Geotechnical Instrumentation and Monitoring
MEG Consulting Limited (M+EG) has provided geotechnical consulting services for the evaluation of the impact of construction works in the vicinity of major sensitive structures, rail and lifeline alignments including buried utilities. Ground instrumentation programs have been developed to monitor ground vibrations, ground displacements and groundwater pressure build-up under static and/or dynamic conditions. The instrumentation program generally includes field supervision during the installation of the required equipment, instrument monitoring and data interpretation. This information is used to define protection schemes and/or remedial measures required to ensure proper performance of the structures/utilities adjacent to construction works.
In terms of specific recent projects, M+EG has provided geotechnical monitoring expertise in the following projects:
- Evaluation of ground vibrations induced by pile driving during the construction of 200th St. Overpass, Langley. (2006). Monitoring services included pre-construction definition of ground vibration baseline information (background noise), monitoring of 3 geophones placed on the ground surface at selected horizontal distances from the pile(s) being installed, evaluation of the variation of the peak particle velocity (PPV) of the ground with distance, and definition of safety corridors based on expected structural damages defined using past experience and published case histories.
- Effects of quarry blasting on possible ground settlements in the case of Towns et al, vs McCartney Construction Co. (2007). M+EG was requested to provide specialist consulting services for a legal case in the United States where a construction company was being sued by local residents who were claiming damages considered to result from blasting activities in a local quarry. The geotechnical services provided by M+EG included the evaluation of ground vibration information collected from a series of geophones installed at different distances from the quarry and monitored during the quarry blasting work, evaluation of recorded PPV values, assessment of potential ground displacements expected due to the blasting work, evaluation of ground displacement patterns/values reported as caused by the blasting work in the surrounding of the quarry, comparison of expected and observed ground displacements and the provision of recommendations on the potential mechanisms involving ground displacements due to blasting works.
- Monitoring of the Trans Mountain Pipe Line (TMPL) pipeline (Kinder Morgan) crossing south of Barnston Island in Langley, BC, during construction works for the Golden Ears Bridge Project. (2008). The monitoring services included the definition of the monitoring program and evaluation of the vibration and ground deformations to ensure they were below the thresholds or within the tolerances provided by Kinder Morgan. The monitoring plan included the use of ground displacement gauges, groundwater pressure meters and geophones. The operational safety limits were defined in terms of settlement/displacement levels and PPV levels to ensure proper operation of the TMPL throughout the construction period. M+EG was present on site during the monitoring to ensure the integrity of the pipeline. As a secondary impact, monitoring of an adjacent slope was included since the vibrations and pore pressure induced in the foundation soils had the potential to initiate lateral ground movements towards the installed pipeline.
- Development of an instrumentation and monitoring plan to evaluate the effect of pile installation and ground improvement works in the Central Segment (King Edward - Cape Horn Interchange) of the Port Mann Bridge/Highway 1 (PMH1) project (2009-2012). The monitoring and instrumentation plan included the installation of ground displacement survey points (i.e. surface gauges and inclinometers), groundwater pressure gauges and geophones in the vicinity and on the critical structures/utilities. The monitoring data were then used to define safety zones and/or protection schemes to ensure proper performance of the structures during the construction work. Ground deformation models were defined and provided to the structure/utility owners to define proper thresholds and/or safety limits to ensure proper operation throughout the construction period. An alert/warning system was developed for the critical structures/facilities in close collaboration with the owners to facilitate the implementation of remedial measures, if required. The scope of the monitoring plan involved the instrumentation and surveillance of the west abutment of the old Port Mann Bridge, CP railway alignment at the Cape Horn Interchange, Kinder Morgan Pipeline, GVWD&SS major sewer line, Terasen high pressure gas line and Telus Fiber Optic main line.