Construction and Geotechnics

The article presents the analysis results of influence of shape and dimensions of cross-section, laying depth of mine, cross-section shape and dimensions of underground mine on the daylight surface settlement of undermined territory depending on the different numerical values of the soil lateral pressure coefficient of the surrounding soil. The numerical solution was obtained in an elastic setting using the computer programs «FEA» and «Stability». In the calculations, the elastic modulus of the enclosing rocks is taken equal to the dimensionless constant E /γ H = 500 (where γ; H are the rocks volumetric weight and laying depth of mine), therefore, the numerical values of the vertical displacements gained as a result of the calculations are also dimensionless. This approach is convenient for both quantitative and qualitative analysis, because not only specific values of vertical displacements are considered, but also change patterns of their values depending on changes in the numerical values of the variables of the calculated parameters. Assuming that the displacements in the linear formulation of the problem are inversely proportional to the elastic modulus, their magnitudes can be determined for any other value of E . It was established the vertical displacements of earth’s surface points located above the mine, provided that the depth of its laying is more than 15.2 m and the dimensions of the cross section are greater than 4×4 m, significantly depend on the shape of the cross section and the lateral pressure coefficient of the surrounding rock. In addition, smaller vertical precipitation of the daylight surface corresponds to an underground mine having an exotic and «non-technological» cross section in the deltoid form. Therefore, the problem arises is to obtain such an optimal cross-sectional shape of the mine that would ensure the minimum precipitation of the earth's surface. The cross-sectional shape of the mine must be as “technological" as possible according to its advancement. The subject of further research is the solution of these problems.

To calculate different geotechnical objects (foundations of unique buildings, pile foundation grillages, slab foundations, embankments, etc.) we often need to simplify geometric model. Use of symmetry principles allows to simplify the model without reducing its detail. A relevant issue with the use of symmetry planes is the assessment of calculation results accuracy. The article considers the research of such an assessment for two traditional geotechnical problems: a shallow foundation slab and a shoring of deep excavation. Calculations have been performed with various options of symmetry planes usage: a full-scale model, using one symmetry plane, using two symmetry planes; differences in the ways of representing building structures: 2D and 3D continuum elements. Generating the finite element mesh, we took into account the fact, that the degree of mesh grinding significantly influence the accuracy of the calculation results. That’s why the finite element mesh was divided into two areas: the area of «interest» represented by small sized elements, and the «peripheral» area created by larger elements. We also considered the sequence of technological processes: the initial stage of the calculation is the creation of the initial stress state, the next stage is the creation of the structure (foundation slab, shoring of excavation), the final stage is the force application. The calculation results were evaluated according to the criteria related to the second group of limit states. The controlled parameters for the shallow foundation slab were: maximum and average settlement, relative difference of settlements; for the shoring of deep excavation - the maximum displacement of the enclosure structure. It was found out that to present the construction in the form of 2D-elements it is necessary to introduce additional boundary conditions. They prevent rotation in nodes located on the plane of symmetry. The authors make conclusions and recommendations for creating design models with the use of symmetry planes.

Underground structures like diaphragm and pile walls are constructed to organize waterproof curtains, protect pit sides, and transfer loads from the structures. Violations of the construction technological process can lead to the formation of defects. To prevent adverse consequences, before excavation, it is necessary to control the integrity of the slurry walls using non-destructive geophysical methods. A review of geophysical slurry wall quality control methods based on the excitation and registration of physical fields through access tubes installed in the reinforcement cage, in wells drilled near the structure or on the surface of the structure, is presented. The main capabilities and limitations of the methods are given. Cross-hole ultrasonic logging was used to study the section of the slurry wall during the construction of the Moscow Metro station. The results of parallel soundings made it possible to identify anomalous zones, interpreted as defects. The geometric dimensions of one of the major defects were refined by ultrasonic tomography. For the first time in Russian testing practice, thermal integrity profiling was applied to study the diaphragm wall at the base of a residential building. The results of temperature monitoring during the concrete hardening are presented. According to the method, a major flaw, excess of the design mark of the wall bottom and bulging of the structure were revealed. The results of thermal integrity profiling were verified by ultrasonic logging. The combined use of thermal and ultrasonic methods can be recommended as a reliable tool for integrity testing of diaphragm and pile walls. To carry out the measurements, the access tubes shall be included in the reinforcement cage of the structure at the design stage.

Sewage networks are one of the main and important urban communications. When sewage move through the collector, harmful gases are released through leaks in wells, penetrate into the residential area of the city and causes a negative impact on the human organism, and also causes chemical deformation of collector and related facilities. One of the gases is hydrogen sulfide, which belongs to the II hazard category. The object of this study is the gravity sewage pipeline of the city, located after the stilling basin, considered in the article as the most problematic, in terms of high concentrations of hydrogen sulfide in the subroof space. The research methods used include the analysis of literature on the topic under study, experimental studies on measuring temperature, atmospheric pressure, studies of the concentration of emitted gases over time in the current collector - collected and systematized data on the constructive characteristics of the collector. Instrumental data on atmospheric air temperature and industrial emissions, atmospheric pressure and pollutant concentrations in industrial emissions of control points of sewage facilities during different seasons of the year are presented. The purpose of the article is to obtain the data necessary for calculating the natural draft depression of the air-gas mixture in the reservoir. According to the results of calculations based on the data collected during the annual period, conclusions are drawn about the absence of natural draft in the drainage collector and the need for taking measures to organize artificial ventilation of the collector, as well as calculating the depression created by the captivating ability of the fluid.

This article discusses world practice in the field of modular construction. The aim of the study is to identify possible ways of applying modular housing technology in the Russian Federation. The goal was achieved through the application of general scientific research methods within the framework of comparative, logical, statistical analysis, etc. Modular construction technologies, such as volume block construction (OBD), multilayer glued wood panels (CLT panels) and light steel ones, were examined and analyzed. thin-walled structures (LSTK). These technologies are seen as the optimal and effective direction, in connection with which the Russian Federation should consider this modern building system as one of the ways to solve the problems associated with the lack of living space. The advantages and disadvantages of modular construction technologies are generalized, an analysis of the world practice of applying this technology indicates the prospects of the direction, since these technologies can be used in almost all areas of construction where there is such a need, for the simple reason that they correspond to all those trends and trends, to which humanity aspires. Practical recommendations are proposed to improve the technical and regulatory legal framework of the Russian Federation in order to promote the sustainable development of modular construction using the volume-block method (HBS), laminated wood panels (CLT panels) and light steel thin-walled structures (LSTK). The results can be used to optimize modular construction technologies, improve them, as well as eliminate the factors that create obstacles for the end user.