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Adhesion of Polymer Coatings
Published in Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai, Suchart Siengchin, Polymer Coatings, 2020
S. Verma, S.K. Nayak, S. Mohanty
Wetting is defined as the spreading of liquid over the solid surface and establishing a close contact with it. To ensure complete wettability, the grooves, roughness, or crevices created over the substrate surface should be filled up by the polymer coating before the entrapment of air leading to the formation of air pockets. Subsequently, this air entrapment results into the formation of weak boundary layer over the substrate surface hindering the adhesion phenomenon. Besides wetting the substrate, polymer coating in its liquid state must be stable to flow and reach the substrate surface at micro- and nanolevel to avoid gas pocket occlusion (Petrie 2000). Apart from wettability, to fulfil the criteria of proper spreadability of the polymer coating over the substrate, these basic universal requirements should always be considered prior to casting/spraying (Petrie 2000): Cleanliness of the substrateWetting of the substrateSolidification of the polymer coating over the substrate forming an adhesive jointGeometry of polymer coating after solidifying should be free from environmental stresses
Water content and soil suction in the capillary zone
Published in H. Rahardjo, D.G. Toll, E.C. Leong, Unsaturated Soils for Asia, 2020
W.N. Houston, S.L. Houston, D. Al-Samahiji
It is well established that the mechanical properties of soil are water content dependent. Although soil properties such as shear strength and compressibility are normally the most inferior when the soil is wettest, it is also typically true that significant changes in water content, particularly from dry to wet, are the greatest source of engineering problems. Urban development results in changes in both surface and subsurface water regimes. Infrastructure construction, such as the building of highways tends to modify surficial and groundwater flows. Construction associated with urbanization normally results in local or regional groundwater table rise and increases in water content of the near-surface soil, especially in arid climate regions. Wetting of initially dry soils may be due to downward infiltration from a surface source, rising groundwater table, or capillary rise.
General report: Engineering behaviour and properties of arid soils
Published in P.G. Fookes, R.H.G. Parry, Engineering Characteristics of Arid Soils, 2020
Factors which tend to encourage collapse on wetting include a high void ratio (for the particular value of net stress) and an open or heterogeneous soil structure where some of the individual void spaces are relatively large. A high void ratio and an open soil structure can be produced by a particular depositional process or can be sustained by the existence of bonding between particles. Conversely, factors which tend to encourage swelling on wetting include a low void ratio (for the particular value of net stress), a relatively homogeneous soil structure and the inclusion of a high clay content, particularly clay minerals which hydrate and expand on wetting. Gourley, Newill and Schreiner (this volume) refer to the “intrinsic expansiveness” of a soil, attributable to the nature and proportion of the clay minerals rather than to any particular stress history or soil structure, and they provide a possible correlation between this intrinsic expansiveness and the Atterberg limits of the soil.
Instability analysis of a quaternary deposition slope after two sudden events of river water fluctuations
Published in European Journal of Environmental and Civil Engineering, 2023
Yue Zhou, Shun-chao Qi, Lei Wang, Ming-liang Chen, Chen Xie, Jia-wen Zhou
In the process of twice events (twice blockages of the river associated with twice landslides), the upper reach of Ouqu River was significantly affected by both flood fluctuations. After the first event, a great landslide dammed lake was immediately formed with the water level in the Ouqu River increased to historically high value, the natural soils at the river bank was submerged into the water for the first time since a quite long time ago, as the flood was estimated to be a once-in-ten-thousand-year flood. It is well known that wetting could lead to reduction in soil’s shear strength/resistance, due to various reasons, for instance, the loss of bonding effect provided by the meniscus water (Wheeler et al., 2003; Qi et al., 2017; Qi & Vanapalli, 2018; Qi et al., 2019). However, significant slope failures and/or collapses along the Ouqu river were not commonly observed. After the second event, a great number of landslides in various types (e.g. rotational sliding and collapses) were observed along the banks of Ouqu river (as shown in Figure 3), which have caused substantial damages to the village road. This might be the direct consequence of a much greater volume of the landslide-dammed-lake and larger rise of the water level, in other words, inundation-induced strength loss has extended to a greater area in the bank soils along the Ouqu River. Site investigations have reported other damages to the different infrastructures, for example, the Gangbai Highway in Jinsha Township was submerged for about 500m. The bridge leading to Jinsha Township was flooded, and the village road to Bagi Village was submerged.
Simulation of chloride ion transport in concrete under wetting–drying cycle
Published in Journal of Sustainable Cement-Based Materials, 2020
Tongning Cao, Lijuan Zhang, Guowen Sun, Caihui Wang, Ying Zhang, Na Yan, Aoxue Xu
In fact, the essence of the deterioration of structural concrete under the condition of drying-wetting cycles is that the porosity, saturation and tortuosity of concrete have changed, which eventually leads to the change of water and chloride transport paths. The transport coefficients established in the model should not only be directly related to the porosity and tortuosity of concrete, but also vary with the change of the characteristic parameters of microstructure. In addition, the chloride ion concentration distribution predicted in the current model is for one-dimensional transport, while the beam column of marine concrete is often subjected to two-dimensional or three-dimensional erosion in the service environment. In the two-dimensional boundary area, the chloride ion concentration tends to sudden change, which is very important to the life prediction of structural concrete. It is very significant to carry out the two-dimensional transport characteristics of chloride ions in concrete under the drying–wetting cycle. Therefore, in order to predict the service life of concrete, a two-dimensional transport model of chloride ion is established in concrete under drying–wetting cycle.
Wetting-induced axial and volumetric strains of a sandstone mudstone particle mixture
Published in Marine Georesources & Geotechnology, 2019
Zhenfeng Qiu, Junjie Wang, Shiyuan Huang, Jiping Bai
The deformation induced by wetting can be affected by confining stress, wetting stress, dry density, and soil types. In the present study, the effects of confining stress and wetting stress on the wetting deformation were investigated. The specimens were tested under varying levels of the confining stress and deviator stress ratio at wetting S. In the wetting triaxial tests, the samples were shear to a constant deviator stress and the deformation of the samples under wetting was recorded. This constant wetting stress can be calculated by the deviator stress ratio. The deviator stress ratio at wetting S is defined aswhere is the deviatoric stress during the wetting process, and is the deviatoric stress at failure in the dry-sample triaxial tests. In the current study, in addition to the zero-equivalent deviator stress ratio at wetting, three ratios were selected for the tests: 0.25, 0.5, and 0.75. Additionally, four confining stresses were selected for the tests: 100, 200, 300, and 400 kPa.