Laboratory and experimental tests in huge amount are required during engineering surveys for large and critical buildings and structures especially in complex geological conditions. The laboratory investigations are applicable in cases with no possibility for field tests. However, as a rule the results obtained from laboratory investigations (in particular compression tests) show conservative values of deformation modulus, which leads to underestimate of soil foundations load-carrying capacity, cost increase of foundations for buildings and structures as well as significant overrun of expensive construction materials. The paper shows laboratory tests results (compression and stabilometric) for unixial and triaxial compression of soil samples; results of field plate-load tests for vertical pressed load over natural soil massif. It also brings comparison of stress-strain properties obtained by results of compression, stabilometer and plate-load tests with derivation of regional correction factors for Nur-Sultan City (Kazakhstan). In case of using the recommended regional coefficients while determining the overall deformation modulus by laboratory tests, a significant economic effect is achieved as a result of cost reduction for materials and construction of foundations for buildings and structures.
ABSTRACT:The bearing capacity and settlement of pile foundation were greatly influenced by the temperature variations of soil ground around pile foundation. This paper presented a short report about laboratory static load tests by model precast concrete piles (cross-section 4 × 4 cm and length of 60 cm) in seasonally freezing soil ground. The depth of frozen soil was 10 cm, temperature -5℃, -10℃, +20℃. There were many factors influencing on pile foundations, such as ice in the ground, low temperatures and moisture of the soil. A series of tests of model piles in seasonally freezing soil ground were carried out, the results of bearing capacity of pile foundations and a settlement were compared. The results of the experiments were shown in charts. By application of numerical modeling the pile and soil base interaction vertical deformation in thermal changes of soil ground, the different settlement of piles. Modeling of thermal conditions of soils in software in accordance with real conditions on the construction site of Kazakhstan, analysis,and comparison of the obtained results ofthe settlement of pile foundations at low temperatures are presented in the paper.
Development of a geotechnical database for the young capital of Kazakhstan, Nur-Sultan city, became a paramount concern of both the scientific community and industry. The creation of the Kazakhstan model of the geotechnical database was based on a fixed dataset which included a city map with determined X, Y, and H coordinates and the user generated data obtained from the materials of engineering and geological surveys from more than 2000 boreholes. Based on the assessment of the built-up area of the city, six main engineering-geological elements (EGE) were identified. The territory of the city was regrouped into eight zones instead of the previous six based on the geological origin and stratigraphy interposition of the EGE. Engineering properties of the soils were considered for physical and mechanical characteristics, where the plasticity limits demonstrated an accurate correlation to the elasticity modulus E and distribution boundaries between the alluvial and eluvial types of the soil on the graph. So, the increased liquid and plastic limits are replicated by higher values of elasticity modulus E, and hence better strength characteristics of a particular soil layer and vice versa, while the moisture content and soil density did not show any obvious pattern and requires additional verification on the construction site. Finally, a geotechnical map was built for the driven piles and the optimal variations in the pile length for each zone were determined.
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