Simulation the interaction of a pile with the soil using a nonlinear mathematical model with a modified Mohr–Coulomb strength criterion

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Summary. Static pile tests allow determining the bearing capacity of a pile as accurately as possible. They should be carried out in advance, before the foundation structures are installed, because their results are used to decide on the need for adjustments. However, static tests usually require significant time, which is due to their execution technology. The main disadvantage of static tests of a full-scale pile is the cost. They are the most expensive method, but at the same time they allow the most accurate reproduction of the pile operating conditions, namely, the load on the pile from the superfoundation structures of the building or structure. The calculated value obtained from engineering calculations allows only a preliminary and approximate assessment of the bearing capacity of the pile on the soil. This method is the simplest, but at the same time the least accurate. Numerical simulation allows us to approximate the results of static testing of an experimental pile to the results of modeling, provided that the parameters of the soil environment for the selected mathematical model are identified. In this work, the Midas GTS NX software package was used for numerical modeling of the experiment (computer simulation of testing a full-scale pile with a static compression load). In this case, volumetric finite elements were used to model the soil mass and the pile shaft. To describe the regularities of soil behavior under load, a nonlinear law of deformation of the soil environment with a modified Mohr-Coulomb strength criterion was used. This model combines nonlinear elastic and elastic-plastic models. The paper investigates the nature of the formation of the stress-strain state of the soil mass under the bottom of the pile and along the lateral surface of the pile at all stages of loading during computer simulation of a full-scale pile test. The phases of pile operation mainly along the lateral surface and the inclusion of the bearing capacity component under the bottom of the pile are identified. The formation of vertical stress concentrator zones in the soil mass under the bottom of the pile is recorded. The nature of the load transfer to the soil through the lateral surface of the pile is established according to the distribution of longitudinal forces in the pile shaft.