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随着海洋平台上部结构的增大,大直径超长的钢管桩越来越多的被应用于实际工程当中。在打桩过程中,往往会因为各种原因而造成停锤。停锤后打桩的再起动问题是一个决定桩基能否打入到设计深度的关键问题,与桩的承载力恢复密切相关。为对这一问题有深入认识,通过对某实际打桩工程出现的问题进行研究,根据地质勘察结果,对该地区的土体特点进行了分析;根据打桩实测纪录,分析了桩端阻力和侧摩阻力对打桩影响。同时根据打桩记录和现场试验,计算了打桩过程中的实际土抗力并对土抗力随时间的变化进行了探讨。分析显示,桩的可打入性与土质条件密切相关;超大直径超长桩在打入过程中形成完全闭塞土塞的可能性不大,连续打桩中的侧摩阻力平均为静止侧摩阻力的0.68;打桩中6周的停锤,使得土抗力比连续打桩的土抗力至少增加了将近65%,停锤3个月后的土抗力超过了初始静承载力,桩的承载力随时间增长的趋势明显。
With the increase of the superstructure of the offshore platform, more and more large-diameter steel pipe piles are used in practical projects. In the piling process, often due to various reasons, stop hammer. Restarting piling after stop hammer is a key issue that determines whether piles can penetrate to the design depth and is closely related to the recovery of pile bearing capacity. In order to have a thorough understanding of this issue, this paper studies the problems that occur in a practical piling project and analyzes the characteristics of the soil in the area according to the geological survey results. According to the recorded records of pile driving, Drag on the pile impact. At the same time, based on the records of piling and field tests, the actual resistance of soil during piling is calculated and the variation of soil resistance with time is discussed. Analysis shows that the penetration of piles is closely related to soil conditions. It is not possible for the super-large-diameter super-long pile to form a completely closed plug when it is driven in. The average lateral friction in continuous piling is equal to the static lateral friction 0.68. The 6-week stop hammer in piling increased the soil resistance by at least 65% compared with that of continuous piling. The soil resistance after 3 months of stopping hammer exceeded the initial static bearing capacity, and the bearing capacity of the pile increased with time The trend is obvious.