PERFORMANCE AND REHABILITATION OF BURIED CORRUGATED METAL CULVERTS AND PIPES

Abstract

The development of civilisations involves the design of supportive, integrated infrastructure, to promote prosperity and enhance the life of populations by overcoming social and economic constraints. Well-established civil infrastructure, including buried soil-metal structures such as deep underground tunnels and utility pipelines, and shallow corrugated metal pipes and culverts, can be considered an essential basis for the progress of developed communities. Growing populations and high volumes of traffic can cause serious congestion in urban centers. Thus, it is advantageous to bury utilities, to avoid interactions with surface structures. Corrugated metal culverts (CMCs) and corrugated metal pipes (CMPs) offer an innovative approach to provide alternative routes for traffic and utilities. Furthermore, due to their time and cost efficiency, CMCs and CMPs are a preferred replacement for aging buried concrete structures. This thesis presents a detailed analysis of the performance of buried corrugated metal culverts and pipes subjected to backfilling loads and surface loading. The first part of the research involved numerical modelling finite element analyses (FEA) of culverts and pipes with different geometries and service loads. A full-scale experiment on a buried open-bottom arch CMC was then used to investigate impacts of the placement and compaction of surrounding backfill soils on the deformations and internal forces developed in buried CMCs and CMPs. The research also examined the influence of deterioration in buried steel structures due to aging factors, primarily involving corrosion and mechanical abrasion. This was achieved by employing accelerated wet/dry cyclic corrosion tests for buried mild (uncoated) and galvanized (zinc-coated) steel coupons. The analysis showed the impact of corrosion propagation on the degradation of the steel material, exhibited by a decrease in nominal thickness (i.e., damage loss) and a deterioration of mechanical properties (i.e., tensile strength, ductility, and hardness). Moreover, the study used empirical prediction models to estimate the development of future corrosion damage over a period of years. Finally, the research investigated the performance of buried CMCs under surface static loading. Full-scale test configurations of buried open-bottom arch CMCs were used to study culvert responses to different cover depths (i.e., 600 mm and 300 mm), culvert conditions (i.e., intact and deteriorated), and rehabilitation techniques for deteriorated (damaged) culverts. Two rehabilitation methods were considered. Carbon fiber reinforced polymer (CFRP) patches were applied inside the culvert to repair damaged spots, and geocell panels were installed in the top backfill soil beneath the applied surface loading to reduce surface settlement and mitigate the stresses transferred to the buried culverts. The test configuration results were compared, based on the surface load-settlement curves, the increase in soil vertical stresses, and the deformations and internal forces developed in the culverts. Furthermore, a numerical modelling finite element analysis was employed to simulate the test configurations under surface static loading. The numerical modelling results were validated against the laboratory measurements. This demonstrated the ability of the finite element analysis to estimate the behaviour of buried CMCs and CMPs with different cover depths, culvert conditions, and rehabilitation/upgrading techniques.