Laboratory model tests and FE analyses on tunneling in the unconsolidated ground with inclined layers

Tunneling model tests are performed in an unconsolidated ground with inclined artificial layers. In order to simulate the model ground with inclined layers, aluminum rods and aluminum blocks are used. Three kinds of formations are introduced for the inclined-layer ground, namely, the 30° formation simulates a ground with lowly inclined layers, the 60° formation with highly inclined layers and the 90° formation simulates a ground with vertical layers. Tunneling process is simulated with a two-dimensional trapdoor apparatus. The 60° formation shows the most significant feature on the non-symmetrical distribution of the earth pressure. For this formation, the outer right part shows a greater concentration of earth pressure than the outer left part of the trapdoor. Simultaneously, the upper left part, for which lateral earth pressure is reduced, shows greater loads than the upper right part of the trapdoor. A numerical simulation by the FE analysis is conducted, using joint elements, to portray the discontinuous behaviors of the model ground, in order to verify the experimental results. By calculating the distributions of earth pressure and surface profiles with the trapdoor displacement, it is confirmed that the calculated results can reasonably portray the experimental results within lower displacements of approximately 1.00 mm.