Abstract: The mud cake blocking at the cutter head will slow down the construction progress of the shielded excavation and event result in serious accidents such as excavation failure and other geohazards. In order to study the effect of hydro-chemical-mechanical coupling on the flow plasticity and the strength of shielded cutter slurry, CaCl2 solutions with different concentrations, such as, 0 mol·L^-1, 0.5 mol·L^-1, 1.0 mol·L^-1, were used to saturate the shield cutter mud cake samples. The mud cake samples after the saturation were tested for Atterberg Limits and modified direct shear tests. The test results show that the increase of the solution concentration can effectively reduce both the plastic and the liquid limits of soil samples; reduce the soil cohesion. However, the increase the solution concentration, the internal friction angle and the overall shear strength are increased. These changes might be the results of the thin water film incorporated at a high concentration; the soil sample’s water retention capacity becomes weak resulting in a decreased plastic limit. With the increase of the solution concentration inhibit soil electric double layer thickness, so that the soil particle agglomeration, the repulsion between the particles decreases, biting force among soil particles increases, thus weakening the cohesion, the internal friction angle increases.

Key words: shield cutter mud cake, salt solution, atterberg limits tests, direct shear tests