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现浇X形混凝土桩(简称X形桩)是为了更好地满足沿海、沿江软土地基处理应用而开发的一种新桩型。该新型桩具有比表面积大、侧向摩阻力高,施工便捷,经济效益高等技术经济优势;但针对其在复合地基中桩-土荷载传递规律特性的研究却相对较少。结合某污水处理厂软基处理工程,开展了X形桩复合地基中桩-土荷载传递规律的现场试验,测得了荷载-沉降关系,桩-土荷载分担比、桩-土应力比,以及桩身轴力等发展情况,分析了不同工况下复合地基中桩-土协调相互作用和中性点位置规律;并将等混凝土用量圆形桩和X形桩的单桩静载荷试验作为对比分析。研究结果表明,本文试验条件下复合地基中X形桩桩侧正、负摩阻力转化发生在0.2倍桩长处,桩侧正摩阻力最大值约为其负摩阻力最大值的140%;相同桩长情况下桩-土应力比随竖向荷载等级增长速率随桩间距的增加而减小。
Cast-in-situ X-shaped concrete piles (X-shaped pile for short) is to better meet the coastal, coastal soft soil foundation treatment and application of a new type of pile. The new pile has the advantages of large specific surface area, high lateral frictional resistance, convenient construction and high economic benefit. However, few studies have been done on the characteristics of pile-soil load transfer in composite foundations. Combined with the treatment of soft ground in a sewage treatment plant, a field test of pile-soil load transfer in X-shaped pile composite foundation was carried out. The relationship between load-settlement, pile-soil load sharing ratio, pile-soil stress ratio Axial force and other development situations, the interaction of pile-soil interaction and neutral point position in composite foundation under different working conditions are analyzed. The static load test of the single pile of circular concrete piles and X-shaped piles is compared as a comparative analysis . The results show that under the experimental conditions, the positive and negative frictional resistance transformation of X-shaped pile in composite foundation takes place at the length of 0.2 times the pile, and the maximum value of positive friction resistance at pile side is about 140% of the maximum negative friction resistance. Under long conditions, the pile-soil stress ratio decreases with the increase of pile spacing with the increase of vertical load level.