An analytical solution for the critical anchorage length of grouted rockbolts
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GMGDA 2019
An analytical solution for the critical anchorage length of grouted rockbolts Yubao Zhan 1 & Jun Zhang 1 & Nan Li 1 & Pengqiang Zheng 1 & Hui Wang 1 & Qingbiao Wang 1 Received: 6 June 2020 / Accepted: 13 August 2020 # Saudi Society for Geosciences 2020
Abstract Determining the critical anchorage length of grouted rockbolts is of great theoretical and practical value for the design of anchorage structures. First, the elastic solution for the critical anchorage length is derived according to the shear stress distribution of the anchorage-body interface, and the factors affecting the critical anchorage length are analyzed. Second, the critical anchorage length and its influencing factors are analyzed by a numerical simulation and compared with the theoretical results. In addition, the accuracy of the critical anchorage length is verified by the field test results. Finally, based on the analysis of the safety degree and the field test, the determination of a reasonable anchorage length is discussed. It is shown that the critical anchorage length of the grouted rockbolt in the elastic state is not related to the pullout load but only to the mechanical properties of the rock and the anchorage-body diameter. The softer the rock is, the longer the critical anchorage length is. With the increase in the anchorage-body diameter, the critical anchorage length is longer. The Poisson’s ratio of the rock has little effect on the critical anchorage length. Moreover, the research also shows that the reasonable anchorage length of the grouted rockbolt determined in this study is economical and can meet the safety requirements for engineering applications. Keywords Grouted rockbolt . Critical anchorage length . Reasonable anchorage length . Analytical solution . Numerical simulation
Introduction Rockbolts have been widely used in mining and civil engineering in the past 50 years. However, the design of the grouted rockbolt has obviously lagged behind its application. One of the core and key elements of the grouted rockbolt design is the determination of the anchorage length. The determination of a reasonable anchorage length not only is related to the safety of the grouted rockbolt but also has an important impact on the cost of the anchorage project, which is a very important issue in anchorage theory research. Understanding the critical anchorage length has been a longterm process. In the design of the grouted rockbolt, the This article is part of the Topical Collection on Geological Modeling and Geospatial Data Analysis * Yubao Zhan [email protected] 1
College of Resources, Shandong University of Science and Technology, Tai’an 271019, China
assumption of the average stress distribution was questioned first. Later, many studies have shown that with increasing load, the interfacial shear stress will move to the depth of the anchorage segment, but the bearing capacity of the grouted rockbolt has not been substantially improved. Scholars have gradually realized that there is an anchorage length in the grouted rockbolt.
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