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SEABED (GRAB) SOIL SAMPLING
SEABED SAMPLING (SEDIMENT GRAB SAMPLING) WAS TAKEN USING A VAN DER VEEN TYPE GRAB SAMPLER AT SELECTED LOCATIONS THROUGHOUT THE SURVEY AREA.
EACH SAMPLE COLLECTED SHALL BE OF A MINIMUM MASS OF ONE KILOGRAM, STORED IN A CLEAR PLASTIC BAG AND PLACED IN ANOTHER BAG BEFORE BEING TIED AND LABELED. A TOTAL OF SAMPLES COLLECTED WAS SENT TO A LABORATORY FOR THE FOLLOWING PARAMETERS : -
PARTICLE SIZE DISTRIBUTION (WET SIEVING METHOD INCLUDING HYDROMETER TEST WHERE REQUIRED) IN ACCORDANCE WITH BS1377: PART 2: 1990 STANDARD TEST METHOD FOR PARTICLE SIZE ANALYSIS OF SOILS.
VAN VEEN GRAB
Platform: Any type of sport fishing boat suitable for sampling works.
Positioning System: VS330 Atlas H-50 with QINSy 8.1 or Hypack 2018 navigation software.
Material: Stainless steel with lead blocks.
Equipment: Van Veen Grab.
Processing Method: Laboratory test.
Test Result: Particle Size Distribution (PSD) for Soil type, grain size, distribution percentage.
HOW A VAN VEEN-TYPE GRAB SAMPLER WORKS:
lowered until it strikes bottom
a release mechanism then closes "cups"
heavy enough to stay closed when raised
covers prevent sediment from washing out as raised to surface
EXAMPLE SEABED SAMPLING POINT
THE GRAB SAMPLER CONSISTS OF TWO OPPOSING SEMI-CIRCULAR JAWS THAT ARE NORMALLY HELD OPEN BY A TRIGGER MECHANISM. THE SAMPLER IS LOWERED TO THE BOTTOM WHERE CONTACT WITH THE BOTTOM SETS OFF THE TRIGGER AND A STRONG SPRING SNAPS THE JAWS SHUT TRAPPING A SAMPLE OF THE BOTTOM INSIDE. FINE COPPER SCREEN COVERS THE TOP OF THE JAWS SO THAT THE TRAPPED MATERIAL WILL NOT WASH OUT AS THE SAMPLER IS RETRIEVED.
LABORATORY TEST REPORT
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