直锚式涨壳锚杆抗拔特性现场试验研究

Field experimental study on the pull-out characteristics of straight anchored expanded shell bolt

普通锚杆在承受拉拔荷载时受力不均匀易发生杆体拔出破坏,因此涨壳式锚杆等新型锚杆逐渐得到了研发应用。本研究在强-中风化和中风化两种场地下,对36mm和52mm直径的普通锚杆和自制涨壳锚杆进行了现场拉拔试验,研究了场地类型、锚杆直径及是否涨壳等因素对锚杆拉拔承载力的影响。并进一步通过构造小波函数对粘结应力随深度变化曲线进行了模拟,探讨了涨壳式岩石锚杆的传力机理。发现涨壳式锚杆由于增加了锚杆端部与岩石之间的嵌固力,改善了锚杆的轴力分布,可以很好地避免杆体拔出破坏,显著提高了岩石锚杆基础拉拔承载力。

In view of the fact that the force in ordinary rock bolt is not uniform when it bears the pull-out load and is easy to failure in the bar,some new types of bolts such as expanding shell bolt are gradually developed and applied.In this paper,the in-situ pull-out tests of ordinary anchor and self-made expanding shell anchor bolt with diameter of 36mm and 52mm were carried out in two different site of highly decomposed and moderately decomposed ground.The influence of site category,bolt diameter and shell expansion on the pull-out bearing capacity of anchor rod was studied.Furthermore,the change curve of bond stress with depth was simulated by constructing wavelet function.The force transfer mechanism of rock bolt with expansion shell was discussed.It is found that the axial force distribution of the bolt would be improved due to the embedded force between the end of the bolt and the rock.Thus the expansion shell bolt can avoid the pull-out failure of the rod and significantly improve the pull-out bearing capacity of the rock bolt foundation.