EU LIMAS Liquefaction around marine structuresWorkpackage 7, NTNU Trondheim
Development of soil sampler for measurement of gas content in soils
Progress of work
By associate professors
Rolf Sandven (NTNU) and Mike Long (UCD)
EU LIMAS Liquefaction around marine structures
Workpackage 7, NTNU Trondheim
Development of soil sampler for measurement of gas content in soils
Progress of work
By associate professors
Rolf Sandven (NTNU) and Mike Long (UCD)
EU LIMAS Liquefaction around marine structures
Overall objectives for further work with the new sampler for gassy soils Realistic ambitions
limited time
limited funding
Scope of LIMAS
bring new interest into sampling of gassy soils
contribute to further development of techniques
Development in steps
start with simple, but useful sampling and measuring method
gradual elimination of limitations as refinement is added to the equipment
EU LIMAS Liquefaction around marine structures
Stepwise development of soil sampler involves limiting requirements Some sample disturbance is accepted
shear deformations or compression is not believed to influence gas bubble size or distribution
the sample equipment will have large area ratio due to accomodation of a ball-valve
simple design precautions will be made to reduce impact
extension ahead of ball-valve
small taper angle
EU LIMAS Liquefaction around marine structures
Stepwise development of soil sampler involves limiting requirements Sample equipment will be designed for shallow sampling
sampling ambitions in the tidal zone
0 - 5m soil depth
0 - 2 m water depth
must be rigid enough for application of back-pressure in sample container
maintenance of sample conditions
sealed sample cylinder during handling outside measuring cell without leakage of gas/water
re-established ambient pressure conditions in the lab. measuring cell
EU LIMAS Liquefaction around marine structures
Stepwise development of soil sampler involves limiting requirements Proposed strategy for gas detection principles
Field tests:
Use of back-pressure saturation techniques on sample cylinder containing retrieved soil sample
Measurement of compressed gas volume, represented by de-aired water on scaled burette
Use of additional field tests
BAT - probe for water/gas sampling
In situ geophysical tests
seismic CPTU
cross-hole methods
logging methods
EU LIMAS Liquefaction around marine structures
Stepwise development of soil sampler involves limiting requirements Proposed strategy for gas detection principles
Laboratory tests on selected samples:
Recovered soil material is reconstituted in laboratory conditions
Triaxial test approach applicable
ambient pressure and saturation conditions are re-established in lab. sample
Use of B-tests for determination of bulk water moduli
Ratio between pore fluid stiffness Kw and skeleton compressibility K indicated
EU LIMAS Liquefaction around marine structures
Stepwise development of soil sampler involves limiting requirements Proposed strategy for gas detection principles
Other scanning and screening techniques for supplementary investigations
use of X-ray scan technique
Magnetic Resonance MRI
CT scanning methods
SEM imaging
Use of multi-purpose core logger
wave velocity
density
magnetism
EU LIMAS Liquefaction around marine structures
Workpackage 7
NTNU Trondheim
Development of a soil
sampler for gassy soils
Progress report
May - October 2001 Literature review on related topics
Preliminary report provided
Contact with other partners on topics
UPPA, GeoDelft
Preparation for further work
sampler design
gas detection methods
EU LIMAS Liquefaction around marine structures
Workpackage 7
NTNU Trondheim
Development of a soil
sampler for gassy soils
Progress report
October 2001 - March 2002 Discussion meeting with GeoDelft and Fugro BV
Started manufacturing of introductory version of soil sampler:
simplified design
evaluate type of ball-valve
sealing potential
wear and maintenance
sampler version can easily be further developed to accommodate pressure valves and water inlet
basis for prototype sampler
evaluation of gas detection by saturation and backpressure techniques - literature study
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