## Vol 13, No 1 (2022)

**Year:**2022**Articles:**8**URL:**https://ered.pstu.ru/index.php/CG/issue/view/155**DOI:**https://doi.org/10.15593/cg.v13i1

Settlement and long-term bearing capacity of the pile taking into account the rheological properties of soils

#### Abstract

A large number of scientific works by both Russian and foreign authors are devoted to the interaction of a single pile with the surrounding and underlying soils. Based on experimental, numerical and theoretical studies, various methods, approaches and solutions have been obtained in scientific works, which make it possible to most correctly predict the settlement and bearing capacity of a single pile. Research in this area is relevant, since the determination of the settlement of the pile, as well as the study of the mechanism of distribution of the load transmitted to it, play an important role in the design of pile foundations. In this work, the boundary value problem of the interaction of a long and incompressible pile with the surrounding and underlying soils in an elastic-viscous formulation, taking into account soil strengthening, was solved, based on the Maxwell model, as well as on the basis of the rheological model of A.Z. Ter-Martirosyan. This study presents a detailed course of solving the boundary value problem, as well as the basic formulas for calculating the settlement and long-term bearing capacity of a single pile. The change in the curve of dependence σ R ( t ) at different values of soil viscosity is shown when solving the problem in an elastic-viscous formulation. An additional graph of σ R ( t ) dependence is presented showing the difference in the presented soil models. Based on the plotted graphs of the dependence of σ R ( t ) when solving the problem in an elastic-viscous formulation, it can be concluded that the time to reach the maximum value of the load under the foot of the pile is directly proportional to the value of the soil viscosity. When solving the problem on the basis of the rheological model A.Z. Ter-Martirosyan, the maximum value of the load under the foot of the pile is reached earlier than when solving the problem in an elastic-viscous formulation both with and without soil strengthening, which requires additional study.

**Construction and Geotechnics**. 2022;13(1):5-15

THE STRENGTH OF UNDERGROUND HORIZONTAL WORKINGS OF ELLIPTICAL CROSS-SECTION SHAPE SUBJECTED TO ALL-ROUND UNIFORM PRESSURE

#### Abstract

The paper presents the results of a study to determine the stress state on the contours of underground workings, the cross-section of which has the form of an ellipse with a fixed value of the large semi-axis. For workings of this type, at different values of the ellipse parameter, the permissible depths of laying and the values of uniform pressure at the points of their contours are determined, at which normal tangential stresses do not exceed the tensile and compressive strength limits of the host rock. Based on the strength condition used in the work, the values of the permissible depths of the workings are calculated for varying values of uniform pressure applied at the points of the workings contours and the specified values of the lateral expansion coefficient of the rock. The permissible values of the stretching uniform pressure at the points of the contours of the elliptical shape of the cross-section with a change in the depth of laying, the specified values of the lateral expansion coefficient of the rock and the ellipse parameter are given. In addition, the paper presents formulas on the basis of which the problem of stress distribution at the points of contours whose cross-section has the shape of an ellipse with a fixed value of the large semi-axis is considered. It is established that when the intensity of the stretching uniform pressure applied at the points of the contours of the workings of an elliptical cross-section shape changes, and the specified values of the ellipse parameter, the depth of the workings and the magnitude of the lateral expansion coefficient of the host rock, sections of the contours on which tensile and compressive stresses act are highlighted. When changing the depths of the workings of the elliptical cross-section shape, sections of contours are identified on which tensile and compressive stresses act at given values of the ellipse parameter, the intensity of the stretching uniform pressure applied to the points of the contours, and the values of the lateral expansion coefficient of the rock.

**Construction and Geotechnics**. 2022;13(1):16-33

DEVELOPMENT OF INNOVATIVE PILE FOUNDATION DESIGNS ON SUBSIDENCE SOILS

#### Abstract

New technical solutions for the elimination of negative friction forces in the construction of pile foundations on subsidence soils are considered. The friction forces arising between the subsidence soil and the side surface of the pile, according to the Amonton-Coulomb law and the theoretical justifications of B.V. Deryagin, are presented as the sum of a term depending on adhesion and the product of the coefficient of friction by normal pressure. There is some function approximating the total friction force along the side surface of the pile. Differentiating this function, we obtain a formula that determines the change in soil pressure on the side surface of the pile, which varies with the depth of the pile location in the subsidence soil. To sharply reduce the forces of negative friction, the author has developed the design of a pile foundation made of asbestos cement pipes. Studies have shown that in these piles, the forces of negative friction are reduced by 20-30 %, compared with concrete piles manufactured in factory conditions. The author has developed two variants of the method of building a pile foundation on subsident soils, in which the role of antifriction lubricant is performed by a layer of humbrine. Humbrin is a waste of the technology of purification of technical oils. This waste accumulates in large quantities in the landfills of oil refineries. The author has proposed a new design of a pile foundation, in which recycled tires are used as an outer shell to remove the forces of negative friction. Experimental studies have shown that even with vertical deformations of the tire screen of more than 0.04 m, the amount of pile precipitation turned out to be negligible, only 0.02 mm. The author also developed a pile foundation erected on subsident soils. This pile foundation has an external cylindrical shell. In the gap between the cylindrical shell and the side surface of the pile there is a spiral-wound elastic rubber rolling harness. When the surrounding soil subsides, the outer cylindrical shell moves vertically down the rolling spiral bundle, removing negative friction from the side surface of the pile. In addition, the rolling spiral elastic harness also performs the function of a seismic isolator.

**Construction and Geotechnics**. 2022;13(1):34-43

Assessment of seismic resistance of multi-storey buildings under seismic impacts on weak subsidence soils

#### Abstract

Under the influence of dynamic and static loads, the volumes of weak soils in the base change due to a decrease in porosity. In this regard, studies of the stability of the building under seismic influences, the bases of which are elastic-plastic layers, have been carried out. As a result of the research carried out in this paper, an equation of ground motion was obtained to determine the general angle of inclination of the building, taking into account the seismic impact characteristic of the construction site and the characteristics of the building itself. An increase in the risk due to the loss of stability of the base due to the possible slope of the building is shown. The mechanism of soil weakening, which leads to the overturning of buildings, is analyzed and justified. The parameters affecting the kinematic characteristics of buildings and structures are shown. It is determined that an elastic system consisting of a building and a base has one-way connections between the foundation and the base, which are removed under the influence of seismic forces in certain areas of the foundation sole, where the static load is insignificant. Removing the links causes a change in the rigidity of the system. The center of gravity and the center of mass are shifted by a certain distance, therefore, there are changing fluctuations. The range of vibrations in this case depends on the ratio of the natural frequencies of buildings and seismic waves. It is known that when a building under the influence of external forces receives a certain slope relative to the vertical axis, then there is a decrease in the load, a dependence is obtained to determine the load reduction coefficient. The paper considers a practical solution to the problem of stability on the example of a 50-meter building. Based on the general principles of earthquake-resistant construction in the calculation of overturning, several calculations of buildings were carried out using the initial data for frequent and weak impacts, moderate strength and rare strong impacts. The results of the research can be applied to the calculations of multi-storey and high-rise buildings built on weak deformable soils, along with other calculations that allow increasing seismic resistance.

**Construction and Geotechnics**. 2022;13(1):44-57

DETERMINATION OF THE VALUE OF THE STABILITY MARGIN COEFFICIENT BASED ON THE ANALYSIS OF THE STRESSED STATE OF THE SOIL MASS IN THE FRAMEWORK OF THE LINEAR THEORY OF ELASTICITY

#### Abstract

The introduction lists the main disadvantages of the traditionally used methods for calculating the stability of slopes and slopes and presents a calculation method in which, for the first time, in our opinion, an attempt was made to construct the most dangerous "slip line" based on the analysis of the stressed state of the soil massif. Further, in the first chapter of the article, three possible approaches to solving the problem of determining the angle of inclination of the most probable shear site at the studied point of the soil massif, based on the analysis of its stress state, are presented and analyzed. The second chapter presents the results of calculating the value of the coefficient of stability of the soil slope by L.G. Fisenko (one of the traditional calculation methods) for two types of sliding line: circular cylindrical (classical case) and constructed by the method of N.S. Nikitin taking into account the operating stresses; and by V.K. Tsvetkov - A.N. Bogomolov. All calculations are performed for one object, the geometric parameters of which and the numerical values of the physico-mechanical properties of the composing soil are given in the article cited below by S.N. Nikitin. As a result, it turned out that the first two coefficients of the margin of stability are respectively equal to K 1 = 1.6 and K 2 = 1.75, and the value of the third coefficient of the margin is equal to K 3 = 2.18. Comparing this value with the values of the coefficients of the margin of stability calculated by the method of S.N. Nikitin and the method of L.G. Fisenko, we see that it is 26 and 20 % higher, respectively, while K 2 > K 1 is 9.4 %. Based on the analysis of the calculation results for the example considered in this paper, it can be stated that methods based on the analysis of the stressed state of the soil mass give higher values of the stability margin coefficients than traditionally used. Thus, the value of the slope stability margin coefficient calculated by the method of V.K. Tsvetkov - A.N. Bogomolov turned out to be equal to K 3 = 2.18. Comparing this value with the values of the stability margin coefficients calculated by the method of S.N. Nikitin and the method of L.G. Fisenko, which are respectively equal to K 1 = 1.75 and K 2 = 1.6, we see that it is 20 and 26 % more than them, respectively. At the same time, K 1 > K 2 by 9.4 % - this indicates that taking into account the stresses during the construction of the sliding line makes its shape different from the circular cylindrical one, which affects the value of the stability margin coefficient.

**Construction and Geotechnics**. 2022;13(1):58-72

THE USE OF METHANOGENIC PLANTS BASED ON SOLID COMMUNAL WASTE IN LOW-RISE CONSTRUCTION

#### Abstract

The authors consider the main aspects of local utilization of waste of low-rise buildings by methane fermentation with the subsequent production of secondary energy resources. Currently, the generation of methane in artificial conditions is an intensively developing industry. Previously, the authors studied the experience of the regions of Russia in the disposal of solid domestic waste. It is revealed that the processing of solid municipal waste in bioreactors can be carried out with the joint fermentation of various wastes. This is also possible by adding existing accelerators for the methane fermentation reaction. The quantitative characteristics of waste generated on the territory of individual residential low-rise buildings have been studied. From the total volume to be disposed of, waste potentially suitable for the formation of the initial substrate was isolated. The main properties of raw materials for the necessary generation of bio methane have been determined. The specific methane yield during its constant generation has been calculated for various combinations of municipal waste of low-rise buildings. The paper presents a general concept of local processing of municipal solid waste and describes the scheme of the methane generating plant. The dimensions and technical characteristics of the installation for obtaining bio methane from waste at the place of their formation in residential buildings have been determined. In addition, the calculation of thermal energy produced on the base on generated methane was carried out. And it was found that the introduction of methane-generating plants in the technical systems of low-rise buildings allows to increase their energy efficiency, reduce the load on existing landfills of solid domestic waste and achieve maximum utilization of waste from residential areas.

**Construction and Geotechnics**. 2022;13(1):73-81

THE USE OF METALLURGICAL CALCIUM, ALUMINUM AND IRON-CONTAINING SLAGS IN THE PRODUCTION OF HEAT-RESISTANT CONCRETE BASED ON ORTHOPHOSPHORIC ACID

#### Abstract

The objects of research are: ferropyl from self-disintegrating slags of low-carbon ferrochrome, slag from smelting without carbon ferrochrome, ferrite-calcium slag and heat-resistant concrete. Due to the fact that the Russian budget does not provide funding for geological exploration and other survey work to determine the quantity and quality of raw materials for the production of construction products, it is necessary to conduct research on the use of technogenic raw materials as raw materials. The use of technogenic raw materials in the production of construction materials practically reduces many costs not only for geological exploration, but also for the arrangement, including the operation of quarries, to zero. Metallurgical industries (non-ferrous and ferrous) in Russia emit a third of all available emissions from industrial enterprises into the atmosphere, while the volume of metallurgy products (non-ferrous and ferrous) is only 17 % of the total domestic industry. In this work, metallurgical waste was used for the production of heat-resistant concrete: as a calcium-containing component, ferropyl from self-disintegrating slags of low-carbon ferrochrome, as an iron-containing component, ferrite-calcium slag, waste from the processing of copper-zinc concentrates, which is a light yellow material slowly cooled to complete scattering, resembling fine sand, and as an aluminum-containing slag from smelting without carbon ferrochrome. Studies have shown that ferrite-calcium slag contains ferrous iron oxide (fayalite) reacts quickly with Н2РO4 and heats the mixture to the required temperature for the appearance of astringent properties. Studies have shown that thanks to the use of orthophosphoric acid as a binder, it is possible to dispose of up to 85 % of non-ferrous metallurgy waste and at the same time obtain heat-resistant concretes with high physical and mechanical properties.

**Construction and Geotechnics**. 2022;13(1):82-95

Comparative experiment to determine the waterproofness of concrete by "wet spot" and "breathability" methods

#### Abstract

Comparative tests of control samples of concrete for water resistance by the direct method of "wet spot" and the method of "air permeability" were carried out. Tests of 6 series of control samples showed that 60 % of the results obtained by the two methods differ by 0.2 MPa (one brand of water resistance W), which is unacceptable. The range of results for the direct "wet spot" method was 0.6 MPa (four waterproof grade W), more than for the "air permeability" method 0.4 MPa (three grade W). Probably, this is due to the imperfection of test methods, with an insufficient level or lack of metrological confirmation of equipment for determining water resistance, and more. In production practice, this situation means that the test results obtained are not provided with confidence, and as a result, under these conditions, it is possible to produce products (concrete) that do not meet regulatory requirements.

**Construction and Geotechnics**. 2022;13(1):96-105