Managing an HDD Pipeline Within an Active Deep-Seated Landslide

Abstract

The management of pipelines within active landslides is challenging, particularly when dealing with deep-seated landslides that pose significant risk to pipeline infrastructure. In this paper, the authors present a case-study of a pipeline operator managing a pipeline installed using horizontal directional drilling (HDD) within an active deep-seated landslide. The pipeline crosses a valley where both approach slopes are composed of valley scale landslides. The east slope landslide is presently being monitored using In-line Inspection surveys equipped with an Inertia Measurement Unit (IMU) tool and a suite of instrumentation, including Shape Accel Array (SAA) sensors and piezometers. These sensors provide near real-time data on the movement rates and deformation of the landslide and ground water levels present on the slope, allowing for better understanding of the landslide behavior. After pipeline impact from the landslide was identified from review of IMU bending strain data, a geotechnical drilling program was conducted to assess the feasibility of a deep valley-scale pipeline replacement using HDD methods and to better characterize the geologic properties at the crossing. This deep pipeline replacement was determined to be cost prohibitive. Long-term management of the pipeline includes planning for a shallow pipeline replacement using HDD methods when the existing pipeline approaches operational limits. A Finite Element Analysis was completed to assess the remaining strain capacity of the pipeline and to define action thresholds to trigger operational responses based on SAA displacement amounts. The framework discussed in this paper could be used for managing pipelines within deepseated landslides in similar situations.

Techniques