COMPARATIVE EXPERIMENTAL STUDY ON PERMEABILITY OF UNDISTURBED AND REMOLDED LOESS UNDER FREEZING-THAWING CONDITION

The influence of freeze-thaw action on the permeability of undisturbed and remolded Q₃ loess in Xi'an city is comparatively studied by the SEM and triaxial consolidation permeability tests. The experimental data indicates that the microstructure of undisturbed and remolded loess all changes significantly under freezing-thawing condition. The soil cementation structure is weakened, and then the particle alignment becomes more loose. Finally, the void ratio of soil increases and makes the permeability enhanced. Freezing-thawing makes the surface structure of undisturbed and remolded loess destroyed greatly, and has a bigger influence on the undisturbed loess. The cracks produced by freezing-thawing process become the main channel for water flow and migration, resulting in the obvious increase of permeability for undisturbed and remolded loess. With the increment of water content, the permeability coefficients for undisturbed and remolded loess all firstly increase and then decrease under freeze-thaw cycle condition, complying with the parabola law. With the increase of freezing-thawing times, the permeability coefficients all firstly increase and finally approach to a steady state, following the exponential rule. With the increment of cell pressure, the permeability coefficients all firstly decrease and finally reach a steady state, also following the exponential rule. The permeability of undisturbed loess is always greater than that of remolded loess under the same condition. Moreover, the permeability coefficient difference between undisturbed and remolded loess is smaller with the increase of cell pressure.