On the base of the uplift model tests and prototype tests on foundation of transmission line tower

the uplift performance of expansive soil is deeply researched.The regularity of soil displacement

stress distribution

load capacity

failure mechanism were analyzed.The defect of existing uplift theory and calculation in clay is pointed out;this is that the failure of the soil is not only existing in cracking surface

but also existing entire soil body.Thus the composing of uplift bearing capacity is put forward that it is consisted of base weight

earth mass weight above the base

shear strength in the failure soil

and foundation bearing capacity caused by stress re-distribution owing to soil compressed;and then the FEM software is used for the analysis and validation.Finally

scale effect in the model tests is discussed.