高频振动贯入灌注桩套管土塞效应的数值分析

为探讨大直径灌注桩套管在高频振动贯入时管端土塞效应的形成机理,采用三维颗粒离散元法进行了数值仿真分析,研究了贯入过程中套管内、外土颗粒的位移、速率与接触应力、土塞高度、孔隙率和土体剪应力的变化.仿真结果表明:高频激振力越大,套管贯入深度越大,相应地管内土塞高度也越大,且超孔隙水压波动的最大幅度和幅值越大;土塞上部孔隙率较大,下部土体较密实.在高频振动贯入过程中,套管端沉入处的超孔隙水压幅值最大,同一时刻土塞内的超孔隙水压随深度增大;管内土颗粒在振动开始时以较小幅度上移;套管端部颗粒接触数目随贯入深度和振动频率的增大而增多,且接触应力和土体剪应力比其他区域大. 

Soil Plugging Effect of Sleeves Driven by High Frequency Hammers

In order to investigate the formation mechanism of soil plugging effect when a large-diameter bored-pile sleeve is penetrated by high frequency hammers, numerical simulation analyses were performed by using the 3D granular discrete element method. Variations in the displacements, velocities, contact stresses of soil particles inside and outside the sleeve, the height of soil plug and as well the porosity and shear stresses in soil plug with sleeve driving were investigated numerically. The numerical results show that the larger the high-frequency exciting force is, the larger the driving depth of a sleeve and the height of soil plug inside the sleeve are. At the meantime, the maximum fluctuation range and fluctuation amplitude of pore water pressure are large with the increase of the exciting force. Porosity in soil plug is larger at its top than at its lower part. During the process of the sleeve driven by a high frequency hammer, the maximum amplitude of pore water pressure appears at sleeve end. The larger the penetration depth is, the larger the pore water pressure becomes. Displacements of soil particles in the sleeve are small at the beginning. The contact number of soil particles at sleeve end raises with the increases of driving depth and vibration frequency. Moreover, contact stresses and shear stresses at sleeve end are larger than those in other regions.