Method of testing the integrity of installed rock bolts
AssigneeGeneral Electric Company
InventorsDavid E. Godfrey, Norman R. Kuchar
Life of this patent
Estimating the term…
Abstract
The bond integrity of resin grouted rock bolts or roof bolts anchored within the ceiling in underground mines is tested by inducing broadband vibrations and measuring the resonant frequencies of the axial and transverse vibration modes. Voids in the resin grout or imperfect bonding cause shifts in the resonant frequencies. The tension in expansion nut rock bolts is determined from the resonant frequency of the transverse vibration mode.
Claims8
A method of testing the integrity of the anchoring of a rock bolt anchored within an elongated hole in a rock-like substance and having an externally accessible base comprising the steps of
- striking the base of said rock bolt to induce acoustic vibrations therein and excite at least one selected vibration mode thereof,
- sensing the vibrations of said rock bolt and generating an electrical signal representative of said vibrations, and
- measuring the amplitude of said electrical signal at a plurality of discrete narrow frequency bands covering a predetermined frequency range and deriving the resonant frequency of said selected vibration mode as an indication of the integrity of the anchoring of said rock bolt.
A method of testing the bond integrity of a rock bolt bonded by resin grout within an elongated hole in rock strata and having an externally accessible base comprising the steps of
- striking the base of said rock bolt to induce broadband acoustic vibrations therein and excite the axial and transverse vibration modes thereof,
- sensing the vibrations of said rock bolt and generating an electrical signal representative of said vibrations, and
- measuring the amplitude of said electrical signal at a plurality of discrete narrow frequency bands covering a predetermined frequency range and deriving the resonant frequency of each vibration mode as an indication of the effective bonded bolt length and axial length of voids in said resin grout.
A method of testing the tension of a rock bolt having one end anchored by means of an expansion nut within an elongated hole in rock strata and having an externally accessible base comprising the steps of
- striking the base of said rock bolt to induce broad band acoustic vibrations therein and excite the transverse vibration mode thereof,
- sensing the vibrations of said rock bolt and generating an electrical signal representative thereof, and
- measuring the amplitude of said electrical signal at a plurality of discrete narrow frequency bands covering a predetermined frequency range and deriving the resonant frequency of said transverse vibration mode as an indication of the tension in said rock bolt.
Dependencies are inferred from the claim text.