The HTPF and the integrated stress determination methods

IN SITU STRESS:MEASUREMENT a substitute for detailed analysis of each slope. SMR classification is a development of the Bieniawski 'Rock Mass Rating' (R.MR) system though application to slopes has not been possible to date. The SMR system provides adjustment factors, field guidelines and recommendations on support methods which allow a systematic use of geomechanical classification for slopes. -from Author

944163 Regional Rock Quality Designation (RRQD) of the west central A r a b i a n S h i e l d B . H . Sadagah & M. Y. H . T . Qari, Bulletin - Association of Engineering Geologists, 30(4), 1993, pp 455-467. Engineering and hydrogeological behaviors of rock masses ate intimately related to the intensity, extension and oftentation of discontinuities hosted by the rock. Qualitative descriptions of such discontinuities provides general base information about any type of engineering structure such as dams, highways, pressure tunnels, airports, etc. However, more significantly, their quantitative descriptions are of prime importance especially concerning design variables. One of the most used indices in this regard is the Rock Quality Designation (RQD). So far in the literature only one-dimensional assessments of RQD are available along scanlines such as tunnel axis or along highway rock cuttings. This paper extends the concept of RQD into two dimensions which helps to assess the rock quality on a regional basis. -from Authors

IN SITU STRESS

Causes and nature of in situ stress 944164 A theory for in situ stresses in isotropic and transversely isotropic rock P . R . Sheorey, International Journal of Rock Mechanics & Mining Sciences, 31(1), 1994, pp 23-34. An elasto-static thermal stress model of the earth is presented for estimating crustal stresses considering the variation of elastic constants, density and thermal expansion coefficient through the crust and mantle. The stresses obtained from the model axe shown to be an average fit to stress measurement data. The factor responsible for causing higher values of the horizontal-to-vertical stress ratio k nearer to the surface is shown to be the earth's curvature. The model and its one variation which considers transverse isotropy indicate that the horizontal stress depends on the elastic modulus measured in the horizontal direction. An equation i s p r o p o s e d for obtaining the horizontal stress in soft, j o i n t e d o r generaLly weaker formations when stress measurement is carried out in competent rocks at the same location. -from Author 944165 Stresses in anisotropic rock mass with irregular t o p o g r a p h y E. Pan & B. Amadei, Journal of Engineering Mechanics ASCE, 120(1), 1994, pp 97-119. Presents a new analytical method for determining the state of stress in a homogeneous, general anisotropic, and elastic half-space limited by an irregular and smooth outer boundary. As an illustrative example, it is shown how the proposed method can be used to determine the state of stress in long isolated and symmetric ridges and valleys in orthotropic or transversely isotropic rock masses. It is found that the magnitude of the stresses is of the order of the characteristic stress pgb, where p is the rock density, g is the gravitational acceleration, and b is the height of the ridge or depth of the valley. -from Authors 944166 Geometry and state of stress of the subducted Nazca Plate beneath central Chile and Argentina: evidence from teleseismic data M. Araujo & G. Suarez, Geophysical Journal International, 116(2), 1994, pp 283-303. Thirty new focal mechanisms of intermediate-depth earthquakes in the South American subduction zone were determined in the region between 21" and 33"S. The focal mechanisms and depths of earthcLuakes with magnitudes greater than 5.7 (mb~were constrained using a body-wave modelling method. The hypocentral depths of the other

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earthquakes, with 5.3 < m s < 5.7, were determined by identifying the arrival time o f the depth phases pP and sP on sexsmograms from several teleseismic stations. These refined focal depths were used to draw detailed isodepth contours of the subducted Nazca plate. The geometry of the subducted slab is discussed. -from Authors 944167 Rock stress in the Fennoscandian Shield O. Stephansson, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 445-459. The in situ stress in the Earths crust prior to an excavation is an important parameter needed to design safe mines and underground excavations. A brief history of rock stress measurements in Sweden, Norway and Finland is given. The Fennoscandian rock stress database (FRSDB) is detailed and estimation of deep stress is given in an example from the Siljan region. The chapter is concluded by placing Fennoscandia in the context of the European- and World-stress map. -after Author

Measurement of in situ stress 944168 Stress measurements in high-stress zones using the modified doorstopper technique R. Corthesy, D. E. Gill, M. H. Leite & P. M. Thompson, Canadian Geotechnical Journal, 30(6), 1993, pp 991-1002. Of the existing in situ stress-measurement techniques, the doorstopper is particularly suited for use in highly stressed zones where core discing may occur. The paper presents stress-measurement results obtained with the modified doorstopper technique in highly stressed granite, at the Underground Research Laboratory (URL) of Atomic Energy of Canada Limited. A brief description of the modified doorsto~1~.r technique and of a stress-calculation model that includes the nonlinear anisotropic behaviour found in highly stressed rocks is made. -from Authors 944169 A soil stress t r a n s d u c e r for measuring in situ soil stresses H . D . Harris & D. M. Bakker, Soil & Tillage Research, 29(1), 1994, pp 35-48. A soft stress transducer has been designed to measure norreal stresses in six different directions, and therefore enable the total state of stress in a soil to be defined. Calibration procedures have been developed which show that the transducer will register applied stresses reliably. The transducer is installed in a horizontal hole bored from a pit using a technique which ensures that it is in full contact with the soil. Field testing has shown that in conjunction with a moderately fast data acquisition system it is capable of measuring detailed stress histories under the tyres of moving vehicles. -from Authors 944170 The hydraulic fracturing method of stress measurement: theory a n d practice B . C . Haimson, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 395-412. Hydraulic fracturing (hydrofracturing) is the best method of assessing in situ stress at great depths. After a brief history of the method, the test equipment and set up are described. Data interpretation from the key pressures and fracture characteristics are given. In situ stress derivation from test data is analysed in terms of axial hydraulic fractures in vertical holes, inclined and horizontal fractures in vertical holes and inclined holes. Recent advances and the future of the method conclude the chapter. -R.Gower 944171 The H T P F and the integrated stress determination methods F . H . Comet, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 413-432. The HTPF (hydraulic tests on preexisting fractures) method eliminates the constraints normally Vresent in hydraulic fracturing stress determinations. Application of the method is discussed through practical examples in crystalline and sedimentary rocks, which illustrate that the HTPF method may be viewed as a generalisation of the hydraulic fracturing technique, and often complements the standard test. In practice, a test should never be used in

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SITE INVESTIGATIONS:REMOTE SENSING

isolation, and so the determination of the regional stress field is viewed as an inverse problem, the solution of which is the best fit of all relevant observations. This new approach is the integrated stress determination method and is detailed in full. -after Author 944172 Measuring in situ rock stress by borehole slotting H. F. Bock, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 433-443. Borehole slotting is a relatively new, self-contained technique which allows numerous, closely spaced and relatively cheap stress measurements to be carried out in boreholes without the necessity for ovemorin~. Borehole slotting has been tested in situ in parallel with conventional stress measuring techniques such as overcoring and hydraulic fracturing. Whilst providing results on the in situ stress state with at least comparable accuracy, it was found to have major advantages over the conventional methods with regard to speed of operation, reliability and economy. With both testing services and equipment now being commercially available, it can be expected that borehole slotting will be of increasing importance in the future. -from Author 944173 How do some field tests really work? The case of the NX-borehole j a c k F . E . Heuze, in: Comprehensive rock engineering. 1Ioi. 3, ed J.A. Hudson, (Pergamon), 1993, pp 683-692. Presents a historical perspective of the past trials and tribulations in the development of borehole jack techniques. Then, the positive building blocks axe summarized, and, finally, a procedure is described to analyze borehole jack data. Additional information regarding the practical use of the jack in the field is provided in a document available through the Lawrence Lxvermore National Laboratory. -from Author 944174 Rafurasos technikaval vegzett kozetfeszultseg. meresek M a g y a r o r s z a g o n (In situ stress measurements in H u n g a r y using the overcoring technique) P. Gemer, R. Porjesz & P. Szafian, Magyar Geofizika, 34(3), 1994, pp 134-142. The theoretical background of the overcoring technique, the description of the test sites, the processing of the data and the results of the measurements are discussed. In the overeoring technique the strain relaxation of a 10-20 cm long core sample removed from the in sire stress field is measured with a strain gauge cell. If the elastic properties of the rock are known, the magnimdas and the directions of the in situ stresses can be determined. The results show that the overcoring technique is very sensitive to the properties of the rock, the morphology and the geological structure of the site. However, consxdering these observations, valuable conclusions can be drawn concerning the recent stress field of the Earth's crust and the direction of the two horizontal principal stresses. -from English summary 944175 Measuring rock stress: case examples of rock engineering in J a p a n K. Sugawara & Y. Obara, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 533-552. The hemispherical-ended borehole technicjue, now in common use in Japan is described in detail. It is shown how the complete state of stress in a rock mass can be determined from the strains on the hemispherical bottom surface of a single borehole. The observation equation to be used in ractice, spherical diamond bits to convert the bottom of e borehole into a hemispherical shape, and a spherical strain cell to bond the necessary 16 strain gauges directly to the rock surface are introduced, as well as subsequent monitoring of the chan~es in strain through the overcoring operation by the continuous measurement system. Four case examples of the technique are given, and finally, compiling the results of the initial rock stress measurements,

the near-surface stress field in the Japanese islands is discussed. -from Authors

SITE INVESTIGATION AND FIELD OBSERVATION 944176 U n d e r g r o u n d disposal of radioactive waste C . S . Mogg & B. J. Breen, Mining Engineer, 153(391), 1994, pp 277-283. United Kingdom Nirex Limited (Nixex) is responsible for developing and managing a facility for the safe deep disposal of intermediate (ILW) and some low-level (LLW) radioactive waste. The company is concentrating its efforts on a ~proposed site at Sellalield in Cumbria. Borehole invesugauons are supplemented by seismic surveys, other geophysical sensing and geological mapping, Nirex announced plans in October 1992 to advance geological investigations by means of an underground Rock Characterisation Facility. The facility would give access to depth to around 800 m below Ordnance Datum in the strong, low permeabilit~ basement rocks of the Borrowdale Volcanic Group. Thin paper outlines the approach to repository design development work and outlines the Nirex future programme. -from Authors

Remote sensing and photographic techniques 944177 Modern surveying techniques for mining and civil engineering A. Chrzanowski, in: Comprehensive rock engineering. Vol. 3, ed LA. Hudson, (Pergamon), 1993, pp 773-809. This brief review of modem surve]ling techniques has shown that with the recent technologlcal developments in both geodetic and geotechnical instrumentation one may, at a cost, achieve almost any needed resolution and precision, full automation and practically real-time data processing. The development of space techniques such as GPS has revolutionized the traditional m e t l i ~ used to establish geodetic control networks and has opened new fields of geodetic surveying applications. Some sophisticated methods, particularly for deformation analysis, have been developed within the last few years. They requite, however, a sound undentanding of all the processes involved in the design, execution and postamdysis of the measurements. -from Author 944178 Strain accumulation 1986.1992 across the Reykjanes Peninsula plate boundary, Iceland, determined from GPS measurements E. Sturkell, F. Sigmundsson, P. Einarsson & R. Bilham, Geophysical Research Letters, 21(2), 1994, pp 125-128, Gc~S geodetic observations 1986-1992 spanning the lique plate boundary on the Reykjanes Peninsula, SW eland, show that left-lateral shear strain is accumulating in the area. The principal strain rates are: ¢1 = 0.255 ± 0.055 p ~ t r a J ~ r (extenston) at N121 + 6"E, and ¢~ = -0.I90 + 0.053 ~ t r a m / y r (contraction) at N31 +6"E, The principat axis ot extension is perpendicular to me strike of fractures within volcanic systems on the Peninsula. Continuous aseismic slip of the North American'Eurasian plates below a 5-11 km locking depth on the Peninsula can ex]~lain ~ e observed depth of earthquakes, the width o f the aetonnanon zone determined from recent fissuring and faulting, and the GPS-measurements of strain. -from Authors 944179 Rapid geomorpbological reconnaissance survey for road alignment in west Nepal G. J. Hearn, Bulletin - International Association of Engineering Geology, 48, 1993, pp 59-68. A rapid geomorphological reconnaissance survey of the 112 km Baltadi-Darchula road currently under construction in the Middle Himalaya of West Nepal is described, The first 30 km of the proposed road was under constmct~n when this 5 day survey commenced, to cover both the initial segment as well as an examination of the stability and practicability of the remainder of the 'alignment. A combi-