The Karun III replacement road passes across the catchment area of three large rivers- Karun, Zahreh & Jarahi. The catchment area exceeds 111203 km2, which is equal to 17 percent of the whole area of the country. The total average annual inflow of these rivers is 22321 m3. The Karun River originates from the upper elevations of Mount Zardkoh-e-Bakhtiari in the Zagross sierra. This 950km-Long River is the longest and the largest river in Iran.
Considering the great elevation difference between the highest point of the Karun River catchment area (Dena summit) and its lowest point (Khuzestan plain) and having the length of the catchment area in view, there have been opportunities to construct several dams across the river, not only to store water but also to utilize its power potential. For this purpose Karun I, Karun II, Karun III, Karun IV, Karun V, Bazoft, Masjed-I-Soleyman & Gotvand dams have been considered to be constructed across the river, some of which are currently in operation. The main objectives of construction of these dams have been to meet a part of the national power demand as well as to regulate the water and control ruinous floods. As the impounding of the reservoir of the KIII dam begins, a portion of the Ahawaz-Shahrekord road connecting Khuzestan province to Chaharmahal-o-Bakhtiari province will be submerged by the reservoir. This necessitates constructing a substitute road in order to keep the two provinces connected during the impounding. Therefore, a replacement road was designed at an elevation higher than the reservoir. The replacement road is located in the Karun River catchments area.
The dam is 205.3 meters high. Its reservoir, which has the capacity to store 3x 109 cubic meters of water, is 48 km2 in area and 60 km long. From a topographical view, the replacement road is located in a mountainous region and has a steep slope in most of directions especially toward minor rivers. Hence, it has been a challenging assignment to construct access ways to build trenches, tunnels and piers of the bridges.
The current Shahrekord-Izeh-Ahwaz road, which is considered as a new road, came in use early in 1996. The Karun III replacement road is a main road that its asphalt roadway is 11.00 meters wide. Having taken aerial photographs and reviewed different choices, the best choice was selected in accordance with the standards and specifications. Afterward, the plan of the road was prepared applying standard geometric specifications. In the selected choice, which is 7377 meters long, two large bridges, three tunnels and twenty culverts were considered in order to construct the shortest road. After studies and necessary reviews, a contractor who could cope with such a challenging project, with its especial complexities, was employed. The project, which included two parts, civil and steel bridges, began in late September 2001.
A main contractor undertook construction of the substitute road, tunnels, technical structures, and piers of the bridges.
One of the biggest manufacturers of steel structures in the country was appointed to construct the two huge steel bridges. The manufacturer undertook to erect the bridges and put them in readiness within 2.5 years.
These bridges can be compared with Varsak Bridge in Mazandaran province and Ghatur Bridge in Azarbayejan province, both of which are presently in use.
Varsak Bridge was constructed on Tehran- Gorgan railway over the Varsak River in Savadkoh city. It was called Victory Bridge because of playing an important role in the Allies’ conquest in World War II. The bridge is 110 meters high and its arch is 66 meters in length, structure of which was constructed using prefabricated concrete slabs.
Ghatur steel bridge came in use on the west railway in 1965. Its arch segments were manufactured in the United States and an American-French company transported these segments to Iran and erected them. The bridge is 128 meters high and the radius of its arch is 232 meters.
Obviously, it would not be possible to design, manufacture and erect the large Karun Bridges unless the most experienced specialists of the country in all fields were engaged. Therefore, the project was based on a good liaison among all groups in order to accomplish the task.
Design stages of the bridge started expeditiously in the second half of the year 2001 as soon as the preparation of materials and site mobilization began. For this purpose, more than 20 experienced engineers carefully carried out the design and prepared the shop drawings.
The first large bridge, which is composed of 890 main segments, weighs more than 2500 tons. The main load bearing structure of the bridge is a 9m-high arch truss. The arch span of the bridge is 264 meters long and 42 meters high. The bridge deck is 336 meters long with four reinforced concrete piers, the highest of which is more than 35 meters. In order to guarantee the safety aspect of the work during the erection and operation, front and back piers as well as upper and lower arch spring lines have been tied to the rock with some cables.
The steel materials used in the bridge structure are of a special weather resistant type. To install the steel segments two cranes with a unique design were utilized.
The great importance of the bridges and the high concern of the executives as well as the fact that it was the first time such a large bridge was going to be erected in the country, required supervision and consultation of a foreign bridge-constructor company during the erection. Conveniently, all stages of design and erection were reviewed and approved by the company.
This attainment was a confirmation of the great scientific leap of Iranian specialists in this field. One dares to say that there is now the possibility to design and construct special bridges in the country as their knowledge is extended beyond the current borderlines.
Being located on a steep valley, the second large bridge is not less complicated to be erected than the first one, although its span is shorter (162m). The bridge weighs 1500 metric tons. Experience attained during the erection of the first bridge offers hope of achieving a noticeable record in erecting such bridges.
All those who have had a hand in the project hope that can effectively step toward the progress of this scientific/executive branch besides fulfilling the construction plan and connecting a part of the country’s road network.
Note that the Ahwaz-Shahrekord main road, which is a part of the whole transportation system of the country, is of great importance from economic, strategic and tourism points of view. Not only is this a connecting road between Isfahan/Chahar-o-Bakhtiari provinces and Khuzestan porvince, but also the route in question is the access way to the important under-construction Karun dams. After construction of the aforesaid dams, with emergence of several lakes, beautiful landscapes and attractive flora and fauna, the region will change to one with tourism interests as well. Especially, after the impounding of the Karun III dam with the lake behind it and the two large bridges amid three tunnels, an amazing landscape will come to exist.