Oval bar

Abstract

The present invention is a manually bendable rebar bolt for use in ground reinforcement, particularly in mining operations. The rebar bolt is a steel rod having a length and a width. The cross-sectional area of the bolt taken along the width generally perpendicular to said length has a long axis and a short axis. The bendable rebar bolt can be manually bent in a direction generally perpendicular to said long axis.

Claims

1. A manually bendable rebar bolt for use in ground reinforcement, said rebar cable bolt comprising: a steel rod having a length and a width and a cross-sectional area taken along said width generally perpendicular to said length, said cross-sectional area having an oval or elliptical shape including a long axis and a short axis; whereby said oval or elliptical shape of said cross-sectional area allows a user to manually bend said steel rod in a direction generally perpendicular to said long axis; wherein a ratio of said short axis to said long axis is at least about 0.6 and less than 0.8; wherein a length of said long axis is less than or equal to 0.9 inches and a length of said short axis is greater than or equal to 0.6 inches.

2. The manually bendable rebar bolt of claim 1, wherein the length of said short axis is about 0.6 inches and the length of said long axis is 0.9 inches.

3. The manually bendable rebar bolt of claim 1, wherein said rebar is #6 grade 40.

4. The manually bendable rebar bolt of claim 1, wherein said long axis is less than 0.9 inches and said short axis is greater than 0.6 inches.

5. A manually bendable rebar bolt for use in ground reinforcement, said rebar cable bolt comprising: a rod having a cross-sectional area, said cross-sectional area having an oval or elliptical shape including a long axis and a short axis, said rebar bolt having a width along said long axis and a width along said short axis; a ratio of said short axis to said long axis is at least about 0.6 and less than 0.8; wherein a length of said long axis is less than or equal to 0.9 inches and a length of said short axis is greater than or equal to 0.6 inches; whereby said oval or elliptical shape of said cross-sectional area allows a user to manually bend said rod in a direction generally perpendicular to said long axis.

6. The manually bendable rebar bolt of claim 5, wherein the length of said short axis is about 0.6 inches and the length of said long axis is 0.9 inches.

7. The manually bendable rebar bolt of claim 5, wherein said rebar is #6 grade 40.

8. The manually bendable rebar bolt of claim 5, wherein said long axis is less than 0.9 inches and said short axis is greater than 0.6 inches.

9. A manually bendable rebar bolt for use in ground reinforcement, said rebar cable bolt comprising: a rod having a length a width and a cross-sectional area taken along said width generally perpendicular to said length, said cross-sectional area having an oval or elliptical shape including a long axis and a short axis, a ratio of said short axis to said long axis is at least about 0.6 and less than 0.8, a length of said long axis is less than or equal to 0.9 inches and a length of said short axis is or equal to 0.6 inches; whereby said oval or elliptical shape of said cross-sectional area allows a user to manually bend said rod in a direction generally perpendicular to said long axis.

10. The manually bendable rebar bolt of claim 9, wherein said rebar is #6 grade 40.

11. The manually bendable rebar bolt of claim 9, wherein said long axis is less than 0.9 inches and said short axis is greater than 0.6 inches.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a partial perspective view of the oval or elliptical bar of the present invention.

(2) FIG. 2 is an end view of the oval or elliptical bar of the present invention.

(3) FIG. 3 is an end view of the bolt installation head of the oval or elliptical bar of the present invention.

(4) FIG. 4 is a schematic view of rollers to roll the oval or elliptical bar of the present invention.

(5) FIG. 5 is a schematic perspective view of the oval or elliptical bar of the present invention.

(6) FIG. 6 is a perspective view of the oval or elliptical bar of the present invention including oval or rebound rebar bolts installed thereon.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

(7) The present invention overcomes the disadvantages of the known methods for making bendable rebar. The present invention provides a preformed oval or elliptical bar 10 having a cross sectional area 20 with a short axis 12 and a long axis 16. The oval or elliptical bar shape is formed while the bar is still in a malleable state. With the deformed rebar formed as an oval or elliptical bar along its length, the bar can be bent along the short axis, i.e. perpendicular to the direction of the long axis, with no additional modifications being required and the processing costs and handling are minimized. The oval cross-section will allow the bolt to be manually bent at any location along the length to suit specific seam height.

(8) The bar exceeds all strength requirements using the ASTM F432-13 standards for yield and tensile strength. By controlling the profile i.e. making it flatter or thinner in the minimum diameter direction, the force needed to bend the bar can be controlled to any desired requirements.

(9) The oval and elliptical bars can also have required bolt installation heads 14, see FIG. 4, forged by traditional forging methods. Although traditional forged heading processes are designed for bars with a circular shape, the present invention is capable of being forged by traditional processes. The bar is heated to the required temperature and then struck to form an initial cone and then again to form the head that is used to facilitate bolt installation in a mine (the head develops the designed bolt capacity). The heads are formed by gathering the material from the oval/elliptical shape and the resulting heads meet all specifications and strength requirements.

(10) A major additional benefit that is realized by forming the bar in an oval shape is the reduced annulus (distance between drilled borehole wall and the bar). This reduced distance creates an installation advantage. The oval shape also creates a paddle shape that facilitates mixing of the resin. The reduced annulus or paddle enhances the tearing of the resin film cartridge and assists with mixing by pushing the resin through a small space. For example in a 1 inch (25 mm) diameter hole the oval bar will have a 0.600 minor axis 12 and a 0.938 inch major axis 16 that results in a 0.062 distance between the borehole wall and the bolt which will result in a vigorous mixing during installation and fast spin cycles along the entire length of the bolt.

(11) The oval or elliptical bar of the present invention is formed by standard rebar forming operations initially. A billet of steel is heated and forced through a series of rollers 18 to from the round shape of the rebar. At the final stage, a further series of rollers 18 form the oval or elliptical shape of the present invention.

(12) Tests were performed to establish that the oval bar of the present invention has equal cross-section and tensile strength as #6 Grade 40 standard rebar, and not lower reinforcement level and volume of steel per in.sup.3.

(13) The initial testing was intended to evaluate head-to-head anchorage capacity of oval bars against current round bars. The short encapsulation pull tests (SEPT) were conducted in the presence of MSHA Tech Support and MSHA District 3.

(14) The Test Conditions and Results:

(15) Two sets of rebar bolts were tested for the SEPT:

(16) Oval Rebar Bolts0.6500.900 Grade 40, 6 ft in length, headed. Mechanical properties of the bar were tensile strength 88,100 ksi and yield strength 54,100 ksi.

(17) Round Rebar Bolts#6 Grade 40, 6 ft in length, headed.

(18) The bolts were installed with 88 flat plates and pull collars, and B23 M35LIF resin (as shown in FIG. 6).

(19) The resin cartridges were cut to 9.5 for 12 grout coverage.

(20) Results and Observations:

(21) All of the bolts were pulled to nine (9) tons. The data showed that the oval bolts performed equal or better than standard round bars without excessive permanent displacement.

CONCLUSION

(22) The oval bolts performed equal or better than standard #6 Grade 40 round bar bolts.

(23) In a further test by MSHA, a full spectrum of tests was conducted on both oval rebars and #6 Grade 40 hot notched rebars for conformance to ASTM F432-13. The conclusions reached were both oval and round rebar bolts exceeded ASTM F432-13 standard for Grade 40 for yield and tensile loads.

(24) The hot notched section of the round #6 Grade 40 bolts conformed to the standard for minimum breaking load after bending and straightening. Bent and straightened oval rebars performed identical to the original sections. Breaking loads of hot notched bars were lower than oval bars, reflecting the detrimental effect of reheating of the steel.

(25) Overall, oval rebar bolt passed all the tests to be considered as replacement to notched rebar bolts. The oval bars also met all requirements of a #6 Grade 40 resin bolt.

(26) The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and do come within the scope of the invention. Accordingly, the scope of legal protection afforded this invention can only be determined by studying the following claims.