GeoBarrier system (GBS) is a system that combines geobag wall with capillary barrier concept as stabilization method against rainfall-induced failure, and vegetation as green cover. This paper ...presents deformation behaviour of a GBS wall constructed as pilot study when subjected to rainfall infiltration. The GBS wall was 4 m high with 70° slope angle. The wall was subjected to uniform surcharge of 10 kN/m
2
and rainfall of 22 mm/h for 8 h. Recycled materials were used as components of the capillary barrier. Coupled deformation-seepage finite element analyses were carried out to evaluate the stress and pore-water pressure variations within and behind the GBS wall during and after rainfall. Limit equilibrium analyses were performed at various stages during and after rainfall to assess the near vertical wall stability. The results of the coupled deformation seepage analysis showed that the reinforced zone in the GBS remained unsaturated during rainfall, indicating that the GBS wall performed well in minimizing the rainwater infiltration. However, the GBS wall face deformation pattern altered during and after rainfall, indicating that the rainfall infiltration increased the lateral stress on the top part of the wall. The variation of lateral stress with depth agrees with field measurements from earth pressure cells.
The cultivation of rice, one of the most important staple crops worldwide, has very high water requirements. A variety of irrigation practices are applied, whose pros and cons, both in terms of water ...productivity and of their effects on the environment, are not completely understood yet. The continuous monitoring of irrigation and rainfall inputs, as well as of soil water dynamics, is a very important factor in the analysis of these practices. At the same time, however, it represents a challenging and costly task because of the complexity of the processes involved, of the difference in nature and magnitude of the driving variables and of the high variety of field conditions. In this paper, we present the prototype of an integrated, multisensor system for the continuous monitoring of water dynamics in rice fields under different irrigation regimes. The system consists of the following: (1) flow measurement devices for the monitoring of irrigation supply and tailwater drainage; (2) piezometers for groundwater level monitoring; (3) level gauges for monitoring the flooding depth; (4) multilevel tensiometers and moisture sensor clusters to monitor soil water status; (5) eddy covariance station for the estimation of evapotranspiration fluxes and (6) wireless transmission devices and software interface for data transfer, storage and control from remote computer. The system is modular and it is replicable in different field conditions. It was successfully applied over a 2-year period in three experimental plots in Northern Italy, each one with a different water management strategy. In the paper, we present information concerning the different instruments selected, their interconnections and their integration in a common remote control scheme. We also provide considerations and figures on the material and labour costs of the installation and management of the system.
Currently there are no small sensors that can be incorporated inside soil samples for laboratory testing, to monitor water transport during loading. This is an important limitation to a better ...understanding of the hydromechanical coupled behaviour of soils. A sol-gel relative humidity sensor (11 mm × 11 mm), microfabricated in a clean room environment, was conceived to be incorporated in soil specimens during standard laboratory tests. The sensor operates based on changes in electrical resistivity detected by a cerium-doped silica–titania film deposited using a sol-gel technique over interdigitated aluminium electrodes spaced at 300 μm. To the best of the authors’ knowledge, sol-gel sensors for relative humidity measurement have never been used in soils; therefore, this is a novel application. The water retention curve of compacted kaolin was measured with the sensors and compared with the curve found using water dewpoint potentiometer WP4-C. The sensors were also tested incorporated in an oedometer cell, in which load was applied under vapour equilibrium. It was possible to detect the increment of the degree of saturation during compression. The use of the developed sensors incorporated in soils is considered acceptable for suction ranges between 1 and 10 MPa, which extends the suction interval covered by tensiometers, normally operating up to 2 MPa. Although the sensors require improvements in terms of sol-gel deposition and calibration protocol, the results confirm their scientific potential for being used in testing and characterization of unsaturated soils.
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► The effect of cationic, anionic and nonionic conventional surfactants on the micellization properties of cationic Gemini pentanediyl-1,5-bis(dimethylcetylammonium bromide) is ...presented. ► The results show that experimental
cmc values of all the binary mixtures are less than the ideal
cmc. ► The interaction parameters determined from the Rubingh and Rosen equations are negative indicating synergism in both mixed micelle and monolayer formation.
The structure of Gemini surfactants makes them potentially useful candidates in terms of their performance, particularly in mixed micelles for different surfactant applications. We have studied mixed micellization and surface properties of binary mixtures of cationic Gemini pentanediyl-1,5-bis(dimethylcetylammonium bromide) (G5, 16-5-16) with conventional cationic cetylpyridinium chloride (CPC), anionic sodium bis(2ethylhexylsulfosuccinate) (AOT), and nonionic polyoxyethylene 10 cetyl ether (Brij 56) in detail by conductometric and tensiometric methods. The interfacial and bulk behaviors were investigated using theoretical models of Clint, Rubingh, Rosen, and Maeda to explain and compare the results of binary mixtures of G5 with the conventional surfactants. The synergism was observed in all the binary systems in the micelle as well as at the interface with expansion of molecular area per molecule. Greater synergistic interaction in the micelles has been found to reduce the solubilizing capacity towards polyaromatic hydrocarbons (PAHs).
Gelatin is a protein widely used in food, pharmaceutical and cosmetic products. Polypeptide structure of gelatin molecule facilitates its interactions with different surface active ingredients that ...are often present in such products. These interactions can significantly change properties of gelatin solution in the bulk, as well as on the interface, and therefore influence the stability of the system. In this study interactions between gelatin and different surface active molecules: two small molecule surfactants (Tween 80, Triton X100) and two surface active polymers: starch derivative (octenyl succinic starch, OSA) and cellulose derivative (hydroxypropylmethyl cellulose, HPMC), were investigated using tensiometric and viscosimetric measurements.
The results show that possibility and mechanisms of interaction between gelatin and surface active molecules depend not only on the nature of molecules, but also on its chemical structure. Thus, non-ionic, branched small molecule surfactant Tween 80 shows hydrophobic mechanism of interaction with gelatin, while other used linear small molecule surfactant, Triton X100, does not interact. Polymeric surfactant OSA starch is a weak anionic polyelectrolyte, but due to hidden polar group, shows hydrophobic interaction with gelatin, dependant on pH of the solution. HPMC molecule, which is non-ionic with small hydrophobic substituents, does not interact at all.
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► Interactions between gelatin and small nonionic surfactants are affected by molecular structure. ► OSA starch interact with gelatin by hydrophobic mechanism. ► HPMC molecules do not interact with gelatin.
The simplified evaporation method (SEM) is frequently used for the determination of the hydraulic conductivity function (HCF) of the unsaturated soil. Usually, the mass of soil samples during ...evaporation is often monitored to calculate the flux. However, the balance is sensitive to the external conditions, such as the tensiometers connected by the cables to transmit data, and the cable will have a disturbing effect on the balance. In this study, a series of laboratory tests were conducted to obtain the hydraulic conductivity function of six kinds of soils, which texture ranged from sand to silty clay by using the alternative simplified evaporation method (ASEM) that reduces the sensitivity of the external environment brought by the balance. The volumetric water content near the centre depth was monitored by the soil moisture sensor, and the change of flux during evaporation was calculated by the volumetric water content. At the same time, for comparison, the mass was monitored during the evaporation process, and the mass of evaporated water was used to calculate the flux (SEM). The HCF obtained by the ASEM was consistent with that obtained by the SEM.
Most studies in vadose zone hydrology use a single conceptual model for predictive inference and analysis. Focusing on the outcome of a single model is prone to statistical bias and underestimation ...of uncertainty. In this study, we combine multiobjective optimization and Bayesian model averaging (BMA) to generate forecast ensembles of soil hydraulic models. To illustrate our method, we use observed tensiometric pressure head data at three different depths in a layered vadose zone of volcanic origin in New Zealand. A set of seven different soil hydraulic models is calibrated using a multiobjective formulation with three different objective functions that each measure the mismatch between observed and predicted soil water pressure head at one specific depth. The Pareto solution space corresponding to these three objectives is estimated with AMALGAM and used to generate four different model ensembles. These ensembles are postprocessed with BMA and used for predictive analysis and uncertainty estimation. Our most important conclusions for the vadose zone under consideration are (1) the mean BMA forecast exhibits similar predictive capabilities as the best individual performing soil hydraulic model, (2) the size of the BMA uncertainty ranges increase with increasing depth and dryness in the soil profile, (3) the best performing ensemble corresponds to the compromise (or balanced) solution of the three-objective Pareto surface, and (4) the combined multiobjective optimization and BMA framework proposed in this paper is very useful to generate forecast ensembles of soil hydraulic models.
Interfacial properties like shear behaviour of commercial milk proteins and food emulsifiers were studied, at both air-water and
n-dodecane–water interfaces. Whey proteins form a protein network at ...interfaces. The film exhibits high elasticity, whatever the interface. On the contrary, micellar caseins and emulsifiers do not exhibit any viscoelastic behaviour at interfaces. Competitive adsorption of proteins with surfactants was clearly identified, both via rheological and tensiometrical measurements. The addition of an emulsifier to an elastic protein film, even at very small amounts, leads to a significant decrease of the interfacial elasticity, depending on the type of emulsifier and on the emulsifier/protein ratio. Water-soluble surfactants (like sucrose ester) are indeed more effective than oil-soluble surfactants in displacing protein molecules from our model interfaces. Most of our results on commercial samples do confirm but also extend what was already described in the literature with purified products. Our major contribution links these interfacial parameters to the stability of model foams. Foaming trials were performed by incorporating air in a sucrose syrup/water mixture, containing protein or emulsifier molecules (previously characterised) for stabilisation. In protein aerated systems, a high surface elasticity is required to prevent quick foam destabilisation: interfacial layers are quite deformable, their rupture and the bubbles' coalescence are limited. In the presence of low-molecular-weight surfactants, the formation and stabilisation mechanisms are quite different. Therefore mixed protein–surfactant systems offer a simple way for optimising foam ability and stability.
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