3D Numerical Analysis of the Interaction of Back-to-Back Reinforced Soil Walls Analyse Numérique Tridimensionnelle de l’Interaction des Murs de Soutènement à Parements Opposés en sols Renforcés.

Abstract

Back-to-back Reinforced Soil Walls are among complex geometry structures and are commonly used in ramp ways, rock fall protection systems, earth dams, levees, noise barriers and especially for bridge abutment approach. However, available design guidelines for this type of walls system are limited. Advanced computational models based on finite element and/or finite difference methods allow researchers to gain a better knowledge of these systems and anticipate the opposite side walls performance under operational conditions. Firstly, a Two-dimensional (2D) modelling by the finite element (FE) code PLAXIS of the quantitative influence of problem geometry, strip pre-tensioning, strip type, and surcharging on horizontal displacements, development of soil shear and plastic zones, lateral earth pressure, and maximum reinforcement loads compared with the analytical international codes (i.e., NF, AASHTO Simplified Method and AASHTO Simplified Stiffness Method). The numerical results demonstrate how this type of reinforced soil walls perform jointly at a certain distance of interaction between the two opposite walls. The walls of the two opposing sides clearly interact with each other when they are close enough and with an overlapping reinforcement layout. Pre-tensioning load can contribute to achieving vertical wall-facing alignment at the end of construction. Using perforated/holed strips, the tensile loads at the end of construction were reduced by about 30% due to the improved polymeric–soil interface strength and stiffness. Secondly, a Three-dimensional (3D) modelling by code PLAXIS to investigate the behaviour of back-to-back reinforced soil walls in case connected to bridge abutment at end of construction and under bridge load application, by comparing the predicted results of the 3D-FE analysis in terms of wall displacement, Lateral earth pressure, reinforcement loads and potential failure surface with those predicted using the 2D-FE analysis. The 3D results indicated that the farther away from the abutment wall (i.e., the corner), the nearest the 2D results at end of construction and under bridge load application. The 3D results at near the corner are more conservative than 2D under bridge load application due to the dead loads (i.e., bridge seat & bridge deck load) which is not taken into account in 2D simulations.