programs and their theoretical basis, and results from two dif: ferent simulation studies are presented. Coti$arisons are m&e with exact theoretical results.

862158 Large diameter drilling in the UK Pigott, C Min Engr V144, N285, June 1985. P671-676 I_

The equipment and method of blind shaft drilling is described, as is the application of raise drilling for large diameter holes in coal mines. The application of large diameter drilling as an aid to tunnel drivage is presented and suggestions are made for future application of these techniques to improve the efficiency in coal mining and aid the rapid exploitation of resources.

862159 Unified prediction model for percussive and rotary drilling Rabia, H Min Sci Technol V2, N3, June 1985, P207-216

Various equations for predicting the performance of percus- sive and oilwell rotary drilling machines are presented and compared. The use of the concept of specific energy for pre- dicting the performance of drilling machines is critically dis- cussed. It is shown that the best available models are those which use a ratio of available energy to strength terms. A unified prediction model for all types of drilling machines is suggested. Auth.

862160 Experimental assessment of borehole drilling damage in basaltic rocks Fuenkajorn, K; Daemen, J J K In: Rock Mechanics in Prodrrctivity and Protection (Proceedings of the Twenty-Fifth Symposium on Rock Mechanics, Evanston, Illinois, 25-27 June 1984) P774-783. Pub1 New York: AIME, 1984

Ring tension tests, permeability tests and optical microscopy were used to examine the effect of drilling on borehole walls in Pomona basalt and Grande basaltic andesite. Three hole sizes and three drilling techniques (diamond, rotary, percussion) were used. Damage was governed by size of drill bit, drilling technique and rock nature. Weaker rock showed more damage than stronger rock. Coarse (over OSmm grain size) rock showed predominantly intragranular damage whilst fine grained (less than O.Olmm grain size) rock showed intergranu- lar cracks.

Blasting

862161 Knocking down of an unstable cliff in an urban&d site (III French) Schwartzmann, R; Tritsch, J J; Le Bouar, C Rev Fr Geotech N32, 1985, P19-28

In 1981 an overhanging cliff above a road showed signs of instability. Investigation revealed a pre-existing essentially ver- tical fracture and that approximately 30,000 cu m of rock might fall. Demolition by blasting was chosen to make the site safe as reinforcement of the cliff was not possible. Geophones, accelerometers and extensometers were used to monitor the effects of blasting on nearby structures and the failure, col- lapse first by sliding, then by toppling, was filmed to allow further analysis.

59A

Machine excavation

862162 Laboratory assessment of the hydraulic cuttability of an Australian black coal Enever, J R Bull Proc Australas Inst Min Metal V290, N2, March 1985, P65- 70

An experimental investigation of the hydraulic cuttability of coal from the Theiss Dampier Mitsui Mine, Queensland, AUS- tralia, illustrates the ability of established cutting equations to describe the behaviour of the coal during cutting. The experi- mental equipment developed for the work proved reliable. Results are consistent with accumulated overseas experience.

862163 Cutting heads for hard surrounding rock in coalroad machine drivages (In German and English) Kleinert, H W Gluckauf Vl21, N20, 24 Ott 1985, P1537-1543 (german) P468-469 (english)

The research conducted by Bergban-Forschung into the improvement of in-line and transverse cutting heads for hard rock is described. The first requirement is to increase the spe- cific force of each pick without increasing wear. Cutting heads are improved by optimising the geometry and the materials from which they are made.

862164 Waterjet-assisted rock cutting systems - the present state of the art Hood, M Int J Min Engng V3, N2, July 1985. P91-Ill

A review is given of the benefits of assisting mechanical tools, notably drag bits, with moderate pressure waterjets suitably directed with respect to the bit. These benefits include reduced bit forces, especially the bit normal force, reduced bit wear, reduced dust make, and reduced incidence of frictional spark- ing. Experiments studying waterjet position, stand-off dis- tance, waterjet energy and bit velocity are described, and experiments designed to gain a better understanding of the mechanisms of rock breakage with this cutting method are outlined. The likely influence of waterjets on these fracture processes is analysed.

862165 Cutting efficiency and life of rock-cutting picks Hurt, K G; MacAndrew, K M Min Sci Technol V2. N2. April 1985, Pl3P151

Results obtained from testing rock-cutting picks using a boom tunnelling machine test rig. cutting in a hard limestone, are summarised. Parameters investigated included pick type and quality, depth and speed of cutting and the cobalt content of the tungsten carbide pick tips. Tests indicated that the best type of pick for hard rock cutting was the rotating point attack. The main agent of destruction of picks in hard rock appeared to be thermal stress.

862166 Cutting theory and coal seam assessment techniques and their application to shearer design Evenden, M P; Edwards, J S Min Sci Technol V2. N4, Aug 1985, P253-270

Some fundamental coal cutting theories and their application to power loader design are described, as are a number of tests used for coal seam assessment. Both laboratory and in situ tests are reviewed and their suitability to aid machine design is

0 1986 Pergamon Press Ltd. Reproduction not permitted