Abstract:  Presently, the cost consumption caused by large settlement deformation of primary support of soft rock tunnel is high. The imbalance between the force of primary support foot and the resistance of locking bolt is the main reason causes the settlement of primary support of tunnel. Hence, the force balance between primary support foot and locking bolt is an important premise to control the settlement deformation of primary support of tunnel. In this paper, based on the elastic foundation beam column principle and the friction pile principle, the internal force and displacement of the locking bolt and its reaction relationship with the foundation are calculated and analyzed, so as to determine the bearing capacity of the locking bolt. Then, by analyzing the flexibility of the locking bolt to the supporting structure, the interaction between the locking bolt and the supporting structure is determined, the mechanical calculation model of the supporting structure considering the influence of the locking bolt on the bottom foot of the supporting structure is established further, and the force acting on the end of the locking bolt is calculated as the design basis of the locking bolt. On this basis, the current popular problems of grade Ⅴ surrounding rock using 40 foot locking bolt are analyzed, and the bearing capacity of 108 foot locking bolt is analyzed through example calculation. Finally, taking the construction of grade Ⅵ surrounding rock aeolian sand tunnel as an example, the remarkable effect of distributed strengthened foot locking anchor pipe and pile on controlling support settlement and deformation is validated. It is concluded that the reaction between surrounding rock and support and that between support and foot locking bolt can be determined according to the principle of loadstructure method, so as to achieve the balance and stability of the force between support structures and further control the support settlement.

Key words: tunnel, primary support, deformation control, foot locking bolt, elastic foundation beam column, friction pile, elastic nonhinged hinged arch, direct elastic resistance, reinforced locking foot, anchor pile