Geotechnical Site Investigation in
Energetic Nearshore Zones:
Opportunities & Challenges
Nina Stark
Virginia Tech, Charles E. Via Department of Civil & Environmental Engineering
Why site investigation in shallow water
environments, and the nearshore zone?
Many modern challenges to society are associated to
processes in the nearshore zone and at the shoreline:
• Coastal erosion and land loss;
• Protection of coastal communities, infrastructure and ecosystems during extreme events and with climate change;
• Scour at coastal structures;
• Navigation, port and waterway infrastructure;
• Beach erosion;
• Etc.
Why site investigation in shallow water
environments, and the nearshore zone?
Coastal erosion and land loss:
Nags Head, NC, USA; June 2016
Why site investigation in shallow water
environments, and the nearshore zone?
Coastal erosion and land loss:
Gold Coast, Australia; September 2016
Why site investigation in shallow water
environments, and the nearshore zone?
Beach erosion:
the.honoluluadvertiser.com
www.soest.hawaii.edu
Why site investigation in shallow water
environments, and the nearshore zone?
Coastal erosion and land loss:
Herschel Island, Yukon, Canada; July 2014
Why site investigation in shallow water
environments, and the nearshore zone?
Coastal erosion and land loss:
LaCoast.gov/LandLoss
Why site investigation in shallow water
environments, and the nearshore zone?
Protection of coastal communities, infrastructure and
eco-systems during extreme events and with climate
change:
Flood damage from storm surge during
Hurricane Sandy. Photo: Master Sgt. Mark
C. Olsen/U.S. Air Force (blog.ucsusa.org)
Why site investigation in shallow water
environments, and the nearshore zone?
Protection of coastal communities, infrastructure and
eco-systems during extreme events and with climate
change:
Why site investigation in shallow water
environments, and the nearshore zone?
Protection of coastal communities, infrastructure and
eco-systems during extreme events and with climate
change:
force-project.eu
Reef devastated by a hurricane. Etang
Sale, Réunion
(datamanagement.reefcheck.org)
Why site investigation in shallow water
environments, and the nearshore zone?
Scour at coastal structures:
AV 11
Accumulation
Erosion
courtesy of
M. Lambers-Huesmann
(BSH)
Why site investigation in shallow water
environments, and the nearshore zone?
Navigation, waterways and ports:
Fluid mud monitoring in the Port of Antwerp, Belgium.
Stark et al. (2014);
courtesy of P. Staelens (dotOceans)
Why site investigation in shallow water
environments, and the nearshore zone?
Many modern challenges to society are associated to
processes in the nearshore zone:
• Coastal erosion and land loss;
• Protection of coastal communities, infrastructure and ecosystems during extreme events and with climate change;
• Scour at coastal structures;
• Navigation, port and waterway infrastructure;
• Beach erosion;
• Etc.
Sediment Dynamics!
Sediment Dynamics
Hydrodynamics
Morphology
Sediments
Sediment Dynamics
At the beach:
Sediment Dynamics
At the beach:
surf
dune
swash
intertidal zone
partially saturated
Sediment Dynamics & Geotechnics
Predicting Initiation of Particle Motion
Shields (1936)
Predicting Initiation of Particle Motion
Hjulstrom diagram modified by Sundborg (1956)
Predicting Volumetric Change
Coco et al. (2014)
Prediction of Scour Depth
Falcone & Stark (2016)
Predictions of Erosion & Geotechnics
Despite great advancements in the prediction of morphological
change & erosion, the accurate prediction of the sediment dynamic
response to energetic forcing is still difficult.
The detailed understanding of the impact of geotechnical
properties on sediment dynamics and vice versa can contribute to
the improvement of prediction methods.
Predictions of Erosion & Geotechnics
And research is already ongoing…
BUT there is a pressing need for more field data,
resulting from limitations of field methods.
Predictions of Erosion & Geotechnics
And research is already ongoing…
BUT there is a pressing need for more field data,
resulting from limitations of field methods.
Possible opportunities:
• Portable Free Fall Penetrometer
• Embedded Pressure Transducers
Portable Free Fall Penetrometers
What penetrometer characteristics do you need to investigate
processes related to sediment dynamics?
•
Stable free-fall performance in active hydrodynamics
•
Robustness
•
Easy handling from vessels of opportunity
•
Vertical resolution < 1 cm (i.e., a fast data logger)
•
A large measurement range (accommodating very soft fluid-like soils to very stiff fine
sands)
A possible solution: Torpedo/Projectile-shaped penetrometers
Portable Free Fall Penetrometers
Torpedo-shaped Small-scale Penetrometers
XBP (after Aubeny and Shi 2006)
blueDrop (after BlueCDesigns 2013)
blueDrop (after Stark et al. 2016)
Nimrod (after Stark et al. 2011)
Nimrod (after Stark et al. 2013)
Portable Free Fall Penetrometers
Torpedo-shaped Small-scale Penetrometers
Stark et al. (2013)
Chesapeake Bay 2016
Waikiki 2008
Lake Geneva, SUI
2011
Sydney, NS 2013
Portable Free Fall Penetrometers
Raw Data
Stark et al. (2016)
Portable Free Fall Penetrometers
Data Analysis - Deceleration
Stoll et al. (2007)
Stark et al. (2016)
Stark and Wever (2009)
Portable Free Fall Penetrometers
Data Analysis – Cone Resistance
Stoll et al. (2007);
XBP
Stephan et al. (2015)
LIRmeter (lance-like free-fall penetrometer)
Portable Free Fall Penetrometers
Data Analysis – Soil Strength
Aubeny and Shi (2006)
XBP
Morton et al. (2016)
free-fall sphere
Portable Free Fall Penetrometers
Data Analysis – Quasi-Static Bearing Capacity
Deceleration
Pore Pressure
Power Law
Integration
Dynamic Sediment Resistance
Dayal and Allen (1973)
Quasi-Static
Sediment
Resistance
Velocity
Terzaghi (1943)
Dynamic
Bearing
Capacity
Dayal and Allen (1973)
Quasi-Static Bearing Capacity
Penetration
Surface
Portable Free Fall Penetrometers
Data Analysis – Quasi-Static Bearing Capacity
Lucking et al. (subm.)
blueDrop
Portable Free Fall Penetrometers
Data Analysis – Quasi-Static Bearing Capacity
Deceleration
Drag? Soil
buoyancy?
Power Law
Dynamic Sediment Resistance
Integration
?
Dayal and Allen (1973)
Strain rate
factor?
Velocity
?
Pore Pressure
Quasi-Static
Sediment
Resistance
?
?
Pore pressure
response for
high
velocities?
Terzaghi (1943)
Dynamic
Bearing
Capacity
Dayal and Allen (1973)
Quasi-Static Bearing Capacity
Penetration
Surface
Projected or
tip mantle,
etc.?
?
Portable Free Fall Penetrometers
Data Analysis – Quasi-Static Bearing Capacity
Deceleration
Drag? Soil
buoyancy?
Power Law
Dynamic Sediment Resistance
Integration
?
Dayal and Allen (1973)
Strain rate
factor?
Velocity
?
Pore Pressure
Quasi-Static
Sediment
Resistance
?
?
Pore pressure
response for
high velocities?
Terzaghi (1943)
Dynamic
Bearing
Capacity
Dayal and Allen (1973)
Quasi-Static Bearing Capacity
Penetration
Surface
Projected or
tip mantle,
etc.?
?
Portable Free Fall Penetrometers
Data Analysis – Pore Pressure
hydrostatic pressure based on echo sounder water
depth
Difference between
measured pressure
at impact and water
depth can be
explained with the
Bernoulli effect.
Measured pressure
at rest in sediment
seems to be
governed by pore
pressure response,
and the decreased
pressure during
embedment.
Lucking et al. (subm.)
Portable Free Fall Penetrometers
Data Analysis – Sediment Dynamics with Currents
Stark et al. (2011)
Portable Free Fall Penetrometers
Data Analysis – Sediment Dynamics with Waves
Albatal et al. (subm.)
Stark and Kopf (2011)
Portable Free Fall Penetrometers
Discussion – Opportunities & Challenges
Things that work well…
•
Deployment (ease of handling, robust, etc.)
•
Data acquisition (reliability, accuracy)
Dorvinen et al. (subm.)
•
Identification of point of impact
•
Resolution of vertical stratification
(resolution <1 cm)
•
Correlation of measurements to soil type &
properties
•
Correlation of measurements to sediment
dynamics
Dorvinen et al. (2015)
Portable Free Fall Penetrometers
Discussion – Opportunities & Challenges
Things that work well…
•
Deployment (ease of handling, robust, etc.)
•
Data acquisition (reliability, accuracy)
•
Identification of point of impact
Stark et al. (2016)
•
Resolution of vertical stratification
(resolution <1 cm)
•
Correlation of measurements to soil type &
properties
•
Correlation of measurements to sediment
dynamics
Lucking et al. (subm.)
Portable Free Fall Penetrometers
Discussion – Opportunities & Challenges
Things that work well…
Work in progress…
•
Deployment (ease of handling, robust, etc.)
•
•
Data acquisition (reliability, accuracy)
Derivation of geotechnical parameters
with minimal knowledge/assumption of
soil conditions
•
Identification of point of impact
•
•
Improved understanding of high impact
velocity pore pressure response
Resolution of vertical stratification
(resolution <1 cm)
•
Calibration for different penetrometer
geometries
Correlation of measurements to soil type &
properties
•
Derivation of more detailed information
of in-situ conditions of mobile layer
Correlation of measurements to sediment
dynamics
•
Site investigations & increasing the
amount of available data
•
•
Portable Free Fall Penetrometers
Outlook – Large-scale Calibration Chamber
Portable Free Fall Penetrometers
Outlook – Add-on Sampling Unit
Bilici and Stark (subm.)
Pore Pressure Monitoring
RBR Solo/Duo pressure transducers:
• Battery and data storage for ~ 1 month of
continuous logging
• 6-12 Hz
Pore Pressure Monitoring
Raw Data – Water level fluctuations/ tidal cycles
Measurements from Yakutat, AK, in 2014
Cannon Beach, Medium Sand
• both sensors represent tidal curve
• p5 is more sensitive to irregularity
(waves)
• p20 is submerged earlier; the level remain
steady over ~ 30 minutes
• Swash turbulence is reflected in both
recordings but more in p5
• Exfiltration was observed simultaneously
at both sensors, leading to a rapid drop at
p20
Stark and Quinn (2015)
Pore Pressure Monitoring
Raw Data – Waves
Stark and Quinn (2015)
Pore Pressure Monitoring
Data Analysis – Pore Pressure Build-up
Pore pressure build up measured at a mixed sand-gravel beach in Nova Scotia in 2012
Pore Pressure Monitoring
Data Analysis – Risk for Residual Liquefaction
Assessment of the risk of residual liquefaction after Sumer (2014)
Stark (subm.)
Pore Pressure Monitoring
Data Analysis – Risk for Momentary Liquefaction (Vertical Pressure Gradient)
Assessment of the risk of momentary liquefaction after Yeh and Mason (2014)
Stark (subm.)
Pore Pressure Monitoring
Discussion
Pore Pressure Monitoring
•
Measurements are simple and reliable
•
Water level observations
•
Wave monitoring at different sediment depths
•
Pore pressure build-up can be found even with coarse sediments
•
Impact of irregular wave forcing and wave groups?
•
Interaction between pore pressure build up, vertical and horizontal pressure gradients?
•
Application and calibration of risk assessment models?
Conclusions & Take Home Messages
Coastal erosion and sediment transport processes represent a major
challenge for research and society.
Conclusions & Take Home Messages
Coastal erosion and sediment transport processes represent a major
challenge for research and society.
Geotechnical testing can contribute to the understanding of soil
behavior and properties under active sediment dynamics. This will
improve current methods to predict coastal erosion.
Conclusions & Take Home Messages
Coastal erosion and sediment transport processes represent a major
challenge for research and society.
Geotechnical testing can contribute to the understanding of soil
behavior and properties under active sediment dynamics. This will
improve current methods to predict coastal erosion.
Portable free fall penetrometers & embedment of pressure sensors
provide complementary information about sediment characteristics
and pore pressure response.
Thank you for your attention!
Questions?
This paper presents data and information from a number of different projects. Funding was provided for these projects by (in random order)
the National Sciences Foundation through grants NSF-IIA-142661 and NSF-OCE-1434938, the Offshore Energy Research Association of
Nova Scotia, the Natural Sciences and Engineering Research Council of Canada, the Atlantic Innovation Fund, the German Research
Association (via MARUM), the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (via the German
Federal Maritime and Hydrographic Agency), the German Academic Exchange Service, Virginia Tech and the Institute for Critical
Technology and Applied Science at Virginia Tech.
Numerous people contributed to the acquisition of the presented data. The following individuals played a crucial role in making the data
acquisition possible: Alex E. Hay (Dalhousie University, Halifax, Canada), Hugues Lantuit (Alfred-Wegener-Institute, Potsdam, Germany),
Achim Kopf, Christian Winter, Christian Zoellner, Hendrik Hanff, and Matthias Lange (all MARUM, Bremen, Germany), Maria LambersHuesmann (BSH, Hamburg, Germany), Arne Stahlmann (Franzius Institute, Hannover, Germany), Jose Borrero (eCoast, Raglan, New
Zealand), Shawn Harrison (University of Waikato, Hamilton, New Zealand), Tom Brandon and Lindy Cranwell (Virginia Tech), Rhonda
Coston (City and Borough of Yakutat, AK), Bill Staby (Resolute Marine Energy, Boston), Stephen Smyth (Blue C Design, Dartmouth,
Canada), and Doug Schillinger (RBR, Ottawa, Canada). Former or current students who have made a significant contribution to the
presented data are Boris Radosavljevic (Alfred-Wegener-Institute, Postdam, Germany), Matthew Hatcher (Dalhousie University, Halifax,
Canada), Ali Albatal, Cagdas Bilici, Freddie Falcone, Greg Lucking, Brandon Quinn and Jared Dorvinen (all current or former Virginia
Tech students).