Proceedings of the 21st Annual Members' Conference, 1996, San Francisco, CA, (DFI)
Determination of Pile Length using Electromagnetic Methods
W. Ronald Woods, PE & Kirk A. McIntosh, PE
Estimating the lengths of piles supporting existing bridges is becoming of increased importance due to federally mandated bridge management programs and foundation scour evaluations. Currently, the length and apparent structural integrity of some pile types can be estimated using low strain stress wave testing. The purpose of this paper is to introduce a new pile length determination method termed “The Electromagnetic Pile Length Determination Method”. This method can be used to estimate the length of any pile type, which has full-length steel in it. The method consists of inducing a magnetic field in the pile using DC voltage, and measuring the resultant flux density and radial effects of the induced field. The volume of steel in the pile is indirectly measured and the pile length determined through empirical correlation. Currently, the pile length can be estimated to within 5 to 10 percent of its total length, in a period of about 15 minutes. The method utilizes two men and relatively inexpensive equipment. This paper presents a brief overview of the method and summarizes data from over 30 piles where the method has been used to estimate the pile length and the pile length was known prior to testing.
|article #91; publication #18 (AM-1996)|