| Popis: |
In situ pressuremeter creep tests of ice require that particular attention be paid to the precision with which the borehole diameter is measured because failure of ice often occurs at strains as small as 1%. Therefore, precision is important to obtain an accurate picture of the stress-strain-time response of the ice before failure. Also, the pressure applied to the ice must be known precisely since the creep rate varies as the cube of the stress. Thus, careful calibration of the pressuremeter is necessary. This paper outlines how a monocellular pressuremeter equipped with an internal caliper should be calibrated to take into account freezing temperatures and the long duration of creep tests. The probe in question contains a two-arm caliper system which determines the diameter of the probe electromechanically; this system must be calibrated before each test. Secondly, both the thickness and resistance of the rubber membrane must be known at any stage of a test; both are dependent on temperature, internal probe pressure, displacement, and elapsed time. The paper also discusses preferred test procedures. |
