33 research outputs found
Geotechnical assessment strategy for bridge maintenance – case study.
This paper presents a practical strategy used to conduct a geotechnical assessment, drawing principally on a maintenance work carried out recently for Rashwood Interchange which carries the M5 Motorway over the A38. The bridge, which was constructed in the early 1960s, had experienced long-term settlement attributed to historical brine pumping activities in the proximity of the bridge area. In planning for its maintenance work several issues challenged the geotechnical assessment, including the review of settlement history and mining instability in the area, the exploitation of as-built data records and the determination of foundation response to additional loading during the bridge repair. The paper presents how these complex challenges were approached, yet using simple procedures and common design tools. The procedures are also applicable to other infrastructure maintenance projects, particularly in transportation geotechnics.N/
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The mutual evolution of mountain waves and katabatic flow
Typically, katabatic flows have been studied in their least complicated or idealized state. Further, these flows are generally regarded as having simple forcing and non-turbulent structure due to the strong atmospheric stability they are bedded within. Somewhat analogously, mountain waves and their effects have been mostly studied in their idealized state, i.e. for constant upstream flow and stability. Even in the numerous cases where these two atmospheric phenomena have been studied in their realistic state, seldom has their mutual interaction been considered. One exception that includes numerical modeling is Gross (1990). The express purpose of this work is to examine how each of these phenomena interact with each other in an evolving nocturnal atmosphere. This work is motivated by observations from the Atmospheric Studies in Complex Terrain (ASCOT) Program which clearly indicate non-idealized behavior in katabatic flows. Although numerous idealized simulations were also completed, discussion here focuses on the most realistic simulations of the case night 3--4 September 1993. This night was dominated by clear skies and light near surface winds. A high pressure system to the southwest of Colorado caused northwesterly flow at {approximately} 7 m s{sup {minus}1} upstream of the Rockies with a Froude number of 0.45 overnight. ASCOT observations indicated that katabatic and mountain wave flow were occurring
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Dynamical processes in undisturbed katabatic flows
Idealized analytical investigations of katabatic slope flows have usually sought to simplify the analysis by either assuming a particular force balance amenable to analytical solution or using integral (or bulk) models. In each case, steady state conditions are evaluated, with occasional exception. Historically, the modeling of idealized katabatic flows has focused analysis of model time where steady state conditions have been achieved. To investigate the true dynamics of evolving undisturbed katabatic flow, the Regional Atmospheric Modeling System (RAMS) is used. As described in Pielke et al (1992) RAMS is a prognostic numerical model that contains the three-dimensional primitive equations in terrain-following, non- hydrostatic, compressible form. In addition to standard variables, RAMS was configured to output the various components of the governing equations with high temporal resolution. Each of the simulations used idealized 2000m high mountain topography of a given slope (1{degree}, 2.5{degrees},5{degrees}, or 10{degrees}) on either side of the peak. In the 3-d simulations this mountain becomes an infinite north-south ridge (cyclic boundary conditions in the N-S direction). Vertical grid spacing was set to 20m for the first 500m {delta}z increases to a maximum of 400 m over 72 grid points to 10.5 km. Horizontal grid spacing was 500 m and the number of east-west grid points was 701, 301, 201 and 201 for the 1 {degree}, 2.5{degrees}, 5{degrees} and 10{degrees} mountains, respectively. Only results from the homogeneous with a vertical structure as follows: 0.0 m s{sup -1} to 3000 m AGL, standard atmospheric {theta} lapse rate of 2.5 K km {sup - 1} to 3000 m AGLl, standard atmospheric {theta} lapse rate of 3.4 K Km {sup -1} above that. The simulations ran for 12 hours after model sunset ({similar_to}1800 MST) so that only longwave radiative effects were active
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Assessing the interaction of mountain waves and katabatic flows using a mesoscale model
This paper has two main purposes. The first is to evaluate the interaction of two common complex terrain meteorological phenomena, katabatic flow and mountain waves. Although occasionally investigated together, generally, the large body of literature regarding them has treated each individually. The second purpose is to show the reader the utility of extracting high time resolution data sets of (1) standard meteorological variables, and (2) seldom used, components of the model equations. Using such time series, significant variability is found in the evolving, clear sky, nocturnal boundary layer, when meteorological variability is generally considered to be at its lowest point diurnally. The approach is to use results from three, 3-d, realistic topography simulations produced by the Regional Atmospheric Modeling System (RAMS). RAMS is a primitive equation mesoscale model formulated in {sigma} coordinates. The model is set up with five nested grids that focus on Eldorado Canyon, which is embedded in the Front Range slope of Colorado. On the finest grid {Delta}x = {Delta}y = 400 m and {Delta}z = 20 m for the lowest 400 m above ground level (AGL). The three simulations were: (1) a realistic simulation; (2) the same as (1) but without radiative forcing (referred to as mountain wave only or MWO) and (3) the same as (1) but without boundary nudging and no initial winds (referred to as katabatic flow only or KFO). The case night is 3--4 Sep 1993 from the Atmospheric Studies in Complex Terrain (ASCOT) 1993 field program near Rocky Flats, Colorado. Both mountain waves and katabatic flows were occurring on this night
Crystal structure determination of classical horseradish peroxidase at 2.15A resolution.
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