Analysing the Chemo-mechanical coupling in BVP: experimental set-up Cedex Madrid - Politecnico di Milano Analysing the Chemo-mechanical coupling in BVP: experimental set-up

Weathering of a cemented silica sand: an artificial soft rock 1) SILICA SAND Part 1: Experimental study After immersion in acid solution: Progressive dissolution of calcareous intergranular bondsProgressive dissolution of calcareous intergranular bonds CaCO H 3 O + Ca H 2 O + CO 2 (gas) Calcite Acid Calcium Water Carbon Dioxide 2)LIME 3) WATER COMPONENTSCOMPONENTS ARTIFICIAL SOFT ROCKARTIFICIAL SOFT ROCK INTACT (cemented sand) COMPLETELY WEATHERED (unbonded sand)

Experimental measures on carbonate dissolution reaction CaCO H 3 O + Ca H 2 O + CO 2 (gas) Calcite Acid Calcium Water Carbon Dioxide We will use artificial cemented sand: the initial amount of CaCO 3 is known if we assume a complete lime hydration. Anyway we can measure it in the chemical lab. It means to measure the pH value. We will use electronic pH_meter to get precise and continuous measures We will use a electronic ion chromatograph to get precise and continuous measures We also know the total amount of ion H + to dissolve all the initial amount of CaCO3. Ning et al (2003) The kinetic of this reaction has been widely studied by chemical researchers

COLUMN TEST: monodimensional chemo-mechanical tests with acid transport Using the WTD, but with an HIGHER specimen

COLUMN TEST: monodimensional chemo-mechanical tests with acid transport Using the WTD, but with a HIGHER specimen and measuring pH and Ca 2+ at different levels h h A A c c i i d d f f l l o o w w a = const. ACID FLOW Axial stress Axial strain Radial stress pH Output [Ca 2+ ] output water flow pH and [Ca 2+ ] measures at different levels pH Input Mechanical: -Axial stress -Radial stress -Axial strain -Radial strain Fluid : -Fluid Velocity -Pore pressure Chemical: -Source input boundary -Chemical species H + Ca 2+ Dimension : diam. 50mm, heigh 100mm

Experimental BVP-Weathering induced subsidence of a shallow foundation Automatic load system with both load and displacement control Available Experimental apparatus Box test (plane strain) (890 x 440 x 200 mm) Photogrammetric acquisition of subsoil displacement field

Experimental BVP-Weathering induced subsidence of a shallow foundation Automatic load system with both load and displacement control Available Experimental apparatus Box test (plane strain) (890 x 440 x 200 mm) Photogrammetric acquisition of subsoil displacement field Ready for test

Apparatus scheme

Photogrammetric acquisition of subsoil displacement field

Digital calibrated photocamera Reference markers Image analisis Photogrammetric acquisition of subsoil displacement field

CORRELAZIONE A MINIMI QUADRATI si ricerca la massima somiglianza tra i toni di grigio dei pixel della FINESTRA di RIFERIMENTO, f(i,j) la convergenza al minimo è ottenuta iterativamente partendo da unapprossimazione della posizione iniziale pari a 5 pixel MODELLO GEOMETRICO : trasformazione affine MODELLO RADIOMETRICO : correzione preliminare col FILTRO DI WALLIS correzione preliminare col FILTRO DI WALLIS e quelli della FINESTRA MOBILE, g(i,j) : variando, attraverso un ricampionamento, FORMA, POSIZIONE, TONI DI GRIGIO della finestra mobile. posizione iniziale posizione finale

SITUAZIONE INIZIALE SITUAZIONE FINALE FASE OPERATIVA sulla prima immagine si selezionano, etichettano, misurano i punti dinteresse su immagini seguenti si predicono le coordinate approssimate considerando gli spostamenti precedentemente valutati prova n°2: 99/102 sferette su 40 immagini prova n°1: 175/190 sferette su 77 immagini

Test 2 results Gid postprocessor EVOLUZIONE DEGLI SPOSTAMENTI DALLISTANTE INIZIALE MESH DORIGINE

Sfera 11 Sfera 28 Sfera 62 Sfera 79 Sfera 45 Comparison with settlement-load curve

Experimental BVP#1-Weathering induced subsidence of a shallow foundation

Experimental BVP#2-Pumping oil -injecting water A B Silica sand : n= Water conductivity k=1*10 -3 m/s Imposing water pressure in injection camera A and im the pumping camera B: Rwsolution of 1 kPa, range from kPa