中文摘要：

螺旋挤土桩在国际桩基工程领域占据着重要的地位,为了深入研究螺旋挤土桩下旋成孔过程的力学特性,运用颗粒离散元方法对螺旋挤土桩下旋成孔过程进行了仿真模拟。在直剪试验的基础上确定了土样细观参数,建立数值模型,模拟研究了螺旋挤扩钻具以不同掘进下旋速度比在浅层和深层土中的掘进过程,通过与试验规律的对比,验证了数值模型的有效性,分析了桩侧土体的位移发展模式和力学响应,探讨了钻具与土体作用机理。研究结果表明,成孔的机理同钻具的掘进旋转速度密切相关,降低掘进旋转速度比,能减小钻具对周围土体的扰动范围,浅层与深层土体的位移模式不同;孔周围应力分布同钻具掘进下旋速度比相关,降低钻具掘进旋转速度比,可有效地减小钻具掘进的竖向阻力。

英文摘要：

The soil displacement screw piles have been extensively used in the international foundation field.In order to study their mechanical behaviors of augered piling,the discrete element simulations are conducted.The micro-simulation parameters are gained to simulate the behaviors of Fujian standard sand under direct shear condition.Based on the parameters,a ground model is formed in PFC3D.A comparison between numerical and experimental results shows reasonable agreement.The mechanism of drilling with different penetration rates of auger in different depth soil layers are studied by considering displacement development,stress distribution and the auger resistance development.The numerical results show that the mechanism of borehole depends on penetration rate of auger.Lower penetration rate reduces the disturbed range of the soil around the borehole and vertical resistance of auger.The displacement mode of the soil varies at different depths.