Studying the effect of drying on soil hydro-mechanical properties using micro-penetration method

Abstract

Understanding the hydro-mechanical response of soil during drying is significant for predicting and preventing the possible disasters related to drought climate. In this investigation, a novel micro-penetrometer was developed to characterize and quantify the drought-induced soil hydro-mechanical response based on the penetration curves, which present the variation of soil strength along depth. The relationships between the penetration resistance and soil water content, and the penetration resistance and soil suction were initially calibrated. It is found that the penetration resistance increases exponentially with decreasing water content as the soil is subjected to drying, while increases linearly with increasing suction. Before the air-entry value is reached, the drying-induced increment of soil strength is insignificant even a large amount of water is evaporated. During this stage, soil strength and water content along depth are generally uniform, and the increment of soil strength is consistent at any depth. After the air-entry value is reached, soil strength increases rapidly even water content decreases slightly. The distribution of soil strength along depth becomes non-uniform. It generally decreases exponentially with increasing depth due to the drying-induced water content and suction gradient. The predicted water content profile based on the penetration results was compared with the measured one, and good agreement was observed. It indicates that the proposed micro-penetration test can be used to characterize the hydro-mechanical response of soil during drying.