The TRI-MOD-S Rock Pressuremeter (Flexible Dilatometer) is a reliable and effective tool used to measure in-situ the strength and stress-strain properties of very stiff soil and rock. It quickly and economically provides a large volume of data encompassing the variability of the geotechnical conditions on a site.
The TRI-MOD-S is comprised of the following components:
The probe: a single cylindrical cell hydraulically inflated with 6 strain gauges and cantilevered arms, and fitted with an inflatable metallic sheath
The hydraulic manual pump
The pneumatical cylinder for deflating the probe
The tubing and electrical cable
Two calibration tubes
The probe is placed at the test depth in a pre-cored borehole. Stress-control is used to run the test. Equal increments of pressure are applied to the probe and held constant for one minute. The diametric changes are logged 30 and 60 seconds after each pressure step is reached. Unload/reload cycles can be performed.
In situ stress-strain curves are obtained by plotting the changes in each of the 3 instrumented diameters or their average against pressure.
The modulus of deformation E used to calculate settlement is given by:
E = (1 + n) (ΔP/ΔR) R
where: n = Poisson’s ratio
ΔP = Corrected increase in pressure
ΔR / R = Relative change of radius
In softer materials, the limit pressure PL, which is the pressure corresponding to the doubling of the volume of the initial cavity,
The TRIMOD-S comes as a complete kit including, the probe, the hydraulic manual pump, the pneumatical cylinder for deflating the probe, the datalogger, the tubing and the electrical cable and two calibration tubes can be estimated.