Littérature scientifique sur le sujet « TRAPEZOIDAL STEPPED SPILLWAY »

The use of wedge-shaped concrete block overlays to protect embankments subject to flows with relatively high velocities is an idea dating from the late 1960s. Subsequent studies addressed the block stability and design, with or without drainage layer underneath, and the flow characteristics. One aspect still lacking systematic research is the block stability considering the influence of the drainage layer and of the uplift pressure beneath the blocks. The stability of blocks located in the training walls of a trapezoidal cross section has never been investigated, although this type of section is expected when installing a concrete block overlay over embankments. The present study addresses this aspect, using a relatively large facility where the blocks are laid on a drainage layer over an embankment artificially saturated, thus intending to simulate a concrete block spillway installed over a compacted homogeneous earth dam. Data collected both in a trapezoidal flume and in a rectangular flume are is analyzed, together with other authors’ data for this type of stepped overlay. The inherent hydrodynamic stability is verified. Experiments with hydraulic jump formation over the blocks at the end of the flume also showed block stability.

Stepped spillways are a more effective type of spillway in energy dissipation than conventional chute channels. Therefore, the dimensions of the energy breaker at the downstream of the stepped spillways are lower. It is an alternative especially for the downstream pool that cannot be built in sufficient length due to the terrain conditions. In this study, the energy dissipation performance of the trapezoidal stepped spillways was investigated numerically by using Flow3D software. Four different models and three different discharges were utilized for this aim. According to the results, the trapezoidal stepped spillway is more effective up to 30% than classical stepped spillways in energy dissipation. The depth of the trapezoidal step and the bottom base length of the trapezoid significantly affected the energy dissipation rate for the trapezoidal stepped spillway.

The scour downstream spillways can endanger the stability of the dams. Hence, determining the scour depth downstream of spillways was vital importance which scours holes formed around and near the foundations of spillways can endanger the stability of dams and may lead to their failure. So, this paper, investigate the scour downstream contraction stepped spillways. The experimental flume used 16.2 m length, 66 cm width and 65 cm depth. The used number of stepped spillways was 4 Sep, contraction ratio was 60% from flume width and the opening area in breaker 10% from the breaker area on all sides putting in down of breakers. The breaker used above the stepped spillway with different shapes of openings as rectangle, triangle and trapezoidal and different numbers by 2, 4, 6 and 8 of beakers. The divergent angle changes by 45º, 30º, 15ºand 10º. The results were showed that the best numbers of openings is 4openings with rectangle shape because it reduces the scour by 54.51%. In finally to improve this scour by divergent angle lead to the best angle is 10º can minimize the scour is 65.38%.

Abstract To improve the performance of stepped spillways, their combination with labyrinth spillways is an interesting topic. In this study, several labyrinth configurations of stepped spillways were presented. Validation of the numerical model was done using the results of the previous physical models. After that, three configurations including: conventional stepped, trapezoidal-labyrinth, and rectangular-labyrinth were modeled using the OpenFOAM model for the skimming flow regime. For simulation, InterFOAM solver and RNG k–ε turbulence model were used. The results showed an increase of 34.7 and 21.1% in energy dissipation in the trapezoidal and rectangular stepped–labyrinth spillways compared to the conventional stepped type, for dc/h = 1.45 (the range of dc is between 8 and 14.5 cm). The flow velocity in the end step of the trapezoidal- and rectangular-labyrinth configuration is reduced by 50.5 and 31.1%, respectively. Furthermore, in the trapezoidal configuration, a 14.7% reduction in flow velocity has been achieved compared to the rectangular stepped–labyrinth configuration. The results showed that the minimum pressure on the vertical faces of the steps occurred in their upper half and the rectangular configuration has resulted in the highest amount of negative pressure. The turbulence kinetic energy, especially in trapezoidal configuration, has increased toward the downstream.

The stepped spillway of a dam holds significant importance in the field of river engineering and can be utilized in diverse applications. Conducting research on flood control is imperative to examine the mechanism by which energy dissipation occurs across stepped spillways. Numerous research endeavours have been conducted in the past to investigate rectangular stepped spillways without baffles, employing diverse research methodologies. The present research was carried out on a tilting flume in order to compute the energy loss through the trapezoidal stepped spillway at various channel slopes for different baffle arrangements. Additionally, it demonstrates the application of a machine learning method, specifically Support Vector Machine (SVM), for predicting the energy dissipation in terms of nondimensional parameters. The models were constructed using laboratory datasets of an exceptionally high quality, which were gathered from both recent and earlier experiments. The experimental findings suggest that the energy dissipation rises with an increase in the number of baffles from zero to five, and is comparatively greater in channels with zero degree slope as opposed to those with one degree slope. The research has determined that the trapezoidal stepped spillway experiences a twenty percent increase in energy dissipation compared to the rectangular stepped spillway. The statistical indices developed during the experimental research are utilized to validate the suggested models and assess their efficiency and usefulness. The proposed models appear to be influenced by a diverse range of factors, including but not limited to the dimensions of the spillway in terms of width and height, the positioning of the baffle, the upstream and downstream heads, the slope of the channel, the inclination of steps, and the Froude number. A nonlinear relationship has been identified between the aforementioned factors. The results demonstrate that the SVM model proposed, which employs a quadratic kernel function, yields the most accurate predictions for energy dissipation across a trapezoidal stepped spillway. This is evidenced by its superior R2 value and lower RMSE, MSE, and MAE values. The observed phenomenon of overtraining is not exhibited by it. The present research validates the application of machine learning methodologies in this field, and it is noteworthy for its ability to predict energy dissipation across trapezoidal stepped spillways, incorporating diverse baffle designs and configurations.