Abstract
Pipelines are reliable and economical means of transporting water, oil, gas, sewage and other fluids. They are generally referred to as lifelines since they play a pivotal role in running a nation’s industries, services, and economy. Thus, it is essential that they remain operational at all times. Pipeline systems are located over large geographical regions and they are generally buried below ground for safety, economic, environmental and aesthetic reasons. As a result, they are exposed to a wide variety of soil profiles and hazards caused by earthquakes. Past earthquake-related pipeline damage highlighted the vulnerability of buried pipelines to Permanent Ground Deformations (PGD) caused by earthquakes. Different types of pipeline failure modes such as joint failure, tension failure, beam buckling, and local buckling failure have been observed in past earthquakes. Recent earthquakes showed that unsatisfactory performance of buried pipelines is still observed. As a result, further research is required in this subject. This thesis aims to study the response of buried continuous pipelines to faulting through physical model tests and numerical analysis. In this Ph.D. research, relevant scaling laws and non-dimensional groups for buried continuous pipelines crossing active faults are derived by using Buckingham-π theorem and governing differential equations. The physical meaning of these non-dimensional groups and their practical ranges are presented. A new physical model test setup of buried continuous pipelines crossing strike-slip faults was developed considering the non-dimensional groups and scaling laws. The working principle of the test setup and sensors used in the tests are also presented. Furthermore, a simple and scalable end connector for physical modeling based on the equivalent end springs approach in numerical modeling is proposed. The performance of the proposed end connector is assessed via physical model tests and numerical analysis. In addition, a new mitigation technique – using tyre derived aggregate (TDA) as backfill material at the vicinity iii of fault crossings- is proposed. The performance of the proposed mitigation method is assessed through physical model tests. The effects of trench shapes, trench dimensions and tyre-chip content in the backfill on pipeline performance are also investigated. Finally, three-dimensional (3D) Finite Element (FE) models of buried continuous pipelines crossing active faults are developed and these models are validated through case studies, experimental studies and analytical methods. By using the calibrated 3D FE models, a parametric study is carried out to investigate the effects of different pipe end conditions on the behaviour of buried continuous pipelines crossing strike-slip faults and to investigate the effects of non-dimensional groups on pipeline response to strike-slip faulting. The research study shows that the newly developed experiment setup is a reliable tool to capture the behaviour of buried continuous pipelines crossing strike-slip faults and to investigate the physics behind the soil-pipe interaction problem under faulting. Furthermore, the proposed end connector is capable of simulating pipe end conditions more realistically compared to conventional pipe end conditions used in earlier experimental studies. Finally, the proposed mitigation technique –using TDA as backfill material at the vicinity of fault crossings- is an effective way of protection that reduces peak bending and axial strains within the buried continuous pipelines crossing active faults.