The ϕu = 0 method and UU tests
This chapter presents a simplified method of dealing with clays through total stresses, known as the ϕu = 0 method, in which UU undrained tests are used. The unconfined compression, or U test, is a special type of triaxial test that involves axial compression of a cylindrical specimen under zero confining stress. Theoretically it should give the same results as the UU triaxial test. In situ testing is a way of avoiding disturbance effects during sampling. In particular, for the determination of the undrained strength of soft and medium clays, the field vane test has been used with success. Early attempts to determine the undrained shear strength by means of this test occurred in Scandinavia in 1919, but this technique only started to be used in Europe and North America in the late forties.