An Experimental study of the Effect of Loads on Frost Heaving and Soil Moisture Migration
1971 Volume 33 Issue 3 Pages 109-119
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1971 Volume 33 Issue 3 Pages 109-119
The application of the artificial freezing of soil to civil engineering has been developed and well utilized in Japan since 1962. The application, however, involves some difficult problems in spite of its benefits. Part of them has been solved on the practical as well as theoretical base mainly by the present authors. One of the most significant problems which remain unsolved, is the frost heave problem. The present paper discusses the problem under various conditions of load pressure in the open system.
Undisturbed soil sample, 10 cm in both diameter and height was enclosed in an acrylic acid resin cylinder of the apparatus (Fig. 1). The lower part of the cylinder contains an end cup filled with water. The surface of the water in the end cup was made to contact the bottom of the soil sample through the porous plate. The soil sample was sufficiently precooled at 0°C, and then cooled from the upper side at -2.5°C. The water in the end cup was kept at 0 °C during the freezing.
The following results were obtained :
1. The soil system discharges water during freezing when the load pressure exceeds a certain value (Fig. 3, 4).
2. The amount of frost heave decreases in accordance with the increase of load pressure (Fig. 7). The relation between the heave ratio (h), which means the ratio of the maximum heave amount to the initial height of sample, and the load pressure (p) is approximated as follows; h= h0+ c/p, where h0 and c are constants.
It is understood from this equation that complete elimination of heave action will be difficult, because it is assumed that h0 is due to freeze-expansion of adsorbed water around soil particles behind the freezing front.
3. The relation between the amount of heave (Vh) and the amount of migrated water (Vw) is expressed by the following equation;
Vh= (1-α) ΓVwo± (1 +Γ) Vw
where, Γ is the coefficient of volume expansion of water changing into ice, Vwo is the volume of water in soil before freezing and a is a constant (0<α<1). Therefore, when soil moisture is discharged from the soil system (Vw< 0), the frost heave decreases in amount. The value of α was calculated as 0.3-0.4 in the present experiment (Figs. 9-12).
