Assessment of Potential Damage to Utilities Due to Tunneling and Excavation

Underground excavations have the potential for considerable ground movement and subsequently, utilities of varying ages and materials could be impacted. Replacing or relocating all the utilities is cost prohibitive; therefore, there is an interest in assessing potential damage to the utilities. Simplified damage assessment methods have been developed for buildings in the last several decades. In contrast, there is no simplified method for assessment of damage to utilities, which may be attributed to the diversity of the utility materials and structures. An infrastructure project in Ontario, Canada, entails mining a few large diameter caverns using sequential excavation method (SEM/NATM). A new practical method for assessment of the damage to utilities was developed for this project. The method described herein is simple enough to be used for both Level-1 and Level-2 assessments of potential damage to utilities, yet robust enough to address diverse utility structures and complex deformation profiles. These utility structures include sewers and watermains up to 1200-mm diameter and gas mains. Utility materials include brick, vitrified clay, concrete, cast iron, steel, and plastics (PVC and polyethylene). The pipeline behavior is investigated in this paper by analysis of the spatially distributed ground deformations caused by excavations.