宜兴抽水蓄能电站地下厂房锚杆承载力现场试验研究与计算方法

IN-SITU TESTING STUDY ON BEARING CAPACITY OF ROCK BOLTS AND CORRESPONDING CALCULATION METHOD

简要介绍了一次大型洞室锚杆支护设计现场拉拔试验的研究成果,内容包括所采用的拉拔试验方法和主要试验结果。给出了锚杆体轴应变测试方法及其测试结果、岩体层面夹角对锚杆受力状态的影响、岩体表面及杆端位移特征、锚杆注浆体与孔壁之间的粘结力等试验结果,并根据试验结果提出了锚杆承载力峰值剪应力计算方法。与传统方法相比,所提出的方法建立在现场试验测试结果基础上,计算中考虑了锚杆体上剪应力不均匀分布的特点,锚杆长度按张拉段与锚固段之和计算,锚杆承载能力按杆体上的峰值剪应力计算,计算结果可较好地反映锚杆的实际受力状态。

The research achievements of in-situ tensile test on the bearing capacity of rock bolts for support of large-scale excavation are presented. The different methods of in-situ tensile test for bolts are discussed. Based on the test results,the distribution characteristics of axial strain along the anchored part and the displacements on bolts head and adjacent rock mass surface are given out. The influence of the dip angle of rock bedding planes on the stress of rock bolts and the coherence between grout and bolt are analyzed. At last,a new method is proposed to determine the bearing capacity of rock bolts. This method is far different from conventional methods. This method is derived from the in-situ test data and the uneven distribution characteristics of shear stress along the bolt are considered. The length of bolt is determined by the stressed part and the anchored part. The bearing capacity of rock bolts is calculated by the peak shear stress along bolt. The calculated results by the method are in accordance with the real force condition in bolting engineering.