深基坑开挖工程,通过有限元软件Plaxis 3D对整个深基坑的施工过程进行模拟。以基坑变形为指标,研究了支护结构的影响。结果表明当双排桩前桩长度为7.5 m时,双排桩前后排桩变形一样。双排桩整体变形随着前排桩桩身长度的增长先减小后增大。前排桩桩长控制在15 m内,增大桩长可以很好的控制基坑变形。双排桩整体变形随着后排桩桩身长度的先迅速减小随后缓慢较小。前排桩桩身变形始终大于后排桩桩身变形,这是因为后排桩起到了足够的拉锚作用。深基坑变形随着双排桩排距增大首先快速减小随后缓慢减小。当双排桩排距超过6 d时,这种控制变形的效果愈来愈小。综上所示,本工程最合适的排距为4~6 d。

The characteristics of muddy soft soil,such as low strength and high water content,it bring great difficulties to the foundation excavation,belong to excavation forbidden zone.Combined with the deep foundation pit excavation engineering in coastal area,the whole construction process of deep foundation pit is simulated by the software PLAXIS 3 D.Taking the deformation of foundation pit as the index,the influence of supporting structure is studied.The results show that when the length of front pile of double row pile is 7.5 m,the deformation of front pile and back pile of double row pile is the same.The overall deformation of double row piles first decreases and then increases with the increase of the length of the front row piles.The length of front row pile should be controlled within 15 m,and the deformation of foundation pit can be well controlled by increasing the length of pile.The overall deformation of double row piles first decreases rapidly and then decreases slowly with the length of back row piles.The deformation of the front row pile is always greater than that of the back row pile,which is because the back row pile has enough anchoring effect.With the increase of double row pile spacing,the deformation of deep foundation pit first decreases rapidly and then decreases slowly.When the row spacing of double row piles exceeds 6 d,the effect of deformation control becomes smaller and smaller.To sum up,the most suitable row spacing of the project is 4~6 d.