Rock Mechanics 4, 71--78 (1972)
(g) by Springer-VerIag 1972
Classification of Landslides and Other Mass Movements
By
A. Nemeok, J. Pa~ek, and J. RybM"
With 4 Figures
(Received September 30, 1971)
Summary
--
Zusammenfassung
--
R~sumd
Classification of Landslides and Other Mass Movements. This paper presents
a new universal classification of slope movements, destined for the purpose of'
engineering geological mapping. This classification was compiled after critical evaluation of the classifications used by now, on the basis of the experience gained by
systematic study of slope movements in Czechoslovakia.
The following 4 types of slope processes are recognized regarding to the geomechanical character and velocity of the movement: creep, sliding, flow and fall.
C r e e p is a geologically long-term movement of non-increasing velocity without
well-defined sliding surfaces. Sliding is a slope movement of coherent masses
along one or more well-defined shear surfaces. Flow represents slope movements
in rocks and soils, analogous to the movements in liquids. Fall is a sudden slope
movement; the moving mass loses its coherence and, for a short time, also its
contact with the underlying rock.
The pictures show the elementary types of movements that are obvious in
the European climatic conditions. Graphical representation of dimensions and
velocity of the phenomena is included.
Klassifikation yon Rutschungen und anderen Hangbewegungen. Die vorgeschlagene Klassifikation geht zurtick auf systematische Untersuchungen an Rutschgebieten in der CSSR. Sie lehnt sich an die besten gebr/iuchlichen Klassifikationen
an, wobei letztere einer kritischen Beurteilung unterzogen werden. Ziel des neuen
Vorschlages ist die Erarbeitung yon Kriterien ftir die ingenieurgeologische Kartierung.
Auf Grund des geomechanischen Charakters der Bodenbewegungen werden
folgende vier Vorg/inge unterschieden: Kriechen - - geologisch langandauernde,
nicbt beschleunigte Bewegungen ohne ausgepr~igte Gleitfl/ichen; Gleiten - - Hangbewegungen zusammenh~ingender Massen l~ings einer oder mehrerer Gleitfl~ichen;
Flief~en - - Hangbewegungen yon fliissigkeits~ihnlichem Charakter; Fallen - - pl6tzliche Hangbewegungen, wobei die bewegte Masse den inneren Zusammenhang und
kurzfristig auch den Kontakt mit dem Liegenden verliert.
Die Grundtypen werden an Hand europ/iischer Beispiele graphisch dargestellt
und durch Angaben tiber Gr6tgenordnung der Massen und deren durchschnittliche
Geschwindigkeit erg/inzt.
Classification des glissements et autres mouvements de terrain. D'aprhs les
exp&iences acquises pendant les 6tudes de glissements en Tch&oslovaquie et d'apr6s
Rock Mechanics, Vol. 4/2
6
72
A. Nem~ok, J. Pa~ek, and J. Rybli~:
l'examen critique des classifications employ6es jusqu'ici, on a recommend6 la
classification suivante, destin6e avant tout au lev4 de g6ologie de l'ing6nieur.
En relation avec le caract6re g4om4canique des mouvements de pente et de leur
vitesse, quatre processus sont distinguds: fluage, glissement, 4coulement, dcroulement. Le fluage - - mouvements g4ologiquement de longue durde, sans acc416ration et sans surfaces de glissement exprim6es. Le glissement - - mouvements de
pente de masses coh4rentes, le long d'une ou de plusieurs surfaces de glissement.
L'dcoulement - - mouvements de pente dans les roches et les sols, analogues aux
mouvements dans les liquides. L'&roulement - - mouvements de pente soudains,
au cours desquelles les masses en mouvement perdent enti&ement leur connexion
int&ieure et, pour un temps aussi, le contact avec le sous-sol.
Les exemples sur les figures repr&entent les types principaux des mouvements
courants dans les conditions climatiques de l'Europe. On indique aussi les dimensions et la vitesse moyenne des types individuels.
The increasing amount and extent of engineering structures such as
large dams, highways, and power stations as well as open-pit mining often
requires large-scale human interference in nature. In these circumstances we
often encounter a number of obstacles caused by natural features. One of
them is the problem of slope stability and related processes, namely landslides and other mass movements. Recently concentrated attention has been
given to engineering geological research on these processes that result from
the displacement of soils and rocks induced by gravitation force in consequence of the disturbance of the natural stability.
Extensive knowledge and intensive continuous study of these processes
and of their origin and development is needed in order to be able to make
a correct diagnosis and particularly to effect the necessary prevention in due
time. For these reasons, the compilation of an universal classification is
essential and indispensable. This will be, however, a hard and thankless
task.
The morphological and geological structure of Czechoslovakia creates
favourable conditions for the occurence of these phenomena. This exerts,
of course, an unfavourable influence on the national economy. For these
reasons, slope processes have been subject of intensive studies in Czechoslovakia for many years. The research was based on the result of the registration of all large landslides on the territory of Czechoslovakia, carried out
in 1962--1963 (Ryb~i~, P a ~ e k and R e p k a , 1965) as well as on the old
tradition of the lifework of Q. Z f i r u b a ( Z f i r u b a and M e n c l , 1969).
After many earlier classifications ( A l m a g i a , 1910; E c k e l , 1958;
H e i m , 1882; H u t c h i n s o n , 1968; J e m e l j a n o v a , 1963; K l e c z k o w s k i ,
1955; L a d d , 1935; N e m ~ o k and Rybfi~', 1968; R o d i o n o v , 1939;
S h a r p e , 1938; S t i n y , 1941; T e r - S t e p a n i a n ,
1966; T e r z a g h i , 1959;
Z f i r u b a and M e n c l , 1961; Z o l o t a r i e v , 1963) and analyzing critically
(Spfirek, 1966), the authors suggest the following classification, the principles of which are given below.
In general, we speak of slope movements in rocks, in ice and in snow.
For the use of practical engineering geology we shall deal with the slope
movements in the rocks only, namely in the non-solid rocks (soils), semi-
Classification of Landslides and Other Mass Movements
73
solid rocks (soft rocks) and in solid rocks, despite the fact that in certain
regional conditions the movements of snow and ice and of frozen rocks are
also of importance.
According to the geomechanical character and velocity of the movement we distinguish the following 4 types of processes:
English
German
French
Russian
creep
sliding
flow
fall
Kriechen
Gleiten
Fliet~en
Fallen
fluage
glissement
8coulement
8croulement
polzu~est'
opolzanije
te~enije
obru~enije
From the kinetical point of view of the kinetics of the motion, these
phenomena can be defined as follows:
C r e e p - - geologically long-term movements of non-increasing velocity
without well-defined sliding surfaces. In most cases we can speak of deepseated (or viscous) flow. The movements are designated as creeping movements, the resulting phenomenon is rock creep, talus creep or soil creep.
If it achieves a critical acceleration, the creep becomes sliding, flow or fall.
In this case, creep is a preparatory stage to sliding, flow or fall.
S l i d i n g - - slope movements of coherent masses along one or more welldefined shear surfaces. We define this movement as a landslide.
F l o w - - slope movement in rocks and soils, analogous to the movements
in liquids. We refer to mudflows or earthflows and rock streams.
F a l l - - sudden slope movement; the moving masses lose their coherence
and for a short time also their contact with the underlying rock. We refer
to rock falls.
In each group, the elementary phenomena can be further subdivided
according to different types determined by regional, morphological, geological or climatic conditions. For this reason, we abstain from more detailed
classification, as we realize that we are not able to consider all possible
variations.
A number of examples are presented only in order to make clear the
principles of the elementary division of these phenomena. They do not
represent anything but a set of examples of elementary types, known especially from Europe.
Each picture contains also a graphical representation of dimensions and
velocity of the phenomenon. The explanation in the text is very brief; it
explains nothing but that which cannot be expressed graphically. The terms
used are proposed for the professional use; they represent only a verbal
translation of the Czech text.
Examples Nos. 1--9 demonstrate creep (Fig. 1). Nos. 1--8 are examples
of deep-seated creep ( N e m ~ o k and Rybfi~, 1968), No. 9 is example of
superficial creep.
6*
74
A. Nem~ok, J. Pa~ek, and J. Ryb~i~:
No. 1 - - loosening of the rocks in the valley slope by cracks parallel to
the surface. This phenomenon is typical of brittle rocks.
No. 2 - - initial stage of disturbing of the stability of the slope by opening of tension cracks in its upper part.
Nos. 3 and 4 - - deep-seated creep grading into sliding in the upper part
of the slope. It is the same phenomenon often described under the old terms
"Talzuschub" and "Bergzerreitgung". If a geologist finds a crack in a moun-
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Fig. 1. Examples Nos. 1--9 belonging to the group "creep"
Beispiele Nr. 1--9 zur Gruppe ,,Kriechen"
Exemples Nos. 1--9 concernant le groupe "fluage"
tain ridge, he calls this phenomenon "Bergzerreigung". If a civil engineer
ascertains some deformation at the toe of a slope, in a foundation pit or
in tunnels, he speaks of "Talzuschub". Example No. 3 is typical of brittle
rocks, example No. 4 of cleaved rocks - - it is the so-called Sackung
( Z i s c h i n s k y , 1966).
No. 5 - - partly analogous to the example No. 4 is gravitational folding
observed in coaly and clayey complexes along the margins of the Tertiary
basins in Czechoslovakia and in Germany, occuring also in limestones with
marly interlayers in geosynclinal mountains.
Classification of Landslides and Other Mass Movements
75
Nos. 6 and 7 - - block-type m o v e m e n t s along a pre-existing surface or
pre-disposed zone on a plastic underlying rock. T h e d e v e l o p m e n t of blocktype m o v e m e n t s c o n n e c t e d with the r o t a t i o n of the blocks is c o m m o n , w h e r e
the u p p e r p a r t of the slope is m a d e up of solid rocks and the lower p a r t of
plastic clays.
N o . 8 - - relatively m o r e plastic rocks are squeezed o u t in the b o t t o m
of an erosion valley and f o r m an anticlinal valley.
N o . 9 - - superficial creep in the zone of seasonal changes (bending of
beds).
Pictures Nos. 1 0 - - 1 3 illustrate sliding on a shear surface (Fig. 2). T h r e e
basic types are distinguished a c c o r d i n g to the type of the sliding surface.
N o . 10 - - sliding along a simple r o t a t i o n a l sliding surface. This type of
sliding is rarely f o u n d in nature; theoretically it should o c c u r only in a
h o m o g e n e o u s rock w i t h o u t any internal a n i s o t r o p h y .
No. 11 - - a landslide along a p l a n a r sliding surface. T h e sliding surface
is a lithologic or tectonic b o u n d a r y or on bedding, schistosity or jointing.
N o . 12 - - an a n a l o g o u s landslide in solid rocks ( M i i l l e r , 1964).
N o . 13 - - sliding along a c o m b i n e d sliding surface. This type of sliding
can be of various forms. T h e picture shows a c o m b i n a t i o n of b o t h cylindrical
and plane surfaces. It occurs often in horizontally b e d d e d argillaceous, m a r l y
or calcareous sediments.
No. 14 - - h o r i z o n t a l translation on a pre-existing sliding surface. T h e
slid masses are limited by plane surfaces of disturbance. Typical of this case
is the existence of a n o n - s t a b l e layer or zone at the toe of the slope. This
layer can be built of a soft or structurally sensitive clay. It can be, however,
also a position of silty sand p r o n e to liquefaction or a fossil, tectonically or
gravitationally c o n d i t i o n e d surface of displacement. O n the contrary, h o w -
Symbols used in figures 1 to 4
A = Dimension of the zone affected by slope movement: 1 - surface dimension; 2 - perpendicular dimension. The typical dimensions of individual examples in following drawings
ar dotted
B = Order of the average velocity of the slope movement: 3 - ram/day; 4 - m/hour;
5 - km/hour; 6 - 100 kin/hour
A = Gr6genordnung
gr6f~ten Ausdehnung;
die im
B = Gr6i~enordnung
mm/Tag-Bereich; 4 -
Erl~iuterungen zu den Abbildungen 1 bis 4
des yon der Hangbewegung erfat~ten Bereiches: 1 - in Richtung der
2 - in Richtung vertikal zur Hangoberflfiche. Die Gr6~enordnungen,
Gel~inde angetroffen wurden, sind punktiert eingetragen
der durchschnittlichen Geschwindigkeit der Hangbewegungen: 3 m/Stunde-Bereich; 5 - km/Stunde-Bereich; 6 - 100km/Stunde-Bereich
Notes explicatives pour les Fig. 1 - - 4
A = Ordre de grandeur de la zone affect& d'un mouvement de pente: 1 - dimension superficielle; 2 - dimension perpendiculaire. Les dimensions typiques pour les diff6rents exemples
suivants sont marqudes de points
B = Ordre de grandeur de Ia vitesse moyenne d'un mouvement de pente: 3 - en mm/jour;
4 - en m/heure; 5 - en km/heure; 6 - en 100 km/heure
76
A. NemSok, J. Pa~ek, and J. R y b ~ ' :
ever, this zone can be built of relatively elastic rock, concentrating the horizontal stresses. Being unloaded by a cutting, this stress changes into an expansible energy influencing unfavourably the stability of the slope.
j
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-C ~__._.4._~---c
14
Fig. 2. Examples Nos. 10--14 belonging to the group "sliding"
Beispiele Nr. 10--14 zur Gruppe ,,Gleiten"
Exemples Nos. 10--14 concernant le groupe "glissement"
15
16
Fig. 3. Examples Nos. 1S--17 belonging to the group "flow"
Beispiele Nr. 15--17 zur Gruppe ,,Fliet~en"
Exemples Nos. 13--17 concernant le groupe "dcoulement"
Pictures Nos. 15--17 illustrate flow (Fig. 3). This process includes also
solifluction and slope movements in quick-clays. The graphical illustration
of these cases would be very difficult.
No. 15 - - flowing of slope deposits as an earthflow.
No. 16 - - a debris flow; a mixture of water and fragments of rocks,
bouldery, stony sandy or loamy weathering products runs downslope.
Classification of Landslides and Other Mass Movements
77
No. 17 - - a superficial flow, affecting the superficial layers of soils on
every more inclined slope after a period of thawing.
The last group, namely falls, includes slope movements predominantly
in the mountains (Fig. 4).
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#'i / \
d~t( ~ \ \ ~<
/ Z\...x
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Fig. 4. Examples Nos. 18--21 belonging to the group "fall"
Beispiele Nr. 18--21 zur Gruppe ,,Fallen"
Exemples Nos. 18--21 concernant le groupe "&roulement"
No. 18 - - sudden displacement of small fragments by rolling downslope - - a process analogous to stone fall in relatively softer rocks. For
instance in young mountains exposed to intense mechanical weathering the
loosened rock fragments roll downslope, where a labile talus is formed.
No. 19 - - stone fall, occuring on steep rocky slopes.
No. 20 - - rock fall; this type of fall occurs mostly in mountains of the
Alpine type. It is a pure case of free fall.
No. 21 - - free fall combined with translation in the first stage. This
type of movement occurs more often than pure free fall.
This classification is, of course, only general. We publish it as a basis
for encouraging further discussion which should lead to the compilation of a
detailed classification scheme. This classification should involve all known
phenomena in our field and last but not least make possible also the classification of all special cases of regional occurence.
References
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Address of the authors: Doc. Dr. Arnold N e m ~ o k , CSc., Slovak Technical
University, Gottwaldovo n~im. 2, Bratislava, (2SSR. Ing. Jaroslav PaSek, CSc. and
Ing. Jan Ryb~i~, CSc., Geological Institute of Czechoslovak Academy of Sciences,
Bo~nl II/1401, Praha 4 - - Spo~ilov, CSSR.