Experimental Study and Prediction of Water Retention Curves of an Unsaturated Kaolin

In this research, soil water retention curves (SWRCs) of compacted kaolin at different dry unit weights were measured using experimental techniques of filter paper and pressure plate. The results show that the water retention behavior of kaolin is independent of the type of measurement method, and the initial dry unit weight of the sample is the most significant factor governing the SWRCs. In other words, the preparation of the samples with different water contents in the filter paper method and the possible resulting changes in the soil fabric do not substantially affect the water retention behavior of kaolin. An existing model was adopted for predicting the behavior of these curves under different dry unit weights. Investigation of the results indicates that the performance of this model is suitable for predicting the SWRCs of samples with nearly identical initial dry unit weights. In contrast, it is inappropriate for samples with wide ranges of dry unit weights. Finally, an alternative method was presented in selecting the model parameters to modify the model predictions of SWRCs. Furthermore, since the behavior of SWRCs is similar to the curves of the low-pass Butterworth filter, this function was used to simulate the SWRCs and gave good agreement with the experimental results.