Field stress measurements in jointed rock

~OOA including determination of depth of fractured zones, permeability and leakage studies, and examination of feasibility of fluid injection to induce fault slip. 925209 Field stress measurements in jointed rock Obara, Y; Sugawara, K Proc International Conference on z~lechanics of Jointed and Faulted Rock, Vienna, 18-20 April 1990 P827-834. Publ Rotterdam: A A Balkema, 1990 The hemispherical ended borehole technique of Sugawara (1986) allows the stress tensor to be determined from a measurement in a single borehole. Measurements in jointed rocks close to an active fault and in a coal mine are presented. The characteristics of the stress field and influence of discontinuities are analysed by comparing these results with those of numerical simulation. Normal and shear stresses on the discontinuities can be estimated from the stress measurements using the stress transformation law. The strength criterion for the discontinuity is discussed. 925210 Selection of equipment for hydrofracturing tests in permeable rocks Marulanda, A; Gutierrez, R; Vallejo, H Proc International Conference on Mechanics of Jointed and Faulted Rock, Vienna, 18-20 April 1990 P667-672. Publ Rotterdam: A A Balkema, 1990 Based on a series of hydrofracturing field tests, difficulties that arise during tests are discussed. The application of simple, mobile, robust, reliable, and inexpensive equipment is shown to be a requisite. Geotechnical aspects for permeable and fractured rock masses or impermeable and low-fractured rock masses that may be encountered during the stress measurement exercise are presented.

Site Investigation and Field Observation Remote sensing and photographic techniques 925211 Geological stereo mapping of geologic structures with SPOT satellite data Berger, Z; Williams, T H L; Anderson, D W Bull Am Assoc Petrol Geol V76, NI, Jan 1992, PIOI-120 The SPOT imaging system uses high resolution visible systems in a scanning passive mode, analysing reflected energy from the earth surface for wavelength and intensity. Quality stereo mapping is possible using either hard copy photographs or the more easily manipulated images on a video monitor. It prorides inexpensive global stereo image coverage in digitized form, ideal for exploration purposes, and complements L A N D S A T data. 925212 Groundwater survey methodology in crystalline basement areas; example of the district of Korhogo (Ivory Coast) (In French) Savane, I; Affian, K; Koli Bi, Z; Cougny, G Int Assoc Engng Geol Bull N44, Oct 1991, P79-88 In regions of crystalline basement, the only productive areas will be those intersecting fractured or heavily weathered rock. Some techniques to search for these areas are described. The

initial stage involves examination of aerial photographs to obtain a detailed description of relief and to identify lineaments and drainage paths. Intersections of observed fractures are then further investigated to see if they mark sizable reservoirs.

925213 Digitally processed satellite data as a tool in detecting potential groundwater flow systems Bobba, A G; Bukata, R P; Jerome, J H J Hydrol V131, Nl/4, Feb 1992, P25-62 The regional groundwater flow system concept, based on a vertical section with recharge, transition, and discharge regions, has gained recent support. The use of LANDSAT data as a tool for identifying the potential of groundwater flow system areas is discussed. Digital radiance data have been used to delineate areas of the Big Creek and Big Otter Creek regions of Ontario according to proximity of water table to the surface. Seasonal and environmental factors in gathering and interpreting the data are discussed. The location of groundwater flow systems provides valuable input for hydrological modelling.

925214 Use of the Global Positioning System (GPS) for ground subsidence measurements in western Venezuela oil fields Chrzanowski, A; Chen, Y Q; Leal, J; Murria. J; Poplawski, T Proc 4th International Conference on Land Subsidence, Houston, 12-17 May 1991 P419-431. Publ IAHS Press." Wallingford, 1991 An area of about 1000 sq km along the eastern coast of Lake Maracaibo has been subject to subsidence caused by oil extraction. Three subsidence basins formed. Maximum subsidence since 1929 is about 5m, and current maximum rates are 0.2m/yr. A 1600 benchmark levelling network is installed and has been monitored every two years. This is slow and expensive. In 1986 a scheme combining terrestial and GPS measurement was implemented, with expected savings of 30%. Full implementation of GPS was achieved in 1990. Accuracy will increase as more GPS satellites become available. A mathematical model and software for subsidence analysis have been developed.

925215 Positional system GPS for subsidence control of the terminal reach of the Po river Gambardella, F; Bortolotto, S; Zambon, M Proc 4th International Conference on Land Subsidence, Houston, 12-17 May 1991 P433-441. Publ IAHS Press: Wallingford, 1991 The present delta of the Po river results from hydraulic engineering in 1604. Subsidence of up to 3m occurred in the 1960s due to removal of groundwater containing natural gas. The traditional benchmark levelling system for monitoring is slow and expensive, and the possibility of geodetic positioning of existing benchmarks by GPS has been investigated. Precision, speed, and economics are described. The accumulation of systematic errors possible with conventional methods does not occur with the use of GPS.

© 1992 Pergamon Press Ltd. Reproduction not permitted