Abstract:

In order to obtain the distributed rule of the earth pressure for unsaturated loess Q3 at the original state and its rules of changes during the process of excavating or saturating, an in-site test was done on an 18 m high slope, which included displacement, earth pressure, suction and the process of collapse. Meanwhile, a series of indoor triaxial shear tests on unsaturated loess Q3 at the original state were also conducted. The outcome as follows: ①For the unsaturated loess Q3 at the original state, the relation between the apparent cohesion and suction is nonlinear, between the effective friction angle and suction is nonlinear too. ②The earth pressure of unsaturated loess Q3 at the original state increases with the excavating depth, which results in the shape of triangle at the end of excavation, high in the middle, low at the two ends; and the maximum earth pressure at the 1/3 height of the slope. Compared with the calculated result from Rankine’s theory, the tested earth pressure is relatively lower, whereas it increases rapidly on the condition of saturation. In short, saturation is the direct cause of the slope collapse.

Key words: unsaturated loess, earth pressure, saturating, suction, in-site test