港口工程大直径管桩竖向承载力可靠性研究

Reliability study on vertical capacity of large-diameter cylinder pile in port engineering

大管桩在港口工程中应用广泛,目前对其承载力的研究还远远不够.由于影响大管桩承载力的因素很多,且多具有不确定性,文中结合港口工程预应力混凝土大直径管桩承载力经验公式,运用可靠度理论对大管桩竖向承载力加以研究,建立了桩基承载力极限状态方程,按JC法计算了可靠度指标.对某港口大管桩承载力进行可靠度计算,并对影响单桩承载力可靠性各个因素进行敏感性分析.结果表明:土的限侧阻力及桩端土极限端阻力的变异性对桩基承载力可靠度均有影响,对桩基承载力起主要作用、土质较好、较深厚的土层,其极限侧阻力的变异性对可靠度影响较大,而在诸多因素中,桩顶荷载效应以及包括计算模式在内的其他不确定性因素的变异性对桩基承载力可靠度的影响较大,尤其对计算模式的不确定性非常敏感.

Large-diameter cylinder pile is widely used in port construction. However, the current study on its capacity is not enough. There are many factors that influence its capacity, among which more are uncertain. Combining reliability theory with empirical formula for vertical capacity of large-diameter post tensioned prestress concrete cylinder pile in port engineering, the vertical bearing capacity is studied; and then capacity limit state equation is established, the reliability indexes are calculated according to JC method. Moreover, the reliability of large-diameter pile capacity in certain port is analyzed, and sensitivity analysis on the various factors affecting the reliability of pile＇s capacity is done. Results show that both the variability of ultimate shaft resistance of the shaft soils and the ultimate tip resistance of tip soil affect the reliability of the capacity, and the variability of the good thickest soil＇s ultimate shaft resistance plays a major role. Among all factors, pile top load effect and the other uncertain factors including the calculation model are great influences on the pile＇s capacity, and it is particularly sensitive to the uncertainty of computing model.