Abstract: The characteristics of the slip surface of the soil are highly important for the calculation of earth pressure. In order to study the characteristics of the limited width soil active slip surface behind the rigid wall, laboratory model tests were carried out using non-cohesive sand, the images of soil during the test were collected and analyzed by digital image correlation method, the shear strain and displacement of soil are obtained, and the translation (T-mode) and rotation around the bottom of the wall are analyzed. The research results show that the critical aspect ratio of active soil with limited width is similar in T mode and RB mode, while in RT mode, the critical aspect ratio is relatively small; the active sliding surface of the soil with limited width in T mode presents the characteristic of "multi-refraction lines". According to the similarity of the sliding angle, it can be divided into the slip surface developed from the mobile retaining wall and the fixed retaining wall, the starting point of the active slip surface of limited-width soil in RB mode is the upper part of the wall heel, and the starting point of the RT mode is the wall heel, both of which extend to the middle of the fixed retaining wall. Obvious soil arch characteristics can be observed in the horizontal and vertical displacement of soil with limited width in T mode and RT mode, and the edge of soil arch is the sliding surface.

Key words: model experiment, soil of limited width, active displacement mode, slip surface, sand