环境地质学
Environmental Geology
主讲人,万新南 教授
Prof,Wan xinnan
环境地质学 Environmental Geology
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
6,Pre降水、江河与洪水
7,Mass Wasting Processes 表层整体再塑
（滑坡、泥石流、溶蚀、塌陷）
8、海岸线与海岸塑造过程
9、生态与植被
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
7,Mass Wasting Processes
表层整体再塑
（滑坡、泥石流、溶蚀、塌陷）
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
There is nothing inorganic...,The earth is
not a mere fragment of dead history,
stratum upon stratum like the leaves of a
book,to be studied by geologists and
antiquaries古玩家 chiefly,but living poetry
like the leaves of a tree,which precedes
flowers and fruit-not a fossil earth,but a
living earth...,
Henry David Thoreau
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
A,Flowing sand,landslides,and rock
falls are examples of mass wasting,the
general term for gravitationally induced
downslope movement of debris,
B,Mass-wasting processes operate on
sloping lands; eventually the debris
reaches a stream or gully where fluvial
processes continue the erosional
process,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Rockfall
Rockfall occurs where a
cliff of bedrock is exposed to
weathering and pieces of
the bedrock are pried loose
and fall,bounce,or roll to
rest at the base of the cliff,
The resulting deposit is
called talus崩塌岩堆 (Behre,
1933; Schumm and Chorley,
1966; Rapp,1976),In an
irregularly eroded cliff,talus
cones may develop in the
gully冲沟 head areas
(Fig.6.2),In more extensive
cliffs,coalescing聚集 talus
cones form a more
continuous blanket of debris
referred to as scree 山麓碎
石 (Jeffreys,1932; Adrews,
1961),
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Rockfall
Talus will not rest at an
angle greater than the angle
of repose,The angle of
repose is measured similarly
to dip of sedimentary rocks,
i.e.,from the horizontal,and
is typically about 33-35°,
Bedrock composition,as
well as talus particle size,
angularity,and sorting,has
some effect on the angle of
repose; large angular
boulders may rest at up to
40°, The angle of repose of
open-pit mine waste rock is
approximately 38°,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Rockfall
One of the world's most
famous talus slopes is the
one which formed an
impedment障碍 to
prospectors开拓者 during
the Klondike gold rush of
1898,the snow-covered
talus slope,called the
Scales,was the only access
to Chilkoot Pass and the
Yukon River,The pass was
guarded by the Canadian
Northeast Police,who
required every prospector to
carry 1 ton of supplies up
the slope and into the
interior,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
One of the world's most
famous talus slopes is the
one which formed an
impedment障碍 to
prospectors开拓者 during
the Klondike gold rush of
1898,the snow-covered
talus slope,called the
Scales,was the only
access to Chilkoot Pass
and the Yukon River,The
pass was guarded by the
Canadian Northeast Police,
who required every
prospector to carry 1 ton
of supplies up the slope
and into the interior.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Creep
Creep is the slow,
downslope movement of
soil,weathered rock,or
other surficial debris,
Movement is by
quasiviscous flow,
occurring under shear
stresses sufficient to
produce permanent
deformation,but too small
to result in a discrete
failure surface such as a
landslide,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Creep
Creep may be caused
by numerous phenomena,
For example,in terrains
subject to frost,rock or
soil may get heaved up
perpendicular to the slope
upon freezing,and
returned vertically
downward during a thaw,
Thus,over time,material
on a slope is likely to
move downhill,Micro-
landslides and random
movements such as
overturned trees,etc.,all
contribute to creep.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Landslide is the process whereby a
distinct mass of rock or soil moves
downslope due to gravity,
Landslides,unlike creep,have one
or more distinct failure surfaces,
Landslide velocities are typically on
the order of 1 m/day to perhaps 300
km/hr as in the special case of air-
entrapped landslides generated by
earthquakes,Shreve (1968) believes
that the prehistoric Blackhawk
Landslide in California slid at
immense speeds on a layer of
compressed air that was trapped
beneath the debris,The landslide,
consisting of 320 million m3,
traveled 8 km across a desert floor
at an average slope of 2.5°, [Hsu
(1975) challenges the airlubrication
空气润滑 hypothesis假说 in favor of
a debris flow mobilized by collision
of particles within a dust-laden
cloud.],
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Landslide activity typically increases
after prolonged rains,or after the frost
leaves the ground in the spring,The
novelist Firtsch (1980) describes the
ominous hazard of landslides which
weighs heavily on the minds of people
who live in the steep slopes of the
Swiss Alps,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Classification of landslides,For
simplicity,landslides can be classified
into two groups,1) translational,and 2)
rotational.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Translational landslides (Fig.6.8)
slide along a bedding plane or other
plane of weakness in the rock,The
entire mass moves parallel to this
plane,as illustrated in the rock slide in
Fig.6.1,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Probably the largest translational
landslide to occur in historic times
happened in 1925 in the Gros Ventre
River Valley in Wyoming (Fig.6.8A),
About 40 million m3 of Pennsylvania
Tensleep Sandstone slid on a bedding
plane inclined about 20°, Heavy rain
and stream undercutting at the base of
the mountain slope contributed to the
failure (Voight,1978),A 45 km2 lake
formed behind the debris; two years
later the dam was overtopped by
heavy spring runoff,and six people
drowned淹死 in the ensuing跟着发生
flood,The 1903 landslide disaster at
the mining town of Frank,Alberta,was
a translational slide which developed
along a prominent set of joints which
dip into the valley.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Rotational landslides (“slumps” or
“slips”) develop in surficial deposits or
weathered rock (fig6.1),They may be
natural in origin or induced by man,
The failure surface is roughly arcuate
弧形 in cross section (spoon-shaped in
three dimensions),At some places the
occurrence of a landslide at the base
of a hill may leave the hillslope above
unsupported,and so another landslide
occurs (Crandell,1951),The chain-
reaction type of stair-stepping slope
failure up a hill is called progressive
failure,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
22 Mathematical analysis,
Mathematical models of landslide
stability are presented in Terzaghi
(1950; 1962),Scheidegger (1961),
Stout (1969),Jaeger (1972),Schuster
and Krizek (1978),and Huang (1983),
Most problems involving the stability of
slopes are associated with the design
and construction of unbraced无支挡
cuts for highways,A very generalized
rule-of-thumb is given by Terzaghi and
Peck (1948):
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
The role of rock anisotropies is very
important in the design of stable slopes,
Fig4.24 shows an example of a
stereographic solution of a possible
wedge failure due to two prominent
planar anisotropies on a deep cut,The
use of stereoplots in analysis of slope
stability is explained in other Chapter.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Consider the landslide cross section
shown in Fig.6.16 having a unit
thickness of 1 m,Assume the debris
consists of three layers of known
density and shearing strength as
shown,First assume a trial failure
plane #1 (ABCD),The slide can be
arbitrarily divided into a convenient
number of slices,and the moment of
each computed, Accurate drafting and
measurement of moment arms is
necessary,The sum of the eight
driving moments is 29,507 kN-m,The
resisting moment is then determined,
and is equal to the shearing strength
(in this case the so-called undrained
shear strength Su is used) times the
length of arc in each slice times the
moment arm,The sum of the resisting
moments is calculated to be 34,500
kN-m,The factor of safety,F.S.,is
equal to the ratio of resisting moment
to driving moment:
F.S,(2.2.9)
In this case:
FS=34,156/29,507=1.16
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Consider the landslide cross section
shown in Fig.6.16 having a unit
thickness of 1 m,Assume the debris
consists of three layers of known
density and shearing strength as
shown,First assume a trial failure
plane #1 (ABCD),The slide can be
arbitrarily divided into a convenient
number of slices,and the moment of
each computed, Accurate drafting and
measurement of moment arms is
necessary,The sum of the eight
driving moments is 29,507 kN-m,The
resisting moment is then determined,
and is equal to the shearing strength
(in this case the so-called undrained
shear strength Su is used) times the
length of arc in each slice times the
moment arm,The sum of the resisting
moments is calculated to be 34,500
kN-m,The factor of safety,F.S.,is
equal to the ratio of resisting moment
to driving moment:
F.S,(2.2.9)
In this case:
FS=34,156/29,507=1.16
Environmental Geology
主讲人,万新南 教授
Prof,Wan xinnan
环境地质学 Environmental Geology
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
6,Pre降水、江河与洪水
7,Mass Wasting Processes 表层整体再塑
（滑坡、泥石流、溶蚀、塌陷）
8、海岸线与海岸塑造过程
9、生态与植被
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
7,Mass Wasting Processes
表层整体再塑
（滑坡、泥石流、溶蚀、塌陷）
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
There is nothing inorganic...,The earth is
not a mere fragment of dead history,
stratum upon stratum like the leaves of a
book,to be studied by geologists and
antiquaries古玩家 chiefly,but living poetry
like the leaves of a tree,which precedes
flowers and fruit-not a fossil earth,but a
living earth...,
Henry David Thoreau
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
A,Flowing sand,landslides,and rock
falls are examples of mass wasting,the
general term for gravitationally induced
downslope movement of debris,
B,Mass-wasting processes operate on
sloping lands; eventually the debris
reaches a stream or gully where fluvial
processes continue the erosional
process,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Rockfall
Rockfall occurs where a
cliff of bedrock is exposed to
weathering and pieces of
the bedrock are pried loose
and fall,bounce,or roll to
rest at the base of the cliff,
The resulting deposit is
called talus崩塌岩堆 (Behre,
1933; Schumm and Chorley,
1966; Rapp,1976),In an
irregularly eroded cliff,talus
cones may develop in the
gully冲沟 head areas
(Fig.6.2),In more extensive
cliffs,coalescing聚集 talus
cones form a more
continuous blanket of debris
referred to as scree 山麓碎
石 (Jeffreys,1932; Adrews,
1961),
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Rockfall
Talus will not rest at an
angle greater than the angle
of repose,The angle of
repose is measured similarly
to dip of sedimentary rocks,
i.e.,from the horizontal,and
is typically about 33-35°,
Bedrock composition,as
well as talus particle size,
angularity,and sorting,has
some effect on the angle of
repose; large angular
boulders may rest at up to
40°, The angle of repose of
open-pit mine waste rock is
approximately 38°,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Rockfall
One of the world's most
famous talus slopes is the
one which formed an
impedment障碍 to
prospectors开拓者 during
the Klondike gold rush of
1898,the snow-covered
talus slope,called the
Scales,was the only access
to Chilkoot Pass and the
Yukon River,The pass was
guarded by the Canadian
Northeast Police,who
required every prospector to
carry 1 ton of supplies up
the slope and into the
interior,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
One of the world's most
famous talus slopes is the
one which formed an
impedment障碍 to
prospectors开拓者 during
the Klondike gold rush of
1898,the snow-covered
talus slope,called the
Scales,was the only
access to Chilkoot Pass
and the Yukon River,The
pass was guarded by the
Canadian Northeast Police,
who required every
prospector to carry 1 ton
of supplies up the slope
and into the interior.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Creep
Creep is the slow,
downslope movement of
soil,weathered rock,or
other surficial debris,
Movement is by
quasiviscous flow,
occurring under shear
stresses sufficient to
produce permanent
deformation,but too small
to result in a discrete
failure surface such as a
landslide,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Creep
Creep may be caused
by numerous phenomena,
For example,in terrains
subject to frost,rock or
soil may get heaved up
perpendicular to the slope
upon freezing,and
returned vertically
downward during a thaw,
Thus,over time,material
on a slope is likely to
move downhill,Micro-
landslides and random
movements such as
overturned trees,etc.,all
contribute to creep.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Landslide is the process whereby a
distinct mass of rock or soil moves
downslope due to gravity,
Landslides,unlike creep,have one
or more distinct failure surfaces,
Landslide velocities are typically on
the order of 1 m/day to perhaps 300
km/hr as in the special case of air-
entrapped landslides generated by
earthquakes,Shreve (1968) believes
that the prehistoric Blackhawk
Landslide in California slid at
immense speeds on a layer of
compressed air that was trapped
beneath the debris,The landslide,
consisting of 320 million m3,
traveled 8 km across a desert floor
at an average slope of 2.5°, [Hsu
(1975) challenges the airlubrication
空气润滑 hypothesis假说 in favor of
a debris flow mobilized by collision
of particles within a dust-laden
cloud.],
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Landslide activity typically increases
after prolonged rains,or after the frost
leaves the ground in the spring,The
novelist Firtsch (1980) describes the
ominous hazard of landslides which
weighs heavily on the minds of people
who live in the steep slopes of the
Swiss Alps,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Classification of landslides,For
simplicity,landslides can be classified
into two groups,1) translational,and 2)
rotational.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Translational landslides (Fig.6.8)
slide along a bedding plane or other
plane of weakness in the rock,The
entire mass moves parallel to this
plane,as illustrated in the rock slide in
Fig.6.1,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Probably the largest translational
landslide to occur in historic times
happened in 1925 in the Gros Ventre
River Valley in Wyoming (Fig.6.8A),
About 40 million m3 of Pennsylvania
Tensleep Sandstone slid on a bedding
plane inclined about 20°, Heavy rain
and stream undercutting at the base of
the mountain slope contributed to the
failure (Voight,1978),A 45 km2 lake
formed behind the debris; two years
later the dam was overtopped by
heavy spring runoff,and six people
drowned淹死 in the ensuing跟着发生
flood,The 1903 landslide disaster at
the mining town of Frank,Alberta,was
a translational slide which developed
along a prominent set of joints which
dip into the valley.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Rotational landslides (“slumps” or
“slips”) develop in surficial deposits or
weathered rock (fig6.1),They may be
natural in origin or induced by man,
The failure surface is roughly arcuate
弧形 in cross section (spoon-shaped in
three dimensions),At some places the
occurrence of a landslide at the base
of a hill may leave the hillslope above
unsupported,and so another landslide
occurs (Crandell,1951),The chain-
reaction type of stair-stepping slope
failure up a hill is called progressive
failure,
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
22 Mathematical analysis,
Mathematical models of landslide
stability are presented in Terzaghi
(1950; 1962),Scheidegger (1961),
Stout (1969),Jaeger (1972),Schuster
and Krizek (1978),and Huang (1983),
Most problems involving the stability of
slopes are associated with the design
and construction of unbraced无支挡
cuts for highways,A very generalized
rule-of-thumb is given by Terzaghi and
Peck (1948):
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
The role of rock anisotropies is very
important in the design of stable slopes,
Fig4.24 shows an example of a
stereographic solution of a possible
wedge failure due to two prominent
planar anisotropies on a deep cut,The
use of stereoplots in analysis of slope
stability is explained in other Chapter.
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Consider the landslide cross section
shown in Fig.6.16 having a unit
thickness of 1 m,Assume the debris
consists of three layers of known
density and shearing strength as
shown,First assume a trial failure
plane #1 (ABCD),The slide can be
arbitrarily divided into a convenient
number of slices,and the moment of
each computed, Accurate drafting and
measurement of moment arms is
necessary,The sum of the eight
driving moments is 29,507 kN-m,The
resisting moment is then determined,
and is equal to the shearing strength
(in this case the so-called undrained
shear strength Su is used) times the
length of arc in each slice times the
moment arm,The sum of the resisting
moments is calculated to be 34,500
kN-m,The factor of safety,F.S.,is
equal to the ratio of resisting moment
to driving moment:
F.S,(2.2.9)
In this case:
FS=34,156/29,507=1.16
Part three 地球表层的塑造过程
环境地质学 Environmental Geology
Mass Wasting Processes
Landslides
Consider the landslide cross section
shown in Fig.6.16 having a unit
thickness of 1 m,Assume the debris
consists of three layers of known
density and shearing strength as
shown,First assume a trial failure
plane #1 (ABCD),The slide can be
arbitrarily divided into a convenient
number of slices,and the moment of
each computed, Accurate drafting and
measurement of moment arms is
necessary,The sum of the eight
driving moments is 29,507 kN-m,The
resisting moment is then determined,
and is equal to the shearing strength
(in this case the so-called undrained
shear strength Su is used) times the
length of arc in each slice times the
moment arm,The sum of the resisting
moments is calculated to be 34,500
kN-m,The factor of safety,F.S.,is
equal to the ratio of resisting moment
to driving moment:
F.S,(2.2.9)
In this case:
FS=34,156/29,507=1.16
