1、翻译部分英文原文The variability of some rockbolt parameters and theirpotential impact on anchorage performancePC HaganThe University of New South Wales (UNSW), SydneyAn assessment of the possible risk factors that may affect the intended performance of fully encapsulated rockbolts was undertaken. The study
2、endeavoured to quantify the level of variability of some rockbolt parameters from across seven coal mines.INTRODUCTIONRockbolts are at the core of strata control in most Australian underground coal mines. Previous studies have found however that despite an estimated industrywide annual expenditure o
3、f over $A35 million on rockbolts, it is estimated that 30%35% of the rockbolts do not perform to specification and may represent some risk to the maintenance of a safe workplace environment (Galvin et al 2001).There are several factors contributing to the underperformance of rockbolts including inst
4、allation procedures and the storage and handling of rockbolts, the effects of which can be mitigated through effective risk management practices.In an effort to improve the performance of rockbolt systems, a research facility has been established at the University of NSW (UNSW) with funding provided
5、 by the Australian Coal Association Research Program (ACARP). The objective of the research is to gain a better understanding of the load transfer mechanisms of fully encapsulated rockbolts and identify the risk factors that impact on the performance of rockbolt systems, thereby contributing to an i
6、mprovement in safety at mine sites.Research undertaken using the facility has examined factors that may impact the anchorage performance or load bearing capacity of fully encapsulated rockbolt systems; the effect of bolt profile on load transfer; the nature of the load transfer between rockbolt, res
7、in and rock; and, a study on the quality conformance of rockbolts at mine sites.The objective of this paper is to review current understanding and knowledge on the anchorage performance of rockbolts combining this with the latest research findings to provide a foundation on which hazards may be iden
8、tified and improvements made to workplace practices.RISK FACTORSThe risk factors that can influence the performance of a rockbolt support system can be broadly classified into three groups design, operation and quality control factors. Table 1 lists a number of risk factors related to each of these
9、groups.Many of the risk factors have a similar outcome in terms of a reduction in anchorage performance of rockbolts. The impacts of these risk factors and their underlying causes are discussed in the following section. TABLE 1Factors that may influence rockbolt anchorage performanceDesignOperationQ
10、uality Control(non-conformance with specifications) spacing length of rockbolt rockbolt inclination strength of rockbolt resin characteristic resin annulus thickness roughness of borehole surface straightness of borehole length of borehole spin and cure times location and inclination of boreholes ro
11、ckbolt diameter core and rib height rockbolt straightness length of rockbolt surface corrosion drill bit size turnover of resin cartridges physical environment (temperature, moisture content, etc) and duration in storageIn addition to these factors, there are other variables that may also impact on
12、rockbolt performance. Many of these lie outside the direct control and monitoring capabilities of personnel at the mine sites. Such factors include the metallurgical properties and deformation pattern of the rockbolt, the chemicals used in the manufacturing process of resin cartridges and consistenc
13、y of these properties. Other measures are required to manage these risk factors by the suppliers such as quality control systems and independent auditing.Resin AnnulusIn general terms, the anchorage capacity of a rockbolt increases with rockbolt diameter this holds true so long as the resin annulus
14、or thickness of the resin between rockbolt and rock remains constant. With an increase in borehole diameter not only does the maximum load bearing capacity increase with rockbolt diameter but also the resistance to shear failure of the resin/rock interface with a larger rock surface area. Karabin an
15、d Debevec (1978) confirmed this general principal in pullout tests conducted with three different borehole sizes while maintaining a constant resin annulus, the results of which are shown in Figure 1.Figure 1. Effect of borehole diameter on the resistance todisplacement of a rockbolt(after Karabin a
16、nd Debevec, 1978)For the case of relatively soft rock such as that associated with coal measures where the resin/rock interface is the weakest link and the length of encapsulation is limited, borehole diameter can be increased to achieve the required load capacity per unit length of the anchorage system. Snyder, Gerdeen and Viegelahn (1979) argued that increasing the borehol
