3D failure of a scale-down dry stone retaining wall: A DEM modelling

Abstract

Dry stone retaining walls are vernacular structures that can be found in many places around the world and were mainly built to reduce slope erosion and to allow agricultural practices. Their stability is essentially warranted by the global wall weight and the capacity of individual blocks to develop friction at contact. The arrangement of these hand-placed blocks contributes also to the stability of the wall. A new interest arose in these structures in the last years, first due to the necessity to repair damages inherent to any built heritage, but also to their possible advantages regarding sustainability. Several studies have tried to address the behavior of slope dry stone retaining walls, whereas few conclusive studies have been performed concerning road dry stone retaining walls. In this latter case, the loading implies, apart from the backfill, the existence of a concentrated force on the backfill surface. The failure of such masonry work is accompanied by true three-dimensional deformations. This study is a first attempt to provide a better understanding of the mechanical behavior of road dry stone retaining walls. It involves a small-scale prototype with clay bricks for the wall, and steel blocks, acting as a concentrated loading on the backfill surface at a given distance from the inward wall face. Steel blocks have been superposed until wall failure. A numerical study based on these experiments is then performed by means of a mixed discrete-continuum approach. The numerical model was able to retrieve the average value of the concentrated force triggering failure found in the experiences, except when the concentrated loading is very close to the wall. Nevertheless, the results provided by this study are considered as encouraging even if further work is required to definitely state about the validity of such a numerical technique for the study of actual road dry stone retaining walls.

Experimental and numerical studies on scaled-down dry-joint retaining walls: Pseudo-static approach to quantify the resistance of a dry-joint brick retaining wall

“…−3 . The friction coefficient between brick layers has been previously experimentally evaluated to 32° ± 2° (Quezada et al, 2016). Hostun sand had a mean unit weight of 13.2 .…”

“…−3 corresponding to a relative density R D of 4%. The internal friction angle of the sand has been taken equal to 32° according to Quezada et al (2016). The friction coefficient of the interface between the wall and the backfill has been identified during this experimental campaign (Savalle et al, 2018a).…”

“…The bricks were modelled as fully elastic as failure surface was supposed to follow the joints. The backfill was assumed to follow a Hooke's law, with parameters drawn from a previously similar numerical 3D study (Quezada et al, 2016). Plasticity in the backfill follows a Mohr-Coulomb's law.…”

“…An additional local damping of 5% was added to stabilize the numerical simulations (Kamai and Hatzor, 2008;Oetomo, 2014;Quezada et al, 2016). This value is rather small for a static study but higher values showed a tendency to mask the minimal inclination angle leading the system to an unstable state and then to failure.…”

“…The elastic parameters of the wall-backfill system (bulk and shear modulus of the bricks, bulk and shear modulus of the backfill, stiffnesses of joints) were determined following either a previous study (Quezada et al, 2016) or UDEC manuals (e.g. classical values used for joint stiffnesses).…”