Application of high pressure water jets to longwall mining

132A built up, slowing down of breakage rate was observed. Reduction of rates of breakage was correlated with reasonable accuracy to the size distribution of particles in the mill. First order kinetics were restored by regular removal of fine particles.

underground experience, convergence monitoring instrumentation and economics of roofboiting are considered. Reduction in floor heave was most noticeable.

Maeldne excavation

883232 Wall reilfforcement in open pit mining Rosengren, K J

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Proc Large Open Pit Misdq Co~fereoce, N e w ~ , October 1986 P257-265. Publ Parkville: Aus[MM, 1986

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GimNkm~f V123, N23, 3 Dec 1987, P1469-1474 (German), P643-645 (English) Unacceptable tool wear and dust make is found when cutting through geological faults with conventional drum shearers. High speed photography was used to study the movements of cutter picks on rock. This has allowed the design of special fault-negotiating drums which cut more smoothly through rock and have much lower pick wear. Further design improvements to the shearer to minimise drum vibration and improve efficiency have been possible.

893233

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Available equipment for water jet assisted cutting of coal and coal measures rocks is described. Trials carried out in the Godborne Colliery, UK, are reported. Results indicated: improved coal product size if the number of picks is reduced; reduced dust make, power consumption and vibration; increased cutting rate; and little damage due to coal penetration beyond pick tip. Full production trials are suggested.

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The development of the use of stressed steel cables and untensioned fully grouted cable dowels, used for many years for rock mass reinforcement in civil engineering and un~rground mining respectively, for open pit mining is reviewed: These reinforcing elements are used to stabilise potentially unstable wall sections or to allow steeper slopes and reduce waste stripping problems. Wall stabilisation, mechanisms of support, cost assumptions and installation techniques are described. Applications to weak rock and the use of shear pins are considered. Many case histories are cited.

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Huang Chengxian Proc IRtermm~io#mlSj~cosimn on ~ im Rock Formatioas, ~ , 3-7 Nomsnber, 1986 P690-699, Publ Belting: Science Press, 1986 The stability under blasting of a gallery in faulted, j~ntcd and partially weathered granite was studiecL Borcbole ~ s i o n and acoustic methods were used to map the d i ~ u t ~ area, and stress distributions caused by b ~ ~ by finite element analysis. Field testa used unliued ~ t i o n s of the gallery and sections supported by shotcrete and long or short bolts. Deformations and st~ss states in the bolts and ahotcrete during blasting were measured. The long bolts were the most efficient support.

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Ko~, R; Schick, U ~fm,sdm~k V48, N6, Dec 1987, P329-334 Trials of a number of bolts, including cable bolts, are described. Mech_anised setting of bolts fixed by cenmntitious grout rather than resin adhesive has also been studied. A test rig has been developed, and results from this will be used to refine finite element methods for calculations in strata control. 883231

n~~ln N ~ wak ~ ~ to adk,~ C a ~ y Storey, R Mira Fair 11147, N316, Jan 1988, P32J-332 Systematic roof bolting has been succ~gfuily uNd to stabilise a roadway at over 800m depth in a seam with friable mudstone roof and ~ n ~ t ~ i c floor. Roadway design was modified flif0~tly from the norm. Model t~ts and mathematical anglysis shovel tim ~ buciding resi~._n~ by ~0%, whibt the roof bolting ~ it by a factor of 10. The equipment uaed to install the full column resin grouted bolts,

Rock Ymw~tlom, ~ i s G , 3-7 Nm~nb~, 1906 P732:738. Publ Beij'ing: Science Press, 1986 A finite element to describe a grouted bolt hasbeen developed. Extensive testing was carried out to underttand the behaviour of interfaces, grout material, and pull- and push-out situations under three dimemional stress for the design of the element. It is used to illustrate the reinforcing effect of bolts in underground openings and the interaction between grouted bolts and the rock mass. 8113235

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Rock Formatiem, ~ , 3-7 ~ , 1906 P739-744. Pub/Be/ring: Science Press, 1986 The b a ~ requirements of a rock bolt system to control deformation of soft rocks, the ~ o f the friction (Iq~lit set) bolt, and rock bolt-rock num i n ~ m demrihed. Cases of the use of friction bolts tO control c e n ~ in i ~ r ground mines are ~ , and the unique ~ o f friction bolts which make t ~ suitable for such applications are described.

© 1988 Pergamon Press pie. Reproduction not permitted