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EU LIMAS Grenoble, France April 2003

EU LIMAS Grenoble, France April 2003. Workpackage 7, NTNU Trondheim Development of a soil sampler for measurement of gas content in soils. Status of in-house testing of prototype sampler By associate professor Rolf Sandven (NTNU). EU LIMAS Liquefaction around marine structures.

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EU LIMAS Grenoble, France April 2003

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  1. EU LIMASGrenoble, France April 2003 Workpackage 7, NTNU Trondheim Development of a soil sampler for measurement of gas content in soils. Status of in-house testing of prototype sampler By associate professor Rolf Sandven (NTNU)

  2. EU LIMASLiquefaction around marine structures WP7 Development of soil sampler for measurement of gas content in soils Contents • Introduction - design principles • In-house testing of sampler prototype • test facilities • test programme and sampler configurations • test results and observations • Conclusions - further development and activities

  3. EU LIMASLiquefaction around marine structures WP7 Development of soil sampler for measurement of gas content in soils Design principles of new soil sampler

  4. Criteria for NTNU soil sampler - conceptual Primarily applicable in clean sands and silts Primarily applicable for depth range between 0 - 2 m under the seabed level Simple system for sealing and pressure control of the sample container Realistic and reasonably accurate representation of the gas/air volume in the sampled soil Criteria for NTNU soil sampler - practical The sampling equipment should be portable and possible to operate in the field The equipment should enable repeated sampling operations at the test site Limited maintenance required after sampling operations are completed Re-use of sealing units in subsequent sampling series EU LIMAS WP7Liquefaction around marine structures

  5. Scope of work Evaluate methods for detection of gas content in obtained samples Select and develop working principles and guidelines for the new sampler and necessary infrastructure through laboratory and field studies Stepwise development of sampler with testing and verification of important features in in-house studies Laboratory and field studies in other LIMAS WPs Objectives for sampling with the NTNU soil sampler Maintain natural level of saturation and gas content of soil sample during and after sampling The gas content in obtained samples should be assessed through direct or indirect measurements The mechanical disturbance of soil sample should be tolerable during the sampling process Need for maintenance and practical preparation works during field mission should be small EU LIMAS WP7Liquefaction around marine structures

  6. EU LIMAS WP7Liquefaction around marine structures Pressure in Drainage • Sampler concept: • 65 mm diameter piston sampler with inner sample container and outer steel cylinder • Sealing of sample container by lower ball valve and upper piston to prevent leakage of gas/air • Possibility for bringing the sample container under pressure after sampling by means of a back-pressure system through the piston • Measurement of water volume needed to saturate the obtained sample Water in Top piston with channels Sample container Ball-valve Tip extension

  7. EU LIMASLiquefaction around marine structures WP 7 Development of soil sampler for measurement of gas content in soils In-house test programme Scope of work and test facilities

  8. Scope of work Test the prototype version of the NTNU sampler in realistic in-house conditions with respect to important technical features Sampler design and overall performance Ball valve function closure system clogging wear Pressure system Evaluation of in situ test procedures and infrastructure Alternative sampler designs EU LIMAS WP7In-house test programme for NTNU sampler

  9. EU LIMAS WP7In-house test facilities Overflow Water inlet Sand box 120x100x100 cm Water outlet Glass wall

  10. EU LIMAS WP7In-house test facilities Cushion Wire Cranetackle Sampler Tackles

  11. EU LIMAS WP7In-house test facilities Mørtelverket Hokksund

  12. EU LIMASLiquefaction around marine structures WP 7 Development of soil sampler for measurement of gas content in soils Sampler configurations and test variables

  13. Sampler configurations included in test programme Prototype f65 mm sampler with ball valve, no piston Prototype f65 mm sampler with ball valve, with coned/flat piston f54 mm open sample tube, standardised geometry f72 mm open sample tube, standardised geometry f95 mm open sample tube, standardised geometry f95 mm open sample tube, sampler geometry EU LIMAS WP7In-house test programme

  14. Evaluation of test variables on sampling efficiency Inner and outer diameter of sample tube Use of piston in sampler prototype Detailed geometry of sampler tip inner and outer clearance sharpness of edge, taper angle Penetration rate during shearing of the sample Use of vibration during shearing of the sample Type of sand in test bin State of test sand (density) EU LIMAS WP7In-house test programme

  15. EU LIMAS WP7First prototype of NTNU sampler Top plate Cylinder extension Sample container Ball valve housing Piston Assembled NTNU prototype f65 mm sampler

  16. EU LIMAS WP7First prototype of NTNU sampler Cogwheel push rod Ball valve Mounted ball valve compartment

  17. EU LIMAS WP7First prototype of NTNU sampler Ball valve Cogwheel push rod Cogwheel Open valve Closing valve Ball valve sealing system

  18. EU LIMAS WP7Open tube test samplers f95 mm f72 mm f54 mm

  19. EU LIMAS WP7Open tube test samplers f65 mm prototype sampler without piston f95 mm open tube sampler with sampler geometry f95 mm with sampler geometry

  20. EU LIMAS WP7First prototype sampler with piston Sampler tip with piston Close-up of piston Ventilation rod

  21. EU LIMAS WP7Prototype soil sampler with piston Piston tip Arrest of piston rod during shearing Positioning of sampler before sampling

  22. EU LIMASLiquefaction around marine structures WP7 Development of soil sampler for measurement of gas content in soils Test results and observations

  23. Sampler concept is feasible but needs improvement Plugging of open cylinders is a major problem and may lead to poor sampling efficiency in small-diameter samplers Plugging risk is reduced when sampler diameter exceeds 100 mm, but this causes impractical sampler designs Use of piston improves sampling efficiency and is mandatory when small-diameter sample design is chosen The ball valve surface and gadgets needs to be of high wear-resistance material (hardened corroless steel) Mechanical cogwheel system for activation of ball valve works well and is easily operated The sampler tip geometry should be considered with respect to plugging risk wall thickness to diameter (t/d) ratio should be reduced as much as possible (tip extension) exchangeable sampler tips necessary EU LIMAS WP7Test results from in-house study Observations of sampler performance

  24. EU LIMAS WP7Summary of test results - all sampler configurations

  25. EU LIMAS WP7Plugging of sampler during sampling slight compaction plugging

  26. EU LIMAS WP7Test results from in-house study

  27. EU LIMAS WP7Test results from in-house study

  28. EU LIMAS WP7Test results from in-house study

  29. EU LIMAS WP7Test results from in-house study

  30. EU LIMAS WP7Test results from in-house study

  31. EU LIMAS WP7Liquefaction around marine structures Development of soil sampler for measurement of gas content in soils Detection of gas content

  32. EU LIMAS WP7 Liquefaction around marine structures Gas detection Suggested method • Transportable pressure system for application of back-pressure in situ • application of back-pressure to sealed sample container through top piston (max. ~ 600 kPa) • measurement of resulting stabilised absorption of de-aired water in sample container during back-pressure application • Precision measurement of absorbed water volume on scaled burette. • Determination of sampled soil volume and available pore volume in subsequent laboratory tests at the site Drainage Flushing

  33. EU LIMAS WP7Pressurisation of sample container Water inlet Top filling of de-aired water

  34. EU LIMAS WP7Pressurisation system for sample container Manometer Pressure supply from nitrogene flask Sampler Pressure regulator

  35. EU LIMAS WP7Pressurisation system for sample container Manometer Pressure regulator Top plate with pressure and water inlets

  36. EU LIMAS WP7Sealing of sample container by the ball valve Assembled sampler pressure tested up to 800 kPa before sampling ): mechanical design of sampler and ball valve compartment successful Wear and abrasion of PVC ball valve and gadgets during closure

  37. EU LIMASLiquefaction around marine structures WP7 Development of soil sampler for measurement of gas content in soils Further development and activities

  38. Sampler concept ~ f65 mm sampler diameter maintained Length of sample container preferrably 3-4 times the sample diameter (open cylinders) Use of sealed piston for improved sampling control Use of wear-resistant hardened material in ball valve/gadgets reduce risk of clogging, wear and leakage may be substituted Cogwheel system succesful, adopted for activation of ball valve Minor technical improvement on sampler components necessary Pressure control Piston will serve as the sealed top cap of sample container channels from pressure and water inlets established through piston ventilation valve controlled by extension rod Back-pressure system is proven and provides the preferred gas/air detection method for field use will be further tested and validated in next round of in-house test EU LIMAS WP7 Design principles of final version of sampler

  39. Workpackage 7 NTNU Trondheim Development of a soil sampler for gassy soils Summary Status of work and further activities I April 2003 First version of soil sampler tested in laboratory facilities at NTNU (November 02 - April 03). Completion of in-house study on: evaluation of sampler design and performance in realistic test conditions study of effects of various equipment configurations and test procedures during sampling Further development and manufacture of final version of sampler has started at NTNU workshop improved design of final sampler and necessary test infrastructure in-house manufacturing and testing in NTNU workshop/labs EU LIMASLiquefaction around marine structures

  40. Workpackage 7 NTNU Trondheim Development of a soil sampler for gassy soils Summary Status of work and further activities II April 2003 Planning of field tests in WP 4 during fall 2003 Practical arrangement of field tests Develop test procedures for field and laboratory tests Planning of alternative laboratory tests on LWI sand in WP3 Alternative simulation of test conditions for LWI large scale experiments In-house laboratory tests on LWI sand shipped to Trondheim Possible sample operations in new large scale tests in Hanover flume (ref. S. Massel, Institute of Oceanology, PAS)? EU LIMASLiquefaction around marine structures

  41. Some general observations from an equipment manufacturer Design of test equipment is not a linear process one step forward may sometimes imply two steps back new and bright ideas need time to mature, develop and materialise the soil-sampler interaction is difficult to handle soil disturbance disturbance of gas/water content influence on design things take (more) time! EU LIMAS WP7 The road ahead.…..?

  42. EU LIMASLiquefaction around marine structures Development of soil sampler for measurement of gas content in soils Supplementary pictures

  43. EU LIMAS WP7Principles of piston sampling and ball valve system Manometer Pressure regulator Top plate with pressure and water inlets Uplift Pushing Shearing Piston sampling Ball valve system

  44. EU LIMAS WP7Principles of ball valve assisted sampling Manometer Pressure regulator Top plate with pressure and water inlets

  45. EU LIMAS WP7Definitions of sampler geometry

  46. EU LIMAS WP7Influence of sampler geometry

  47. EU LIMAS WP7Influence of sampler geometry

  48. Effect of gas on soil characteristics Sample disturbance due to gas exsolution and expansion Increases susceptibility for momentary liquefaction Influence on soil parameters shear modulus bulk modulus strength and pore pressure parameters consolidation parameters Influence on geophysical properties wave velocity magnetism EU LIMASLiquefaction around marine structures

  49. EU LIMASLiquefaction around marine structures Soil - water gas systems (Hrydech et al (1987)) Sr = 5-9 % Sr = 9 - 70 % Sr > 70 %

  50. Detection of gas in soil samples Computer tomography (CT) imaging Scanning Electron Microscope (SEM) techniques Uni- or multisensor scanning devices sonic wave velocity gamma-ray detection magnetism Volumetric measurement during water absorption EU LIMASLiquefaction around marine structures

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