Payab Zamzam Group - Drilling Karkheh Dam

More information about Karkheh Dam drilling project is summarized in the followings. You can also go to IWPC karkheh site at www.karkheh.com to obtain more information about the whole dam project as well.

Karkheh Dam

Client: Iranian Water and Power Company (IWPC)

Engineer: Mahab Ghods Company

Contractor: Sepasad Company

Karkheh Dam is the largest dam construction in Iranian history. This is built on Karkheh river, the third largest river in Iran. The specifications of the dam is summarized in the following table:

Type	: Earth- fill, with clay core.
Total volume of embankment	: 32.5^(M.m3).
Crest level	: 234^(m.) m.a.s.l.
Height from the Foundation	: 127^(m.).
Crest length	: 3030^(m.).
Crest width	: 12^(m.).
Maximum width on the foundation	: 1100^(m.).

The main characteristics of the reservoir is shown in

the following table:

Volume at operational level of 220^(m.)	: Apx. 5.4^(B.m3) (before sedimentation).
Operational volume	:3.9^(B.m3)(after sedimentation).
Volume at the minimum operational level of 160^(m.)	: 430^(M.m3).

Considering the size of the dam and its volume, the Spillway of Karkheh Dam has been designed based on the reliable discharge of probable maximum flood , considering suitable free – board. The following table summarizes these specifications. The drilling operation of this company was located at the spillway structure, a huge concrete body which you can see in the next picture.

Type

: gated.

Location	: right bank.
Discharge capacity	: 18260^(m3/s)-(at PMF).
Total length	: 1118^(m)(including the lengths of stilling basin & outlet channel).
Width	: 110^(m) (excluding the middle piers, with the width of 90^(m.)).
Stilling basin length	: 164^(m).
Stilling basin width	: 110^(m).
Design head on ogee crest	: 17^(m).
Crest level of the ogee	: 209^(m) m.a.s.l.
Excavation volume	: 5.5^(M.m3).
Concrete volume	: 758000^(M.m3).

Two close ups of the drilling location are shown in the following pictures.

The gates of the spillways are anchored to the concrete body using high capacity tendons as in the picture.

The design for the reinforcement was reconsidered later requiring more tendons to be installed in the pillars. This necessitated drilling of very accurate holes without any deviations with 146 mm in diameter for the extra tendons.

Drilling had to be performed in the reinforced concrete with large diameter (146mm). To investigate on the number of reinforcing bars that will be cut during drilling, the operation was performed with coring.

During the operation, at many locations the bit had to cut through the steel rebars. These included both transversal as well as longitudinal ones. The later ones were very hard to cut, keeping in mind the very low permitted deviations. removing the cores with these longitudinal rebars was a difficult task in this project.

To keep the deviation to within its permitted limit, a total station was utilized in all the stages of operations, including the setup of the drilling rigs, alignment of the spindel and drilling operations.

All these tasks were performed from a limited space on the platforms erected at the site on the piers.

The work was finished on February of 2003 and the holes were washed clean and were handed over to the next team for further tendon installations. All these were made possible through expert of the engineers and dedication of the site workers.