加卸载条件下砂浆锚杆力学响应试验研究

Experimental study on mechanical response of mortar anchor-bolt under loading-unloading condition

围绕全长黏结砂浆锚杆加卸载力学响应问题,利用自主研发的拉拔试验系统,开展了各级拉拔力水平下锚固在不同刚度套筒中锚杆系统的加卸载拉拔试验,监测拉拔过程中锚杆轴向应变和套筒外壁周向应变的变化,分析试验过程中锚杆杆体-砂浆界面剪切力分布及演化规律,并探讨了套筒刚度和加卸载作用对锚杆系统力学响应的影响。试验结果表明:试验过程中拉拔力、杆体轴向应变、套筒周向应变随拉拔位移的变化规律相同,整体呈先上升后下降的趋势;加卸载阶段,轴向应变、周向应变与拉拔力同步变化,随卸荷点荷载增加,滞留位移逐渐增大;沿着锚杆轴线方向界面剪切力分布不均匀,锚杆杆体-砂浆界面出现解耦后,剪切力峰值逐渐向杆体内部传递。试验成果能够弥补相应加载路径下研究的不足,同时也能够为类似工程现场提供参考。

Around the loading-unloading mechanical response of the full-length cemented mortar anchor-bolt,the loading-unloading pulling-out experiments on the anchor-bolt system inside the anchor-bolt sleeves with different stiffnesses under all the pulling-out force levels are carried out by means of a self-developed pulling-out experiment system for monitoring the changes of both the axial strain of the anchor-bolt and the circumferential strain of the sleeve outer wall during the pulling-out process,from which the shear force distribution and evolution laws of the interface between the body of anchor-bolt and the mortar during the experiment are analyzed,while the influences from the stiffness of the sleeve and the loading and unloading effects on the mechanical response of the anchor-bolt system are discussed as well.The experiment results show that the changing laws of the pulling-out force,the axial strain of the bolt body and the circumferential strain of the sleeve are the same along with the pulling-out displacement during the experiment process and generally exhibit the trends of increasing at first and then decreasing.During the loading-unloading phase,the axial strain and the circumferential strain change synchronously,while the residual displacement gradually increases along with the increase of the load at the unloading point.Along the axial direction of the anchor-bolt,the shear force at the interface is non-uniformly distributed,while the peak shear force is gradually transmitted into the bolt body after the decoupling of the bolt-mortar interface.The experiment results can not only make up the deficiency of the study made under the condition of the corresponding loading-unloading path,but also can provide some references for the similar project concerned.