Automatic Back-Pressure Saturation Device for Triaxial Testing
If back pressures are applied to unsaturated triaxial specimens too rapidly, the specimens may be overconsolidated by the temporary application of effective stresses that are higher than intended. This is dangerous because the strengths of the specimens will be higher than they would be without this inadvertent overconsolidation. An automated device has been developed to ensure that the specimen will not be overconsolidated during saturation. This device continuously monitors the maximum effective stress in the specimen and optimizes the rate at which the cell pressure and back pressure can be increased without exceeding an allowable effective stress at any point in the specimen. Tests were performed on three soils with different grain sizes and degrees of saturation to investigate the effectiveness of the device under varying test conditions. The tests show that the device is capable of applying back pressures with a minimum of operator attention, and that it eliminates the possibility of inadvertently overconsolidating specimens during back-pressure application.