Slip Stick – Innovative Advancement in Subsurface Ground Movement Monitoring

Abstract Landslides are an example of an unpredictable geologic hazard with the potential for catastrophic consequence to buried pipelines. Once identified, landslide instrumentation and associated monitoring programs are typically developed and implemented to better manage landslide-related threats for infrastructure including buried pipelines. Often this has included the use of inclinometer casing installed into boreholes advanced using a drill rig. This paper will present the results of prototype testing of an instrument, called Slip Stick, intended to provide inclinometer grade deformation information and can be installed using simple handheld methods without the need to mobilize heavy equipment. Traditional inclinometers and similar technologies are the current best practices for in situ monitoring of ground movement. These monitoring techniques inform operators of both the depth of the failure plane and the estimated magnitude of soil movement. This data is used to provide warnings of potential stresses on pipelines as well as information to enable effective landslide mitigation practices. The Slip Stick will enable agile implementation of deterministic in situ monitoring that supports landslide-related risk reduction for buried pipelines. A persistent challenge when installing traditional inclinometers for subsurface ground movement monitoring is being able to rapidly deploy new instrumentation, commonly in hazardous locations and in steep terrain. Often regulatory permitting, landowner agreements, and improved access infrastructure are a prerequisite to mobilization of drill rigs and associated equipment required for installation. Inclinometer monitoring technologies also require specialized casings installed within boreholes. Implementation of these monitoring technologies can be an expensive and time-consuming endeavor. The Slip Stick instrument is installed directly in the overburden and includes a chain of sensors that measure tilt between individual segments. Like inclinometers, data collected by the Slip Stick can be used to better understand if ground movement has engaged a pipeline and provide engineering information for potential mitigation solutions. An overview of the Slip Stick installation processes is highlighted to illustrate the potential cost savings of the Slip Stick casing-less instrumentation as compared to traditional inclinometers. The product was also developed to support both a telemetry system for near-real time remote monitoring, as well as data stored on site with a data logger. Results of ground movement are calculated from measured tilt and presented graphically to develop a profile of the Slip Stick by resolving tilt between individual sensor segments, similar to standard inclinometer profiles. Results from lab-based testing illustrating both the ability to withstand environmental conditions of a casing-less installation as well as a direct comparison of movement profiles are presented. Early stages of field-based testing and the 2024 development plan for preproduction research and development, highly accelerated life testing, and extensive field pilot installations are outlined in this paper.