Slurry and Earth Pressure Balanced Shields, - Comparison and Application Domains. Which one is a suitable choice?

Since the development of the Earth Pressure Balanced Shield in late seventies, a big debate governs over the choice between slurry and E. P. B. Shields. Here, the author intends, based on his experiences in numerous tunneling projects as well as research works that he has been conducting on tunneling in soft water-bearing grounds, to give a better insight to each one of the technics and their application domains. After recalling the principals of the slurry and E.P.B. Shields, the advantages and disadvantages of each one of the technics are described. For a better comprehension, a hypothetical case of tunneling is studied, where a tunnel of 8 meter in diameter is to be driven in alluvial deposits under relatively high hydrostatique pressure. The parameters to be considered, their significances and importance are pointed out. Then some experiences from actual projects and some interesting results from research works conducted on a prototype scale model are brought up.