ASTM D4823-95(2014)
(Guide)Standard Guide for Core Sampling Submerged, Unconsolidated Sediments
Standard Guide for Core Sampling Submerged, Unconsolidated Sediments
ABSTRACT
This guide covers core-sampling submerged, unconsolidated sediments. It also covers terminology, advantages and disadvantages of different types of core samplers, core-distortions that may occur during sampling, techniques for detecting and minimizing core distortions, and methods for dissecting and preserving sediment cores. Sampling procedures and equipment are divided into categories based on water depth. Critical dimensions and properties of open-barrel and piston samplers like the cutting-bit angle, core-liner diameter, inside friction factor, outside friction factor, area factor, core-barrel length, barrel surfaces, and chemical composition of sampler parts shall conform to this standard guide. The following factors shall be considered for decisions in choosing between an open-barrel sampler and a piston sampler: depth of penetration, core compaction, flow-in distortion, surface disturbance, and repenetration. Driving techniques included in this guide are free core samplers, implosive and explosive samplers, punch-corer samplers, vibratory-driven samplers and impact-driven samplers. Guides are also included for collecting short cores in shallow water, collecting long cores in shallow water, and collecting short and long cores for a range of water depth. Field record shall be provided for every sampling operation. Guides are also provided for core extrusion for samplers with no liners, slitting core and core liners, sectioning cores, sampling through liner walls, preserving cores, and displaying cores.
SCOPE
1.1 This guide covers core-sampling terminology, advantages and disadvantages of different types of core samplers, core-distortions that may occur during sampling, techniques for detecting and minimizing core distortions, and methods for dissecting and preserving sediment cores.
1.2 In this guide, sampling procedures and equipment are divided into the following categories based on water depth: sampling in depths shallower than 0.5 m, sampling in depths between 0.5 m and 10 m, and sampling in depths exceeding 10 m. Each category is divided into two sections: equipment for collecting short cores and equipment for collecting long cores.
1.3 This guide emphasizes general principles. Only in a few instances are step-by-step instructions given. Because core sampling is a field-based operation, methods and equipment must usually be modified to suit local conditions. This modification process requires two essential ingredients: operator skill and judgment. Neither can be replaced by written rules.
1.4 Drawings of samplers are included to show sizes and proportions. These samplers are offered primarily as examples (or generic representations) of equipment that can be purchased commercially or built from plans in technical journals.
1.5 This guide is a brief summary of published scientific articles and engineering reports. These references are listed in this guide. These documents provide operational details that are not given in this guide but are nevertheless essential to the successful planning and completion of core sampling projects.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see 6.3 and 11.5.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D4823 − 95 (Reapproved 2014)
Standard Guide for
Core Sampling Submerged, Unconsolidated Sediments
This standard is issued under the fixed designation D4823; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.8 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This guide covers core-sampling terminology, advan-
ization established in the Decision on Principles for the
tages and disadvantages of different types of core samplers,
Development of International Standards, Guides and Recom-
core-distortions that may occur during sampling, techniques
mendations issued by the World Trade Organization Technical
for detecting and minimizing core distortions, and methods for
Barriers to Trade (TBT) Committee.
dissecting and preserving sediment cores.
1.2 In this guide, sampling procedures and equipment are
2. Referenced Documents
divided into the following categories based on water depth:
2.1 ASTM Standards:
sampling in depths shallower than 0.5 m, sampling in depths
D420GuidetoSiteCharacterizationforEngineeringDesign
between0.5mand10m,andsamplingindepthsexceeding10
and Construction Purposes (Withdrawn 2011)
m. Each category is divided into two sections: equipment for
D1129Terminology Relating to Water
collecting short cores and equipment for collecting long cores.
D1452Practice for Soil Exploration and Sampling byAuger
1.3 Thisguideemphasizesgeneralprinciples.Onlyinafew
Borings
instances are step-by-step instructions given. Because core
D1586TestMethodforStandardPenetrationTest(SPT)and
sampling is a field-based operation, methods and equipment
Split-Barrel Sampling of Soils
must usually be modified to suit local conditions. This modi-
D1587Practice for Thin-Walled Tube Sampling of Fine-
fication process requires two essential ingredients: operator
Grained Soils for Geotechnical Purposes
skill and judgment. Neither can be replaced by written rules.
D4220 Practices for Preserving and Transporting Soil
1.4 Drawings of samplers are included to show sizes and Samples
proportions. These samplers are offered primarily as examples D4410Terminology for Fluvial Sediment
(orgenericrepresentations)ofequipmentthatcanbepurchased
commercially or built from plans in technical journals.
3. Terminology
1.5 This guide is a brief summary of published scientific
3.1 Definitions—For definitions of terms used in this guide,
articles and engineering reports. These references are listed in
refer to Terminology D1129 and Terminology D4410.
this guide. These documents provide operational details that
3.2 Definitions of Terms Specific to This Standard:
are not given in this guide but are nevertheless essential to the
3.2.1 check valve—a device (see Fig. 1) mounted atop an
successful planning and completion of core sampling projects.
open-barrel core sampler.As the sampler moves down through
1.6 The values stated in SI units are to be regarded as
water and sediment, the valve remains open to allow water to
standard. No other units of measurement are included in this
flow up through the barrel. When downward motion stops, the
standard.
valve closes. During retrieval, the valve remains closed and
creates suction that holds the core inside the barrel.
1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.2.2 core—a vertical column of sediment cut from a parent
responsibility of the user of this standard to establish appro-
deposit.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
For specific warning statements, see 6.3 and 11.5.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This guide is under the jurisdiction ofASTM Committee D19 on Water and is Standards volume information, refer to the standard’s Document Summary page on
the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology, the ASTM website.
and Open-Channel Flow. The last approved version of this historical standard is referenced on
Current edition approved Jan. 1, 2014. Published March 2014. Originally www.astm.org.
approved in 1988. Last previous edition approved in 2008 as D4823–95 (2008). Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
DOI: 10.1520/D4823-95R14. this guide.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4823 − 95 (2014)
NOTE 1—(a) Strips of metal foil slide up through the core barrel as the
cutting edge advances downward. (4) (b) The plastic sleeve unfolds from
pleats stored near the cutting edge. This sleeve surrounds the core as the
barrel moves down. (3)
NOTE 1—Dark bands represent stiff sediments; light bands represent
FIG. 3 Core Conveyors
plastic sediments. As coring proceeds, sediment below the barrel moves
laterallyawayfromthecuttingedgeandplasticsedimentsinsidethebarrel
are compressed. “A” is the core’s length and “B” is the barrel’s
penetration depth.
3.2.7 extrude—Theactofpushingacorefromacorebarrel
FIG. 1 Deformations Caused by Open-Barrel Core Samplers (1)
or a core-barrel liner.
3.2.8 open-barrel sampler—in simplest form, a straight
3.2.3 core catcher—a device (see Fig. 2) that grips and
tube open at both ends. More elaborate open-barrel samplers
supports the core while the sampler is being pulled from the
have core catchers and check valves.
sediment and hoisted to the water surface.
3.2.9 piston immobilizer—a special coupling (see Fig. 4)
3.2.4 core conveyor—a device (see Fig. 3) for reducing
that protects a core from disruptive forces that arise during
friction between a core and the inside surface of a core barrel.
sampler pull-out. Piston immobilizers are also called split
3.2.5 core-barrel liner—a rigid, thin-wall tube mounted
pistons or break-away pistons.
inside the barrel of a core sampler. During the core-cutting
3.2.10 piston sampler—a core sampler (see Fig. 5) with a
process, sediment moves up inside the liner.
solid cylinder (piston) that seals against the inside walls of the
3.2.6 core sampler—an instrument for collecting cores.
core barrel. The piston remains fixed at the bed-surface
elevationwhilethecorebarrelcutsdownthroughthesediment.
NOTE 1—(a) The leaves separate during penetration and then close
during retrieval. Strips of gauze can be woven around the leaves to
provideadditionalsupport. (2)(b)Thelevertripsdownduringretrievalto NOTE 1—During penetration the shear pins break but the flow-
releasethespringandtwistthefabricsleeveshut. (3)(c)Thecuppedplate restricting orifice holds the clevis and piston together. During retrieval,
drops during retrieval to block the entrance and support the core. (3) (d) water in the top chamber flows through the orifice and allows the piston
Theleverreleasesthespring-loadedbladewhichpivotsdownwardtohold and clevis to separate. Cable tension pulls the clevis up against the stop
the core. (3) but friction locks the piston and core barrel together.
FIG. 2 Core Catchers FIG. 4 Piston Immobilizer (5)
D4823 − 95 (2014)
3.2.15 undisturbed sample—sediment particles that have
notbeenrearrangedrelativetooneanotherbytheprocessused
to cut and isolate the particles from their parent deposit. All
core samples are disturbed to some degree because raising the
cores to the water surface causes pore water and trapped gases
to expand (10). In common usage, the term “undisturbed
sample” describes particles that have been rearranged but only
to a slight degree.
4. Critical Dimensions of Open-Barrel and Piston
Samplers
4.1 Dimensions of a sampler’s cutting bit, core tube, and
core-tubeliner(seeFig.7)arecriticalinapplicationsrequiring
undisturbed samples. These dimensions control the amount of
distortion in recovered cores. The recommendations in this
section were developed from tests on open-barrel core sam-
plers (11);however,therecommendationsareusuallyextended
NOTE 1—(a) The sampler is lowered slowly through the water. (b) The
sampler falls free when the trip weight contacts the bed. (c) The core
to cover piston-type core samplers.
barrel cuts downward but the piston remains stationary.
4.2 Cutting-Bit Angle—Theangle“b”onthecuttingbit(see
FIG. 5 Operation of a Piston-Type Core Sampler (6)
Fig. 7) should be less than about 10°; the optimum angle is
about 5°. If the angle is smaller than about 2°, the bit cuts
3.2.11 recovery ratio—the ratioA/B where “A” (see Fig. 1)
efficiently but its edge chips and dulls easily.
is the distance from the top of the sediment core to the bottom
4.3 Core-Liner Diameter, D (see Fig. 7)—D should be
s s
ofthecuttingbitand“B”isthedistancefromthesurfaceofthe
larger than about 5 cm; however, the upper limit for D is
s
parent deposit to the bottom of the cutting bit.
difficult to establish. As D increases, the amount of core
s
3.2.12 repenetration—a mishap that occurs when a core
compaction decreases but the sampler becomes heavier and
sampler collects two or more cores during one pass.
larger. A survey of existing samplers shows that 10 cm is a
practical upper limit. A few samplers have barrels larger than
3.2.13 surface sampler—a device for collecting sediment
from the surface of a submerged deposit. Surface samplers are 10 cm but these are used only for special applications (12).
sometimes referred to as grab samplers.
4.4 Inside Friction Factor—The dimensions D and D (see
s e
3.2.14 trip release—a mechanism (see Fig. 5 and Fig. 6(b)) Fig. 7) set the inside friction factor defined as C =(D −
i s
that releases a core sampler from its suspension cable and D )100/D . For a barrel without a core conveyor, the optimum
e e
allows the sampler to freely fall a predetermined distance C value depends mainly on the barrel’s length. C should be
i i
before striking the bed. smaller than 0.5 if the barrel is shorter than about 2 m. If the
barrelislongerthanabout2m, C shouldfallbetween0.75and
i
1.5. For a barrel with a core conveyor, C should be smaller
i
than 0.5 regardless of the barrel’s length. Notice that in all
instances D is lightly greater than D . The small expansion
s e
above the cutting bit minimizes friction where the outside of
NOTE 1—(a) The messenger weight strikes the hook and releases the
stringholdingthecheckvalve. (7)(b)Thetripweightstrikesthesediment
and unhooks the sampler. (8) (c) The cable slackens and allows the
spring-loaded hook to open. (9)
FIG. 6 Release Mechanism FIG. 7 Critical Dimensions for Cutting Bits and Core Barrels (11)
D4823 − 95 (2014)
the core contacts the inside of the barrel or liner. Friction 10, and 20 apply to slow-penetrating, open-barrel samplers.
distorts the core’s strata by bending horizontal layers into Studies suggest that all of these factors can be increased by
curved, bowl-shaped surfaces shown on the upper part of Fig. raising the sampler’s penetration speed or using a piston
8. Friction also causes overall end-to-end compaction of the sampler instead of an open-barrel sampler.
core and thereby reduces recovery ratios. If friction becomes
4.8 Barrel Surfaces—All surfaces contacting the core
very large, sediment fails to enter the cutting bit. Instead,
should be smooth and free of protruding edges to reduce
sediment moves aside as the bit penetrates downward. This
internal friction and minimize core distortion. The surfaces
lateral motion, commonly referred to as “staking,” prevents
should also be clean and chemically inert if the core is to be
deep-lying strata from being sampled. It is important to
analyzed for contaminants or if the core is to be stored in its
observe upper limits on C because too large an expansion
i
liner for long periods of time.
causes another form of distortion, the core slumps against the
4.9 ChemicalCompositionofSamplerParts—Samplerparts
walls as the sediment slides up into the barrel.
must not contain substances that interfere with chemical
4.5 Outside Friction Factor—The dimensions D and D
w t
analysis of the cores. For example, barrels, pistons, and core
(see Fig. 7) set the outside friction factor defined as C =(D
o w
catchers made of plastic should not be used if tests include
− D)100/D. C shouldbezeroforbarrelsusedincohesionless
t t o
phthalate concentrations. Misleading data will result from
sediments; but C should be between 1.0 and about 3.0 for
o
plasticizer contamination of the sediments.
barrels used in cohesive sediments. Notice that in all instances
D is larger than D. The small contraction above the bit
5. Open-Barrel Samplers Versus Piston Samplers
w t
reduces friction at the outside surface of the barrel and makes
5.1 Users sometimes face difficult decisions in choosing
it easier to push the core barrel into the bed. On a long barrel,
between an open-barrel sampler and a piston sampler. The
friction can be reduced by installing one or more sleeves (see
decision frequently depends not only upon characteristics of
Fig. 7). The sleeves not only plough a path for the barrel but
the two samplers but also upon other factors such as hoisting-
they also serve as clamps to hold barrel sections together.
equipment capabilities, working platform stability, water
4.6 Area Factor—The dimensions D and D set the area
depth, operator experience, and the purpose for collecting the
w e
2 2
factor defined as C =(D ) 100/D . C should be less than
cores.Thissectioncoversfactorstoconsiderbeforemakingthe
a w e a
10 or possibly 15. Notice that C is proportional to the area of
final choice.
a
sediment displaced by the bit divided by the area of the bit’s
5.2 Depth of Penetration—Most open-barrel samplers and
entrance; therefore, C is an index of disturbance at the cutting
a
most piston samplers rely on momentum to drive their barrels
edge. A sampler with too large an area factor tends to
into sediment deposits. Momentum-driven samplers are re-
oversample during early stages of penetration when friction
leased at a predetermined point so as to acquire momentum
along the inner wall of the barrel is low. Oversampling occurs
while falling toward the bed. A momentum-driven piston
becausesedimentlayingbelowandoutsidethebitshiftinward
sampler generally penetrates deeper than a momentum-driven
as the bit cuts downward.
open-barrel sampler provided the two samplers have equal
4.7 Core-Barrel Length—Asampler’s core barrel should be
weights, e
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