Parakrama Samudraya and the proposed jogging track
The growing discussion on the above subject among the public including Buddhist priests, environmentalists, farmers, politicians and UDA hierarchy, had so far focused on (1) the possible destruction of our heritage, a proud product of King Parakramabahu the Great, which had lasted for many centuries, for a purpose that does not bring tangible benefits to the people, (2) the need for a jogging track when a few are already available in Polonnaruwa, (3) the priority of the proposal when there are numerous other requirements for the community unfulfilled eg. purified water, accessible rural roads, (4) a solution to the human-elephant conflict, (5) non availability of fertilizer, (6) improvements to the irrigation system throughout and so on, under the present perilous economic status. But no one had expressed the Engineer’s point of view and the stability of this ‘composite’ dam (bund), except by a senior lecturer of a university as published in the ‘Sunday Times’
The purpose of this letter is to elaborate more from an engineering perspective, if the track is constructed. Clearly the existing dam and widened part of the dam for a jogging track in the future, is expected to form a composite dam constituting the old and the new construction which is on the water retaining side of the lake.
No one knows, unless geological investigations are carried out, how this existing dam was constructed, materials that went into it and how the layers of the dam were compacted, composition of the foundation and so on. My guess is that it is formed with lateritic soil and huge boulders brought in by elephants which were filled and compacted.this is a mystery and no one can say exactly the details of it.
Clearly the new section for the track will be constructed using the currently available material and compacted with vibratory rollers on top as well as along the slopes possibly disturbing the old dam well formed. But the degree of compaction and the formation of a monolithic dam can never be achieved, as the older section had been stabilized over several centuries despite the vagaries of the weather patterns.the writer does not agree with some of the arguments that jogging will create vibrations that could affect the bund, as the number of joggers at any one time is small and the rhythm is different.
The most devastating affect will be the differential settlement between the old dam and the new construction due to seepage of rain water, with passage of time, causing the new construction to slide or settle, on to the lake side, not forgetting a reduction of the capacity of the SAMUDRAYA, however marginal it would be.any rectifications at that stage would be enormously costly.the Legendary Engineer late Deshamanaya Dr A.n.s.kulasinghe, with whom the writer had been working with, for decades, would be turning in his grave if he could hear of this stupid move.
These types of proposals are attempted simply due to the fact that State Agencies are managed by people who are only trained to think of alien disciplines like the Military.