Study on the Stability of Spread-Footing Foundations on Permafrost Regions

Spread-footing foundations embedded in frozen soil are subject to both the wind-induced uplift and frost heave forces. The stress and deformation of foundations in the Qinghai-Tibet Power Transmission Line (QTPTL) engineering were monitored to investigate the stress state of the tower foundations. The results showed that the stresses at the bases of tower foundations had a close relationship with air and ground temperatures. Seasonal variations in the contact stress depended on the seasonal freezing and thawing of foundation soil. The contact stress increased with the cooling of the underlying soils and decreased with the warming of the underlying soils. The numerical simulation results showed that the frost heave force induced by soil freezing potentially threatens the safety and normal operation of the QTPTL. Thaw settlement may lead to harmful deformation of tower foundations if global warming is considered in the numerical model. The remedial measure with thermosyphons only can reduce the settlement of the foundation and will increase the frost jacking risk of the foundation.