Session: 04-03-03 Geohazard Management - Landslides - Part II

Paper Number: 87081

87081 - Stress Relief Excavation for Pipeline Geohazard Mitigation 

Due to the long linear nature of pipeline infrastructure, they cross various slope geometries and geologies and are susceptible to various geohazards, including landslides and subsidence. These ground movements can potentially induce axial, bending, and torsional stresses in pipelines. One of the methods to mitigate the effects of perminant ground deformation on pipelines is stress relief excavation. In this approach, the soil above and around the pipeline in the affected area is excavated to allow the pipeline to rebound and relieve some of the accumulated elastic stresses in the pipeline. Stress relief excavations also allow for the installation of subsurface drainage within the pipe trench. Additionally, exposing the pipeline through stress relief excavation provides the opportunity to install geotechnical instrumentation such as strain gauges on the pipeline to monitor future applied stresses. Stress relief excavation trenches can be backfilled with a layer of non-cohesive deformable sand around the pipeline to reduce the effects of future ground movements on the pipeline. Stress relief excavations can be performed along with other mitigation measures such as soil nails or retaining walls, depending on the objective of mitigation.

This paper presents the results of five case studies of stress relief excavations. These case studies include a variety of situations in which the stress-relief excavations were performed. Various directions of landslide movement with respect to pipeline and extents of excavation. A summary of pipeline out-of-straightness and IMU bending strain will be presented. The results of pipeline rebound during the stress relief excavation will be presented and discussed. The strain measurement using strain gauges during stress relief excavation will be discussed.  This paper will discuss the considerations about selection of stress relief excavation as a mitigation option, the sequence of performing stress relief excavation, stability of landslide and trench while exacavating within landslide mass, and quality control and monitoring requirements during the stress relief excavation.

Presenting Author: Amir Ahmadipur Geosyntec Consultants, Inc.

Presenting Author Biography: Dr. Ahmadipur is a licensed professional geotechnical engineer with seven years of experience in a wide range of geotechnical engineering topics. He is experienced in landslide mitigation design, geotechnical instrumentation, monitoring and data management, geotechnical analysis and design, and foundation engineering.