|
|
Dam Breach of Eartfill Dams Due to Internal Erosion
Kotaška, Stanislav ; Hodák, Jiří (referee) ; Satrapa, Ladislav (referee) ; Jandora, Jan (advisor)
Dam breaches are relatively rare but can be catastrophic. In the event of a earthfill dam breach, a special flood will occur that can cause loss of life and property. While it is difficult to prevent a earthfill dam breach, it is important to focus on protecting the population. Depending on the type of damage expected to the earthfill dam, different measures are taken to protect people. After analysing possible dam failures and calculating the consequences, risks are assessed and then reduced by relocating people and property. Accurate analysis of potential failures and prediction of the flood wave is necessary to predict how a given special flood will propagate in the floodplain below the dam. The thesis clearly summarises the mechanism of earthfill dam breach due to internal erosion and presents mathematical methods for modelling this phenomenon. The main result is an increase in the predictive capability of the AREBA software used to simulate breaches of earthfill dams due to internal erosion and overtopping. An extension to the AREBA software has been introduced to allow the setting of different levels of comparison plane, consumption curves and reservoir characteristics. In addition, the AREBA software has been extended to include water balance equation and additional methods for dealing with water levels below the dam. New methods have also been added to deal with roof collapse of the seepage pipe, friction losses in the seepage pipe and dealing with the roughness coefficient calculations. A Monte Carlo method with LHS sampling was introduced to generate the input parameters. After applying the proposed improvements, a sensitivity analysis was carried out to identify the most sensitive geotechnical model parameters. In addition, other software’s for simulating the failure of earthfill dams due to internal erosion was presented (EMBREA, DL Breach, WinDAM C) and its results were compared with the modified AREBA software on selected case studies.
|
|
| |
|
| |
|
| |
|
|
Sensitivity Analysis of the Software AREBA for Simulation Dam Breaching Due to Internal Erosion
Kotaška, Stanislav
One of the causes of earth fill dam failure are internal erosion. To simulate these phenomena, a number of software are available to calculate the failure of an earth fill dams due to overtopping or due to internal erosion. For this purpose, software (SW) A Rapid Embankment Breach Analysis (AREBA) was chosen, for which a one-way sensitivity analysis was performed. The paper aims to understand the key geotechnical parameters input to the SW AREBA and their influence on the dam breach hydrogram, the size of the breach and also on the time characteristics. The most sensitive parameters influencing the outputs are the Manning´s roughness coefficient and the erodibility coefficient. These two parameters should be varied by the Monte-Carlo method in the AREBA.
|
|
|
Matematical model of permeability evolution in a fractured porous media due to internal erosion and deposition.
Krajinová, Markéta ; Lanzendörfer, Martin (advisor) ; Zumr, David (referee)
The seepage of fluid through saturated porous media may lead to inner erosion, channelization, preferential flow and transport and deposition of particles. A novel mathematical model was created to describe some of the processes. The model describes a temporal and spatial development of porosity (volume fraction) and permeability (transmissivity) due to erosion and deposition in saturated porous and fractured media. The model calculates the change of permeability and porosity in a direction of different fracture joint sets. The model is based on multi-continua theory, where a region is divided into components (three or more components in this thesis). The components are described by separate differential equations. This approach was used recently by Mahadevan et al. (2012) and Fujisawa et al. (2009) for erosion of porous media. This thesis describes the approaches, assumptions and the equations used in the model. In contrast to the published models, the thesis considers anisotropy. It is characterized by transmissivity tensor (also hydraulic conductivity tensor), which is composed of vectors in the joint sets directions. The model also uses a Dupuit approximation, which allows to approximate flow onto a horizontal plane. The model is also introduced by a numerical simulation using final element...
|
|
| |
guest ::
