Renovation of existing dam by enlarging Kasabori Dam

Disaster recovery improvements to reduce flood damage

Renovation of existing dam by enlarging Kasabori Dam

# Public Sector # Japan # Water resources # Flood control # Operation and Maintenance # Dam

Improved dam flood control capacity on a limited schedule

With the Igarashi River in Niigata Prefecture damaged by flooding from heavy rains in July 2011, a three-pronged disaster recovery improvement project was conducted on the river, consisting of: 1) improving the river channel, 2) building a reservoir, and 3) enlarging Kasabori Dam (an existing dam). Given the limited period for budget allocation, the big issue with the disaster recovery improvement project was how quickly dam enlargement for the existing Kasabori Dam could be completed from the initial planning phase.
Kasabori Dam is a concrete gravity dam built in 1964 for the purpose of river training, power generation, and irrigation on the Kasabori River, a right bank tributary of Igarashi River in the Shinano River system. This is the second renovation of the crest gates after a second gate was added in 1979.
In order to ensure that this enlarging project will fulfill the 20% deficiency in flood control capacity, the existing channel crest has been widened from 4 to 6 meters, and the dam height has been raised by 4 meters.

Streamlining construction and evaluating the safety of the enlarged dam geometry

In order to unite the new and existing dam bodies, part of the existing dam body needs to be cut for laying the additional concrete for dam enlargement. The wider the section cut out, the greater this task will impact project feasibility and scheduling. Thus, a distinctive dam geometry was adopted in an effort to reduce costs and schedule time, starting the concrete addition for the Kasabori Dam enlargement from midway up the downstream surface of the dam. The basic geometry was confirmed to be safe using a 2D design method. Since the raised portion of the downstream concrete addition is discontinuous in shape, a finite element analysis was conducted using a 2D section to check for shape-induced stress distribution issues. Given the thickness of the concrete addition, a temperature stress analysis was conducted to study measures for preventing temperature cracking. Also, seismic performance tests were performed on the finished shape using level 2 seismic motion.

*Information as of September 2019.

Project Details

    Project Name :Planning and Design for Renovation of Kasabori Dam
    Client Name : Regional Development Department, Sanjo Regional Development Bureau, Niigata Prefecture, Japan