Volume 20, Issue 4 (December 1997)
Automatic Volume Measuring Device for Testing Dry Soils: “Martina”
A new automatic measuring device for testing dry granular soils in laboratory is presented. The device enables direct measure of volume changes of dry specimens by measuring gas that comes out or in during testing due to soil deformability. As the soil deforms, voids (which are supposed to be hydraulically connected to each other) change their volume; if they are part of a closed hydraulic circuit (any leakage is avoided) and gas pressure is kept constant by adjusting the total volume of such circuit, the amount of gas through soil voids is transferred to the measuring device, which varies its volume. The apparatus is described in detail as to its working principle. A strong effort was made to assess errors and to calibrate such apparatus as well as to evaluate its precision when used for triaxial testing. Finally, to validate its behavior, the most significant results obtained comparing dry versus saturated granular soil triaxial tests are here presented.