Construction and Geotechnics

It is known that as a result of the device of underground workings on the earth's surface the bowl-shaped hollow caused by movement of soil in the developed country is formed. The cross section of this hollow, carried out in the normal direction with respect to the extension of the production, has a saddle shape. This fact is confirmed by numerous results of theoretical researches and field observations. The article presents an analytical solution to the problem of stress distribution in a homogeneous isotropic soil mass with asymptotically damped movement on the part of its boundary. The resulting solution can be used to determine the stresses arising in the soil mass due to its subsurface mining. Methods of the theory of functions of complex variable (Kolosov-Muskhelishvili methods) were used to construct the analytical solution. Expressions for stress and strain components, depending on the Poisson ratio, are determined based on the solution of the second basic boundary value problem of the plane theory of half-plane, which is very important, because of the sufficiently large difference in the numerical values of this characteristic for different types of rock soils. Graphic images of stress contours are presented. To build the painting from lines of voltages used mathematical shell Maple. Particular cases of the above solutions are the solutions of the problems of the stress-strain state of elastic half-plane with uniform and linear displacements of the boundary of the half-plane. By summing up the stress and strain components given in the article, it is possible to obtain a solution of a similar problem in the asymptotic tendency of displacement to a certain constant value (equal-dimensional displacement).

In the article the problem of ensuring the stability of buildings and construction on slopes. Incorrect assessment of slope stability can lead to an emergency situation, which in dense housing can affect existing buildings that were previously in a stable state. At the present time for stability prediction the slope stability is widely used finite element method, implemented in a variety of software systems. The aim of the study was to select the optimal solution for ensuring the stability of a slope composed of claystones. The authors solved the following tasks: review of questions to ensure slope stability is completed; the patent search is carried out and results are analyzed; the analysis of archive data of reports on the investigated object is made; the initial data for calculations and numerical simulation in the Plaxis 2D software package were determined; factors that significantly influenced the formation of an emergency situation at the research object are identified based on the results of the first series of numerical experiments; the optimal technology for slope stability is selected based on the results of the second series of numerical experiments. Claystones of the Early Permian age take part in the geological structure of the territory of Perm city, the bearing capacity of which decreases with water saturation. This can lead to loss of stability of the slope, composed of argillite-like clays, which was confirmed by the results of the first series of numerical experiments. As a result of the second series of numerical experiments, the most rational of the methods considered to ensure the stability of the slope was a method using two rows of soil-cement piles located in different parts of the slope.

Valve-type water fittings, equipped with the flat locking element, work practically without water leaks under operating conditions. A locking element with an orifice-shaped opening in the form of a «curved drop» was designed to improve the regulating capacity of the valve. The results of the studies of the hydraulic characteristics of liquid outflow through the orifices of various shapes carried out by the methods of mathematical simulation and physical experiment were presented in scientific publications by Russian and foreign specialists. Patterns of liquid outflow through the orifice in the form of «curved drop» have not been fully investigated. It constrains the task of designing of the valve-type water fittings with high regulating capacity. A mathematical model has been developed that includes a description of the orifice-shaped opening in the form of a «curved drop» and generates a numerical experiment to determine the hydraulic characteristics of liquid outflow. Within the framework of mathematical and physical experiments, the geometric parameters of an orifice-shaped opening in the form of a «curved drop» were determined, which provide a change in the water flow rate in proportion to its opening. In the process of implementing the physical experiment, the following hydraulic characteristics of the liquid flow through an orifice in the form of a «curved drop» was determined: the local resistance coefficient ζ , the speed ratio φ , the compression ratio ε , the flow coefficient μ , the flow rate of water q at different pressures. It is experimentally determined that the valve head, that equipped with a locking element with an orifice-shaped opening in the form of a "curved drop", is characterized by a high regulating capacity. In the range of the handle rotation from 30° to 180° at a pressure of 0.05 MPa, the water flow rate changes by an average of 1.2 % per 1° of adjustment, and at a pressure of 0.3 MPa - 1.4 % per 1° of adjustment.

In the article ˮUse of geosynthetic shells in constructionˮ is presents the results of analysis of the application of geosynthetic shells in construction, in particular: for the construction of artificial islands, dams, retaining walls, highways and railways, foundation of foundations on weak soils, and dehydration of bottom sediments and other suspensions with subsequent use or burial. The technology of constructing artificial islands with the help of geo-shells is described, including the preparation of the construction site, the removal of sharp objects, the installation of a protective layer, the filling of shells on special barges with the help of a dredging projectile and placing them in the necessary place, layered packing of shells with filling of voids with soil, construction with a protective layer of geotextile and a layer of rock outline with further soil deposition in the space formed by the dam, communication and construction on the surface of artificial land. A fragment of the laying of geo-shells during the erection of a dam around the future land is presented, showing the possibility of locating geosynthetic shells in several rows horizontally and vertically to achieve the necessary design parameters, and a cross-section of the protective geotextile layer with anchor pipes along the margins filled with bottom sediments and a geo-shell. The order of production of works for the construction of dams from geosynthetic shells is presented. The advantages of dehydration and utilization of bottom sediments and liquid wastes with the help of geosynthetic shells are included. They consist of ecological compatibility, economicality in comparison with hardware methods, small number of personnel, short duration of work, high pulping rate, complexity of technological processes and the possibility of further use of shells. A systematic waste dehydration technology is provided, provided with detailed comments of each step, and is supplemented with a cross-sectional image of the shell polygon. Based on the patent study carried out, prospective directions for the use of geosynthetic shells have been identified and characterized.

The work is devoted to improving the method for predicting the longitudinal smoothness of the road surface coverage. The purpose of the study was to improve the methodology for predicting the roughness index of the road surface covering taking into account the negative weather and climate factors, the composition of the traffic, and the level of maintenance. The authors conducted a wide analysis and classification of domestic and foreign methods for predicting the change in the longitudinal smoothness of the road surface coverage. It is proposed to improve the accuracy of predicting the smoothness of the coating, based on the improvement of the known linear multifactor model predicting the change in the international roughness index (IRI) depending on the traffic intensity and the initial state of the coating, by including additional factors. As factors, it is suggested to use data on the qualitative composition of the transport stream, namely, the level of impact of heavy trucks, the level of weather and climate impacts on the coverage, as well as the level of road maintenance. As a data processing tool, multivariate linear regression analysis is proposed in Deductor Studio. On the basis of statistical calculations, it is established that the introduction of the indicated correlation factors into the correlation-regression model makes it possible to increase the accuracy of forecasting the international roughness index of the road surface coverage. The authors present the results of using the improved model on a number of highways in the Volgograd Region, which allow us to judge the statistical significance of the model obtained on the basis of the increasing multiple correlation coefficient and the decreasing mean absolute error in verifying the results. Improving the forecasting of changes in the longitudinal smoothness of the cover at the stage of technical and economic calculations will help to increase the objectivity of decision-making in the management of the transport and operational condition of highways.

The systems of ground heat exchangers for heating and cooling of buildings are becoming more widespread. Such systems are practically not used in Russia. This is mainly due to a low cost of energy resources and lack of a regulatory framework. To calculate the systems of ground-based heat exchangers, it is important to know the thermophysical properties of a ground base, such as thermal conductivity. There are no national standards for determining such characteristics in thawed soils. The available foreign calculation methods are characterized either with a low convergence with the experimental data, or developed for a certain type of soil. In addition, the existing methods are mostly empirical, and do not attempt to explain the mechanism of heat exchange in soils. Hence, there is a need to develop a more universal method aimed at predicting and evaluating the processes of heat exchange of soil bases. This paper presents a new calculation model for the thermal conductivity of soils, as well as provides basic suggestions for the derivation of analytical formulas. The presented model takes into account the density, moisture content and temperature of a soil base. The technique presented in the paper makes it possible to use cost-efficient experiments to determine the thermal conductivity of a base. The analytical calculation method is step by step presented in this paper, as well as two exmaples of using this method. The first one is less accurate for a preliminary evaluation, without the need to take probes and conduct experiments. The second one is more accurate, with at least one experiment with a sample of a disturbed or undisturbed structure. The comparison results of the calculated values and the experimental data, as well as the conclusions about the model applicability are given.

This article presents the methods developed to test piles located in buildings under operation. The first testing method allows preserving the stress-strain state of the soil containing a pile, which has been formed during the operation of a building, thus increasing the reliability of the pile load testing. It is achieved by making two notches at opposite corners of the pile shaft, a hydraulic jack is installed in each notch, the reinforcement in two other corners of the pile shaft is cut, and the pile is separated from the pile cap by the tension of the remaining part of the pile shaft at the start of static loading. During the test, the bearing capacity of the pile, which was tested using the proposed method, was from 5 % to 7,1 % greater than the one of the piles tested according to GOST 5686-2012. The second testing method takes into account the influence of the adjacent piles on the tested one. It is achieved by installing deformation measuring devices (extensometers) on the tested and adjacent piles before separating the pile from the cap, which makes it possible to measure the changes of the strain state of the pile shaft during the test, as well as to determine the influence of the adjacent piles on the tested one. Also, the tests determine the actual load influencing the tested foundation pile, which is obligatory, when it comes to developing an engineering design of a reconstruction project. The proposed methods of the static load testing in operated buildings can be used for investigations prior to reconstruction and technical upgrades of operated buildings.