Abstract: In order to investigate the vertical deformation contributed by effective stress increment of soils overlying foundation base， the saturation test of unsaturated sandy soil and the static load test were conducted with different axial loads and cell pressures， and work of calculation and analysis based on Mohr-Coulomb’s method was finished. The main physical and mechanical indexes of gravelly sand and gravel， such as natural gravity， cohesion and angle of internal friction etc.， were obtained under condition of saturation. Effective stress increment and its vertical deformation were obtained by using the indexes. The results indicate that degree of saturation of gravel is more easily to reach 100% compared with gravelly sand， and saturated unit weight of gravel is larger， but porosity and water content of gravel are smaller than that of gravelly sand. As to saturated sandy soil， the principal stress computed by effective stress method is usually larger than that by total stress method， thus angle of internal friction and cohesion obtained by effective stress method are more reasonable. In addition， vertical deformation contributed by effective stress increment can not be ignored.

Key words: effective stress increment, additional stress, desaturation effect, excess pore pressure, settlement