Schuerch, Roberto
Roberto Schuerch
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Tunnelling, Tunnel Jacking, Ground Stability, MC Model, MCC Model
This thesis investigates the problem of time-dependent stability of geotechnical structures (such as trenches or tunnels) in medium- to low-permeability water-bearing grounds, typically clayey or silty soils. The peculiarity of these soils is that they respond to excavation with a delay. The time-dependency can be traced back to the swelling process triggered by the dissipation of the excavation-induced negative excess pore pressures. Unstable conditionsmay necessitate improvement or reinforcement of the ground or the application of a support (e.g. by compressed air or pressurized bentonite slurry in the case of tunnel face). As such measures may present economical and operational disadvantages, the question of whether and for how long the excavation can remain stable without support is of great practical relevance. The stand-up time (time lapsing between end of the excavation and the occurrence of failure), and thus the feasibility of refraining from ground reinforcement, improvement or support, depends essentially on soil strength and permeability.Tunnelling, Tunnel Jacking, Ground Stability, MC Model, MCC Model
This thesis investigates the problem of time-dependent stability of geotechnical structures (such as trenches or tunnels) in medium- to low-permeability water-bearing grounds, typically clayey or silty soils. The peculiarity of these soils is that they respond to excavation with a delay. The time-dependency can be traced back to the swelling process triggered by the dissipation of the excavation-induced negative excess pore pressures. Unstable conditionsmay necessitate improvement or reinforcement of the ground or the application of a support (e.g. by compressed air or pressurized bentonite slurry in the case of tunnel face). As such measures may present economical and operational disadvantages, the question of whether and for how long the excavation can remain stable without support is of great practical relevance. The stand-up time (time lapsing between end of the excavation and the occurrence of failure), and thus the feasibility of refraining from ground reinforcement, improvement or support, depends essentially on soil strength and permeability.