Bored Pile Capacity by Direct SPT Methods Applied to 40 Case Histories

Abstract

In these last decades, the in situ tests have known considerable progress caused by the technological development reported in this area, their earlier use were in the foundation design. These technical improvements have permitted more real knowledge of the soils characteristics and/or behavior in different depths.  They became good tools for a geotechnical engineer. Recently, the use of bored piles is multiply around the world because of their moderate bearing capacity suitable in many projects, relatively low cost, easy length adjustments, low vibration, and noise levels during the installation.  An attempt is done in this paper to formulate and calibrated a new method based on the N-value from SPT. Data averaging, failure zone extension, and plunging failure of piles has been noticed in the proposed approach. A data base were collected and analyzed, including 40 full scale static pile load tests through a variety of grounds and stratigraphy around the world. The soil profiles range from soft to stiff clay, medium to dense sand, and mixtures of clay, silt, and sand. The pile embedment lengths range from 2 to 57 m and the pile diameters from 100 to 1220 mm. A performance analysis of the new SPT method is carried out with other prediction methods by using different criteria. The proposed method is suitable tool to practical design of bored piles, due to their consistent results.