Hydraulic and earth engineering – Earth treatment or control – Chemical
Patent
1989-07-11
1991-01-15
Reese, Randolph A.
Hydraulic and earth engineering
Earth treatment or control
Chemical
405259, 411 8, 411 9, E21D 2102
Patent
active
049849379
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a rock bolt comprising a bolt rod adapted to be secured in a borehole, a bolt head for a retaining plate adapted to be attached outside the borehole, and a compressively loaded deformable member, which surrounds the bolt rod, incorporated in the supporting connection between the retaining plate and the bolt rod.
In the provision of supports and lining in underground cavities and particularly in the construction of tunnels or galleries such rock bolts serve as safety elements, which are systematically set to extend approximately radially to the axis of the tunnel or gallery and take up a more or less large part of the rock pressure and introduce the forces they have taken up into the depths of the rock which correspond to the borehole so that the rock contributes to the support. In order to avoid a load on the bolt rods in excess of the ultimate load and because the radial rock pressure decreases with the deformation, rock bolts are used which are of the kind described first hereinbefore and which permit a controlled deformation of the rock within certain limits so that they permit a simplification of the supporting structure in the provision of supports and lining in underground cavities.
A rock bolt which is of the kind mentioned first hereinbefore is known from Austrian Patent Specification No. 378,823. A bolt head which is secured to the bolt rod protrudes outwardly through an opening of the retaining plate and a sleeve is inserted between the bolt head and the retaining plate and under a corresponding load will be expanded by the conical or spherical bolt head as it penetrates so that the anchoring structure will be yieldable in dependence on the elongation behavior of the supporting sleeve. German Patent Specification No. 1,583,803 discloses a rock bolt which has a bolt head that is supported on the retaining plate and constitutes a drawing die, which surrounds the bolt rod at a distance from its protruding end, which is smaller in diameter in the region in which the drawing die is attached so that the grooved bolt rod can be drawn out through the drawing die with a removal of material and/or deformation. The two known designs are expensive owing to the required selection and quality of the materials and in dependence on the length in which a deformation is desired they must protrude from the retaining plate to a considerable extent and can take up only smaller supporting forces and only a small influence can be exerted on the resistance of the shaped part to deformation, i.e., on the deforming process and also on the characteristic of the resistance which opposes the drawing-in of the bolt rod.
It is an object of the invention to eliminate the disadvantages which have been pointed out and to provide a rock bolt which can rationally be manufactured and can be set in a simple manner and in case of need can be designed to have no parts which protrude a large distance from the borehole and will provide a yieldable support which has an adjustable and/or selectable characteristic and with full utilization of the load-carrying capacity which is determined by the strength of the bolt rod will permit an influence to be exerted on the dependence between supporting forces and the deformation.
The object set forth is accomplished according to the invention by the deformable member constituting an upsettable sleeve member accommodated with a clearance in a tubular member adapted to be inserted into the borehole and held between a rodside thrust face and a plateside thrust face, the tubular member having an outer end bearing on the retaining plate and comprising a collar constituting the plateside thrust face adjacent an inner end thereof.
The upsettable member can be made without a high expenditure and by the selection of its wall thickness, shape and material and by the provision of a profile etc. may be provided to have an upsetting behavior which is well adapted to the load conditions which are to be expected. Any risk of a sudden yielding caused by material defects will be precluded.
REFERENCES:
patent: 3967455 (1976-07-01), Conway
patent: 4187040 (1980-02-01), Donan
patent: 4472088 (1984-09-01), Martin
patent: 4519735 (1985-05-01), Machtle
patent: 4613254 (1986-09-01), Liebig
patent: 4648753 (1987-03-01), Stephan
patent: 4789284 (1988-12-01), White
patent: 4850746 (1989-07-01), Finsterwalder et al.
Ingenieure Mayreder, Kraus & Co. Baugesellschaft m.b.H.
Kelman Kurt
Reese Randolph A.
Ricci John
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