Abstract: To study the effect of soil structure on deformation characteristics, a series of odometer and mercury intrusion porosimetry tests on undisturbed, remolded, reconstituted and compacted samples of Shanghai soft clay, was carried out to obtain the compression curves and the pore-size distributions (PSD) of samples. The test results show that consolidation pressures and sample preparations have important influence on the PSD curves, and the PSD of undisturbed sample of Shanghai soft clay exhibits a unimodal shape, with a pore-size mainly ranging from 0.01 to 1.0 ?m. The unimodal PSD of undisturbed sample is greatly influenced by soil structure. Large and medium interparticle pores are compressed into the small interparticle pores with increasing consolidation pressures, particularly under the consolidation pressure larger than the structural yield stress. The unimodal PSD also was found in saturated soft clay, no matter undisturbed, remolded, reconstituted or compacted samples. However, the PSD curves of samples using different sample preparation methods are different. The compacted samples have larger pore size and the reconstituted samples generate uniform pore size. The differences of micro-pore structure among different samples will be reduced with increasing consolidation pressure, yet never eliminated even at large consolidation pressure. Lastly, the reference void ratio, i.e., a simple expression of clay fabric, is used to normalized the compression curves of the samples with different preparation. Different compression curves of four types’ samples are normalized to a high correlative unified compression curve, which shows that the reference void ratio is a reasonable and effective parameter to illustrate the PSD of clay.

Key words: Shanghai soft clay, mercury intrusion porosimetry, pore-size distribution, soil structure, reference void ratio