Microbially induced calcite precipitation (MICP) was used to treat several sandboxes filled with naturally occurring beach sand collected from Atlantic Beach, Florida. A surface-spray/percolation technique was used to treat these sandboxes where a relatively high-concentration bacteria solution and high-concentration calcium chloride/urea solutions were applied directly to the boxes’ surfaces. Several different treatment combinations were tested whereby bacterial optical density, bacteria/urea/calcium chloride volume relative to pore volume, and bacteria/urea/calcium chloride ratio were manipulated. Treated sandboxes were tested for erodibility using a pocket erodometer. In addition, sandboxes were dissected after erosion testing to examine crust depth. Results showed that higher optical densities, higher bacteria quantities relative to void volume, and higher bacteria quantities relative to urea led to lower erodibility and greater crust depth. When MICP constituent quantities were maximized to give the best erosion/crust-depth results, erodibility improvements began to approach what may be considered adequate erosive resistance. Further investigation is required to better classify this behavior more quantitatively.

In recent years, the Florida Department of Transportation (FDOT) adopted a form of performance-based maintenance contracting (PBMC) that it calls the asset maintenance contracting (AMC) program. This case study presents an analysis of the AMC program in Florida using a survey, an interview, and content analysis. Although similar studies have been conducted in the past, the survey presented here is unique in that the opinions of contractors and lower-level state employees were solicited. The results indicated that contractors were more confident in the success of the AMC program than were the state employees in Florida and that the cost and performance data needed to be maintained for quantitative analysis. The results highlighted the need for partnering between state agencies and contractors, emphasized the need for a shared-risk model, and stressed the importance of a well-defined scope and of quantifiable performance measures. The unique work associated with this paper included the use of contractors and lower-level employees in the survey and the use of content analysis to examine the interview responses. This was the first study of its kind conducted in Florida.

This paper begins by demonstrating how the Florida Department of Transportation (FDOT) local scour equations take the ratio between grain size and structure size into account when computing equilibrium local scour depth and contrasts this with the well-known Colorado State University (CSU) equation that does not take sediment information into account. Then, a relatively recent empirical formulation from the J-L. Briaud research group for computing local equilibrium scour depth is presented that appears to take the structure size/grain size ratio into account indirectly. Next, a possible explanation for the dependency between local equilibrium scour depth and the structure/grain size ratio is presented that was originally developed by D. Max Sheppard in 2004. This explanation shows that superimposing the pressure gradient around a particle with the pressure gradient around a pile leads to the dependency between equilibrium scour depth and the grain size/structure size ratio. Finally, a new formulation for local equilibrium scour depth based upon turbulent energy spectrum decay is presented. This new formulation reduces the local scour problem to a problem whereby turbulent diffusivity must be better understood. However, this new formulation also appears to show a dependency between equilibrium scour depth and the grain size/structure size ratio. Overall, the analysis presented herein provides several reasons, explanations, and pieces of evidence to suggest that the grain/structure size ratio is an important parameter to consider when computing local equilibrium scour depth.

So-called “Type IX” chute spillways with impact baffle blocks have been used successfully around the globe for over 50 years. A key advantage of the chute spillway is the elimination of a costly stilling basin allowing for a more simplistic outlet works design. The current design process is based upon physical models developed in the 1950s and observation of completed projects over the last 50 years. The design procedure is empirical and provides the designer with a range of workable layouts, baffle heights, and baffle spacing. Unfortunately, this approach may not be optimal. This first study of a longer research effort focus uses Monte Carlo simulations and computational fluid dynamics (CFD) to examine the design methodology and physical model basis for the current design procedure. Initially, the study examined the design procedure with a Monte Carlo simulation to explore the range of acceptable designs that can be realized. Then, using CFD, full-scale prototype (located in Gila, Arizona USA) physical model results that were a key basis for the current design procedure were recreated. The study revealed that a wide range of acceptable chute designs can result from following the current design procedure but that some of these may be better than others. The study also outlines future research efforts needed to revise the current design methodology.