Is Excess Pore Water Pressure Build up an Engineering Demand Parameter for Excavation Analyses?-PPT Presentation

PPT Presentation

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The presentation examines whether excess pore-water pressure buildup should be treated as an engineering demand parameter in deep-excavation analyses. Fully coupled finite-element simulations of a flexible excavation support system in soft clay used a hypoplasticity model and a groundwater table 1 m below the surface.<br /><br />Parametric studies investigated how excavation rate and soil hydraulic conductivity affect the response, including changes in a dimensionless α parameter and maximum vertical surface settlement. Results were presented across different excavation-rate-to-conductivity ratios and excavation geometries, indicating that the degree of hydraulic coupling matters when estimating excavation-induced movements.<br /><br />The proposed assessment method uses α, with a threshold near 0.3, to guide whether an undrained analysis is sufficient or a fully coupled solid–fluid analysis is recommended. It estimates settlement responses using figures and semi-empirical methods, including Clough et al. (1989), and is compared with excavation case histories.<br /><br />Overall, the work presents excess pore-water pressure effects as relevant to selecting an appropriate analysis approach: excavation rate and hydraulic conductivity influence whether an undrained approximation can represent the response or whether full soil–fluid coupling is needed.

Keywords

excess pore-water pressure

deep excavation

finite-element simulation

soft clay

hydraulic conductivity

excavation rate

groundwater table

surface settlement

hydraulic coupling

undrained analysis