INFLUENCE OF PRE-REINFORCEMENT MEASURES ON EXCAVATION STABILITY OF TUNNELLING

Taking the surrounding rock of land section of Xiamen Subsea Tunnel as engineering background,the influence of pre-reinforcement on stability of tunnel from three aspects including failure load of surrounding rocks,displacements of surrounding rocks and safety of primary support is analyzed through model test,in which the effects of grouting,small pipe,anchor and their combination on failure mode of un-supported section and tunnel face are studied. It is shown that single measure is less efficient than the combinatorial one,and the adaptability of single measure should be considered;for single measure to control destructiveness,grouting is more efficient than small pipe and anchor;anchor has less effect on ground displacement,but it is more efficient to control displacement of tunnel face than small pipe. The variation of axial force and safety factor in the primary support stage is related to the effect of pre-reinforcement;and the location of the biggest bending moment is related to the failure mode of tunnel.