冲淤沉积层中新型咬合桩工法及应用

通过分析冲淤沉积层的特点和套管咬合桩的施工工艺,对套管咬合桩在冲淤沉积层中的扩径现象进行研究。指出在该地层中套管咬合桩施工产生扩径的主要原因是套管下沉对地层的扰动、周围土体向管内涌挤而产生的超挖和缓凝混凝土对地层的挤压扩张作用。提出利用水泥搅拌桩替代A序素混凝土桩,用有钢筋笼的B序桩咬合A序的水泥搅拌桩,形成钻孔桩咬合搅拌桩的一种新型咬合桩工法。该工法可以有效解决在冲淤沉积层中进行咬合桩施工时的扩径问题和止水问题。该工法在南京地铁西延线工程中得到应用,取得了较好的应用效果。

The Construction Method and Application of New-Style Secant Piles in Alluvium

Based on the analysis of the construction technology of secant piles in alluvium,the phenomenon of hole enlargement is studied.The main reasons of hole enlargement occurred in alluvium are pointed out,which are the ground disturbance of pipe setup, overexcavation owing to surrounding soil squeezing to the pile pipe and extrusion of delayed coagulating concrete to ground.On this basis,a new construction method is put forward.The new method includes the points that the plain concrete piles of A order is substituted by cement mixing piles and that B order piles with reinforcement skeleton intersect A order cement mixing piles.The new method can solve the problems of hole enlargement and retaining groundwater efficiently.The new method has been used in Nanjing metro construction,and the application results are preferably satisfactory.