Shengyang Yuan

Calibration of a Coupled Model to Predict the Magnitude of Suction Generated by Osmotic Technique With PES Membranes and Temperature Effect

Using the osmotic technique to control soil suction requires a reliable correlation between concentration of soluble polyethylene glycol (PEG) and suction generated under isothermal condition. Experimental data to establish such correlation can be found in the literature but they tend to be incomplete and mainly pertain to cellulose membranes. Recent research has shown that polyethersulfon membranes (PES) are a better alternative than cellulose membranes in terms of durability and reliability. However, no complete calibration dataset is available for applying the osmotic technique to account for use of PES membranes and effects of different PEG molecular weights, concentrations and temperature. This study intends to fill such a gap by providing reliable and comprehensive experimental data. The response of PES membranes was investigated over a range of temperature varying from 20°C to 40°C and the results were used to calibrate a coupled model that allows a better prediction of suction generated by the osmotic technique. The influence of PEG molecular weight has been evidenced and can be incorporated in the model.

Development and Validation of a New Near-Infrared Sensor to Measure Polyethylene Glycol (PEG) Concentration in Water

A near-infrared absorption based laser sensor has been designed and validated for the real-time measurement of polyethylene glycol (PEG) concentration. The wavelength was selected after the determination of the absorption spectrum of deionised water and PEG solutions using a Varian Cary 6000i spectrophotometer, in order to limit the influence of PEG molecular mass on the absorption measurement. With this new sensor, the water is treated as the attenuating species and the addition of PEG in water reduces the absorbance of the medium. The concept was validated using three different PEG types (PEG 6000, 20,000, and 35,000) and it was found that the results follow Beer Lambert’s law. The influence of temperature was assessed by testing the PEG 20,000 at four different temperatures that could be encountered in a laboratory environment. The data show a slight temperature influence (increase of absorbance by 8% when the temperature rises from about 20° to about 29°). Following the validation phase conducted ex situ, a prototype of an immersible sensor was built and calibrated for in situ measurements.