Sensitivity analysis for dam breach parameters using different approaches for earth-fill dam

The prediction of dams breach geometry crucial in studies of dam breaking. The hydrographs characteristics of flood that resulting from breaking of dam is mainly depend on the geometry of breach and the time formation of breach. Five approaches (Froehlich, Macdonald and Langridge-Monopolis, Von thun & Gillete, USBR and Singh % Snorrason) was used in order to predict dam breach parameters (breach width, breach side slope, breach formation time). The Sensitivity analysis was performed in order to assess the effect of each parameter on the resulting hydrograph of the flood. HEC-RAS model was used to calculate the effect of each parameter on the hydrograph of the flood that resulted. The width of breach (Bavg), side slope (z) and formation time of breach (tf) increased by 25%, 50%, 75% and 100% and decreased by 25%, 50% and 75%, respectively. Flood hydrograph was estimated at the dam site for each case. Sensitivity analysis was performed in order to check the effect of each parameter of breach and time of breaching. Sensitivity analysis was performed with Froehlich method with the mode of overtopping failure and maximum operating level at 107.5 meter above sea level. Result of sensitivity analysis show that peak discharge and time to reach it is adequately sensitive to breach side slope, highly sensitive to the breach formation time and less sensitive to breach width.

A hydrodynamic model of an embankment breaching due to overtopping flow using FLOW-3D

Embankment dam failures are concerning to many people in the society today, including dam engineers, federal, state, and local officials. The effects of dam failure may cause more harm than good; leading to the losses of lives, properties being damage, economic and environmental downfall. Embankment dam breaching is a complex process between hydraulics and soil erosion processes; until today it still requires more researches to be done. Many factors involved in embankment breaching such as cohesiveness of embankment material, compactness of the embankment soil material, height of the dam and slope of the dam. Through the help of simulation techniques such as computational fluid dynamics, it is possible to understand the behaviour of embankment breaching processes. In this research, modelling of embankment breaching with the aid of FLOW-3D allow us to open doors to plenty of experiments to breaching in the near future. This research focuses in analysing and comparing hydrodynamic parameters; breach outflow hydrograph, peak outflow rate Qp and failure time iy, and geometric parameters; breach depth Hb , and top breach width Bt , of the modelling breached embankment for different sediment diameter and inflow rates. Moreover, the research also investigates the velocity magnitude and breach width during the embankment breaching process.

Sensitivity Analysis of Dam Breach Parameters for Variation Capacity Earthen Dams

Sensitivity analysis is an effective tool to determine the robustness of an assessment by examining the extent to which the results are affected by changes in input. In this study, the FAST method was applied to analyse the sensitivity to the earth dam failure process. Four (04) input variables were selected including breach development time, breach width, side slope, and initial breach position. The effects of these parameters on the two (02) outputs i.e., the maximum outflow, and rising time were assessed. The study was applied to 08 reservoirs with different capacities. The sensitivity analysis showed that the development time and initial breach location dominantly affect these outputs. Additionally, development time is the most important factor in rising time. The lateral slope has an insignificant effect on outputs. The effect of breach width can be neglected to rising time, however, its influence on maximum outflow is significant. The results of this study show the role of input variables in the flow hydrograph due to dam failure. Through this research, the workload of the breach parameter analysis process can be substantially reduced.

Laboratory Experiments on Breaching Characteristics of Natural Dams on Sloping Beds

Natural dams formed by landslides may produce disastrous floods after dam outburst. However, studies on the breaching characteristics of natural dams on sloping beds systematically are still at an early stage, and especially the relationship between breach width and depth is still unclear. In this paper, results of a series of laboratory tests that assessed seven different flume bed slope angles are presented. The results show that 3 stages of breaching process of natural dams on different bed slopes were observed. According to the results, headward erosion was the main force for enlargement of breach when bed slope was relatively small. With the increasing of bed slope, the effect of tractive erosion on longitudinal development of breach wass enhanced. The discharge hydrographs were unimodal for all the bed slopes. The peak discharge increased first and then decreased with the increasing of bed slope. The elapsed time from the start of breach formation to the moment of peak discharge decreased with the increasing of bed slope. The difference between different bed slopes was larger when the bed slope was small or large, and the relationship between duration and bed slope had the same characteristics. With the increasing of bed slope, the ratio of breach width to breach depth rose to 1 and then decreased with the increasing of bed slope angle. A result of the present work is a function of the relationship between the breach width and depth for which it is possible to calculate them. This function is based on a shape parameter that linearly decreases with bed slope. The relationship between shape parameter and bed slope was developed to calculate the shape parameter with an additional relationship between shape parameter and mean diameter of particles. Combined with the experimental data and filed data of Tangjiashan natural dam, the shape parameter was calculated, and the function was validated.

The method of assessing the quality of the excavation workmanshift in the underground coal mine

A new method of assessing the quality of the heading workmanship was proposed in this article. The method includes 13 parameters characterizing the quality of excavation performance, namely: the heading breach width, the heading useful height, the heading useful width, the angle of inclination of arch, the horizontal offset of arch (direction), the vertical offset of arch (cancellation), distance between mine roadway support, the arch set overlap length, the tightening torque of clamps screws, development of struts, dadding and the contact of support with rock strata. For each element of the excavation the number of quality points is determined based on by the amount of multiples of the quality statistics QN from the qualifying constant. After adding up the points, the final grade is obtained in the form of the quality category. The conclusion is an example of the evaluation of the quality of heading workmanship according to the developed method.