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Automated tiltmeter monitoring of bridge response to compaction grouting
In June of 1999, Applied Geomechanics was retained by Hayward Baker to monitor the Laurel Street Bridge in Santa Cruz during compaction grouting of the ground beneath the bridge footings. This work was performed as part of an extensive program of seismic upgrades to many of California's bridges after the 1989 Loma Prieta earthquake. The project specifications for the compaction grouting put stringent requirements on the allowable amount of bridge movement during the grouting process. Hayward Baker recognized that tiltmeters were one of the few instruments that could measure movements small enough to satisfy the specifications. The tiltmeters used for this application are capable of detecting 0.001 inch (0.0254 mm) deflections over a 100 foot (30.48 m) span. Continuous monitoring of the tiltmeters was implemented to provide instant notification of vertical deflections greater than 0.1 inch (0.254 mm). However, the threshold alarming was complicated by the fact that the normal diurnal movement of the bridge due to thermal expansion and contraction is of the same order of magnitude. Therefore, the normal daily movement of the bridge was modeled with a sine wave, and the alarm thresholds were based on the difference between the model and the recorded data. This model is relatively easy to program within a datalogger and results in alarms that respond to grout-induced movement rather than thermoelastic bridge deformation.
Automated tiltmeter monitoring of bridge response to compaction grouting
In June of 1999, Applied Geomechanics was retained by Hayward Baker to monitor the Laurel Street Bridge in Santa Cruz during compaction grouting of the ground beneath the bridge footings. This work was performed as part of an extensive program of seismic upgrades to many of California's bridges after the 1989 Loma Prieta earthquake. The project specifications for the compaction grouting put stringent requirements on the allowable amount of bridge movement during the grouting process. Hayward Baker recognized that tiltmeters were one of the few instruments that could measure movements small enough to satisfy the specifications. The tiltmeters used for this application are capable of detecting 0.001 inch (0.0254 mm) deflections over a 100 foot (30.48 m) span. Continuous monitoring of the tiltmeters was implemented to provide instant notification of vertical deflections greater than 0.1 inch (0.254 mm). However, the threshold alarming was complicated by the fact that the normal diurnal movement of the bridge due to thermal expansion and contraction is of the same order of magnitude. Therefore, the normal daily movement of the bridge was modeled with a sine wave, and the alarm thresholds were based on the difference between the model and the recorded data. This model is relatively easy to program within a datalogger and results in alarms that respond to grout-induced movement rather than thermoelastic bridge deformation.
Automated tiltmeter monitoring of bridge response to compaction grouting
Schuyler, Jeffrey N. (author) / Gularte, Francis (author)
Nondestructive Evaluation of Highways, Utilities, and Pipelines IV ; 2000 ; Newport Beach,CA,USA
Proc. SPIE ; 3995
2000-06-09
Conference paper
Electronic Resource
English
Geotechnical Instrumentation News - Real-Time Tiltmeter Monitoring During Compaction Grouting
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