1、翻译部分英文原文Quantifying the performance of resin anchored rock bolts in the Australian underground hard rock mining industry， Western Australian School of Mines, PMB 22, Kalgoorlie 6430, Australia Barrick Australia, P.O. Box 1662, Kalgoorlie 6433, Australia1. IntroductionThe purpose of rock support and
2、reinforcement is to ensure excavations remain safe and open for their intended life span. The effectiveness of a reinforcement strategy is important for two main reasons: these being safety to personnel and equipment, and achievement of the most economical access to extract ore. For a particular roc
3、k mass, a stabilization scheme capable of matching the expected behaviour is selected based on an assessment of the likely failure modes predicted from the interaction of an excavation (geometry and purposes), the network of geological discontinuities, weathering and the loading conditions from stre
4、ss and blast damage 14.In most underground mines, the primary form of excavation stabilization is provided by a pattern of rock bolts installed within the rock mass. This is complemented with the use of passive support, such as that provided by mesh or shotcrete, in order to provide surface restrain
5、t at the exposed excavation boundaries.The reinforcement controls the overall excavation stability through keying, arching or composite beam reinforcing actions 5, while the mesh and/or shotcrete supports the small loose pieces of rock that may detach between the rock bolt plates 6,7.In general, a s
6、tabilization scheme cannot be selected without consideration of the ground support drilling equipment available at a particular mine site. A modern, optimal strategy would consist of mechanized installation of reinforcement and support in a single pass in order to increase productivity and reduce ex
7、posure of personnel and equipment during installation.2. Mechanized resin anchored bolt installationOver the last decade or so, jumbo-installed, 45mm diameter galvanized and black steel friction bolt stabilizers have become the preferred form of reinforcement in underground hard rock mining in Austr
8、alia 8,9. This has been mainly driven by a desire to achieve fast development rates and low costs in order to allow the extraction of low-grade orebodies. In more recent years, as the mining operations are getting deeper and the rock masses are becoming highly stressed, other reinforcement schemes s
9、uch as fully encapsulated resin anchored bars are being considered as an alternative to friction bolts for longterm reinforcement 1013.The typical bolts being used in the underground hard rock mines have been modified from the bolts used in the coal mining industry. The modifications have been neces
10、sary due to the need to drill larger hole diameters with the type of equipment used in the hard rock metaliferous mines. The modification is mainly in the form of paddles or the use of a spring welded on to the end section of the bolts. Fig. 1 shows the anchor sections for a 24mm Posimix bolt with s
11、pring arrangement and a 27mm Secura bolt showing a paddle arrangement. The Posimix wire is 3mm in diameter and has a length of 500 mm. The paddle width is 29.2mm and they have been sheared into the end of the bolt for the purpose of mixing resin.Fig. 1. Posimix and Secura bolts showing spring and pa
12、ddle mixing arrangements, respectively.Nevertheless, the introduction of mechanized resin anchored bolting using jumbos has been difficult to implement economically due to the high cost of resin transport and storage: this requires the use of refrigerated trucks and surface and underground storage f
13、acilities. Other problems include speed of installation of bolt installation, including ability to install mesh on a single pass, poor matching of bolt diameter to jumbo-drilled hole diameters, as well as operator skills.3. The load transfer conceptA fully encapsulated rock bolt is classified as con
14、tinuous mechanically coupled in terms of the basic mechanisms of load transfer between the reinforcing elements and a rock mass 14. A continuous mechanically coupled (CMC) reinforcing element relies on a fixing agent, usually a cement or resin based grout, which fills the annulus between the element
15、 and the borehole wall. The main function of the grout is to provide a mechanism for load transfer between the rock mass and the reinforcing element.The load transfer concept is critical to understand how fully encapsulated bolts stabilize an excavation. Windsor and Thompson 15, explain the concept
16、by means of the three basic individual components, listed as follows (see Fig. 2):1. Rock movement at the exposed excavation boundary, which causes load transfer from an unstable region (wedge or slab) to a reinforcing element.2. Transfer of load via the reinforcement element from the unstable portion to a stable interior region within the rock mass.3. Transfer of the reinforcing element load to the rock mass in the stable zone
