Abstract
Soil nailing has been a well accepted technique for stabilizing slopes. It is particularly useful when there is a limited working area, for example on slopes along highways, where the system can be installed directly in the slope without any major earthworks. The nail shaft will tie down the potential sliding segment to the interior stable ground. Nevertheless there have been many failures in this system where creep movement of the shaft results in the loss of stabilizing friction. In passive soil nails the stabilizing effect is considered to come from the shear capacity of the nail shaft and thereby the shaft demands no initial tension force. On the other hand, for active soil nail systems, despite applying a tension force to the nail shaft, the concept of stabilizing is considered exactly as for the passive system. Apparently, based on effective stress concepts, whenever the nail shaft is subjected to tension force, the weak frontal zone will be pulled against the interior stable ground and this thereby increases the effective stress along the potential failure surface. In turn, the shear strength along the surface will be increased and thereby stabilize the slope. This is a more appropriate mechanical design and will be presented in this paper. An innovation to the conventional soil nail system is the application of hybrid anchor at the free end to provide passive pressure resistance to effectively hold down the frontal supporting wall. This involves a special drilling technique for the installation of hybrid anchors. Using this technique, creep is prevented and thus the tension in the nail shaft will provide a long-lasting effective stress along the potential failure surface and thereby effectively stabilize the slope. The design of the hybrid anchor and its in situ pullout behaviour, with and without grout will be presented.
Published Version
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