Metoda identyfikacji ciągłości wklejenia żerdzi kotwiowych w górotworze

• Autorzy: Staniek A.

Warianty tytułu

EN

Method for identification of continuity of resin layer of rock bolts

• Języki publikacji: PL

Abstrakty

PL

W artykule przedstawiono metodę identyfikacji nieciągłości wklejenia żerdzi kotwiowych w górotworze. Metoda polega na wymuszeniu drgań badanego obiektu młotkiem udarowym i eksperymentalnej analizie modalnej. Otrzymane częstości własne porównywane są z wynikami teoretycznej analizy modalnej realizowanej na modelu elementów skończonych badanego obiektu dla różnych warunków brzegowych odpowiadających różnym przypadkom nieciągłości wklejenia Omówiono wyniki badań prowadzonych w warunkach stosowania obudowy kotwiowej dla przypadków o znanej i nieznanej długości wklejenia Przeprowadzono również analizę statystyczną otrzymanych wyników oraz przedsta-wiono wnioski końcowe.

EN

A rock bolt which is grouted underground may not be properly inserted with the result of discontinuity of a cement layer surrounding it. Such discontinuity may also occur in working conditions due to typical rock behavior and displacement. It may be very hazardous to mine safety. In this paper a method for non-destructive identification of discontinuity of a resin layer surrounding rock bolt is presented. The method uses modal analysis procedures and is based on an impact excitation where a response transducer is positioned at a visible part of a rock bolt. As an installed rock bolt acts as an oscillator, different length of discontinuity of resin layer changes its modal parameters. By proper extraction of these parameters, from which a resonant frequency is seen as most valuable, the intended identification is possible. At the first phase of research work measurements and analyses were performed in laboratory conditions on models with different types of discontinuity of a cement layer. A special stand was prepared and rock bolts were grouted into cement cylinders of different lengths and clinched to a 20-t foundation. Though there was a good correlation between obtained results, quite large interaction with supporting elements was observed. Not being unexpected it proved that such laboratory conditions can not be used as a reference for in situ measurements. What also was gained from laboratory measurements and analysis was the fact that most significant role in identification of different lengths of discontinuity of a resin layer, which form boundary conditions, play natural frequencies. Damping does not convey satisfactory information on that subject and may vary to a certain degree from sample to sample overshadowing its proper usefulness. Since tests in real conditions must be performed on relatively short length of a rock bolt, a mod shape usage was also constrained. One of the obstacles in making in situ measurements, especially in severe mine conditions, is lack of a relatively low cost apparatus used for acquiring and recording data These severe conditions are frequently met in coal mines where rock bolts are installed to support roof strata Because of this inventing and constructing of a portable measurement system was realized. As a programming tool the Lab VIEW program was used and as hardware a DAQ card installed on a laptop platform and worked out conditioning signal unit were introduced to the measurement chain. As a continuation of laboratory measurements and analysis relevant tests were performed at an experimental coal mine underground. One of technical problems was proper insertion of a rock bolt into a drill hole with known length and placement of its discontinuity. After overcoming this obstacle underground tests were realized and through relevant analysis the modal parameters, especially natural frequencies, were derived. The experimental setup is shown in Figure 3.

Słowa kluczowe

PL

górotwór; żerdź kotwiowa

EN

rock bolt; resin layer

• Wydawca: Główny Instytut Górnictwa
• Czasopismo: Prace Naukowe GIG. Górnictwo i Środowisko / Główny Instytut Górnictwa
• Rocznik: 2005
• Tom: nr 3
• Strony: 111--134
• Opis fizyczny: Bibliogr. 21 poz.

Twórcy

autor

Staniek A.

• Główny Instytut Górnictwa, Zakład Akustyki Technicznej, Techniki Laserowej i Radiometrii, Plac Gwarków 1, 40-166 Katowice, tel. [phone],

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