Study on shear strength and deformation characteristics of sandy silt improved by cement under hydrothermal action

At present, researches on the stability of sandy silt improved by cement (SS-C) are abundant, but there are few researches on the shear strength and deformation characteristics of it under the conditions of low temperature and different moisture content in cold regions. Firstly, sandy silt was selected as the research object, which the liquid limit (wL) is 28.6% and plasticity index (IP) is 8.9, the coefficient of nonuniformity (Cu) is 61.5, and the optimum cement incorporation ratio was determined as 6% according to the maximum direct shear strength at − 7 ℃. Secondly, the SS-C was tested by direct shear at different temperatures (−2 ℃, −5 ℃, −7 ℃, −14 ℃) and moisture contents (13.0%, 15.2%, 18.0%). Subsequently, the effects of temperature and moisture content on shear strength and shear modulus were calculated and analyzed. The results show that when the temperature drops from − 2 ℃ to − 7 ℃, the cohesion of the SS-C increases by 243.4%; when from − 7 ℃ to − 14 ℃, it continues to increase by 285.7% compared with that at − 2 ℃, and the internal friction angle of the SS-C also shows a similar variation law with the temperature. At − 7 ℃, when the initial moisture content increases from 13.0% to 15.2%, the increase of cohesion is about 8.6%; when from 15.2% to 18.0%, it is about 22.8%, while the change of internal friction angle is less than 1%. Finally, the impact of hydrothermal action on the failure ratio of the SS-C was analyzed, and the relation equation between shear strength and tangent elastic modulus of the SS-C was established.