Sediment and Hydrologic Budgets for the Lake of the Woods Watershed, Champaign County, Illinois

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ANALISIS TEGANGAN DENGAN METODE ELEMEN HINGGA PADA SPILLWAY BENDUNGAN DENGAN PENGGANTIAN BENTUK MERCU.

Air melimpah pada musim penghujan dan sangat sedikit ketika musim kemarau, sehingga bendungan harus didesain sedemikian hingga dapat menampung air untuk digunakan pada musim kemarau dan harus dapat mengalirkan air yang berlebihan ketika musim penghujan, melalui spillway. Spillway harus bisa mengalirkan air sehingga air tidak melimpas melalui badan bendungan. Penggantian bentuk mercu spillway adalah salah satu cara untuk meningkatkan debit aliran mercu pelimpah. Tujuan penelitian ini adalah untuk mengetahui letak terjadinya tegangan yang berlebihan. Mengetahui perbedaan tegangan yang terjadi pada badan spillway dengan penggantian bentuk mercu spillway. Mengetahui letak bagian spillway yang harus diberi perkuatan. Penelitian ini meneliti tegangan dalam struktur bangunan spillway dengan penggantian bentuk mercu spillwayogee dengan bentuk mercu trapesoid pada bendungan Jatibarang, Semarang, Jawa Tengah. Dikarenakan bentuk mercu trapesoid yang tidak prismatis pada arah longitudinal maka analisis dengan alat bantu SAP2000 menggunakan elemen solid 3D. Dari hasil analisis didapat peningkatan tegangan akibatpenggantian bentuk mercu spillway untuk tegangan normal arah X-axis terjadi peningkatan pada kisaran 0% - 43366,93%, Y-axis pada kisaran 0% - 32767,74% dan pada arah Z-axis dalam kisaran 0 – 132349,32%, angka tersebut pada segmen dasar mercu spillway. Pada segmen badan spillway dan dasar spillway peningkatan tegangan normal pada semua arah akan semakin berkurang. Kata Kunci : Metode Element Hingga, Trapesoid Spillway, Ogee Spillway

Predictive Modeling the Free Hydraulic Jumps Pressure through Advanced Statistical Methods

Pressure fluctuations beneath hydraulic jumps potentially endanger the stability of stilling basins. This paper deals with the mathematical modeling of the results of laboratory-scale experiments to estimate the extreme pressures. Experiments were carried out on a smooth stilling basin underneath free hydraulic jumps downstream of an Ogee spillway. From the probability distribution of measured instantaneous pressures, pressures with different probabilities could be determined. It was verified that maximum pressure fluctuations, and the negative pressures, are located at the positions near the spillway toe. Also, minimum pressure fluctuations are located at the downstream of hydraulic jumps. It was possible to assess the cumulative curves of pressure data related to the characteristic points along the basin, and different Froude numbers. To benchmark the results, the dimensionless forms of statistical parameters include mean pressures (P*m), the standard deviations of pressure fluctuations (σ*X), pressures with different non-exceedance probabilities (P*k%), and the statistical coefficient of the probability distribution (Nk%) were assessed. It was found that an existing method can be used to interpret the present data, and pressure distribution in similar conditions, by using a new second-order fractional relationships for σ*X, and Nk%. The values of the Nk% coefficient indicated a single mean value for each probability

Testing of Concrete Abrasion Resistance in Hydraulic Structures on the Lower Sava River

The paper deals with the issues of resistance of concrete linings to long-term abrasion loading caused by waterborne particles, particularly for the proposed hydro power plants on the Sava River in Slovenia. The main purpose of the research work was to define the possibility of forecasting the process of concrete lining wear on the Sava River dam structures based on the standard procedures of abrasion resistance testing. Abrasion resistance of concrete has been researched in accordance with the standard ASTM C 1138 and Böhme (DIN 52108) methods. The research work was based on a comparison between laboratory results and measurements of abrasion resistance of concrete under natural conditions by performing test plots in the stilling basin of the Vrhovo HPP. Concrete composites with different mechanical properties have been analysed within the research programme. The analysis showed a qualitative similarity of the level of concrete abrasion between laboratory simulations and measurements in the field, as well as suitability of the ASTM C 1138 laboratory method for the assessment of\ud abrasion resistance of concretes in the spillway of the HPP chain on the Lower Sava River

Anderson Dam Spillway Design

This Senior Design Project is a spillway design option for the proposed Anderson Dam based on the Santa Clara Valley Water District Seismic Retrofit Project. The focus was to design a spillway resistant to cavitation to prevent a failure similar to the Oroville Dam Crisis in 2017. The design includes initial concept designs for a morning glory spillway and a chute spillway, followed by initial structural design and hydraulic verification for the chute spillway option. Hydraulic verification was done using Flow 3D and Flowsight to create accurate hydraulic models of the spillway

Phreatic seepage flow through an earth dam with an impeding strip

New mathematical models are developed and corresponding boundary value problems are analytically and numerically solved for Darcian flows in earth (rock)–filled dams, which have a vertical impermeable barrier on the downstream slope. For saturated flow, a 2-D potential model considers a free boundary problem to Laplace’s equation with a traveling-wave phreatic line generated by a linear drawup of a water level in the dam reservoir. The barrier re-directs seepage from purely horizontal (a seepage face outlet) to purely vertical (a no-flow boundary). An alternative model is also used for a hydraulic approximation of a 3-D steady flow when the barrier is only a partial obstruction to seepage. The Poisson equation is solved with respect to Strack’s potential, which predicts the position of the phreatic surface and hydraulic gradient in the dam body. Simulations with HYDRUS, a FEM-code for solving Richards’ PDE, i.e., saturated-unsaturated flows without free boundaries, are carried out for both 2-D and 3-D regimes in rectangular and hexagonal domains. The Barenblatt and Kalashnikov closed-form analytical solutions in non-capillarity soils are compared with the HYDRUS results. Analytical and numerical solutions match well when soil capillarity is minor. The found distributions of the Darcian velocity, the pore pressure, and total hydraulic heads in the vicinity of the barrier corroborate serious concerns about a high risk to the structural stability of the dam due to seepage. The modeling results are related to a “forensic” review of the recent collapse of the spillway of the Oroville Dam, CA, USA