The objective here is to model the mechanism of face stability ahead of tunnel boring machines (TBMs) in soft ground, with particular emphasis on the increments of water pressure induced in front of the TBM due to the following factors:
- Face pressure higher than groundwater pressure
- Conditioning elements, such as foam and slurry, are supossed to penetrate into the ground to reduce its permeability and concentrate the pressure loss (from face pressure to groundwater pressure) in a thin layer at the TBM face. However, the penetration velocity of these elements can be smaller than the excavation rate of the TBM, in which case the TBM excavates the ground faster than the flow of particles.
If 1 and 2 occur, a new field of groundwater pressures is induced ahead of the TBM, which modifies the effective stress state in the ground.
Published References:
- Dias, T. G. S., & Bezuijen, A. (2017). A Design Framework for TBM Face Equilibrium in Permeable Ground. In ITA World Tunnel Congress 2017 - Surface Challenges - underground solutions (p. 7). Bergen, Norway (Download)
- Dias, T. G. S., & Bezuijen, A. (2016). A Different View on TBM Face Equilibrium in Permeable Ground. In ITA World Tunnel Congress 2016 - Uniting an Industry. San Francisco, USA: Society for Mining, Metallurgy, and Exploration (SME) (Download)