Abstract: In order to have a more comprehensive study about the mechanic and permeability of the soil-cement under the influence of the additives, there was a series of tests based on the orthogonal design method with a overall consideration of the influence of moisture content, cement content, water reducing agent content, fly ash content and other factors.Then according to the test, the unconfined compressive strength and permeability coefficient were obtained at the age of 3 d, 7 d and 28 d respectively, and the influence law of various factors on test were mastered and the relationship between them was simulated by SPSS software.The test results show that the order about the three factors against the unconfined compressive strength and permeability coefficient are moisture content, cement content, water reducing agent content,fly ash content.With the increase of moisture content, the cement-soil compressive strength decreases gradually and the permeability coefficient constantly increasing while the impact trend of cement content on the contrary.With the increase of water reducing agent of the sample, the strength curves were under the opening parabolas while the permeability coefficient curves were "V" shape change.In the practical engineering need according to the corresponding engineering goal and combined with field test to determine the best mix.In the cement-soil mixed a moderate amount of fly ash had no obvious effect on the strength.But it can reduce the permeability of the soil-cement especially in short ages.

Key words: soil-cement;additive;orthogonal test;unconfined compressive strength;permeability coefficient