不同施工工艺下桥桩极限承载力仿真研究

Simulation Study on Ultimate Bearing Capacity of Bridge Piles under Different Construction Techniques

为研究正循环成孔、螺旋钻成孔两种施工工艺下桥桩极限承载力,通过对现场静载荷试验进行有限元数值模拟,确定桩基极限承载力及桩侧摩阻力分布,将理论计算值、试验实测值及模拟计算值对比分析。分析结果表明,桩-土界面引入无厚度Goodman摩擦单元,并考虑地应力平衡,能较好模拟桩土真实状态;正循环成孔桩初期的极限承载力较螺旋钻成孔桩小,经过桩周土较长时间的固结,其极限承载力接近于螺旋钻成孔极限承载力;采用螺旋钻成孔的情况下,古土壤和老黄土极限侧摩阻力推荐值为75 kPa。

In order to research the ultimate bearing capacity of the bridge-pile under the different construction processes which are normal circulation and spiral drilling,the value of ultimate bearing capacity and the distribution of the shaft friction resistance along the pile were obtained by the finite element numerical simulation based on the static load tests in site,and the simulation value was compared with the theoretical research value and measured value.The analysis results show that with the introduction of no-thickness Goodman friction unit and consideration of the balance of geostatic,the true state of pile-soil coupling can be simulated well by the finite element,and the ultimate bearing capacity under the normal circulation drilling is less than that under the spiral drilling at the initial stage,but the values can be close to each other in two means with a long time solidification.Under the spiral drilling,the pile-skin friction value recommended for ancient soil is 75 kPa.