NUMERIC SIMULATION OF STRESS-STRAIN STATE OF CONTINUOUS FLIGHT AUGER PILE FOOT UNDER REPEATED STATIC LOADING

Taking into account the rapid growth of high structures construction and their requirements, it is important to distinguish significant loads and superstructures. Pile foundations and their combinations are used for such purposes. Complex engineering and geological conditions in the field of construction requires geotechnical grounding of the most appropriate design solution and its implementation technology. Continuous flight auger (CFA) pile technology has become widespread in the field of pile foundation design. CFA piling method allows to make a soil foundation under the pile heel weaker (especially on sandy soils) that causes further settlement, uneven, in particular. Repeated pile preloading static tests can be considered to be an efficient technique of bases deformation reduction that contributes to lower level of settlement and higher load bearing capacity. The results of engineering and geological findings and field tests determine reliability of pile load-bearing capacity and future soil deformation that make any design solution efficient. Due to the lack of clear engineering and geological solution, it is recommended to conduct a series of calculations by means of numerical simulation according to Eurocode 7. The application of modern software package significantly simplifies and intensifies this process providing quite accurate results for further design process. The accuracy of numeric simulation results depends on a selected model of soil ground deformation. Any model is suggested to use ground warp parameters obtained by experimental results. Comparison of laboratory findings with field tests can be considered as the most reliable method for numerical analysis verification. Test calculations with a compressive ?settlement ? loading? curve while conducting field testing help to improve soil model parameters for certain engineering and geological conditions. Only under the conditions of satisfactory results compatibility, soil model parameters can be used for further simulation of bases and foundations behavior, taking into account the influence of superstructures. The results of numeric simulation of stress-strain state multilayer ground warp under repeated static CFA pile loading in Plaxis 3D software as well as the correlation with field test findings have been presented in this research. The advantages of nonlinear elastoplastic Hardening Soil Model widespread application have been demonstrated. HSM model parameters considered in the research made it possible to do the most realistic simulation of a single-loaded pile behavior and soil foundation stress and strain conditions. The methods of numeric simulation of gradual CFA pile loading and unloading in Plaxis 3D software package have been improved. Such methods proved to be quite reliable to simulate repeated ?loading ? unloading? cycles of CFA piles. The comparison of calculation results with CFA pile static field test data showed that the settlement deviation figure is up to 15%.