Abstract:

By using the upper bound plastic theory, the upper bound solution model of prereinforced structure of frontal soil mass of working face of shallow tunnels in soft soil is established, and the mechanical behavior of the prereinforced structure of frontal soil mass of working face of shallow tunnels is systematically analyzed. The stability of working face is studied under the conditions that the working face with preserved core soil and frontal soil mass is reinforced. It is concluded that preserved core soil can bring distinctively mechanical effect to working face. It is also proposed that in special stratum, frontal prereinforcement can effectively maintain the stability of working face. And it is confirmed that the failure of working face is progressive and cumulative, that is to say, the crack slide angle of soil mass on working face is a constant value, which doesn’t change with the prereinforcement measures.

Key words: mined tunnel under shallow cover, soft oil, soil mass ahead of working face, advance reinforcement, upper bound solution model, advance support force