Construction process

PROCESS.1

Preparation work

Before the start of construction, a ground survey is conducted as preparatory work to check for any discrepancies between the design and the actual site.

Temporary cofferdam (diversion)

To build a dam body, the river stream is changed temporarily. A “temporary drainage channel” for diverting river water, an “upstream temporary cofferdam” to intercept the river, and a “downstream temporary cofferdam” to prevent the backflow of water are built.

Environmental conservation

The impact on the surrounding environment caused by dam construction is reduced.
We are also tackling environmental conservation in the construction of the Kawakami Dam, which is currently under construction.

(Link to Japan Water Agency Kawakami Dam website.)

Japanese giant salamander
Scarce birds of prey
Plants

PROCESS.2

Foundation excavation work

Foundation excavation work of dam body

To construct the dam on firm bedrock, excavate soil and sand and weak bedrock to expose the firm bedrock.

Foundation Treatment Works

To increase the strength and water tightness of the foundation ground of the dam, the foundation bedrock is filled with cement milk.

PROCESS.3

Dam concrete placing works

Construction equipment work

The tower cranes, concrete batching plant, and belt conveyors for material transportation, necessary to construct the dam body, are installed.

Concrete placing works

Concrete is placed for the dam body. There are two types of casting methods: the “columnar block method,” where each block is stepped and divided into pillars, and the “RCD method” and “extended layer method,” where the blocks are placed without creating a height difference.

Safety management at the construction site

Obayashi Corporation uses the latest technology to focus on the safety management of people working on-site.

PROCESS.3

Embankment work for dam body

Material transportation

Roller compaction

α system (embankment construction, quality control)

PROCESS.4

Completion・maintenance

Trial filling

After the dam is completed, water is stored to check if there are any problems, and the safety of the dam is confirmed.

Maintenance managment

After the completion of the dam, maintenance to achieve the objectives such as flood control, water utilization, normal function maintenance of running water, and keeping functionality over the long term is conducted.