Abstract
Dam spillways permit the release of excess water from reservoirs; however, these structures can experience erosion during these releases, causing damage to dam infrastructure. To study rock mass erodibility in this context, a scaled physical model of an unlined open-channel flow spillway is built. The set-up used allows studying multiple parameters influencing rock mass erosion, such as joint orientation, joint opening, block protrusion, joint roughness, and block shape and size. The model also permits varying hydraulic parameters, including channel roughness, flow velocity, and flow turbulence. Using this model, it was evaluated how joint opening and surface protrusion (height and configuration) affect hydraulic parameters both on the block surface and inside rock joints responsible for rock block uplift. Dynamic pressure in the joints varied less than on the block top, with less variability as joint opening size decreased. The force acting on the block top, i.e. on the channel surface, was the main force influencing block uplift, and its effectiveness was affected by protrusion configuration, protrusion height, and joint opening. The uplift force under the block, induced mainly by static pressure, remained constant regardless of protrusion configuration and joint opening. However, the block geometry used may have induced less dynamic pressure under the block. Therefore, block geometry may alter the relative effects of protrusion and joint opening on uplift pressure. Future studies should evaluate how block shape affects the role of both parameters on rock mass erodibility.
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Source: Modified from Koulibaly et al. [9]
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Data availability
The data sets generated and analysed during the current study are available from the corresponding author on reasonable request.
Abbreviations
- \({A}_{\mathrm{A}}\) :
-
Surface top area of the block
- \({A}_{\mathrm{B}}\) :
-
Surface bottom area of the block
- \({A}_{\mathrm{L}}\) :
-
Surface lateral area of the block
- \({A}_{\mathrm{f}}\) :
-
Surface area offering frictional resistance
- \({F}_{A}\) :
-
Force acting on the top face of the block
- \({F}_{\mathrm{B}}\) :
-
Force acting on the bottom face of the block
- \({F}_{C}\) :
-
Force acting on the lateral face “C” of the block
- \({F}_{D}\) :
-
Force acting on the lateral face “D” of the block
- \({F}_{\mathrm{down}}\) :
-
Force acting towards the downward direction
- \({F}_{E}\) :
-
Force acting on the lateral face “E” of the block
- \({F}_{F}\) :
-
Force acting on the lateral face “F” of the block
- \({F}_{\mathrm{f}}\) :
-
Friction force
- \({F}_{\mathrm{up}}\) :
-
Force acting towards the upward direction
- \({\gamma }_{\mathrm{w}}\) :
-
Unit weight of water
- \(g\) :
-
Gravitational acceleration
- \({G}_{\mathrm{b}, \mathrm{down}}\) :
-
Block weight in the downward direction
- \({G}_{\mathrm{b},\mathrm{n}}\) :
-
Block weight in the normal direction in relation with the block’s lateral faces
- \(h\) :
-
Block height
- \(\varphi\) :
-
Friction angle
- \({P}_{A}\) :
-
Total pressure acting on face “A” of the block
- \({P}_{A, \mathrm{stat}}\) :
-
Static pressure acting on face “A” of the block
- \({P}_{A,\mathrm{dyn}}\) :
-
Dynamic pressure acting on face “A” of the block
- \({P}_{B}\) :
-
Total pressure acting on face “B” of the block
- \({P}_{B,\mathrm{dyn}}\) :
-
Dynamic pressure acting on face “B” of the block
- \({P}_{B,\mathrm{stat}}\) :
-
Static pressure acting on face “B” of the block
- \({v}_{A}\) :
-
Flow velocity measured on face “A” of the block
- \({v}_{B}\) :
-
Flow velocity measured on face “B” of the block
- \(y\) :
-
Water height above the channel
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Acknowledgements
The authors would like to thank the research group R2Eau for their helpful comments and suggestions and the Natural Sciences and Engineering Research Council of Canada (NSERC) (#CRDPJ 537350–18), Hydro-Québec, Mitacs Inc. (# IT22640), and Uniper for research funding.
Funding
This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) (#CRDPJ 537350–18), Hydro-Québec, Mitacs Inc. (# IT22640), and Uniper.
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AS contributed to conceptualization, resources, validation, and project administration; AS and M-HW contributed to methodology; M-HW contributed to formal analysis and investigation, visualization, and writing–original draft and preparation; AS, MQ, C-ON, and M-HW contributed to writing–review and editing; AS, MQ, and C-ON contributed to funding acquisition; and AS and MQ contributed to supervision.
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Wisse, MH., Saeidi, A., Quirion, M. et al. Effects of joint opening and block protrusion on the hydraulic parameters affecting rock block erosion in unlined spillways using a reduced-scale model. Acta Geotech. 19, 1965–1979 (2024). https://doi.org/10.1007/s11440-023-02085-y
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DOI: https://doi.org/10.1007/s11440-023-02085-y