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Rock Scour Model for Unlined Plunge Pools and Stilling Basins
https://orcid.org/0000-0001-9704-4744
https://orcid.org/0000-0002-9139-2366
Abstract This paper presents a new scour model (SM) that is able to evaluate the rock scour development, shape, ultimate depth and probability of occurrence. The model takes into account two main scour mechanisms: (1) the maximum rock crack extension that mainly depends on the geology, rock characteristics/mechanics and hydraulic fracturing analysis; and (2) the isolated rock block stability that depends on the flow hydraulics and rock block dimensions. The former defines the ultimate extent of the fractured area in a rock matrix where the isolated rock blocks can be detected; only in this area, the rock block stability analysis can be performed afterwards. The isolated rock block stability has been studied in the literature; on the contrary, the information related to the rock crack propagation in dissipaters is limited, which is investigated in this paper. Here, the expected maximum rock crack extension is defined by a threshold on the stress intensity factor. The rock stress intensity factor is investigated via stochastic approaches, compatible with the stochastic nature of the turbulent bottom pressure field, with the support of physical hydraulic modelling results. The proposed SM is a physically based model that couples the hydraulics and geological aspects of scour phenomena, allowing a realistic evaluation of the rock scour. This is drawn out by the comparison between the maximum scour depth computed via the rock block stability analysis and the maximum depth of rock matrix fractured area where the isolated rock blocks can be formed by the incident flow; the smallest depth gives the expected scour. The ultimate scour could be significantly smaller than the one computed via the approaches in the literature, especially for compact rocks suitable for unlined dissipaters. This highlights the relevance of this study that takes into account the high-velocity flow characteristics such as aeration and turbulence effects as well as the main geomechanical characteristics of the whole rock mass obtained by geological surveys. Furthermore, the SM stochastic approach makes it suitable in the risk-based design of dams, hydropower outlet works and other hydraulic structures as well as dam stability assessment. The model is validated using well-known real-life scour cases in the literature such as Wivenhoe and Cabora Bassa dams. A design example is included in the paper demonstrating the evaluation of the rock scour downstream of a large dam.
Highlights The paper presents a novel probabilistic rock scour model applicable to hydraulic structures.The model is able to evaluate the rock scour development, ultimate depth and probability of occurrence in unlined dissipaters.This physically-based model couples the hydraulics and geological aspects of scour phenomena allowing a realistic evaluation of the rock scour.The model is suitable for the risk-based design of dams, hydropower outlet works and other hydraulic structures as well as dam stability assessment.The model is validated using knowing real-life scour cases in the literature such as Wivenhoe and Cabora Bassa dams.
Rock Scour Model for Unlined Plunge Pools and Stilling Basins
https://orcid.org/0000-0001-9704-4744
https://orcid.org/0000-0002-9139-2366
Abstract This paper presents a new scour model (SM) that is able to evaluate the rock scour development, shape, ultimate depth and probability of occurrence. The model takes into account two main scour mechanisms: (1) the maximum rock crack extension that mainly depends on the geology, rock characteristics/mechanics and hydraulic fracturing analysis; and (2) the isolated rock block stability that depends on the flow hydraulics and rock block dimensions. The former defines the ultimate extent of the fractured area in a rock matrix where the isolated rock blocks can be detected; only in this area, the rock block stability analysis can be performed afterwards. The isolated rock block stability has been studied in the literature; on the contrary, the information related to the rock crack propagation in dissipaters is limited, which is investigated in this paper. Here, the expected maximum rock crack extension is defined by a threshold on the stress intensity factor. The rock stress intensity factor is investigated via stochastic approaches, compatible with the stochastic nature of the turbulent bottom pressure field, with the support of physical hydraulic modelling results. The proposed SM is a physically based model that couples the hydraulics and geological aspects of scour phenomena, allowing a realistic evaluation of the rock scour. This is drawn out by the comparison between the maximum scour depth computed via the rock block stability analysis and the maximum depth of rock matrix fractured area where the isolated rock blocks can be formed by the incident flow; the smallest depth gives the expected scour. The ultimate scour could be significantly smaller than the one computed via the approaches in the literature, especially for compact rocks suitable for unlined dissipaters. This highlights the relevance of this study that takes into account the high-velocity flow characteristics such as aeration and turbulence effects as well as the main geomechanical characteristics of the whole rock mass obtained by geological surveys. Furthermore, the SM stochastic approach makes it suitable in the risk-based design of dams, hydropower outlet works and other hydraulic structures as well as dam stability assessment. The model is validated using well-known real-life scour cases in the literature such as Wivenhoe and Cabora Bassa dams. A design example is included in the paper demonstrating the evaluation of the rock scour downstream of a large dam.
Highlights The paper presents a novel probabilistic rock scour model applicable to hydraulic structures.The model is able to evaluate the rock scour development, ultimate depth and probability of occurrence in unlined dissipaters.This physically-based model couples the hydraulics and geological aspects of scour phenomena allowing a realistic evaluation of the rock scour.The model is suitable for the risk-based design of dams, hydropower outlet works and other hydraulic structures as well as dam stability assessment.The model is validated using knowing real-life scour cases in the literature such as Wivenhoe and Cabora Bassa dams.
Rock Scour Model for Unlined Plunge Pools and Stilling Basins
https://orcid.org/0000-0001-9704-4744
https://orcid.org/0000-0002-9139-2366
Abstract This paper presents a new scour model (SM) that is able to evaluate the rock scour development, shape, ultimate depth and probability of occurrence. The model takes into account two main scour mechanisms: (1) the maximum rock crack extension that mainly depends on the geology, rock characteristics/mechanics and hydraulic fracturing analysis; and (2) the isolated rock block stability that depends on the flow hydraulics and rock block dimensions. The former defines the ultimate extent of the fractured area in a rock matrix where the isolated rock blocks can be detected; only in this area, the rock block stability analysis can be performed afterwards. The isolated rock block stability has been studied in the literature; on the contrary, the information related to the rock crack propagation in dissipaters is limited, which is investigated in this paper. Here, the expected maximum rock crack extension is defined by a threshold on the stress intensity factor. The rock stress intensity factor is investigated via stochastic approaches, compatible with the stochastic nature of the turbulent bottom pressure field, with the support of physical hydraulic modelling results. The proposed SM is a physically based model that couples the hydraulics and geological aspects of scour phenomena, allowing a realistic evaluation of the rock scour. This is drawn out by the comparison between the maximum scour depth computed via the rock block stability analysis and the maximum depth of rock matrix fractured area where the isolated rock blocks can be formed by the incident flow; the smallest depth gives the expected scour. The ultimate scour could be significantly smaller than the one computed via the approaches in the literature, especially for compact rocks suitable for unlined dissipaters. This highlights the relevance of this study that takes into account the high-velocity flow characteristics such as aeration and turbulence effects as well as the main geomechanical characteristics of the whole rock mass obtained by geological surveys. Furthermore, the SM stochastic approach makes it suitable in the risk-based design of dams, hydropower outlet works and other hydraulic structures as well as dam stability assessment. The model is validated using well-known real-life scour cases in the literature such as Wivenhoe and Cabora Bassa dams. A design example is included in the paper demonstrating the evaluation of the rock scour downstream of a large dam.
Highlights The paper presents a novel probabilistic rock scour model applicable to hydraulic structures.The model is able to evaluate the rock scour development, ultimate depth and probability of occurrence in unlined dissipaters.This physically-based model couples the hydraulics and geological aspects of scour phenomena allowing a realistic evaluation of the rock scour.The model is suitable for the risk-based design of dams, hydropower outlet works and other hydraulic structures as well as dam stability assessment.The model is validated using knowing real-life scour cases in the literature such as Wivenhoe and Cabora Bassa dams.
Rock Scour Model for Unlined Plunge Pools and Stilling Basins
Maleki, Shayan (author) / Fiorotto, Virgilio (author)
2022
Article (Journal)
Electronic Resource
English
BKL:
38.58
Geomechanik
/
56.20
Ingenieurgeologie, Bodenmechanik
/
38.58$jGeomechanik
/
56.20$jIngenieurgeologie$jBodenmechanik
RVK:
ELIB41
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