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Abstract Combined anchoring technique of tiebacks and soil nails is frequently used in practice for stability of granitoid soil slopes due to their higher anchorage capacity. Despite the routine use，the existing design method for the combination remains however controversial，in which the soil nails are designed to enhance local stability rather than contribute to overall stability of the slopes. The tiebacks are always designed to balance the driving force of a slope. Thus，the current design method cannot reflect the advantages of the combination. Attempting to solve the problem，a new design method is presented，in which the contribution of the soil nails，as well as the tiebacks，to overall stability of a slope is taken into consideration. As a result of this consideration，the preload of the tiebacks decreases and the slope consequently moves(the quantity of the movement is very small) and the movement mobilizes the resistance force of soil nails. By this process，the passive and active anchors work harmoniously；and the stress corrosion possibility of the active anchors(tiebacks) is reduced due to the decreasing of the preload resulting in a better long-term stability. Also，the amount of the tiebacks may decrease，which can save the construction cost. A granitoid soil slope along G323 national highway in China is taken for example to validate the presented design method by the field investigations of preload in some tiebacks，the stress in some soil nails and the ground surface displacement.
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Received: 06 August 2012
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2013, Vol. 32 
