Empirical Bearing Capacity Formula for Steel Pipe Prebored and Precast Piles Based on Field Tests

In this study, analysis of real-scale field pile loading test results on 20 fully instrumented steel pipe test piles will be carried out, to propose a modified empirical formula to estimate the bearing capacity of the steel pipe prebored and precast pile. In addition, to overcome the limited consideration of the surrounding soil capacity of the existing formula, the proposed formula will be based on an expanded standard penetration test (SPT) N value that will consider the realistic conditions of the ground. The formula will be proposed based on a statistical approach to the data points from the field pile loading test, to ensure safe engineering practice and find a reliable formula. The statistical analysis of the data points indicated that the existing formula underestimated the bearing capacity of the steel pipe prebored and precast pile. The proposed formula estimated a 20% higher pile tip bearing capacity and shaft resistance compared with the existing formula. The accuracy and the stability of the proposed formula will be verified by comparing the estimated results with additional field test data. The verification process showed that the proposed formula gave more realistic results and did not exceed the actual bearing capacity of the test piles.