Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Patent
1995-05-01
1997-06-10
Neuder, William P.
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
4052595, E21D 2105
Patent
active
056369450
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a device for mounting rockbolts.
When permanently safeguarding with rockbolts, e.g. in tunnels, corrosion protection is required. To achieve this, the bolt may be completely moulded by injecting cementing grout or by "cement grouting". The bolts are usually hot galvanized or powder painted.
It is desirable to combine the use of bolts utilized for making a work place safe, without any requirement for corrosion protection, and the succeeding cementing to increase the fastening and establish protection against corrosion.
To achieve this, tube shaped bolts with an expansion bushing at the inner end have been used. This solution to the problem allows later cementing, but is expensive because the cost of tube bolts is approximately twice that of steel bolts. Additionally, this solution is sensitive to incorrect grout consistency.
It has been proposed to after treat steel rods with a cementing hose and a venting tube. A steel rod is fastened at its inner end with an expansion bushing or a plastic grouting, e.g. a polyester cartridge. Additionally a venting tube is introduced to the bottom of the hole and a cementing hose is introduced approximately 25 cm into the hole. The outer part of the hole is then sealed with sealing foam, before introducing of cementing grout. The air in the hole will then expel through the venting tube.
This cementing requires additional mounting time and is impaired by bad sealing with the sealing foam. This results in leakage before the hole is filled and a part of the bolt not being covered by cementing grout.
SUMMARY OF THE INVENTION
The main object of the invention is to provide a device for fastening rockbolts, which may be used more quickly and with less expensive equipment than has been the case with known methods. Further, it has to ensure a sufficient quality and safety of the fastening to avoid damages due to bolt deficiency caused by bad fastening. It is a particular object to provide a fastening method giving lasting corrosion protection, to increase the longevity and safety of the bolt.
To practice the invention, only an inexpensive and easily mounted tube is required. This tube can be manufactured quite inexpensively from plastic and can be easily mounted on the rockbolt in advance of or at mounting in the rock, i.e. at the front of a tunel during blasting work. The device will thus be prepared for later cementing with grout or other cementing mass to ensure fastening of the rockbolt and corrosion protection. In this way, rapid insertion of the rockbolt as protection during the work is achieved, and the expansion bushing at the inner end of the rockbolt can be loaded. It is then possible to make a rapid pressurised introduction of cementing grout, as the tube will ensure a complete evacuation of air from the rockhole and a corresponding introduction of cementing grout to thereby provide the required protection.
The tube can be secured to the support element in different ways and be manufactured from different materials and in different shapes, as stated in the independent claims and in the description of the examples.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention in one embodiment is described in more detail with reference to the drawings, in which
FIG. 1 is an axial section and
FIG. 2 shows in larger scale detail of the outer end of the device of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1 there is shown a rockhole 11 with a rockbolt 12 of steel with which is threaded 13 on the inner end and on which an expansion bushing 14 is mounted. The outer end is threaded 15 with a nut 16 thereon. Under the nut 16 is a spherical support or pressure element 17, (in the following denominated "pressure sphere") defining a convex wall or surface, thrust against a washer element 18 on the rock wall 19 around the hole 11. The washer element 18 has an upwardly curved flange 20 along the rockwall toward the rockhole. This flange is adjacent the inner part of the pressure sphere 17.
The pressure sphere 17 which is
REFERENCES:
patent: 4140429 (1979-02-01), Herbst
patent: 4655644 (1987-04-01), Lane et al.
patent: 4832534 (1989-05-01), Duvieusart
patent: 4992004 (1991-02-01), Haug
patent: 5375947 (1994-12-01), Gouws et a.
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