Method and apparatus for re-tensioning a roof bolt in an underground mine

A re-tensionable roof bolt assembly for anchoring a rock strata in an underground mine, comprising:

• a. a roof plate with an opening formed therein;
• b. a roof bolt consisting of a head and a shaft, said roof bolt shaft inserted through said opening in said roof plate and inserted into a bore hole in said rock strata along with a quick-setting resin;
• c. a screw member oriented between said roof plate and the head of said roof bolt, said screw member consisting of an externally threaded portion and a head portion, said screw member further defined to include a central bore having a diameter slightly larger than the diameter of said roof bolt shaft and a slotted first aperture of the same diameter extending radially from said central bore to the exterior of said screw member and extending the full length of both said externally threaded portion and head portion of said screw member thereby effecting a slotted opening;
• d. an internally threaded nut having first and second parallel faces and a plurality of outer sides extending between said faces to define a surface for the application of force to turn said nut and a central bore through said nut perpendicular to said first and second face and featuring a continuous internal thread adapted and sized to complement the threaded portion of said screw member, and wherein said nut is further defined to include a slotted second aperture approximately identical in size and diameter to said slotted first aperture in said screw member;
• e. at least one spacer having first and second parallel faces and an outer edge perpendicular to and extending between said first and second faces, said spacer further defined to include a central bore and slotted aperture approximately identical in size and diameter to said central bore and slotted aperture in said screw member.

A method for re-tensioning a roof plate in an underground mine wherein said roof plate is held by a fixed roof bolt, said roof bolt having a head and a shaft, comprising:

• a. coupling a screw member consisting of an externally threaded portion and a head portion and featuring a central bore having a diameter slightly larger than the diameter of said roof bolt shaft and a slotted aperture of the same diameter extending radially from said central bore to the exterior of said screw member and extending the full length of both said externally threaded portion and said head portion of said screw member, with an internally threaded nut having first and second parallel faces and a plurality of outer sides extending between said faces to define a surface for the application of force to turn said nut and a bore through said nut perpendicular to said first and second face and featuring a continuous internal thread adapted and sized to complement the threaded portion of said screw member, wherein said nut further features a slotted aperture approximately identical in size and diameter to said slotted aperture in said screw member;
• b. placing said coupled screw member and nut around the roof bolt shaft by orienting the slotted aperture around said roof bolt shaft, with the head portion of said screw member oriented toward said roof bolt head while said nut is oriented toward the roof plate of said mine roof;
• and
• c. turning said nut away from said head portion of said screw member such as to bias said base plate against said mine roof, re-tightening said roof bolt.

A method for re-tensioning a roof plate in an underground mine wherein said roof plate is held by a fixed roof bolt, said roof bolt having a head and a shaft, comprising:

• a. coupling a screw member consisting of an externally threaded portion and a head portion and featuring a central bore having a diameter slightly larger than the diameter of said roof bolt shaft and a slotted first aperture of the same diameter extending radially from said central bore to the exterior of said screw member and extending the full length of both said externally threaded portion and head portion of said screw member, with an internally threaded nut having first and second parallel faces and a plurality of outer sides extending between said faces to define a surface for the application of force to turn said nut and bore through said nut perpendicular to said first and second face and featuring a continuous internal thread adapted and sized to complement the threaded portion of said screw member, wherein said nut further features a slotted second aperture approximately identical in size and diameter to said slotted first aperture in said screw member;
• b. placing said coupled screw member and nut around the roof bolt shaft by orienting the slotted aperture around said roof bolt shaft, with the head portion of said screw member oriented toward said roof bolt head while said nut is oriented toward the roof plate of said mine roof;
• and
• c. placing a spacer having first and second parallel faces and an outer edge perpendicular to and extending between said first and second faces, said spacer further defined to include a central bore and slotted aperture identical in size and diameter to said slotted aperture in said screw member, between said roof bolt head and said screw member head portion;
• and
• d. turning said nut away from said head portion of said screw member such as to bias said roof plate against said mine roof, re-tightening said roof bolt.

An apparatus for re-tensioning a fixed roof bolt in an underground mine, said roof bolt having a head and a shaft, said apparatus comprising:

• a. a screw member consisting of an externally threaded portion and a head portion, said screw member further defined to include a central bore having a diameter slightly larger than the diameter of said roof bolt shaft and a slotted first aperture of the same diameter extending radially from said central bore to the exterior of said screw member and extending the full length of both said externally threaded portion and head portion of said screw member thereby effecting a slotted opening;
• b. an internally threaded nut having first and second parallel faces and a plurality of outer sides extending between said faces to define a surface for the application of force to turn said nut and a central bore through said nut perpendicular to said first and second face and featuring a continuous internal thread adapted and sized to complement the threaded portion of said screw member, and wherein said nut is further defined to include a slotted second aperture approximately identical in size and diameter to said slotted first aperture in said screw member;
• c. at least one spacer having first and second parallel faces and an outer edge perpendicular to and extending between said first and second faces, said spacer further defined to feature an annular recess in said first parallel face dimensioned to couple the head of said roof bolt such that said roof bolt head is nested in said recess upon re-tensioning of the roof bolt.