Centrifuge modelling on the stability of emergency flood control riverbank reinforced by deep mixed column: Case Study of Baishan Junction, China

Cement deep mixing pile (CDM) are often used to improve the stability of embankments/riverbanks in soft soil areas due to the extremely low bearing capacity of natural soft soil foundations. Especially for riverbank filling for emergency flood control. In order to accurately identify the destabilization and damage characteristics of the riverbank reinforced by CDMs, centrifugal model test was conducted to investigate the settlement characteristic of the riverbank, the force and deformation properties of the piles at different locations, as well as the destabilization and damage mechanisms of the foundation under the high gravity field. The riverbank has two slopes, a primary slope and a secondary slope in that order from the top of the riverbank downward. The results indicate that the soil below the top of the primary slope was subjected to compression, and no large horizontal displacement occurred in this region. In addition, ground collapse has occurred near the toe of the riverbank slope. Besides the most dangerous sliding surface, there are still potential sliding bodies and sliding surfaces in the foundation. The soil slip surface and the points of failure in the columns were not completely coincident. After the column failure happened, it can be used as a fast drainage channel to accelerate soil consolidation. The piles under the top of the primary slope were mainly damaged in compression without large horizontal deformation; the piles under the shoulder of the primary slope to the shoulder of the secondary slope were damaged in bending failure and carried most of the horizontal loads; and the piles under the secondary slope to the riverbed were damaged in shear failure. According to the specific damage situation of the columns, rigid piles/strength core composite piles with higher bending strength can be considered to replace some of the CDMs to effectively improve current design methods for CDM-reinforced foundation.