Soil-structure interactions due to cyclic translations of integral abutment

Abstract

The primary objective of this thesis is to investigate soil-structure interactions due to cyclic abutment translations and the mechanisms causing soil settlement/heave and escalation of lateral earth pressure behind the integral abutment. In addition, a comparative study of the mitigation performance of two compressible inclusion materials in an integral abutment, one being a commonly used traditional compressible inclusion (EPS geofoam) and the other a new potentially promising material (Infinergy-«), was conducted. The study of the fundamental mechanisms of soil-structure interactions in response to cyclic translations has established conceptual underpinnings beneficial to optimising the abutment design of integral bridges. This includes ensuring cost-competitiveness, safer design, and better long-term service performance, especially at the approach to the integral bridge, which typically suffers from persistent settlement/heave bump, which is challenging to eradicate. This research has also generated new knowledge of soil-structure interactions of integral abutments subjected to cyclic translational movements under true field stress/strain conditions. This could be a benchmark against which the effects under cyclic rotational or a combination of translational and rotational movements could be compared. Finally, the work has helped to enhance the understanding of investigators and designers in a study area still defined by uncertainties in predicting the effects of the translational, rotational, and combination of both movements of abutment and abutment foundation in integral bridges. The experimental tests conducted in a specially designed physical model with similarity with a full-scale prototype have been complemented by the use of other analysis tools, namely, PIV techniques and Abaqus finite element models, to capture effects and kinematics of soil-structure interactions, including soil circulation, slumping, densification, loosening, heaving and failure surfaces. This help to ensure current design guidelines on soil-structure interactions of integral abutments are assessed against realistic and true stress/strain levels as might be expected in the field to determine the limits of their applicability. The findings from this thesis have highlighted the shortcomings in three out of four design guidelines in that they underestimate the lateral earth pressure in integral abutments subjected to cyclic translations. The new material named "Infinergy-«" investigated in this research has outperformed the traditional and widely used expanded polystyrene as a compressible material in integral abutments. This should provide designers with a feasible and better engineering alternative to consider for future integral abutment projects.

Date of Award	2022
Original language	English