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首页> 外文会议>IUYAM Symposium on Theoretical and Numerical Methods in Continuum Mechanics of Porous Materials, Sep 5-10, 1999, Stuttgart, Germany >Settlements of Sand due to Cyclic Twisting of a Tube
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Settlements of Sand due to Cyclic Twisting of a Tube

机译：由于管子的周期性扭曲而导致的沙子沉降

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摘要

Bored piles are constructed by filling concrete into an excavated borehole with the purpose of transferring load to bearing strata below the building. Large diameter bored piles are used with increasing frequency and confidence in urban areas where the reduction of noise and vibrations during installation plays a primary role. The construction of bored piles in cohesionless soils usually requires a casing to support the borehole during its excavation. The casing consisting of a steel pipe is usually driven into the soil by a simultaneous axialy push and cyclic torsion with constant amplitude and low frequency. As it is empirically well known, cyclic torsion eases penetration considerably, but it has the negative side effect of generating settlements at the surface around the pile. In this paper an experimental and numerical investigation of the penetration of a tube in a sand with the aid of cyclic twisting is presented. In the experimental part a steel pipe was installed in a cylindrical chamber, and loose sand was deposited into the chamber under controlled conditions. Afterwards, cyclic rotation with constant amplitude was applied to the tube while monitoring settlements at the surface. In the numerical part of the investigation a 3D-FE model was used to simulate the experiment and to compare the penetration resistance with and without cyclic twisting. The behaviour of the soil was modelled by a hypoplastic constitutive law, and interface friction was assumed to follow the Mohr-Coulomb friction law. The material constants were determined by means of conventional laboratory tests.
机译：钻孔桩是通过将混凝土填充到开挖的钻孔中来构造的，目的是将载荷传递到建筑物下方的承压层。大直径钻孔桩在城市地区使用的频率和置信度越来越高，在安装过程中减少噪音和振动起主要作用。在无粘性的土壤中建造钻孔桩通常需要使用套管来支撑钻孔过程。通常，由钢管组成的套管通过恒定的振幅和低频的同时轴向推力和循环扭力被打入土壤。如经验上众所周知的那样，周期性扭转大大减轻了穿透力，但是具有在桩周围的表面产生沉降的负面影响。在本文中，借助于循环扭曲，对管在沙子中的渗透进行了实验和数值研究。在实验部分中，将钢管安装在圆柱形腔室中，并且在受控条件下将松散的沙子沉积到腔室中。之后，将恒定振幅的循环旋转应用于管子，同时监视表面的沉降。在研究的数字部分中，使用了3D-FE模型来模拟实验并比较有和没有循环扭曲时的抗穿透性。土壤的行为是通过一个次生本构定律建模的，并且假定界面摩擦遵循Mohr-Coulomb摩擦定律。材料常数通过常规实验室测试确定。

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