1. 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)

2. EU LIMAS Liquefaction around marine structures n Overall objectives for further work with the new sampler for gassy soils n Realistic ambitions –limited time –limited funding n Scope of LIMAS –bring new interest into sampling of gassy soils –contribute to further development of techniques n Development in steps –start with simple, but useful sampling and measuring method –gradual elimination of limitations as refinement is added to the equipment

3. EU LIMAS Liquefaction around marine structures n Stepwise development of soil sampler involves limiting requirements n 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

4. EU LIMAS Liquefaction around marine structures n Stepwise development of soil sampler involves limiting requirements n 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

5. EU LIMAS Liquefaction around marine structures n Stepwise development of soil sampler involves limiting requirements n Proposed strategy for gas detection principles n 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

6. EU LIMAS Liquefaction around marine structures n Stepwise development of soil sampler involves limiting requirements n Proposed strategy for gas detection principles n 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 K w and skeleton compressibility K indicated

7. EU LIMAS Liquefaction around marine structures n Stepwise development of soil sampler involves limiting requirements n Proposed strategy for gas detection principles n 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

8. EU LIMAS Liquefaction around marine structures Workpackage 7 NTNU Trondheim Development of a soil sampler for gassy soils Progress report May - October 2001 n Literature review on related topics n Preliminary report provided n Contact with other partners on topics –UPPA, GeoDelft n Preparation for further work –sampler design –gas detection methods

9. EU LIMAS Liquefaction around marine structures Workpackage 7 NTNU Trondheim Development of a soil sampler for gassy soils Progress report October 2001 - March 2002 n Discussion meeting with GeoDelft and Fugro BV n 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 n evaluation of gas detection by saturation and backpressure techniques - literature study