Research On Uplift Behavior Of Golmud-Lhasa Transmission Line Tower Foundation In Permafrost

In China, more and more transmission line project across the permafrost region,but at present there is no design specification of tower foundation in permafrost. In thiscontext, the Northwest Electric Power Design Institute Chinese Power EngineeringConsulting Group launched the work to set 《Technical specification for design offoundation for overhead transmission line in frozen soil region》. This paper as a subproject, relying on Golmud to Lhasa transmission line project, will reserach the upliftbehavior of expansion slab tower foundation in permafrost.This paper conducts pull-out tests of the tower foundation models. The foundationmodels are scale down from the excavation expansion slab tower foundation includingstraight column foundation and cone column foundation. Pull-out tests of foundationmodels is conducted in silty clay of different water content, different freezingtemperatures to get the shape parameters of the failure surface and its change law alongwith the different experimental conditions, as well as the uplift load displacement curveof foundation model. From analysis, the pull out failure mode of foundation inpermafrost is overcome freezing strenghth between foundation and soil-compression offrozen soil above expansion slab-the emergence and development of plastic zone infrozen soil-general shear failure of frozen soil.According to the Golmud-Lhasa transmission line engineering,establishaxisymmetric model of straight column foundation and cone column foundation withdifferent depth and different extension plate diameter in permafrost with just freeze andcompletely melt active layer. The simulation process from the beginning of uplift togeneral shear failure of permafrost to get the uplift angel of failure surface, find out thatits value is close to the value of model test. Research the influence of foundation depth,expansion slab diameter, foundation type to uplift bearing behavior of tower foundation.On the basis of the foundation size and foundation load in Golmud-Lhasatransmission line engineering, establish3D numerical model of straight-line towerfoundation and corner tower foundation. Calculate the displacement of tower foundationsubject to pullout load and horizontal load, compare to the displacement of towerfoundation only subject to uplift load. Make the conclusion that the horizontal loadinfluence coefficient might be0.95.