Physical Modelling of Lime Stabilisation in Soft Soils Around Deep Excavations-Article

Article

Pdf Summary

The study investigates whether a shallow layer of lime-stabilised clay can reduce heave and ground settlement around deep excavations in soft soil. This could offer a more economical alternative to treating the full soil depth or extending treatment to the retaining-wall toe.<br /><br />Researchers conducted two centrifuge tests at 160 g, modelling a 12 m-deep excavation supported by an 8.8 m-embedded, very stiff retaining wall. The wall was designed to minimise movement from bending, allowing observed ground displacements to be attributed mainly to basal heave. The reference test used untreated clay; the second included a 5% lime-treated layer, half the excavation depth in thickness, across the formation level.<br /><br />The lime-treated layer substantially improved excavation performance. At an overburden pressure of 50 kPa, surface displacements near the excavation were 65% lower than in the untreated test. At 39 kPa, measured movements were about one-third those of the reference test. The treatment also delayed failure and increased excavation stability by a factor of three. Pore-pressure measurements and image analysis supported the observed reduction in movement.<br /><br />The lime-treated soil had been cured for two days. Separate strength tests showed that its strength continued to develop with curing, particularly over the first week, but the analysis suggested little additional stability benefit from delaying excavation beyond seven days. The findings indicate that a relatively shallow treated layer can control movements in soft-clay excavations. However, only two centrifuge tests were performed, and the most effective treatment width and area remain to be established.

Keywords

lime-stabilised clay

deep excavation

soft soil

basal heave

ground settlement

centrifuge test

retaining wall

pore pressure

soil stabilization

excavation stability