CONSTRUCTION AND GEOTECHNICS

The article provides an overview of ways to strengthen the soil base by high–pressure injection – injection in the hydraulic fracturing mode. During high-pressure injection, a cement-sand solution under pressure disrupts the continuity of the soil mass and fills the cavities formed. After hardening, the formed injection bodies reinforce the base and seal the surrounding soil.The high-pressure injection method allows solving a large number of geotechnical problems. However, its significant disadvantage is the uncertainty of the number, direction and size of cracks resulting from a violation of the continuity of the soil mass at an injection pressure exceeding the structural strength of the soil.Currently, there are several approaches to solving this problem: the use of special design injectors; the implementation of technological techniques that localize the spread of the injection solution; the method of group high-pressure injection.As a result of the review, prospects for further research on improving the method of high-pressure injection are outlined.

The proposed article presents the results of comparison of the values of the maximum allowable load on the base of a double-slot foundation obtained by three methods: the SP (SNiP) method, the method based on the construction of the uprush prism, and the method based on the analysis of the stress state of the soil foundation. It turned out that the value of the lateral pressure coefficient significantly affects the value of the ultimate load. The greater its value, the greater, with all other conditions being equal, the friction forces acting on the lateral surfaces of the vertical walls of the slotted foundation and, consequently, the bearing capacity of the foundation. The graphical dependences of the value of the ultimate load on the numerical value of the lateral pressure coefficient for the soil conditions of the considered example are approximated with 100% reliability by an exponential function. The values of the ultimate load calculated with the help of the FEA computer program from the condition of the plastic deformation areas interlocking can be both higher and lower than the values obtained by other methods. It has been established by back calculation that the ultimate load values obtained by these methods for identical conditions correspond to specific values of the lateral pressure coefficient if the ultimate load is determined based on the condition of the interlocking of plastic areas under the foundation footing. That is, the method based on the analysis of the stress state of the foundation is common to the two methods mentioned above. Proceeding from the fact that the calculated values of the ultimate allowable load obtained on the basis of the SP (SNiP) methodology correspond to the results obtained with the FEA computer program at certain values of the lateral pressure coefficient, it seems possible to recommend this program for calculating the foundations of slotted foundations according to the first group of limit states.

Geological conditions with great uncertainty always go through a schematization stage. It can be realized in different ways. For example, in the form of stochastic approach, when ground parameters are random variables with the indication of the distribution law. Such an approach is not used to describe the ground environment for construction. The main approach is deterministic approach with statistical separation of IGE and indication of their boundaries. In this method, the boundaries of separation are often conducted conditionally and expressed in the form of engineering-geological sections. Traditionally, the connection of IGEs between geologic excavations is made by lines or curves. Based on geologic sections, it is difficult to create a spatial geologic model for numerical calculations because the outer boundaries may be significantly distant from the geotechnical engineering study area. To build a spatial engineering geologic model, it is proposed to use the geostatistical method of Kriging, which creates a surface of separation of different IGEs in space. In this case, the created surface of IGE separation will depend on both statistically processed parameters and their position. The advantage of Kriging is the possibility to extrapolate the obtained results to the boundaries of the computational domain of modeling. In the paper, nine different theoretical variograms were selected from the initial data and the results of numerical calculation of a shallow-deposited slab were evaluated.

The optimization of the cost-to-performance ratio has been widespread in bridge construction nowadays, and to improve it, it is best to maximize the structure's efficiency in the initial stages of the design process. By integrating cutting-edge and powerful Building Information Modeling (BIM) technologies, new project design approaches have been developed in the bridge construction industry. Design is moving from conventional 2D drawings to 3D modeling, and the use of parametric design may make it possible to have several variants of the same model in a single file. Information-based parametric design is currently favored by many bridge engineers and designers as a method to overcome the limitations of current bridge industry technologies. The process of building a complicated structure like a bridge has become considerably simpler and more efficient thanks to parametric design and visual programming in BIM. This article aims to describe a parametric approach to the adaptation and design automation process of the information modeling design of the Helix Bridge. Its distinctive design is reminiscent of a double helix, inspired by the structure of human DNA, and its overall length of 280 meters makes it one of the longest pedestrian bridges. Parametric scripts are created using the Grasshopper visual programming language, and the model can be integrated into BIM software like Tekla Structures and Revit for further detailing and strength calculation. Plug-ins are used to develop the algorithms for each and every bridge element, and because attributes are linked, the model changes automatically. In parametric BIM modeling, a virtual model of the Helix Bridge may now be developed in a digital environment while also being enhanced with different types of information. The parametric model's integration into many software packages has made the design automation process for the Helix Bridge flexible and saving time and effort.

The significant inventories of synthetic gypsum – the wastes of different productions are the promising raw material for building materials industry. In this work the waste of etching acid industry – fluoroanhydrite has been investigated. The microstructure of fluoroanhydrite binder in comparison of gypsum binder has been analyzed by scanning electron microscopy method. On the base of high-grade gypsum G-16 the composition of composite nonshrink gypsum-fluoroanhydrite binder contained 15 % of fluoroanhydrite has been selected. The mechanical properties and microstructure of gypsum-fluoroanhydrite binder that had been mechanochemically activated using such activators as fly ash, Portland cement and manganese sulfate have been explored. The activation of binder had allowed to increase its compressive strength by 46 % and to provide the value of softening coefficient no less than 0.75. On the base of activated gypsum-fluoroanhydrite binder the composition of dry mixture for self-levelling floors was selected using methods of mathematical experimental design. The optimal dosage of admixtures of hyperplastisizer, defoaming agent and setting time retarder had been found. The developed composition is nonsrink and has high strength and adhesion to concrete basement and also it is not inferior in quality to dry construction mixtures for self-levelling floors presented at the modern construction market.