Comparison of the bearing capacities of a small-diameter bored pile obtained from the results of field tests and numerical modeling

Abstract

Abstract. The paper compares the results of modeling static soil tests with a small-diameter drill pile with the data obtained from field tests. The calculations were performed by numerical modeling using the PC software "Plaxis", which is based on the finite element method. This problem was solved in a flat (2D) formulation for an axisymmetric model, which makes it possible to analyze the stress-strain state (SSS) and the interaction of elements of the pile-soil environment system.
 Separate computational models were created for two types of piles made using different technologies: a bored- CFA pile and a drilled pile with partial soil displacement. In order to take into account the preload history in order to maximize the models' approximation to real conditions, the calculations were performed in 4 stages in accordance with the construction sequence: Stage 1 - initial stage (determination of the initial stresses in the soil massif in the natural state), Stage 2 - excavation to the design mark of the pit bottom, Stage 3 - testing of the soils with a pile by static load. Stage 4 - pile unloading. Based on the results of the calculations, the SSS and the interaction of the elements of the "pile-soil environment" system have been analyzed and compared the settlement graphs obtained from the results of the calculations with the data of field tests.
 It is shown that the use of a plane axisymmetric FEM is a sufficiently effective approach for assessing the stress-strain state and understanding the interaction of elements of the pile-soil system, as well as predicting the bearing capacity of piles for further design of the pile foundation before obtaining the results of field tests. In addition, the labor intensity and time consumption of this approach are relatively low compared to other alternative methods.
 With appropriate experience in using this approach in different soil conditions with appropriate comparison with field test data, it can be applied in the feasibility study and final decisions on the choice of a particular type of foundation.