Posts Tagged ‘geohazard’

Effect of Geohazards on Pipelines


When planning a pipe route or evaluating an existing one the associated geohazards along that one should be considered. Those which are most commonly considered geohazards are landsliding, land subsidence from underground mining or karst, and earthquake induced ground motions (i.e., faulting, liquefaction, lateral spreading and landsliding). This can determine whether that investigated route is viable or not. Given the long line reaches, the operator can struggle with determining which areas along the alignment contain the most critical geohazard(s). Whether along a proposed or existing route is best done by a two-phased approach. Phase 1 would identify those geohazard areas that can affect the pipeline during its lifetime, and Phase 2 would identify those geohazard areas which may potentially exceed the operator’s acceptable risk threshold.

The first step when evaluating the vulnerability of the pipeline to a geohazard is the assessment of the event (or occurrence) and severity probabilities (or in other words, what is the chance of a certain magnitude of ground motion). However, even more important is the assessment of the behavior or damage potential of the pipeline to the concerned geohazard movement that could occur during the expected operational lifetime of the line. The key overall assessment here then becomes whether the determined damage potential (occurrence and associated severity probabilities) exceeds the threshold of acceptable exposure level by the operator/owner. Evaluating the damage potential of certain site conditions many times requires numerical analysis in order to account for all the important ground movement, backfill, and pipeline conditions.

For any geohazard condition, the damage analysis should consider the primary modes of pipeline deformation, which are tensile stretching, buckling and bowing (aka upheaval buckling). These pipe deformations are a function of the nature of the ground movement the pipeline is exposed to. For example, significant tensile and compressive deformations can result from differential vertical (settlement) and lateral ground movement perpendicular to the pipeline, as well as, slippage between the ambient backfill and the line from lateral ground movement along the pipe.


Where the risk is deemed too high, there are many ways to mitigate the damage or hazard potential, these include:

• Relocating the line;

• Telemetric monitoring of pipe deformations;

• Designing for the ground movement;

• Reducing the backfill/pipe friction/adhesion against slip;

• Using restraints against upward bowing; and

• Installing stress relief joints.


More information on this topic can be obtained from below.

BLOG: How to Handle Geohazard Risks

Engineering UPDATE Issue #4 entitled: Improvement of Mine Support Saves Pipeline from Subsidence event

Engineering UPDATE Issue #25 entitled: Transmission Pipeline Subsidence from Mining

Engineering UPDATE Issue #44 entitled: Property Management System for Geotechnical Risks

Engineering UPDATE Issue #51 entitled: Upheaval Buckling of Pipelines

How to Handle Geohazard Risks

Geohazards can be described as unexpected land movement events which can potentially result in hazardous conditions or significant damage to infrastructure. Land movement categories that are more commonly considered geohazard events are land subsidence for underlying karst or underground mining, landsliding, and earthquake motions. In addition to the movements themselves, the ramifications of these earthquake motions can be exhibited in various forms including fault displacements, land subsidence, liquefaction, lateral spreading, and landsliding.

Courtesy of the University of Missouri, 2012.

USGS air photo of the Mud Creek landslide, taken on May 27, 2017.

In handling a geohazard risk, risk evaluation is very important. The risk evaluation of a geohazard will determine whether the project will proceed, and with the go-ahead, the associated costs of the risk mitigation measures that would be taken. These costs can be significant. Therefore, having a superior understanding of the geohazard is imperative. Because of the importance of the geohazard risk assessment, which merits an extensive investigation, it should be performed by an expert experienced and specialized in the geohazard concern. In other words, the assessment falls outside the general practitioner in the associated discipline or a geotechnical engineer. For the allocated investment, the geohazard expert will provide a far superior assessment. In fact, even when the investigation budget is limited, it should be done by the geohazard specialist given their ability to extend the available project data collected.

Addressing a geohazard requires an understanding of all the geohazard-site conditions and their implications. This involves predicting the frequency of an occurrence as well as the probability spectrum of ground movement severity. Most importantly, however, is the assessment of the probability spectrum of damage potential being considered. The potential is most important to the project decision making process as this damage spectrum is evaluated against the damage threshold of the risk manager to determine the acceptable risk. Unless there are lender restrictions, commercial risk decision makers may be under greater stress to relax the acceptable risk threshold due to competitive economics. The acceptable risk results in the establishment of mitigation measures and risk protocols for effective and rapid event reactions where needed.

More information can be obtained on this topic form below.

Engineering Update #44 entitled: Property Management System for Geotechnical Risks

BLOG: How to Find a Geotechnical Engineering Expert

BLOG: What is Karst Subsidence

BLOG: What is Mine Subsidence

BLOG: What to Look for When Selecting a Geotechnical Engineering Company

BLOG: Landsliding What to Do

BLOG: What to Look for in a Mine Subsidence Expert

BLOG: Landslides

BLOG: What to Look for in a Karst Subsidence Expert