Performance and working mechanism of tension–compression composite anchorage system for earthen heritage sites

Although the fully grouted tension anchorage system (T-anchorage system) has been widely used in the field of anchoring of earthen heritage sites, it has always suffered from the failure of the bolt–slurry interface debonding and the strong attenuation of the shear stress of the bolt–slurry interface along the embedment length. In this article, a new type of fully grouted tension–compression composite anchorage system (TC-anchorage system) is proposed, which is made up of a pressure bearing system with the same diameter of the anchor hole at the end of the tension bolt. The in situ anchorage, pull-out test and interfacial stress–strain monitoring were carried out for the T-anchorage systems and the TC-anchorage systems. This was based on the preliminary analysis and comparison of the structure and working mechanism of the two anchorage systems. The test results show that: the average ultimate load of the TC-anchorage system is about 40% higher than that of the T-anchorage system. TC-anchorage systems have the characteristics of small elastic deformation and large plastic deformation. The strain at the bolt–slurry interface varies progressively along the embedded length with the increase of load in a positive skewness–bimodal–negative skewness curve. The working mechanism of TC-anchorage systems includes three progressive stages: bolt–slurry interface debonding, conical slurry formation and slurry extrusion. The research conclusion provides a reference for the application of TC-anchorage systems in the protection and reinforcement of earthen heritage sites.