Analytical Modeling of Unsaturated Soil Shear Strength during Water Infiltration for Different Initial Void Ratios

Unsaturated soil mechanics, when applied to determine the soil shear strength, are crucial for accurately evaluating the safety of geotechnical structures affected by seasonal moisture variations. Over the past decades, multiple models have been formulated to predict the behavior of unsaturated soils in terms of water flow and shear strength individually. Building upon these foundational studies, this research introduces a model that couples an analytical solution for one-dimensional water infiltration with an unsaturated shear strength model. This model further incorporates the impact of void ratio fluctuations on soil properties and state variables related to shear strength. A parametric analysis is conducted to evaluate the effects of the initial void ratio on a representative soil profile during a water infiltration event. The model presented in this paper integrates various concepts from the field of unsaturated soil mechanics and is applicable to any homogeneous soil where expansion/collapse effects are negligible. It demonstrates how shear strength might be underestimated when using a saturated soil approach. Conversely, it may also lead to an overestimation of safety conditions if the soil approaches a saturated or dry state. The proposed model offers a more accurate prediction of unsaturated soil shear strength. It is useful for determining transient safety factors in geotechnical structures. Furthermore, when combined with field-installed instrument monitoring, this model contributes significantly to the functionality, safety, cost-effectiveness, and sustainability of geotechnical structures and projects.