Shrinkage and desaturation properties during desiccation of reconstituted cohesive soil

摘要

A vacuum evaporation method, proposed by the authors to reduce the water content more quickly than by air drying, was applied to six saturated reconstituted cohesive soil samples to investigate shrinkage and desaturation properties during desiccation. The test conditions were a vacuum pressure of p_v= -93.9 to -97.5 kPa, a consolidation pressure of σt,=68.6-392 kPa, an initial water content of wo = 0.59-0.92 w_L, and an initial surface area of the specimen of A_(s0) = 20-205 cm2, where w_L is the liquid limit. The results obtained for these restricted conditions are as follows. The vacuum evaporation of pore water from the soil occurs at a vacuum pressure higher than about -93 kPa (p_v > 93 kPa), but the evaporation process is very slow. The minimum void ratio, e_(min), at the no-shrinkage phase of the soil subjected to the vacuum pressure, becomes a constant value. The relations e_(min) ≈ 1.15 e_s and w_s ≈87(e(min)/G_s) are obtained, where es is the void ratio corresponding to the shrinkage limit, w_s, and G_s is the specific gravity of the soil particles. Using the vacuum evaporation method, the continuous relations for w — e, w— V/V_o, and w — S_r are more easily and more rapidly obtainable than with the conventional method by air drying. These three relations were formulated using two parameters, namely, an experimental parameter that is simply obtained using vacuum evaporation tests and a parameter that can be assumed and determined easily. The three formulated relations show a good agreement with the experimentally obtained results. Furthermore, if the basic physical parameter, w-s, has already been obtained, then the three relations can be estimated roughly without the performance of any tests.