【摘要】 基于入和没入硬层时有限元数值模拟对比分析和持力层不同时同场地现场对比试验资料分析,对大直径超长灌注桩的承载潜力问题进行了探讨.结果表明:(1)大直径超长桩入和没入桩端硬层时其承载性能会有很大区别.桩入硬层后其承载力大大提高,其极限承载力为没入硬层的3.8倍以上;(2)通过桩底注浆使持力层强度提高后,大直径超长桩的承载力大大提高.和注浆前相比,注浆后桩的承载力提高了0.27—1.0倍以上.和非注浆的桩相比,注浆桩的承载力为非注浆桩的1.25—1.61倍以上;(3)有好的天然持力层时,应设法使大直径超长桩进入该持力层;无好的天然持力层时,可进行人工桩底注浆使桩端岩土层强度提高;(4)当大直径超长桩有了好的持力层后,应使桩顶的沉降尽可能的大,这样可使桩的承载潜力充分地发挥出来.更多还原

【Abstract】 Based on the field loading tests and FEM numerical simulation analysis,the paper probes into the potential bearing capacity of large diameter and super-long bored-cast-place piles.Conclusions are drawn as follows:Firstly,the bearing behavior is different greatly when the pile penetrates into hard soil layer and when it does not.The bearing capacity of the pile is increased greatly—its bearing capacity being 3.8 times as much as the pile that doesn’t penetrate into hard soil layer. Secondly,the bearing properties of large diameter and super-long bored-castplace piles is improved greatly after the bearing layer is reinforced by pile bottom grouting.The bearing capacity of pile after the bottom grouting is 0.27—1.0 times greater than the pile’ that precedes bottom grouting.The bearing capacity of grouting piles is 1.25—1.61 times as much as that of the non-grouting piles.Thirdly,when there is a strong natural bearing layer, the large diameter and super-long bored-cast-place piles would penetrate into the bearing layer.When there isn’t strong natural bearing layer,the bearing properties of pile end soil layer can be enhanced through pile bottom grouting.Finally,with a strong bearing layer,the tip settlement of large diameter and super-long bored-cast-place piles should be as large as possible in order to bring the bearing capacity of pile into fully play.更多还原