Mechanics behavior of lattice girder reinforced shotcrete support for tunnels

Presently, the New Austria Tunnelling Method (NATM) are applied in the construction of most mountain tunnels. And in the NATM, lattice girder reinforced shotcrete support for tunnels is applied more and more widely, but the study of mechanics between the two parts and effects on support is also rare. Then the mechanical model of lattice girder reinforced shotcrete support was established by the theory of thin shells. Combined with the practical engineering, the elastic solution of the initial support was got and the mechanical properties of initial support were analyzed. After that, the effects of the thickness of shotcrete and spacing of grid arch on support were researched. The study show that when the spacing of grid arch are changed between 0.6 m and 1.0 m, its effects on the support are not very significant. And that, when the shotcrete is upgraded, concrete plays a major supporting role.