| Pipe bursting and horizontal directional drilling (HDD) are two common construction techniques used to install new pipelines in the subsurface without the use of an open trench. Because of the relatively young age of these trenchless technologies, solutions are not readily available to predict soil movements in the shallow near-surface environment. Instead, designers of pipe bursting and HDD installations rely on generalized rules of thumb to determine the required depths of cover and clearances between new installations and existing utilities and/or structures to ensure detrimental damage does not occur. Current pipe bursting rules of thumb require clearances based on the degree of upsizing of the replacement pipe. Unfortunately, these guidelines do not consider the depth of the pipe bursting installation, magnitude of the overburst, soil properties, location and relative condition of the existing utility and/or structure in relation to the new installation, or the allowable deflection for an existing utility/structure. Current HDD industry rules of thumb are based on installation depth and product pipe diameter. Unfortunately, these guidelines do not consider the diameter of the bore, soil properties, magnitude of the bore pressurization induced displacement fields, location and relative condition of the existing utility and/or structure in relation to the new installation, or the allowable deflection for an existing utility/structure. A lack of published case histories involving these trenchless technologies increases the difficulty in assessing whether current rules of thumb are sufficient to adequately protect existing utilities and/or structures in response to pipe bursting or HDD installations.; A research program, originating back to 1996 at the University of Waterloo, Waterloo, Ontario, Canada initiated research efforts into the behaviour of polyethylene pipes during installation using HDD construction practices. Monitored parameters during installation advanced the understanding of the installation process. Work completed and presented as part of this research builds on this initiative expanding it to include additional instrumentation and the development of an updated data acquisition system. Results of this research work have been used to assess HDD rules of thumb associated with the behaviour of the pipe and subsurface during and following installation. (Abstract shortened by UMI.)... |
