In northern forests, winter is the preferred time for logging operations, since, when wet soils freeze, their strength increases, which ensures a high load-bearing capacity of winter forest roads and reduces the cost of forestry work by increasing the load on forestry equipment, including when driving through frozen lowlands. The present article analyzes frozen loamy–sandy soil, which, at subzero temperatures, behaves like a brittle material with a sufficiently high, but limited, strength. Well-known models commonly use empirical parameters, correlations, and numerical methods to estimate the strength of such materials. An analytical model of the full load–displacement curve would reduce the number of necessary calculations and increase the ability to predict the bearing capacity of winter forest roads. However, there are few of these models. Such models were developed, as a rule, to study stress–strain in concrete and rocks, meaning that researchers have to recalculate the load into stress and displacement into deformation, which is not always simple. This work aimed at theoretically justifying a new analytical model for quantifying the bearing capacity of winter forest roads and assessing the adequacy of the model by comparing it with experimental data. To achieve this purpose, the concepts of fracture mechanics and methods of mathematical modeling were used. The model was verified using experimental data, and model examples for determining the peak load were provided. Prospects for development of the research topic were also considered, taking into account new developments in forest road monitoring for logging management.
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.
Петрозаводский государственный университет Научно-исследовательский институт леса Финляндии АННОТАЦИЯ В статье приводится описание компьютерной программы, предназначенной для поддержки принятия решений при использовании лесосечных отходов в качестве сырья для производства древесного топлива.
The issue of soil compacted state forecasting during the construction of a forest road is considered. The mechanical system formation of contacting particles of the compacted soil are given and substantiated. A model of compaction of a loose soil layer in the system "compaction device - compacted material" has been developed. A new compartment approach in this field of applied research was used, within which the system under study is subdivided into interconnected units, called compartments, the content of a certain substance in each of them is a separate variable of the system. Various technological situations are analyzed with the minimum and maximum allowable boom outreach of the excavator. The modeling of the effect of porosity on the soil layer thickness during its compaction, denser packing of particles and the appearance of residual (irreversible) deformations has been carried out. A method for determining the relationship between the degree of soil compaction and changes in its porosity and deformations has been developed. The complexity of the theoretical study of the compacted soil is substantiated. The practical significance of the developed model of soil layer compaction and the methodology for assessing its deformations has been confirmed with successful implementation at the design and monitoring stages of the construction of a pilot section of a forest road located in the Republic of Karelia on the basis of Petrozavodsk State University.
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