The problem of forest roads improvement is relevant nowadays. The issues of strength of thawed and frozen soils as the materials of forest roads require further research. The article is aimed at the problem of developing a technique for indirect determination of elastic modulus and tensile stresses in frozen soil. It is based on the results of tests on three-point bending of a beam with a developing crack. The authors used methods of experimental and theoretical studies of mechanical systems. Testing was performed with samples in the form of beams with a cross section in the form of a rectangle 55 mm wide and 39 mm high. The span of the beam was 280 mm. The beam material was sandy soil at a temperature of minus 4.6 °C. Three-point bending tests were performed using of test-machine. Based on the analysis of tests a mathematical model is developed to determine the elastic modulus of the beam material and to estimate the tensile stresses in the section with a crack. Tests and results of mathematical modeling confirmed that the destruction of the beam from sandy soil with an evolving crack corresponds to the downward branch of the diagram "load-displacement". The results of the work complement the current understanding of frozen sandy soil functioning and can be used in assessing the status and substantiating recommendations for improving forest road construction technologies.
This article focuses on the analysis of patterns of functioning of forest roads on the example of the Republic of Karelia. At present, most of the logging volumes are in the winter period. However, according to the literature, it is known that climate change may be one of the reasons for the accelerated development of transport infrastructure throughout the year. Taking into account economic feasibility and technical feasibility, in the near future, the problems of improving forest roads of all kinds remain topical. The object of research in the article are temporary forest roads. The subject of the research is the patterns of functioning of temporary forest roads in the winter and off-season periods. The goal of the work is to substantiate recommendations for improving temporary forest roads during off-season periods. Used methods of mathematical modeling and the results of experimental studies. The features of temperature deformations of the unpaved roadbed, which may cause the destruction of the roadway, are considered. The main result is the justification of restrictions on the movement of vehicles on forest roads, if the temperature is-3 ° C and above.
There are a number of urgent tasks related to the forecasting of the state and improvement of technologies for the construction of temporary forest roads. In the present work, the object of the study is a two-layer structure as a model of a straight section (segment) of a dirt road in the stage of seasonal freezing. Conditions of occurrence and parameters of frost cracks in the upper layer of the road during seasonal freezing were simulated. The paper demonstrates the possibility of using mathematical modeling of mechanical systems to analyze the conditions of frost cracks formation in the soil. The considered problem is to predict the distance between frost cracks in the soil. Practical examples of numerical implementation of the proposed approach are presented. The research results confirm that the use of mathematical modeling methods in the problems associated with the analysis of the state of temporary logging roads is a relevant and promising direction; the developed method provides sufficient adequacy of the simulation results, does not require cumbersome calculations; the results of the study do not contradict the data known in the literature; the practical significance of the work is determined by the fact that the presented results can be used to justify technical solutions for improving winter logging roads; the prospects of the study are associated with the refinement of data on the interaction of the frozen soil layer interacting with the underlying soil layer, the temperature of which is non-negative.
Low-temperature cracking is one of the main reasons for the deterioration of the upper layer of roads in regions with cold winters. A large number of works focused on deterioration prevention are known, however the interdisciplinary problem of low-temperature cracking remains relevant. The important, but insufficiently studied factor is the distribution of normal and tangential (shear) forces acting on the upper layer of the road. The objective of the current study was to clarify insight about the distribution of tangential forces in the contact area of the upper layer of the road with the base. There are works in which it is assumed that these forces are distributed by a piecewise linear law. We propose a mechanical and mathematical model and an analytical solution to the problem of the distribution of shear forces in the contact area of the upper layer with the base. The main result of the study: it is found that the distribution of shear forces in the segment of the asphalt concrete layer is described by a second-order polynomial. However, the shear stresses are distributed linearly over the entire length of the segment and reach the highest modulo values in the area of the end sections of the segment. The results of the presented study clarify the understanding of functioning of the upper road layer at low temperatures. By that, the contribution to the solution of the problem of increasing the crack resistance of roads in regions with cold winters is made.
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