The article considers the issues of assessing the stability of non-standard soil-geological systems in difficult conditions. An analytical review of modern methods and tools for assessing the stability of embankment slopes is carried out. The features of the work of the embankment in the areas of the spread of permafrost are considered. The features of the design of embankments on permafrost soils with the preservation or partial thawing of frozen soils have been studied. Two versions of the calculated static schemes of sliding surfaces are presented: base - subgrade and base - subgrade - pavement. Based on the results of field studies, the physical and mechanical characteristics of the soils of the embankment and the base of the subgrade were determined, which became the basis for mathematical modeling and assessment of the stability of the embankment slopes. In software packages GeoStab and Geo5, based on the finite element method and the results of field studies, digital models of embankments were built on a weak foundation. The calculation of the stability of the system “base - subgrade” under the action of a standard uniformly distributed load has been performed. Two models of the system and the base - subgrade - road surface are considered: without cracks on the rolling strip and with cracks. It was found that coating defects affect the stability of the system only in the presence of an earthquake of medium strength and more. Recommendations for strengthening the slopes of embankments operating in difficult soil-geological conditions are given.
The article discusses the existing theories of physical and chemical processes occurring in artificial stone based on a cement binder, affecting the dynamics of strength gain. A mathematical model of the continuously increasing strength of the cement stone according to the logarithmic law has been investigated. The authors questioned the adequacy of the application of such theories to exclude the factor of hardening time from experiments aimed at identifying the effect of such measures as the use of surfactants, mineral additives, changes in the water-cement ratio, etc., on the strength gain. The authors proposed to study the influence of such factors on the dynamics of changes in the strength of cement stone as a more efficient tool. The main arguments of the theory of abrupt strength gain and destruction of cement systems are presented. The authors planned an experiment to plot the dynamics of the strength gain of an artificial stone based on a cement binder to assess the relevance of the problem. During the experiment, two batches of specimens were tested, six specimens in each at 3-, 7-, 14-, 28-, 56-and 84-day age, respectively. The values obtained during the experiment showed significant differences at an early age of hardening. The theoretical curves of variation of strength in time were obtained based on the experimental data, within the framework of the existing theory of the strength gain of an artificial stone based on a cement binder. The simulation results were compared with the experimental results and with each other. The arguments were put forward for and against existing theories based on the results of the analysis of experimental studies and theoretical calculations.
The paper considers the issues of crack resistance of multilayer systems made of asphalt concrete, namely: the causes and features of the occurrence and development of "reflected" cracks are investigated. A study of the operational state of highways was carried out and the prerequisites for the formation of defects on the pavement were determined, including the regional features of the work of the road structure. The authors comprehensively studied the causes of internal and external defects and deformations of asphalt concrete pavements. The most popular technologies for sealing cracks and restoring the pavement are considered, the experience of repairing roads in the western part of Russia, Europe and the USA is also investigated. The results of determining the rate of formation and development of defects in the surface of the exploited roads are presented. In laboratory conditions, work was carried out to simulate cracks in two-layer samples of fine-grained asphalt concrete. Test specimens with a height and diameter of 10 cm were made by molding and compacted in layers, a crack was laid in the lower layer of the specimen. After gaining strength, the samples were tested for compression. Analysis of the results of physical modeling made it possible to put forward an assumption about the existence of a relationship between the presence (absence) of internal defects in the coating and the strength of the structure. To confirm the hypothesis, mathematical modeling of the operation of a two-layer system in the GenIDE32 software package was performed. Evaluation of the stress-strain state by the finite element method showed the presence of characteristic zones of system weakening around the defect area. In a two-layer system, there is an increase in internal stresses and strains around the crack, as well as a decrease in the overall strength (stability) of the system. In conclusion, the influence of internal defects of asphalt concrete coatings on the process of formation of "reflected" cracks were identified.
In the work, the adequacy of the hypothesis about the influence of internal cracks on the strength of the coating was tested. The authors reviewed and analyzed the methods of bench testing of road surfaces. A program has been developed for testing samples of a two-layer asphalt concrete pavement in the presence and absence of an imitation crack in the lower pavement layer. Samples-cylinders of the coating were made in the laboratory and tested for uniaxial compression and shear, and samples-squirrels in tensile bending, under various temperature conditions, simulating the conditions of operation of the coating on highways. The test results, in general, confirm the adequacy of the hypothesis put forward and do not contradict the generally accepted theory of asphalt concrete strength. Based on the results obtained, a model of a sample reinforced with geosynthetic materials has been developed. The sample with a fractured geogrid showed higher tensile flexural strength parameters. In conclusion, recommendations are given for increasing the crack resistance of the road surface at the stage of repair work.
The paper studies the matters of multilayer asphalt-concrete systems cracking resistance, specifically we investigated the occurrence and development causes and peculiarities of the reflected cracks. In this study was examined the highways’ state of repair and the prerequisites for the defects formation on the pavement were determined, as well as the regional road structure operation aspect. The authors studied from every angle the causes of internal and external asphalt concrete pavements defects and deformations. The most popular filling of cracks technologies and restoring the pavement are were discussed in this paper, also the experience of roads repairing in the western part of Russia, Europe, and the USA was investigated. The determination results of the formation and develop-ment defects rate on the surface of the operated roads are presented in this article. Cracks in double-layer samples of finegrained asphalt concrete were simulated in laboratory conditions. A prototype model of 10 cm height and diameter were made by molding and densifying in layers, and a crack was laid in the lower layer of the prototype. Af-ter densifying samples were tested for compression. The physical modeling results analysis allows us to assume the dependence between the presence (or ab-sence) of pavement internal defects and the structural solidity. Mathematical modeling of the operation of a double-layer system was performed in the GenIDE32 software package to confirm the hypothesis. Evaluation of the stress-strain state by the finite element method showed the presence of system weakening characteristics zones around the defect area. There is increasing inter-nal stresses and deformations around the crack in a double-layer system, as well as a decrease in the overall system strength (stability). In the end, conclusions about the influence of asphalt-concrete pavement internal defects on the reflected cracks formation pro-cess were drawn.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.