Investigation of pile behaviour with bidirectional static loading test and numerical analysis

Deep foundation system is used for handling of loads in high places from the superstructure in Geotechnical Engineering, in cases where the shallow foundations are not enough bearing capacity. Piled foundations are most commonly used in these systems. Due to the higher load of the superstructure, barette foundation is prefered in case where the system designed as pile foundation exceeds the permissible settlement limit or this system is uneconimical. Barette foundation is rectangular, has a greater bearing capacity than the equivalent diameter of the pile. Bearing capacity and the type of the bored pile and barette which will be constructed in-situ can be determined by the datas obtained after the laboratuar studies and the in-situ investigations in the project area. Several methods are avaliable for determining the bearing capacity of piles. These are the capacity calculations made with static pile formulas considering the engineering properties of soil, pile load tests which are applied in the field and the numerical analysis performed by the finite elements method. Tİp and friction capacity of the barette or pile can be obtained seperately in static calculations. Pile load tests are the most effective methods to determine its behaviours of the in-situ conditions and for testing safety and accuracy of design. The numerical analysis that were performed with the most suitable soil model of constructing behaviour is supported to the control of approaches after the analysis made in the field and before constructing. In this study, to be determined pile behavior and bearing capacity, the conventional pile loading and bi-directional static pile loading test results made with Osterberg load cell and the numerical analysis results made with the finite elements method were compared. Pile and barette foundation design is evaluated to consider the displacement and mobilizing skin friction values that obtained by the field test and nummerical analysis results. For this purpose, the pile and the barette which were done bi-directional static loading and conventional pile loading tests, were modeled with the finite elements method taking into consideration the soil parametres obtained from the field tests. The suitibility of the specified model for the pile and barette has been checked with the displacement values obtained by the analysis conducted in the field and depending on the parametric approaches made during numerical analysis. Theoretical displacement values occured under the test load in the pile and barette which were done capacity calculations, displacement and mobilised skin friction values which have been observed from bidirectional static loading and conventional pile loading tests have been compared with displacement and mobilised skin friction values from numerical analysis.The factor affecting the datas which were obtained as a result of the numerical analysis and the displacement observed in the end of the tets in the field and the skin friction values mobilized along the pile shaft have been examined. Based on the numerical analysis made with parametric approaches and loading test conducted on the field, the displacement values occured in barette and piles in the loading tests with the skin friction values which have been mobilized on the pile and barette sahft has been determined as much as smaller than mobilized skin friction values and displacement values which were obtained as a result of numerical analysis made by the finite elements method in the same soil parameters. The differences observed in the results of field loading tests and numerical analysis has been considered to occur as a reason of that the model could not have exactly showed the characteristic properties of the area made by the numerical analysis with the finite elements method camed out, the behaviour of the materials could not have approved as currently rigid in the model, the distribution which will be occured in the soil during the construction could not have identified and affecting of the analysis results by the construction which has not been careful enough. In this cases, for evaluating of the in-situ loading tests and numerical analysis correctly; soil parameters used in the numerical analysis should be solved in high security by taking average values, borehole logs conducted in the field should be made in close to experimental area, and also the acts of the barette and pile is expected to be generalized by increasing the analysis the usage with the different materials and soil model.