TA project: PROPWALL

Click here to read the final report of the PROPWALL Project.

A concise presentation of the project's aim and main outcomes is available in the Joint brochure of the SERIES TA facilities.

TITLE OF PROPOSAL: Centrifuge study of the seismic performance of propped flexible retaining walls embedded in saturated sand

HOST TA FACILITY: 
Turner Beam Centrifuge, Cambridge, UK

TA AGREEMENT BETWEEN USERS AND FACILITY:
May 2011

STARTING DATE:
December 2010

END DATE:
June 2012

NO. OF USERS (researchers):
7

LEAD USER: 
Giulia Viggiani - University of Rome Tor Vergata (Italy)

ADDITIONAL USERS: 
Stefano Aversa - University of Naples Parthenope (Italy)
Paulo Alexandre Lopes de Figueiredo Coelho - University of Coimbra (Portugal)
Riccardo Conti – Sissa, Trieste (Italy)
Luca de Sanctis – University of Napoli Parthenope (Italy)
Rosa M.S. Maiorano – University of Napoli Parthenope (Italy)
Michele Tricarico – University of Napoli Parthenope (Italy)


SUMMARY OF PROPOSED RESEARCH:

Monitoring of existing structures and experimental observations on small scale models have shown that retaining structures can experience serious damage when exposed to moderate to strong earthquakes, with both failure of structural elements and large permanent displacements of the walls (Anastassopoulos et al., 2004). An understanding of the dynamic behaviour of retaining structures and adequate design procedures are vital for the control of seismic induced displacements and the limitation of damages to the surrounding buildings.
The seismic interaction between embedded retaining walls and the surrounding soil can be evaluated using several procedures at different levels of complexity. The simplest procedures (pseudo‐static approach) are relevant for very simple retaining structures (i.e. un‐propped retaining sheet pile walls or sheet pile walls with a single level of props or anchors located in the proximity of the ground surface). The second group of methods (simplified dynamic analyses) considers separately the free‐field propagation of the seismic action trough the ground and the interaction of the wall and the soil simulated by means of a visco‐elasto‐plastic Winkler subgrade model (Richards et al., 1999). Complete soil‐structure interaction analyses seem more appropriate to simulate the seismic behaviour of such kind of structures. Many commercial (FEM or FDM) computer codes are able to apply natural or artificial seismic input at the base of the mesh and to evaluate the performance of the ground and of the structure during the earthquake.
However, many uncertainties exist in the numerical analyses of dynamic soil‐structure interaction, among which a major role is played by the constitutive model adopted for the soil as very rarely the libraries of commercial codes contain constitutive models able to simulate with sufficient approximation the cyclic and dynamic behaviour of soils under seismic conditions.
The present research project aims at investigating the seismic behaviour of flexible retaining structures supported with one prop at dredge level or with a second prop at the top of the wall. Both types are very common in the case of railway and road underpasses, in which the foundation raft acts as a prop and a second prop, for higher excavation levels, is due to the presence of the over passing structure. These structures are common also in the underground levels of buildings. The research follows on from previous and current work on the seismic behaviour of flexible retaining structures in dry sand: it is proposed to extend the scope of the research to saturated conditions to examine the effects of pore water pressure generation during seismic shaking on the stability and the displacements of the walls and the soil mass.
The objective will be pursued with complementary activities: (1) physical modelling on reduced scale models carried out in the geotechnical centrifuge of the Schofield Centre and (2) advanced numerical modelling with fully coupled finite difference dynamic analyses using an advanced constitutive model developed by Papadimitriou & Bouckovalas (2002) which was kindly made available to the research group. 

What's next

Series logo small   SERIES Concluding Workshop
  Joint with US-NEES "Earthquake Engineering Research Infrastructures

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