Experimental Evaluation of Lateral Swelling Pressure of Expansive Soil Fill behind a Retaining Wall

Lateral swelling pressure (LSP) of expansive soils included in the total lateral pressure (TLP) often results in instability and even sliding failure of retaining walls. In this study, a modified oedometer was developed and adopted to overcome certain limitations in previous laboratory swelling tests on expansive soils. A method for measuring LSP is proposed. TLPs of medium expansive soils samples were measured under different water contents, dry unit weights, and immersion vertical pressures. From experimental results, it was indicated that the ratio of LSP to vertical swelling pressure (VSP) at a constant volume of expansive soils with different initial water contents ranged from 0.27 to 0.31. A case study was carried out to investigate the stability of a 3-m-high gravity retaining wall backfilled with expansive soils. In active state, the larger resultant force of LSP is two times of that of active earth pressure on the retaining wall, resulting in sliding failure of retaining wall.