Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Patent
1996-02-12
1998-07-07
Taylor, Dennis L.
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
527401, 4052591, 4052596, E21D 2002
Patent
active
057758506
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a rock bolt that is adapted to be anchored such as by means of a cement or a chemical resin grout (hereinafter referred to as "grout") in a hole drilled in a rock formation.
The term "rock bolt system" as used herein is understood to cover the above described arrangement.
Rock bolt systems are used to stabilise rock formations in a wide range of situations, such as underground and surface mines, tunnels and cuttings, and rock bolts have achieved a high acceptance in both the mining and civil engineering industries.
In any given application, the purpose of a rock bolt system is to apply a clamping or confining action to a failing section of a rock formation to control deformation of the failing section and to enhance the strength of the failing rock section. In other words, the purpose of a rock bolt system is to allow load (forces) to be transferred from a failing section of a rock formation, through the grout, to the rock bolt and to sustain the load (forces).
The performance of a rock bolt system is dependent on the efficiency of transferring load (force) to a rock bolt from a rock formation. The efficiency of transferring load is dependent on the following two parameters.
(a) The maximum shear stress that can be sustained by the rock formation/grout and grout/rock bolt interfaces (the "load transfer" properties of the rock bolt system).
(b) The rate of generating shear stress (the "stiffness" properties of the rock bolt system).
An object of the present invention is to provide a rock bolt for use in a rock bolt system which enables the rock bolt system to have an improved performance when compared with rock bolt systems based on known rock bolts.
According to the present invention there is provided a rock bolt adapted to be anchored in a hole in a rock formation by means of a cement or a chemical resin anchor thereby to form a rock bolt system, the rock bolt comprising a core on which is formed a profile for optimising the load transfer and the stiffness properties of the rock bolt system, the profile comprising opposed sides, with one or both sides comprising at least two sections, with a first section being steeper than a second section.
The present invention is based on the realisation that the structural requirements of a rock bolt that have a bearing on the load transfer properties and the stiffness properties of a rock bolt system based on the rock bolt are different. The present invention is also based on the realisation that the performance of the rock bolt system in terms of these properties can be optimizsed by providing a profile on the rock bolt that has at least two sections on at least one side of the profile of which one section (the "first section") is formed to optimise the stiffness properties and another section (the "second section") is formed to optimise the load transfer properties.
It is preferred that the core be generally cylindrical.
The term "generally cylindrical" as used herein in connection with the core of the rock bolt is understood to cover, but is not limited to, (i) arrangements in which the core is cylindrical; and (ii) arrangements in which the core is cylindrical save for lengthwise extending flats or channels.
It is preferred that the rock bolt comprise a solid core.
It is preferred that the opposed sides of the profile converge to a ridge or apex.
The term "ridge or apex" as used herein in connection with the profile is understood to mean the juncture of the converging sides of the profile.
It is noted that, whilst in theory the juncture of converging sides is a line, in practice the juncture as formed may be rounded or flattened slightly.
It is preferred that both sides of the profile comprise the first and the second sections.
In an alternative arrangement it is preferred that only one side of the profile comprise the first and the second sections.
It is preferred that one or more of the sections of the profile be planar.
It is preferred that one or more of the sections of the profile be curved.
It is preferred that the first sec
REFERENCES:
patent: 832711 (1906-10-01), Webber
patent: 1367182 (1921-01-01), Conkling
patent: 1400278 (1921-12-01), Fougner
patent: 2245419 (1941-06-01), Unke
patent: 3489437 (1970-01-01), Duret
patent: 4989902 (1991-02-01), Putch
patent: 5104266 (1992-04-01), Daryoush et al.
Derwent Abstract Accession No. 87:078236/11, Class Q49, 23 Jul. 1986 1245710 (Cen Plan Des Techn).
Fabjanczyk Mieczyslaw Wieslaw
Gale Winton James
Renwick Maxwell Thomas
Kerins John C.
Taylor Dennis L.
The Broken Hill Proprietary Company Limited
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