U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, N.H., U.S.A.

Settlement of clay soils after freezing and thawing is the result of the suction forces that draw pore water to the freezing front. These suction forces cause an increase in the effective stress on the clay beneath the freezing front, and thus cause an overconsolidation of the clay. As these suction forces often exceed 1 atm, their direct measurement is not easy.

A technique for indirectly determining the maximum suction occurring during freezing is presented which utilizes the apparent memory that clay soils have for maximum past (preconsolidation) pressures. Suctions as large as 532 kN m^?2 were observed after freezing and thawing a clay soil which was initially consolidated to 128 kN m^?2.

The volume changes resulting from the freezing and thawing of clays were related to the plastic limit and were observed in the laboratory to be as high as 25%. If provisions are not made to account for these volume changes in a ground freezing project, considerable damage to structures can occur from settlement and the resulting stresses.