The behaviour of piles in unsaturated expansive clays under cyclic lateral loading
The behaviour of piles in unsaturated expansive clays under cyclic lateral loading
This article presents the results of full-scale testing of laterally loaded piles installed in an unsaturated expansive clay profile. For the pile tested under natural water content conditions, a distinctive accumulation of progressive displacement (or ratcheting) was observed in the direction of applied loading. This behaviour was attributed to the local yielding of the bonded/cemented material along soil fissures. In contrast, the ‘wet’ pile, tested after the clay profile was allowed to swell for a period of 6 months exhibited no ratcheting. Given that fissures would likely have swelled closed prior to testing of the ‘wet’ pile, local yielding of the bonded material along fissures due to applied loading would not have occurred, thereby limiting any ratcheting behaviour. Moreover, as the number of loading cycles increased, the ‘dry’ pile displayed an increased cycle stiffness. Given the local yielding that would have occurred during initial load cycles, it is postulated that this behaviour be ascribed to subsequent load cycles pushing intact masses of clay against one another at the fissure interfaces. Conversely, the ‘wet’ pile demonstrated slight reductions in cycle stiffness. Assuming constant water content conditions within the clay profile, this result is due to local reductions in void ratio behind the loaded pile, causing increases in saturation, thereby reducing soil suction and stiffness with increasing load cycles.
T. A. V. Gaspar; Ruan Andrew Murison; S. W. Jacobsz; Gerhard Heymann; A. S. Osman
18th European Conference on Soil Mechanics and Geotechnical Engineering (ECSMGE2024)
A - New developments on structural design
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