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Effect of anisotropy on the assessment of diggability for BWE
375A development of reinforced polymer bolts in Australia is outlined. Selection and testing of materials, preliminary laboratory pullout tests, concrete block tests, and in-mine tests are described. Recommendations for their successful use are made.
Machine excavation See also." 926104 926279 Investigations into the selection of the economic cutting speed of conical picks for boom roadheaders (In German)
926283 Bond strength of grouted cable bolts
von den Dreisch, S Gluckauf-forschungsh [/52, N5, Oct 1991, P214-219
Yazici, S; Kaiser, P K lnt J Rock Mech Min Sci 1/29, N3, May 1992, P279-292
The correct choice of pick for driving of mine roads is discussed. For soft to medium rocks, slim conical picks with small (19mm diameter) hard metal studs achieve high break out with low machine load and dust make. As hardness increases, larger studs (up to 50mm) are required. Coarse grained hard metal shows significantly lower wear rate than fine grained under these conditions. Pick wear rate rises only slightly with cutting speed up to an optimum value of 1.5 m/s. Above this speed, wear increases disproportionately.
A conceptual model for fully grouted cable bolts is presented. Bond strength of the bolt is taken to be primarily frictional and dependent on pressure at the bolt-grout interface. The increase in dilational pressure during loading can be explained in terms of elasticity, brittle cracking of the grout, and dilatative bolt-grout interface. Rock and grout properties and bolt and borehole geometries affect development of interface pressure. Load drop observed in some short bond length pullout tests can be explained, and should disappear if ratio of rock to grout stiffness exceeds 0.68. These results indicate that grouted cable bolts will be less effective in soft or disturbed rock masses than in stiff rocks.
926280 Model of tunnel boring machine performance
Wijk, G lnt J Geotecb Geol Engng VIO, N1, March 1992, P19-40 A mathematical model of TBM performance is developed, including an equation for cutter wear. Simple mechanical parameters and the Cerchar abrasivity index (CAI) are used to describe the rock mechanics. A complete description of tunnelling is possible, with instantaneous and accumulated values of penetration rate, tool condition, and costs as the tunnelling proceeds through a rock mass with variable properties (strength and CAI). Wedge shaped and constant wearflat tools are considered. The optimum changeover for wedge tools and optimum design of constant wearfiat tools are considered. 926281 Effect of anisotropy on the assessment of diggability for BWE
Bolukbasi, N; Koncagul, O; Pasamehmetoglu, A G Int J Surf Min V5, N3, 1991, P107-109 Oreinstein and Koppel (O and K) wedge tests were carried out on marl samples from 4 open pit mines, at angles of 0, 45, and 90 deg to the bedding. Variations in the cutting resistances (Fa, F1, Fls) were determined. Test angle has significant effect on cutting resistance, with a factor of 3 between Fa for 90 and 0 deg. To give a true indication of material diggability, the wedge test should be carried out normal to the bedding.
Rock and Soil Reinforcement and Support Bolts and anchors 926282 Tests make the case for 'plastic' roof bolts
Conley, N; Priest, S D Colliery Guard V240, N2, March 1992, P72-80 Rock bolts are an accepted component of rock support systems. Fabrication in fibre-reinforced polymers instead of the traditional steel offers advantages in terms of high strength with low weight, corrosion resistance, and amenability to machine cutting, making them ideal for use in coal mines. The
926284 Effect of stress change on the bond strength of fully grouted cables
Kaiser, P K; Yazici, S; Nose, J Int J Rock Mech Min Sci II29, N3, May 1992, P293-306 The bond strength of fully grouted cable bolts is primarily frictional and thus may change in response to increased interface pressure due to load-induced dilation or reduced pressure as a result of mining activity. The effect of stress change on bond strength is examined using a bond strength model described in a companion paper. Laboratory tests using grouted smooth steel bars support the theory. Mining induced stress reduction is considered to be a major factor affecting capacity of grouted bolts. In low to medium stiffness rocks, typical mining induced stress reductions may lead to almost total loss of load bearing capacity. 926285 Strata control - a new science for an old problem
Siddal, R G; Gale, W J Min Engr V151, N369, June 1992, P341-356 The evolution of the theory and practice of roadway stabilisation by roofbolting, now becoming accepted in the UK, is summarised. Factors affecting behaviour of mine roadways are examined, and concepts of roadway stabilisation outlined: roadway support; roadway reinforcement; beam building; and rock strengthening. Choice of system is discussed. Practical experiences with roofbolting in the UK are presented. Experiences of stress effects are described. Recent technology is reviewed, including cable bolting, Coupled Australian Technology roofbolts, injection anchors, modular rib bolting machines, and onboard bolters. Future developments are considered. 926286 Support of station brows in the no. 1 sub-vertical main and ventilation shafts on Oryx Mine
Brentley, K R Proc S A N G O R M Symposium on Impact o f Rock Engineering on Mining and Tunnelling Economics, Welkom, 7-8 October 1991 P9-19. Publ SANGORM: Orange Grove, 1991 Support design for stations at the Oryx Mine in bedded argillaceous and siliceous quartzites in conditions of high virgin stress is described. Conventional steelwork and concrete was rejected because of buckling and cracking when the shaft pillar
© 1992 Pergamon Press Ltd. Reproduction not permitted
Machine excavation See also." 926104 926279 Investigations into the selection of the economic cutting speed of conical picks for boom roadheaders (In German)
926283 Bond strength of grouted cable bolts
von den Dreisch, S Gluckauf-forschungsh [/52, N5, Oct 1991, P214-219
Yazici, S; Kaiser, P K lnt J Rock Mech Min Sci 1/29, N3, May 1992, P279-292
The correct choice of pick for driving of mine roads is discussed. For soft to medium rocks, slim conical picks with small (19mm diameter) hard metal studs achieve high break out with low machine load and dust make. As hardness increases, larger studs (up to 50mm) are required. Coarse grained hard metal shows significantly lower wear rate than fine grained under these conditions. Pick wear rate rises only slightly with cutting speed up to an optimum value of 1.5 m/s. Above this speed, wear increases disproportionately.
A conceptual model for fully grouted cable bolts is presented. Bond strength of the bolt is taken to be primarily frictional and dependent on pressure at the bolt-grout interface. The increase in dilational pressure during loading can be explained in terms of elasticity, brittle cracking of the grout, and dilatative bolt-grout interface. Rock and grout properties and bolt and borehole geometries affect development of interface pressure. Load drop observed in some short bond length pullout tests can be explained, and should disappear if ratio of rock to grout stiffness exceeds 0.68. These results indicate that grouted cable bolts will be less effective in soft or disturbed rock masses than in stiff rocks.
926280 Model of tunnel boring machine performance
Wijk, G lnt J Geotecb Geol Engng VIO, N1, March 1992, P19-40 A mathematical model of TBM performance is developed, including an equation for cutter wear. Simple mechanical parameters and the Cerchar abrasivity index (CAI) are used to describe the rock mechanics. A complete description of tunnelling is possible, with instantaneous and accumulated values of penetration rate, tool condition, and costs as the tunnelling proceeds through a rock mass with variable properties (strength and CAI). Wedge shaped and constant wearflat tools are considered. The optimum changeover for wedge tools and optimum design of constant wearfiat tools are considered. 926281 Effect of anisotropy on the assessment of diggability for BWE
Bolukbasi, N; Koncagul, O; Pasamehmetoglu, A G Int J Surf Min V5, N3, 1991, P107-109 Oreinstein and Koppel (O and K) wedge tests were carried out on marl samples from 4 open pit mines, at angles of 0, 45, and 90 deg to the bedding. Variations in the cutting resistances (Fa, F1, Fls) were determined. Test angle has significant effect on cutting resistance, with a factor of 3 between Fa for 90 and 0 deg. To give a true indication of material diggability, the wedge test should be carried out normal to the bedding.
Rock and Soil Reinforcement and Support Bolts and anchors 926282 Tests make the case for 'plastic' roof bolts
Conley, N; Priest, S D Colliery Guard V240, N2, March 1992, P72-80 Rock bolts are an accepted component of rock support systems. Fabrication in fibre-reinforced polymers instead of the traditional steel offers advantages in terms of high strength with low weight, corrosion resistance, and amenability to machine cutting, making them ideal for use in coal mines. The
926284 Effect of stress change on the bond strength of fully grouted cables
Kaiser, P K; Yazici, S; Nose, J Int J Rock Mech Min Sci II29, N3, May 1992, P293-306 The bond strength of fully grouted cable bolts is primarily frictional and thus may change in response to increased interface pressure due to load-induced dilation or reduced pressure as a result of mining activity. The effect of stress change on bond strength is examined using a bond strength model described in a companion paper. Laboratory tests using grouted smooth steel bars support the theory. Mining induced stress reduction is considered to be a major factor affecting capacity of grouted bolts. In low to medium stiffness rocks, typical mining induced stress reductions may lead to almost total loss of load bearing capacity. 926285 Strata control - a new science for an old problem
Siddal, R G; Gale, W J Min Engr V151, N369, June 1992, P341-356 The evolution of the theory and practice of roadway stabilisation by roofbolting, now becoming accepted in the UK, is summarised. Factors affecting behaviour of mine roadways are examined, and concepts of roadway stabilisation outlined: roadway support; roadway reinforcement; beam building; and rock strengthening. Choice of system is discussed. Practical experiences with roofbolting in the UK are presented. Experiences of stress effects are described. Recent technology is reviewed, including cable bolting, Coupled Australian Technology roofbolts, injection anchors, modular rib bolting machines, and onboard bolters. Future developments are considered. 926286 Support of station brows in the no. 1 sub-vertical main and ventilation shafts on Oryx Mine
Brentley, K R Proc S A N G O R M Symposium on Impact o f Rock Engineering on Mining and Tunnelling Economics, Welkom, 7-8 October 1991 P9-19. Publ SANGORM: Orange Grove, 1991 Support design for stations at the Oryx Mine in bedded argillaceous and siliceous quartzites in conditions of high virgin stress is described. Conventional steelwork and concrete was rejected because of buckling and cracking when the shaft pillar
© 1992 Pergamon Press Ltd. Reproduction not permitted