Broad Band Attenuation Vessel

Broad Band Attenuation Vessel (BBAV) BBAV measures wave attenuation at frequencies below 100 Hz. BBAV employs the phase shift method to measure seismic wave attenuation for strain around 1e-6. Maximum size of the sample is 76 mm in diameter and 250 mm in length. The sample can be confined up to 25 MPa. The BBAV has an hydraulic circuit to saturate the sample and to vary the pore pressure up to 20 MPa. Due to the decimetric size of the sample, the machine can perform another kind of experiment: a series of zero-volume mini-pressure sensors (i.e. the sensitive part of the sensor is extremely close to the pores of the rock), can be inserted in the plug to investigate the pore pressure evolution when the stress field changes. This test aims to reproduce numerical experiments calculating the fluid flow at the mesoscopic scale on a rock column partially saturated with liquid and gas. This is done in order to estimate the influence of attenuation due to wave-induced fluid flow on the attenuation measured in our laboratory experiments, i.e. when all possible physical mechanisms take place simultaneously.

Reference

TISATO N. & MADONNA C. (2012) Attenuation at low seismic frequencies in partially saturated rocks. Measurements and description of a new apparatus. Journal of Applied Geophysics, 86, 44-53. external page http://dx.doi.org/10.1016/j.jappgeo.2012.07.008