Deformation Patterns and Surface Settlement Trough in Stratified Jointed Rock in Tunnel Excavation

Abstract

The special mechanics of inclined stratified jointed rock may cause unexpectedly surface settlement. This paper studies the special rock condition with analyses of discrete element method (DEM) numerical analysis, field monitoring data and physical model testing results. Numerical models with different internal friction angles, different thicknesses and different inclination angles were analyzed. The surrounding rock deformation patterns can be divided into three categories — shear deformation pattern, mixed deformation pattern and normal deformation pattern — based on different dominant deformation behaviors. The beam analogue model and combined beam analogue model were discussed in different stratum thickness conditions to understand the surrounding deformation patterns. It was found that the settlement trough consisted of two diverging dissymmetrical Gaussian curves by comparing the settlement troughs for different inclination angles, which is unique for excavation in ordinary rock conditions. In this paper, the approximated formulas to verifying the settlement trough position were provided to secure the safety of the upper structures during tunnel excavation.