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Computer controlled volumetric strain measurements in metadolerite

  • A. Cipullo
  • W. White
  • I. K. Lee
Article

Abstract

A new volumetric strainmeter system has been developed for the measurement of true volumetric strains occurring in selected fresh and decomposed rock samples tested under computer controlled triaxial loading conditions.

The system is capable of resolving volume adjustments of the confining medium to within ±2.8 mm3 and maintain confining pressure deviations to ± 6.9 kPa. The results of the investigation have shown the inadequacy of the commonly used strain gauge method to represent the volumetric strains occurring in the whole of the test specimen and they have provided further experimental evidence for the continuity concept in the fracture mechanism of rocks. Even in the most decomposed samples tested, crack initiation and propagation starts at lower stress levels than previously recognised, in contrast to the generally accepted concept of critical stress levels which characterise and define the process of brittle fracture propagation in rocks.

Keywords

Drill Hole Volumetric Strain Triaxial Test Radial Strain Volume Recovery 

Mesure volumétrique des déformations dans une métadolérite par ordinateur

Résumé

Un nouvel appareil destiné à contrôler les déformations volumétriques a été mis au point pour mesurer les véritables différences de volume se produisant sur un échantillon de roche comprimé dans les trois axes sous contrôle d'un ordinateur.

L'appareil est capable de mesurer des différences de volume en milieu confiné de l'ordre de ±2,8 mm3, et de garder une pression du milieu entre ±6,9 kPa. Les résultats de ces investigations ont montré le manque de précision de la méthode usuelle pour représenter les volumes des déformations se développant dans l'échantillon et elles ont permis de confirmer par des expériences le principe des mécanismes de rupture des roches.

Même dans les essais d'échantillons plus altérés, l'origine des fissures et leur développement commencent sous des contraintes inférieures à celles prévues, contredisant ce qui est généralement admis.

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Copyright information

© International Assocaition of Engineering Geology 1985

Authors and Affiliations

  • A. Cipullo
    • 1
  • W. White
    • 2
  • I. K. Lee
    • 2
  1. 1.Empire CentreGeotechnical Control OfficeKowloonHong Kong
  2. 2.School of Civil EngineeringThe University of New South Wales, Royal Military CollegeDuntroonAustralia

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