Challenges in planning highway improvements in landslide terrain
Abstract
Alberta Transportation (AT) is responsible for providing a safe, innovative, and sustainable provincial transportation system in Alberta. This responsibility includes the planning, design, construction, and maintenance of public roadways. Economic and expansion pressures place demands on the roadway network capacity. In order to facilitate a rational and sustainable highway expansion program, AT undertakes numerous Functional Planning Studies (FPS) well in advance of any engineering design or construction. A FPS is a multidisciplinary project that requires input for highway planning, traffic forecasting, geometric and drainage considerations, aboriginal consultation, environmental studies, surfacing strategy considerations, and geotechnical impact. The results of these inputs are captured in the FPS, from which a long term work plan can be rationally formulated. Numerous geohazard sites, mostly landslides, impact existing public roadways, associated infrastructure and surrounding environs. These geohazard sites can play a crucial role in determining the outcome of a FPS. To manage the risks posed by such geohazard sites, AT has implemented the Geohazard Risk Management Program (GRMP) to identify, investigate, instrument, monitor and, if required, repair such sites. The FPS includes a geotechnical review of the impact of known GRMP sites. The completion of these reviews requires a practical understanding of highway geometric considerations, construction methodology and the geohazard mechanisms that affect the existing or proposed alignments. Two FPS case histories are provided which illustrate the impact of large landslide geohazards on the outcome of planning studies. Conclusions related to findings from these FPS in relation to the geotechnical input required and influence on future highway works are also provided.