## 5 Conclusions  
This study evaluated the apparatus scale effect on the pullout response of a geogrid in cohesive soils through monotonic and cyclic/post-cyclic pullout tests subjected to different applied normal stresses. Based on the obtained results, the following conclusions can be highlighted:  
* In general, in the small-scale tests, no significant deformation occurred over the back half of the reinforcement, as opposed to the large-scale tests, where the geogrid displacements decreased progressively with the distance to the front end, showing a progressive mobilization of the interaction mechanisms at the interface. * Particularly under lower applied normal stresses, the geogrid pullout resistance was considerably influenced by the apparatus scale and higher values were reached in the large-scale tests. However, the scale effect became less prominent when the applied normal pressure increased. Under post-cyclic loading conditions, the effect of apparatus scale on the pullout resistance values followed the same trend as that observed under monotonic loading. * Despite the variability for the pullout resistance, the maximum shear stresses obtained from both types of equipment showed reasonable agreement. * Under normal stresses of 25 and 50 kPa, the geogrid's confined stiffness at low strains (<2%) derived from the small-scale tests exceeded that from the large-scale equipment. However, under a higher normal stress (100 kPa), the values of confined tensile stiffness obtained from both equipment types were consistent. * The pullout interface's apparent coefficient of friction (\(\mu\)s/GSY) decreased with increasing normal stress. While for \(\sigma_{\text{n}}\) = 25 kPa, the \(\mu\)s/GSY values obtained from the small-scale tests exceeded those from the large pullout box, under higher normal stresses, the differences between the \(\mu\)s/GSY values associated with different test devices were not significant. The inclusion of geosynthetics in civil infrastructure projects enables significant energy and natural resource savings, thus addressing the global sustainability requirements. Furthermore, the assessment of soil-geosynthetic interaction parameters using small-scale pullout test equipment represents significant benefits, including a reduced consumption of resources, reduced cost, and an easier and faster test assembly, in comparison to conventional large-scale tests. The presented results highlight the importance of the scale effect in pullout tests, while also considering the influence of the applied normal stress. When the pullout resistance is estimated on the basis of small-scale pullout tests, proper scale effect correction factors may be considered for more consistent estimates of the soil-geosynthetic interface strength parameters. S.R.B. : Data curation, writing--original draft preparation, methodology, resources and conceptualization; G.O.M.P. : conceptualization, writing--original draft preparation, review and editing; F.B.F. : formal analysis, writing--original draft preparation, review and editing; J.L.d.S. : resources, project administration, supervision and writing--review and editing. All authors have read and agreed to the published version of the manuscript. This research was funded by: Process 405594/2022-4. CNPq/FNDCT/MCTI 15/2022--Desempenho de paymentos estabilizados com geossinteicos: uma abordagem experimental e numerica; Grant No. 2021.03625.CEECIND/CP1679/CT0002 with DOI 10.54499/2021.03625 accessed on 3 August 2024. CEECIND/CP1679/CT0002 from the Stimulus of Scientific Employment, Individual Support (CEECIND)--4 th Edition, provided to F.B.F. by Fundacao para a Ciencia e Tecnologia (FCT); and Base Funding--UIDB/04708/2020 with DOI 10.54499/UIDB/04708/2020 ([[https://doi.org/10.54499/UIDB/04708/2020](https://doi.org/10.54499/UIDB/04708/2020)]([https://doi.org/10.54499/UIDB/04708/2020](https://doi.org/10.54499/UIDB/04708/2020))) accessed on 3 August 2024 of the CONSTRUCT--Instituto de I&D em Estruturas e Construcoes--funded by national funds through the FCT/MCTES (PIDDAC).