现浇X形混凝土桩竖向承载性状模型试验研究

Model test of vertical bearing capacity of cast-in-situ X-shaped concrete piles

为研究现浇X形混凝土桩的荷载沉降特性及其荷载传递机制,利用河海大学的大型试验模型槽开展X形桩的足尺模型静载荷试验。通过在桩身设置的钢筋测力计及在桩底埋设的土压力盒,实测了在竖向荷载作用下X形桩与土相互作用时的工作性状。试验结果表明:X形桩的荷载沉降曲线为缓变型;桩侧摩阻力与桩端阻力随桩顶沉降的增加均呈递增性;但随着桩顶荷载的增加,桩侧摩阻力分担桩顶荷载比例却呈递减性,其分担桩顶荷载比例由初期的约90%下降到极限状态时的70%左右,而桩端阻力分担桩顶荷载的比例呈递增性,其分担桩顶荷载比例由初期的约10%上升到极限状态时30%左右。研究成果可为今后竖向受荷X形桩的设计与研究提供重要参考。

To study the load settlement characteristics and load-transfer mechanism of cast-in-situ X-shaped concrete piles,full-scale model pile load test of X-shaped pile is carried out by using the large-scale test trench of Hohai University.The interaction behavior of the vertical loaded X-shaped piles is obtained by means of the reinforcement stress gauges set in the pile and earth-pressure boxes embedded in the pile bottom.The experiment results show that： X-shaped pile load settlement curve is an adjustment curve;pile side friction and tip resistance show incremental development with the increasing pile settlements;but with the increase of pile top load,the ratio of pile side resistance sharing pile head load is regressive,its sharing ratio decreases from the initial load of about 90% to 70% of the limit state,while the ratio of tip resistance sharing the load is incremental,the pile top load-sharing ratio of about 10% from the initial state up to 30% of the limit.The research results are useful for the design and analysis of X-shaped piles under vertical load.