锚固结构荷载传递机理离散元模拟研究

DEM Numerical Simulation Research on the Load Transfer Mechanism of Anchorage Structure

研究目的:岩土锚固技术是岩土工程领域的重要分支,被广泛应用于土木、矿山、水电等工程领域,但关于锚固结构荷载传递机理的细观力学研究相对较少。本文依据现场试验,通过建立锚杆拉拔试验颗粒流数值模型,探讨不同荷载作用下轴力、锚固界面剪应力分布特征以及周边岩土体的细观力学特性。研究结论:(1)建立了锚杆张拉试验颗粒流数值模型,通过将计算结果与试验数据进行对比,验证了模型的合理性与有效性;(2)分析了锚固结构的荷载传递机理,其界面剪应力沿锚杆方向的分布是不均匀的:在弹黏性阶段,锚固界面剪应力以及轴力分布均为单调递减曲线;在弹塑性阶段,界面剪应力峰值点大致位于弹塑性变形区和弹黏性变形区的分界位置,并且随着张拉荷载的逐渐增大,界面剪应力峰值不断增大,峰值点不断向远端推移;(3)无论是在重力作用下还是受到拉拔荷载时,锚孔周边岩土体的强力接触力和弱力接触力基本垂直,在受到拉拔荷载时,周边岩土体的颗粒会发生重排列,导致强力接触力与弱力接触力方向产生强烈偏转;(4)本文研究方法与结论可为类似锚固结构的设计与力学分析提供理论借鉴。

Research purposes: Geotechnical anchoring is an important branch in geotechnical engineering. It has been widely used in civil engineering,mining,hydropower and other engineering filed. However,the study on mesoscopic load transfer mechanism of anchorage structure is still lack. The particle-flow simulation model is established based on field test in this paper and the features of the axial force and shear stress distributions along the anchor rod and meso-mechanical feature of surrounding rock and soil mass is fully analyzed.Research conclusions:( 1) The simulation model of anchorage structure is established and the validity of simulation model is verified by comparing the experiment data obtained from on-site pullout test and the simulation mode.( 2) The load transfer mechanism of anchorage structure is analyzed,and the distribution of interfacial shear stress along the direction of anchor is uneven: at elastic-viscous stage,the distribution of the interfacial shear stress and the axial force are monotonic decreasing curves;at the elastic-plastic stage,the peak value of the interfacial shear stress is located at the boundary between the elastic-plastic deformation area and the elastic-viscous deformation area,and with the increase of the pullout load,the peak value of the interfacial shear stress increases and the peak value point moves to the anchor end.( 3) No matter by gravity or by the pull-out load,the strong contact force is perpendicular to weak contact force between soil particles. The soil particles of the surrounding anchor hole will rearrange by the pull-out load,which results in a strong deflection of the strong contact force and the weak contact force direction.( 4) The simulation method and results of this paper have some reference value for design and mechanical analysis of similar anchorage structure.