Seepage losses from trapezoidal earth canals with an impervious layer under the bed

Seepage of irrigation water from earth canals is one of the most significant causes of water loss. It should be carefully studied and controlled. This research aims to study the effect of the presence of an impervious layer under the bed of trapezoidal earth canals on the amount of seepage discharge. The finite element numerical model SEEP2D is used in the study. Different scenarios for the canal's dimensions and side slopes are considered. Various values for the vertical distance between the canal's bed and the impervious layer are also studied. The numerical model's results are verified using Vedernikov's equations. The results show that the presence of an impervious layer can reduce the amount of seepage discharge by up to 82.7% compared to that calculated without it, depending on the depth of the pervious layer, the ratio between canal's bed width to water depth, and the side slopes. It is recommended to have boreholes at canal construction sites in order to investigate if an impervious layer exists under the canal's bed. This helps to estimate the correct amount of seepage discharge based on the vertical distance from the canal's bed to the impervious layer under it. Design charts are also provided.

Making cotton face masks extra-protective by use of impervious cloth as the front layer to restrict flow of aerosols and droplets

Introduction: One of the important measures to prevent spread of COVID-19 in community is use of face mask. Though the debate is going on regarding the airborne transmission of SARS-CoV-2 it makes reasonable point for universal use of face masks. A large variety of face masks are available in the market or people can make their own using household items. The efficacy of masks depends upon the type of cloth and number of layers of the cloth. Material and methods: We have created an innovative mask with two layers of cotton and an impervious layer. The impervious layer made from polypropylene coated with polyurethane was applied on the outer side in the middle half of the mask in front of mouth and nose. The efficacy of this test mask was measured against N95FFR (reference standard), triple layer surgical masks and single layer cotton mask. A manikin was used wearing these masks/respirator and aerosols/droplets of diluted red colored carbol fuchsin and fluorescent Auramine O were sprayed from distance of 1m and 2m. We also tested use of face shield. Both macroscopic and microscopic examination of the dissected masks and respirator was performed. Results: The N95FFR was able to block the aerosols/droplets by its front layer. One triple layer surgical mask showed microscopic presence of stain in its innermost layer while the other blocked it with middle layer. The single layer cotton mask was not able to protect as we observed stain on the face itself. The test mask blocked most of the stain on impervious layer and also on the front cotton layer on lateral sides, where impervious layer was absent. When fluorescent stain was used, ultraviolet examination demonstrated that the whole area covered by test mask was clean while the other non covered area was fluorescent. Conclusion: We believe that our innovation can be used in the community as well as in general areas of the hospital like, offices, labs, etc. and can be a better alternative to single use triple layer surgical masks. Further testing may be done by other organizations to rule out bias in our study.

Collaboration solves long standing corrosion problem

External pitting corrosion has been a long standing issue for stainless steel pressure equipment systems on Woodside offshore facilities. Experience has shown that this pitting cannot be effectively managed by inspection and, as a result, the current policy is that piping replacement should be planned once the presence of significant pitting corrosion has been identified. All Woodside offshore facilities have 316-grade stainless steel pressure equipment which is experiencing active external corrosion pitting to varying degrees. This represents the potential for hundreds of millions of dollars in piping replacement across the company. STOPAQ is an established product for the mitigation of external corrosion in carbon steel equipment however, it has not previously been used at Woodside on stainless steel equipment to address pitting corrosion. Through collaboration with the Woodside Future Laboratory at Monash University, Materials and Corrosion Engineering, Woodside Energy Limited has challenged the old established theory regarding the mechanism of pitting in stainless steel and a test program has been devised to validate the new way of thinking, which postulates that elimination of moisture and oxygen from the pits, by the application of an impervious layer like STOPAQ, will stifle the corrosion reaction and arrest the pitting. A recently completed test program at Monash which utilised computed tomography (CT) scanning, to very accurately determine the volume of corrosion pits, has confirmed that the application of STOPAQ to pitted stainless steel is very effective at mitigating this type of corrosion.

Blistering Mechanism Analysis of Hydraulic Asphalt Concrete Facing

Two years after the Zhanghewan Pumped-Storage Power Station was put into operation, more than 500 blisters appeared in the asphalt concrete facing of the upper reservoir, and nearly half of them ruptured at the surface. The blistering mechanism of the asphalt concrete facing was studied in this paper. Through on-site inspection and coring inspection, it was found that the blistering was caused by the vapor pressure formed by the water enclosed in the middle of the impervious layer during high temperatures. Numerical analysis showed that the temperature 5 cm below the surface could reach 50–60 °C. Through numerical analysis and model tests, the internal water at this temperature may form a vapor pressure of 20 kPa. Finally, the blister size of the asphalt concrete facing at this temperature and pressure was studied with a model test. The possible sources of moisture inside the impervious layer were also analyzed through a core test, which found that moisture was most likely to be introduced by water spraying during rolling.

Oxidation Behavior of Silicides

The oxidation behavior of Mo, Nb, and Ti-silicides has received significant attention in past few decades for their potential to be used as high temperature structural materials. These Si-bearing intermetallic alloys have the ability to form an oxide scale containing SiO2, which is protective if formed as a continuous and impervious layer, so that the ingress of oxygen from atmosphere to the underneath alloy is restricted. To form a continuous and stable SiO2scale, it is important to have sufficient activity of Si along with thermodynamic and kinetic conditions favoring its growth in comparison to that of oxides of other alloying elements. MoSi2has superior oxidation resistance compared to that of Mo3Si or Mo5Si3, because of its higher Si content. Furthermore, a continuous film of SiO2is able to form at temperatures in the range of 800-1700oC on MoSi2due to vaporization of MoO3, but not on NbSi2or TiSi2due to competitive growth of Nb2O5or TiO2, respectively. During past two decades, a significant effort has been devoted to development of Mo-Si-B alloys containing Mo-rich solid solution, Mo3Si and Mo5SiB2as constituent phases, due to their ability to form a protective borosilicate scale. The presence of B2O3contributes to fluidity of borosilicate scale, thereby contributing to closure of porosities. Efforts have been also made to develop multicomponent Nb-silicide based alloys with optimum combination of mechanical properties and high temperature oxidation resistance with limited success. There have been efforts to develop silicide based coatings for protection oxidation for Mo-rich Mo-Si-B alloys and Nb-Si based ternary or multicomponent alloys with inadequate oxidation resistance. Oxidation behavior of selected silicides with potential for structural application, along with mechanisms for protection against oxidation has been reviewed and discussed.

Efficient concrete increased water resistance modified with mineral and polymeric additives

The article deals with issues of optimizing the composition of efficient concrete increased water resistance, reducing its cost without losing or increasing its basic properties. In recent years, the most effective method of tightness to water in the construction of buried and underground structures, as opposed to the use of bituminous and other traditional materials, is a method based on the use of concrete with increased water resistance. This type of tightness to water is called “White bath” in Europe. The essence of the technology is that the role of the impervious layer is performed directly by the concrete itself. The subject of the study is the composition of self-stressing concrete, which has a high density and fastness to water, but a high price compared to the concrete on Portland cement, which limits its wide application. The aim of the study is the development and optimization of the composition or stressing concrete with desired properties using a variety of mineral and polymeric additives to reduce the cost of the finished product while maintaining or improving the significant operational indicators.