预应力锚杆拉拔力学特性及临界锚固长度研究

Study on pull-out mechanical characteristics and critical anchorage length of prestressed anchor bolts

相较于非预应力锚杆而言,预应力锚杆在受到拉拔作用后呈现出特殊的支护力学特性。为深入探明预应力锚杆的这一特点,采用足尺室内实验和理论分析的方法研究预应力锚杆在受载后的力学响应情况,掌握预应力锚杆的支护力学特点及其机制,进一步丰富和扩展了预应力锚杆的主动支护理论,并从锚固系统支护效果最优化的角度出发,基于二次开发手段提出一种预应力树脂锚杆临界锚固长度的数值计算方法。结果表明:(1)预应力施加后锚杆的荷载-位移曲线形态发生了明显变化,在前期支护刚度增加,同时出现荷载突变点,且随着预应力施加量值的增加,突变点处荷载从17.3 kN增加至54.6 kN;(2)预应力锚杆在受载后呈现出“先刚后强”的支护力学特性,在支护前期能够迅速达到较大的承载力,有效提高锚杆控制围岩变形的能力;(3)建立的数值分析模型很好地再现了锚固系统在受到拉拔荷载时的力学响应情况,基于该模型分析了不同锚固长度条件下锚固系统的承载能力峰值,确定了该实验条件下树脂锚杆的临界锚固长度为44 cm。相关研究成果对认识预应力锚固系统的支护力学特性和参数设计具有指导意义。

Compared with the non-prestressed bolt,the prestressed bolt shows special supporting mechanical characteristics after being pulled out.In order to deeply investigate this characteristic of the prestressed bolt,the full-scale indoor experiments and theoretical analysis were used to study the mechanical response of the prestressed bolt after being loaded,and the supporting mechanical characteristics of the prestressed bolt and its mechanism were further understood,which further extended the active support theory of the prestressed bolt.Additionally,from the perspective of optimizing the support performance of the anchorage system,the numerical calculation method for the critical anchorage length of the prestressed resin bolt was proposed based on the secondary development mean.The results showed that:(1)After the prestress was applied,the shape of the load-displacement curve of the bolt changed obviously,the support stiffness increased in the early stage,and the load mutation point appeared at the same time.With the increase of prestress application value,the load value at the mutation point increased from 17.3 kN to 54.6 kN;(2)The prestressed bolt exhibited an initial increase in stiffness after being subjected to the tensile load,followed by an increase in strength in support mechanics,quickly providing the larger bearing capacity in the early stage of support and effectively improving the ability of the anchorage system to control the deformation of the surrounding rock;(3)The established numerical analysis model well reproduced the mechanical response of the anchorage system under the tensile load,based on which the peak bearing capacities of the anchorage system under different anchorage length conditions had been analyzed,and the critical anchorage length of the resin bolt under this experimental condition had been determined to be 44 cm.The relevant research results have guiding significance for understanding the support mechanical characteristics and parameter design of prestressed anchorage systems.