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为建立适合黄河中下游以中密~密实粉土、粉细砂及可塑~硬塑粉质黏土为主要冲积地层条件的大直径钻孔桩承载变形计算分析方法,基于郑州市三环快速路工程6个场地18根试桩现场试验结果,在分析桩侧摩阻力和桩端阻力随桩土相对位移和桩端位移发挥规律的基础上,建立大直径钻孔桩桩侧荷载传递模型和桩端承载模型,并给出计算参数取值;通过工程实例计算分析验证计算方法的可行性与合理性,在此基础上,改变桩径、桩长等参数,进一步计算分析该场地条件下大直径钻孔桩承载及变形规律。结果表明:大直径钻孔桩桩径越大,Q-s曲线拐点越明显;荷载较小时,增加桩径对提高大直径钻孔桩承载变形性能的影响更显著;大直径钻孔桩承载性能的提高幅度随桩长增大明显减小,通过增加桩长来提高大直径钻孔桩承载性能存在有效性之问题;未注浆大直径钻孔桩呈现较明显的刺入破坏模式,桩径越大,桩长越小,发生刺入破坏时桩顶沉降变形越小;桩端后注浆可提高大直径钻孔桩有效桩长,随桩长及桩径增大,提高单桩极限承载力量值越大。
In order to establish a method to calculate the bearing deformation of large diameter bored piles which is suitable for medium-density, fine silt, fine sand and plastic-hard plastic silty clay in the middle and lower reaches of the Yellow River as the main alluvial stratum, Based on the field test results of 18 test piles in 6 venues, based on the analysis of the frictional resistance of pile side and the resistance of pile tip with the relative displacement of pile and soil and the displacement of pile tip, the load transfer model and pile tip Bearing the model and given the value of the calculation parameters. Through the calculation and analysis of the engineering example, the feasibility and rationality of the calculation method are validated. On the basis of this, the parameters such as pile diameter and pile length are changed, and then the large diameter drill Piling bearing and deformation law. The results show that the larger the diameter of large diameter bored pile, the more obvious the inflexion point of Qs curve. When the load is small, the increase of pile diameter has more significant effect on increasing the bearing capacity of large diameter bored pile. The bearing capacity of large diameter bored pile increases The amplitude increases obviously with the increase of the pile length. It is effective to increase the bearing capacity of the large diameter bored pile by increasing the length of the pile. The unperforated large diameter bored pile shows the obvious puncture failure mode, , The smaller the pile length is, the smaller the deformation of pile top will be when piercing is broken. The post-pile grouting can increase the effective pile length of large diameter bored pile and increase the ultimate bearing capacity of pile with pile length and pile diameter increasing The bigger