On the effects of pore water pressure buildup and dissipation on the seismic performance of a propped r.c. diaphragm wal
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RESEARCH PAPER
On the effects of pore water pressure buildup and dissipation on the seismic performance of a propped r.c. diaphragm wall in sand Kateryna Oliynyk1 • Nicola Pontani1 • Claudio Tamagnini1 Received: 2 March 2020 / Accepted: 12 September 2020 Ó The Author(s) 2020
Abstract The study concerns the analysis of a retaining structure composed by a couple of r.c. diaphragm walls propped at the crest in loose and medium-dense, variably saturated sand under seismic conditions. Fully coupled dynamic equilibrium conditions and pore water flow in the porous soil have been taken into account, in order to assess the effects that the development and subsequent dissipation of excess pore water pressures can have on the performance of such structures under seismic conditions. To this end, a series of simulations in which the saturated soil permeability is varied of about two orders of magnitude has been carried out, in order to consider different evolution rates for the dynamic consolidation process. The von Wolffersdorff hypoplastic model and the van Genuchten water retention equation have been used to describe the mechanical and hydraulic behavior of the sand. The results obtained in a large series of finite element simulations show a significant dependence of the seismic performance of the structure evaluated in terms of permanent rotations and structural loads, in view of the modern performance-based design criteria on the excess pore pressures buildup during the seismic shaking and on its dissipation with time. For the particular seismic input considered, neither fully drained nor fully undrained conditions can be considered applicable in most of the cases considered. In such conditions, the quantitative assessment of wall and soil displacements, pore water pressures and effective stress distributions within the soil requires necessarily the solution of a fully coupled, nonlinear dynamic consolidation problem. Keywords Coupled dynamic consolidation Diaphragm walls Earthquake loading Flexible retaining structures Hypoplasticity Performance-based design Sand
1 Introduction The seismic behavior of diaphragm walls supported retaining structures has recently attracted significant interest in the geotechnical scientific community and among practicing geotechnical engineers, in view of their importance in the development of underground transportation infrastructures, notably in urban environments.
& Claudio Tamagnini [email protected] Kateryna Oliynyk [email protected] Nicola Pontani [email protected] 1
University of Perugia, via G. Duranti, 93, 06125 Perugia, Italy
In particular, much attention has been paid on the use of performance-based concepts to assess the safety of the structure against earthquake loading. In this approach, the attention is focused on the evaluation of the deformation response of the soil–structure system under a given seismic load, rather than on the assessment of system stability based on conventional safety
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