Session: 06-05-01 Strain Demand

Paper Number: 133093

133093 - Correlation of IMU Bending Strain Features to Geohazard Locations: An Update 

Abstract: 

This paper presents an update to the results of Theriault et al. (2020) on the correlation of single-run IMU bending strain features to geohazard locations.  Theriault et al. reviewed over 4,600 IMU-identified bending strain features from a single pipeline operator located in a variety of geographic settings and concluded that while the overall correlation between ILI vendor bending strain features and geohazards is low (about 94% not correlating with geohazards, based on the analysis of Theriault et al.), higher maximum magnitude and in particular, higher horizontal magnitude, as reported by the ILI vendors, are strongly correlative to geohazard occurrence, rising to over 50% correlation when horizontal magnitude is greater than 0.14%.

This paper presents the result of a review of over 17,000 IMU single-run bending strain features for two pipeline operators as reported by ILI vendors to provide a more statistically significant and nuanced analysis of the correlation of IMU bending strain with geohazards.  The objective of this paper is to demonstrate how bending strain magnitude from a single IMU run can be a useful tool to perform a screening to identify locations that likely have been affected by geohazards to allow for prioritized further evaluation and, in some cases, to identify locations where the visual evidence of the geohazard may have been removed through prior activities.    

To perform the review, reported bending strain features were cross-compared with possible geohazards identified through desktop and field geomorphic evaluation.  Each reported bending strain feature was assigned a location, such as a landslide, river channel, road crossing, utility crossings, pipe replacement locations, and similar, to distinguish likely geohazards from other locations and to distinguish geohazard types. 

The paper shows that approximately 6.5% of the reported bending strain features correlated to a geohazard (93.5% not correlating).  The vast majority of the reported bending strain features (~81%) were less than 0.2%, and at that magnitude and less, the correlation with likely geohazard is less than 5.5%.

This correlation increases significantly with increased bending strain magnitude.  At a maximum reported magnitude of 0.3% and greater, the correlation between bending strain features and likely geohazards rises to over 22%, and at a maximum magnitude of 0.4% and greater, it rises to a correlation of over 45%.

A stronger correlation is found between the maximum reported horizontal magnitude and geohazards.  At horizontal magnitudes as low as 0.1% and greater, the correlation between reported bending strain features and likely geohazards is over 24%.  At reported horizontal magnitudes of 0.3% and greater, the correlation between reported bending strain features and likely geohazards increases to almost 60%. 

Based on this review, results similar to those of Theriault et al. were observed but with lower correlation percentages at higher magnitudes.  While the overall conclusions support the prior work by Theriault et al., the results of this analysis suggest that the conclusions of Theriault et al. may have been skewed by a relatively small sample size, particularly at higher magnitudes, and that while the overall correlation between high maximum magnitude and horizontal magnitude and geohazards is strong, geohazards are not the only sources of such conditions.  As more data is collected and analyzed a better representation of the correlation between ILI vendor-reported IMU bending strain features, geohazard occurrence, and other causes can be established. 

The paper provides further discussion and analysis of the correlation with individual geohazard types, the relative prevalence of reported IMU bending strain features by magnitude, and where multiple IMU runs have been performed, the correlation between reported strain change features and geohazards.  Additionally, the paper provides recommendations for further research and evaluation of the usage of IMU bending strain features to identify geohazards and assess their effects on pipelines.

Presenting Author: Alexander Mckenzie-Johnson Geosyntec

Presenting Author Biography: Alex McKenzie-Johnson is a landslide enthusiast and geologist who spent his formative years roaming the hills and mountains of the Pacific Northwest. Alex’s approximately two decades of professional geology experience have been primarily focused on the management of pipeline geohazards across North America as both a consultant and an employee of a major pipeline company. Alex was the lead author and project manager of the 2020 INGAA Foundation Report “Guidelines for Management of Landslide Hazards for Pipelines," and the 2023 INGAA Foundation Report "Recommended Practice for Pipeline Integrity Management of Landslide Hazards." Alex was also a key contributor to the 2018 PRCI Report “Guidelines for Management of Geohazards Affecting the Engineering and Construction of New Oil and Natural Gas Pipelines," the 2019 ISO Standard 20074 “Petroleum and natural gas industry — Pipeline transportation systems — Geological hazard risk management for onshore pipeline,” and the 2023 INGAA Foundation Report, "Framework for Geohazard Management."

Alex currently leads a team of geologists, geological engineers, and geotechnical engineers at Geosyntec Consultants, Inc. that provides support for many aspects of pipeline geohazard management, including programmatic development of processes and procedures, threat identification and assessment, installation, and implementation of instrumentation and monitoring, and design and oversight of mitigation measures. Alex resides in The Woodlands, Texas, on the north side of the Houston metropolitan area.

Authors:

Alexander Mckenzie-Johnson Geosyntec
Bailey Theriault Geosyntec
Rhett Dotson D2 Integrity
James Hart SSD, Inc.
Patricia Varela Geosyntec