This paper presents a discussion about the selection of resistance at the interface between concrete and soil for numerical modeling of load tests. This paper presents the evaluation of the ultimate load of eighteen simulations varying the shear strength of the ground, comparing the results with the predictions of □-method for clay piles. The analyzes were carried out for piles of two diameters maintaining a length to diameter ratio of 20. The results showed a discrepancy close to 10% for the case of the shallow and deep pile. The findings have implications for the use of numerical modeling of complex foundation structures suggesting an appropriate interface value in numerical modelling.