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Using a computer spreadsheet to characterize rock masses prior to subsidence prediction and numerical analysis.

Authors
O'Connor-KM; Siekmeier-JA; Powell-LR
Source
Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, RI 9581, 1996 Jan; :1-75
Link
NIOSHTIC No.
20039373
Abstract
To characterize rock mass overlying high-extraction coal mines, the USBM utilizes a computer spreadsheet program and modified Rock Mass Rating (RMR) system. The spreadsheet calculates an RMR based on a bed's engineering properties determined from core logs and laboratory tests. An in situ deformation modulus and a bending stiffness are computed for each bed. Stiffness-versus-depth plots identify groups of beds with similar stiffness. Large variations in stiffness between adjacent beds are considered significant horizontal discontinuities where slip is likely. Time domain reflectometry (TDR) is used to verify this hypothesis by measuring shear displacement along such discontinuities. A model of the overburden is built by assuming that a near-surface laminated beam exists above a transition zone in which large plastic slip occurs along horizontal discontinuities. Increasingly thicker groups of beds are modeled to determine the most probable beam thickness based on a comparison with measured deflection profiles.
Keywords
Coal-mines; Computer-applications; Deflection; Deformation; Discontinuities; Geologic-strata; Geologic-structures; Ground-subsidence; Mechanical-properties; Numerical-analysis; Overburden; Rock-mechanics; Site-characterization; Stiffness; Time-domain; Underground-mining; Quantitative-analysis
Publication Date
19960101
Document Type
Report of Investigations
Fiscal Year
1996
NTIS Accession No.
PB96-139241
NTIS Price
A04
Identifying No.
RI-9581
NIOSH Division
TCRC
Source Name
Minneapolis, MN: U.S. Department of the Interior, Bureau of Mines, RI 9581
State
MN
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