Optimum Arrangement of Prestressed Cables in Rock Anchorage

Prestressed cables in anchorage are usually arranged with equal length, and the rockʹs stability is weakened by tensile stress concentrating in the front end of the grouted portion. Besides, the construction of the prestressed cables is always difficult because of too small cable spacing. Based on the anchorage design used in the construction of the West River Bridge of New Nanning-Guangzhou Railway, the prestressed cable group were improved to be quincunx arrangement which is long cables alternating with short ones, so as to decrease the superposition of tensile stress. When anchorages bear the prestressed force and bridge construction loads, the change of rock slopeʹs displacement and anchoring force were studied comparatively by three dimensional numerical simulation, which were carried on in two conditions, one is the prestressed cable group arranged with equal length while the other is quincunx. The research shows that, compared with the equal length arrangement, prestressed cable group adopting quincunx arrangement can further reduce the displacement of the rock slope, increase the short cableʹs anchoring force and save engineering costs while keep the rock anchorage system safely when bearing bridge construction loads.