Investigation of the Anchorage Head Characteristics

摘要

From previous studies undertaken by the author the influence of the anchorage head assembly characteristics on the dynamic response of ground anchorage systems has been shown to be significant. The anchorage head assembly consists of a bearing plate and stressing nut for the case of rock bolt anchorages, the type of anchorage considered in this paper. Furthermore, the rock surface that the bearing plates are usually placed against may be different. It can vary from smooth concrete surfaces to the very rough surfaces found in tunnel walls and roofs. When the anchorages are tested using the GRANIT dynamic testing technique initial testing requires the use of a load cell to monitor the load which will change the characteristics of the anchorage head assembly. A lumped parameter model, developed to observe and understand the behaviour of ground anchorage systems when subjected to a dynamic load addresses the influence of the anchorage head assembly characteristics on the dynamic response. From the results from each of the anchorage components, obtained from the model it appears that the most influential part of the anchorage system with respect to the detection of the load is the anchorage head assembly. In order to investigate how changes in the bearing plate characteristics influence the response of anchorage system, a number of bearing plates were constructed and tested using the anchorage head rig specially designed for these tests. The investigation of the influence of the shape and dimensions of bearing plates is the subject of this paper and is shown to have a significant role in determining the dynamic behaviour of ground anchorages. Furthermore different degrees of the roughness of the surface that bearing plates are placed against are examined for the influence on the anchorage head characteristics.