夯扩碎石桩单桩载荷试验数值模拟

Numerical modeling of loading tests on a rammed aggregate pier

对一初始直径0.76m、桩长5.05m的夯扩碎石桩单桩建立数值模型,精确模拟其夯扩和载荷试验分级加载过程,并对同一直径和桩长的未夯扩碎石桩进行了数值模拟以作比较分析。计算和实测的夯扩碎石桩桩顶和桩端荷载–沉降曲线吻合很好。未夯扩与夯扩碎石桩桩顶沉降比值在1.8～10.7之间,而两者的桩端沉降量都很小。未夯扩碎石桩桩身侧向膨胀比相同荷载下的夯扩碎石桩大很多。夯扩碎石桩桩身轴力沿深度衰减幅度较大;而未夯扩碎石桩当桩顶荷载较大时,由于桩身侧向膨胀增大,桩身侧摩阻力也随之增大,桩身轴力则表现为沿深度衰减幅度逐渐增大。

A three-dimensional numerical method is used to delicately simulate the installation and in-situ loading tests on a single rammed aggregate pier （RAP） with the initial diameter of 0.76 m and initial length of 5.05 m. An unrammed aggregate pier （UAP） with the same dimensions is also simulated using the numerical method for the purpose of comparison. The computed and measured settlements at the top and bottom of the RAP are in good agreement. The ratio of the UAP to RAP top settlements is 1.8 to 10.7 whereas their bottom settlements are quite small. The bulging along the UAP shaft is much greater than that along the RAP shaft at the same loading. The magnitude of axial forces along the RAP shaft decreases significantly with depth, while for the UAP, the bulging along the shaft becomes greater as the top loading increases to a certain level. The bulging increases shaft friction forces. As a result, the magnitude of axial forces along the shaft decreases significantly with the depth.