Determining the Capacity of Unknown Foundations

Using a program of mostly non-destructive-testing, the foundation capacity of a nearly 100-year old bridge was determined at a fraction of the cost of what a conventional approach would have cost. Initial proposals to determine the foundation size, depth, and integrity using an invasive/destructive approach of test pits, borings, and coring had substantial costs. The municipality accepted an alternative proposal to perform a combination of non-destructive testing and limited destructive testing. The program incorporated Ground Penetrating Radar (GPR), dispersive technology, and limited borings. GPR was used to determine the reinforcing in the abutments, thickness of the abutment, and if abutments and piers had footings. Dispersive wave technology was used to determine the thickness of the abutment, the depth of abutment, and the general quality of the concrete. Conventional borings were done to sample the concrete, calibrate the NDE, and determine the founding materials. Using this combination of complementary NDE and limited destructive testing, very few assumptions were necessary to determine the foundation capacity and integrity of the nearly 100-year old foundations at a fraction of the cost of an invasive/destructive evaluation.