Deformation test equipment FLAT JACK

manualfor wallfor the construction industry

FLAT JACK TESTING EQUIPMENT WHAT DOES IT DO Estimation of in-situ compressive stress within solid unit masonry (single-jack testing) and In situ measurement of masonry deformability properties (double-jack testing). Monitoring of stress changes in elements such as concrete lining of pre-existing tunnels. ADVANTAGES • Compact and easy to carry; • Simple to install and use; • Reliable and accurate; • Compliant with RILEM recommendations. DESCRIPTION Device for applying the load, consisting of welded metal pockets, pressurized by means of a measuring fluid. Equipped with a fluid inlet and outlet system. APPLICATION SINGLE-JACK TESTING: The determination of the state of stress is based on the stress release caused by a plane cut perpendicular to the wall surface. The stress release is determined by a partial closing of the slot (this means that the distance between the gauge points previously fixed to the wall across the slot will be shorter than before the cutting). A thin flat-jack is placed inside the cut and the pressure is gradually increased to obtain the distance measured before the cut. The pressure of the hydraulic system driving the displacement equal to those read before the slot, will give the stress condition in that area, after taking in due consideration some correction factors. The displacement caused by the slot and the ones subsequently induced by the loaded flat jack are measured by a removable strain gauge before and after the slot and during the tests.