EFFECT OF THE STUDY SCALE ON SETTLING AND DEFORMATION MODULUS OF ELUVIAL CLAY SOILS 

A. G. Baranovskii

RITOS Ltd., ul. Komarova 112a, Chelyabinsk, 454071 Russia

Е-mail: geologia85@mail.ru

The variability of settling and deformation modulus of eluvial clay soils under the influence of external loading is studied in laboratory and in field. The object of study is Mesozoic eluvial clay  formed as a result of chemical weathering of granite gneiss, and being widespread in the area of Chelyabinsk. This study is aimed at assessing the effect of research scale on settling value and deformation modulus of Mesozoic eluvial clay soils, as well as at identifying their temporal change patterns upon the increasing external pressure on soil. In this case, the scale of study refers to the test area  or the impact area on the studied soils, to which the interaction between the experimental device (a stamp loaded for assessing the deformability of ground massifs or a compression device for testing soil samples) and soils is restricted. To achieve this goal, field and laboratory studies of eluvial soils were carried out in the designed civil construction area. The variability of settling and deformation modulus of eluvial clay soils was assessed by comparing the data of laboratory studies of the physical and mechanical properties of eluvial clay soils with the data of field tests with a type III stamp (S = 600 cm²). A comparative analysis of field and laboratory studies showed that the scale of research has an important effect on settling and deformation modulus of the studied soils, namely, the deformability of eluvial clay rises with an increase in the impact area. As proceeds from the graphs S = ƒ (P), built on the basis of field and laboratory studies, under the same normal loads, most often exceeding 0.3 MPa, linear elastic deformation of the soil goes in the odometer; whereas, in field tests, the eluvial clay undergoes plastic deformation. This is caused by different stress-strain state of soil in a massif and in a sample. In addition, structural bonds have an important effect on the deformation and settling of the soil, which should be taken into account according to the results of these studies. Time analysis of the experimental data revealed the dependence of settling on time and external pressure. The research resulted in obtaining the multiple regression equations, which permit predicting the settling variation with time.

Keywords: eluvial clay soils, field and laboratory tests, time changes, physical and mechanical properties of soils, vertical static load, plate load test, soil deformation modulus, settling, study scale, area of experiment, regression equation

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