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Section 1. Geology
https://doi.org/10.29013/ESR-20-5.6-3-5
Zakirov M. M., Agzamova A. I., Begimkulov D. K., Normatova N. R., Ochilov G. E., Tashkent State Technical University named after Islam Karimov, Tashkent City, Uzbekistan E-mail: [email protected]
ENGINEERING AND GEOLOGICAL PROPERTIES OF EOCENE CLAYS OF THE NORTHERN TAMDYTAU AS THE BASIS FOR ENGINEERING STRUCTURES
Abstract. The article studies clays with high moisture content of the lower horizons of the Northern Tamdytau section, where weathering and salinization is weak, which contributes to their swelling growth up to 19.7%. It is noted that these clays should be classified as slightly swelling - to a depth of 2.0-2.5 m, medium swelling - to a depth of 3.0 m and heavy swelling - from 3.5-4.0 meters or more. The increased swelling value of the lower horizons of clays is because climatic and technological factors do not have an impact on lower horizons in terms of their original material composition and properties.
Keywords: moisture, clays, swelling degree, swelling value, swelling pressure, soil body, ground-water regime, technological factors, hypergenesis.
Recently, the problem of construction development of territories formed by swelling soils is very important. Underestimating and ignoring the swelling properties caused damage to many industrial and civil buildings and structures. Although the swelling processes make the construction and operation of buildings and structures significantly difficult, the areas of their distribution are actively developed. This is due to the lack of available territories for construction with pace showing an upward trend.
Gain in moisture of swelling soils leads to the foundations upheaval located therein and the forma-
tion of negative friction for pile foundations. There are instances where some structures uphove to 580 mm when foundation soils swollen. The soil shrinkage causes structure settlement after drying-out [3; 4; 5]. In some cases, the horizontal swelling pressure on underground structural elements is also dangerous. These studies are highly relevant because active industrial and economic development of territories inevitably leads to imbalance of components of the environment. The groundwater regime is changing, and the soil body moisture is increasing. Comprehensive study and assessment of urban agglomeration
Section 1. Geology
territories and areas of development is one of the most important objectives of engineering geology.
The purpose of the study is to develop a study of technologically impacted soil bodies formed by swelling rocks based on the analysis of identified and justified patterns of formation of their composition, properties and alterations in the hypergenesis zone.
A significant contribution to the study of the methodological features of swelling clays and the identification of their genesis was made by M. F. Vi-kulov, M. Z. Zakirov, V. A. Frank-Kamenetsky, A. A. Sabitov, V. I. Osipov. Later, the swelling processes in different regions were studied by G. A. Ma-vlyanov, A. M. Khudoybergenov, A. M. Samedov, M. M. Zakirov and many others.
The mineralogical composition of soils has a significant impact on the ability to swell. Other things being equal, soils containing montmorillonite in the clay fraction are larger than those containing kaolinite. Kaolinite, having a rigid crystal lattice, interacts with water molecules and hydrated cations (sorbs them) only with its external surface, and montmorillonite, having a sliding crystal lattice (package structure), interacts not only with the external surface, but also to a greater extent with the internal surface of structural layers, that is, these particles are able to absorb water.
It is known that depending on the weakening rate or disappearance of rigid structural bonds, as well as on the rate of formation of adhesive films around solid particles, swelling occurs not immediately after soaking the soil, but within a certain time. With unlimited flow of liquid, the swelling ends when the propping forces are balanced by the applied pressure.
These studies analyze the causes of clay swelling and clay minerals and explain the swelling processes from the perspective of capillary theory, using the aqueous colloidal hypothesis and as a complex physical and chemical process occurring under capillary, adsorption, osmotic and other factors. Thus, swelling is a complex physical and chemical process caused by the presence of water in an inter-wrapper space of the clay mineral crystal lattice, by natural struc-
tural bonds accompanied by compositional changes of exchangeable cations, by interaction of solid particles with pore solutions, by capillary phenomena, etc. The extent to which these processes influence the clay swelling varies and depends on their mineral, chemical composition, dispersion, physical and other properties [1; 2].
At the same time, the temperature factor is important, since the swelling increases with increasing temperature, although it is poorly studied [2; 3]. The influence of material composition of different genetic types of clay rocks on the swelling degree has been poorly studied. Physical and mechanical properties of clay rocks are formed throughout their geological history, from the moment of sedimentation and further transformations during the diagenesis, catagenesis, and hypergenesis processes [4]. When swelling rocks are moistened, it contributes to their softening and disturbance of their natural structure, loss of strength characteristics, transition from a solid and semi-solid consistency to a plastic consistency. These properties of clays should be taken into account in engineering and geological surveys to justify construction projects.
Currently, the clay swelling can be limited or prevented by applying external pressure [1; 2; 3; 4]. The degree of clay swelling decreases with increasing external load. Deformation does not occur if the external load is greater than or equal to the swelling pressure.
The swell value of studied clays, determined by the shake method (in test tubes), is 1.6-10.5 times greater than the initial one (undisturbed structure). There is an increase in the degree of clay swelling with depth. Near surface layers, where there is a greater impact of superimposed (secondary) processes, show the smallest swelling. To a depth of 3.0-3.5 m, the swelling increases by 0.8-2.8 times. In the depth range of 3.0-3.5 m, the swelling is stabilized from 6 to 8 times. Dramatic changes in the swelling values are observed for all samples in the load range from 0 to 0.1 MPa, especially in the range of 0-0.05 MPa.
Numerous studies have shown that at a pressure of 0.1 MPa, the swelling is 2.0-2.5 times less than
at free swelling. Accordingly, the swelling stops at Based on the above, the following conclusion can
a pressure of 0.35 MPa. This means that when the be made:
pressure exceeds 1.0 MPa moistened clays do not - there is a gradual increase in the values with
swell. Such behavior of swelling clays is important the depth of swelling degree, swelling moisture and
when designing structures in urban territories of the swelling pressure;
Northern Tamdytau [5; 6]. - relatively low indicies of eocene clay swelling
The clays of the upper horizons swell despite the in the upper layer of the section are attributable to
weathering and salinity. Increased clay moisture in geological and geomorphological condition, small
the lower horizons, where weathering and salinity amount of natural moisture and high evaporation of
is weak, contributes to an increase in their swelling precipitation, development ofweathering processes,
value up to 19%. The studied clays of the Northern salinity with sulfate and bicarbonate salts;
Tamdytau should be classified as slightly swelling - to - increase in the swelling value of the lower
a depth of 2.0-2.5 m, medium swelling - to a depth horizons of clays is due to the fact that climatic
of 3.0 m and heavy swelling - from 3.5-4.0 meters and technological factors do not have an impact
or more. Numerous swelling measurements of clay on lower horizons in terms of their original ma-
samples with natural moisture content from 10 to terial composition and engineering-geological
25% confirm their high swelling capacity. properties.
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