Force-displacement Behavior and Progressive Failure Mechanism of Earth-retaining Structures under Earthquakes

Project: Research

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Description

Earth-retaining structures are geotechnical engineering systems constructed tomaintain the stability of soil between two different ground elevations. It is estimated (GEO2002) that, in Hong Kong, the fatality risk attributable to retaining wall failures alone justifiesan annual investment of HK$10M in life loss mitigation measures. Significant additionalrisks arise due to property damage caused by the collapse of retaining walls or indirecteconomic costs associated with excessive displacement of walls (due to disruption ofservices). Although HK is not located within a high-risk seismic zone, the BuildingDepartment has employed consultants to introduce tailor-made seismic-resistant designstandards into HK’s building regulations, which will include retaining walls. In HK,earth-retaining structures are designed using the conventional Limit State Design (LSD)approach, which only considers safety, ignoring performance, and can lead to veryconservative solutions when dealing with uncertainties.Currently, there is a move in design methodology away from LSD to PerformanceBased Design (PBD), particularly in earthquake engineering. PBD has prevailed because itconsiders not only the uncertainties inherently present in seismic design in an explicit manner,but also allows holistic performance objectives (e.g., “Life Safety”) to be achieved in bothengineering and financial terms. The aforementioned government consultants dealing withthe seismic design standards are considering adopting the PBD approach. However, theconcept of PBD has never before been applied to the design of earth-retaining systems. Oneof the major challenges in the implementation of PBD to such structures rests with therequirement of having accurate predictions of displacements. This is due to the fact thatdeformation is directly related to material damage and thus is needed to quantify the“performance” of the system. A number of studies (e.g., the sliding block models andpseudo-dynamic methods) have focused on the displacement estimation of rigid retainingwalls but with questionable results, as most of them neglect either the rotational or thetranslational displacement mode.This project aims to develop an analytical model for assessing the tip displacementof earth-retaining structures, by analytically solving and integrating the full stress and straindistributions in the soil mass to derive the system’s force-displacement relationship,considering both the rotational and translational displacement modes. To calibrate theanalytical model, experimental work will be undertaken on two medium scale retaining wallstructures. The ultimate goal is to enable the draft of Performance-Based design criteria forthese structures, which can be adopted in the new HK design guidelines.

Detail(s)

Project number9048078
Grant typeECS
StatusFinished
Effective start/end date1/01/1731/12/21

    Research areas

  • Earthquake engineering , Force-displacement model , Progressive Failure , Performance based design , Retaining wall