Bridge Abutment Monitoring

Background

Location: British Columbia, Canada

FortisBC Inc. (electricity and natural gas) is located in British Columbia and is a subsidiary of Fortis Inc., Canada’s largest private utility company. They serve more than 1.1 million customers in over 135 communities and operate approximately 48,000 kilometres of pipelines.

Objective

A natural gas line that has been in service since the 1950s was still considered safe, but as part of their proactive commitment to safety and environmental responsibility, FortisBC wanted to upgrade the line before any safety issues may arise in the future. The old 20-inch line would be upgraded to 30 inches, but a part of the line being upgraded required excavation near an existing bridge abutment. Project consultants required assurance that the bridge’s structure wouldn’t be adversely affected by the necessary excavation for the upgrade.

Challenges

The allowable lateral displacement of the concrete bridge abutment was minuscule—millimeters of movement were perceived as an unacceptable risk to the health of the bridge. Concerns were raised about the geotechnical conditions beneath the abutment footing, and how the groundwater or additional loads could cause failures in the soil.

Solution

To measure the lateral displacement, RST provided a rental Inclinometer System to monitor two inclinometer boreholes near the abutment area. The boreholes had RST’s Inclinometer Casing installed within them. To assess the stability of the earth beneath the abutment, RST Piezometers were installed to monitor pore water pressures.

Benefits

RST was able to quickly provide a reliable and accurate monitoring solution that accommodated FortisBC’s budget. RST’s Field Services Team provided technical services for installation of instrumentation and worked directly with a drilling company to install the inclinometer casing on behalf of FortisBC. Quick installation—installed over the course of only three, one-day site visits.

Results

Data was accurate and reliable during the one month of the instrumentation’s required service. FortisBC was able to conclude that the bridge abutment was not adversely affected by the excavation and the pipeline upgrade could proceed without sacrificing public and environmental safety. Disruption to the bridge would have caused significant financial impact.

Instrumentation

In-Place Inclinometers were installed at borehole depths of 12–14 m.
Tilt Meters on each column at 2 m above the ground—for tilt measurement in north south direction. Standpipe Piezometers at 3–6m deep—screened in peat and clay.
Vibrating Wire Strain Gauges.

Partners Featured In This Success Story

FortisBC

Speak with an Expert

I’m very happy with the quality of the instrumentation and technical support from RST, as always. They worked with us from the initial stages of the project to ensure that we were fully prepared and equipped to use the RSTAR network for the first time. They delivered everything within the tight project time frame to ensure that there were no delays on site, and the submersible tilt meters looked like new even after over twelve months of being submerged in Thames water!
 
-Richard Lipscombe, BEng (Hons), Director & Principle Consultant - RL Geotechnical Ltd