Table Of ContentFurther titles in this series:
Volumes 2, 3, 5, 6, 7, 9, 10, 13, 16 and 26 are out of print
1. G. SANGLERAT — THE PENETROMETER AND SOIL EXPLORATION
4. R.SILVESTER —COASTAL ENGINEERING, 1 and 2
8. L.N. PERSEN — ROCK DYNAMICS AND GEOPHYSICAL EXPLORATION
Introduction to Stress Waves in Rocks
1 1. H.K. GUPTA AND B.K. RASTOGI — DAMS AND EARTHQUAKES
12. F.H. CHEN — FOUNDATIONS ON EXPANSIVE SOILS
14. B. VOIGHT (Editor) — ROCKSLIDES AND AVALANCHES, 1 and 2
15. C. LOMNITZ AND E. ROSENBLUETH (Editors) — SEISMIC RISK AND ENGINEERING DECISIONS
17. A.P.S. SELVADURAI — ELASTIC ANALYSIS OF SOIL-FOUNDATION INTERACTION
18. J. FEDA — STRESS IN SUBSOIL AND METHODS OF FINAL SETTLEMENT CALCULATION
19. Á. KÉZDI — STABILIZED EARTH ROADS
20. E.W. BRAND AND R.P. BRENNER (Editors) — SOFT-CLAY ENGINEERING
21. A. MYSLIVE AND Z. KYSELA — THE BEARING CAPACITY OF BUILDING FOUNDATIONS
22. R.N. CHOWDHURY — SLOPE ANALYSIS
23. P. BRUUN — STABILITY OF TIDAL INLETS
Theory and Engineering
24. Z. BAZANT — METHODS OF FOUNDATION ENGINEERING
25. Á. KÉZDI — SOIL PHYSICS
Selected Topics
27. D. STEPHENSON — ROCKFILL IN HYDRAULIC ENGINEERING
28. P.E. FRIVIK, N. JANBU, R. SAETERSDAL AND L.I. FINBORUD (Editors) — GROUND FREEZING 1980
29. P. PETER — CANAL AND RIVER LEVEES
30. J. FEDA — MECHANICS OF PARTICULATE MATERIALS
The Principles
31. Q. ZÁRUBA AND V. MENCL — LANDSLIDES AND THEIR CONTROL
Second completely revised edition
32. I.W. FARMER (Editor) — STRATA MECHANICS
33. L. HOBST AND J. ZAJÍC — ANCHORING IN ROCK AND SOIL
Second completely revised edition
34. G. SANGLERAT, G. OLIVARI AND B. CAMBOU — PRACTICAL PROBLEMS IN SOIL MECHANICS AND
FOUNDATION ENGINEERING, 1 and 2
35. L. RÉTHÁTI — GROUNDWATER IN CIVIL ENGINEERING
36. S.S. VYALOV — RHEOLOGICAL FUNDAMENTALS OF SOIL MECHANICS
37. P. BRUUN (Editor) — DESIGN AND CONSTRUCTION OF MOUNDS )FOR BREAKWATERS AND COASTAL
PROTECTION
38. W.F. CHEN AND G.Y. BALADI — SOIL PLASTICITY
Theory and Implementation
39. E.T. HANRAHAN — THE GEOTECTONICS OF REAL MATERIALS: THE eg, €k METHOD
40. J. ALDORF AND K. EXNER — MINE OPENINGS
Stability and Support
41. J.E. GILLOTT — CLAY IN ENGINEERING GEOLOGY
42. A.S. CAKMAK (Editor) — SOIL DYNAMICS AND LIQUEFACTION
42. A.S. CAKMAK (Editor) — SOIL-STRUCTURE INTERACTION
44. A.S. CAKMAK (Editor) — GROUND MOTION AND ENGINEERING SEISMOLOGY
45. A.S. CAKMAK (Editor) — STRUCTURES, UNDERGROUND STRUCTURES, DAMS, AND STOCHASTIC
METHODS
46. L. RÉTHÁTI — PROBABILISTIC SOLUTIONS IN GEOTECTONICS
47. B.M. DAS — THEORETICAL FOUNDATION ENGINEERING
48. W. DERSKI, R. IZBICKI, I. KISIEL AND Z. MROZ — ROCK AND SOIL MECHANICS
49. T. ARIMAN, M. HAMADA, A.C. SINGHAL, M.A. HAROUN AND A.S. CAKMAK (Editors) — RECENT
ADVANCES IN LIFELINE EARTHQUAKE ENGINEERING
50. B.M. DAS — EARTH ANCHORS
51. K. THIEL — ROCK MECHANICS IN HYDROENGINEERING
52. W.F. CHEN AND X.L. LIU — LIMIT ANALYSIS IN SOIL MECHANICS
53. W.F. CHEN AND E. MIZUNO — NONLINEAR ANALYSIS IN SOIL MECHANICS
54. F.H. CHEN — FOUNDATIONS ON EXPANSIVE SOILS
55. J. VERFEL — ROCK GROUTING AND DIAPHRAGM WALL CONSTRUCTION
Developments in Geotechnical Engineering, 56
Subsidence
Occurrence, Prediction and Control
Barry N. Whittaker and David J. Reddish
Department of Mining Engineering, The University of Nottingham,
University Park, Nottingham NG7 2RD (U.K.)
ELSEVIER
Amsterdam — Oxford — New York— Tokyo 1989
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PREFACE
Surface subsidence is recognised as a problem in most countries, particularly those with
significant mining and other underground resource extraction industries. This book addresses
the problems relating to subsidence whether caused naturally, or arising from mining or other
forms of underground extractive activity.
The character of subsidence can range from general lowering of the surface thereby often
resulting in a saucer or trough shaped depression to that of a distinct hole with vertical sides
and of appreciable depth and width. In many cases the occurrence of surface subsidence from
mining operations can be predicted but in some instances there is a degree of uncertainty with
the potential for some form of subsidence to occur later. The role played by time, although
generally recognised as a factor, has not been always thoroughly appreciated in terms of the
development or likely occurrence of subsidence at the surface.
Subsidence is usually associated with underground mining operations even though in
several cases subsequent surface subsidence may not be of any significance. There are also
many areas possessing a history of past mining, and the stability of the surface in respect of
existing and future structures and particular land uses is frequently questioned. There is a
pressing need for an improved understanding of the mechanics of mining subsidence
particularly regarding predicting its occurrence and characteristics. The mining subsidence
problem is compounded by the fact that its surface manifestation can take different forms
and have far reaching effects on different types of structure at or near the surface. There is a
world-wide wealth of knowledge on surface subsidence although such information is scattered
widely and not necessarily readily accessible or expressed in a form allowing its ease of
application to and comparison with related problems.
The main purpose of this book has been to bring together subsidence knowledge,
experiences and research findings in many countries and rationalise such information
especially in respect of its particular field of application. Emphasis has been given to collating
field data on subsidence from different countries in order to make direct comparisons.
Prediction of subsidence, particularly its occurrence and general characteristics has been seen
as an important area where the book can contribute significantly in terms of reviewing
available knowledge, methods, scope of application and orders of accuracy achieved. The
book also examines methods of controlling subsidence and discusses the response of surface
structures to and protection against subsidence.
The book refers extensively to research into mining subsidence carried out at the
Department of Mining Engineering, University of Nottingham, and the following persons
have made special contributions: Dr. T. R. C. Aston, Professor T. Atkinson, Dr. D. S. Berry,
Dr. C. D. Breeds, Dr. D. J. Forrester, Dr. R. Firman, Dr. D. J. Fitzpatrick, P. Gaskell, the
late Emeritus Professor H. J. King, J. C. Malcolm, J. N. van der Merwe, Dr. A. G.
Pasamehmetoglu, Dr. J. H. Pye, G. Ren, Dr. C. H. Shadbolt, S. F. Smith, A. Szeki, and K.
Wardell. Thanks are expressed to these and many other persons who have given valuable help
to the authors during preparation of this book.
The authors in their review of current knowledge pertaining to mining subsidence have
been greatly assisted by various publications and particularly from the British Coal
Corporation, Elsevier Science Publications, Pergamon Press Ltd., and the transactions of the
Institution of Mining Engineers and the Institution of Mining and Metallurgy to whom the
authors express their gratitude.
VI
The authors hope the book will create greater interest in achieving a better understanding
of the mechanics of mining subsidence and its associated aspects and provide a basis for
making improved assessments and predictions on subsidence related problems.
Barry N. Whittaker and David J. Reddish
Department of Mining Engineering
University of Nottingham
Nottingham.
CHAPTER 1
NATURAL SUBSIDENCE AND INFLUENCE OF GEOLOGICAL PROCESSES
The occurrence of subsidence in nature is well-known. It can take the form of regional
sinking of major parts of the earth's crust in one extreme whilst the localised occurrence of
small surface depressions due to formation of solution cavities in limestone represents
perhaps another extreme form of natural subsidence, although with widely differing time
scales.
The geological cycle involving transition from earth movement to denudation followed
by deposition, and thereafter further earth movement initiating the next cycle, is responsible
for the occurrence of significant natural subsidence. The effect of the geological cycle in
allowing selective and localised sedimentation to occur, is to produce disturbances in the
loading of the earth's crust and thus lead to earth movements involving combinations of
subsidence and uplift.
The meaning of subsidence
The term subsidence as applied to the earth's surface normally refers to a surface point
sinking to a lower level, and can include a structure settling into the ground or the ground
itself lowering and carrying the structure with it, or even a surface layer collapsing into an
underground cavity. Subsidence usually refers to vertical displacement of a point, but also
implies a measure of horizontal movement of adjacent points by virtue of the lateral shift of
ground generated by the accompanying downward movement.
Soil properties influence their settlement (which is a form of subsidence) behaviour,
particularly their consolidation characteristics in relation to the conditions and magnitude of
loading. Additionally soils exhibit shrinkage characteristics following loss of moisture, and
the obverse occurs on gaining moisture. Consequently, a certain degree of short-term
settlement is to be expected with many new structures depending upon the type of foundations
and the soils on which such foundations are built. Some structures experience long-term
settlement effects owing to fluctuating moisture changes in the foundation soils, especially
where the local water-table is highly sensitive to climatic conditions.
Subsidence of the surface commonly refers to en masse lowering of the ground rather
than the localised effect of consolidation or shrinkage of soils. Such sinking of the surface
may arise from regional geological reasons including tectonic or volcanic activities, or from
removal of material from below the surface as with tunnelling or mining operations, or from
localised natural causes such as occurs with swallow-holes or sink-holes in limestone country.
Some examples of natural subsidence involving relatively localised (as opposed to
regional) effects are illustrated in Figure 1; movement of land masses in the form of
gravitational slides is well-known particularly in mountainous regions, whilst earthquakes can
trigger additional and sudden lowering of unconsohdated deposits; collapse of cavities
created by groundwater solution of salt domes has resulted in subsidence of the surface
similar to collapse of large natural voids in lava flows.
A
-rr-r T" v. - - \ v^
(a) Earthquake induced movement along fault planes
(b) Earthquake induced additional and sudden subsidence of deltaic and other unconsolidated deposits
Salt dome
Void formed by action of groundwater Collapse of capping which can be
sudden and without warning
^B^^fWi
Lava flow
(c) Collapse of natural voids associated with salt domes and lava flows
(d) Natural instability of land masses resulting in gravitational slides which may creep or be triggered by other
natural phenomena
Figure 1 Examples of natural subsidence
3
Geological cycle in relation to natural subsidence
Legget (1962) draws attention to the role played by the geological cycle in producing the
structural features of the earth's crust as are evident today. The relevant processes involved
with the cycle have a major bearing on natural subsidence. There is ample evidence around
the world of major subsidence occurrences in the past. Natural subsidence continues to occur
in various parts of the world either as a fairly continuous or intermittent phenomenon or as
sudden manifestations triggered by earthquakes or collapse of capping over an underground
cavity.
Subsidence of the earth's surface is associated with the geological cycle, namely those
processes responsible for the structure of the earth's crust. The basic elements of the
geological cycle are (1) denudation, (2) deposition, and (3) earth movement, which repeats
itself.
The denudation, or weathering, element of the cycle includes the action of water
resulting in decomposition of rocks by erosion either mechanically or chemically, temperature
changes resulting in comminution of exposed rock surfaces, the effects of wind action
especially in arid regions, the action and effect of glaciation, and that of wave action of the
sea. The depositional element of the geological cycle mainly includes the action of water, and
to a significantly less extent that of wind, in the creation of accumulated deposits. The effect
of progressive deposition, accompanied by denudation, leads to disturbing the state of
equilibrium of rock pressures in parts of the earth's crust and can induce local and regional
vertical and consequential horizontal movements of the surface.
The earth movement element of the cycle is spasmodic in relation to the other two. The
effects of major earth movement occurrences in the past are strongly evident world-wide.
Volcanic activity occasionally triggers significant natural subsidence, although not on the
same scale or frequency as earthquakes.
Legget (1962) when discussing ground subsidence refers to substantial vertical
displacements triggered by earthquakes in New Zealand and the USA; in the first example at
Karamea the town was situated on deltaic deposits and sank 60cm, whilst in the second
example, this occurred following the 1934 earthquake where subsidence of 38cm was observed
near to Kosmo, Utah.
Sedimentary basin subsidence
The mechanisms of sedimentary basin subsidence have been reviewed by Bott (1976) and
he points out that such basins occur in various tectonic settings in relation to the proximity of
plate boundaries. The two main types of basin subsidence encountered within plate interiors
are described by Bott as broad regional subsidence dissociated from obvious faulting and
narrow graben-type basins. The causation of subsidence on such major scales has been
attributed to three main factors:
1. gravity loading by sediments and water producing flexure of the earth's crust;
2. thermal events inducing raising the temperature of crustal rocks producing
consequential uplift by way of thermal expansion and later followed by erosion and
subsidence due to subsequent cooling; and
3. deformational behaviour of the continental crust in relation to mainly tensional
stresses.
4
The factors listed here are largely hypothetical and are still the subject of considerable debate
amongst geologists. Subsidence of sedimentary basins is discussed by Bott (1976) and for
further information the reader is advised to consult Tectonophysics, 36 (1976).
Figure 2 illustrates the principal features of subsidence arising from sedimentary basin,
rift valley (graben) fault structures and plate boundary interaction mechanisms.
Dolines, swallow-holes, sink-holes and crown-holes
The occurrence of depressions at the surface overlying limestone country are referred to
by four common terms. Dolines refer to simple closed depressions in karst (rough limestone
country with water drainage through fractures, fissures, joints and other cavities giving rise to
potential widening by solution of limestone due to chemical weathering) which have also
manifested themselves as a natural surface subsidence phenomenon. The term 'doline* as is
used by geomorphologists is all embracing and includes swallow-holes, sink-holes* and
crown-holes.
A swallow-hole refers to a fissure system in limestone which intercepts the surface, in
some cases as a well-defined open void and in others as a bottle-necked opening or simply as a
widened fissure, and where such holes have free ingress and egress for running water.
A sink-hole in connection with natural subsidence in limestone country is another term
for swallow-hole, namely a subsidence hole down which water drains away naturally.
Swallow-holes usually refer to those holes where water continuously, or intermittently, flows
into and through such structures; sink-holes commonly include those structures which now
appear dry but have drainage potential.
Crown-holes refer to the natural phenomenon of a localised subsidence depression
caused by progressive upward collapse from a subterranean cavity.
Holmes (1965) in his book 'Principles of Physical Geology* p.422 associates swallow-
holes with sink-holes in connection with solution of limestone by the action of water giving
rise to funnel-shaped holes at the surface; the process loosens locally the jointed block
structure producing enlargement of such voids or drainage paths. He draws attention to the
well-known swallow-hole of Ingleborough namely Gaping Ghyll whose shaft has a depth of
111m which connects with a chamber of 146m length and 33m height; the water traverses an
underground labyrinth of flow paths to emerge several kilometres from its surface entry
point. The potential for creating large caverns by solution of limestone is demostrated by the
Carlsbad Cavern of New Mexico where the 'Big Cavern' is reported by Holmes to be almost
1220m long, with a height of 90m and width up to 180m.
Subsidence arising from development of subterranean voids
The occurrence of sink-holes and crown-holes in limestone country is probably the most
common form of natural subsidence. This can be a frequent occurrence where carbonate
rocks, rock salt and gypsum deposits lie relatively close to the surface. The formation of
•The term sink-hole has a broader meaning in connection with mining subsidence, and refers to the
appearance of a sharply defined subsidence funnel-shaped depression or shaft-like hole at the surface which may
or may not have free drainage potential owing to possible plugging of its collapse chimney by clay puddling
action, and consequently embraces the meaning of crown-holes also.
5
Successive periods of major
sedimentation generating
increased loading.
Compaction
of sediments
and driving ,
Increasing out of balance forces due to
out
major sedimentation causing uplift
interstitial
tendency of adjacent land mass.
water causing
subsidence.
(a) Subsidence of sedimentation basin
t
Subsidence due to combination of
removal of side support and fault
structure.
(b) Faulting associated with rift valley (graben) and lateral shift earth movement producing subsidence.
Original position
(c) Plate tectonics producing earth crustal movements with plate tilting and resulting land mass uplift and
subsidence.
Figure 2 Principal features of natural subsidence arising from major earth movements
