Experimental study of a pseudo-preconsolidation pressure in frozen soils

Preconsolidation pressure (pc) is an important parameter in soil mechanics. For conventional unfrozen soils, pc is an index of the loading history and has a close relationship with the mechanical properties of soils. For frozen soils, special structures exist due to the interaction between ice and soil grains. A similar index like pc may exist in frozen soils, which is of great importance in the study of their mechanical properties. In this paper, clay obtained from the Qinghai–Tibet Railway is taken as the study object. K0 compression tests were carried out on remolded soil samples with a wide range of dry unit weights under different negative temperatures. Double logarithmic coordinates were used to obtain the preconsolidation pressure index of the frozen soil. The test results show that an index does exist in the frozen soil, which is called pseudo-preconsolidation pressure (PPC) to take into account its different nature to pc in conventional soil mechanics. The test results also show that PPC is dependent on the initial dry unit weight of the frozen soil, but temperature is a more dominant factor. In order to investigate the influence of creep on frozen soils and use creep models for unfrozen soft soils, creep tests were carried out at different creep times at different temperatures. PPC was found to change in different ways with different pre-loads during creep. Further more extensive studies on the creep effects of pre-load on PPC would help to establish creep models for frozen soils.