Weathered rock or IGMs (Intermediate Geomaterials) is still a controversy in designing the bearing capacity of the drilled shaft. At present, Vietnamese standards separately defined the load capacity of the pile in soils and rocks. That leads to both underestimation and overestimation in case IGMs assumed to be soil and rock, respectively. In this paper, a case study of a project in central Vietnam basing on experienced equations, finite element method (FEM), and field measurement was conducted. The static loading and pull-out tests were conducted for drilled shaft with 0.8 m in diameter installing in the weathered rock. In these tests, instruments were installed including the displacement device, strain gage, and extensometers, which were distributed along the drilled shaft to measure the side and tip bearing capacity of the piles. In addition, FEM was employed to simulate the static loading and pull-out tests of the piles. The obtained results indicated that FEM had a similar behavior at the medium loading stage compared to the field tests (static loading and pull-out tests). Thus, FEM could be a potential method that can be used for calculating and estimating the bearing capacity of the drilled shaft in the IGMs layer. An empirical equation was proposed for computing the side resistance of the pile in the IGMs layer. Finally, this study could help to choose properly the pile length in the design of the pile placed on IGMs layer so that the safety and cost-effective problems can be optimized.