Image of the side of a mountain showing a past landslide.

| Case Study

Detecting Geohazards in Unpiggable Pipelines

High-resolution stress assessment using large stand-off magnetometry

Pipelines operating in areas affected by subsidence or landslides can experience mechanical loading as a result of ground movement. Detecting and assessing these stresses can be difficult, especially when conventional in-line inspection methods are not feasible or when a rapid response is required. To help operators proactively manage these risks, ROSEN offers large stand-off magnetometry (LSM), a non-intrusive aboveground inspection method that identifies bending, buckling and localized stress concentrations in buried pipelines, without excavation and without any impact on operations. This technology can be hand carried or drone deployed.

The challenge

The operator was responsible for a pipeline section situated in a region known for geohazard activity, where ongoing ground movement threatened the pipeline’s integrity. The operator evaluated monitoring options such as strain gauges and fiber-optic systems, but dismissed them due to the high installation effort required for excavation. ROSEN proposed a non-intrusive, above-ground assessment, capable of identifying changes in the pipeline route, variations in depth of cover, and stress-related anomalies. All supported by high-precision GPS data and inspection repeatability allowing for repeat monitoring.

A labeled graphic that shows a pipeline movement with a white pipeline on a light blue underground.

Figure 1: Schematic representation of a pipeline affected by a landslide, illustrating ground-movement direction, displaced alignment, and the resulting high bending loads.

Our solution

ROSEN applied its LSM technology to provide an assessment of mechanical stresses and geometrical anomalies acting on the buried pipeline. Magnetic field measurements were collected from the surface without any need for excavation or alteration of the pipeline's operational parameters. In parallel, data with centimeter-level accuracy was gathered, enabling precise spatial X, Y, Z coordinate alignment of every measurement.The collected magnetic data enabled ROSEN to determine the pipe- line’s precise position, which could be compared to as-built drawings or previously recorded GPS data, to allow for the identification of movement of the pipeline. In addition, direct comparison of the LSM data with future inspections will provide further proof of movement, helping the operator to determine whether there are active geohazards in the area or not. LSM also provides a depth-of-cover assessment, which is essential for not only detecting potential threats arising from third party damage but also upheaval or buckling where the pipeline rises or settles unevenly. By analyzing variations in the magnetic field, the advanced ROSEN algorithms produced detailed stress information and highlighted stress concentration zones along the pipeline. These zones were quantified using Von-Mises stress relative to the pipeline’s Specified Minimum Yield Strength (SMYS), and any areas approaching critical levels were precisely located to enable targeted follow-up activities. This approach provided a comprehensive, above-ground integrity assessment with no disruption to normal operations.

Strip chart of the depth of cover of a pipeline at risk from ground movement.

Figure 2: The two strip charts above show the pipeline depth of cover and the stress profile of the area of the pipeline identified as at threat from ground movement. Pipeline upheaval of more than two-times the pipe diameter was identified in this 10-meter section of the survey. In the same location, there was an abnormal increase in Stress Concentration Zones (SCZs) with higher than normal operational stress-levels.

Your benefit

The LSM inspection provides operators with a precise location of the pipeline route, and by comparing this to other available data, enables a compre-hensive view of whether the pipeline has moved, or not. When coupled with ROSEN’s geohazard assessment and management services, this data can help determine whether ground movement has influenced the pipeline, and offers a reliable means of monitoring its condition over time.

The combination of the data recorded in-field and desktop studies conducted by ROSEN’s technical experts provides operators with targeted and optimized mitigation and monitoring recommendations, specifically in areas that need them. This enables informed and targeted integrity decisions, optimizing costs while maintaining both operational and environmental safety.

Reliable detection of pipeline movement and depth-of-cover changes that can enable proactive mitigation before failure by bending or buckling.
Precise location of areas with high stress, supporting efficient follow-up activities.
Non-intrusive, above-ground inspection requiring no excavations, no operational changes and no contact with the pipeline.
Data collection along the entire route, offering high resolution and insight to the whole pipeline, as opposed to only point-based field measurements.
Proven repeatability of the assessment, enabling operators to monitor stress development over time and identify emerging geohazard impacts before they impact operations.
Offers a comprehensive evaluation over the whole survey length from geohazard impacts. The ROSEN geohazard assessment portfolio provides operators not just with an inspection, but clear guidance and support with how to manage impacts and further mitigation design.

You want to know how LSM could benefit your specific pipeline challenges?
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