Bidirectional construction process mechanics for tunnels in dipping layered formation

The geological conditions surrounding the Tianpingshan Tunnel of the Gui-Guang railway in Guizhou Province are very complex. To study the mechanical regularity of the Tianpingshan Tunnel during construction process, a 3-D physical model was carried out based on the conditions of the section located between 372.335 km and 372.435 km (DK372 + 335 ∼ DK372 + 435) of the tunnel. The 3-D physical model was conducted to clarify the effect of the dipping formation and bidirectional excavation on the tunnel deformation. The results of the crown settlements, floor heave and radial displacement of the equivalent sections in the physical model were analyzed. In the physical model the results of the model test show that in the section located at 25 cm the crown settlements are much smaller than those in the section of 175 cm. And the floor heave in the section located at 25 cm is larger than that located at 175 cm. Furthermore, the radial displacement in horizontal direction is found to be much larger than that in vertical direction in the section located at 25 cm. However, the variation characteristics of radial displacement in the section located at 175 cm are reverse to that in the section located at 25 cm. The numerical study and the field measurements were compared with the model test to demonstrate the effectiveness and accuracy of the results of the numerical study.

► The construction process mechanics of the tunnel were investigated.
► A new kind of material was invented to simulate the rock mass of Tianpingshan Tunnel.
► The results were influenced by dipping layered formation and excavation direction.