CONSTRUCTION AND GEOTECHNICS

One of the most common processes occurring in the soil foundation in Russia and negatively affecting the safety of buildings and structures is the process of frost heaving.When calculating the stability of the foundation under the action of tangential frost heaving forces according to SP 22.13330 and 24.13330, it is necessary to compare the tangential frost heaving forces with the sum of the forces restraining heaving and the loads on the foundation. At the same time, to obtain a more accurate result, it is recommended to determine the tangential frost heaving forces according to GOST R 56726 by shifting a soil sample relative to the foundation material at a speed equal to the rate of frost heaving of the soil. The rate of frost heaving should be understood as the rate of soil movement relative to the foundation material when it freezes. However, at present, domestic literature does not regulate the values of the rate of soil heaving.This study provides a review, analysis and generalization of scientific information on the dependence of the parameters of the frost heaving process on various soil characteristics and external influences on it. During the work, the experimental data obtained by other scientists were accumulated.As a result of the analysis of the collected data array: general trends towards an increase in the frost heave rate with increasing soil moisture, towards a decrease in the frost heave rate with increasing soil density and soil skeleton density were identified; recommended boundary values of the frost heave rate and relative deformation for soil types based on the flow index were determined; a method for analytically determining the frost heave rate based on the content of 0.05-0.005 mm particles in the soil was proposed.The proposed analytical methods will allow a preliminary estimate of the frost heave rate based on known soil parameters, without resorting to expensive, long-term tests. In turn, knowledge of the frost heave rate will increase the accuracy of determining the tangential frost heave forces according to GOST R 56726. Thus, the research results will allow a more accurate prediction of the effect of soil heave forces on the structures of buildings and structures

The article describes the experience of foreign studies of soils subject to seasonal freezing and thawing (USA, China, Mongolia, Canada). The article examines the studies and changes in soils subject to freeze-thaw cycles. The effect of freeze-thaw cycles on strength, dynamic and deformation characteristics, including frost heaving and subsequent thawing of soils. The article presents the results of studies of reinforced soils (clays, sands, silts) subject to freeze-thaw cycles. The tests were carried out in laboratory conditions, experimental models were created and numerical experiments were carried out in programs.The dynamic characteristics of reinforced soils were studied on dynamic triaxial test rigs, strength characteristics on shear devices in low-temperature rooms, frost heave and thaw on standard devices for determining frost heave and on devices of our own production, including the influence of freeze-thaw cycles on these characteristics. Geosynthetic materials were used as reinforcement in the experiments. Among the geosynthetic materials selected were: geogrids, geogrids, short-fiber, long-fiber and water-draining geotextiles, geomembrane, two-layer composite geomembrane. In addition to soil reinforcement with standard sheet geosynthetics, one of the ways to improve soil properties is to mix soil with other materials such as fly ash, lime, polymer fibers, cement, silica, rubber particles, the article provides brief results of a study of adding them to the soil. The results of frost heaving studies when mixing soil with steel and sisal fibers are also described. The results of the introduction of geotextiles and geogrids in the construction of roads and railways are briefly described

The influence of various factors, such as the natural and climatic conditions of the survey area, the variability of engineering and geological properties in terms of the depth of the ground layers and in terms of the building area, including waterlogging, heterogeneity of the structure, makes determining the characteristics of dispersed rocks of Quaternary deposits a multifactorial and complex task. The purpose of the work is a comprehensive analysis of engineering, geological and geotechnical studies performed on samples of undisturbed or disturbed structures, which makes it possible to assess not only the quality of the soil, but also the prospects for changing the properties of the geological material with changes in environmental parameters (humidity, load, etc.). The article shows the relevance of using the synthesis of scientific research methods and laboratory methods for determining the physico-mechanical parameters of dispersed soil as the most common rock in solving practical problems of choosing a base at the design stages of building structures or structures according to the first group of limiting conditions (load-bearing capacity). To achieve this goal, the behavior of the soil environment under certain conditions is modeled, and the natural stress-strain state in the array with the expected load from the construction site is reproduced. Based on the results of the conducted research, mathematical models of behavior are described and dependences of relative deformation and porosity coefficient at a given stress are established. The use of modern equipment has made it possible to establish the dependence of the strength characteristics of dispersed soils on the strength conditions. A comprehensive analysis of the research results showed the importance of the data obtained in solving engineering problems, allowed us to assess not only the quality, but also the prospects for changing the properties of the soil base with changes in humidity and load.

The study's object was polypropylene PP-DVU and polypropylene homopolymer. These construction materials are used as components of geosynthetic materials and as a part of pipeline systems and the reactor, which are integrated into a newly built industrial complex designed for the processing of columbite concentrate. During service, the studied materials interact with chemically aggressive environments. The specimens were exposed to a liquid solution of hydrofluoric and sulfuric acids at elevated temperatures. Material degradation was assessed through tensile strength tests, mass changes, microhardness, visual appearance, and moisture absorption. The depth of aging and relative elongation were the most indicative criteria for predicting the lifespan of the polymer material. The aging of the material was determined through water absorption tests and mechanical testing. Aging was also visually evident through a noticeable color change. The water absorption of the aged layer was higher compared to the material that had not come into contact with the medium. The aging depth helped determine the diffusion rate of the medium into the material, which aids in recommending the optimal wall thickness for the product. The material's tensile strength remained the same after the tests, thus making this criterion less valuable. A combination of insitu and laboratory tests showed a positive effect by reducing the overall testing time. Criteria for predicting the lifespan of polypropylene materials used in the reactor for columbite concentrate processing were proposed and substantiated