基于沉桩模拟试验的装配式地下连续墙沉桩阻力评估方法

Jacking resistance evaluation method of prefabricated diaphragm wall based on laboratory experiment

装配式地下连续墙采用工厂预制、现场沉桩施工快速,具有施工文明、环境污染小的特点,是我国城市轨道交通基坑支护领域的重要发展方向。装配式地下连续墙现场施工的关键在于大截面预制板桩沉桩过程的控制,沉桩设计中需综合考虑沉桩阻力计算及预成槽泥浆状态的控制问题。针对装配式地下连续墙沉桩阻力的评估计算,通过模型桩室内沉桩试验系统研究了不同预成槽泥浆状态下的桩侧摩阻力、桩端阻力分布规律,提出了装配式地下连续墙自重沉桩及预压沉桩情形下的预成槽泥浆状态控制标准确定方法。结合预成槽模型桩室内沉桩试验结果,建立了装配式地下连续墙沉桩阻力评估模型,提出了预成槽泥浆状态控制范围,开发了预制桩沉桩可行性评估软件。其中,1.2m标准幅预制桩自重沉桩的泥浆密度不应超过1.15 g/cm^3,300 kN预压沉桩不应超过1.33 g/cm^3。

Prefabricated diaphragm wall is constructed through factory prefabrication and site jacking, which is more civilized and environmentally friendly, and it is an important research direction in rail transit pit support engineering in China. The key for the construction of prefabricated diaphragm wall is the jacking process control of the sheet pile with large section. During the design stage, it is particularly important to consider how to evaluate jacking resistance and perform slurry control. In order to evaluate the jacking resistance of prefabricated diaphragm wall, a series of model pile experiments is conducted. From which, lateral resistance and tip resistance of different preformed slurry situations are studied. With the experimental results, preformed slurry control standard is proposed for prefabricated diaphragm wall deadweight and preloading jacking. According to the final results of the model pile jacking experiments, a jacking resistance evaluation model for prefabricated diaphragm wall is established, the reliable control standard for preformed slurry situation is determined, and the related software is developed. Our results show that for prefabricated diaphragm wall deadweight jacking with 1.2 m width, the slurry density could not exceed 1.15 g/cm^3, and for preloading jacking with 30 ton additional pressure, the slurry density could not exceed 1.33 g/cm^3.