Idukki dam's 'movement of crust' to be studied
text_fields
Thodupuzha: Idukki dam has been found to show defective 'movement of crust'. When the water level rises, the dam normally should expand and return to normal when the water level comes down.
As per engineering principles, when the dam reaches its full capacity, there must be a movement of crust from 20 to 40 millimetres. However, it has been found that this movement occurs only in the 'upstream' and not in the 'downstream'. This is against the design principle of the arch dam.
It has been pointed out that the movement of crust not occurring in a ratio as directed by the architecture is a serious issue. It is learnt that KSEB research department submitted a report the other day that the 'movement of crust' defects in the arch dam, which is the vital part of Idukki project, is a cause of concern.
A confidential report, but not one indicating urgent risks, highlights that the long-term scenario has to be subjected to study.
The 'movement of crust' was accurate until 1994-95. Idukki dam was designed by Surveyer Triniger Shanivertasche (SNC), a Canadian company. It is Asia's largest concrete arch dam and the second in the world.
Arch dams have better strength to resist pressure. the high pressure building up in the dams when the water level goes up, will be equally towards the sides and downward in the case of arch dams. This is the strength of arch dams. The pressure of Idukki dam, which is built connecting Kuavan-Kurathi hills, is borne by these natural hills. In the case of other dams (gravity dam) the pressure will be only vertically downward.
In the case of earth dams also this is the case. Two other dams, Cheruthoni and Kulamav of the Idukki project, which is a combination of three dams, are gravity dams.
The arch model is used in the design of Idukki dam, which stands above the others in size, with the objective of keeping it safe and strong and with technical perfection. The prsence of two very strong hills was also factored in.
Water in the Idukki project's reservoir is spread over an area of 60 square kilometres.