Plasticity-Based Analysis of Reinforced Soil Structures

Reinforced soil structures are typically analyzed for stability using limit equilibrium calculations. Results from such analyses are sometimes ambiguous because of different assumptions made in addition to the presumption of the limit state. These ambiguities can be removed if the kinematic approach of limit analysis is used, in which a rigorous bound to a limit load, or a bound to the required strength of reinforcement, is sought. The required strength of reinforcement is the strength needed to maintain stability of the structure. The kinematic approach involves calculations of work dissipation in the soil and reinforcement as two separate terms in the energy balance equation. An alternative method includes description of reinforced soil as an anisotropic continuum. Because limit analysis provides a rigorous bound to the reinforcement strength, limit loads, or a safety factor, the geometry of the failure mechanisms considered can be optimized, so that the best bound is obtained (a solution closest to the exact solution). Considerations can be extended to calculations of critical accelerations of reinforced slopes subjected to seismic loads. Also, permanent displacements can be calculated using limit analysis with rigid-block time integration. Some fundamental aspects of plasticity-based analyses of reinforced soil will be discussed.