METHOD FOR INVESTIGATING AN ANCHORED ROD-LIKE BODY HAVING AN ACCESSIBLE END, AND APPARATUS FOR CARRYING OUT THE METHOD

摘要

ABSTRACTThis invention relates to a method and apparatus for investigating arod-like body which is anchored in a surrounding material and which has anaccessible end, for determining the state of the anchorage of the body and itslength. It has long been known in the art that elastic oscillations of amultiplicity of different wave types can be used to determine the state of boltsand other anchors. However, there is a problem in the present art in that theoscillations are highly dampened. The present invention provides the advantageof having oscillations with a much lower damping effect and which do not pro-pagate in bore hole mud. Transient elastic oscillations are excited in theaccessible end of the body. The oscillations comprise a flexural wave causinga deformation of the body varying with respect to amplitude and phase over thecross-section of the body. The flexural wave propagates in the longitudinaldirection of the body and is partially reflected at discontinuities of the bodyand/or the anchorage. Transient elastic oscillations comprising flexural wavesreflected at such discontinuities and returning to the accessible end of the bodyare received and detected. The position and magnitude and/or type of at leastsome of the discontinuities are estimated with the aid of time-position andamplitude of the reflected flexural waves. Discontinuities of interest are thebeginning and end of anchorage, the end of the body and possible cracks orfractures in the body and/or its anchorage. The method and the apparatus areprimarily intended for in-situ investigation of concrete-bond rock anchors (bolts)although the method and apparatus can be used for at least partially investi-gating other anchored rod-like bodies.