Construction concept of Kallanai Dam (Grand Anicut)

         

       The Kallanai Dam was “[built] during the second century AD by Karikalan, a king of southern India's old Chola Dynasty” and “is also one of the oldest irrigation systems in the world that is still in use” (Agoramoorthy and Hsu, 2008). “The purpose of the dam was to divert the waters of the Kaveri across the fertile Thanjavur delta region for irrigation via canals. Since the English arrived in the eighteenth century, the Kallanai has been tampered with and other hydraulic structures have been added nearby. It is therefore difficult to extrapolate from the current situation into the past to understand the workings of the anicut” (Bijker, 2007). Approximate Year of Completion 200 AD.The exact location of the Kallanai is in the Trichy District.

Construction details

                         

                     

                               Besides attracting a large number of tourists, the dam has fascinated historians and engineering experts. Though much has been said time and again about Grand Anicut, not many know the great contribution made by king Karikalan to promote irrigation in the delta region.In this context, Chief Minister Jayalalithaa sprang a surprise recently by announcing her government’s intention to build a befitting memorial to the Chola king.

                               Grand Anicut is a massive structure constructed with uneven stones to a length of 329 metres and a width of 20 metres across the main stream of the river.It is a unique structure built just with large boulders brought over and sunk in the Cauvery sand, a task arising of a desperate need for irrigating fertile fields downstream when the floods breached the left bank and rushed down north to rejoin the Coleroon, leaving its delta high and dry.                                                                                                                The dam was meant to divert water across the fertile delta region for irrigation through canals.The main function of this dam was to retain the supply in the Cauvery and its branches and pass on the surplus into Coleroon through the Ullar river.The dam is seen as a model for engineers across the world. Sir Arthur Cotton’s 19th century dam across the river Coleroon (Kollidam), the major tributary of Cauvery, is stated to be a replication.It is a sad reality that when the British took over Thanjavur from the Mahrattas in 1800, irrigation work was neglected but the supply realised in the Cauvery was inadequate.

Construction Technique

                                   The dam was first build in Rocks  then,  later it was repair and reconstruct by concrete in british period. The following are the process of construction of dam.

Rock cutting

 The main material of this dam is Rocks. 

These rocks are cut down by following process.

• Punching hole 
• Inserting Wooden Wedge 
• Adding Water
• Breaking

Placing of Rock

                                 The Rocks are directly placed in the  path of the River Cauvery. The stones are placed in their respected places.External Thrust or push is required to maintain stability to stones.We Can't able Push the stones in the high speed water.  so, they followed simple method to immerse the stone into river by loading and erosion process. One Stone is placed in Bottom and another stone is placed in top of it.By erosion it will placed in correct position.

                   Simply this method is explained by waves in beach.when we place our legs in the sea shore.The waves will  carry over the sand particle on side of our legs.due to this our legs are immersed into sand on sea shore.This is the principle of the stone placing.Due to this the basement of the Dam is made up of Sand Bed.

                     By this method the Dam was Build in the River Cauvery. The sand bed give Great Strength and Durability to the structure. This will shows the work and knowledge of our Ancestors.