Heaving of Spread Footing Due to Expansive Soil in Mae Moh District, Lampang

Abstract

This article presents the issue of foundation uplift in a four-story residential building in Mae Moh District, Lampang Province. The building exhibits diagonal cracks on walls near windows on all floors, separations at beam-column joints, and tilting of ground-floor columns. Surrounding the building, water sources are found within a 20-meter radius, and a permanently waterlogged area exists on the western side, indicating high soil moisture conditions. A soill investigation revealed that the subsoil beneath the foundation has a high swelling potential. Laboratory tests indicated a maximum swelling pressure of approximately 150 kN/m² and a free swell ratio of about 4.0%. Analysis using the O’Neill and Poormoayed method predicted a foundation heave of approximately 55–65 mm, which
is significant enough to cause structural damage. The study found that using a shallow spread footing on expansive
soil presents challenges, as designing a foundation with sufficient weight to counteract swelling pressure is difficult. This issue is particularly pronounced at greater depths, where stress from the building load diminishes. Suitable mitigation measures may include deep foundation systems to bypass the swelling zone or soil improvement techniques before construction to reduce the soil's swelling potential.