Cable bolts

Abstract

A cable bolt for providing support and balance to a rock mass, comprising: a multi-strand cable having a plurality of steel wires being twisted together, said multi-strand cable having a first end portion for anchoring in a borehole of rock mass and a second end portion for being positioned adjacent to the opening of the borehole, a fixture secured to the second end portion of said multi-strand cable, wherein at least one of the plurality of steel wires is made from steel having as steel composition: a carbon content ranging from 0.20 weight percent to 0.95 weight percent, a silicon content ranging from 0.5 weight percent to 2.0 weight percent, a manganese content ranging from 0.40 weight percent to 1.0 weight percent, a chromium content ranging from 0.0 weight percent to 1.0 weight percent, a sulphur and phosphor content being limited to 0.025 weight percent, the remainder being iron and unavoidable impurities, and said steel has as metallurgical structure: a volume percentage of retained austenite ranging from 4 percent to 25 percent, the remainder being tempered primary martensite and untempered secondary martensite.

1 . A cable bolt for providing support and balance to a rock mass, comprising:
 a multi-strand cable having a plurality of steel wires being twisted together, said multi-strand cable having a first end portion for anchoring in a borehole of rock mass and a second end portion for being positioned adjacent to the opening of the borehole,   a fixture secured to the second end portion of said multi-strand cable,   wherein said cable bolt has energy absorption of at least 20 KJ/m for a cable bolt having a diameter of about 15.4 mm, and at least 30 KJ/m for a cable bolt having a diameter of about 17.8 mm, and   wherein at least one of the plurality of steel wires is made from steel having as steel composition:
 a carbon content ranging from 0.20 weight percent to 0.95 weight percent, 
 a silicon content ranging from 0.5 weight percent to 2.0 weight percent, 
 a manganese content ranging from 0.40 weight percent to 1.0 weight percent, 
 a chromium content ranging from 0.0 weight percent to 1.0 weight percent, 
 a sulphur and phosphor content being limited to 0.025 weight percent, 
 the remainder being iron and unavoidable impurities, 
 and said steel has as metallurgical structure:
 a volume percentage of retained austenite ranging from 4 percent to 25 percent, the remainder being tempered primary martensite and untempered secondary martensite. 
 
   
     
     
         2 . A cable bolt according to  claim 1 , it further comprises a plate for placement between the rock mass and said fixture for tensioning said multi-strand cable relative to the rock mass, said plate defining a plate opening for the passage of said multi-strand cable through said plate. 
     
     
         3 . A cable bolt according to  claim 1  or  2 , wherein said fixture comprises a wedge portion and a corresponding head portion, wherein said wedge portion engages said multi-strand cable and secures said multi-strand cable within said head portion as said wedge portion engages said corresponding head portion for tensioning said multi-strand cable. 
     
     
         4 . A cable bolt according to any one of the preceding claims, wherein said multi-strand cable is partially covered with a sleeve. 
     
     
         5 . A cable bolt according to any one of the preceding claims, wherein at least one of the steel wires has a corrosion resistant coating. 
     
     
         6 . A cable bolt according to any one of the preceding claims, wherein at least one of the steel wires has surface deformation. 
     
     
         7 . A cable bolt according to any one of the preceding claims, wherein the cable bolt has a deformation at fracture of at least 10 cm/m. 
     
     
         8 . A cable bolt according to any one of the preceding claims, wherein the diameter of said multi-strand cable is in the range of 10 to 40 mm. 
     
     
         9 . A cable bolt according to any one of the preceding claims, wherein said multi-strand cable has a preselected length of at least 6 m. 
     
     
         10 . A cable bolt according to any one of the preceding claims, wherein said multi-strand cable is in the form of seven steel wire having a central steel wire and six outer steel wires. 
     
     
         11 . A cable bolt according to  claim 10 , wherein the diameter of the central steel wire is larger than the diameter of the outer steel wires. 
     
     
         12 . A multi-strand cable having a plurality of steel wires being twisted together, the diameter of said multi-strand cable being in the range of 10 to 40 mm,
 wherein said multi-strand cable has energy absorption of at least 20 KJ/m for a cable having a diameter of about 15.4 mm, and at least 30 KJ/m for a cable having a diameter of about 17.8 mm, and   wherein at least one of the plurality of steel wires is made from steel having as steel composition:   a carbon content ranging from 0.20 weight percent to 0.95 weight percent,   a silicon content ranging from 0.5 weight percent to 2.0 weight percent,   a manganese content ranging from 0.40 weight percent to 1.0 weight percent,   a chromium content ranging from 0.0 weight percent to 1.0 weight percent,   a sulphur and phosphor content being limited to 0.025 weight percent,   the remainder being iron and unavoidable impurities,   and said steel has as metallurgical structure:
 a volume percentage of retained austenite ranging from 4 percent to 25 percent, the remainder being tempered primary martensite and untempered secondary martensite. 
   
     
     
         13 . A process of manufacturing a multi-strand cable bolt having energy absorption of at least 20 KJ/m for a multi-strand cable bolt having a diameter of about 15.4 mm, and at least 30 KJ/m for a multi-strand cable bolt having a diameter of about 17.8 mm,
 said process comprising the following steps:   a) selecting a steel wire with steel composition:
 a carbon content ranging from 0.20 weight percent to 0.95 weight percent, 
 a silicon content ranging from 0.5 weight percent to 2.0 weight percent, 
 a manganese content ranging from 0.40 weight percent to 1.0 weight percent, 
 a chromium content ranging from 0.0 weight percent to 1.0 weight percent, 
 a sulphur and phosphor content being limited to 0.025 weight percent, 
 the remainder being iron and unavoidable impurities, 
   b) austenitizing said steel wire above Ac3 temperature between 920° C. and 980° C. during a period less than 120 seconds,   c) quenching said austenitized steel wire between 20° C. and 280° C. during a period less than 60 seconds,   d) partitioning said quenched steel wire between 320° C. and 500° C. during a period ranging from 10 seconds to 600 seconds,   e) cooling down the partitioned steel wire to room temperature,   f) twisting the quenched and partitioned steel wires into a multi-strand cable,   g) cutting the multi-strand cable into a preselected length,   h) adding a fixture to an end portion of said multi-strand cable.   
     
     
         14 . A process of manufacturing a multi-strand cable bolt having energy absorption of at least 20 KJ/m for a multi-strand cable bolt having a diameter of about 15.4 mm, and at least 30 KJ/m for a multi-strand cable bolt having a diameter of about 17.8 mm,
 said process comprising the following steps:   a) selecting a steel wire with steel composition:
 a carbon content ranging from 0.20 weight percent to 0.95 weight percent, 
 a silicon content ranging from 0.5 weight percent to 2.0 weight percent, 
 a manganese content ranging from 0.40 weight percent to 1.0 weight percent, 
 a chromium content ranging from 0.0 weight percent to 1.0 weight percent, 
 a sulphur and phosphor content being limited to 0.025 weight percent, 
 the remainder being iron and unavoidable impurities, 
   b) twisting said steel wires into a multi-strand cable;   c) austenitizing said multi-strand cable above Ac3 temperature between 920° C. and 980° C. during a period less than 120 seconds,   d) quenching said austenitized multi-strand cable between 20° C. and 280° C. during a period less than 60 seconds,   e) partitioning said quenched multi-strand cable between 320° C. and 500° C. during a period ranging from 10 seconds to 600 seconds,   f) cooling down the partitioned multi-strand cable to room temperature,   g) cutting the quenched and partitioned multi-strand cable into a preselected length,   h) adding a fixture to an end portion of said multi-strand cable.