基于扰动状态概念的砂土-混凝土桩接触面荷载传递模型研究

Load transfer model of sand−concrete pile interface based on disturbed state concept

基于扰动状态概念理论,考虑砂土密实度对扰动函数的影响,建立混凝土桩-砂土接触面荷载传递模型。用混凝土板表征桩侧粗糙度效应,采用大型直剪仪开展不同密实度的砂土-混凝土桩接触面力学行为的试验模拟,研究砂土密实度对混凝土桩-砂土接触面的力学特性的影响规律,分析接触面模型初始剪切系数、模型扰动参数(A和Z)对桩-砂土接触面荷载传递模型的作用机制。研究结果表明:1)混凝土桩-砂土接触面易呈现应变软化,在低法向应力条件下,混凝土桩-密砂接触面的应变软化程度最大。2)模型扰动参数Z在数值上近似等于孔隙比。模型扰动参数A越大,砂土与混凝土桩接触面的软化显著程度越大。参数A随着密实度增大而增大。随着法向应力增大,密砂的扰动参数A呈近似线性衰减,松砂和中密砂的扰动参数A近似呈双折线衰减。3)初始剪切系数k_s随着法向应力增大而增大,密实度越大,增速越快。4)基于扰动状态概念的桩-砂土接触面荷载传递模型可靠、参数的物理意义明确且易确定,能很好地表征桩-砂土接触面的应变软化及硬化等力学特征。

Based on the concept theory of disturbance state,the influence of density of sand on the disturbance function was considered,and a load transfer model was established for the concrete pile-sand interface.The effect of pile side roughness was described by concrete slabs.Large-scale direct shear tests on the pile-sand interface at different densities were carried out to investigate the influence of sand densities on the mechanical properties of the concrete pile-sand interface.The mechanisms of the initial shear coefficients and the effect of disturbance parameters(A and Z)on the load transfer model of the pile-sand interface were analyzed.The results show that:1)The concrete pile-sand interface is prone to strain softening,and the concrete pile-dense sand interface shows the greatest strain softening under low normal stress conditions.2)The model disturbance parameter Z numerically approximates to the pore ratio.The larger the model disturbance parameter A,the more significant the softening of sand-pile interface.The parameter A increases with increasing denseness.For dense sands,the parameter A decays approximately linearly with normal stress,and for loose and medium dense sands,it decays approximately birefringently.3)The initial shear coefficient ks increases with increasing normal stress,and the greater the denseness,the faster the rate of increase.4)The pile-sand interface load transfer model based on the concept of disturbance state concept is reliable,and the physical meaning of the parameters is clear and easy to determine,which can well describe the mechanical characteristics such as strain softening and hardening of the pile-sand interface.