黏性土地区螺杆灌注桩竖向承载力静载试验

Experiment on Vertical Bearing Capacity of Screw Grout Pile in Cohesive Area

目的研究螺杆灌注桩单桩竖向承载力,为其在粉质黏土地区实际工程应用提供合理的设计依据.方法通过螺杆灌注桩的静载试验数据,结合螺杆桩的工作机理,根据土层假设不同的螺杆桩极限承载力侧摩阻力标准值提高系数,建立不同土质情况下承载力等式,利用方程求根及矩阵线性回归等数学方法得到桩在粉质黏土中的侧摩阻力提高系数,建立单桩竖向极限承载力标准值计算公式.结果桩周土为软塑黏土、可塑黏土、硬可塑黏土、硬塑黏土时,桩极限侧摩阻力标准值提高系数分别为1.0～1.2、1.2～1.3、1.4～1.6、1.6～1.8.结论螺杆灌注桩单桩竖向极限承载力相比现行规范中经验参数法计算得到的承载力数值提高较大,研究结果对螺杆灌注桩在粉质黏土地区的设计和施工具有指导意义.

The vertical bearing capacity of single pile of screwgrout pile was studied to provide reasonable design basis in its practical application. Through the static load test of screwgrout pile,with the combination of working mechanism of screwpile,the side friction increase coefficient of pile in silty clay was obtained by using the mathematical methods of multivariate equation extract roots and linear regression,and the calculation formula of standard value for vertical ultimate bearing capacity of single pile was established. The standard value for ultimate side friction increase coefficient of pile were respectively 1. 0 ～ 1. 2、1. 2 ～ 1. 3、1. 4 ～ 1. 6、1. 6 ～ 1. 8 when the soil around pile were soft plastic clay,plastic clay,hard plastic clay,hard plastic clay. The screwgrout pile vertical ultimate bearing capacity of single pile was increased larger when compared with bearing capacity value calculated by empirical parameter method in current codes,the research results had guiding significance for the design and construction of screwgrout pile in silty clay area.