Stability analyses of a reinforced soil wall on soft soils using strength reduction method

• The stability of a built-to-failure RSW on soft clay was captured by the SRM.
• The stability of RSWs on soft soils can be improved by extending the bottom layers.
• Upper bound strength and stiffness exist for a certain length of the extended layers.
• Ignorance of reinforcement strength may overestimate the stability of RSWs.

A two-dimensional coupled mechanical and hydraulic finite element (FE) modeling was performed on a 7.6 m high built-to-failure reinforced soil retaining wall (RSW) on very thick soft clay. The observed ground settlement, toe displacements, and the deep-seated global failure of the RSW were well captured with the FE modeling and the Strength Reduction Method (SRM) incorporated in the FE program. The effects of extending, strengthening and stiffening bottom layers of the reinforcement on the stability of the RSW were further investigated by using the calibrated modeling. The results show that the stability of the RSWs on soft soils can be apparently improved by extending the bottom reinforcement layers. By increasing strength and stiffness of reinforcements, fewer bottom reinforcement layers need to be extended to maintain the stability of the structures. There are upper bound strength and stiffness values for a certain length of the extended reinforcements, beyond which the increments of strength and stiffness will have little effect on the stability. Reinforcement strength should be considered in numerical modeling of reinforced soil structures when the reinforcement strength is less than the upper bound value and internal and compound stabilities are concerned. Ignoring reinforcement strength may lead to overestimation of the stability of the structures. For a safe and economical design, RSWs on soft soils can be reinforced with relatively shorter, low strength and stiffness reinforcements at upper layers while with relatively longer, high strength and stiffness reinforcements at bottom layers.