Analytical and empirical studies related to geotechnical design of mine shafts.

摘要

Geotechnical design of mine shafts has received little attention in the literature, and shafts are still constructed predominantly on the basis of prior experience. Literature review and preliminary investigation led to the definition of the problem in three main aspects: (i) Analytical studies consisting of analyses of stress distribution around shaft openings, a sensitivity analysis of design parameters, and an analysis of failure mechanisms; (ii) Empirical studies; and (iii) Development of design guidelines.;Analytical studies helped in the understanding of the stress distribution around mine shafts and in the quantitative estimation of the extent of the disturbed rock zone. The extent of the disturbed rock zone was used in the determination of the bolt length and bolt load, and the support pressure on the lining.;The sensitivity analysis determines the effects of the design parameters. The results led to the determination of the most appropriate orientation of rectangular shafts with respect to the direction of field stresses and the degree of the anisotropy of the rock mass.;Three primary types of failure mechanisms, using analytical and graphical methods, were recognized: shear failure, compression failure, and buckling of the vertically bedded layers. The results of this study are essential for design of support systems.;The adjustments for the favorability of the discontinuity orientations with respect to the direction of the shaft were developed. The adjustments depend on the friction and dip angles of the discontinuities. The range of the adjustments is from 0 to ;Both the primary and the permanent support systems were identified. Guidelines for the design of rock bolts in rectangular and circular shafts were developed. Another major outcome of this research was new guidelines for concrete lining of circular and rectangular shafts with uniform and non-uniform external support pressures based on the design codes of American Concrete Institute.;The results of this research will contribute to understanding of the geotechnical behavior of mine shafts and will be useful as guidelines for the design of rock bolts, and plain and reinforced concrete lining in rectangular and circular shafts.