MASS PHYSICAL SEDIMENT PROPERTIES
Burghard W. Flemming and Monique T. Delafontaine
Department of Marine Research, Senckenberg Institute,
Wilhelmshaven, Germany
Synonyms
Engineering properties of sediments; Geotechnical sediment properties; Soil mechanics; Soil physics
Definition
The expression “mass physical sediment properties”, in
engineering also known as geotechnical sediment properties, refers to the physical nature of a sediment or soil,
including its behavior when exposed to external forces.
Introduction
This contribution only examines the more commonly used
mass physical properties. More comprehensive technical
treatments can be found in Lambe and Whitman (1969),
Carver (1971), Inderbitzen (1974), Mitchell (1976), Dunn
et al. (1980), Hillel (1998), and Warrick (2002). The physical properties of the sediment particles (e.g., grain size
and mineralogy) are not discussed in any detail here as
they are dealt with elsewhere in this encyclopedia.
The mass physical properties addressed in this contribution are the shear strength, water content, bulk density
(mass concentration), void ratio, porosity, permeability,
Atterberg limits, and carbonate content. Various combinations of these parameters allow a quantification or assessment of important parameters and processes, among them
material standing stocks and fluxes (e.g., Iversen and
Jørgensen, 1993; Bartholomä et al., 2000; Delafontaine
et al., 2000), but also sediment–organism relationships
in terms of, for example, biomass, species numbers or species richness per unit area, or sediment volume relative
to sediment type, food resources (e.g., organic matter,
particulate organic carbon, particulate organic nitrogen),
or pollution levels (e.g., heavy metals, PCBs, and other
toxic substances) (e.g., Pearson and Rosenberg, 1978;
Jumars and Wheatcroft, 1989; Meadows and Meadows,
1991; Snelgrove and Butman, 1994; Maxted et al., 1997;
Mulsow et al., 1998; Flemming and Delafontaine, 2000;
Delafontaine et al., 2004).
Definition of units and associated terminology
The rules for the usage of various physical units, including
their symbols and associated nomenclature, have been laid
down in the International System of Units (SI) in Oceanography (e.g., UNESCO, 1985). Unfortunately these rules
are even today frequently violated (see Williams, 2004). In
this context, the terms content (mass per unit mass) and
concentration (mass per unit volume) are often confused
or used synonymously (cf. Flemming and Delafontaine,
2000). This may partly be due to the fact that the two terms
are not clearly distinguished in the SI rules for units.
Therefore, to avoid any misunderstandings, the units associated with material contents and concentrations are
specifically defined and explained below.
Content
A content is a measure of the mass (or number or volume)
of a substance in a unit mass of sediment and is commonly
measured in g kg
À1
, mg g
À1 , or mg g
À1 (or number or
volume per kg, g, mg, or mg). Correspondingly, one speaks
of mass content (e.g., mass of solids per unit mass of sediment), number content (e.g., particle number per unit
mass of sediment), or volume content (e.g., pore space
per unit mass of sediment). Contents are often expressed
as percentage values of the total sediment, e.g., weight%
in the case of mass contents.
Concentration
A concentration is a measure of the mass (or number or
volume) in a unit volume of sediment and is commonly
measured in kg m
À3
, g dm
À3 (or g l
À1
, i.e., grams per
liter), g cm
À3
, or mg cm
À3 (or number or volume per
m
3
, dm
3
, or cm
3
). Correspondingly, one speaks of mass
concentration (e.g., mass of solids per unit volume of
sediment), number concentration (e.g., particle number
per unit volume of sediment), or volume concentration
(e.g., pore space per unit volume of sediment).
Although the two measures are closely related, the relationship between the two is neither simple nor straightforward, and sometimes even counterintuitive, as illustrated
in Figure 1 by the very different trends described by
the total sediment (sand + mud, i.e., grain size of
2,000–63 mm and <63 mm, respectively) and the individual sand and mud concentration curves as a function of the
mud content. Initially the latter two curves follow an
expected trend, the mud concentration increasing as the
sand concentration decreases. However, at a mud content
of about 60 % (in this example), the mud concentration
curve peaks and then, quite unexpectedly, also decreases
with further increases in mud content. As will be
explained below, the reason for this counterintuitive trend
is the increasing water content of the sediment and associated changes in the network structure (fabric) of sand–
mud mixtures. Note that the sediment type classification
at the top of Figure 1 follows the scheme proposed by
Flemming (2000).
The example in Figure 1 shows that a change in content
of a sedimentary component (here mud) is automatically
accompanied by a change in concentration, even though
not always in a predictable or obvious way. A change
in concentration, on the other hand, is not necessarily
accompanied by a corresponding change in content. For
example, the compaction of mud by expulsion of water
(e.g., in the course of compaction) will not change
the mud content per unit sediment mass, but the material
concentration will increase proportionally to the decrease
MASS PHYSICAL SEDIMENT PROPERTIES
419
Burghard W. Flemming and Monique T. Delafontaine
Department of Marine Research, Senckenberg Institute,
Wilhelmshaven, Germany
Synonyms
Engineering properties of sediments; Geotechnical sediment properties; Soil mechanics; Soil physics
Definition
The expression “mass physical sediment properties”, in
engineering also known as geotechnical sediment properties, refers to the physical nature of a sediment or soil,
including its behavior when exposed to external forces.
Introduction
This contribution only examines the more commonly used
mass physical properties. More comprehensive technical
treatments can be found in Lambe and Whitman (1969),
Carver (1971), Inderbitzen (1974), Mitchell (1976), Dunn
et al. (1980), Hillel (1998), and Warrick (2002). The physical properties of the sediment particles (e.g., grain size
and mineralogy) are not discussed in any detail here as
they are dealt with elsewhere in this encyclopedia.
The mass physical properties addressed in this contribution are the shear strength, water content, bulk density
(mass concentration), void ratio, porosity, permeability,
Atterberg limits, and carbonate content. Various combinations of these parameters allow a quantification or assessment of important parameters and processes, among them
material standing stocks and fluxes (e.g., Iversen and
Jørgensen, 1993; Bartholomä et al., 2000; Delafontaine
et al., 2000), but also sediment–organism relationships
in terms of, for example, biomass, species numbers or species richness per unit area, or sediment volume relative
to sediment type, food resources (e.g., organic matter,
particulate organic carbon, particulate organic nitrogen),
or pollution levels (e.g., heavy metals, PCBs, and other
toxic substances) (e.g., Pearson and Rosenberg, 1978;
Jumars and Wheatcroft, 1989; Meadows and Meadows,
1991; Snelgrove and Butman, 1994; Maxted et al., 1997;
Mulsow et al., 1998; Flemming and Delafontaine, 2000;
Delafontaine et al., 2004).
Definition of units and associated terminology
The rules for the usage of various physical units, including
their symbols and associated nomenclature, have been laid
down in the International System of Units (SI) in Oceanography (e.g., UNESCO, 1985). Unfortunately these rules
are even today frequently violated (see Williams, 2004). In
this context, the terms content (mass per unit mass) and
concentration (mass per unit volume) are often confused
or used synonymously (cf. Flemming and Delafontaine,
2000). This may partly be due to the fact that the two terms
are not clearly distinguished in the SI rules for units.
Therefore, to avoid any misunderstandings, the units associated with material contents and concentrations are
specifically defined and explained below.
Content
A content is a measure of the mass (or number or volume)
of a substance in a unit mass of sediment and is commonly
measured in g kg
À1
, mg g
À1 , or mg g
À1 (or number or
volume per kg, g, mg, or mg). Correspondingly, one speaks
of mass content (e.g., mass of solids per unit mass of sediment), number content (e.g., particle number per unit
mass of sediment), or volume content (e.g., pore space
per unit mass of sediment). Contents are often expressed
as percentage values of the total sediment, e.g., weight%
in the case of mass contents.
Concentration
A concentration is a measure of the mass (or number or
volume) in a unit volume of sediment and is commonly
measured in kg m
À3
, g dm
À3 (or g l
À1
, i.e., grams per
liter), g cm
À3
, or mg cm
À3 (or number or volume per
m
3
, dm
3
, or cm
3
). Correspondingly, one speaks of mass
concentration (e.g., mass of solids per unit volume of
sediment), number concentration (e.g., particle number
per unit volume of sediment), or volume concentration
(e.g., pore space per unit volume of sediment).
Although the two measures are closely related, the relationship between the two is neither simple nor straightforward, and sometimes even counterintuitive, as illustrated
in Figure 1 by the very different trends described by
the total sediment (sand + mud, i.e., grain size of
2,000–63 mm and <63 mm, respectively) and the individual sand and mud concentration curves as a function of the
mud content. Initially the latter two curves follow an
expected trend, the mud concentration increasing as the
sand concentration decreases. However, at a mud content
of about 60 % (in this example), the mud concentration
curve peaks and then, quite unexpectedly, also decreases
with further increases in mud content. As will be
explained below, the reason for this counterintuitive trend
is the increasing water content of the sediment and associated changes in the network structure (fabric) of sand–
mud mixtures. Note that the sediment type classification
at the top of Figure 1 follows the scheme proposed by
Flemming (2000).
The example in Figure 1 shows that a change in content
of a sedimentary component (here mud) is automatically
accompanied by a change in concentration, even though
not always in a predictable or obvious way. A change
in concentration, on the other hand, is not necessarily
accompanied by a corresponding change in content. For
example, the compaction of mud by expulsion of water
(e.g., in the course of compaction) will not change
the mud content per unit sediment mass, but the material
concentration will increase proportionally to the decrease
MASS PHYSICAL SEDIMENT PROPERTIES
419