粉质黏土中静力沉桩过程产生的孔压试验研究

静压管桩在实际工程中有着广泛应用,桩-土界面超孔隙水压力对静压桩的工作性能有着巨大影响。目前的研究多集中于桩周土中超孔隙水压力的分布,缺少对桩-土界面处应力的真实情况的研究。通过在桩身开孔、嵌入硅压阻式孔隙水压力传感器的方法,在黏性土体中开展了2组模型桩的室内静力压桩试验,对桩-土界面的孔隙水压力、超孔隙水压力的变化规律进行了研究。试验结果表明:利用硅压阻式传感器首次成功监测了沉桩过程中桩-土界面产生的孔隙水压力;2根试桩在沉桩过程中产生的桩-土界面孔隙水压力、超孔隙水压力均随着沉桩深度的增加而增大;同时2根试桩沉桩过程中产生的超孔隙水压力均较大,最大可达4.21 kPa,约为上覆有效土重的75%,在实际工程中需对沉桩过程中产生的较大超孔隙水压力加以重视;同一深度处的超孔隙水压力存在消散现象,随着深度的增加,消散程度逐渐减小;在实际工程中,需采取有效措施,防止超孔隙水压力过大。试验结果可为静压桩施工和桩-土界面理论研究提供参考。

Laboratory Study on Pore Water Pressure During Static Indentationof Pile in Silty Clay

Jacked pipe has been widely used in practical engineering. The excess pore water pressure at the pile-soil interface has a great influence on the performance of jacked pile. Most current researches focus on the distribution of excess pore water pressure in the soil around the pile rather than the real situation of stress at the pile-soil interface. In this paper, by drilling holes in pile body and embedding silicone piezo-resistance pore water pressure sensor, static pile pressure test was conducted on two groups of model piles in clayey soil. The variations of pore water pressure and excess pore water pressure at the pile-soil interface were investigated. The pore water pressure generated at the pile-soil interface during pile jacking has been successfully monitored for the first time by the silica-piezo-resistance sensor. The pore water pressure and excess pore water pressure of pile-soil interface both increased with the growth of pile jacking depth. In the meantime, the excess pore water pressure generated in the process of pile jacking was relatively large, up to 4.21 kPa, which was about 75% of the effective overburden soil weight. In practical engineering, the relatively large excess pore water pressure generated in the process of pile jacking should be paid attention to. The excess pore water pressure at the same depth dissipated, and such dissipation attenuated with the increase of depth. In practical engineering, effective measures should be taken to prevent from excessive excess pore water pressure. The test results offer reference for static pressure pile construction and theoretical research on pile-soil interface.