Residual strength of underground structures in service

Abstract

Old tunnels suffer from deterioration and it is necessary to assess their residual strength to properly organize their repair and strengthen them. The stress state of underground structures evolves over time, firstly because of the advancement of the working face during construction, then due to gradual changes in soil properties and mechanical properties of materials composing the infrastructures, such as reduction of cohesion, loss of strength and (or) stiffness, etc. These changes are caused by combined actions such as creep and (or) weathering processes as well as the appearance of cracks that induce redistribution of stresses and therefore strains. This study investigates tunnels and galleries of the Paris underground. Macromodeling based on the finite element method allows consideration of different scenarios of tunnel-lining deterioration, specifically at the extrados of the galleries or tunnels. To understand changes in the stress state, and also damage occurrence and associated redistributions (stress and strain), it is necessary to model the delayed deformations. To model the infrastructure behavior, a time-dependency approach has been chosen. This approach can quantify the damage and predict the residual strength of this type of underground structure. An elastic–viscoplastic constitutive model with strain-softening is used to reproduce the appearance of the degraded zones and their behavior. The results obtained with the numerical approach reproduce Paris metro tunnel behavior, corroborate geoendoscopy results, clarify their interpretation, and improve the management of infrastructure repairs.

Tunnel Failure Evolution and System Reliability Analysis Based on the β-unzipping Method

“…Failure criteria and the evolution process are key areas of underground structural research. Structure failure is a process that evolves from local damage to overall destruction [13,14]. Different initial damage causes different failure processes [15][16][17][18][19][20].…”

Mechanical Behavior of Tunnel Lining with Cracks at Different Positions

“…Therefore, research on lining cracks is of great significance. Much research has been carried out to study the damage of tunnels; the cause is summarized and analyzed by on-site investigation of the number, length, inclination, and width of lining cracks and the depth of typical cracks [8,9]. Studies on the failure of concrete structures have been carried out based on numerical analysis [10,11].…”