快速拉格朗日法在锚杆拉拔数值模拟试验方面的运用

为研究主要影响锚杆锚固力的因素、锚杆在拉拔过程中整体失稳的规律等,采用三维显式有限差分法,建立锚杆拉拔数值仿真模型,进行计算机模拟。结果表明:数值模拟计算的结果和现场试验得到的结果基本吻合,表明数值模拟锚杆拉拔过程是可行的;锚杆的拔出过程是逐渐滑移到突然整体失稳的过程;锚杆的锚固效应随着锚固剂与锚杆间的摩擦角、粘结力和浆体有效围压的增加而增强;锚固剂所受的剪切应力分布规律随锚杆拉拔过程而改变,在拉拔初始时,自由端锚固剂处的剪切应力为最大,锚固端处的剪切应力为最小且接近为零,随着锚杆拉拔过程的进行,自由端处锚固剂与锚杆的界面首先达到屈服点,使自由端处锚固剂与锚杆之间产生滑移现象,而后锚固剂所受的剪切应力慢慢呈现均匀分布,并达到最大值(在锚固剂与锚杆的界面上达到屈服),锚杆出现整体失稳;在锚杆的拉拔过程中,锚杆自由端处的变形量最大,从自由端至锚固端,锚杆的变形量逐渐减小;锚固剂的变形规律与锚杆的变形规律相同。

The Application of Fast Lagrangian Method to the Numerical Simulation of Anchor Bolt Pull-out Tests

The major influential factors of the anchorage force and the law of whole instability in the course of pull-out tests for anchor bolt are studied by means of numerical simulation using the 3D explicit finite difference methods.The results show that the numerical simulation results basically tally with the results of pull-out field tests,which shows that it is feasible to numerically simulate the pull-out process of the anchor bolt.The pull-out process of the anchor bolt is from gradual slippage to whole instability abruptly.The anchorage effect of the anchor bolt boosts up along with the augment of friction angle between the anchorage agent and the anchor bolt,the cohesive force and the effective surrounding pressure of slurry.The distribution regularity of the shear stress on the anchorage agent changes with the process of the anchor bolt pull-out.At the initial stage of pull-out tests,the maximum shear stress appears at the free end of the anchorage agent.On the contrary,the shear stress of anchorage agent at the anchorage end is minimum and almost zero.Along with the pull-out tests for anchor bolt,the interface of the anchorage agent at the free end and the anchor bolt attains the yield point first,which results in the slippage between the anchorage agent at the free end and the anchor bolt.Then the shear stress on the anchorage agent takes on slowly homogeneous distribution and reaches the maximum(yield arrives at the interface of the anchorage agent and the anchor bolt). The anchor bolt becomes overall instable.During the process of anchor bolt pull-out,the deformation of the anchor bolt at the free end is the largest.The deformation of the anchor bolt diminishes gradually from the free end to the anchorage end.The deformation regularity of the anchorage agent is the same as that of the anchor bolt.