Efficiency of Pressurized Rock Traps for Unlined Hydropower Tunnels

Havrevoll, Ola Haugen; Vereide, Kaspar; Lia, Leif

doi:10.3390/en14144344

Cited by 3 publications

(2 citation statements)

References 20 publications

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“…The observations from inside the sand trap, after dewatering and before emptying of sediments, show that the sediments are separated in grain size and accumulate at mainly two places; (i) a gravel deposition at the upstream end, directly downstream the diffusor and (ii) a sand deposition at the downstream end in front of the weir. Furthermore, sediments were found downstream the sand trap and on the top of the pressure shaft, indicating that sand is transported through the sand trap and into the turbines [18].…”

Section: Prototype Observationsmentioning

confidence: 99%

Retrofitting of Pressurized Sand Traps in Hydropower Plants

Richter

Vereide

Mauko

et al. 2021

Water

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Unlined pressure tunnels in sound rock, combined with pressurized sand traps at the downstream end, allow for low-cost construction of hydropower tunnel systems. This design concept is utilized in hydropower plants across the world. Currently, many such power plants are being upgraded with higher installed capacity, which may result in challenges with the sand trap efficiency. A physical scale model test, accompanied by 3D CFD simulations of a case study pressurized sand trap, has been studied for economic retrofitting. The geometric model scale is 1:36.67 while the velocity scale and sediment scale are 1:1 (same average flow velocity and sediment size in model and prototype). This is currently an uncommon scaling approach but with several advantages, as presented in this paper. Various options for retrofitting were investigated. A combined structure of ramp and ribs was found to significantly improve the sediment trap efficiency. The main novelties from this work are the proposed design of the combined ramp and rib structure. Secondary results include an efficient setup for physical scale models of pressurized sand traps and a methodology that combines the benefits of 3D CFD simulations with physical scale models testing for sand trap engineering and design.

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Section: Prototype Observationsmentioning

confidence: 99%

Retrofitting of Pressurized Sand Traps in Hydropower Plants

Richter

Vereide

Mauko

et al. 2021

Water

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“…With the rapid development of underground engineering construction, the complexity of engineering geological environment is increasing, which poses a more difficult challenge to the stability of engineering rock masses [1,2]. Due to the uneven distribution of natural joints and fissures in rock masses, as well as the fissure water, crack propagation of rock masses threatens the stability of project and even brings huge safety risks to the construction [3,4].…”

Section: Introductionmentioning

confidence: 99%

Study on Influence of Joint Locations and Hydraulic Coupling Actions on Rock Masses’ Failure Process

et al. 2022

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Distribution of joints and fissures under hydraulic coupling condition is particularly critical to the stability of surrounding rock masses in underground engineering construction. In this paper, DDARF (Discontinuous Deformation Analysis for Rock Failure) and RFPA (Rock Failure Process Analysis) are compared and analyzed firstly based on laboratory tests. Then using preferred software RFPA, the failure process, stress state, acoustic emission characteristics and energy dissipation laws of rock masses with different joint locations are analyzed under the hydraulic coupling condition. Results show that a large tensile stress region is generated on both ends of the original joint with the micro-cracks’ propagation, water pressure in cracks promotes the generation of tensile stress to a certain extent, damage effect angle increases gradually from the rock specimen with the middle joint to that with the marginal joint; the same water pressure has a certain auxiliary effect on the main crack failure when the joint is close to the middle part of the specimen, and has a dominant effect on the local crack failure when the joint is far away from the middle; the maximum water pressure shows the “U” shaped distribution. At low initial water pressure, stresses of specimens with symmetrical joint locations have similar evolution trends, while at high initial water pressure, the water pressure in cracks has significant dissipation and thus the maximum water pressure in the system does not exceed the initial value. The length of the main crack path is positively proportional to the number of acoustic emissions and the energy accumulation capacity, and evolution of the damage variable basically shows a development trend of steady growth-rapid growth-steady growth.

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