Abstract:  In order to study the surrounding rock load calculation method suitable for horizontal layered surrounding rock tunnel and guide the actual tunnel construction, the paper adopts the method of theoretical derivation and the numerical simulation loadstructure calculation model to optimize the excavation method and the initial supporting parameters of horizontal layered surrounding rock tunnel. The results show that: 1) Rock beam structure will be formed when the vault of horizontal layered rock tunnel collapses. Based on this, a revised method for the calculation formula of vertical load in horizontal layered rock tunnel is proposed. 2) Based on the mechanical balance and stability analysis model of the face and taking into account the effect of collapsing vault rock beams, the ultimate thickness of horizontal layered sandstone and mudstone rock beams in the working area of inclined shaft No. 1 of Tongchuan tunnel is calculated to be 1.7 and 2.3 m, respectively. When the rock layer thickness is greater than the ultimate thickness, the rock beams can replace the advance support to strengthen the vault; At the same time, the construction method of surrounding rock Ⅲ and Ⅳ is calculated and analyzed, and the results show that the stability coefficient of the face of the whole section method instead of the original step method still meets the standard requirements. 3) After optimizing the initial supporting parameters of Ⅲb, Ⅳa and Ⅳb types in the inclined shaft working area of Tongchuan tunnel No. 1, the maximum spacing of steel supports is 1.8, 1.6 and 1.6 m, respectively, and the corresponding safety factors of the most unfavorable section are 1.65, 1.63 and 1.57, which are all greater than the safety factor control standard in the code.

Key words: horizontal stratified rock, load calculation, construction method, initial support, parameter optimization