Laboratory geophysics techniques are performed through a new advanced oedometer cell, which allows 3D Electric Resistivity Tomography (ERT) and seismic wave velocity measurements: spatial and temporal variation of electrical properties are monitored under controlled mechanical and hydraulic conditions.
The device has an internal diameter of130 mm, and can accommodate samples up to60 mmin height. The cell has 42 electrodes located on its internal boundary; 16 are equally spaced on the sidewall, and 13 are on each of the base and top plates.
The cell allows drainage via the top and base plates. The drainage system is composed of three concentric nonconductive rings with a few micrometres of tolerance between them, resulting in an equivalent permeability of about 6 x 10-6 m/s.
The Complex Impedance Tomograph used for injecting currents and acquiring potentials was constructed by the Iridium Italy (link) company. It is a very fast acquiring device with a 16 bit resolution. The instrument can perform approximately 200 acquisitions per second (at an operating frequency of 1 kHz) so that it is possible to properly appreciate water content or concentration variations inside samples also for relatively fast transitory phenomena.
The electrical measurements are performed on the basis of a four point measurements scheme. Electrodes placed on the sidewall and plates are used alternatively to inject current and to measure the electrical potential.
After performing a large enough number of independent measurements (~ 800), the electrical conductivity distribution within the sample is estimated with a reconstruction procedure using a commercial software developed by sc-aip, based on a least-squares algorithm with a Tikhonov regularization inversion technique.
Sensors for the measurement of P and S wave velocity are allocated on top and bottom caps of the cell. For S wave measurements cantilever mounted PZT-5A Bimorphs by Morgan Electro-Ceramics (10 by 20 by 0.5 mm3) with a parallel connection are used. The transducers used to generate and receive P waves are a lead zirconate titanate ceramic PZT-5A with a cylindrical shape. The ceramic element is produced by Physik Instrument with a thickness of2 mmand a diameter of8 mm. Both seismic sensors are allocated in an opposite space in the bases and covered by a thin surface of epoxy in order to insulate the piezoceramic from interstitial water.
The equipment was realised in collaboration with Universitat Politècnica de Catalunya.
This new equipment has been used to perform some tests:
as for stationary condition, ERT measurements have been performed to evaluate the degree of saturation. Experiments have been conducted on homogeneous samples compacted at different value of water content. For each sample, ERT and wave velocity measurements have been executed;
as for transient condition, ERT measurements have been used in conjunction with a finite element simulation to infer the water retention curve and the unsaturated hydraulic conductivity of coarse and fine homogeneous samples.
Tests have been used to study the chemical behaviour of geomaterials and to evaluate the clay barriers performances;
Test have been performed on a preconsolidated kaolinite homogeneous saturated sample to valuate the variation of porosity during oedometer test.
Experimental tests have been conducted in collaboration with:
Ph.D. Cesare Comina (Assistant Professor) – Department of Earth science, Università degli Studi di Torino,Turin,Italy
Ph.D. Gabriele Della Vecchia (Assistant Professor) Department of Structural Engineering, Politecnico di Milano,Milan,Italy
Current status of the research
Nowadays, a new 3D ERT oedometer cell is building, in collaboration with Universitat Politècnica de Catalunya. The new cell will allow performing tests on unsaturated soils controlling either matric or total suction, through the axis-translation technique or vapour transfer technique, respectively.
Arato, Alessandro; Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Godio, Alberto; Musso, Guido
In: Geotechnical and Geophysical Site Characterization 4
CRC Press (Taylor & Francis Group)
4th International Conference on Site Characterization, ISC'4 (Pernambuco; Brazil) 18-21 September 2012
Vol.2 pp.8 (pp.1789-1796)
Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Musso, Guido
GEOTECHNIQUE
Thomas Telford
Vol.62 pp.12 (pp.583-594) ISSN:0016-8505 DOI:10.1680/geot.10.P.066
Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Musso, Guido; Comina, Cesare
In: Titolo volume non avvalorato
Incontro Annuale dei Giovani Ingegneri Geotecnici IAGIG (Salerno (Italia)) 27-28 Maggio 2011
Comina, Cesare; Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Musso, Guido
ACTA GEOTECHNICA
Springer
Vol.6 pp.9 (pp.195-203) ISSN:1861-1125 DOI:10.1007/s11440-011-0146-3
Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Musso, Guido
In: Innovazione tecnologica nell'ingegneria geotecnica
Edizioni Agi
XXIV Convegno nazionale di geotecnica (Napoli) 22-24 giugno 2011
Vol.2 pp.8 (pp.687-694) ISBN:9788897517009
Comina, Cesare; Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Musso, Guido
EPJ WEB OF CONFERENCES
pp.6 ISSN:2100-014X DOI:10.1051/epjconf/20100622012
Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Musso, Guido
In: Proc. 5th International Conference on Unsaturated Soils
5th International Conference on Unsaturated Soils (Barcelona (Spain)) September 6-8
Vol.CD-Rom
Comina, C; Cosentini, RENATO MARIA; DELLA VECCHIA, G; Foti, Sebastiano; Musso, Guido
In: Proc. 14th International Conference on Experimental Mechanics (ICEM 14)
14th International Conference on Experimental Mechanics (ICEM 14) (Poitiers, France) July 4-9
Vol.CD-Rom
Comina, C; Cosentini, RENATO MARIA; Foti, Sebastiano; Musso, Guido
RIVISTA ITALIANA DI GEOTECNICA
Vol.44 (pp.15-26) ISSN:0557-1405
Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Musso, Guido
In: Titolo volume non avvalorato
Incontro Annuale dei Ricercatori di Geotecnica (Roma) 9-11 Settembre 2009
Comina, Cesare; Cosentini, RENATO MARIA; Foti, Sebastiano; Musso, Guido
In: Titolo volume non avvalorato
28° Convegno nazionale GNGTS (Trieste) 16-19 novembre 2009
(pp.561-564)
Comina, Cesare; Cosentini, RENATO MARIA; DELLA VECCHIA, Gabriele; Foti, Sebastiano; Musso, Guido
PURE MATHEMATICS AND APPLICATIONS
Vol.20 pp.3 (pp.165-167) ISSN:1218-4586
Comina, Cesare; Foti, Sebastiano; Musso, Guido; Romero, E.
GEOTECHNICAL TESTING JOURNAL
Vol.31 (5) ISSN:0149-6115 DOI:10.1520/GTJ101367
Comina, Cesare; Festa, C; Foti, Sebastiano; Musso, Guido
THE LEADING EDGE
Vol.31 (pp.468-471) ISSN:1070-485X
A., Borsic; Comina, Cesare; Foti, Sebastiano; Lancellotta, Renato; Musso, Guido
GEOTECHNIQUE
ICE
Vol.55 pp.9 (pp.539-547) ISSN:0016-8505 DOI:10.1680/geot.2005.55.7.539
Comina, Cesare; Foti, Sebastiano; Lancellotta, Renato; Musso, Guido
In: Titolo volume non avvalorato
Proceedings of the 11th International Conference of the International Association of Computer methods and Advances in Geomechanics IACMAG2005 (Torino)
Vol.2 (pp.27-34)
Total: 16