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Using a Computer Spreadsheet to Characterize Rock Masses Prior to Subsidence Prediction and Numerical Analysis.

PB96139241

Publication Date	1996
Personal Author	O'Connor, K. M.; Siekmeier, J. A.; Powell, L. R.
Page Count	75
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 hypthesis 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	Ground subsidence Underground mining Rock mechanics Deformation Coal mines Overburden Mechanical properties Site characterization Discontinuities Geologic structures Geologic strata Deflection Stiffness Computer applications Numerical analysis Time domain
Source Agency	Bureau of Mines
NTIS Subject Category	48A - Mineral Industries 50D - Soil & Rock Mechanics
Corporate Authors	Bureau of Mines, Minneapolis, MN. Twin Cities Research Center.
Document Type	Technical Report
Title Note	Rept. of investigations/1996.
NTIS Issue Number	199608

Using a Computer Spreadsheet to Characterize Rock Masses Prior to Subsidence Prediction and Numerical Analysis.

Using a Computer Spreadsheet to Characterize Rock Masses Prior to Subsidence Prediction and Numerical Analysis.
PB96139241

Publication Date	1996
Personal Author	O'Connor, K. M.; Siekmeier, J. A.; Powell, L. R.
Page Count	75
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 hypthesis 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	Ground subsidence Underground mining Rock mechanics Deformation Coal mines Overburden Mechanical properties Site characterization Discontinuities Geologic structures Geologic strata Deflection Stiffness Computer applications Numerical analysis Time domain
Source Agency	Bureau of Mines
NTIS Subject Category	48A - Mineral Industries 50D - Soil & Rock Mechanics
Corporate Authors	Bureau of Mines, Minneapolis, MN. Twin Cities Research Center.
Document Type	Technical Report
Title Note	Rept. of investigations/1996.
NTIS Issue Number	199608