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Evolution of the plastic zone near a microfracture: a numerical simulation and its implications on in situ stress measurement
IN SITU STRESSMEASUREMENT 956154 ReiiabRity assessment of c4Mrifoge soil test resdts R. Popescu & J. H. Prevost, Soil Dynamics & Earthquake Engineering, 14(2), 1995, pp 93-101. A methodology to assess the reliability of the mean value obtained from a series of soil test results is employed to assess the quality of the results obtained from laboratory soil tests and centrifuge experiments performed within the framework of the VELACS Project. (Authors) 956155 Study on dynamic deformation and strength chracteristics of Lwchean loess (in Cwnese) Wu Zhihui, Xie Dingyi & Yu Xiongfei, Shuili Xuebao/ Journal of Hydraulic Engineering, 12, 1994, pp 67-71. The dynamic deformation and strength characteristics of an intact loess specimen is investigated in this paper. A series of results dealing with the dynamic constitutive relation the dynamic strength and dynamic deformation are obtained. (e@sh summary) 956156 Dynaudc damage constitutive model of concrete in oniaxial tension and ampradon (in CM-) Li Qingbin, Zhang Chuhan & Wang Guanglun, Shuili Xueba~/J~urMI of Hydraulic Engineering, 12, 1994, pp SS60. Based on the static damage constitutive model, two hypotheses have been proposed by the authors and a dynamic damage constitutive model of concrete under uniaxial tension or compression has been deduced. This model was verified by experimental results. (English summary)
Identification and classification 956157 Bi-lineu models for simultaneoas estimation of a formation presmre and litbological characteristics in interbedded samdsamdshles S. Katz, G. V. Chilingar, F. Aminzadeh, A. Gurevich & L. Rhilyuk, Journal of Petroleum Science & Engineering, 12(l), 1994, pp 37-48. A new method for analysis of lithology variations in muhilayered geologkal formations and suppression of lithological components in formation pressure indicators is described. The key element of the methodology is the suggestion that several curves indicating variations with depth in formation piessureandinlithologymaybepresentedasasumof~ basic components: 1) smooth components, slowly changing with depth; 2) a fast-changing component, and 3) random components, mutually uncorrelated at different curves. The models for formation pressure and lithological indicators are built as bi-linear functions of variables from those two groups. An example of this methodology is a joint use of information on drilling rate taken in the form of d,exponent and information on the lithology taken in the form of the shale content in interbedded sands and shales. (from Authors) 956158 Rmk evaluation of the Neyveki lignite deposit on the basis of retktamce parameter A. Singh & B. D. Singh, Journal - Geological Society of India, 44(4), 1994, pp 391-397. The Neyveti fdd is well known for Tertiary lignite deposits in India. The reflectance of organic constituents (huminite mace&$ has been measured to find out organic maturation level (rank) of the main lignite seam lying either at same time he1 or at different time levels in space. The deposits are of
sub- bituminous C stage (ASTM) with the mean reflectance (Ro max. in oil) range from 0.34 to 0.42% (average 0.39%). Evidence from rank study indicates that the quality of lignite deteriorates towards the southern part of the field. (Authors) 956159 Variation hr refleetanee 8ruI dmmBtry of v#inite ad ritrinite preenrso m in a series of Tertiary eoaIa, Aretic Canada M. Mastalerz & R. M. Bustin, Organic Geochemictry, 22(6), 1994, pp 921-933. A continuous 3308 m thick sequence of coal measures from tbe Eureka Sound Group, Foshiem Peninsula, Ellesmere Island has been studied in order to document changes in chemistry of coals from 0.17 to 0.56% vitrinite retlectance (&) as well as to determine ditRerences in chemistry between collinite and telinite and their precurso rmacerals.FTIR spectra show that, in coals with R.,0.2%, and the lignin component is more aromatic in colbnite than in telinite. The di&remm between telinite and coilinite are attributed to di&rences in chemistry of the primary plant material. (from Authors)
IN SITU STRESS Measurement of in situ stress 956160 Strain me ssoremenQ with the borebole dotter A. Becker & D. Werner, Terru Nova, 6(6), 1994, pp 608-617. Inthepast,thedoorstoppermethodhasbeenusedsuazssfully for de&mining in situ tectonic stmsses. Here an example is given regarding the application of the borehole slotter in the domain of tectonic stress determhmtions, which is an innovative strain relief technique without ovemoring. Data are presented that test the reliability of the strain measumments by the borehole slotter under well-known stress conditions, that indicate the reproducibility of borehole slotter strain data compared with those from doorstopper measurements, and that demonstrate the utility of the borehole slotter even for the &m&nation of weak tectonic strains. In northern Switzerland the borehok slotter was used in a horizontal borehole under lithostatic loading conditions only, in a rock slope area with very heterogeneous stress conditions, and in a vertical borehole where tectonic stress should be dominant. The results show that the borehole slotter is a reliable tezhnique, which allows precise detennination of in situ strains. (from Authors) 956161 Evolution of the plastic mne near a microfractux a mnerical simdation and its haplicatioas on in situ strew measurement Yarlong Wang, S S. Shen & Haibing Cheng, CaMdian Geotechnical Journal, 31(S), 1994, pp 779-787. The instantaneous shut-in pressure has been used to estimate the far-tield in situ minimum principal stress during microfracture testing. A plastic zone can be induced near the fracture. Because of the early plastic (irreversible) deformation induced near the fracture, the irreversible deformation nearthefracturesurfacereducesthefracturepressureand generates a discrepancy between the far&Id minimum stress and the fracture closure pressure, which has been identified as the minimum in situ stress in the past. A finite&ment numericrd model is used to investigate this di@epancy due to the plastic deformation near a fracture. It is conchtded that a plastic zone can be generated near a hydraulic fracture in poorly consolidated media. (from Authors)
Identification and classification 956157 Bi-lineu models for simultaneoas estimation of a formation presmre and litbological characteristics in interbedded samdsamdshles S. Katz, G. V. Chilingar, F. Aminzadeh, A. Gurevich & L. Rhilyuk, Journal of Petroleum Science & Engineering, 12(l), 1994, pp 37-48. A new method for analysis of lithology variations in muhilayered geologkal formations and suppression of lithological components in formation pressure indicators is described. The key element of the methodology is the suggestion that several curves indicating variations with depth in formation piessureandinlithologymaybepresentedasasumof~ basic components: 1) smooth components, slowly changing with depth; 2) a fast-changing component, and 3) random components, mutually uncorrelated at different curves. The models for formation pressure and lithological indicators are built as bi-linear functions of variables from those two groups. An example of this methodology is a joint use of information on drilling rate taken in the form of d,exponent and information on the lithology taken in the form of the shale content in interbedded sands and shales. (from Authors) 956158 Rmk evaluation of the Neyveki lignite deposit on the basis of retktamce parameter A. Singh & B. D. Singh, Journal - Geological Society of India, 44(4), 1994, pp 391-397. The Neyveti fdd is well known for Tertiary lignite deposits in India. The reflectance of organic constituents (huminite mace&$ has been measured to find out organic maturation level (rank) of the main lignite seam lying either at same time he1 or at different time levels in space. The deposits are of
sub- bituminous C stage (ASTM) with the mean reflectance (Ro max. in oil) range from 0.34 to 0.42% (average 0.39%). Evidence from rank study indicates that the quality of lignite deteriorates towards the southern part of the field. (Authors) 956159 Variation hr refleetanee 8ruI dmmBtry of v#inite ad ritrinite preenrso m in a series of Tertiary eoaIa, Aretic Canada M. Mastalerz & R. M. Bustin, Organic Geochemictry, 22(6), 1994, pp 921-933. A continuous 3308 m thick sequence of coal measures from tbe Eureka Sound Group, Foshiem Peninsula, Ellesmere Island has been studied in order to document changes in chemistry of coals from 0.17 to 0.56% vitrinite retlectance (&) as well as to determine ditRerences in chemistry between collinite and telinite and their precurso rmacerals.FTIR spectra show that, in coals with R.,
IN SITU STRESS Measurement of in situ stress 956160 Strain me ssoremenQ with the borebole dotter A. Becker & D. Werner, Terru Nova, 6(6), 1994, pp 608-617. Inthepast,thedoorstoppermethodhasbeenusedsuazssfully for de&mining in situ tectonic stmsses. Here an example is given regarding the application of the borehole slotter in the domain of tectonic stress determhmtions, which is an innovative strain relief technique without ovemoring. Data are presented that test the reliability of the strain measumments by the borehole slotter under well-known stress conditions, that indicate the reproducibility of borehole slotter strain data compared with those from doorstopper measurements, and that demonstrate the utility of the borehole slotter even for the &m&nation of weak tectonic strains. In northern Switzerland the borehok slotter was used in a horizontal borehole under lithostatic loading conditions only, in a rock slope area with very heterogeneous stress conditions, and in a vertical borehole where tectonic stress should be dominant. The results show that the borehole slotter is a reliable tezhnique, which allows precise detennination of in situ strains. (from Authors) 956161 Evolution of the plastic mne near a microfractux a mnerical simdation and its haplicatioas on in situ strew measurement Yarlong Wang, S S. Shen & Haibing Cheng, CaMdian Geotechnical Journal, 31(S), 1994, pp 779-787. The instantaneous shut-in pressure has been used to estimate the far-tield in situ minimum principal stress during microfracture testing. A plastic zone can be induced near the fracture. Because of the early plastic (irreversible) deformation induced near the fracture, the irreversible deformation nearthefracturesurfacereducesthefracturepressureand generates a discrepancy between the far&Id minimum stress and the fracture closure pressure, which has been identified as the minimum in situ stress in the past. A finite&ment numericrd model is used to investigate this di@epancy due to the plastic deformation near a fracture. It is conchtded that a plastic zone can be generated near a hydraulic fracture in poorly consolidated media. (from Authors)