CONSTRUCTION AND GEOTECHNICS

Jet grouting technology is a promising technology for use in the permafrost regions. Existing methods of producing jet grout elements in permafrost soils have a thermal impact on the surrounding soil mass during thawing of the improving zone and hardening of the soil cement. The aim of the study was to determine the thermal effect of the jet grout elements production on permafrost soils during their preliminary thawing with steam. The numerical method in the Frost 3D software package is used to simulate the jet grout elements production and predict changes in the temperature regime of the surrounding soil mass. The temperature increase during the jet grout elements production and the hardening of the soil cement is considered according to the field data. The freezing time of the jet grout element with the surrounding soil mass and the complete restoration of the temperature distribution has been determined. It is concluded that installation of soil cement elements in permafrost soils, during their preliminary thawing with steam, has a noticeable thermal impact on the surrounding soil mass. When improving bases in the permafrost regions using jet technology, it is necessary to make a thermal forecast taking into account heat release during preliminary thawing of the improving zone and hardening of the soil cement

The current issue of landslide danger in Nizhny Novgorod has been studied for several decades. The activation of landslide processes risk increases annually in the spring and autumn periods due to the abundant soaking of the slopes during snowmelt or precipitation. Often a critical decrease in the stability of slopes and slopes occurs as a result of anthropogenic impacts.

The purpose of the study is to solve the problem of ensuring the mechanical safety of underground wastewater disposal facilities and increasing the reliability of their operation, taking into account the current technical condition and the range of natural and man-made external and internal influences. Based on the analysis of the joint work of linear and point underground structures in a ground mass with a combination of influences of various nature, to identify factors influencing the risk of reducing their mechanical safety. When systematically examining the structure as a whole, its interfaces or part of the structures, to identify defects and conditions of their manifestation, which may lead to destruction or loss of stability of the structure as a whole, its interfaces or part of the structures. According to the level of stress-strain state of local interface zones and the boundaries of the distribution of exceedances of maximum permissible values over the structure and the enclosing soil massif, design scenarios and situations are identified that correspond to a violation of the structural safety of the structure as a whole in one case, and in the other – the structural safety of a part of the structure (node) of the structure. The causes and mechanism of defects in coupled structures of tunnels and mines operating under conditions of non-stationary impacts during wastewater transportation have been identified. A methodology and algorithm for conducting joint geotechnical and design calculations are proposed that allow modeling the processes of interaction between the tunnel shell and the ground environment and predicting the parameters of their joint work, ensuring the operation of the structure and its parts within the boundaries of mechanical safety. Based on the results of interaction modeling, the limiting levels of the stress-strain state were determined, both for parts of structures and local interface zones responsible, respectively, for structural and structural safety, and for the structure as a whole - its mechanical safety. Geotechnical protection methods and a monitoring system for ensuring the mechanical safety of spatially and geometrically heterogeneous underground wastewater disposal facilities are proposed.

Tunneling by the shield method often causes deformations in the soil mass and on the surface. With the active development of tunnel boring in the twentieth century, deformations of soil surface and structures have become very relevant topics for the safety of closed work. From the foundations of rock mechanics firstly appeared analytical methods with the consideration of the theories of elasticity for space and half-space. And after that, with reference to the accumulated experience and analysis of field monitoring results a complex of empirical methods appeared. Both groups of methods are still of applied im-portance and, at times, continue to be improved. The aim of the work is a review and comparative analysis of analytical and empirical methods of various authors for determining settlement and distance to the inflection point of the settlement curve (ix), as well as their systematization with reference to their appearance and the features of the development of this field of geotechnics.With the help of a comprehensive comparative and content analysis of various approaches to determining the settlement of soil surface and the distance to the inflection point of the settlement curve (ix) in tunnel boring, the paper presents the main classification of these analytical and empirical methods in their chronological appearance.The analysis of some examples of comparison of analytical and empirical methods for calculating the values of soil surface settlement in the sources of different years provides coverage of the absolute majority of studies from the moment of their appearance for taking into account tunnel-boring operations. Comparative results of available research are presented and some approaches of the most cited studies are analyzed.An extensive review of analytical and empirical methods of the soil surface and structures settlement during tunnel-boring shows that these methods can no longer always meet all the conditions, approaches and standards of modern design methods for geotechnical and tunnel construction tasks. However, understanding the vector of development of these groups of methods provides insight into the development of engineering thought and the accumulation of statistical material of field measurements of half a century tunneling experience.