公路软土地基处理中Y型沉管灌注桩异形特性研究

Research on Abnormity Characteristic of Y-shaped Tube-sinking Cast-in-situ Pile in Highway Soft Ground

介绍了用AutoCAD求解Y型桩截面几何特性的方法,通过移轴及坐标变换证明了Y型桩截面任意1对形心轴均为其形心主轴,截面对任意1个形心主轴惯性矩相等。分析了Y型桩截面的4个独立变量(外接圆半径、模板弧度、开弧间距、夹角度数)对Y型桩的几何异形特性的影响,并根据周长等代与面积等代的原则对Y型桩、方桩和圆桩的几何特性进行了对比。理论分析结果表明:从增大桩侧表面积、减少混凝土用量的角度来看,Y型桩优于方桩,方桩优于圆桩。现场试验结果表明:Y型桩承载力随桩侧表面积的增加而增大,尽管反拱曲面存在摩阻不均匀发挥的特性,但未发现其异形摩阻弱化效应。

Method of calculating geometry characteristic about Y-shaped tube-sinking cast-in-situ pile section by AutoCAD was introduced. The conclusions that random centroid axis of inertia was centroid principal axis of inertia and random centroid principal axis of inertia had same moment of inertia were proved by parallel-axis and changing coordinate. Influences of circumscribed circle radius, cyclostyle angle, arc space, degree of included angle of Y-shaped pile on the abnormity characteristic of Y shaped pile section were analyzed. Geometry abnormity characteristics of Y-shaped tube sinking cast in situ pile, quadrate pile and circular pile by same area or same perimeter were contrasted. Theoretical analysis results show that Y shaped tubesinking cast-in-situ pile is better than the quadrate pile, and the quadrate pile is better than the circular pile from the point of view of reducing concrete and augmenting skin area. Field test results show that effects of increasing of bearing capacity and lateral surface area are all obviously. Although characteristic of fricion asymmetry exertion probably exists in inverse arch surface, but its weak effect of abnormal friction is not found.