苏通大桥群桩基础应力扩散角反演分析

等代墩基法是群桩沉降计算的一种简化模式,在计算超长大直径钻孔灌注群桩基础最终沉降量时,得到的理论值往往偏大,经沉降经验系数修正后其值又偏小,而且按照从外围基桩以-φ/4(-φ为平均摩擦角)来考虑应力扩散作用显然不适用于深水群桩基础沉降计算.鉴于此,利用苏通大桥地基基础安全监测系统实时在线监测数据,考虑钢护筒与桩身共同作用,采用等代墩基法模型反演不同施工阶段应力扩散角,得到荷载传递过程中应力扩散角随时间的变化规律,从而给出用等代墩基法计算深水群桩基础沉降时应力扩散角的取值范围,为桩基设计提供一定的理论依据.

Back analysis of stress diffusion angle for foundation with pile groups of Suzhou-Nantong Bridge

The equivalent pier method is a simplified model for calculating the settlement of a foundation with pile groups. However, the calculated final settlement of the foundation with super-long large-diameter drilled bored pile groups is much larger, and it is much smaller after modified by empirical coefficients. Meanwhile, it is not suitable to calculate the settlement of deep-water foundations with pile groups according to the stress diffusion angle σ~-4 (σ~- is the average friction angle) of the outside piles. Therefore, using the real-time online data of the foundation safety monitoring system of the Suzhou-Nantong Bridge and the interaction between the steel casing and the piles, the stress diffusion angle at different construction stages was back analyzed through the equivalent pier method model. The variation patterns of the stress diffusion angle over time were obtained during the load transfer process. Furthermore, the range of the stress diffusion angle was proposed for the calculation of the settlement of the deep-water foundation with pile groups using the equivalent pier method, providing a theoretical basis for the design of pile foundations.