ABSTRACT:

The borehole slotting stress meter, originally developed at James Cook University, Townsville/Australia, is now commercially available through INTERFELS GmbH. When compared with the University"s prototype the Interfels equipment has been improved in a number of points. These improvements are briefly outlined. New fields of application of borehole slotting have been opened up by INTERFELS Testing Services in the years 1990–91. They include testing of old masonry brick tunnel linings on its actual state of stress, delineation of the distribution of loads in the foundations of buildings and the in-situ determination of the extent of the plastic zone in underground construction.

RESUME:

La sonde à fente pour forages, developee à l"origine par l"Universite James Cook, Townsville/Australie, a ete mis sur le marche par la maison INTERFELS GmbH en 1990. En comparaison du prototype de l"Universite James Cook, INTERFELS a effectue une serie des ameliorations relatif à la sonde et le système, quelles sont expliquees brièvement. On a ouvert des nouveaux champs d"application pour la sonde à fente. Ils comprennent entre autres des mesures de tension dans la maçonnerie des tunnels anciens de chemin de fer pour determiner l"etat de charge actuel, des etudes relatif à la distribution des charges de fondation des batiments anciens et des determinations en ce qui concerne l"extension de la zone plastique en construction souterraine.

ZUSAMMENFASSUNG:

Die Bohrlochschlitzsonde, urspruenglich an der James Cook Universitat, TownsVille/Australien entwickelt, wurde 1990 von der INTERFELS GmbH auf dem geotechnischen Markt eingefuehrt. Im Vergleich zu dem James Cook Prototypen wurde von der INTERFELS eine Reihe von Verbesserungen an Sonde und System vorgenommen, die kurz erlautert werden. Neue Anwendungsfelder fuer das Bohrlochschlitzen wurden erschlossen. Diese umfassen u. a. Spannungsmessungen im Mauerwerk alter Eisenbahntunnel zur Ermittlung des aktuellen Belastungszustandes, Untersuchungen zur Verteilung von Gruendungslasten alter Gebaude und Ermittlungen zur Ausdehnung der Plastischen Zone im untertagigen Felsbau.

1
INTRODUCTION

Borehole slotting is a stress measuring method which is designed for quick operations and high-density stress measurements at reasonable costs. It is a non-over coring method. Its equipment is fully recoverable. The method was developed at the James Cook University of North Queensland (JCUNQ), Townsville/Australia (References 1 - 3). In 1990, borehole slotting services and instrumentation became commercially available through Interfels GmbH in Bad Bentheim/Germany (Reference 6). There are two immediate objectives of this contribution. First the reader should be briefed on some technical features of the Interfels borehole slotting system as it incorporates a number of improvements when compared with the JCUNQ prototype, described earlier in the literature (References 1 - 3). The second objective is to report on some new applications of borehole slotting carried out by the Interfels Testing Services within the period 1990–91. New applications include the determination of the stress state in old tunnel linings, the foundation loads of buildings and the extent of plastified zones in underground openings.

2
THE INTERFELS BOREHOLE SLOTTING SYSTEM

The Interfels borehole slotting system is made up of the following six principal components (see Figure 1). - (1) Borehole probe ("slotter") (2) Electrical control and readout (3) Pneumatic and hydraulic control unit (4) Pressure vessel for cooling water (5) Cables, hoses and accessories such as settingrods (6) Software In the following, a brief description of the system is given. Changes with regard to the JCUNQ prototype are marked, boldface.

2.1
Borehole Probe ("Slotter") (Figures 2 and 3)

The slatter is designed for borehole diameters of 95 to 103 mm. The maximum depth of the standard equipment is 30 m. Suitable for testing are dry boreholes at any inclination. No special preparation of the borehole wall is required.

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