Study on stress and deformation characteristics of existing-new two-stage cantilever retaining wall

A two-stage cantilever retaining wall is composed of two single-stage cantilever retaining walls, which are stacked up and down. The structure not only has the advantages of a single-stage retaining wall, but also compensates for the shortcomings of the height limit of the single-stage retaining wall; therefore, it has been gradually applied in projects. Based on the actual project of Zhongwei-Lanzhou Passenger Dedicated Line into Lanzhou Hub, this paper studies the influence of the construction of new cantilever retaining wall and the filling of subgrade on the deformation and earth pressure of the new cantilever wall and the existing cantilever wall by means of field test and numerical simulation. The results show that with an increase in the filling height after the new cantilever wall (upper wall), the horizontal displacement of the top of the upper and lower walls increased nonlinearly. The displacement direction of the upper wall was the filling direction, and that of the lower wall was the deviation from the filling direction. The higher the filling height, the greater is the displacement. With an increase in the filling height, the earth pressure behind the upper wall increases gradually along the wall height and decreases slightly to the bottom of the wall, which is approximately a linear distribution. The earth pressure behind the existing cantilever wall first increases along the wall height and gradually decreases after reaching a certain depth, but the earth pressure of the lower wall does not increase significantly with an increase in the filling height behind the upper wall. The slope failure mode is the overall sliding failure of the retaining wall together with the fill soil. The sliding surface passed through the lower edge of the lower wall heel and was similar to an arc shape. The stability of the two-stage cantilever retaining wall was better than that of a single-stage retaining wall. Finally, a calculation method for the overall stability and earth pressure of the existing two-stage cantilever retaining wall was proposed.