Algiers subway (In French)

386A upthrust fault. Friable mylonitic structures, cataclastic structures, and bedded schist and massive cataclastic structures exist in the rock mass. A parallel adit, 37m from the tunnel centre, was used to provide advance warning of geological problems. Drainage and extensive pre- and post-support were necessary to allow tunnel construction. Penetration rate of 39m/month was achieved through the fault zone.

end of the tunnel and geophysical survey of the alignment. Based on this information, support of fibre shotcrete and bolts was specified. During drill and blast excavation, rock quality appeared much better than first assessed. Using these observations and experience in similar rock, support classification was revised and a less intense bolting pattern adopted.

936423 .Algiers subway (In French) Chermouti, S Proc 7th ISRM International Congress on Rock Mechanics, Aachen, 16-20 September 1991 II2, P1277-1280. Publ Rotterdam: A A Balkema, 1991

936427 Mechanism and evaluation of deformations of tunnels of squeezing ground Kawamoto, T; Aydan, O; Akagi, T; Ito, T Proc 7th I S R M International Congress on Rock Mechanics, Aachen, 16-20 September 1991 V2, P1317-1320. Publ Rotterdam: A A Balkema, 1991

Construction of a 450m long tunnel section of mean radius 5m through gneissic rock with varying degree of alteration is described. Instrumented test galleries were used to evaluate construction methods (machine or blasting) and sequences, convergence, drainage, and support. The method of construction was chosen to minimise the destressing of the altered rock mass. 936424 Methods of geotectonic analysis: the case of the Siaix tunnel, Savoy, France (In French) Deville, E; Masseglia, M; Robert, A; Sirieys, P Proc 7th I S R M International Congress on Rock Mechanics, Aachen, 16-20 September 1991 V2, P1281-1284. Publ Rotterdam: A A Balkema, 1991 The 1.7km long Siaix tunnel runs through rocks with complex geology affected by the Alpine orogeny, primarily limestones and flysh. A comprehensive geological survey was carried out to determine the structure and to quantify potential deformation. Orientation and frequency of fractures, occurrence of faults, and rock type and history were mapped. Three distinct zones of deformation behaviour were distinguished. 936425 Somport tunnel - reconnaissance of rock massif from a nearby tunnel Fuentes, F; Lorenzo, F; Perez, P Proc 7th ISRM International Congress on Rock Mechanics, Aachen, 16-20 September 1991 V2, P1289-1292. Publ Rotterdam: A A Balkema, 1991 The 8.6km Somport road tunnel joining France and Spain through the Pyrenees passes through highly deformed and folded rock. At the site characterisation stage advantage was taken of a disused rail tunnel, noticeably parallel to and close to the planned alignment. This allowed detailed study of the hydrogeology, thickness and features of the decompressed rock, and lithological boundaries and fractured areas, plus in situ measurement of deformation moduli. The range of mechanical and geophysical methods used is described. 936426 Engineering geology of the Nuoija railway tunnel, Swedish Lapland Hansen, L Proe 7th ISRM International Congress on Rock Mechanics, Aachen, 16-20 September 1991 V2, P1301-1303. Publ Rotterdam: A A Balkema, 1991 The Nuoija tunnel runs through the upper nappes of the Scandinavian Caledonides. Pre-investigation for the 1100m long rock section included 2 exploratory holes drilled from each

Examination of case studies and laboratory testing have been used to study the influence of the nature of the surrounding medium, geology, stress state, seepage, support system, and advance rate on the phenomenon of tunnel failure in squeezing ground. A method to predict squeezing potential is proposed and a non-linear rheological model developed to predict deformation behaviour of the surrounding rock medium. The model is evaluated for the case of a tunnel in highly squeezing ground.

936428

Some experiences on tunnelling in swelling materials Vrkljan, I; Ortolan, Z; Zenko, T; Redzepagic, M Proc 7th I S R M International Congress on Rock Mechanics, Aachen, 16-20 September 1991 V2, P1381-1386. Publ Rotterdam: A .4 Balkema, 1991 The complexity of tunnelling in swelling rocks is illustrated with reference to 2 tunnels in Algeria. The rocks involved correspond to calcareous silty clays to silty marls. Laboratory characterisation of the rocks according to ISRM suggested methods was carried out. In the first tunnel, swelling predicted on the basis of laboratory testing did not occur. In the second, floor heave occurred by a different method from that expected. These experiences demonstrate the near impossibility of reproducing the natural conditions for swelling rocks in the laboratory.

Stresses around underground openings See also: 936302

936429 Analytical solutions for transient thermoclastic stress fields around a borehole during fluid injection into permeable media Hojka, K; Dusseault, M B; Bogobowicz, A D Can Pet Techaol V32, N4, April 1993, P49-57 An approximate analytical transient time solution is presented for the temperature and stress field around a circular borehole during constant rate injection of a hot or a cold fluid into a permeable porous medium. Changes in tangential stress and implications to borehole stability and induced fracturing are examined. The transient temperature field is solved separately for the fluid and the rock. Transient time pressure distribution is calculated using the Theis equation. Stresses are calculated taking into account poroelastic and thermoelastic response of the rock.

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