Upper limit of heaving pressure derived by pore-water pressure measurements of partially frozen soil

Experiments were conducted to estimate heaving pressures of saturated soil partially frozen in a closed system. Temperatures at both ends of a specimen were kept constant, i.e., positive at the top and negative at the bottom. When the overburden pressure P was maintained at a constant value, the pore-water pressure P_w, which showed a certain value before freezing, decreased gradually as freezing progressed, finally attaining a specific value, whereafter the specimen ceased taking water into it. The pressure difference between P and P_w, at this stage was defined as the upper limit of heaving pressure σ_u, which evidently depended on the temperature θ_c of the cooling end, in accordance with the relation: σ_u = −11.4 θ_c (kg/cm²)

It corresponds to the modified Clausius-Clapeyron's formula, which gives the freezingpoint depression of an ice—water system, where the pressure acting on the ice differs from that on the water. This is the same as the value obtained by Radd and Oertle (1973). It is considered, however, that, when θ_c lowers, the value of θ_u reaches finally a constant value smaller than the one obtained by the above equation. Denoted by σ_{u max}, it was defined as a maximum heaving pressure. The value of σ_{u max} depended on soil type.