AUTOMATIC VOLUME MEASURING DEVICE FOR TESTING DRY SOILS - MARTINA

A new automatic measuring device for testing dry granular soils in lab oratory is presented. The device enables direct measure of volume chan ges of dry specimens by measuring gas that comes out or in during test ing due to soil deformability. As the soil deforms, voids (which are s upposed to be hydraulically connected to each other) change their volu me; if they are part of a closed hydraulic circuit (any leakage is avo ided) and gas pressure is kept constant by adjusting the total volume of such circuit, the amount of gas through soil voids is transferred t o the measuring device, which varies its volume. The apparatus is desc ribed in detail as to its working principle. A strong effort was made to assess errors and to calibrate such apparatus as well as to evaluat e its precision when used for triaxial testing. Finally, to validate i ts behavior, the most significant results obtained comparing dry versu s saturated granular soil triaxial tests are here presented.