楠竹加筋复合锚杆静力学性能试验研究

楠竹加筋复合锚杆是一种专门为土遗址加固而发明的新型锚杆,目前关于其力学性能研究尚不系统。本研究设计了单轴压缩试验、拉拔试验和三点弯曲试验,测试复合锚杆的静力学指标,分析锚杆的工作性能,为加固工程设计提供理论依据。压缩试验表明,径高比为1∶1和1∶2的复合锚杆试件的抗压强度分别是72.08MPa和43.48MPa,弹性模量分别是5.29GPa和5.25GPa。试件的压缩破坏形式是,带箍筋时发生散裂,不带箍筋时发生腰折破坏。拉拔试验表明,钢绞线受拉时复合锚杆内部界面上存在剪切应力峰,随着轴向荷载的逐渐增大,剪应力峰逐渐从邻近加载端向远离加载端的方向移动,平均最大剪切应力与锚杆长度呈指数关系。弯曲试验表明,复合锚杆试件弯曲过程中,内黏结剂与竹子界面剪切滑移变形大于钢绞线与内黏结剂界面的变形,过大的界面滑移和材料断裂是导致弯曲破坏的原因。研究认为,楠竹复合锚杆压缩强度较高,界面剪切强度较低,提高锚杆整体性能的措施包括增设端部锚定板、提高内黏结剂强度、提高钢绞线表面粗糙度等。建议锚杆吊装时宜多点捆绑,尽量保持直线状态,最大弯曲率不得超过2%。

Laboratory study of the static properties of bamboo-steel cable composite anchor

The bamboo-steel cable composite anchor(BSCC anchor) is a newly designed anchor for reinforcement of earthen archaeological sites.Three types of laboratory tests,including compression test,pulling test and bending test,were conducted to measure the static parameters so as to illustrate the working mechanism of the anchor.Compression test indicated that the specimens with diameter-to-height ratios of 1∶ 1 and 1∶ 2 have compressive strength 72.08MPa and 43.48MPa,and elastic modulus 5.29GPa and 5.25GPa,respectively.It was observed that the specimens fractured in a pattern of vertical racking or lateral bulging with or without a buckling hoop attached.Pulling test indicated that a shear stress peak along the internal interfaces appeared near the end of the loading,which was shifted far away from the loading end while axial load increased.An exponential relation was found between the average max shear stress and the anchor length.Bending test indicated that the deformation at the interface of bamboo and steel strand was larger than that at the interface of inner binder and steel strand,and the bending failure was occurred due to large interface sliding and material rupture.This study illustrates that BSCC anchor has higher compressive strength but lower shear strength along the internal interfaces.It is suggested that BSCC anchor can be improved by various measurements such as setting an end plate for the steel strand,increasing the strength of inner binder,and increasing the surface roughness of steel strand,etc.It is suggested that a BSCC anchor should be kept in a straight state when hoisted for installation,no bending greater than 2%.