Abstract
A success of any experimental research program relies on selecting the suitable experimental technique and appropriate testing equipment. These testing equipments should be calibrated for all factors affecting test results. Reliable calibration of any experimental device is considered the main step for a successful experimental program. Evaluation of the volume change behavior of expansive soils using osmotic technique have gained widespread acceptance as reliable method for controlling suction in soil specimens. In this research, suction controlled testing was performed using modified oedometer and triaxial equipment by circulating Polyethylene Glycol solution (PEG) over a semi-permeable membrane which overly the tested specimens. The modified oedometer comprised of thin-wall oedometer ring instrumented with strain gauges to measure the lateral stresses evolving during the test. The first part of this paper introduces the errors that arise during osmotic suction testing, concerning the device flexibility and PEG solution losses. The second part of the paper highlights the calibration procedure for estimating lateral stresses in modified oedometer from instrumented strain gauge as well as introduces a correction for the temperature fluctuation. Finally, the effect of triaxial cell flexibility on the volume change measured during osmotic suction controlled testing as well as temperature effect on volume change measurements was evaluated and correction procedures were introduced.