Review of long seabed samplers and criteria for new sampler design

Abstract

Publication informationMarine Geology, 226 (1-2): 145-165Publisher Elsevier A cost efficient way of investigating shallow sediments and for collecting soils data for 2 many offshore geotechnical problems, e.g. anchoring of floating structures with suction 3 piles or evaluation of submarine slope stability, is to carry out seabed sampling to say 4 25 m below seabed and in addition perform seabed CPTUs to say 40 m. Based on a 5 review of data collated from the literature and from in house project experience at the 6 Norwegian Geotechnical Institute it was found that Kullenberg type piston core samples 7give poor recovery and samples, which are increasingly disturbed as penetration 8increase. This means that laboratory tests on these samples will give results that are not 9 representative of in situ conditions and will give incorrect parameters for foundation 10 design. Many different factors control the quality of the samples recovered but the need 11 for an effectively stationary piston a core retainer and improvements to the physical 12 sampler parameters, e.g. diameter / wall thickness ratio, cutting edge angle, inside and 13 outside friction are perhaps the most critical. The importance of each of these factors is 14 discussed in detail in addition to the need for instrumentation and the way to penetrate 15 the sampler. Recommendations are given in terms of criteria for the design of a new 16 sampler, which the authors feel will give better results than most samplers used in 17 practice today.

Performance of a novel sediment sampler as an add‐on unit for portable free‐fall penetrometers: Combining in situ geotechnical testing with sediment sampling

“…The results of these studies showed that the sharper carver can significantly overcome high strains on collected samples. The suggested value of the cutting‐edge angle for large‐scale deep gravity corers is 5° (Lunne and Long ). However, as the cutting edge of a small‐scale free‐fall sampling add‐on device should resist high impact velocities (up to 6 m s −1 ), the sharpest carver (C2) in this study equaled a 15° angle which performed well.…”

“…At the mouth of Ankau River, the use of a core catcher enabled the collection of sediment, but the recovery length was low (Fig. a; Lunne and Long , Bilici and Stark ). For the outer banks of the Lost River, the failure was mostly due to coarser sediment which could not be retained by suction.…”

Quality of Conventional Fixed Piston Samples of Norwegian Soft Clay

“…According to Lunne and Long (2006) the potential consequences of sample disturbance are summarised in Table 5. These are linked to two key design parameters, i.e.…”

A Simple Device for Subsectioning Aqueous Sediments from the Box or Spade Corer

“…Adopting these methods result in subsectioning= sampling error and sediment mixing. The subsectioning systems used for the gravity and piston core sediments also have been reviewed (Lunne and Long 2006), and possible errors due to sampling disturbance exerted by sample tube penetration, retrieval, sample extrusion, etc., have been discussed. For example, in piston extruder technique (Kemp et al 1971), precise extrusion of sediments for small increments is difficult due to diversity of fixtures, whereas in another (Glew 1988), the apparatus is large, bulky, heavy, and complicated as the method involves movement of components by locking and unlocking of many parts.…”