<p>Understanding active earth pressure in unsupported trenches is essential for evaluating their stability. Traditionally, the Rankine or Coulomb theories are employed to calculate active earth pressure using saturated shear strength parameters. However, when trenches are excavated in unsaturated soils, additional factors such as soil type, matric suction profile, and rainfall events must be considered. Especially, estimating the behavior of unsupported trenches reliably, particularly with respect to rainfall infiltration, is crucial to prevent sudden failures. This study aims to estimate the variation of active earth pressure during rainfall events and identify the optimal location of equilibrating force to maintain the stability of unsupported vertical trenches during construction operations. For this, extensive numerical analyses were carried out using SEEP/W and SLOPE/W (GeoStudio 2020) jointly for different levels of groundwater table and a rainfall intensity equivalent to the saturated hydraulic conductivity of the soil. Based on the findings, it turned out that applying the median value of resultant force at 20 or 40% of the critical depth of an unsupported vertical trench will ensure FOS greater than 1.2 during long periods of rainfall events. The findings in the research can be utilized in the field to mitigate the risks associated with the instability of unsupported vertical trenches in unsaturated soils.</p>