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

Presentazione sul tema: "Analysing the Chemo-mechanical coupling in BVP: experimental set-up Cedex Madrid - Politecnico di Milano Analysing the Chemo-mechanical coupling in BVP:"— Transcript della presentazione:

1 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

2 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 3 + 2 H 3 O + Ca 2+ + 3H 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)

3 Experimental measures on carbonate dissolution reaction CaCO 3 + 2 H 3 O + Ca 2+ + 3H 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

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

5 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

6 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

7 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

8 Apparatus scheme

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11 Photogrammetric acquisition of subsoil displacement field

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

13 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

14 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

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

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

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

18 Experimental BVP#2-Pumping oil -injecting water A B Silica sand : n= 0.3-0.4 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 0-1000 kPa

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