Evaluation of frost heave and moisture/chemical migration mechanisms in highway subsoil using a laboratory simulation method

Seasonal processes in cold countries significantly affect the engineering characteristics of highway subsoil over time. Cyclical freeze-thaw leads to changes in thermal and moisture conditions. As a result, road bearing capacity can progressively change from the initial design. In this work, a modified laboratory method was developed, with cyclical freeze-thaw of soil samples and simultaneous supply of deionised water and a de-icing agent (sodium chloride) to the base. The benefits of the test procedure included slow freezing, simulating the conditions that can be experienced by highway soils in cold environments, extended soil column heights and a larger number of identical soil samples, which allowed experimental variability to be assessed. The method included the monitoring of moisture and chemical mass transfer in the soils. Samples supplied with deionised water experienced ice segregation in their upper parts, and significant heave. While soils supplied with NaCl solution behaved in a similar fashion during their first freeze-thaw cycle, the second cycle saw a reduction in the rate of migration of the freezing front within the soils and also less ice segregation and less heave due to increased salinity. Salt was preferentially transferred upwards in the soil columns as a result of the thermal gradient, including negative pressure associated with cryosuction, and osmotic pressure. The new method provides a more realistic laboratory approach to assessing potential freeze-thaw impacts, and the effects of de-icing agents on soils beneath roads, and in different settings.JSC Center (International program “Bolashak”)

The impact of the temperature and humidity state of the road on heat and mass transfer in winter

Sharp diurnal temperature fluctuations in Astana, Kazakhstan, in winter, as well as freezing up to 2 or more meters leading to the destruction of the roadway, especially during the spring thaw, prompted a detailed study of the state of roads. In this work, the temperature and humidity of the highway structure layers were monitored in winter, and the mass transfer of water in the gaseous state due to the negative pressure of cryosuction in the frozen layers was also considered. It was determined that mass transfer of water in the form of steam 1.44 10⁻⁴ g/h per 1 dm3 of soil at temperature fluctuations of -5-8 °C. The rate of vapor passage towards the freezing front in the soil was 0.467 m/h. The freezing of the ground base continued for 132 days in the winter period of 2021-2022 in Astana with the formation of 456.72 g of ice due to the migration of water in a gaseous state in every 1 m3 of soil, which increases the humidity by 40 % or more and significantly reduces the bearing road capacity during the spring thaw. As a solution to the problem of water migration in the form of steam, it is proposed to introduce an additional layer of vapour barrier over the soil base at a depth of -60 cm.Ministry of Education and Science of the Republic of Kazakhstan. Grant No. AP1326886

Heat and Mass Transfer by Vapour in Freezing Soils

This paper is an extended version of our paper published in Cryosphere Transformation & Geotechnical Safety ‘21, Salekhard, Russia, 8–12 November 2021; pp. 366–369.Copyright: © 2022 by the authors. Vapour mass transfer is often underestimated when designing the bases for structures in frost susceptible soils. Intensive and long-term vapour transport may lead to excessive frost heaving and associated issues. A vapour transport model and the algorithm of its calculation is presented in this study based on the results of experimental freeze–thaw cycles of nine soil samples with varied density. The temperature field distribution, air voids volume and the energy comprising latent heat for the phase transition and heat extracted during the temperature drop are the main parameters for determining the vapour velocity and the amount of ice formed. According to the results, the average speed of vapour transport in frozen soils was about 0.4 m/h. The amount of ice built in 1 h during uniaxial freezing due to the saturated vapour pressure difference was 1.64 × 10−5–3.6 × 10−⁵ g/h in loose samples and 1.41 × 10−⁶ g/h to 5.61 × 10−⁷ g/h in dense samples of 10 cm diameter and 10 cm high sections. The results show that vapour mass transfer can increase the risk of ice growth and related problems.Funding: This research received no external funding

Evaluation of frost heave in clay soils

Copyright © 2021 The Author(s). Frost heaving in clayey soils with a low coefficient of permeability raises a lot of questions regarding the cryosuction, surface tension forces, and accompanying phase transfer of water. The freeze-thaw laboratory test results were considered in this work in terms of temperature and volumetric parameters change, dry density, and water mass transfer. The article presents a model for calculating the mass transfer of water (vapour) in the gas state under the influence of cryogenic forces. Findings include the improved understanding of the heat and mass transfer phenomenon during the unidirectional freezing of soils in an open system. Most of the tests for engineering properties registered a slight reduction in relation to strength, cohesion, and angle of internal friction. However, there was a significant increase in the coefficient of permeability after the freeze-thaw cycles with initially dense compacted soil samples, which was due to loosening and moistening of the soil samples during the heave at sub-zero temperatures. The conceptual model for frost heave in soils was developed based on the vapour mass transfer. There was presented algorithm of vapour flow calculation in unsaturated soils using fundamental thermodynamic equations

Phraseological terminology in the English economic discourse

The research is devoted to the phraseological terms that are encountered in English economic texts. The research analyzed lexical-semantic, cognitive, pragmatic, and linguistic-cultural peculiarities of phraseological units. This research extracts 50 phraseological terms from papers in linguistics, mass media materials, business and professional literature on economics. They were distinguished through four phraseological and semantic fields: “monetary relations”, “buying and selling”, “business and management”, and “economic and production relations”. The dominant term “money” was determined. This term has a conceptual meaning, expressed by the positive and negative connotative marking. Phraseological units mean abstract things that take a shape within a specific context. This research explains the use of toponyms, anthroponyms, and zoonyms in phraseological units, as well as the presence of occasional lexemes. Other aspects that were addressed include the main origins of economic phraseological units (mythology, real-life events, characters and persons, literary works, religion), the ethnic, psychological, socio-political and cultural constants of the English economic sphere

Fashioning of Students' Research Competence Through Technology of Project Activities

Objective: The authors provide justifications for changing the current education system, updating the teaching and methodological approach in school specialised education. The paper investigates the issue of fashioning students' research competence through the technology of project activities.Background: Project activity has become widely used since it combines the theoretical and practical parts of the science under study, which allows to set up a connection between its components. Research competence is an integral feature of a student's personality, which manifests itself in a willingness to take an active research position.Method: The authors conducted an experiment to study the problem of improving the quality of students' knowledge upon studying biology in senior school. The participants in the experiment were 120 students of the 10th and 11th years of a specialised school for children with psychological disorders.Results: The authors developed a methodology for the fashioning of research competence. The results of the conducted pedagogical experiment confirmed the validity of the initial assumptions regarding the influence of the use of research teaching methods in biology lessons aimed at improving the quality of biological education.Conclusion: Through project activities, students with intellectual disabilities learn to work in a team. Despite the fact that teamwork is uniting, each of the students learns to independently set the purpose and tasks of the study, analyse the sources presented, present the results of their activities to others. The main signs of project activity include the fact that students learn the technique and technology of working with the project. Project activity allows for the fashioning of students' research competence during the lesson, thereby enabling students to unleash their potential

Évaluation du soulèvement par le gel des couches de fondation gelées dû au transfert d'eau à l'état gazeux

Conference theme: Geotechnical Engineering Challenges To Meet Current And Emerging Needs Of Society....Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP13268861)