钢绞线-水泥土粘结作用对抗拔桩传力类型的影响研究

Study on the Influence of Steel Strand-cement-soil Adhesion on the Force Transmission Type of Uplift Pile

旋喷搅拌加劲抗拔桩(HPJM-RCS桩)是一种广泛应用于工程中的抗拔桩,具有较高的承载性能。该桩的钢绞线-水泥土粘结作用影响其传力类型,使其具有不同的破坏模式和工作性能。本文提出了HPJM-RCS桩钢绞线-水泥土粘结模型,并对试验桩进行了数值模拟。研究结果表明,使用Horpibulsk经验公式计算水泥土无侧限抗压强度和ACI规范公式计算钢绞线粘结强度,可为确定这些参数提供一种有效方法;3折线粘结作用模型可用于HPJM-RCS桩的传力分析;在加载初期,该桩与拉力型抗拔锚杆的承载性能类似,锚板尚未发挥荷载分担作用;在锚板发挥作用之后,该桩属于拉压分散型抗拔桩。因此,设计时忽略钢绞线与水泥土之间的粘结应力会导致支护刚度偏低而不经济。

High Pressure Jet Grouting&Mixing Reinforced Cement-soil(HPJM-RCS)anchor pile has high uplift bearing capacity and is widely used in engineering.Adhesion between steel-strands and cement-soil affects the force transfer type of uplift piles,resulting in different failure modes and working performance.This paper proposes an adhesion model for HPJM-RCS pile and conducts numerical simulation on a test pile.Results show that the Horpibulsk empirical formula and ACI code formula can calculate unconfined compressive strength of cement-soil and bond strength of steel strands respectively,providing an effective method for determining these parameters without conducting tests.Broken line bond model can analyze force transfer of HPJM-RCS piles.At initial loading stage,the anchor plate has not yet shared the load,and the bearing capacity is similar to tensile pull-out anchor rod.After anchor plate plays its role,HPJM-RCS pile becomes tension-compression dispersion pull-out pile.Neglecting bond stress between steel strands and cement soil in design will result in low support stiffness under normal service load level,which is uneconomical.