Aiming at the problem of asymmetric large deformation in the construction of very large section highway tunnels， considering the relationship between the first principal stress of high in-situ stress and tunnel axis， laminated soft rock interlayer and interlayer state， spatial asymmetry of soft rock at working face， groundwater and other factors， and combined with the physical and mechanical properties of rock samples and ground stress measurements， the mechanism of asymmetric large deformation formation is investigated and the targeted optimization support scheme is proposed based on the analysis of engineering geological conditions， and failure and damage characteristics of surrounding rock and support structure. The results show that the asymmetric large deformation of the surrounding rock in high in-situ stress laminated soft rock tunnel is due to the combined effect of the dip angle α of rock stratum， the angle β between maximum horizontal principal stress and tunnel axis， the angle γ between maximum horizontal principal stress and rock stratum， surrounding rock lithology and groundwater. The location of the asymmetric deformation in the surrounding rock is determined by the combination of the above factors. When the principal stress σ1 is neither perpendicular nor parallel to the tunnel axis， compressive bias tectonic horizontal ground stress will form， leading to lateral asymmetric stresses in the tunnel cross-section and resulting in asymmetric deformation. In order to reduce the deformation effectively and prevent the surrounding rock from loosening and collapsing due to excavation disturbance， the measures of altering the layout of anchors， improving the length and stiffness of the advanced grouting small conduits， spraying temporary sealing， and installing a damping layer of high-density rubber sponge board between the flashing and sprayed concrete are helpful.
