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Abstract Combined structure of feet-lock bolt and steel arch is an effective support measure in preventing the crown settlement. An analytical model to calculate the support of joint bearing with feet-lock bolt and steel arch in weak rock tunnel was established considering the compatibility conditions of bending moment，axial force，shear force and deformations at the junction. The steel arch was taken as a fixed arch and was analyzed using the method of structural mechanics. The formulae describing the lateral and axial mechanical behaviors of feet-lock bolt were derived with the methods of elastic foundation beam and load transfer respectively. The internal forces and the deformation of feet-lock bolt were studied through an example，and the results were compared with the model given in a reference paper in which the bending moment and deformation compatibility conditions at the junction were ignored. The influence of different installation angles of feet-lock bolt on its internal force and deformations at the junction was discussed. Finally，the influencing factors for the effect in controlling the crown subsidence were studied，including the lateral pressure coefficient and stiffness of surrounding rock，and the parameters of feet-lock bolt. The results indicated that the welded part was the weakest link for feet-lock bolt and should be welded firmly. The bending moment transfer at the junction was recommended to be considered. The lateral resistance to bolt mainly concentrated in the region near the end of bolt，where the surrounding rock should be specially reinforced. Extra length of bolt had no effect to its lateral behavior. The best installation angle was found to be about 45°.：Using more feet-lock bolt(pipe) or using feet-lock bolt(pipe) of high specification enhanced support effect. A low value of the lateral pressure coefficient of surrounding rock be better considered in the design of feet-lock bolt.
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Received: 26 December 2013
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2015, Vol. 34 
