注浆支盘式锚杆拉拔试验及极限承载力计算

Pull-out test and ultimate bearing capacity calculation of grouting branch-type anchor

注浆支盘式锚杆是自主研发的一种新型锚杆,具有广阔的应用前景。为了探究支盘式锚杆的承载特性,构建室内试验模型,针对不同的埋置深度、支盘直径和双支盘间距等条件进行拉拔试验,获取相应的荷载-位移曲线,并对部分数据采取无量纲化处理得到埋深比与荷载系数关系曲线,最后通过简化力学模型推导出支盘式锚杆的端阻力与拉拔极限承载力的计算公式。研究结果表明,埋置深度与极限承载力呈非线性关系且存在临界埋深;盘径对抗拔承载力的影响最为显著,与极限承载力呈线性增长关系,极限承载力较普通锚杆提高了2~5倍多;双支盘的分界间距为4倍支盘直径时可充分调用双支盘的承载力,由于双支盘锚杆在加载初期时土体主要为剪切变形,故其荷载-位移曲线开始阶段斜率较单支盘锚杆要大得多;埋深比与荷载系数关系曲线的斜率突变点为临界埋深比,其值为3.02;该计算公式所得结果与4组试验结果基本一致,验证了计算公式的有效性。研究结果对支盘式锚杆的设计和工程应用具有重要的理论及实际意义。

Branch-type anchor is a new type of bolt independently developed by the authors,which has broad application prospects.In order to explore the load-bearing characteristics of branch-type anchors,an indoor test model was constructed,and a series of pull-out tests was carried out for different embedding depths,branch diameters,and double-branch spacing.The corresponding load-displacement curves were obtained,and non-dimensional processing for part of the data was conducted to obtain the relationship curve between the buried depth ratio and the load factor.Finally,a simplified mechanical model was used to derive the calculation formula for the end resistance and the pull-out ultimate bearing capacity of the branch-type anchor.The research results show that there is a nonlinear relationship between the embedment depth and the ultimate bearing capacity,and a critical embedment depth exists.The plate diameter has the most significant impact on the pull-out bearing capacity,which has a linear growth relationship with the ultimate bearing capacity.The ultimate bearing capacity is 2-5 times higher than that of a straight bolt.The bearing capacity of the double plate can be fully used when the separation distance of the double plate is 4 times of the plate diameter.Since the soil is mainly sheared at the initial stage of loading,the initial slope of the load-displacement curve of the double-branch anchor is much larger than that of the single-branch anchor.The sudden change point of the slope of the relationship between the embedment depth ratio and the load factor is the critical embedment ratio,which is 3.02.The results obtained by this formula are basically consistent with those of the four testing groups,which verifies the validity of the calculation formula.The research results have important theoretical and practical significance for the design and engineering application of the branch-type anchor.