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Hydrofracturing stress measurements in fractured rock. A laboratory study
87A
Identification and classification 902180 Simple geotechnical classification of molassic formations (In French) Coumantakis, J Int Assoc Engng Geol Bull N39, April 1989, P87-90 A classification system for molassic formations is proposed, based on experiences in Greece, mainly from road excavations. The classification is related to slope stability and excavation conditions, and considers lithology, microstructure, and physical properties of the rock, and the relation between bedding directions and axis of the excavation.
In Situ Stress See: 902472
Causes and nature of in situ stress See: 902436
induced microseismic activities were the techniques used. Results of HTPF are consistent with previously available data. Inversions of all focal mechanisms could not be achieved because of non-convergence of the iterative method used. It was successful for 14 closely spaced events, but results did not agree with those of HTPF. This is attributed to stress perturbations caused by fluid injection.
902184 Methods to determine pillar stress distribution and its effect on stability Conover, D P; Haramy, K Y; Hanna, K Rock Mechanics as a Guide Joe EO~cient Utilization of Natural Resources: Proc 30th U.S. Symposium, Morgantown, 19-22 June 1989 P419-424. Publ Rotterdam: A A Balkema, 1989 Three room and pillar coal mines were instrumented. Borehole pressure cells were installed to determine vertical stress distributions in pillars at various stages of mine development, using methods developed by the USBM. Measured stresses are compared to theoretical distributions. Pressure cell data are seen to be useful for qualitative evaluation of stresses and stress development. Calculated values are found to be sensitive to coal properties and initial pressure setting of the cells.
Measurement of in situ stress See also: 902445 902181 In situ stress determination by hydraulic fracturing - a method employing an artificial notch Hayashi, K; lto, T; Abe, H int J Rock Meek Min Sci V26, N3/4, July 1989, P197-202 A new in situ stress measurement technique is proposed which overcomes requirements of multiple wellbores or large numbers of data for conventional methods. An artificial notch is created at the wellbore surface. Analysis for crack initiation, crack curving and stress distribution near the notch is presented. The method is suitable for the general case where principal stress axes are unknown. It has been applied to a geothermal field in Japan and results show the least compressive stress is neither vertical nor in the horizontal plane, contrary to conventional thinking. 902182 In situ stress measurements by the hydraulic fracturing method at Imaichi pumped storage power plant, Tochigi, Japan Matsunaga, I; Kuriyagawa, M; Sasaki, S lnt J Rock Mech Min Sci V26, N3/4. July 1989, P203-209 Hydraulic fracturing data from three boreholes were analysed to determine the 3D stress field. Acoustic emission was monitored during fracturing for fracture mapping and source mechanism analysis, and borehole television observations used to identify the fractures. Hydraulic fracturing results give comparable data to AE and BTV observations. 902183 Stress determination from hydraulic test data and focal mechanisms of induced seismicity Cornet, F H; Julien, P lnt J Rock Mech Min Sci V26, N3/4, July 1989, P235-248 In situ stress measurements were attempted to a depth of 850m in a granite massif at Le Mayet de Montagne. Hydraulic tests on pre-existing fractures and inversion of focal mechanisms of
902185 Hydrofracturing stress measurements in fractured rock. A laboratory study Cheung, L S; Haimson, B C Rock Mechanics as a Guide for Efficient Utilization of Natural Resources: Proc 30th U.S. Symposium, Morgantown, 19-22 June 1989 P427-434. Publ Rotterdam: A A Balkema, 1989 Laboratory hydraulic fracturing stress measurements were made using a vertically fractured Niagara dolomite under true triaxial stress and at different pre-existing fracture orientations. The ability to induce new hydraulic fractures perpendicular to minimum horizontal principal stress depends on applied stress state and existing fracture orientation. It is concluded that when new hydraulic fractures are opened, stress measurement can be made with little influence from preexisting fractures. When existing fractures are opened, shut in pressure give a good approximation of fracture normal stress.
902186 Stress measurements in a burst-prone heterogeneous rock mass using a novel miniature hydraulic fracturing tool Wold, M B; Enever, J R; Crawford, G R Rock Mechanics as a Guide for Efficient Utilization of Natural Resources: Proc 30th U.S. Symposium, Morgantown, 19-22 June 1989 P435-442. Publ Rotterdam: A A Balkema, 1989 A miniature hydraulic fracturing tool for use in 38mm diameter boreholes has been developed at CSIRO. The tool and its use are described with reference to measurements in the Long Shaft nickel mine. Results are compared with overcoring measurements. The variation in premining stress with location in the heterogeneous rock mass, with stress discontinuities across contacts between rock units, is evident.
© 1990 Pergamon Press pie. Reproduction not permitted
Identification and classification 902180 Simple geotechnical classification of molassic formations (In French) Coumantakis, J Int Assoc Engng Geol Bull N39, April 1989, P87-90 A classification system for molassic formations is proposed, based on experiences in Greece, mainly from road excavations. The classification is related to slope stability and excavation conditions, and considers lithology, microstructure, and physical properties of the rock, and the relation between bedding directions and axis of the excavation.
In Situ Stress See: 902472
Causes and nature of in situ stress See: 902436
induced microseismic activities were the techniques used. Results of HTPF are consistent with previously available data. Inversions of all focal mechanisms could not be achieved because of non-convergence of the iterative method used. It was successful for 14 closely spaced events, but results did not agree with those of HTPF. This is attributed to stress perturbations caused by fluid injection.
902184 Methods to determine pillar stress distribution and its effect on stability Conover, D P; Haramy, K Y; Hanna, K Rock Mechanics as a Guide Joe EO~cient Utilization of Natural Resources: Proc 30th U.S. Symposium, Morgantown, 19-22 June 1989 P419-424. Publ Rotterdam: A A Balkema, 1989 Three room and pillar coal mines were instrumented. Borehole pressure cells were installed to determine vertical stress distributions in pillars at various stages of mine development, using methods developed by the USBM. Measured stresses are compared to theoretical distributions. Pressure cell data are seen to be useful for qualitative evaluation of stresses and stress development. Calculated values are found to be sensitive to coal properties and initial pressure setting of the cells.
Measurement of in situ stress See also: 902445 902181 In situ stress determination by hydraulic fracturing - a method employing an artificial notch Hayashi, K; lto, T; Abe, H int J Rock Meek Min Sci V26, N3/4, July 1989, P197-202 A new in situ stress measurement technique is proposed which overcomes requirements of multiple wellbores or large numbers of data for conventional methods. An artificial notch is created at the wellbore surface. Analysis for crack initiation, crack curving and stress distribution near the notch is presented. The method is suitable for the general case where principal stress axes are unknown. It has been applied to a geothermal field in Japan and results show the least compressive stress is neither vertical nor in the horizontal plane, contrary to conventional thinking. 902182 In situ stress measurements by the hydraulic fracturing method at Imaichi pumped storage power plant, Tochigi, Japan Matsunaga, I; Kuriyagawa, M; Sasaki, S lnt J Rock Mech Min Sci V26, N3/4. July 1989, P203-209 Hydraulic fracturing data from three boreholes were analysed to determine the 3D stress field. Acoustic emission was monitored during fracturing for fracture mapping and source mechanism analysis, and borehole television observations used to identify the fractures. Hydraulic fracturing results give comparable data to AE and BTV observations. 902183 Stress determination from hydraulic test data and focal mechanisms of induced seismicity Cornet, F H; Julien, P lnt J Rock Mech Min Sci V26, N3/4, July 1989, P235-248 In situ stress measurements were attempted to a depth of 850m in a granite massif at Le Mayet de Montagne. Hydraulic tests on pre-existing fractures and inversion of focal mechanisms of
902185 Hydrofracturing stress measurements in fractured rock. A laboratory study Cheung, L S; Haimson, B C Rock Mechanics as a Guide for Efficient Utilization of Natural Resources: Proc 30th U.S. Symposium, Morgantown, 19-22 June 1989 P427-434. Publ Rotterdam: A A Balkema, 1989 Laboratory hydraulic fracturing stress measurements were made using a vertically fractured Niagara dolomite under true triaxial stress and at different pre-existing fracture orientations. The ability to induce new hydraulic fractures perpendicular to minimum horizontal principal stress depends on applied stress state and existing fracture orientation. It is concluded that when new hydraulic fractures are opened, stress measurement can be made with little influence from preexisting fractures. When existing fractures are opened, shut in pressure give a good approximation of fracture normal stress.
902186 Stress measurements in a burst-prone heterogeneous rock mass using a novel miniature hydraulic fracturing tool Wold, M B; Enever, J R; Crawford, G R Rock Mechanics as a Guide for Efficient Utilization of Natural Resources: Proc 30th U.S. Symposium, Morgantown, 19-22 June 1989 P435-442. Publ Rotterdam: A A Balkema, 1989 A miniature hydraulic fracturing tool for use in 38mm diameter boreholes has been developed at CSIRO. The tool and its use are described with reference to measurements in the Long Shaft nickel mine. Results are compared with overcoring measurements. The variation in premining stress with location in the heterogeneous rock mass, with stress discontinuities across contacts between rock units, is evident.
© 1990 Pergamon Press pie. Reproduction not permitted