Expansive soil has clay minerals which expand upon adding water. Such expansion can be large enough to exert pressure on adjacent structures which can induce structural damage.
I am searching for a cheap sensor to be placed between soil and a model structure to measure the swelling pressure.
Greetings;
You can simply use load cells with zero strain and these can be connected to PC for logging the data. Becarefull to choose a suitable cell regarding the max pressure limit. For instant, highly compacted smectite rich clays exert very high swelling pressures 2-2.5 MPa. Below a manufacturer of load cells.
Good luck
http://www.dacell.com/en/en_loadcells/show/view/cno/10/page/2/id/744
well, I am more interested in measuring the distribution of pressure, unless a local measurment
I see, then maybe you can use a flexible load cells (below). But the installation will be a little bit tricky! These might fail under high pressures unless you find suitable ones with the high pressure capacity.
Another alternative, you can make a bigger cell (say 70 or 100 mm dia.) then you can install ordinary small load cells. Install them at different spots, let’s say at the circumference which requires a special arrangement, see the attachment. You can follow the same idea for top and bottom parts.
I hope this could help you.
http://www.tekscan.com/flexiforce/load-cell.html
Thanks but i am looking for a large scale measurement and looking for a sheet like sensor to delineate the distribution of pressure on spreaded area
A simple laboratory method for measuring the swelling pressure is using an odometer. After reaching your soil to the maximum expansion in an odometer, you should add surcharge on it until the gauge return to zero. That surcharge is your swelling pressure.
Laboratory method suggested by Mr. Moghadas is OK, but suitable only for less expansive soils. It is impossible to bring all the sample back into the oedometer ring by loading after the total volume change of extremely swelling bentonites.
Thank you Renata and Mehrdad for the contribution.
Can you please further elaborate the procedure. And any article or standard, explaining it will be appriciated.