The water pumped by reclamation stations of the Republic of Uzbekistan contains many mechanical impurities. This negatively affects the operation of pumping units. There is a decrease in the operating parameters of the pumping unit and the associated increase in electricity consumption. Analysis of the alluvial regime of the main water sources of large pumping stations shows that the sediment concentration can reach values of 15-20 kg/m3 and, on average, up to 8-10 kg/m3 (i.e., exceed the permissible values according to the technical requirements for centrifugal pumps by 2-3 times). Based on the consideration of a two-phase liquid model (pure water and mechanical impurities) and formulas for determining the useful power, a dependence is derived to determine the magnitude of the increase in power consumption. According to this dependence, a graph of the dependence of the increase in the value of the required useful power depending on the concentration of mechanical impurities in the pumped water is constructed, which can be applied in practice during the operation of irrigation pumping stations. The results of a quantitative analysis of the influence of the content of mechanical impurities in the pumped water on the value of the pump's useful power showed that with average turbidity of the pumped water of 10 kg/m3, the overspending of electricity would be 1.75%. This is of great practical importance for the machine water lifting of the Republic of Uzbekistan (the main consumer of electricity in the agricultural sector), and the results can be used to develop an energy-saving strategy in the field of operation of irrigation pumping stations.
It is shown that during operation reinforced concrete structures are very often susceptible to cracking, which leads to a deterioration in the quality and expected life of them. The traditional methods of restoration and strengthening of structures are methods of building up, impregnating the structure of concrete with polymer and other materials, applying monolithic coatings or gluing metal polymer and other elements. Known repair methods are characterized by high complexity of execution, high cost, etc. It is shown that there is a pressing economic incentive for the development of concrete capable of self-repairing and repairing damage. Recently, tendencies toward the creation of new materials that are capable of actively interacting with external factors have been outlined towards world practice; such materials have received the name “intellectual”. The use of «intelligent» materials allows you to monitor and predict the state of various structures and structures, at the required time and even in hard-to-reach areas, significantly increase the resource of engineering systems and their reliability. It has been shown that to date, various chemical methods have been developed for creating self-healing concrete. One of the breakthrough technologies in the field of obtaining effective materials and structures based on them are biotechnologies based on the use of microorganisms. Many researchers have studied the use of calcite produced by bacteria to increase the life of concrete-based structures and restore buildings by eliminating cracks, increasing the strength of concrete, reducing permeability, and reducing water absorption. The article provides an overview of the work of foreign specialists in these areas.
Reinforced concrete as one of the main materials for a wide class of building structures for civil, industrial and transport purposes has a number of specific properties: physical nonlinearity, anisotropy, and crack formation. The behavior of reinforced concrete in the elastoplastic stage before its destruction is more characterized by deformation of concrete. It is shown that the physical nonlinearity of concrete is due to plastic deformations, which are characteristic of various types of stress state. For a triaxial stress state, the system of equations in the mechanics of a deformable solid, it includes two groups of formulas that combine nine equations that include 15 unknowns (three displacements, six strain components, and six stress components). In order for the system to be closed, it is necessary to supplement it with six equations. Such equations are the basic physical relationships that relate the six stress components to the six strain components. The use of linear relationships between stresses and strains introduces the greatest error in the assessment of the stress-strain state (NDS) of structures made of materials with the properties of nonlinearly deformable bodies. In this regard, the more correctly the physical law defining the correlation reflects the material, according to which the material resists various types of deformations, the less error will be allowed in the assessment of the NDS of structures. The article proposes a new approach to the construction of basic physical relationships based on an invariant solution to the problems of mechanics of a deformable solid for concrete in a plane stress state. The correspondence of the proposed dependences to the real stress and deformable state of the material is shown.
A mathematical model of the problem of viscoelastic isotropic plate vibrations based on the Kirchhoff-Love hypothesis in a geometrically nonlinear formulation was presented. The mathematical model was built without considering the tangential forces of inertia. To describe the viscoelastic properties of the plate material, a weakly singular Koltunov-Rzhanitsyn kernel with three different rheological parameters was chosen. To solve the problem of parametric vibrations of a viscoelastic plate with a weakly singular relaxation kernel, a numerical method based on the use of quadrature formulas was applied. A discrete model of this problem was first constructed using the Bubnov-Galerkin method; i.e., a system of integro-differential equations with variable coefficients was obtained, and then, using a numerical method based on the elimination of a singularity of the kernel, the problem of parametric vibrations of viscoelastic rectangular plates was solved. The influence of the viscoelastic properties of the material and the variability of the plate thickness on the oscillatory process was shown.
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