Abstract
The research reported in this thesis investigates the nature of trench excavation induced ground movements and their adverse effect on adjacent buried pipelines. The factors affecting the 'in-service' performance of buried pipelines are first reviewed. This is followed by a review of the available field data relating to ground movements induced by trench excavations. A finite element parametric study of trench excavation induced ground movements under undrained conditions is then presented. The models used are governed by linear elasticity. The results indicate that the pattern and magnitude of ground movements are dependent on the soil properties, the excavation geometry and the in-situ stresses. These results show a very rapid build up of movement near the trench ends. The results of a soil-pipe interaction analysis demonstrate high concentrations of bending and shear forces near the trench ends. Analytical studies aiming to assess the interface slippage and the free rotations of the pipe joints show no significant adverse effects. The most important factors affecting the bending moments induced in the pipe are found to be the excavation depth, the soil in-situ stresses, the pipe position, the soil modulus and the relative modulus of the soil and the pipe. An analytical study shows that the provision of rigid supports to the sides of a trench excavated in different stages may result in fixing of the pipe curvature and lead to an overall increase of bending moments. A procedure for estimating the maximum immediate strains in pipes, induced by adjacent trench excavations is finally proposed.