One aspect of the problem of improving the design and construction of structures, the beds of which are composed of heaving soils, is improvement in the accuracy of diagnostics for the frost-heaving characteristics of these soils. Two methods of determining the frost-heaving characteristics of a soil are currently used in engineering practice − indirect and laboratory testing.The indirect method makes it possible to establish the extent to which a frozen soil will heave from computed indicators, the determination of which requires use of certain soil characteristics. Thus, data on grain-size distribution are required for a sandy soil, and an indicator of moisture content, including the in-situ (in the period prior to winter), at the plastic limit, and the critical content for a clayey soil.It is known that in addition to the above-mentioned characteristics, many other natural factors also influence the rate of frosting heaving. Research conducted in this field has revealed the most significant of these factors, and their effect on the magnitude of the deformation caused by frost heaving. This information, which is borrowed from [1], is presented in Table 1.It is obvious that the indirect method does not allow for consideration of many of these factors. At the same time, the prewinter moisture content is not usually determined during engineering surveys, and it is also recommended that it be established by computational means. Consequently, the method in question allows for determination only of the range of variation in the indicators of frost-induced heaving deformation, and it should therefore be treated as an approximate method.The method of laboratory testing permits consideration of a large part of the factors cited in Table 1, and determination of actual frost-heave characteristics. This renders the method in question more preferable in the survey stage, especially when the frost-heaving characteristics obtained are used for the design and analysis of foundations, for example, shallow foundations, etc.In domestic practice, soil specimens have been tested for frost heaving in the laboratory since the second half of the last century. The first instruments for these tests were refitted standard instruments for determination of the relative swelling deformation of a clayey soil. The structural solution Information regarding the development of new instruments for the laboratory testing of soil for frost heaving, and also results of experimental investigations to reduce the heaving properties of clayey soil under the action of an ionic stabilizer are cited.
The paper discusses the negative impact of heaving soil during freezing of a road structure, including heaving formation. The provisions of normative methodology for testing the road structure for frost resistance are considered. The results of indirect and laboratory tests for determining the soil group by the degree of heaving are analyzed. The validity of influence of natural factors on frost heaving is considered. Proposals for improving the normative methodology are put forward.
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