Implementation of Cone Penetration Test Technology in Design and Analysis of Driven Piles

Abstract

The design and analysis of pile foundations in Louisiana are based on traditional subsurface exploration methods. This procedure is expensive and time consuming, and it often results in a pile design that is too conservative. The Louisiana Department of Transportation and Development (LA DOTD) has recently adopted the cone penetration test (CPT) technology to design and analyze driven piles. A research effort was undertaken at the Louisiana Transportation Research Center to identify the most appropriate CPT methods for predicting the ultimate axial load carrying capacity of piles driven into Louisiana soils. An evaluation was conducted to rank the CPT methods based on their capability to predict the measured pile load carrying capacity. The top three performance methods were programmed into software, called Louisiana Pile Design by CPT, to facilitate their use in the design and analysis of driven piles by LA DOTD engineers. The current LA DOTD implementation plan is to use the CPT technology to supplement conventional subsurface exploration techniques and to reduce the number of soil borings and pile load tests. A plan for eliminating conventional subsurface exploration completely and replacing it with CPT is still under investigation. The best performing CPT methods were implemented in the design of driven piles on several highway bridges. In these projects, the CPT was capable of identifying the soil stratification at the pile bent location and predicting the pile load carrying capacity. The benefit of implementing the CPT technology in the design and analysis of driven piles over the conventional subsurface exploration methods was also demonstrated.