Pore pressures around tunnels in clay

TLDR: In this paper, the pore-pressure generation and dissipation around shallow tunnels excavated in both normally and overconsolidated clays are investigated, and the effects of immediate support on pore pressure are also studied by defining a quantity termed effective stiffness ratio (ESR).

Abstract: The pore-pressure generation and dissipation around shallow tunnels excavated in both normally and overconsolidated clays are investigated. The influence of the diameter D, depth of cover to diameter ratio H/D, coefficient of earth pressure at rest K0, and strength and modulus variations with depth on pore-pressure generation are examined. The effects of immediate support on pore pressure are also studied by defining a quantity termed effective stiffness ratio (ESR). A two-dimensional, nonlinear finite element analysis is performed to obtain the pore-pressure generation behav-iour. Strength, modulus, initial stress field, and unloading due to excavation are reflected in this analysis. The pore-pressure dissipation behaviour is investigated by employing an uncoupled consolidation theory using finite elements. A dimensionless time factor is used to present the results of pore-pressure dissipation. These results are presented using nondimensional quantities and in normalized forms. The results are directly a...