Session: 06-05-01 Strain Demand

Paper Number: 134063

134063 - Vibrating Wire Strain Gauges for Pipeline Geohazard Monitoring: Operation, Failure Mechanisms, and Data Interpretation 

Abstract: 

The purpose of this paper is to review and document the functionality of spot-weldable vibrating wire (VW) strain gauges for geohazard monitoring of pipelines. The paper presents best practices for installation and interpretation of strain gauge data.  Additionally, this paper examines means to evaluate questionable data and how to distinguish indications of malfunctioning or error from actual strain changes resulting from geohazard effects on a pipeline.  Finally, the paper examines some of the reasons why strain gauges may not function correctly or have erroneous readings, and how to correct these issues through a quality control program. 

This paper has been compiled from experience installing and monitoring thousands of VW strain gauges for pipelines from many geographic environments across the United States.  The first section of the paper provides a brief introduction to VW strain gauge instrumentation, including the components of a VW strain gauge system and how the technology works.  The second section presents best practices for installation of VW strain gauges on pipelines, including mechanisms for implementing effective quality control designed to minimize the number of gauges that malfunction or do not report.  Based on the authors’ experiences, when correctly installed using these quality control practices, fewer than 1% of the VW strain gauges fail on an annual basis. 

The third section summarizes the most common strain gauge failure mechanisms, based on the authors’ experiences with several pipeline operators. Finally, the fourth section presents guidelines for interpreting VW strain gauge data, including methods to distinguish actual measurements of strain from erroneous readings, based on experience reviewing and interpreting thousands of strain gauges installed on operating pipelines.   This section provides examples of commonly seen responses, such as gradually increasing strain from slow-moving geohazards and suddenly increasing strain from rapidly-moving geohazards, non-injurious changes in strain resulting from seasonal temperature changes and operational pressure adjustments, clearly erroneous measurements from malfunctioning systems, and questionable data which may have several interpretations.  For the questionable data, the paper provides possible explanations for these results and provides guidance on how use of other on-site instrumentation can help to resolve ambiguous data to distinguish actual strain change from erroneous results.

Presenting Author: Amir Ahmadipur Geosyntec Consultants, Inc.

Presenting Author Biography: Amir is a licensed geotechnical project engineer with Geosyntec Consultants. He earned his master’s degree in soil mechanics from Imperial College London, and Ph.D. in Geotechnical Engineering from Penn State. He has been a part of Geosyntec’s pipeline geohazard mitigation group for the past 6 years working closely with several major pipeline operator clients. He has experience in a wide range of geotechnical engineering and pipeline geohazard topics including landslide mitigation design, geohazard assessment, geotechnical site investigation, geotechnical design for compressor stations, and instrumentation, monitoring and data management for pipelines.

Authors:

Suraj Khadka Geosyntec Consultants, Inc.
Amir Ahmadipur Geosyntec Consultants, Inc.
Arash Mosaiebian Enbridge
Ali Ebrahimi Geosyntec Consultants, Inc.