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Active Control of Underground Stresses through Rock Pressurization.

PB95179610

Publication Date	1995
Personal Author	Vandergrift, T. L.
Page Count	47
Abstract	To significantly increase the stability of underground excavations while exploiting the full advantages of confined rock strength, methods must be developed to actively control the distribution of stresses near the excavation. The U.S. Bureau of Mines study examines theoretical and practical aspects of rock pressurization, an active stress control concept that induces compressive stress in the wall rock through repeated hydraulic fracturing with a settable fluid. Numerical analyses performed by incorporating the rock pressurization concept into a variety of boundary-element models indicate that rock pressurization has the potential to improve underground excavation stability in three ways: (1) by relocating stress concentrations away from the weak opening surface to stronger, confined wall rock; (2) by inducing additional stresses in a biaxial stress field to reduce the difference between the principal stress components near the surface of the opening; and (3) by counteracting the tensile stresses induced in the rock around interally loaded openings.
Keywords	Overburden Rock mechanics Formation pressure Coal mining Caverns Hydraulic fracturing Numerical analysis Mathematical models Excavation Compressive strength
Source Agency	Bureau of Mines
NTIS Subject Category	48A - Mineral Industries
Corporate Authors	Bureau of Mines, Denver, CO. Denver Research Center.
Document Type	Technical Report
Title Note	Rept. of investigations/1995.
NTIS Issue Number	199511

Active Control of Underground Stresses through Rock Pressurization.

Active Control of Underground Stresses through Rock Pressurization.
PB95179610

Publication Date	1995
Personal Author	Vandergrift, T. L.
Page Count	47
Abstract	To significantly increase the stability of underground excavations while exploiting the full advantages of confined rock strength, methods must be developed to actively control the distribution of stresses near the excavation. The U.S. Bureau of Mines study examines theoretical and practical aspects of rock pressurization, an active stress control concept that induces compressive stress in the wall rock through repeated hydraulic fracturing with a settable fluid. Numerical analyses performed by incorporating the rock pressurization concept into a variety of boundary-element models indicate that rock pressurization has the potential to improve underground excavation stability in three ways: (1) by relocating stress concentrations away from the weak opening surface to stronger, confined wall rock; (2) by inducing additional stresses in a biaxial stress field to reduce the difference between the principal stress components near the surface of the opening; and (3) by counteracting the tensile stresses induced in the rock around interally loaded openings.
Keywords	Overburden Rock mechanics Formation pressure Coal mining Caverns Hydraulic fracturing Numerical analysis Mathematical models Excavation Compressive strength
Source Agency	Bureau of Mines
NTIS Subject Category	48A - Mineral Industries
Corporate Authors	Bureau of Mines, Denver, CO. Denver Research Center.
Document Type	Technical Report
Title Note	Rept. of investigations/1995.
NTIS Issue Number	199511