劲性复合桩竖向承载性能现场试验与数值模拟研究

    Field test and numerical simulation of vertical bearing characteristics of stiffened deep cement mixing pile

    • 摘要: 劲性复合桩因其高承载性能、桩侧摩阻力大和沉降量小等特点,在岩土工程中被广泛应用。通过现场试验及一系列数值模拟,对劲性复合桩的承载特性进行研究。结果表明,劲性复合桩的荷载-位移曲线呈缓变型。试验结束对桩体全断面开挖后,芯桩与水泥土紧密结合未发生破坏,这表明芯桩和水泥土可以有效地协同工作;芯桩长度LC过小会使得桩顶荷载无法有效地传递到芯桩底部以下水泥土,从而导致劲性复合桩的承载性能发挥不充分;增大含芯率ω能够有效提高劲性复合桩的承载力,但当含芯率ω大于0.4时承载力增大速率变缓。最后提出一个新的桩侧摩阻力修正系数λ以单独考虑含芯率的影响,从而对规范JGJ/T 327—2014的计算方法进行修正。研究成果可为劲性复合桩的承载力计算及设计提供参考。

       

      Abstract: The stiffened deep cement mixing (SDCM) pile is widely used in geotechnical engineering because of its high bearing capacity, high skin friction and low settlement. In this paper, the bearing characteristics of the SDCM pile are investigated through field tests and a series of numerical simulations. The results show that the load-displacement curve of the SDCM pile is slow-varying. After the test is completed and the entire cross-section of the pile is excavated, the core pile is tightly bonded to the cemented soil without any damage, indicating that the core pile and cemented soil can work together effectively; the reduction of the core pile length LC prevents the load at the pile top from being effectively transferred to the cemented soil below the core pile bottom, which results in the insufficient play of the load-bearing performance of the SDCM pile; the increase of the core pile content ratio ω can effectively improve the bearing capacity of the SDCM pile, but when the core pile content ratio ω is more than 0.4, the rate of increase in bearing capacity slows down. The results of this research can provide a reference for in the calculation of bearing capacity and design of the SDCM pile. Finally, a new correction factor λ for the skin friction is proposed to consider the effect of the core pile content ratio separately, so as to correct the calculation method of the specification JGJ/T 327—2014.

       

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