926255 Expert system of discontinuity properties evaluation Yun-mei Lin; Xia-ting Feng Rock Mechanics as a Multidisciplinary Science, Proc 32nd US Symposium, Norman, 10-12 July 1991 Pl185-1194. Publ Rotterdam." A A Balkema, 1991 Deformation and failure of rock masses often occur along rock discontinuities and are closely related to the geomechanical properties of these discontinuities. An expert system has been developed to help evaluate a system of discontinuities on the basis of type, spacing, number, orientation, roughness, persistence, filling state and materials, aperture, and presence and action of water. The characteristics of the expert system (PANDA), knowledge representation, knowledge base and its structure, and goals are described.
Rock Breakage and Excavation Rock fracture under dynamic stresses 926256 Laboratory scale modelling of single hole blasting Bhattacharya, J; Kumar, N J Min Metal Fuels V34, N4, April 1991, P89-99 Rock fragmented by blasting is subjected to an instantaneous load. An attempt to simulate this in the laboratory by high velocity impact tests was unable to reproduce realistic blast conditions, but interesting data on dynamic fragmentation of rock under point loading were obtained. A point impact tool loaded by a dropping weight was used. The equipment and specimen geometries are described. Energy considerations are analysed. Fragmentation results and how they correlate with other rock properties are discussed.
926257 Mathematical modelling of rock fragmentation by high pressure arc discharges Garnsworthy, R K Proe 3~1 International Symposium on Rock Fragmentation by Blasting, Brisbane, 26-31 August 1990 P143-147. Pub/ Parkville: AusIMM, 1990 Laboratory experiments were carried out in which a high pressure arc discharge in a borehole in a basalt core was used to induce fragmentation. Fracture development was recorded by high speed cameras and heave velocity measured using a laser technique. A mathematical model for fragmentation is presented, which gives crack numbers and accelerations sufficiently close to those seen to suggest its physical basis is correct. Further development can now continue. The usefulness of the arc discharge technique in modelling blasting is evident.
Drilling 926258 Precision drilling of blast-holes (In French) Heraud, H; Roy, J Y Industrie Minerale V74, May 1992, P57-60 The quality of blasthole drilling has a large influence on the result of the blast. Deviations from design pattern, due to material properties or drilling procedure, are obvious in presplitting, but not directly visible in ground breaking, and ~
can lead to overbreak, vibration, or oversize blocks. Deviation tolerance is only 2-3%. Classical drilling techniques can produce accurate drillholes provided the equipment is well maintained and the operator skilled. Modern instrumentation to improve placing and alignment of holes, drilling monitoring, and post-drilling examination permit better control to be achieved.
926259 Investigation into rock drilling Pandey, A K; Jain, A K; Singh, D P Int J S u r f M i n V5, N3, 1991. P135-141 Choice of drilling method depends on many factors, including rock properties, production requirements, and equipment availability. High penetration rate with low wear is the ideal. Laboratory drillability tests have been carried out using rotary and percussion drills and the microbit drilling machine, which incorporates the principles of the rotary drag bit. Correlations between penetration rate and bit wear and rock properties and drilling variables have been examined for Chunar sandstone and Makrana marble.
926260 Elastic to plastic impact transition in rock deformation Inyang, H J; Pitt, J M lnt J Surf Min V5, N3, 1991, P143-149 Effectiveness of percussive impact for rock breaking depends primarily on the level of energy applied relative to the rock strength. Each brittle rock has a critical impact energy at which intense fracturing initiates. This energy is dependent on flaw size distribution and total porosity. Rebound tests with a specially designed hammer on a range of rocks indicate the critical energy value correlates well with ultrasonic pulse velocity. Below the critical energy, deformation is mainly elastic with minor crushing in the vicinity of the bit tip: above it, deformation is largely plastic, with extensive fracturing and crushing.
926261 Heavy weight rock bits increase penetration rates in hard rock Grimes, R E; Felderhoff, F C; Brown, H Oil Gas J V90. N20, May 1992, P76-79 Faster penetration rates and lower costs have been achieved in the hard rock formations of the Permian basin in the West Texas/southeastern New Mexico region using improved, high weight on bit drill designs. Tungsten carbide insert bits with moderately high density of insert rows and low cone offset show improved durability and lower bit wear. Bearing design and metallurgy were matched to the increased loads. Both rate of drilling and length before bit change show significant improvements.
926262 Cationic drilling fluid improves ROP in reactive formations Hemphill, T; Valenziano, R; Sketchier, B Oil Gas J V90, N23, June 1992. P60-65 High permeability sands and dispersive clays and shales cause difficulties in drilling wells in the Gulf of Mexico. A cationic water-based drilling fluid has been developed to alleviate these problems. The background to use of organic polymer additives in drilling muds is briefly outlined. Improvements possible in penetration rate in the softer rocks, stability of reactive clays and shales, reduced bit bailing, filtration control, and permeability plugging/filter cake characteristics are described with reference to Gulf of Mexico wells.
1992 Pergamon Press Ltd. Reproduction not permitted