INFILTRATION CHARACTERISTICS OF TOPSOIL AT HEIFANGTAI IN GANSU PROVINCE

Heifangtai is one of the typical loess platforms in Gansu province. The platform surface has been largely irrigated over the past forty years. The underground water level upraised and many landslides occurred. The frequent loess landslides have seriously threatened the local development. This paper carries out the double rings infiltration tests, varying-head infiltration test for the disturbed samples and varying-head infiltration test for the remolded samples. It analyzes the characteristics among the three tests. It uses the geophysical prospecting to verify the test results. The following conclusions are made:(1)The permeability coefficient of unsaturated loess tested by the three kinds of tests are linearly decreases with the increase of dry density; (2)Under the same conditions the permeability coefficient tested by the double rings infiltration tests is the largest. The remolded samples' permeability coefficient is the minimum. The differences among the results from the three types of permeability coefficient tests decrease with the increase of dry density; (3)The permeability coefficient tested by the double rings infiltration tests is most close to the in situ loess permeability according to the high-density electrical method.