Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Civil and Environmental Engineering | en_US |
| dc.contributor.advisor | Yin, Zhen-yu (CEE) | en_US |
| dc.creator | Pathak, Bidur | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/14180 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Experimental and numerical investigations of sand-epoxy coating effects on sand-GFRP interfacial shear behaviour | en_US |
| dcterms.abstract | Glass fibre-reinforced polymer (GFRP) composites have been widely used in engineering applications, including offshore structures, owing to their high strength-to-weight ratio and inherent corrosion resistance. However, their smooth surfaces and relatively low hardness can limit shear performance at the soil-GFRP interface. Surface modifications, such as sand-epoxy coatings, have been proposed to enhance surface roughness and hardness, thereby promoting mechanical interlocking and improving interface friction. This study aims to develop a comprehensive understanding of the shear mechanism at the sand-GFRP interface by systematically investigating the effects of GFRP surface type and roughness on shear and volumetric behaviour, as well as the evolution of surface roughness under cyclic shearing. | en_US |
| dcterms.abstract | A series of interface direct shear tests was conducted under both monotonic and cyclic shearing conditions. Air-dried standard silica sand was employed as the test material, in conjunction with uncoated GFRP plates and sand-epoxied GFRP plates featuring different concentrations and grades of epoxied sand. Three distinct GFRP surface types (i.e., smooth finish, rough finish, and sand-epoxied surfaces with differing sand concentrations) were examined to evaluate their performance under varying particle sizes, initial relative densities, sand proportions, and normal stresses. The optimal sand coating configuration was identified through monotonic testing, while long-term performance was assessed via cyclic testing. The frictional characteristics of the interfaces were analysed to elucidate variations in shear stress mobilisation, vertical deformation, and roughness evolution mechanisms under moderate to high normal stresses (200 kPa to 800 kPa). A discrete element method (DEM) simulation was performed to provide micromechanical insights into the sand-GFRP interface behaviour under constant normal stresses up to 200 kPa, focusing on contact evolution and roughness changes. Additionally, a finite element method (FEM) analysis using an enhanced hyperbolic constitutive model was implemented within ABAQUS, integrating user-defined subroutines to validate the experimental results. Model parameters were calibrated through a covariance matrix adaptation evolution strategy (CMA-ES), leveraging data from both monotonic and cyclic shearing tests. | en_US |
| dcterms.abstract | The results indicate that increasing the dosage of epoxied sand enhances the surface roughness of GFRP, thereby improving interlocking mechanisms and resulting in higher interface shear strength. Under cyclic shearing conditions, both mobilised shear stress and vertical deformation increased with cycle number, normal stress, and interface roughness. GFRP degradation and particle breakage became more pronounced as the median particle size increased. The evolution of roughness was attributed to mass sliding and rotation in smooth interfaces, whereas rotational effects and bonding-debonding mechanisms governed in rough surfaces. The application of sand-epoxy coating significantly enhanced surface hardness and relative roughness while effectively mitigating long-term degradation. Cyclic shearing exhibited higher interfacial friction angles than monotonic shearing due to the combined effects of surface degradation, particle breakage, interlocking, and stress redistribution at the interface under elevated normal stress. DEM simulations revealed that sand-epoxy coatings can increase peak friction angles by up to 37% and 98% for fine and medium sands, respectively, with force chain concentration being more evident in dense specimens. Interface slip decreased with increasing normalised roughness, and the roughest interfaces promoted diagonal force chain alignment, particularly under high normal stresses. FEM simulations demonstrated that the model effectively captured hardening behaviour and contraction but exhibited limitations in predicting softening and dilation under large deformations. Further refinements are needed to enhance the model's predictability. | en_US |
| dcterms.abstract | This research advances the characterisation of the sand-GFRP interface and informs the practical design of sand-epoxy coatings by integrating experimental investigations with numerical analyses, encompassing micromechanical and macromechanical modelling. The findings provide fundamental insights into interface contact mechanics and shear behaviour, forming a foundation for future developments in geotechnical applications involving GFRP composites and granular materials under diverse loading conditions, with potential for subsequent validation under environmental scenarios. | en_US |
| dcterms.extent | xxiv, 292 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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