Offshore Soil Sampling

The self-contained tools are typically capable of exploring soil conditions to approximately 12.8 m. Deeper investigations will require an operation through the drill string. 

---

Allen, R.L., Yen, B.C., and McNeill, R.L. 1978. Stereoscopic X-ray assessment of offshore soil samples. Proceedings of the 10th Annual Offshore Technology Conference. Paper No. 3212. Houston, TX. 

From these data, it appears that in areas where PAH concentrations are high, such as the northeastern United States, one can associate the PAH mixtures found with both anthropogenic activity and combustion. There is a possibility that natural combustion, such as forest fires, could contribute to the more remote areas (Maine soil, for example). The contribution of PAH to the offshore sediments (Samples 3, 4, 9) by forest fires should be minimal compared with the anthropogenic contribution because of the proximity of these sites to urban areas and their distance from large forested areas. 

A self-contained sampling tool such as a gravity (or drop) core sampler, a box core, or a vibratory corer is the most inexpensive method to obtain soil samples offshore. These tools can generally be operated from small supply vessels (less than 51.2 m) tirat have a crane or a... 

Semple, R.M., and Johnston, J. W. 1979. Performance of "Stingray" in soil sampling and in situ testing. Proceedings of the International Conference on Offshore Site Investigation. London. 

Based on a full suite of sample types including soil, stream sediment, surface water, groundwater and offshore marine and estuarine sediment in the coastal zone. 

The ocean has received far less attention than wetlands and soils as a source and sink of CH4. Studies of CH4 distributions in the Eastern Tropical North Pacific showed two CH4 maxima (Rurke et al., 1983) a surface maximum presumably associated with methanogensesis in fecal fellets (Karl and Tilbrook, 1994) and a deeper maximum. The mass spectrometric GC/C/IRMS technique discussed earlier allows measurement of fi CEU in small samples of seawater (Holmes et al., 2000). This technique was applied in the Eastern Tropical North Pacific (Sansone et al., 2001) to study methanogenesis and methane oxidation. The Sansone et al. (2001) results show a distinct difference in the fi CEU from the two CH4 maxima, leading to the suggestion that the deeper maximum may result from long distance offshore transport of CH4 with a shelf or seep source similar to that shown in Cynar and Yayanos (1993, figure 3). 

Several investigators have quantified the effects offshore wireline percussion sampling has on shear strength and other soil properties. For example, Emrich (1971) compared shear... 

Noorany, 1.1985. Offshore sampling and in-situ testing 1981 update. In Updating Subsurface Sampling of Soils and Rocks and Their In-Situ Testing, Saxena, S.K., ed., Engineering Foundation, New York. 

Yoimg, A.G., Quiros, G.W., and Ehlers, C.J. 1983. Effects of offshore sampling and testing on undrained soil shear strength. Proceedings of the 15th Annual Offshore Technology Conference. Paper No. 4465, Houston, TX. 

The CPT is an acceptable test under every methodology for liquefaction assessment. The CPT is a necessary test for any of the advanced methods of liquefaction assessment, particularly when moving into 2D cases of soil structure interaction or if looking to offshore situations. The CPT will even be necessary if taking undisturbed samples for cyclic simple shear testing, both as a means to extrapolate the test data obtained across the area of the site (only a few of these laboratory tests will normally be carried out) as well as provide data to estimate the sample disturbance from in situ to as-tested conditions. For a description of the CPT, see Appendix B-2.3.2. 

---