Construction and Geotechnics

An effective way to strengthen shallow foundations is contour reinforcement - the execution of vertical elements in the soil base along the edges of the foundation. The introduction of reinforcement elements that perform the function of a "compression wall" leads to a noticeable decrease in deformations and an increase in the bearing capacity of the soil at the base of the reinforced foundations. As reinforcing elements, various structures and materials with strength properties that exceed the corresponding properties of the soil can be used. A positively recommended method for the formation of reinforcement elements is group high-pressure injection. The essence of the method lies in the simultaneous supply of a cement-sand mortar through several sources installed in a row, under pressure exceeding the structural strength of the soil and the subsequent creation of flat vertical injection bodies of conditionally rectangular shape in the soil. An important issue in contour reinforcement is the determination of the optimal injection parameters - the number and spacing of injection bodies in plan and in depth, which can lead to a significant reduction in cost of work. To determine the rational parameters of the contour reinforcement with injection bodies, a set of numerical experiments was performed to calculate the stress-strain state of the soil foundation for different reinforcement schemes in the MIDAS GTS NX 2019 software package. The calculations were carried out in a 3D formulation, taking into account the nonlinear nature of the soil operation. Based on the results of the calculation, the most effective schemes for the location of reinforcement elements were determined when strengthening shallow foundations with contour reinforcement with injection bodies, and the technology for consistent reinforcement work with a gradual increase in the number of reinforcement elements was substantiated.

The object of the study is a ceramic sample taken from the wall of a distillery built in 1896 in the village of Rozhdestveno, Samara region, with an age of more than 120 years. Studies have shown that the sample under study contains an increased amount of carbon (C = 9.48). Obviously, this is due to the fact that low-melting clay with a high organic content was used as a binder (clay raw material), or a burn-out additive was introduced into the karmic mass, for example finely ground coal (no more than 1 mm in size). The burnout additive not only increases the porosity of the products, but also promotes firing inside the material and uniform sintering of ceramics. It was found that the increased content of alkali oxides in the ceramic sample (R2O > 3.5 %) contributes to the formation of a liquid phase in the temperature range of 950-1000 oC, which flows into small pores, and thereby reduces the porosity of the product. It was revealed that three types of pores are mostly found in ceramic bricks: slit-shaped, isometric and oval-shaped pores, in the studied sample the pores are mainly oval (rounded) in shape. Integral and differential porograms of the studied samples obtained by mercury porometry showed that the total volume of micropores ranging in size from 10-4 to 10-8 m is 0.157 cm3/g. The differential distribution of micropores, depending on their size, is as follows, %: 10-4 - 10-5 m - 27; 10-5 - 10-6 m - 24; 10-6 - 10-7 m - 24; 10-7-10-8 m - 25. Dangerous pores in ceramic materials are capillary pores with a size of 10-6 - 10-7 m. The content of "dangerous" micropores in the studied sample is 24 %, and the content of such "dangerous" pores in wall ceramics is in the range of 40-60 %.

Removing icicles from the roofs of buildings is a major problem for most cities. The paper provides an overview of a large number of patented methods and devices for combating icicles and ice on the eaves of roofs. However, there are very few really manufactured and tested products. The aim of the work was to test experimental samples of anti-icing cornices using solar radiation energy in artificially created conditions. For thermophysical experiments, more than 30 models of cornices were made from different materials with different paint coatings. During the experiments, it was found that the black color RAL 9005 has the greatest absorption capacity, and the gray graphite RAL 7074 is very close to it. The blue RAL 5005 and green RAL 6029 have a lower absorption capacity. The red RAL 3000 has a noticeably lower absorption capacity than blue and green. The least heated in the sun was the white RAL 9003 cornice model and galvanized steel. The dependence of the absorption capacity of cornices on the degree of their roughness and the method of applying the paint coating is not revealed. Due to the energy of solar radiation, anti-icing cornices can have a temperature 40-45 °C above the ambient temperature. Even in the shade, the temperature of the black cornices exceeds the ambient temperature by 4-5 °C. The wind blowing at an average speed of 2.5 m/s reduces the temperature difference between the experimental cornices and the air in the shade by about 2 times. The presence of a stretch film on the part of the cornice that will be placed under the roof allows you to reduce heat loss by one and a half to two times.

The formula for normal tangential stresses for single underground workings of different cross-sectional shapes, located at a given depth, with all-round tensile uniform pressure applied at the points of the contours of the workings, is derived. As a mapping function is considered a function of complex variable, which is a polynomial of natural degree n with a pole of first order in zero, allowing the construction of various families of simple closed curves, simulating configurations of the contours of underground workings. Examples are given of contours whose cross-section has the form of a straight and inverse trapezoid, triangle, vaults with vertical and sloping walls, rhombus, rectangle, square and ellipse. Based on the method proposed by the author, the coefficients of the polynomial of the seventh degree, which performs conformal mapping of the interior of a unit circle on a plane with a trapezoidal hole of a given dimensions, are calculated. The stress state of constructed workings at the points of its contour at different depths of laying, the values of the all-round tensile uniform pressure at two fixed values of the lateral expansion coefficient of the rock is investigated. The graphical representations of the stress acting on the contour of the working in question are given. The obtained results can be used to solve problems of determining the permissible depths of mine workings and calculating the values of permissible values of uniform pressure in the points of their contours. The criterion for determining the values of these values is the condition of absence of points on the contours of workings, in which the normal tangential stresses exceeding the limits of tensile and compressive strength of the host rock.

The problem of the beneficial use of large-tonnage industrial waste is acute all over the world. The metallurgical industry is no exception. One of the actual areas of application of such slags is the construction industry. Often, slags have many impurities that adversely affect the quality of the materials from which they can be made. However, in a small amount they can be used as pigment dyes, which make it possible to obtain materials of an unusual color. Decorative concretes differ from ordinary "gray" concretes in that they give architectural expressiveness to products, primarily for finishing works (walls, floors). The selection of the composition of such concrete requires a thorough study of both the raw materials themselves, including slags, and the selected compositions based on them. The article presents studies of finely ground slag from gas cleaning of metallurgical production, including physical and chemical methods. The analysis of the influence of the multicomponent composition of metallurgical slag on the structure and properties of the future composition of concrete is given. It was revealed that almost all components of the slag do not have a positive effect on the hydraulic or pozzolanic activity of the binder during the formation of the structure of the cement stone. More than half of the constituent minerals of the slag contains iron-containing compounds, giving the slag a rich brown color. The slag has a slight plasticizing effect. The slag particles contribute to the release of water retained by the cement particles, and, hence, to an increase in the total specific surface area of the cement particles. This structure hydrates the cement gel faster, resulting in faster hydration and strength development. Therefore, it is advisable to use the studied slag as a finely ground pigment additive in the selection of binder and concrete compositions. The finely ground structure of the slag makes it possible to improve the capillary-porous structure of concrete, reduce the consumption of cement by 5-15 %, while obtaining concrete in terms of compressive strength of a class of at least B30. The compositions of the decorative binder were selected using slag and fine-grained decorative concrete based on it for decorative flooring. The best concrete composition has strength class B40 for rooms with high impact intensity.