As of September 2007, there were over 67,000 U.S. bridges in the National Bridge Inventory classified as having unknown foundations. The bridges spanning rivers are of critical importance due to the risks of potential scour. In fact, over half of all bridge collapses are due to scour. Not only are these failures costly, they can be deadly for the traveling public. On April 5, 1987, ten people were killed in New York when a pier collapsed on the Schoharie Creek Bridge causing two spans of the deck to fall into the creek. Several other fatal collapses have occurred since the Schoharie Creek Bridge failure. Detecting scour is only part of the assessment that must take place to determine risk of failure and knowing the foundation depth is a critical component of the assessment. While this issue is not new, current techniques are typically invasive or costly. This research explores the feasibility and effectiveness of induced polarization (IP) and electrical resistivity imaging (ERI), near surface geophysical methods, for determining the depth of unknown foundations. In this work, forward models are created to ascertain the effects of the bridge layout on data quality such as varying depths and the impact of adjacent foundations on the foundation in question. Next, an experimental study is conducted at a National Geotechnical Experimentation Site (NGES) to further identify key parameters for the testing design and setup in order to obtain optimal surveys of bridge foundations. The conclusions of the forward modeling and NGES investigations are used to plan the field surveys on four bridges with known foundations. The outcomes of the four bridges show that IP and ERI can be used in concert with one another to estimate the type and depth of bridge foundations. The results of the field surveys are used to create a probability of non-exceedance curve for future predictions of unknown bridge foundations using the methods described in this research.

The thesis is focused on the reconnstruction of the "Old Bridge“ in Bratislava. Part of the reconstruction is the foundations of a new pier and redevelopment of an existing pier. The introduction provides an overview of methods used for the foundations within the river and from there onwards, the most suitable method haas been selected. The piers foundation is designed in several variants, coupled with the drawings. In conclusion, the variants were compared and the most suitable one was selected.

Shelby tube sediment samples collected from the foundations of ten (10) bridges located in the state of Georgia were tested in the laboratory to find their erosional behavior and the correlation of erosion parameters with sediment properties in order to improve the prediction of scour around bridge foundations. These sites were spatially distributed in order to fall into different major river basins and in different physiographic regions. A description of the Valley and Ridge, Blue Ridge, Piedmont, and Coastal Plain physiographic regions of Georgia is included, and the erosion parameters found from flume measurements are associated with their respective regions. Flume measurements were performed using a rectangular, tilting, recirculating flume located in the hydraulics lab in the School of Civil and Environmental Engineering at Georgia Tech. Velocities up to 1.7 m/s and bed shear stresses up to 21 Pa can be achieved in the flume. Regression analysis was performed on erosion rates as a function of applied shear stress to determine the parameters of the erosion function. The resulting parameters, the critical shear stress and the erosion rate constant, were correlated with soil properties and physiographic regions. Experimental methodology was chosen to approach this problem because the involvement of interparticle forces for fine-grained materials makes it difficult to deal with the erosion phenomenon through other means. Nevertheless, analytical description of the erosion phenomenon was included in order to provide a better understanding of it. Linear, exponential and power regression mathematical models for erosion rate were compared, and the two best-fit regression models of erosion rate as a function of shear stress are proposed to formulate a methodology intended to characterize the behavior of a soil exposed to erosive flow conditions. One of them is a linear model to calculate critical shear stresses and low erosion rates. The second model, which is exponential, has the advantage of describing the erosion rate response for a wider range of shear stress values. It is shown that one of the most relevant predictors for the critical shear stress and erosion rate constant in the regression models is the fine material content present in the sample, which is an indirect indicator of the contribution of interparticle forces to the erosion process. Applying the described methodology, a more case-specific calculation of the erosion at bridge foundations can be performed taking into account the actual material in situ.