PROCESS
Among the dams, the arch dam has a structure in which the water pressure of the reservoir is transmitted to the foundation of bedrock on the riverbed and both banks through the dam body, and the dam body is supported by the bedrock.
As a measure to ensure the stability of the bedrock that supports the arch-type concrete dam, bedrock PS anchors (* 1) are inserted into the bedrock and tightened to reinforce it, thereby integrating the foundation bedrock.
* 1 PS anchor (Prestressed anchor)
A structure that suppresses and reinforces external forces such as earthquakes by applying a compressive force to structures.
einforcing the bedrock that supports the arch-type concrete dam with PS anchors
Image of bedrock reinforcement after installing multiple PS anchors. (Plan)
Construction process of bedrock PS anchor (image of bedrock surface and inner part)
Create a concrete block pressure plate at the anchor installation location on the bedrock surface
To install an anchor into the bedrock a drilling machine is used to dig a hole.
Assemble the anchor on stage
Glossary
・Fixation length section: Grouting (*2) section that transmits the tensile load due to the tension of the anchor to the surrounding bedrock.
・Free-length section: It does not adhere to the surrounding ground or grout when the anchor is tensioned.
・Packer: A member for reliably injecting grout into the anchorage area.
・Centralizer: A component to hold the tendon (*3) in the center of the anchor hole.
・Spacer: A component to keep the spacing of PC steel stranded wire constant.
・Anti-corrosion coated PC steel stranded wire: Tensile material covered with coating material
・Pressure receiving plate: A structure installed to transmit the tensile force of the anchor.
・Rust prevention cap: A cover for protecting PC steel stranded wire from corrosion
*2 Grouting is an injection that fills a gap. Cement milk is generally used in anchor work.
*3 Anchor body assembled from PC steel wires and PC steel stranded wires.
Install an anchor into the drilled bedrock
After inserting the anchor, grout such as cement milk is injected to fix the fixing length, which is the tip of the anchor, to the bedrock.
Once the grout on the fixing length has hardened, pull the anchor with a hydraulic jack and fix it.
Then, grout is applied to the free length.
Install and complete the anti-corrosion cap on the pressure plate.
Example of bedrock PS anchor: Go to the Kawamata Dam reinforcement work 
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