Abstract: Immersion of loess can form compacted saturated loess or uncompacted saturated loess, and their engineering properties are significantly different. Based on the tests and data statistics of 22 loess sites in the Xi’an area, this paper systematically studied the basic physical and mechanical properties of the uncompacted saturated loess for the first time, revealed the fundamental reasons for its water-saturated weak property and large deformation due to water loss, and summarized the physical and mechanical characteristics of the uncompacted saturated loess in Xi’an area. The above research results can provide a basis for scientific research and engineering practice to strictly distinguish two types of saturated loess and formulate technical measures by classification. It is concluded that: uncompacted saturated loess is a kind of soil in which collapsible loess is not fully compacted, and macropore structure still exists in the immersion process. It is exposed in Q₃ loess or the upper part of Q₂ loess. It has a large void ratio, high water content, medium and high sensitivity, medium and high compressibility, low bearing capacity and strength, and is generally in soft plastic or flow plastic state. It is distributed adjacent to the compacted saturated loess, collapsible loess, and paleosol, forming a combination of soft and hard strata.

Key words: saturated loess, uncompacted state, physical state, mechanical properties