"Вестник МГСУ"

Geoecological conditions, natural and anthropogenic factors that boost hazardous processes in the territory of Tomsk are considered in the paper. The algorithm of research of geoecological conditions of urban territories is proposed by the authors. The authors have also identified the reasons of hazardous processes and development patterns typical for them; the authors also break the territory into zones on the basis of the level of hazards and risks that the urban development is exposed to. The authors provide their recommendations in respect of the engineering protection of urban lands on the basis of the zoning of the territory of Tomsk.
Comprehensive geoecological research was performed in furtherance of the algorithm proposed by the authors. The research undertaking made it possible to identify the patterns of hazardous processes, to assess the state and sustainability of natural and technological systems in the zones of geoecological risks, to compile a map of urban zones based on the intensity of geoecological risks that challenged the urban development, and to develop a set of actions to assure the engineering protection of the territory, its buildings and structures.

The authors consider varied engineering actions aimed at the protection of pipelines from developing erosion processes with a focus on the conditions of northern regions. Engineering solutions, considered in the article, include prevention of erosion processes along pipelines, protection from suffusion, protection of extended areas having the limit value of the slope angle, and actions aimed at the drainage of areas along pipelines. Prevention of erosion processes along pipelines consists in the restoration of the fertile layer using biological methods, as well as the volumetric soil reinforcement using geological grids. Prevention of suffusion processes consists in the employment of various types of suffusion shields accompanied by the application of geotextile. Berms are constructed as suffusion prevention actions in extended areas having a limit value of the slope angle. This action is used to reduce the water flow energy of drainage ditches and trays along the pipeline. The authors believe that a complete geotechnical monitoring network must be designed and developed to monitor the condition of pipelines and foundation soils.

The authors argue that drainage norms depending on the functional use of territories must be considered as the first step in the design of flood protection systems. Further, calculation of the drainage norm should be performed based on the extent of the flooding vulnerability of areas. Any designer should identify the parameters of hazards that may cause harmful effects, including the groundwater level, the moisture content of soil, contamination of the groundwater and soil, and the change of soil properties by soaking and draining in order to characterize the hazard of flooding processes in urban and industrial areas. The classification of factors affecting the vulnerability of urban and industrial areas is based on the four features, or indicators of vulnerability, including urban, geotechnical, environmental, and operational indicators. An assessment of harmful effects of flooding should be made following the identification of the flooding hazard degree and the vulnerability of the area to flooding. The research findings contain the threshold of the geological safety and the acceptable depth of the groundwater. Any design of engineering protection actions should take account of the drainage norm within the boundaries based on the acceptable groundwater level in terms of the geological safety threshold.

In recent years, domestic and foreign scientific literature and regulatory documents refer to a trend of using the theory of risk in assessing the harmful effects of underflooding on buildings, constructions and industrial sites of various applications. The requirements of state standards, building regulations require carrying out “dangerous impact level assessment within the territory of the existing or forecasted uderflooding”. In this case “the drainage rates accepted in the design of protective structures must in each case ensure the position of the groundwater level below the critical level”. The authors have developed a methodology and specific methods of calculating the permissible levels of ground water for local construction projects based on risk theory and examples of calculation. Based on the research results, the following conclusions were made: 1. In accordance with the existing regulations of the Russian Federation in the design of engineering systems, the protection from underflooding should in each case ensured the position of groundwater levels below the critical level. In this connection, in each case calculations of drainage standards and acceptable levels of ground water must be carried out in the interpretation of the theory of risk. 2. The methodology was offered for calculation of these quantities on the basis of the existing requirements for calculation of the security levels when flooding of city and plant territories. 3. The authors obtained calculated dependencies and developed a method of calculation of the critical level of groundwater for local facilities with regard for their categories and responsibility level, geotechnical, hydrogeological conditions, features of the surrounding buildings, the possibility of hazardous processes induced by underflooding, deterioration of the object, etc. 4. The authors give recommendations for the calculation of the permissible norms of drainage and admissible groundwater depth in the design of engineering systems, protection from flooding of both newly designed facilities and existing and reconstructed objects. 5. The method of calculation is illustrated by an example, allowing not only to assess the rate of drainage and acceptable levels of groundwater for planned and existing facilities, but also to judge the negative impact of underflooding on the object.