Concrete placement of Seymareh dam body
In the case of double arch dams either cable cranes or tower cranes with required capacity are commonly used for concrete placement of the dam body. At Seymareh use of cable cranes was hardly possible due to different reasons. These were mainly the regional geology and space limitations for crane runway that could make its installation and commissioning very difficult. Tower crane option was also considered, but the idea soon became aborted due to foreign purchase restrictions.
Then the option of using a conveyor belt system was studied. It was to be used for the first time in large size double arch dams and no previous experience was available on it for projects of Seymareh size. Therefore all stages of design, manufacture, installation and operation of this system were accomplished by Iranian expert and engineers, using domestic capabilities available.
Procedure used in concrete pouring
Considering the height of the dam and the fact that the conveyor belt system should cover all sections of dam body, three systems were used to complete the works. In designing each system problems and limitations encountered in the previous one were reviewed and necessary corrections were made for the next stage.
This system was designed in two phases. First, a top belt which was supported by a lattice-boom crane was used. Later, four fixed conveyor belts with a total length of 100 meters were used to pour concrete over different blocks while the belt at the end was maneuvered by crane. Maximum rate of concreting with this system was recorded at 70 cubic meters per hour.
A 60 meter top belt was designed and manufactured by using two conveyor belts 30 meters each which were jointed together at a point. The system was pivoted to a tower crane standing at the upstream side of the dam foundation. Suitable length of belts and flexibility of the system due to two jointing pivots reduced displacement time to move from one block to another. This further shortened the time of concrete pouring between blocks. Maximum rate of pouring recorded by this system reached 90 cubic meters per hour which led to 50% increase in monthly rate, due to reduction in time between blocks concrete pouring.
Third system was put to work after the height of dam body blocks was increased and tower crane faced height limitations. At this stage a telescopic conveyor belt system was adopted which could rotate 360 degrees horizontal and 60 degrees vertical. Maximum length of belts was 30 meters. These belts were located on pillars fixed on dam blocks and were raised together with raising of blocks. Maximum rate of pouring reached 180cu meters per hour which is a record. Total length of belts used in this system was 420 meters.
At any rate, transport of concrete with conveyor belt can be considered as a new method while using cable or tower cranes. This system with its capabilities, may become a competitor to other presently available ones. Among important advantages of this system include high rate of concrete pouring and no need for international procurement.