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- Bauingenieurwesen (BAU) (39) (entfernen)
Bedload transport and hydro-abrasive erosion at steep bedrock rivers and hydraulic structures
(2018)
Abrasion in a concrete-lined sediment bypass tunnel is estimated using a Japanese state-of-the-art prediction model and validated by measured invert abrasion data at Asahi Reservoir, Japan. The model is described in detail, certain shortcomings are disclosed, and a revised version is proposed. The model consists of a kinetic energy term accounting for the impact by saltating particles, and a friction work term accounting for the grinding stress. It is found that the latter term yields concrete abrasion values being consistently a multiple compared to its kinetic term contradicting other research. Based on that, and a possible particle impact angle inconsistency, it is proposed to omit the friction work term. It is shown that the calculated abrasion is overestimated by 138% on average compared with that measured, if both terms are accounted for. However, promising results are obtained with only 30% overestimation by neglecting the friction work term.
To achieve the sustainable use of dams, the development of methods for sediment management in reservoirs is required. One such method includes the use of Sediment Bypass Tunnels (SBTs) to divert sediment around a dam, thereby preventing sedimentation in the reservoir. However, SBTs are prone to severe invert abrasion caused by the high sediment flux. Therefore, it is necessary to establish a measurement system of the sediment transport rate in these tunnels. One system to measure sediment transport in rivers is the Swiss plate geophone, which can register plate vibrations caused by particle impact. In Japan, the Japanese pipe microphone is used, and sediment transport is measured based on the sound emitted by the particle impact. In this study an attempt was made to optimize the advantages of both systems by fixing a microphone and an acceleration sensor to a steel plate. The results of calibration experiments with this new system are presented and compared with the existing methods. It was found that the acceleration sensor can detect sediment particles larger than 2 mm in diameter. Moreover, a new parameter, referred to as the detection rate, was introduced to describe the correlation between the actual amount of sediment and the registered output. Finally, two parameters - the saturation rate and hit rate - are introduced and exhibit strong correlation with the detection rate.
This paper describes the design of the new tunnel invert lining of the 9-foot tunnel at Mud Mountain Dam, Washington, USA. The tunnel diverts all bed load sediments into the tailwater. Major invert abrasion has been observed in the existing steel lining. The new invert design consists of 0.59 m2 and 0.79 m2 granite blocks that are 0.25 m thick and placed tightly together along the tunnel. Stability analysis showed factors of safety ranging from 1.2 to 2.6 against uplift. This will be achieved with strip drains placed in the bedding material along the tunnel. A service-design-life analysis was performed using abrasion prediction modelling.
This model was based on abrasion measurement data acquired from granite field tests at Pfaffensprung sediment bypass tunnel, Switzerland. The estimated annual abrasion depths for the granite were approximately 0.50 mm/year for average sediment transport conditions.
Without adequate measures, reservoirs are not sustainable, neither the
reservoir itself due to continuous sedimentation, nor the downstream ecosystem due to altered sediment continuity. Appropriate actions are inevitable and require a systematic sedimentation management. Sediment bypassing constitutes one effective strategy that routes sediment load around reservoirs during floods. A sediment bypass system has the advantage that only newly entrained sediment is diverted from the upstream to the downstream reach thereby re-establishing sediment connectivity. Hence, such a system contributes to a sustainable water resources management while taking the downstream environment into consideration. This paper gives a state-of-the-art overview
encompassing design, bypass efficiency, hydraulics, challenges due to abrasion, positive effects on both downstream morphology and ecology, and makes design recommendations.
In this paper typical bypass efficiencies of sediment bypass tunnels (SBTs) used to counter reservoir sedimentation are described, distinguishing between two layouts of the tunnel intake. It results that SBTs are an effective measure to reduce the sedimentation of dam reservoirs, particularly of type (A) with intake at the reservoir head. The hydroabrasive wear of tunnel inverts is significant and
has to be mitigated by using adequate invert liners. The invert abrasion can be estimated based on an abrasion model where a correct input value of the bed material resistance coefficient is paramount to limit model uncertainties. Based on abrasion measurements at prototype SBTs typical values of the material resistance coefficient are recommended for high-strength concrete, natural stones and steel liners. The field experiences gathered so far and the comparison of various invert materials suggest granite pavers as a promising lining material for severe abrasion conditions.
Stormwater quality models are usually calibrated using observed pollutographs. As current models still rely on simplified model concepts for pollutant accumulation and wash-off, calibration results for continuous pollutant concentrations are highly uncertain. In this paper, we introduce an innovative calibration approach based on total suspended solids (TSS) event load distribution. The approach is applied on stormwater quality models for a flat roof and a parking lot for which reliable distributions are available. Exponential functions are employed for both TSS buildup and wash-off. Model parameters are calibrated by means of an evolutionary algorithm to minimize the distance between a parameterized lognormal distribution function and the cumulated distribution of simulated TSS event loads. Since TSS event load characteristics are probabilistically considered, the approach especially respects the stochasticity of TSS buildup and wash-off and, therefore, improves conventional stormwater quality calibration concepts. The results show that both experimental models were calibrated with high goodness-of-fit (Kolmogorov–Smirnov test statistic: 0.05). However, it is shown that events with high TSS event loads (>0.8 percentile) are generally underestimated. While this leads to a relative deviation of −28% of total TSS loads for the parking lot, the error is compensated for the flat roof (+5%). Calibrated model parameters generally tend to generate wash-off proportional to runoff, which is indicated by mass-volume curves. The approach itself is, in general, applicable and creates a new opportunity to calibrate stormwater quality models especially when calibration data is limited.
Results from a long-term stormwater quality monitoring program were used to derive total suspended solids (TSS) event load distributions at four small urban environments (flat roof, parking lot, residential catchment, high traffic street). Theoretical distribution functions were fitted to the empirical distribution functions obtained. Parameters of the theoretical distribution functions were optimized with respect to a likelihood function to get both optimized parameters and standard errors. Kolmogorov-Smirnov and Anderson-Darling test statistics were applied to assess the goodness-of-fit between empirical and theoretical distribution. The lognormal distribution function was found to be most expressive to approximate empirical TSS event load distributions at all sites. However, the goodness-of-fit of the statistical model strongly depends on the number of events available. Based on the results of a Monte-Carlo-based resampling strategy, around 40 events should be considered.
BIM Interdisziplinär
(2018)
Nordrhein-Westfalen braucht eine gut aufgestellte Wasserforschung,
um den heutigen und künftigen Herausforderungen im
Land sowie auch national und international gewachsen zu sein.
Eine erste Erfassung der Wasserforschung in Nordrhein-Westfalen
im Sommer 2017 vermittelte Fakten zu Bestand, Defiziten
und Entwicklungspotenzialen. Mehr als 750 Wissenschaftler
forschen in Nordrhein-Westfalen in über neunzig Forschungsgruppen
verschiedener Disziplinen zum Thema Wasser. Die
Schwerpunkte liegen primär in den Ingenieurwissenschaften,
aber auch in den Natur-, Geo-, Sozial-, Wirtschafts- und Rechtswissenschaften.
Universitäten, Fachhochschulen, An-Institute
sowie außeruniversitäre Forschungsinstitutionen tragen zur
breit aufgestellten Wasserforschung bei, die unter anderem in
sechs Forschungszentren und zahlreichen Kooperationsprojekten
untereinander vernetzt ist. Der guten nationalen Vernetzung der
Akteure stehen befriedigende internationale und stark ausbaufähige
europäische Kontakte gegenüber. Die internationale
Sichtbarkeit und Attraktivität der Wasserforschung in Nordrhein-
Westfalen wird ihren Spitzenleistungen in einzelnen Bereichen
nicht gerecht. Ein vertiefter Praxistransfer von Forschungsergebnissen
offeriert der Wasserwirtschaft innovative, praxistaugliche
Lösungen und zudem der Umweltwirtschaft interessantere
Marktchancen. Besonders günstige Randbedingungen
sind in den innovationsfähigen Kommunen und Wasserverbänden
des großen, dicht besiedelten und an Landschaftstypen reichen
Bundeslandes Nordrhein-Westfalen zu sehen. Im nächsten
Schritt wird zu analysieren sein, wie die Potenziale der Wasserforschung
in Nordrhein-Westfalen effizienter genutzt und ausgebaut
werden können, um zur zukunftssicheren und nachhaltigen
Ausrichtung der Wasserwirtschaft in Nordrhein-Westfalen,
zu wissenschaftlicher Exzellenz und umweltwirtschaftlichem Erfolg
des Landes beizutragen.
Ressourcenschonung durch Digitalisierung im Bauwesen. Perspektiven der Industriegesellschaft.
(2018)
In-situ-Monitoring der Reinigungsleistung großer dezentraler Niederschlagswasserbehandlungsanlagen
(2018)
Große dezentrale Niederschlagswasserbehandlungsanlagen
werden mittels kontinuierlicher Gütemesstechnik hinsichtlich ihrer
Frachtwirkungsgrade an Standorten mit hohem Stoffaufkommen untersucht.
Die Bilanzierung der Zulauf- und Ablauffrachten basiert auf dem Zusammenhang
zwischen den abfiltrierbaren Stoffen (AFS) und der Trübung.
Erste Ergebnisse der Installation der Messtechnik, des Datenmanagements
und Frachtwirkungsgrade werden vorgestellt.
AVA - modellbasiert mit iTWO
(2018)
Auf dem Weg in die Kreislaufwirtschaft im Bauwesen. 2. Kollegsymposium am 04.06.2018 in Aachen
(2018)