Subsurface ground movements associated with trenchless pipe replacement methods

As we enter the new millenium, our nation is facing a crisis resulting from underground infrastructure that are functioning far beyond any reasonably anticipated design life and require renewal to mitigate deterioration. Maintaining this large network of underground sewer, water, and gas pipelines is difficult and costly. The problem is compounded by the significant impacts that a major repair or rehabilitation project can have on the daily life, traffic, and commerce of the area served by and along the pipeline in question. Trenchless pipe replacement, or pipe bursting, provides a trenchless alternative for the renewal of underground infrastructure. The process includes various static, hydraulic, and pneumatic methods of breaking an existing pipe and simultaneously installing, by pulling or pushing, a new pipe of equal or larger diameter. One of the greatest challenges facing acceptance of this renewal option is the issue of its effects on adjacent buried infrastructure. This paper describes a unique approach for monitoring subsurface ground movements during the pipe bursting process to assist planners and contractors in evaluating the risk of potential damage to surrounding structures. Initial field testing of this procedure on the Millstone Sanitary Trunk Sewer project in the City of Nanaimo, British Columbia is described. It is anticipated that adoption of this trenchless method of urban renewal will increase, as more techniques are developed to quantify the risks associated with soil movements.