Controlled blasting in hard intense jointed rock in tunnels

Controlled blasting in hard intense jointed rock in tunnels

195A with air as the drilling fluid. Tests were carried out on intact rock. rock heated to various temperatures and allowed to cool to ambient, and ro...

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195A with air as the drilling fluid. Tests were carried out on intact rock. rock heated to various temperatures and allowed to cool to ambient, and rock heated and maintained at temperature. Mechanical properties measured were S-wave velocity, Brazilian tensile strength and uniaxial compressive strength. Drilling rates were seen to fall with temperature of heating for both hot and cooled rocks. The drilling rate was concluded to be dependent on the fractured state of the rock, which is affected by the heating and cooling treatment and by the temperature gradient caused by the flushing air.

Blasting 865197 Controlled blasting in hard intense jointed rock in tunnels Rustan, A; Naarttijarvi, T; Ludvig, B CIM Bull [:78, N884, Dec 1985, P63-68 Accidents from falling rock in intense jointed rock masses in tunnelling is one of the major reasons for serious injuries and deaths in Swedish mines. A project directed towards controlled blasting in hard intense jointed rock started with an extensive literature review. Model tests with a new equivalent model material have been initiated to find ways of improving blasting techniques. Results led to the theoretical development of a new initiation method with ultra short delays for controlled blasting, called 'Cutblasting'. The objective of the fullscale tests was to compare different methods for controlled smooth blasting and to develop more effective methods. A new classification system for controlled blasting regarding the damage to the surrounding rock is proposed.

865198 Computational techniques for predicting rock fragmentation and rubblization Taylor, L M; Kuszmaul, J S Proc 5th Engineering l~lechanics Division Speciality Confi,rence, Wyoming, !-3 Aug 1984 VI. P157-159. Publ New York: ASCE, 1984 The confincd blasting of rock to create a suitable rubble bed for in situ retorting of oil shale is considered as a two phase process. In the first phase, the first few milliseconds after the blast, the rock is fractured and fragmented by the early time blast induced stress wave. The second phase occurs in a time span over about one second and includes long-term fragment motion, which determines the final void ratio and permeability of the bed. Two models to analyse the two phases of rubblisation are described.

865 ! 99 Effect of delay times on fragmentation. Model tests (In Swedish) Norell, B Swedish Detonic Research Foundation report DS 1985: 1, 15 May 1985, 48P Literature relating delay times and their effects on fragmentation in rock blasting is reviewed. A number of small scale model blasts using a rock like material NIMI27 have been carried out, which show an optimal interhole delay of 2ms/m burden. Variations in optimal delay of 2-10ms/m burden are found in the literature, these variations being dependent on model scale, material and hole configurations. NIMI27 is seen to be a useful material for small scale models, especially if it can be manufactured in thicker plates than at present.

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Machine excavation 865200 New heading systems - the way to higher profitability (In German and English) Knickmeyer, W Glackauf V122, N3, 6 Feb 1986, P230-234 (german), P74-76 (english) The major factors influencing the cost effectiveness of the boom roadheader have been analysed, and, with the exception of deployment rate,all are inherent in the system. To increase productivity, research is being carried out into high pressure water jet cutting, a profile cutting system and selective cutting systems for driving arch roadways with roller bits. Initial progress in this long term project is reported.

865201 Computer-controlled, water-jet-assisted roadheaders and shearers (In German and English) Kogelmann, W J Gluckauf VI22, N8, 24 April 1986, P556-563 (german), P162-165 (english) Water jet assisted cutting, at pressures up to 700 bar, can greatly increase the excavation rates of rocks and minerals. The components of water jetting systems, pick design for assisted cutting and assisted cutting with standard picks are described with particular reference to applications to roadhcaders and coal shearers. The advantages in lowered bit consumption, coarser coal with less fines and energy savings are important for shearers. The major advantage when applied to roadheaders is the ability to cut rock some 20-35% harder than is now possible with this type of machine, such that boom type roadheaders could meet the rock conditions found in 70% of all tunnels and mines.

865202 Relative cuttability of Coal Measures stone Hughes, H M Min Sci Teehnoi 1:3, N2, Jan 1986, P95-109 The technology used in the development of machines for the drivage of tunnels and roadways, and for the construction of holes and openings in stone in the Coal Measures are examined. The paper summarizes the relevant characteristics of Coal Measure stone and associated machines.

865203 Review of waterjet excavation research Summers, D A In: Research and Engineering Applications in Rock Masses (paper to the 26th US Symposium on Rock Mechanics, Rapid City, 26-28 June 1985) V2, P895-903. Publ Rotterdam: A. A. Balkema, 1985 The history and development of water jet and water jetassisted rock cutting is presented and potential advantages accruing from their adoption are examined. The present state of water jet cutting technology in the USA is described.

865204 Rock fragmentation by cutting, ripping and impacts. Some theoretical and experimental studies Ranman, K E PhD Thesis, Lulea Univ 1986: 49D, 148P Various methods of mechanical rock breaking are studied. The work is divided into five sections: (I) boreability testing and prediction; (2) full scale rock cutting tests using cutters with button inserts and steel discs; (3) development of a tensile stress model describing side chipping between rock cutting

© 1986 Pergamon Journals Ltd. Reproduction not permitted