Short-term thermo-mechanical numerical modelling of reinforced soil walls with polyester strap reinforcements

Polyester (PET) materials have become more common as reinforcement solution in reinforced soil walls (RSW). It has been shown that strength and stiffness of geosynthetics products, including PET, is load-, time-, and temperature-dependent. Consequently, the mechanical response of these materials is influenced by in-soil conditions. The present study describes viscoelastic and visco-plastic constitutive formulations used to model PET strap reinforcement layers in thermo-mechanical finite element models. The models are demonstrated using an idealized 15-meter high RSW with concrete facing panels, including loading due to a road at the top of the structure. Reinforcement model parameters were calibrated using laboratory measured data. Analyses include temperature boundary conditions representing a Mediterranean climate for a 1-year period following end of construction. Calculated stress and strain values were in accordance with values found in the literature. The results of this study are a precursor for the long-term modelling of RSWs under operational conditions subjected to changing atmospheric boundary conditions.The authors wish to thank Aaron Kim from GECO Industrial (Korea, Rep.) for providing polymeric strap data from manufacturing quality control records. The authors wish to acknowledge the support of the Department of Civil and Environmental Engineering (DECA) of the Universitat Politécnica de Catalunya�����BarcelonaTech (UPC) and the International Centre for Numerical Methods in Engineering (CIMNE) and the funding received from the Spanish Ministry of Economy and Competitiveness through the “Severo Ochoa Programme for Centres of Excellence in R&D” (CEX2018-000797-S-20-4).Peer ReviewedPostprint (published version

Simplified approach to analyse global stability of reinforced soil walls

Reinforced soil walls (RSW) are a proven alternative to conventional earth retaining structures due to their rapid construction, smaller environmental impact, lower cost, as well as more sustainable social/functional features. Design methods for RSW appear in international codes and guidelines. However, they often do not provide detailed calculations for global stability assessment. Global stability can significantly affect RSW design for specific geometric cases and/or site-specific boundary conditions. Traditional limit equilibrium (LE) methods have the disadvantage of not considering reinforcements and/or require iterations to achieve a safety factor (SF) value. Alternatively, numerical methods can be time consuming for both model generation, particularly for complex geometries, and during calculations. The present study discusses different analytical strategies using limit equilibrium formulations and a numerical finite element method, and proposes a simplified analytical method for global stability analysis based on a three-part wedge failure mechanism, and simple wall conditions.Peer ReviewedPostprint (published version

Comparison of geosynthetic reinforced soil wall solutions using analytical design methods and numerical modelling

European design standard (prEN-1997 202x) permits the use of suitably verified numerical models for the design of reinforced soil walls (RSW). The paper first compares three analytical design method outcomes (Coherent Gravity, Simplified, and Stiffness method) available in US (AASHTO 2020) and Canadian (CSA 2019) design codes. Polyester (PET) strap reinforcement arrangements from each method were then simulated using a 2D finite element model (FEM) which considered construction stages and transient compaction conditions. The models for each arrangement were analyzed using different material factors applied to the soil frictional strength. Serviceability limit states (SLS) and ultimate limit states (ULS) were evaluating via horizontal wall deformations, soil shear strains, and maximum reinforcement tensile loads. Numerical results remained within SLS and ULS criteria. The maximum tensile loads from the numerical models were close to, but lower than the predicted loads using the Stiffness Method, which in turn were lower than the loads predicted using the Simplified and Coherent Gravity methods.Peer ReviewedPostprint (published version

Coupled modelling of environmental in-soil conditions and their effects over polyester straps reinforced soil structures

Polyester (PET) strap reinforcement materials are being routinely used as soil reinforcement for mechanically stabilized earth (MSE) walls. Strength and stiffness of the polyester fibres can be expected to decrease with increasing temperature and in the presence of moisture. By using numerical simulations, mean in-soil temperature values could be approximated to the mean atmospheric yearly value with diminishing fluctuation with increased depth. In-depth relative humidity values were found to present a constant behaviour for three of the four imposed boundary condition. Temporal variations in the response of PET straps were adequately modelled with viscous models within different soil environments.Postprint (published version

Strength reduction analysis in polymeric reinforced soil walls

The latest revision of EN-1997 allows for the use of numerical tools to design geotechnical structures, provided limit state conditions are thoroughly evaluated were analysis of the construction and post-construction stages must be included. Regarding ultimate limit state conditions, material factors must be used as to evaluate the effect of soil strength reduction on the performance of the structure. The present study focuses on the design of an idealized 10.5 m-tall reinforced soil wall with discrete concrete facing panels and polymeric strip reinforcements using finite element tools. A manual strength reduction analysis was performed, which showed no sign of structural failure, but rather hints of probable failure mechanisms which may occur, provided the structure is subjected to further unfavorable conditions.Postprint (published version

Modelling the effect of in-soil temperature and relative humidity on performance of PET strap soil reinforcement products

Polyester (PET) strap reinforcement materials are now used routinely as soil reinforcement for mechanically stabilized earth (MSE) walls. Strength and stiffness of the polyester fibres can be expected to decrease with increasing temperature and in the presence of moisture. This study presents the results of analyses using numerical simulations that were carried out to estimate, first, the in-soil temperature and relative humidity changes for different ground properties and atmospheric boundary conditions, and second, the temporal strength and stiffness changes in simulated buried PET straps placed in different soil environments while subjected to different tensile loads and temperatures.Postprint (published version

A Search for Low-mass Dark Matter via Bremsstrahlung Radiation and the Migdal Effect in SuperCDMS

In this paper, we present a re-analysis of SuperCDMS data using a profile likelihood approach to search for sub-GeV dark matter particles (DM) through two inelastic scattering channels: bremsstrahlung radiation and the Migdal effect. By considering possible inelastic scattering channels, experimental sensitivity can be extended to DM masses that would otherwise be undetectable through the DM-nucleon elastic scattering channel, given the energy threshold of current experiments. We exclude DM masses down to $220~\textrm{MeV}/c^2$ at $2.7 \times 10^{-30}~\textrm{cm}^2$ via the bremsstrahlung channel. The Migdal channel search excludes DM masses down to $30~\textrm{MeV}/c^2$ at $5.0 \times 10^{-30}~\textrm{cm}^2$.Comment: This paper is being withdrawn due to an error in data selection during the analysis. Although incorrect, the limits are roughly representative of the sensitivity. The new corrected version of the result will be uploaded once read