Centrifugal model tests on features of slip surfaces in backfill and earth pressures against balance weight retaining walls

Mastering the features of slip surfaces in backfill and earth pressures against the balance weight retaining wall with complex back shape is of great significance to improving the structural design. A set of wall displacement real-time controlled mechanism is developed, and geotechnical centrifugal model tests on three types of embankment filling heights with balance weight retaining walls are conducted. The deformation and fracture characteristics of backfill and the variation laws of earth pressure under translation mode are analyzed, and then the difference between the experimental data and the standard design values is compared. A modified method is proposed for the earth pressures based on the shearing state of slip surfaces to address the existing problems in the traditional models. The results show that when the active limit state is reached, only the slip surface towards the lower wall and the second slip surface towards the upper wall occur in the backfill, which is divided into three regions: translational soil, sliding soil and immobile soil. The shear stress of the first slip surface towards the upper wall does not reach the limit, which is the key factor causing the value of earth pressure tests on the upper wall to be significantly larger than the design value but smaller than that on the lower wall. By introducing a mobilization coefficient (η≤1) of internal friction angle (φ) for the first slip surface towards the upper wall, a modified pattern for calculating the earth pressures against the balance weight retaining wall is proposed to better reflect the influences of the stress declination angle (φ_η=ηφ) on slip surface dips and earth pressures against the upper and lower walls. With this improvement, the calculation-modified values are in good agreement with the experimental data.