Abstract:

In case of deeply buried tunnels passing underneath pile foundations, the formula of vertical safe distance between the tunnel crown and the bottom of the pile foundation is deduced according to the arching theory of rock mechanics. The calculation formula is related to the surrounding rock grade, the physical and mechanical properties of the surrounding rock, the tunnel diameter, the pile foundation diameter, the horizontal distance from the pile foundation to the tunnel center and the loading on the pile foundation bottom, etc. The vertical safe distance from the tunnel crown to the bottom of the pile foundation in case of Line 1 of Nanchang Metro is calculated with the deduced formula. Then 2D and 3D numerical calculation models are used to verify the calculation results. The results show that the 2D numerical calculation results are consistent with theoretical calculation results and due to the space effect, the 3D numerical calculation values are approximately 85% of the 2D calculation values.

Key words: deeply buried tunnel, pile foundation, vertical safe distance, arching effect