Abstract
In this paper, the mechanism of the interface dilatancy of cement mortar rockbolts is studied based on the phenomenon of splitting failure of samples with a high sand content in the grouting material in laboratory tests. A conceptual model of the interface layer is used to explain the dilatancy mechanism of the interface. Based on the thick‐walled cylinder theory, the causes of splitting failure of the samples are analyzed. By using the numerical simulation method, the influences of different dilatancy angles of the interface layer on the interface shear stress and the radial stress are analyzed. The results show that the sand content of the grouting material has a substantial effect on the bearing capacity of the rockbolt. The higher the sand content in the grouting material is, the more obvious the interface dilatancy will be, and the greater the radial stress generated by dilatancy will be, which will produce a higher bearing capacity of the anchorage system. Under the same load, the maximum shear stress of the interface layer increases with increasing dilatancy angle. Similarly, the larger the dilatancy angle of the interface layer is, the greater the radial stress caused by dilatancy will be. Away from the interface layer, the radial stress decays rapidly. The influence range of the radial stress caused by dilatancy is mainly in the interface layer and the rock nearby.
Highlights
Grouted bolts have been widely used in underground engineering applications
There is no restraint around the sample, the failure load of the sample is not consistent with the real bearing capacity of the anchorage system
In this paper, according to the phenomenon of radial splitting of the samples found in the laboratory model test, the mechanism of the interface dilatancy of cement mortar rockbolt is studied. e primary conclusions are summarized as follows: (1) e sand content of the grouting material has a substantial influence on the ultimate pull-out force of the anchorage system
Summary
Grouted bolts have been widely used in underground engineering applications. Such bolts mainly provide the support force through the shear stress between the bolt and the grout and between the grout and the surrounding rock. Is research focuses on cement mortar grouted rockbolts. It is well known that the determination of the anchorage length is one of the most important problems in the design of anchorage structures. E key for determining the anchorage length is to obtain the shear stress at the interface of the anchorage structure. Erefore, it is of great importance to accurately determine the shear stress distribution at the interface for the prediction of the ultimate bearing capacity of the grouted rockbolt [4]. In the current code for the design of anchorage structure (BS 8081:2015), it is still assumed that the interface shear stress is uniformly distributed, both theory and experiment show that the distribution of the interface shear stress is nonlinear
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