Abstract: The shallow buried tunnels under unbalanced geostresses in complex geological conditions exist uncertainties. Different traffic lanes in the highway tunnel will result in the change of stress and strain states in the rock mass. This paper presents the parametric studies of two through four traffic lanes of shallow burred highway tunnels under the same unbalanced geostresses by using FLAC3D commercial software. The effect of traffic lanes on the stability of rock mass during the tunnel excavation. The results indicate that, with the increase of traffic lanes in the tunnel, both the vertical and horizontal deflections in the rock mass increase. The pressures at the both sides, crest and bottom of the excavated tunnels are increasing with the increase of traffic lanes. The plastic zones in the rock mass of tunnels with all three different traffic lanes have extended to the ground surface with similar shapes. Tunnels with less traffic lanes are more stable with a smaller plastic zone. From the stress, strain plastic zone and deformation in the surrounding rock mass point of view, tunnels with three traffic lanes under the unbalanced geostresses will have a least performance and the tunnels with two lanes perform better.

Key words: Tunneling Engineering, Traffic Lanes, ShallowBuried Tunnel with Unbalanced Geostresses, Plastic Zones