State-of-the-art in shotcreting (in German and English)

153A 855126 Full pneumatic backfilling of a blind shaft with drilling and shotfiring (in German and English) Zimmer, H Gluckauf VI21, N2, 24 Jan 1985, P120-124 (german), P46-47 (english) A large blind shaft at the Osterfeld colliery, Germany, was constructed with a ring lining and backfilling. Using a modification of a proven concrete spraying machine and a high pressure nozzle for wetting at the discharge of the supply line, it was possible to place the fine, dry material at the bottom of the 520m shaft with good compaction of the backfill material. 855127 State-of-the-art in shotcreting (In German and English) Feistkorn, E Gluckauf V121. N2, 24 Jan 1985, P126-133 (german), P48-51 (english) The history of shotcreting is briefly reviewed. The present state of the art is illustrated by current spraying methods and equipment, while other sections cover special applications of shotcrete: bolt-shotcrete combinations, fibre shotcrete, consolidation and single shell lining. Finally, factors affecting the quality of shotcrete and ergonomic problems of its application are discussed. 855128 Wet sprayed concrete by the thin flow method (In German and English) Waldeck, R Gluckauf V121, N2, 24 Jan 1985, P134-138 (german), P52-54 (english) Drifts driven by the drill and blast method in the Walsum mine, Germany, were supported by wet sprayed concrete and yielding arches. The concrete lining consisted of two shells. The outer shell absorbed the high drivage convergences and ensured the load carrying capacity of the rock strata; the inner, applied after decay of drivage convergences, prevented caving in the event of crack formation. Materials properties, application equipment and procedure, arch setting and rock bolting, convergence measurements and operating experience are outlined. 855129 Use of rockbolts and shotcrete for supporting pit bottoms and landings (In German and English) Feckler, W Gluckauf V121, AL~, 24 Jan 1985, P139-144 (german), P55-57 (english) The use of rockbolts and shotcrete, for support in large rooms close to shafts, is widely adopted in Germany in cases where dynamic rock stresses are not expected. An initial layer of shotcrete (consolidation shotcrete) is applied to preserve the load bearing capacity of the rock. Rock bolts are set to provide the load bearing system and in time an inner layer of shotcrete is applied to prevent corrosion of rock bolt tips and reinforcement mesh. The equipment used is described and the economics of this method of support examined. 855130 Use of steel fibre shotcrete to line stonedrifts (In German and English) Masson. C Gluckauf V121, N2. 24 Jan 1985, P145-148 (german), P57-59 f english ) Steel fibre reinforcement improves shotcrete compressive and tensile strength, shrinkage, creep and, in particular, early strength. The use of steel fibre shotcrete as the roadway lining in a German colliery is described. An initial 5cm layer of steel fibre shotcrete was applied and was able to absorb the large drivage

convergences without fissuring. The early bearing capacity was of great importance. After drivage convergence had faded, damage to the first shell was made good and a second, unreinforced shotcrete layer applied. 855131 Borehole lining with colloidal cement (In German and English) Grossekemper, H J; Bussing, R Gluckauf VI21, N2, 24 Jan 1985, P149-152 (german), P59-61 (english) Colloidal cement, prepared by intensive mixing of cement and water in a colloidal mixer, may be successfully used to line boreholes to a diameter of 3.6m. It can be rapidly applied by drawing a centrifugal slinger up the shaft. Colloidal cement linings show considerable cost savings when compared with conventional steel casing methods. 855132 Use of slinger-placed shotcrete to line large borehole walls (In German and English) Gailer, G; Kraus, A Gluekauf V121. N2, 24 Jan 1985. P153-156 (germanj. P61-63 (english) The use of a centrifugal slinger to apply a one-coat grout lining in boreholes up to 2.5m diameter is described. The equipment and grout specifications and field testing are outlined. The technique is an economic, time saving alternative to ring supports or casing. 855133 Incidence of coal face width on roof control (In German) Everling, G Gluckauf-forschungsh V46, N1, Feb 1985, P5-12 The relationship of coal face width (necessary for ease of winning and conveying, and ventilation) and the strength and yield points of supports is examined. Both strong roof and fractured roof conditions are considered. 855134 Strata loading of mine roadway supports Whittaker, P E Min Sci Techn V2, N1, Dec 1984, P45-56 Steel arch supports and rectangular sets at depths of 350-780m in coal mines'were instrumented to investigate the general pattern of strata loading pressure, especially development, magnitude and distribution of rock pressure, under extreme and average conditions. Results indicate that the designer may work to values of 5 and 10 tonnes per sq m as average and extreme loading. However, the variability of results indicates that steel supports must be selected with due consideration of geological and mining conditions for each specific case. 855135 Vicious circle of shotcreting technology Wallis, S Tuna Tuaalg 1/17, N4, April 1985. P27-29 The support requirements necessary when using the New Austrian Tunnelling Method are considered, with particular reference to shotcrete. Shotcreting equipment and the specific advantages and disadvantages of the wet and dry application techniques are discussed.