Seminar - Hongyuan Liu - Effects of Tunnelling on Existing Support Systems in the Sydney Region

Wednesday 19 September 2007, 1.10 - 1.50 pm
Civil Engineering Lecture Theatre 3

Abstract:
Underground excavations such as tunnels have been gradually increasing during the last few decades because of the development of better and more environmentally friendly infrastructure (e.g. highways, railways, subways, sewage disposal, communication, power transmission and other subsurface lifelines) in congested urban cities. As a result, the construction of new tunnels in close proximity to existing structures such as adjacent tunnels, piles, buildings, and pipelines becomes indispensable. In such cases, it is essential to protect the existing structures, and to control the construction of the new tunnel in order not to cause adverse effects on them since the construction of the new tunnels leads inevitably to ground displacements and deformations, which may affect the existing structures and lead to unacceptable damage.

This presentation will study the effect of tunnelling on the existing support system (i.e. shotcrete lining and rock bolts) of an adjacent tunnel using full three-dimensional (3D) numerical techniques, which takes into account the tunnelling procedure, the interaction between the shotcrete lining and rock mass, the interaction between the rock bolts and rock mass, and the elasto-plastic behaviour of the rock mass, the shotcrete lining and the rock bolts. The main objectives are: 1) to develop the 3D numerical procedure, i.e. TUNNEL3D incorporating with ABAQUS; 2) to investigate the complete response of the existing support system to the installation of adjacent parallel/crossover tunnels; 3) to address the influence of the tunnel construction length, the boundary conditions and the mesh, and the position between the new and existing tunnels on the obtained results; and 4) to qualitatively compare the numerical results with others’ field observations and model tests. The main results are summarized into the following two recent papers:

* Liu HY, Small JC, Carter JP. 2007. Full 3D modelling for effects of tunnelling on existing support systems in the Sydney region. Tunnelling and Underground Space Technology (In press and online available, doi: 10.1016/j.tust.2007.06.009)
* Liu HY, Small JC, Carter JP. Effects of tunnelling on the existing support system of a perpendicular crossover tunnel (manuscript in review)

However, this presentation will suppose the rock masses in tunnels are perfectly excavated by mechanical tools such as TBM (tunnel boring machine) and ignore the excavation process by TBM. Please refer to our following recent papers for the fracture process of rock mass by mechanical tools:
* Liu HY, Kou SQ, Lindqvist PA. 2007. Numerical studies on bit-rock fragmentation mechanisms. International Journal of Geomechanics ASCE (In press, to be published in October 2007)
* Liu HY, Kou SQ, Lindqvist PA, Tang CA. 2007. Numerical modelling of the heterogeneous rock fracture process using various test techniques. Rock Mechanics and Rock Engineering, 40 (2): 107-144