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Geohazard Identification, Monitoring and Mitigation Methods Using Soil Nail Technology for Coastal, Riparian and Water Infrastructure

By:Martin P. Derby, P.G., CPG

Director – Coastal and Riparian/Geohazard Mitigation GeoStabilization International

Presentation Overview/Abstract:

Geohazards have the potential to adversely impact infrastructure along US waterways. Unstable
slopes, seismic, subsidence, and hydrotechnical (water erosion) hazards are just a few types of
geohazards that will be discussed in detail. Performing geohazard identification/assessments
along shorelines assists owners and operators in determining if a natural hazard may impact their
assets. Geohazard monitoring provides the ability for owners to make more proactive decisions
regarding various geohazards that may threaten their infrastructure assets and the public.
Additionally, geohazard monitoring provides a meaningful decision framework to assess risk and
prioritize mitigation efforts. Various geohazard monitoring methods for unstable slopes will be
discussed. These methods include in-situ or downhole instrumentation (i.e., inclinometers, shape
arrays, piezometers, etc.), and surface instrumentation (i.e., wireline extensometers, physical
survey markers, GPS, etc.), as well as other advanced remote sensing methods including: InSAR
(satellite), ground based InSAR, and LiDAR (airborne). There are many types of geohazard
mitigation methods for unstable slopes. An engineering method to mitigate unstable natural
slopes or construct new or over-steepened slopes, include the method of soil nailing. The soil
nailing practice involves drilling solid or hollow bar components to depths specified by a
geotechnical engineer. The inserted nails are usually grouted and installed at a slight downward
inclination, with the solid/hollow bar elements installed at regular spaced points across the slope.
Steel-reinforcing rigid shotcrete or flexible wire mesh is often applied as facing to add strength
and erosion control. This presentation will include several examples of soil nail mitigation along
our US coasts, at a Georgia Military Base, along rivers as well as an example of a slope mitigation
for a dam.

Martin Derby - Director of Coastal & Riparian/Geohazard Mitigation