PRESSUREMETER INTERPRETATION FOR WEAK ROCK . FIELD TESTING IN ENGINEERING GEOLOGY. PROCEEDINGS OF THE TWENTY-FOURTH ANNUAL CONFERENCE OF THE ENGINEERING GROUP OF THE GEOLOGICAL SOCIETY, SUNDERLAND POLYTECHNIC, SEPTEMBER 4-8 1988

This paper examines some of the concepts which should be applied to pressuremeter test interpretation in weak rock, with particular emphasis on the influence of tensile cracking caused by instrument expansion within the rock. The development of tensile cracking is reviewed first, followed by a description of the finite element modelling technique used to illustrate the effects of radial cracking on pressuremeter pressure-radial strain curves. The model is applied to two examples. The first models a pressuremeter test carried out in a moderately weathered mudstone with a saturated water content, W, of 8%, and an effective in situ stress of 200 kPa. An 8 degree effective angle of dilation was assumed. The resulting pressure volumetric strain curve is illustrated and the volumetric strain calculated from the change in overall volume of the cavity during tests. Analysis of shear modulus was also carried out for the same conditions and properties, but with values of effective in situ horizontal stresses in the 10 kPa-1500 kPa range. Tests were also carried out on softer mudstone (W=13%). In situ horizontal stress values were determined for each of the simulation examples using the stronger mudstone. The second example was carried out for a very stiff clay. The results show that in mudstone the formation of radial cracks: (a) produce a pressiometer response, that is less stiff than if no cracks had occurred; (b) greatly affects values for in situ horizontal stress. Little cracking occurred in the clay, and these cracks had no significant effect on the pressure-volumetric strain curve. For the covering abstract of the conference see IRRD 832042.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0903317516
• Corporate Authors:

  GEOLOGICAL SOCIETY PUBLISHING HOUSE

  UNIT 7, BRASSMILL ENTERPRISE CENTRE, BRASSMILL LANE
  BATH,   United Kingdom  BA1 3JN
• Authors:
  • JOHNSTON, I W
  • Harberfield, C M
• Publication Date: 1990

Language

• English

Media Info

• Pagination: p. 85-90
• Serial:
  • Publication of: GEOLOGICAL SOCIETY PUBLISHING HOUSE
  • Publisher: GEOLOGICAL SOCIETY PUBLISHING HOUSE

Subject/Index Terms

• TRT Terms: Accuracy; Clay; Conferences; Cracking; Deformation; Evaluation and assessment; Field tests; Finite element method; Instruments for measuring loads or pressure; Mathematical models; Pressiometric probes; Pressure; Rocks; Stiffness; Stresses
• Uncontrolled Terms: Horizontal; Pressiometer
• Subject Areas: Data and Information Technology; Geotechnology; Planning and Forecasting;

Filing Info

• Accession Number: 00607151
• Record Type: Publication
• Source Agency: Transport and Road Research Laboratory (TRRL)
• ISBN: 0-903317-51-6
• Files: ITRD, TRIS
• Created Date: Mar 31 1991 12:00AM