Abstract:

Taking Hanguguan tunnel on ZhengzhouXi'an passengerdedicated railway as an example, the authors synthetically analyze and determine the deformation model of the surrounding ground of deepburied large crosssection tunnels in loess stratum, as well as the working mechanisms of the bolts of these tunnels based on the deformation model, by theoretic analysis and insitu prototype test. The study results are as follows: For the surrounding ground at the arch, the attenuation of the displacement is slow, the relative displacement of the surrounding ground at different depths is very small and integral settlement occurs; For the surrounding ground at the sidewall, the attenuation of the displacement is rapid and the relative displacement of the surrounding ground at different distances is large; the deformation model of the surrounding ground at different positions is the key factor that influences the working mechanisms of the bolts and the force that the bolts at the arch undertake is very small, while the force that the bolts on the sidewall undertake is large. Based on the study results, the authors suggest that bolts may not be installed in the 130° range of the tunnel arch and that fullybonded bolts should be installed within the scope from the mentioned range to the side wall foot. These study results, which have provided effective guidance for the design and construction of the tunnel, can be used as reference for similar works in the future.

Key words: tunnel in loess, deep cover, deformation model, bolt, working mechanisms