INVESTIGATION FOR WATER AND SALT MIGRATIONS ON SPALLING DISEASE OF LOESS SLOPE CAUSED BY SALIFICATION EROSION

The paper studies characteristic of spalling disease of loess slope caused by salification erosion through field investigation and indoor water content and soluble salt tests. The results show that the salification erosion spalling disease can be divided into strip-shape, sheet-shape and cavity-shape spalling on the basis of spalling shape. Furthermore, the salification erosion spalling disease can further be divided into Q₃ loess, Q₂ loess, paleosol layer and artificial compacted loess spalling according to the geological conditions. The water content of loess sample increases with the increment of vertical depth from slope surface. With the increase of vertical depth from slope surface, the total salt content decreases greatly and reaches a stable value soon. The CO₃^2- and HCO₃^- ion contents have no obvious change rule with increasing vertical depth. With the increase of vertical depth, the Cl^- and SO₄^2- ion contents decrease greatly and reaches a stable value soon. The K⁺, Mg²⁺ and Ca²⁺ ion contents have no obvious change rule with increasing vertical depth. With the increase of vertical depth, the Na⁺ion content decreases greatly and reaches a stable value eventually. The SO₄^2- and Cl^- ion contents are higher in the anions with the Na⁺ ion content highest in the cations. Therefore, Na₂SO₄ and NaCl are the main components of soluble salt in soil on the surface of loess slope. Furthermore, Na₂SO₄ and NaCl repeatedly dissolve and crystallize under condition of climate change, which causes the spalling disease of loess slope.