1. METHODS FOR SUBSIDENCE PREDICTION AND CONTROL
MINE PORTAL TEAM
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2. What is Mine Subsidence
Mine subsidence is the collapse of the ground surface over areas where coal or mineral ores were removed.

3. Modes of Subsidence Trough subsidence Sinkhole subsidence
Source: www. aegweb.org, Retrieved

4. Source : www.dep.state.pa.us, Retrieved 23-08-2011

5. Component of Subsidence
Vertical Displacement
Horizontal displacement
Slope (or tilt)
Horizontal strain
Vertical curvature (or flexure)

6. Source : www.qjegh.lyellcollection.org, Retrieved 22-08-2011

7. Development of Dynamic Subsidence Profiles as the Face Advances
Source : www. dep.state.pa.us, Retrieved

8. Terminology of Subsidence
limit angle or angle of draw
angle of break or angle of fracture
Inflection Point
Critical Subsidence
Subcritical Subsidence
Supercritical Subsidence
Non Effective Width

9. limit angle or angle of draw
Source : Geofacts no. 12, Ohio Department of Natural Resources, 2010

10. Standard Subsidence Curve
Source :

11. Critical Subsidence
Source :

12. Subcritical Subsidence
Source : Retrieved

13. Supercritical Subsidence
Source : Retrieved

14. Subsidence Prediction Methods
Theoretical models
Elastic Theory
Plastic Theory
Stochastic Theory
Influence function method
Profile function method
Empirical Methods
GIS-Based Subsidence Prediction Method

15. THEORETICAL MODELS Elastic Theory
following equation is used in this method-
Zu(x, y) = ultimate subsidence at any point ( x,y ) on the ground surface
b = vertical closure of the opening
D = depth to the top of the opening

16. Elastic Theory
The notation is used to represent an equation of the form:
f (U,V) =f (U2,V2) −f (U2 ,V1) − f (U1 ,V2)
+f (U1 ,V1)
U1 = Xc – w/2 – x
U2= Xc + w/2 – x
V1 = Yc – L/2 – y
V2 = Yc + L/2 – y
where (Xc, Yc) are the coordinates of the center of the underground opening represented by a parallelepiped where L and W are its length and width, respectively

17. Plastic Theory
a = ratio of vertical subsidence to mine closure M = room height H = depth to mine horizon x = distance from the center of subsidence l = opening width Vzm = rate of subsidence & η = kinematic stiffness of the rock body.

18. Stochastic Theory
The stochastic theory is a statistical approach that treats the rock body as a cohesionless medium.
A rock mass that contains numerous and pervasive fractures may behave as a material with zero cohesion,
The stochastic theory states that when a volume of rock is removed (an extraction element), it is replaced by an equal volume of rock lying above. The resultant particle movement at the ground surface is predicted by a bell-shaped probability curve representing the subsidence profile.

19. Influence function method
Use to describe amount of influence exerted at the surface by infinite small elements of the extraction area.
Total subsidence is the sum of the elementary troughs of all extraction elements according to their position.
Advantages-
Not confined to rectangular extraction.
Able to negotiate superposition problems.

20. Subsidence Prediction- Empirical Methods
The relation between maximum subsidence, Non-effective width, depth and height of extraction and other parameters recommended by NIRM is presented below: Longwall method Smax = he*0.6(1+(W/H)/0.754)-12.68) Smax = Maximum subsidence for a given width to depth ratio ‘x’ he = Effective height of extraction (Height of extraction x % of extraction) W = Width of the panel H = Depth of the panel

21. Subsidence Prediction- Empirical Methods
Bord & Pillar Method Smax = he*0.65(1+(w/H)/0.75)-8) Smax = Maximum subsidence for a given width to depth ratio ‘x’ he = Effective height of extraction (Height of extraction x % of extraction) W = Width of the panel, ‘m’ H = Depth of the panel, ‘m’

22. Safe limits of subsidence
Railways lines
Water bodies
Buildings
Aerial ropeway and electric transmission high tension pylons
Roads
No movement permitted Maximum tensile strain is 4.5 mm/m Max. total elongation or compression is 60 mm Strain 3mm/m Slope to the extent that the displacement of the top most point should not be more than one third of the radius of the base No stepping due to subsidence

23. Different Methods for Subsidence Control
Working Mine
Plane Fitting
Trench Around Houses
Tension cable
Hydraulic Sand Stowing
Partial Extraction Method
Non-Effective Width
Chess Board
Goaf Pillar
Wide and Stall
Splitting of Pillar with Stowing
Splitting of Pillar with side bolting
Harmonic mining

24. Different Methods for Subsidence Control
Abandoned Mine
Point Support Method
Gravel Column
Flyash Grout Injection
Fabric Formed Concrete
Areal Backfilling
Pumped Slurry Injection
Flyash Slurry Injection
Pneumatic Flyash Injection

25. PARTIAL EXTRACTION METHODS
Partial extraction methods can be classified in to two groups
Pillars and overburden both are stable
Wide stall method
Pillar splitting method
Pillars are stable whereas overburden may fail
Non-effective width extraction
Chess board method
Goaf pillar method

26. PARTIAL EXTRACTION METHODS
Wide Stall Method
It involves the widening of the galleries from its side or sides.

27. PARTIAL EXTRACTION METHODS
Pillar Splitting Method
Pillars are split and form number of stooks.

28. PARTIAL EXTRACTION METHODS
Chess board method

29. PARTIAL EXTRACTION METHODS
Goaf and pillar method

30. PARTIAL EXTRACTION METHODS
Plan of panel designed by extracting diagonal rows of pillars.

31. HYBRID METHOD OF PARTIAL EXTRACTION
It is a combination of Wide stall method and pillar splitting method.

32. Harmonic Method of Extraction
Extraction of a panel causes tensional and compressive strain at the surface
The working of two seams should be so advanced simultaneously to cancel out the balance of strain, caused by face by the strain induced by another at a different level.
This approach is known as harmonic mining, which however is not simple Because the mine has to be pre-planned and also problems due to interaction between faces in different seams have to be encountered.

33. A Case Study: An abandoned mine in Seita Reservoir area, KitaKyushu, JAPAN
Source : Synthesis Subsidence Prediction Method, Institute of Environmental Systems, Kyushu University, Fukuoka, Japan

34. Seita Reservoir area
200 m
1200 m
3D view of spatial distribution of coal seam layers with DEM around Seita reservoir area

35. observation points P4 P3 P5 P2 P6 P1 P7 P8
Subsidence contour up to 1997 with
observation points

36. Seam Layer 1
Seam Layer 2
Seam Layer 3
Seam Layer 4

37. Comparison of calculated and measured subsidence value

38. subsidence value simulation

39. Maximum subsidence = 3270 mm
3D view of final subsidence model and underground mining layers in GI

40. References
Nelson, Paul E (2010) “Subsidence Modelling Techniques – An Overview of Graphical, Analytical and Numerical Method” , p
Esaki T, Djamaluddin I, Mitani Y and Zhou G (1997) “Synthesis Subsidence Prediction Method due to Underground Mining integrated with GIS”.
Retrieved
, Retrieved