2017-03-29_REPORT - C1982056

• Permit No: C1982056
• IBM Index Class Name: Report
• Doc Date: 3/29/2017
• Doc Name: Quarterly Subsidence Monitoring Report
• From: Twentymile Coal, LLC
• To: DRMS
• Permit Index Doc Type: Subsidence Report
• Email Name: TNL
• Email Name: DIH
• Media Type: D
• Archive: No

Panel
Ribside
I
I
I
I
I
I
I
I
I
I
Vertical Stress
Re -distribution
/ I
Yield "Rigid" or
Pillar Abutment
Pillar
(a) After Development
Panel Panel
Strain
+E Curve Extension (Compression
E Subsidence \ �♦
Curve I', I ♦♦
'♦ so
Zone of Vertical Extension
I (bed separation) I
I I
I
IL too
O2 Zone of Bed Separation
I 1Q Zone of Caving I /
2
O 3-sm
T777= FT
Pillar Yield and Floor
Punching Floor Heave Zone of Incomplete
(load transfer to cure) Convergence
Figure 1
Generalized Vertical Stress Change and
Displacement during Longwall Mining
(Derived using information from Mark, 1992,
Bienawski, 1992, Shadbolt, 1977)
(b) After Longwall Extraction
1. Empirical Methods: Graphical Methods, Profile
Functions, Influence Functions and Zone Area
Methods.
2. Analytical Methods: Mechanistic Models, Finite
Element, Boundary Element, and Hybrids
(c) Zones of Fracturing
(Singh, 1986)
EXPLANATION:
rn = Extracted seam thickness
s = Subsidence
ov = In-situ vertical stress
6p = Side abutment stress
+E = Extension
-E =Compression
Table 1 provides a summary of the relative
capability of each method with regard to the
prediction of subsidence, displacement, and strain.
The interested reader is referred to the citations for a
detailed description of each method.
Table 1. Relative capability of the methods to predict subsidence, displacement and strain.
PREDICTION METHOD METHOD OF PREDICTING
(REFERENCE) Subsidence (S) Displacement Strain (E)
Graphical Method
Graphical based on w/h &
Not predicted, however, Figure
Maximum strains predicted
(Ref: NCB, 1975)
tabulated profile data
64 provides a monogram for
using Smax/h multiplier. Strain
calculating the change in length
profile predicted using tabulated
of influence.
of a subsided surface structure.
& graphical data.
Profile Functions
Uses mathematical equation
Calculated from predicted
Calculated from predicted
(Karmis, 1992; Singh, 1992)
based on empirical data.
slope.
curvature
Zone Area Method
Subsidence factor calculated by
Calculated from predicted Calculated from predicted
(Karmic & Hacocks, 1983;
superposition of the proportional
slope. curvature.
Marr, 1975)
extraction of a finite number of
concentric rings forming the area
of influence.
Influence Functions
Profiles constructed by
Calculated from predicted Calculated from predicted
(VPI, 1987; Salamon, 1992)
integrating the influence function
slope. curvature.
(see eq. 3-7 to 3-11)
Mechanistic Models Subsidence predicted based on Not addressed. Not addressed.
composite beam deflections.
Finite & Boundary Element Subsidence & related parameters Produced as model output. Computed from modeled
Models simulated directly through displacements.
(Su, 1992; Summers, 1990) analysis of the rock mass
response to underminine.