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Data were presented in [i, 3, 5, 6] on the fracture of glass-plastics under long-term loading. According to the theory in [2], in the presence of a macrocrack, the parameters of the kinetics of crack growth are linked with the theological properties Of the con~osite and itscrack-resistance characteristics under short-term static loading.The main goal of the present study is to experimentally verify certain premises of the mechanics of delayed fracture of anisotropic viscoelastic bodies presented in [2] and to determine the feasibility of using the results in [2] to describe the kinetics of crack growth in polymer composites.The main postulates of the theory in [2] are as follows. The composite is modeled by an anisotropic viscoelastic body. The composite examined was characterized by shear creep, when the creep strains in the direction of the warp and weft can be ignored compared to creep strains in shear. Fracture is described within the framework of the generalized ~k model. Meanwhile, it is assumed that the crack-tip opening 6 and the size d of the prefracture zone are constant at each moment of time for the growing crack.The following equation is the equation of the main period of crack growth, which in the case of a macrocrack (i.e., a crack satisfying the condition d << s where s is the length or half-length of the crack) makes the main contribution to the time to rupture = 1 + qQ (q),

Гаврилов Д.А., Лойко С.В. Фитолиты почв темнохвойный гемибореальных лесов ... // ДОСиГИК. Т. 7. № 1 (13). С.

Dark, coniferous hemiboreal forests in the south of West Siberia are located in the Holocene forest-steppe ecotone, where natural environmental conditions have been quite dynamic. This dynamic environment resulted in the contrasting evolution of regional soil cover and the development of unique soil profiles with the second humus horizon. The second humus horizon is assumed to be a relic from the dark-humus soil formation stage in the mid-Holocene. This article draws conclusions about changes in regional environmental conditions by analysing data from a geochemically interrelated coevolutionary soil series, obtained by using a combination of conventional soil studies, phytolith analyses, and accelerator mass spectrometry (AMS) dating of phytolith-occluded carbon (PhytOC) and humic acids. The results showed that, in general, phytocenoses changed from mire-meadow vegetation towards forest vegetation via the meadow stage. However, these stages had different durations, depending on the soil catenary position. The topographical divergence of soil phytolith profiles reflects the relief effect on the development of specific soil type combinations, accounting for the major elements of the regional mid-Holocene soil cover. The leading elementary soil-forming processes were humus accumulation and hydrogenic accumulation of calcium carbonates. In the hilltop site of Endocalcic Stagnic Albic Luvisols, the evolutionary changes were shown by the shift from the meadow phytocenosis (Calcic Stagnic Chernozem) to the forest phytocenosis. In the midslope site, the environment was more humid from the start, favouring a phytocenosis with features of the meadow-mire type. The shift from the meadow-mire environment (with Spodic Chernic Gleysols) to the forest type environment with leading profile-forming processes, acid hydrolysis and lessivage, was gradual, occurring via the meadow stage with Calcic Stagnic Chernozem. In the toeslope site (Calcic Stagnic Greyzemic Epidystric Umbrisols), the meadow-mire stage (with Spodic Chernic Gleysols) was succeeded by the forest stage of soil formation. The AMS-dating of PhytOC estimated that the dark-humus stage of soil formation began 6.5–5.7 years calBC. Despite the observed slight translocation of phytoliths down soil profiles and phytolith solubilisation, phytolith analysis can be used to reconstruct shifts in the soil formation environment for surface Holocene palaeosols.

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