The bamboo-truncating tunnel portal’s structure is at complicated 3D stress condition

so 3D numerical calculation method is necessary to used for correct result relatively. For the simplifying calculation model

the trial was carried out for up bamboo-truncating tunnel portal which with the slope 1: 1.5 in Class Ⅴ surrounding rock. Firstly

the model test result was used to proof the arch crown surrounding rock stress which gained by 3D numerical analysis

both have good compatibility. Secondly proceed from the structural stress character and the distribution of surrounding rock stress

the inner force controlling cross-section of structural transverse and longitudinal direction were gained. Through the research

the relationship between q and of arch crown load in each pressure distribution figure was also obtained. Furthermore

the pressure distribution graphics in transverse direction was plotted; and load value calculation methods in longitudinal direction was provided. Therefore

the calculation model was simplified from 3D numerical structural calculation to load-structure model with transverse and longitudinal direction to calculate its inner force separately.