Buried Plates Research Articles

Reducing the maximum scour depth downstream of the sluice gate using a combination of two buried plates with a sill

ABSTRACT One of the main interests of researchers is the local scour downstream hydraulic structures due to free hydraulic jump, which can cause massive damage or collapse for hydraulic structures. In this study, a new countermeasure was developed to reduce the maximum scour depth by using two buried plates and a sill downstream of the sluice gate. The results showed that the two buried plates were a very effective tool in reducing the maximum scour depth downstream of the fixed apron. It was found that when the two plates were buried at (L P1 /L B = 0.07 with L P2 /L B = 0.14) with a sill installed at (L S /L B = 0.1 with h S /L S = 0.14), the maximum scour depth upstream and downstream of the first plate (Ds 1 and Ds 2 ) was reduced by 57% and 64%, respectively, and the maximum scour depth downstream of the second plate (Ds 3 ) was reduced by 35% compared to the maximum scour depth for the no-plate condition. An empirical formula was developed to determine the maximum scour depth. The study results may be applied in the area of protection design for the fixed apron.

Effect of buried plates on scour profiles downstream of hydraulic jump in open channels with horizontal and reverse bed slopes

Local scour downstream of sluice gates in erosive beds is one of the main concerns of hydraulic engineers because it can cause considerable damage to structures. Many researchers have conducted various studies to predict the maximum depth and length of scour holes and to develop new methods to control this phenomenon. In the methods that have recently been examined, embedded buried plates are used to control the scour in the erosive beds. In this study, using a physical model, the effect of buried plates in erosive beds on the depth of scour downstream of a hydraulic jump was studied. Several experiments were performed in which plates were buried at 50° and 90° angles at different distances from the apron in open channels with horizontal and reverse bed slopes. The results of experiments in which the scour profiles were drawn in dimensionless forms show that the angle and position of the plates are important to controlling and reducing scour depth. In fact, by reducing the angle of buried plates, the maximum depth of scour is also reduced. Also, comparison of the results of a single buried plate and double buried plates shows that using two buried plates at the distances of 30 and 45 cm from the non-erodible bed is more effective in reducing the scour depth. The best distances of the buried plates with angles of 90° and 50° from the non-erodible bed are 45 cm and 30 cm, respectively, in the condition with a single buried plate.

Seasonal and annual variations in the volumetric sediment balance of a macro-tidal salt marsh

This paper examines the spatial and temporal variability in the volumetric sediment balance of Allen Creek marsh, a macro-tidal salt marsh in the Bay of Fundy. The volumetric balance was determined as the balance of inputs of sediments and organic matter via accretion on the marsh surface and outputs of sedimentary material primarily due to erosion of the marsh margin. Changes in marsh surface elevation were measured at 20 buried plates and 3 modified sediment elevation tables from 1996–2002, and detailed margin surveys were conducted in 1997, 1999 and 2001 using a differential global positioning system. Changes in surface area were calculated using GIS overlay analysis and used in conjunction with accretion and erosion data to derive volumetric estimates of gains and losses of sedimentary material in the marsh system. Currently the volumetric sediment balance at Allen Creek marsh is positive. However the processes of erosion and accretion demonstrate seasonal, annual and spatial variability. Inputs to the system include deposition on the marsh surface from sediment laden waters and from ice rafting of sediments. Sediment is deposited onto the marsh surface year round, even during the winter when vegetation cover is sparse, and the amount of deposition in general is not significantly correlated with the frequency of tidal inundations. Based on the data from 1996 to 2002, the mid and high marsh zones experience mean accretion rates of approximately 1.4 cm year − 1 whereas accretion rates in the low marsh region are statistically significantly lower (0.8 cm year − 1 ). The absolute amount of accretion varies between seasons and from year to year. The main loss to the marsh is through erosion of the marsh margin cliffs which can remove a comparatively large volume of sedimentary material in one mass wasting event and which also decreases the vegetated surface area available for deposition from sediment laden waters. The volume of material removed from the marsh margin almost tripled between 1997 (169 m 3) and 2001 (502 m 3) following breaching of the side of a tidal creek channel, altering the patterns of margin erosion and deposition in the marsh system. During this time, however, other sheltered areas of the marsh system, such as along the tidal creek banks, showed evidence of new vegetation growth, increasing the amount of vegetated surface area available for deposition. The processes of erosion and deposition on the marsh surface exhibit considerable spatial variability, with different regions of the marsh being more or less sensitive to seasonal variability in the dominant controls influencing sediment deposition and erosion in this system, namely wave activity, vegetation, ice and water depths. A key factor in predicting how a marsh will evolve and respond to a number of different controls, e.g. sea-level rise or reduced sediment supply, is to quantify both accretion of the marsh surface and erosion of the marsh margin, evaluating the marsh system as a volumetric whole. This study demonstrates that a marsh system should be assessed in three dimensions rather than simply as a surface of accumulation. This is particularly important for open coastal marshes exposed to the erosive action of waves.

Dynamic Responses of Shallow-Buried Flexible Plates Subjected to Impact Loading

The dynamic soil-structure interaction phenomenon involved in a shallow-buried flexible plate under impact loading is investigated both experimentally and numerically. This interaction causes load relief on the buried structure. Plexiglass plates were used as the buried flexible roof structure and low-velocity impact loadings were generated on the soil surface. Measurements of the interaction loads between the sand and the plate, and the accelerations of the buried plates were conducted. A decoupled single-degree-of-freedom model was used to simulate the dynamic responses of the buried flexible plates. The numerical model allows separation between soil medium and the buried structure. Different degrees of load-relief phenomenon are experimentally and numerically observed for the buried plates of three different stiffnesses. The numerical calculation shows good agreement with the experimental results. The results show that the stiffer plates experienced less separation from soil, which was observed in terms of higher loading magnitudes and longer loading durations. The same separation phenomenon was also observed in terms of lower displacement magnitudes and shorter durations.

Defect and Dopant Control During Silicon Epitaxy Using B and Ge

ABSTRACTThe control of dopants, impurities and defects for VLSI of silicon integrated circuits requires a complex set of crystal and processing conditions to be satisfied simultaneously. In order to achieve the maximum yield and highest level of electrical performance for a given device design, we have manipulated the lattice constant and boron doping levels in CVD epitaxial silicon layers co-doped with germanium. By adjusting the ratios of germane and diborane in a dichlorosilane/hydrogen CVD reactor we have obtained buried high conducting layers which are strain-free and lattice matched to the Si substrate. Degenerate boron and boron and germanium codoped epitaxial layers on (100) p-type silicon substrates were investigated. Solubility, electrical activity limits and defect structure of boron in strained and strain-free silicon epitaxial layers were investigated by spreading resistance, SIMS profiling, X-ray and transmission electron microscopy techniques. Bright field and weak-beam dark field imaging of cross-sectional and plan-view specimens were used to confirm the presence or absence of precipitates and threading dislocations. A model has been proposed to describe the mechanism of threading dislocation formation in heavily boron-doped layers. We are now in a position to strategically locate co-doped Si(B, Ge) p++ layers as recombination zones or buried field plates to suit the needs of MOS latchup control, high speed and radiation hard devices, as well as the needs of defect free p++ etch stops for thin membranes and three-dimensional silicon structures.