Title of Invention

A ROCK BOLT FOR REINFORCING ROCK STRATA IN A ROOF OR SIDE OF MINE OR TUNNEL

Abstract

In the present invention there is provided a rock bolt useful for reinforcing several rock strata in a mine or tunnel roof or side, which comprises in combination a rock bolt, bearing plate and a nut. The combination consisting of an elongated cylindrical rod the peripheral body of which being provided along its length with a plurality of pairs of pointed and inclined web protrusions placed diametrically opposite to each other. The protrusions in form of elongated stud or a web act as guides to align the bolt inside a hole in a multi-layered rock strata and enable tearing of polyethylene packets of grout material into shreds, mix the grout material uniformly and distribute the grout material uniformly along the annular space. The elongated cylindrical rod is having a pointed upper end and a threaded lower end. The threaded portion of the said rod being provided with a removable co-centric bearing plate having a central hole of diameter less than the rod but more than the threaded portion, thus ensuring proper alignment of the bolt in a previously drilled bore-hole This enables holding of the bolt straight in a borehole in the rock layers and thereby ensure a uniform grout distribution in the annular space between the bolt and the rock. The threaded portion being provided with at least one removable nut having peripheral diameter greater than the central hole of the said bearing plate. This bolt will be able to hold and stitch multi rock layers when used in combination with a known grouting medium, which may be composed of cement or resin. The rock bolt of the present invention is simple to manufacture, easy to install and cheaper in cost.

Full Text

The present invention relates to a rock bolt for reinforcing rock strata in a mine / tunnel roof / side. The present invention particularly relates to a reinforcing long bolt for supporting several rock strata in a mine / tunnel roof / side. The present invention provides a novel rock bolt useful for strengthening layers of rock in a mine or a tunnel roof or side. This bolt will be able to hold and stitch the rock layers when used in combination with a known grouting medium, which may be composed of cement or resin. The novel rock bolt of the present invention will be capable of holding itself straight into a previously drilled borehole in the rock layers and thereby ensure a uniform grout distribution in the annular space between the bolt and the rock. It is well known that various kinds of bolts are used to stitch several rock strata to increase the bending moment of the individual layer of rock, which in turn supports the roof of the said opening. This system of composite layer reinforcement serves the basis for support design and the support mechanism in the mine and tunnel openings. Extensive efforts have been devoted to the development of various supporting devices for mine roofs and tunnels. To highlight the wide mining and tunneling usage and continual efforts, which have been made by other inventors to improve the performance of supporting bolts, a few patent references are provided below for illustration. Reference may be made to U.S. patent no. 4,173,918, titled: 'Roof bolt and the like'. This invention relates to the field of "roof bolts" AND "mine tunnels" which comprises of a roof bolt for use in a predrilled hole in a mine has an elongated stud on which is mounted a cylindrical sleeve. The first or inner end of the stud is threaded and carries a wedge adapted to enter one end of the sleeve and forcefully expand it in response to the rotation of the stud. The second or outer end of the stud is threaded in a like direction and carries a nut, held in a fixed position of rotation on the stud by a shear pin engaged in a common hole through part of the nut and stud. A shoulder plate is carried on the stud between the nut and sleeve, and the second end of the stud has a backing plate attached. The main disadvantage of this bolt is that it binds the layer in a mechanical method and is having complicated and slow installation process thereby requires a very skilled labour. Reference may be made to European patent no CA2466283. The invention relates to a rock bolt which includes a tubular member, a device at one end of the tubular member for mechanically anchoring the tubular member inside a hole in a rock face, a bar which is partly inside the tubular member with a threaded portion which projects from the tubular member, and wherein the tubular member is formed with load resisting formations which restrain the bar from being pulled out of the tubular member. The main disadvantage of this system is that it is difficult to install, slow, does not ensure uniform distribution of the grout material. Moreover it does not grout the last few layers of the strata above the mine tunnel. Reference may be made to U.S. patent no. 4,666,345 titled 'Rock bolt structure'. The invention relates to an elongate hollow rock bolt, bolt installations, and process of effecting the same, wherein the bolt is slightly over-size relative to the transverse cross-section of the mine roof hole or aperture in which the bolt is to be installed. The bolt has a radial, transverse polygonal cross-section formed by contiguous deflectable resilient sides provided with outwardly directed fins, the latter being tapered. When the bolt is impact-forced into a mine roof aperture, the fins are forced inwardly, deflecting the bolt sides which, owing to their resiliency, maintain the fins and the aperture wall areas contacting the same under compression, thus increasing the holding effect upon the bolt. The latter may be grouted in, and also may have a pre-installed bearing plate provided with an aperture and slide-slots accommodating the fins. The main disadvantage of this system is that it has a complicated design and requires a separate grout pump, which adds to the cost of rock bolting system. This bolt requires to be impact-forced inside the bore hole. Reference may be made to U.S. patent no. 4,192,631 entitled 'Mine roof support method and apparatus'. The invention relates to a rock bolt, which is tensioned to hold a support plate or similar structure in firm engagement with the face of the rock structure. The apparatus includes an elongated bar engaged by thread with one end of a hollow collar, the other end of which is threaded to receive the rock bolt. An installation tool in the form of an elongated rod is provided at one end with outwardly extending fixed members for engagement with stop surfaces on the other end of the collar. Rotation of the tool is transmitted to the collar and bar to break a resin cartridge within a blind drill hole in the rock formation and mix the contents thereof. Upon hardening of the resin mixture about the bar, the installation tool is withdrawn and the rock bolt carrying a roof support plate is threaded into the anchored collar and tensioned to the desired degree. This invention requires a separate installation tool and is having a complicated installation process. Reference may be made to U.S. patent no. 4,295,760 titled: 'Rock bolt anchor', in which a series of adjoining cam discs are mounted on a foot having an inclined surface, with the cams surrounding a stem connecting the foot and a head of a diameter to fit within a borehole in rock. The stem extends axially between the head and the foot, while the inclined surface is spaced from the head and is inclined with respect to the axis of the anchor. The head has threads for receiving corresponding threads on a bolt which extends through the foot and stem, while the flat cam discs have a width less than, and a length greater than, the diameter of the borehole. The anchor is moved into the borehole and the cam discs are caused to engage the wall of the borehole, the bolt then being turned to thread the head against the cam discs and force the ends of the cam discs against or into the wall. The main disadvantage of this system is that it has a complicated design, which adds to the cost of rock bolting system. This bolt also requires to be forced inside the bore hole by impact-hammering. Reference may be made to U.S. patent no. 4,299,515, titled 'Rock reinforcement system'. This innovation relates to a system for reinforcing a rock formation, in mining or tunneling operations, wherein an elongated bolt is anchored in a blind drill hole in the rock formation by both a mechanical expansion anchor and a resin grouting mix. The invention is particularly directed to novel means which prevent relative rotation of the bolt and anchor in one direction and allow relative rotation in the opposite direction, whereby a conventional, two-compartment resin cartridge can be broken and its contents mixed while rotating the bolt and anchor in the first direction, and the anchor expanded to tension the bolt by reversing the direction of rotation before the resin mix hardens. The novel means comprise a collar element, which is affixed to the end of the bolt above the expansion anchor and cooperatively engages a stop means on the anchor in only one direction of bolt rotation. The main disadvantage of this system is that it also has a complicated installation procedure, which adds to the cost of rock bolting system. It does not ensure uniform distribution in thickness of grout material along the annular space between the bolt and the bore hole. Reference may be made to U.S. patent no. 4,601,614, titled: 'Rockboit', for installation in a bore in the roof of an underground excavation, such as a tunnel or mine, to support the roof, comprises a sleeve having a closed top and ports in its upper end, a plunger slideably mounted in the sleeve, and hardenable binder material encapsulated in burst able cartridges in the sleeve above the plunger. The rockboit is inserted into the bore and the plunger is operated either mechanically or by the application of pressurized fluid to the plunger, to extrude the binder material to secure the rockboit in the bore. A mechanical anchor can be provided on the top of the sleeve so the rockboit can be tensioned before the binder sets. Alternatively, faster setting binder can be provided in the sleeve below the balance of the binder so that it is the last to be extruded and remains near the top to secure the top to the surrounding rock before the balance of the binder sets so that the rockboit can be tensioned before the balance of the binder sets. The main disadvantage of this system is that it requires an pre-anchoring mechanism prior to the completion of grouting therefore it is a complicated process and requires accuracy of timely executing of different steps involved in installation. It also does not ensure uniform distribution in thickness of grout material along the annular space between the bolt and the bore hole. Reference may be made to U.S. Patent No. 4,650,373, entitled 'Rock bolt construction and installation'. This invention consist of an elongate hollow rock structure and installation wherein the elongated shank of the bolt is hollow and has a series of outwardly bowed side or side portions that are capable of resilient deflection. Fin means are provided in sides or side portion, with the overall span of the fin means being greater than the bolt hole into which the bolt is to be impacted. The pin means are tapered so as to provide for ease of insertion of the bolt. Impaction of the bolt into a mine roof hole provides for a compression loading of the fins of the bolt shank such that these engage the aperture wall in a forced-compression state. Corrosion factors are limited to fin edge contact with the aperture wall of the bolt hole. Resilient sides' deformation at the core of the bolt shank is relied upon to compression load the fins for frictional contact with the aperture wall into which the bolt is inserted. The main disadvantage of this system is that it has a complicated design and requires a separate grout pump which adds to the cost of rock bolting system. This bolt also requires to be inserted by impact-force inside the bore hole. All the above-mentioned inventions are of different rock bolts. The disadvantages of these inventions are in their complicated designs and difficulty in installation. Another disadvantage of these prior arts are that these require very skilled manpower to erect and also very time consuming, which may not be at par with the rate of advance of the mine roadway/ tunnel. Yet another disadvantage of these bolts are that these do not ensure uniform mixing of the grout materials. Still another disadvantage of these bolts are that these do not ensure uniform distribution in thickness of grout material along the annular space between the bolt and the bore hole. Another drawback of these bolts is that if the grout material is a cement / resin capsule then the polyethylene pack containing the grout material prevents proper contact between the bolt and the side-walls of the bore hole thereby creating a weak zone. Yet another drawback of these bolts are that many a times it has been found that the bolt is not in the center line of the bore hole which again is the main cause of the irregular distribution of the grout material. Another negative aspect of some of these bolts are requirement of impact hammering (U.S. Patent No. 4650373, 4295760, 4,666,345) to insert into the bore hole as the protruding fins are of larger diameter. Moreover these are very costly bolts. Hence, it is clear from the hitherto known prior art that there is a definite need to provide a rock bolt which can easily and reliably ensure a proper supporting system in mine / tunnel roofs/sides. The main object of the present invention is to provide a rock bolt for reinforcing rock strata in a mine / tunnel roof / side which obviates the drawbacks of the hitherto known prior art as detailed above. Another object of the present invention is to provide a rock bolt which is a reinforcing long bolt for supporting several rock strata in a mine / tunnel roof / side. Yet another object of the present invention is to provide a rock bolt useful for strengthening layers of rock in a mine or a tunnel roof or side. Still another object of the present invention is to provide a rock bolt which is capable of holding and stitching rock layers when used in combination with a known grouting medium, which may be composed of cement or resin. Still yet another object of the present invention is to provide a rock bolt which is capable of holding itself straight into a previously drilled borehole in the rock layers and thereby ensure a uniform grout distribution in the annular space between the bolt and the rock. A further object of the present invention is to provide a rock bolt which is a reinforcing long bolt useful for supporting mine roof/ tunnels having simple design, easy to manufacture, cheap and easy installation procedure, which obviates the drawbacks of the above noted hitherto known prior art. In the present invention there is provided a rock bolt useful for reinforcing several rock strata in a mine or tunnel roof or side, which comprises in combination a rock bolt, bearing plate and a nut. The combination consisting of an elongated cylindrical rod the peripheral body of which being provided along its length with a plurality of pairs of pointed and inclined web protrusions placed diametrically opposite to each other. The protrusions in form of elongated stud or a web act as guides to align the bolt inside a hole in a multi-layered rock strata and enable tearing of polyethylene packets of grout material into shreds, mix the grout material uniformly and distribute the grout material uniformly along the annular space. The elongated cylindrical rod is having a pointed upper end and a threaded lower end. The threaded portion of the said rod being provided with a removable co-centric bearing plate having a central hole of diameter less than the rod but more than the threaded portion, thus ensuring proper alignment of the bolt in a previously drilled bore-hole This enables holding of the bolt straight in a borehole in the rock layers and thereby ensure a uniform grout distribution in the annular space between the bolt and the rock. The threaded portion being provided with at least one removable nut having peripheral diameter greater than the central hole of the said bearing plate. This bolt will be able to hold and stitch multi rock layers when used in combination with a known grouting medium, which may be composed of cement or resin. The rock bolt of the present invention is simple to manufacture, easy to install and cheaper in cost. Accordingly the present invention provides a rock bolt for reinforcing rock strata in a mine /tunnel roof / side, which comprises in combination a rock bolt, bearing plate and a nut; the said combination consisting of an elongated cylindrical rod the peripheral body of which being provided along its length with a plurality of pairs of pointed and inclined web protrusions placed diametrically opposite to each other, the said rod having a pointed upper end and a threaded lower end, the threaded portion of the said rod being provided with a removable co-centric bearing plate having a central hole of diameter less than the rod but more than the threaded portion, the said threaded portion being also provided with at least one removable nut having peripheral diameter greater than the central hole of the said bearing plate. In an embodiment of the present invention, the elongated cylindrical rod is ribbed or un-ribbed, of diameter in the range of 20 to 22 mm (3) and of length of the order of 1.8 m or more as required. In another embodiment of the present invention, the peripheral body of the elongated cylindrical rod is provided along its length with a plurality of pairs of pointed and inclined web protrusions at intervals of the order of 30 cm. In still another embodiment of the present invention, the peripheral body of the elongated cylindrical rod is provided along its length with a plurality of pairs of pointed and inclined web protrusions having depth of less or equal to 3 mm with sharp edges. In yet another embodiment of the present invention, the pointed and inclined web protrusions are inclined at an angle of 20 to 30° with respect to the center line of the rod. In still yet another embodiment of the present invention, the rod is having a pointed upper end which is symmetrically pointed or cut in an inclined manner. In a further embodiment of the present invention, the rod is having a threaded lower end of length in the range of 125 to 150 mm. In a still further embodiment of the present invention, the threaded portion of the said rod being provided with a removable trough shaped square bearing plate having a central hole of diameter less than the rod but more than the threaded portion. In a yet further embodiment of the present invention, the threaded portion of the said rod being provided with one or more removable lock-nut(s). In figures 1 to 6 of the drawings accompanying this specification an embodiment of the rock bolt of the present invention for reinforcing rock strata in a mine / tunnel roof / side is illustrated. In figure 1 is shown the bolt (3) which is an elongated cylindrical rod which maybe ribbed or un-ribbed having diameter in the range of 20 to 22 mm and of length of more than 1.8 m or as required in the specific area depending on the multi-layered rock strata. One end of the rod being pointed or cut in an inclined manner (1). The other end of the rod being threaded (4). The threaded length (4) may vary from 125 to 150 mm. The peripheral body of the rod being provided along its length at intervals of 30 cm with a plurality of pairs of pointed and inclined web protrusions (2) placed diametrically opposite to each other. The pointed webs/protrusions (2) are inclined at an angle of 20 to 30° with the center line of the rod. The depth of these webs will be less than equal to 3 mm so that the bolt can easily be pushed into the bore hole. Figure 2 of the drawing represents the cross-section of the bolt with the webs (5) protruding out in four directions. Figure 3 and 4 represents the top view and elevation respectively of the bearing plate (6) of thickness of the order of 6 mm, 150 mm square made up of mild steel. The bearing plate has a hole in the center to accommodate the threaded portion (4). The diameter of this center hole should be less than the diameter of the rod (3) but more than the diameter of the threaded portion (4). The bearing plate is preferably trough shaped (6) in such a manner to provide a firm grip on the roof of the mine/ tunnel. Figure 5 and 6 represents the top view and elevation respectively of the steel hexagonal nut (7) of thickness of the order of 20 mm. The nut should be large enough so that it does not pass through the central hole of the bearing plate. In the present invention the protruded pointed webs (2) are such that it will just fit into the bore-hole pre-inserted with wet cement capsule or resin capsules. The webs cut the polyethylene packs and mixes the grout material due to rotary movement of the drill machine by which it is pushed into the bore-hole. It also aligns the rod straight along with the bore-hole. In the present invention the trough shaped square bearing plate will provide a firm grip on the rough roof surface of a mine / tunnel. More the pressure on the bearing plate (6) more it will exert pressure on the roof. The novelty of the rock bolt of the present invention for reinforcing rock strata in a mine / tunnel roof / side, resides in its usefulness for reinforcement of a multi-layered rock strata several rock layers, through simple cost-effective constructional features and ease of installation requiring less manpower, less electricity cost and having low cost of manufacture. Another novelty of the present invention is that it does not require very skilled labour in installation. It will also take less time to install, which may be at par with the rate of advance of the mine roadway/ tunnel Yet another novelty of the present invention is that this bolt ensures uniform mixing of the grout materials as a result there will be a homogeneous strength in the grout to bind the bolt and the rock layers. The novelty of the rock bolt of the present invention for reinforcing rock strata in a mine / tunnel roof / side, has been realized by the non-obvious inventive step of providing in combination a rock bolt, bearing plate and a nut; wherein the said combination consists of an elongated cylindrical rod the peripheral body of which being provided along its length with a plurality of pairs of pointed and inclined web protrusions placed diametrically opposite to each other. In the hitherto known prior art, there are no such pointed webs / protrusions which act as cutters/mixers. The presence of these sharp edged and angled cutters in form of webs (2) enables cutting of the polyethylene packets of cement / resin capsule into shreds. In the present invention the pre-inserted cement capsules are cut into minute pieces and therefore mixed properly to give a homogenous grout mechanism. The following example is given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of the present invention. Example-1 Rock bolts of the present invention for reinforcing rock strata in a mine / tunnel roof / side in accordance with the present specification were manufactured as mentioned in figures 1 to 6 of the drawings. Field trials in various mines in Jharia coalfield were conducted. The trials were conducted along with the available other bolts in the market. This comparative study was made to evaluate the performance of the present invention. The results of the experiments such as installation and load bearing capacity of this bolting mechanism at different mines was studied and are detailed below. Pneumatic roof bolters were used to make the bore-holes in the mine roof and after inserting the grouting material the roof bolt was pushed in the bore-hole giving a rotary motion by a drill machine. After the required setting time physical tests were done. Some of the bolts were tested to check the load bearing capacity. In others core drilling was done to recover the bolt along with the grout materials as set during installation. It was found that the bolts of the present invention gave better load bearing capacity by 3 to 4 T more than the other bolts. The cores were studied further for other details. The bolts of the present invention were found to be perfectly aligned along with the bore hole as the protrusions / webs on the bolts provided the required support to maintain uniform annular space in the bore hole. The plastic packets of the grout materials were turned into shreds during rotary movement of the bolt therefore the contact of the grout between the bore-hole and the bolt improved considerably which helped in increase of the load bearing capacity. The main advantages of the rock bolt of the present invention for reinforcing rock strata in a mine / tunnel roof / side are: 1. Simple design, which can be easily and reliably manufactured and installed using the same prevailing installation techniques. 2. Ensures uniform mixing of the grout materials to give a homogeneous strength in the grout to bind the bolt and the rock layers. 3. Ensures proper severing of polyethylene packs to avert chances of weak layers in the grout after curing. 4. Ensures proper alignment of the bolt in the bore-hole. 5. Ensures uniform thickness of the grout material in the annular space between the bore-hole and the bolt. 6. Ensures better and strong contact / bonding strength between the bolt and the rock layers. We claim: 1. A rock bolt for reinforcing rock strata in a mine / tunnel roof / side, which comprises; characterized by providing in combination a rock bolt, bearing plate and a nut; the said combination consisting of an elongated cylindrical rod, the peripheral body of which being provided along its length with a plurality of pairs of pointed and inclined web protrusions placed diametrically opposite to each other, the said rod having a pointed upper end and a threaded lower end, the threaded portion of the said rod being provided with a removable co-centric bearing plate having a central hole of diameter less than the rod but more than the threaded portion, the said threaded portion being also provided with at least one removable nut having peripheral diameter greater than the central hole of the said bearing plate. 2. A rock bolt as claimed in claim 1, wherein the elongated cylindrical rod is ribbed or un-ribbed, of diameter in the range of 20 to 22 mm (3) and of length of the order of 1.8 m or more as required. 3. A rock bolt as claimed in claims 1-2, wherein the peripheral body of the elongated cylindrical rod is provided along its length with a plurality of pairs of pointed and inclined web protrusions at intervals of the order of 30 cm. 4. A rock bolt as claimed in claims 1-3, wherein the peripheral body of the elongated cylindrical rod is provided along its length with a plurality of pairs of pointed and inclined web protrusions having depth of less or equal to 3 mm with sharp edges. 5. A rock bolt as claimed in claims 1-4, wherein the pointed and inclined web protrusions are inclined at an angle of 20 to 30° with respect to the center line of the rod. 6. A rock bolt as claimed in claims 1-5, wherein the rod is having a pointed upper end which is symmetrically pointed or cut in an inclined manner. 7. A rock bolt as claimed in claims 1-6, wherein the rod is having a threaded lower end of length in the range of 125 to 150 mm. 8. A rock bolt as claimed in claims 1-7, wherein the threaded portion of the said rod being provided with a removable trough shaped square bearing plate having a central hole of diameter less than the rod but more than the threaded portion. 9. A rock bolt as claimed in claim 1, wherein the threaded portion of the said rod being provided with one or more removable lock-nut(s). 10. A rock bolt for reinforcing rock strata in a mine / tunnel roof / side, substantially as herein described with reference to the example and figures 1 to 6 of the drawings accompanying this specification.

Documents:

362-del-2005-Abstract-(07-06-2013).pdf

362-del-2005-abstract.pdf

362-DEL-2005-Claims-(05-08-2011).pdf

362-del-2005-claims.pdf

362-DEL-2005-Correspondence Others-(05-08-2011).pdf

362-del-2005-Correspondence-Others-(07-06-2013).pdf

362-del-2005-correspondence-others.pdf

362-del-2005-description (complete).pdf

362-del-2005-drawings.pdf

362-del-2005-form-1.pdf

362-del-2005-form-18.pdf

362-del-2005-Form-2-(07-06-2013).pdf

362-del-2005-form-2.pdf

362-DEL-2005-Form-3-(05-08-2011).pdf

362-del-2005-form-3.pdf

362-del-2005-form-5.pdf