ABSTRACT:

Three series of tests were carried out in laboratory on rock and concrete specimens to validate test protocols, verify the capabilities of the testing system, and determine the hydraulic and poroelastic properties of test specimens. Specimen porosity ranged between 1 and 23%. Pore pressures up to 5 MPa and temperatures up to 175°C were achieved during single-phase steady-state flow experiments on water-saturated specimens. Hydraulic conductivities down to 10-10 cm/sec were measured. Testing conditions are described, and results are discussed and compared with those published in literature.

1. INTRODUCTION

Three series of tests were carried out in laboratory on five lots of porous rock and concrete specimens to determine their physical, mechanical, hydraulic and poroelastic properties. Tests were carried out at the CANMET-MMSL rock mechanics laboratory located in Ottawa. Most of the tests discussed in this paper are well-known to geotechnicians and practitioners active in hydrogeology and petroleum engineering, involved in the production or the underground storage of gas and other energy fuels [1-3]. Similar pressure and temperature conditions, with elevated gradients, are also found in geothermal deposits and volcanic domes located near the earth?s surface. Hydraulic and poroelastic properties are needed to analyze their conditions of stability, or before proceeding with mineral extraction [4-7]. Tests were carried out on samples provided by external clients or gathered by the laboratory for the test program. Tested materials included Indiana limestone, Nepean and Potsdam sandstone, a volcanic breccia and highperformance concrete specimens. Mechanical properties determined consisted of triaxial strength and deformation moduli under drained and undrained conditions. The hydraulic properties of test specimens at various confining and temperature levels constituted another set of properties determined. The execution of the test program allowed laboratory test protocols to be updated and validated, and to proceed to the evaluation of the performance of the testing system. Test protocols, properties investigated and results are presented and discussed in the paper.

2. REVIEW OF POROUS ROCK PROPERTIES

The properties determined during the test program can be grouped into four (4) main categories. These are:

  • The physical properties of materials, e.g. density and porosity, including the properties of the fluid used during the experiments;

  • The hydraulic properties, e.g. the hydraulic conductivity and the intrinsic permeability;

  • The bulk and shear elastic moduli, determined through standard drained and undrained triaxial compression tests. Tests were continued until failure during the last stage of testing to determinethe ultimate strength of specimens; and

  • The poroelastic constants, e.g. the Biot and Skempton coefficients, and the coefficients for coupling hydraulic and mechanical (H-M) properties during poroelastic analyses, e.g. the Biot modulus and the hydraulic diffusivity.

2.1. Physical properties

Material density, ¿, and unit weight, ¿, are determined according to the conditions of saturation, e.g. dry, wet or natural, or saturated. Conditions under which samples are retrieved from drillholes or prepared in laboratory are referred to as natural conditions [8-10]. The porosity, n, is the ratio of the volume of the voids, VV, to the total volume of the specimen, VT, expressed either as a fraction ranging from 0 to 1, or in percent.

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