Environmental Engineering Reference
In-Depth Information
Swedish Foil Sampler
High-quality continuous samples in soft, sensitive cohesive soils, useful in locating the
shear zone in a slope failure problem, are possible with the Swedish foil sampler. A sam-
pling tube, usually 8 ft in length, is pushed into the soil by a special drill rig as a reaction.
To eliminate friction between the sample and the tube walls, thin steel strips, or foils,
unroll to follow along the sampler walls as the sampler penetrates the soil.
2.4.4
Subaqueous Sampling
Categories
Sample procurement under subaqueous conditions can be placed in one of four general
categories on the basis of the sampling technique:
1.
Normal cased-boring methods.
2.
Wireline drilling techniques.
3.
Sampling to shallow depths below the bottom without drill rigs and casing.
4.
Sample recovery from deep borings in offshore sands. Borehole remote-sensing
and logging methods (Section 2.3.6) , such as the electric well logger and nuclear
probes, should be considered since they provide important supplemental data.
Normal Cased-Boring Methods
General
Normal cased borings require a stable platform for mounting the boring equipment and
procurement of samples. The up and down movements from swells severely affect drilling
and sampling operations as bits and samplers are removed from contact with the hole bot-
tom. Tidal effects require careful considerations in depth measurements.
Platforms
Floats ( Figure 2.69) or barges ( Figure 2.70) are used in shallow water, generally less than 50
ft (15 m) deep, with slight swells. Penetration depths are in moderate ranges, depending
on drill rig capacity.
Large barges or jack-up platforms are used in water to depths of the order of 100 ft (30 m)
with slight to moderate swells. Penetration depths below the bottom are moderate
depending upon the drilling equipment.
Drill ships with wireline drilling techniques are used in deep water (Section 2.3.4 and
Figure 2.42) .
Wireline Drilling Methods
General
Wireline drilling techniques are used in deep water. Much deeper penetration depths are
possible than are with normal cased borings, and operations can tolerate much more
severe sea conditions than can cased borings.
Platforms
Large barges or moderately large ships are used in relatively calm water and water depths
over 50 ft (15 m), where deep penetration of the seafloor is required. Jack-up platforms are
used where heavy swells can occur. Large drill ships (Figure 2.42) are used in deep water
where deep penetration below the seafloor is required.
 
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