Geotechnical and structural design considerations for fixed crest weirs
Van-Eckmann, Aaron (2022)
2022
All rights reserved. This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-202204255864
https://urn.fi/URN:NBN:fi:amk-202204255864
Tiivistelmä
The objective of this thesis was to identify and outline structural and geotechnical design considerations for fixed crest weirs. Regional geotechnical properties and climate impediments, due to the geographic location of Finland, were also considered. This thesis was commissioned by Ramboll Finland Oy.
The methodology of this thesis was conducted through data collection and data analysis. Thus, resulting in a compendium of theoretical aspects, that are necessary for the design and for the integrity of the structure.
The results show that weirs constructed from soils are affected by frost heave and that impact of the accumulation of ice build-up against the structure re-quires individual evaluation for each design criteria separately. The design considerations for weirs are sufficient stiffness to prevent settlement, the ground must have adequate capacity to withstand vertical actions, and there must be sufficient sliding resistance to withstand horizontal and inclined actions. The function of the weir is subjected to high destabilising actions, due to the retained water and accumulated sediments, and low stabilising actions, due to the distribution of uplift pressures under the foundations. Therefore, there must be adequate resistance for seepage and hydraulic fracture. Pore water pressure dissipation and creep in soft organic subsoils can cause significant deformations of the weir structure.
Analytical calculations with Eurocode 7 compare the design destabilizing pore water pressure to the design stabilizing vertical stress and compares the design destabilizing seepage force to the design stabilizing submerged weight. Due to local variations in the hydraulic gradient caused by inconsistencies in the soil matrix, relatively high limit states in design are recommended for higher integrity of the weir.
The methodology of this thesis was conducted through data collection and data analysis. Thus, resulting in a compendium of theoretical aspects, that are necessary for the design and for the integrity of the structure.
The results show that weirs constructed from soils are affected by frost heave and that impact of the accumulation of ice build-up against the structure re-quires individual evaluation for each design criteria separately. The design considerations for weirs are sufficient stiffness to prevent settlement, the ground must have adequate capacity to withstand vertical actions, and there must be sufficient sliding resistance to withstand horizontal and inclined actions. The function of the weir is subjected to high destabilising actions, due to the retained water and accumulated sediments, and low stabilising actions, due to the distribution of uplift pressures under the foundations. Therefore, there must be adequate resistance for seepage and hydraulic fracture. Pore water pressure dissipation and creep in soft organic subsoils can cause significant deformations of the weir structure.
Analytical calculations with Eurocode 7 compare the design destabilizing pore water pressure to the design stabilizing vertical stress and compares the design destabilizing seepage force to the design stabilizing submerged weight. Due to local variations in the hydraulic gradient caused by inconsistencies in the soil matrix, relatively high limit states in design are recommended for higher integrity of the weir.