Abstract: The settlement of high backfill foundation in deep ravine of Q2 and Q3 loess under natural moisture content and saturated conditions was investigated based on the centrifuge testing. A large-scale centrifugal model test was carried out to simulate the behaviors of the high backfill foundation in its construction and post-construction periods. In this test, the intact loess and disturbed loess were selected as testing materials. It is shown that the settlement deformation of the high backfill foundation mainly occurs in the construction period, and the settlement rate increases with the filling height. After the test, the settlement trough can be clearly seen on the top of the foundation. The maximum settlement occurs in the middle of the filling body. The deformation on the gentle slope with the joint of the filling body and the original foundation is smaller than that on the steep slope. Under the natural moisture content, the total settlement is small, whereas the differential settlement is large. In contrast, the deformation under the saturated condition shows different characteristics, and the foundation is less stable. Differential settlements can yield a rupture between the original foundation and the filling body, so that the joint zone needs special treatments during construction period to improve the constraint of the filling body. It is suggested here that a certain reserved height of the filling body should be determined by the end of the filling process, and then measures must be taken to avoid the post-construction cracking owing to large differential settlement deformation.

Key words: soil mechanics, collapsible loess, centrifugal model test, high backfill foundation, settlement deformation, intact loess