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Item type:Publication, Access status: without files , The hydro-mechanical interaction in novel polyurethane-bound pervious pavement by considering the saturation states in unbound granular base course(2022); ; ; ; The pore-water pressure generated by intermittent dynamic vehicle loading under various saturation states is recognized as a critical factor influencing the behaviour of permeable pavement structures, especially the behaviour of UGB layer. However, the underlying mechanisms of hydro-mechanical interaction in the UGB layer and the influence on the pavement structure are still unclear. This study aims to characterize the changes in dynamic response in permeable pavement structures under various saturation conditions by considering the hydro-mechanical interaction within the UGB layer. To achieve this objective, a full-scale test track with a PUPM wearing course was constructed. Pressures and water distribution were characterized by embedded sensors within different layers of the test track when subjected to the accelerating pavement test. Based on the coupled SAME model, the water distribution and the dynamic response of UGB in the rainfall events were both characterised and solved by FEM. The results predicted by the proposed SAME model correspond to the field measurements, and the influence of the water content on the resilient modulus distribution within the UGB layer was then estimated. Based on the predictions for the stress state of the UGB layer, the sensitivity analysis was also proposed.Publicationtype: Journal Article50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , In-situ and numerical investigation on the dynamic response of unbounded granular material in permeable pavement(2020-12); ; ; ; Permeable pavements have been widely used as an effective means to improve hydrological characteristics and the ecology of the urban environment. This study aims to investigate the response of fully permeable pavement (FPP) subjected to dynamic loading under dry and saturated conditions. A full-scale test track topped with polyurethane bound permeable material (PUPM) was built to obtain the stress response with an accelerated pavement test (APT) system. In addition, comprehensive analyses were performed based on the coupled Stress-dependent Moisture-sensitive Cross-anisotropic Elastoplastic (SMAEP) model in FEM. The APT test showed that the worst state was observed when the pavement structure was fully saturated, and that and brittle failure of the pavement surface occurred when the critical load level was achieved. The prediction of vertical stress predicted by Stress-dependent Cross-anisotropic Elastic (SAE) and SMAEP were both validated with the field data. The horizontal stress predicted by SAE gave a very high and unreasonable tensile stress prediction at the bottom of the unbounded granular base (UGB) layer when subjected to the high load level. With the consideration of moisture effect and the plastic properties of the material, the prediction made by SMAEP is effective to estimate the dynamic response of the UGB layer. Based on the sensitivity analysis, the optimized designs for FPP based on PUPM were suggested.Publicationtype: Journal Article123 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Dynamic Response of Fully Permeable Pavements: Development of Pore Pressures under Different Modes of Loading(2020-07-01); ; ; ; Permeable pavements are widely recognized as an effective way to improve the environmental and ecological aspects of conventional dense pavements. Based on traditional pavement materials, permeable pavements are often designed to be partially permeable or to consist of merely permeable surfaces. Recently, the development of novel polyurethane-bound pervious mixtures (PUPM) has made the widespread application of fully permeable pavement (FPP) structures possible, which will increase the environmental benefits of permeable pavements. In this case, the saturation of a pavement has a major influence on the performance of FPP. The generation and dissipation of pore pressure is recognized as a critical factor, influencing the bearing capacity of permeable pavement structures. In literature, only few studies focus on the pore pressure in permeable pavements under traffic loading. This study aims to measure and characterize the changes in pore pressure in a full-scale permeable pavement under various saturation conditions under traffic loading. To achieve this objective, pore pressure data was collected from laboratory testing as well as from a full-scale test track constructed with a polyurethane-bounded pervious mixture (PUPM) wearing course. Based on this study, it is found that when permeable pavement material is subjected to cyclic loading, the pore water pressure is much larger than the pore air pressure; in fact, the latter is found to be negligible. During the irrigation process and dynamic vehicle loading, the pore water pressure increases as the saturation increases. The changes of pore water pressure are not obvious in the PUPM surface layer when comparing the results to the pervious layers below the wearing course. Under cyclic vehicle loading, the accumulated pore water pressure of each layer increases with the number of loading cycles and also increases as the saturation increases. These findings support the quest for an in-depth understanding of the stress state and the degradation mechanisms in FPP. The results provide practical conclusions and recommend optimized design properties for a wide application of FPP.Publicationtype: Journal Article82 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Numerical analysis for the influence of saturation on the base course of permeable pavement with a novel polyurethane binder(2020-04-20); ; ; ; Permeable pavements represent an effective approach to optimize the conventional sealed pavement infrastructure. Compared to sealed pavement structures, the porous pavement structure allows fluids to pass through it freely, reducing and controlling runoff in the surrounding area. The stress state of this pavement system under different saturation conditions is one of the most important challenges for the pavement design. This study aims to develop a modulus-reduction method for the pavement material under different saturation conditions by considering hydro-mechanical interaction. To achieve this, a full-scale permeable test track was constructed in this study. A falling weight deflectometer (FWD) was used to measure the deflection of the test track at different saturation states. Using the back-calculated elastic parameters, tire-pavement interaction models were created to conduct finite element method (FEM) simulations of the stress state of the test track subjected to the loads from Accelerated Pavement Testing (APT). The results show that the hydro-mechanical properties of the test track are significantly affected by the water content. As a result, the current design algorithm of fully permeable pavements should consider the effects of saturation to allow for improved designs of fully permeable pavements.Publicationtype: Journal Article102 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Investigations on microstructure characteristics of porous pavement based on X-ray CT scanning(2019-08); ; ; Gathering insights on materials at pore scale using digital imaging techniques, such as X-ray computed tomography (CT), gains more and more attention in various fields of engineering disciplines. The better understanding of material properties, internal structures, and material behaviour has generated many scientific and industrial advances. Investigations on porous materials, especially the visualisation of the pore space, allow the derivation of macroscopic material properties and provide a basis for numerical calculations, e. g. flow or contaminant transport through threedimensional pore structures. The investigated porous material in this study is used in water-permeable road constructions as a novel pavement material aiming at instant drainage of rainfall into the subgrade and subsoil. Commonly used porous asphalt is made utilising bitumen-based binder materials. In this case, however, an innovative binder material based on polyurethane (PU) is used to form a flexible and porous pavement layer. The utilisation of this binder material not only increases the functionalities of the pavement layer but also increases rutting resistance and fatigue behaviour. This paper gives insights on the pore space obtained from CT-scans of two different pavement compositions of novel porous pavement material. The compositions vary in terms of particle size distribution of the utilised grains and the maximum grain diameter. The segmentation process of the obtained CT-images into the components of the multiphase media, i. e. grains, pore space, and binder material, as well as the reproduction of the three-dimensional models will be presented. Also results of investigations on the representative elementary volume for two volume-dependent properties will be demonstrated.Publicationtype: Conference Paper25 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Hydraulic properties of polyurethane-bound permeable pavement materials considering unsaturated flow(2019-07-10); ; ; ; Constant urban and infrastructural growth leads to increased sealing of areas in municipal areas. This surface sealing results in distortions of the natural water cycle, which again can lead to noticeable changes in the natural ecosystem. To counteract the effects of surface sealing, innovative permeable road structures provide a promising environment-friendly opportunity. An innovative highly permeable road surface material based on alternative binders using polyurethane (PU) to replace the conventionally used bituminous binders has been developed in the course of an ongoing research project. It is intended that the high permeability of the road's surface material and underlying support layers leads to a quick drainage through the road construction down to the subsoil. The aim of this study is to understand and quantify the relevant hydraulic properties of PU-bound road surface material, i. e. the water retention behaviour and the hydraulic conductivity in saturated and unsaturated states. A predictive model to determine the surface material's water retention behaviour was used as a first estimation and very low air entry values were observed. Results from laboratory experiments on the material's saturated hydraulic conductivity as well as the water retention behaviour in the low suction range are presented. Additionally, empirical hydraulic models to describe the retention behaviour and models for the saturated and unsaturated hydraulic conductivities are outlined and applied.Publicationtype: Journal Article834 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Measurement of hydraulic properties of unsaturated permeable polyurethane bound asphalt materialsIn order to reduce the far reaching consequences of surface sealing, the use of permeable pavements is increasingly gaining importance especially with regard to sparing the natural resources, groundwater, soil and the climate. Permeable Polyurethane (PU) bound asphalt pavements are currently the most effective high-tech construction method for environmentally friendly transport infrastructures and modernwastewater management. Because of the enhanced permeability of such pavements, the design of the sub-construction requires specific attention. An unexplored approach is to install the permeable pavements directly on the unbound subsoil, in order to drain the accumulated water completely. The infiltration of the rainwater through the construction leads to an increased water supply in the subsoil. However, the hydro-mechanical interaction of the porous PU-asphalt structure and the subsoil is still unknown. To gain primary insights into this mechanism the hydraulic properties of different PU-bound asphalt mixtures are analyzed focusing on the Soil-Water Characteristic Curve (SWCC) and the hydraulic conductivity.The air entry value of highly porous structures is estimated to be quite low, leading to challenges when measuring small-scale suction. In this paper first results of laboratory tests are presented.Publicationtype: Conference Paper86