Abstract: The study of the instability deformation characteristics and prereinforcement control effect of aeolian sand tunnel is of great significance. Hence, the basic properties and parameters of aeolian sand formation of Menghua Railway are obtained by laboratory physicomechanical experiment. And then the variation laws of maximum principal stress and plastic zone of the tunnel are analyzed by numerical simulation. Finally, the effects of different prereinforcement methods in aeolian sand tunnels are studied by model experiment. The experimental results show that: (1) The antishear ability of aeolian sand can reach the extreme value when the water content is about 7%-14%, which is more conducive to the stability of tunnel surrounding rock. (2) The instability of the tunnel is sudden, which will mainly experience 3 basic processes, i.e. partial destruction of the tunnel face, crown collapse continuously, and large volume of instability. (3) The internal displacement and deformation velocity of the surrounding rock of the crown ahead of excavation face without pregrouting are the highest, which could be reduced by 81.1% and 98.3% respectively after the combined reinforcement of horizontal rotary jet grouting piles and steel pipe. (4) The combination of horizontal rotary jet grouting pile and steel pipe has the best effect on the surrounding rock stress control of crown ahead of the excavation face; and the reinforcement control range of horizontal rotary jet grouting pile is smaller than the combination of horizontal rotary jet grouting pile and steel pipe.

Key words: aeolian sand tunnel, instability deformation characteristic, model experiment, pre-reinforcement method, control effect