Construction and Geotechnics

The article is devoted to variant design of the prefabricated building structures of the power transmission line portal in a seismically hazardous area with a calculated seismicity is 8 points. Three basic versions of the foundation are considered: a monolithic foundation of concrete of class B15, a prefabricated foundation according to a standard solution according to the working documentation of the YUZHENERGOSETPROEKT and a two-layer foundation construction consisting of a monolithic pillow of class B15 and elements with a prismatic base of class B30. As a result of the simulation by PC ANSYS, using finite element method to determine the stress-strain state on the surface of the model elements. 10 variants of loads have been considered, several basic and one particular combination of forces. Maximum sediment and sediment difference (the second limit state), stresses in concrete and in working reinforcement meshes (the first limit state) were determined. It was found that the maximum sedimentation of the foundations of the considered options is not significantly different (within 3 %), the difference in sediment differs by 40 %. Stresses in concrete differ by 17 %, but even in the worst case, 41 % of the calculated compressive strength of concrete. For each of the options for a special combination of efforts, the cross section of the working armature was selected. In the models, two grids were installed along the bottom of the basement. It is established that for the considered models of foundations, the grids with the same step, but of different diameters, are optimal. The effect from the application of the model of a two-layer foundation with a prismatic base of class B30 is 49 % in terms of the area of the working reinforcement, which makes it possible to draw a conclusion on the efficiency of using a two-layer foundation for the construction of power line portals.

A preliminary geotechnical assessment of a site allows to make technical and economic analysis of the object of reconstruction or new construction. For the correct choice of the constructive solution of the structure underground part during geotechnical evaluation, it is necessary to know the existing bedding of soils at the construction site, soil physical and mechanical characteristics and the presence of anomalous inclusions (cavities, pipelines, other underground soil inclusions, etc.). This allow to perform the most correct feasibility study. Modern non-destructive techniques of wave analysis make it possible to quickly make velocity profiles of soil strata, with minimum labor costs, and evaluate soil physical and mechanical characteristics. One of these express techniques is Multichannel Analysis of Surface Waves (MASW). The article presents testing results by means of express method of multichannel analysis of surface waves at the sites of Perm and the Perm krai for dispersed and semi-rock soils. A comparative analysis of wave profiles with geological profiles obtained by engineering-geological surveys was carried out to assess the effectiveness of application of wave analysis for a site preliminary geotechnical assessment. In general, MASW allowed to determine the layers boundaries in the upper section with sufficient accuracy. Also an error of soil unit weight empirical formula given in foreign literature relative to the soil unit weight values determined under laboratory conditions is estimated. Divergence between different soil types was no more than 18 %. As a result, MASW with relatively low labor costs allowed to obtain a fairly reliable profile of the soil low velocity upper section.

This paper introduce results of survey of practice specialists in foundation engineering on frozen soils. The purposes of this research are getting data about frequency of use certain design decisions and determination of the most common causes of accidents of building foundations. The survey was designed in such a way that the analysis of the answers given to the questions presented in it contributed to the understanding of the current picture of the Russian practice of foundation engineering in areas characterized by spread of frozen soils. Presented questions were divided into thematic blocks. Distribution of construction projects by region and types of construction were fixed in first block. The ratio of objects by different parameters such as distribution of objects constructed according to the principle I and principle II of using frozen soils, type and material of foundation, type of piles for pile foundation and different ways of thermal stabilization of soils were evaluated in the second block. The ratio of general causes of occurrence the accident situations during exploitation of building foundations on frozen soils were needed to be evaluated in the third block. Used ways of struggle with the previously mentioned reasons were needed to be listed in the fourth block. The survey was conducted at the international scientific-practical conference "Modern technologies for the design and construction of foundations on frozen soils." The sample of respondents was formed randomly, regardless of age and gender. The criterion for the selection of respondents was the need to have experience in the design, construction and exploitation of foundations in areas with the spread of frozen soils. Thus, the survey conducted is fully consistent with the conditions of representativeness, and the data obtained can be easily approximated to the entire population.

Natural gases are a highly efficient energy source and a valuable chemical raw material, so they are now widely used for gas supply to cities and industrial enterprises. Natural gas has a number of advantages over other fuels and raw materials: non-toxic; lighter than air; has a high calorific value; extraction, transportation and use is easier than other fuels. In the middle of the last century began an active gasification of the cities of the Russian Federation. The article presents information from the history of gasification in Russia and Perm. The article presents an analysis of the level and volume of financing of gasification in Russia and Perm. Currently, the growth rate of gasification in the country is stable, but in many Federal districts the level of gasification is quite low. The condition of priority allocation of investments for gasification of the region is the absence of debts to pay for current gas supplies; repayment of debts of previous years; economic efficiency of the proposed facilities; loading of gas pipelines and gas distribution stations; readiness of consumers to receive gas. In addition, one of the problems of the gas industry in Russia is the deterioration of existing gas pipelines. Taking into account the service life of steel gas pipelines, it is now necessary to make decisions on their reconstruction and replacement. According to estimates of reliability of gas supply to consumers, the gas supply system of the right Bank of Perm is considered reliable. The gas supply system of the left Bank of Perm does not meet all the requirements of reliability due to the lack of communication of gas sources, as well as the need for repair work on gas distribution networks of high pressure.

One of the features for functioning of many industrial buildings is production or usage of oily liquids in the technological processes. These oily liquids such as vegetable or mineral oils and petroleum products can systematically fall onto the concrete and reinforced concrete structures and impregnate them. This leads to deterioration and changes in concrete’s and reinforced concrete’s physical and mechanical characteristics such as strength, material fatigue, endurance, deformability and some others. Despite the fact that many studies have already been carried out, the technical significance of the problem is extensive and still requires additional research. Influence of vegetable and mineral oils on the deformative properties of concrete has not been fully studied yet. The purpose of the research is to study the dependence of changes in the deformation of concrete and cement-sand mortar on the viscosity of the mineral oil (industrial oil I-30A) and vegetable oil (corn and olive oil). The currently available recommendations for the evaluation of these changes do not take into account the viscosity of oils and petroleum products. This holds out the possibility to solve the problems of assessing the reliability of the bearing concrete and reinforced concrete structures of industrial buildings where vegetable or mineral oils and petroleum products are produced or used. As a result of the research the influence of oily liquids with different viscosity on the deformative properties of concrete and cement-sand solution has been studied, and the laws of their changes have been established. Empirical mathematical models have been developed to predict deformations in concrete depending on the oil’s viscosity. The obtained results allow assessing the technical safety of the bearing concrete and reinforced concrete structures of industrial buildings in which vegetable or mineral oils are produced or used. The researches of physical and mechanical properties of concrete impregnated with oil are being continued.

The work is devoted to the feasibility study of the construction of motor roads with low traffic. The design solution proposed for comparison is a pavement design in which the role of a crushed stone base is played by an over compacted fine soil. In the Volgograd region, fine clay soils (sandy loam, loam) occupy a significant part of the area. In this regard, the feasibility study for the construction of agricultural roads with the use of repacked soils of this type in the construction is of extremely important socio-economic importance. The proposed method of technical and economic assessment is based on the determination of the actual strength resource of road structures based on the prediction of changes in the longitudinal evenness of the coatings. The prediction methodology is based on the improvement of the well-known linear multifactor model that predicts a change in the International Roughness Index (IRI), depending on the intensity of movement and the initial state of coverage, by including additional factors. As factors, it is proposed to use data on the qualitative composition of the traffic flow, namely, the level of impact of heavy goods vehicles, the level of weather and climate influences on the surface, as well as the level of road maintenance. As a data processing tool, a multivariate linear regression analysis is proposed implemented in Excel. Based on the results of calculations based on diagnostic data from an experimental section of the road of the proposed construction in the Bykovsky district of the Volgograd region, the authors concluded that the proposed design solution was technically and economically feasible.