INTERRELATIONSHIPS OF THE SWELLING AND THE SHRINKAGE OF THE CLAY AND THE LOESSIAL SOILS

Abstract

The article considers the character of the interrelationship between the relative swelling and the volumetric shrinkage of the clay and the loessial soils. The possibility of their adequacy (accordance) or antagonism (contradiction) was estimated. Examples are given from the practice of engineering surveys in Turkey (Ankara clays), Russia (eolian clays, the city of Nevinnomyssk in the North Caucasus) and the USA (forecasting the swelling of clayey soils, Oklahoma), which show the need for simultaneous study of these dangerous properties and elucidation of the factors of their manifestation. The results of experiment and investigations were presented for three objects: the proluvial loessial soils (p III–IV) of the lithological section Desyatnikov (Buryatia); the lacustrine clays (l III–IV) of the test hole 45-b (Primorye, the area of the lake Khanka); the clays of the Jurassic coal-bearing formation (engineering geological boreholes on the survey area, the microdistrict Topkinskiy, c. Irkutsk). The programs «Standard statistics» and «Cluster analysis» of the R-type microstructural parameters were determined by the method of «Microstructure», the composition of clay minerals — using X-ray diffraction analysis. The absence of interrelations between swelling and shrinkage is confirmed by the results of the experiment under conditions of a change in the moisture content of the paste samples (alluvial clay soils), the data for determining these indices for proluvial loess-like sandy loams and cohesive sands of the Desyatnikovo (Buryatiya) section and the clay of the Jurassic coal-bearing formation (Irkutsk). The manifestation of the correlation of swelling and shrinkage was established only for lake clays from the area of Fr. Khanka (Primorye), enriched with smectite. It is shown that the main factors of swelling of clayey and loess soils are the composition of clay minerals, the degree of aggregation (the number of aggregates), the actual content of the fraction < 0,002 mm, the content of primary (free) fine-fine sand (0,25–0,05 mm) particles; as well as shrinkage with the listed swelling factors, is most likely not connected, which is, apparently, the reason for the discrepancy in the manifestation of these physicochemical properties; to determine the degree of danger of the soil strata in connection with swelling or shrinkage, it is necessary to determine the value of these indicators in the course of engineering surveys in laboratory conditions on duplicate samples.