Abstract: Undisturbed loess is a type of under-consolidated soils with structural strength, and its confined compressive deformation characteristic is distinct from those of ordinary soils. To study the general character of confined compression deformation of undisturbed loess, confined compression tests were carried out on Q3 and Q2 undisturbed loess with different water contents sampled from six fields in Xi'an and Lanzhou. The compression curves of undisturbed loess at different water contents from corresponding sites were obtained. The shape of the compression curve was analyzed. Through the compressive yield stress and the initial void ratio corresponding to the curve, the compression curves of tested loess at different water contents were normalized into a same curve, and the positions of the normalized curves of loess with the same sedimentary period were the same. The normalized curves of Q3 and Q2 loess were respectively described by composite power-exponent model. The initial void ratio and compressive yield stress of the loess in the literature were substituted into the expression of normalized curve to calculate the compression curves and compressibility indexes. It was found that the curves tested in literature was close to the compression compressibility indexes, demonstrating the normalized characteristic of loess compression curve and its application value. The test loess compression curve has the characteristics that can be normalized by its initial void ratio and compressive yield stress, which provides a convenient way for the analysis of confined deformation properties of loess.

Key words: soil mechanics, undisturbed loess, compressive curve, compressive yield stress, initial void ratio, normalization