The chief priest of the Tissamaharama temple had pointed out to the head of the State on one of his inspections in 1993 that the Tissa Maha stupa had developed series of vertical cracks right round the dome of the stupa. According to him, the phenomena had started around 10 years before and was attributed the vibration caused by heavy lorries boulders to Kirinda down a road adjacent to the stupa. The author was requested to inspect the stupa immediately and submit a report. Accordingly an inspection was carried out by the SEC and a report was submitted to the Department of Archaeology on 22nd June 1993. According to this report there were ten large structural cracks which were almost vertical and were evenly distributed around the dome. Each crack had the widest separation at the middle of the dome, (where one could insert a clenched fist ), and appeared to spread towards the top square (Hatareskotuwa) and towards the basal terraces (Pesawas). The structural integrity of the stupa was definitely impaired and was beyond restoration to its original condition except through removal of the separated section and re building. It was also evident that one could not predict when there would be a catastrophic collapse not unlink the one occurred at Mirisavetiya.Ttssamaharama Maha Stupa (Mahanaga stupa?), had been restored fully 1900 with public donation. No records were available of the construction work, (except that the total cost of reconstruction was Rs. 19,000/=), nor how the ruins looked like before restoration works. In fact, little information is available as to the period of original construction of four stupas found today at Tissa, the ancient Magama. (The stupas being Mahanaga, Yatala, Sandagiri and Menik Stupas ). The Mahanaga or the Tissamaharama stupa was probably built in early second half of the third century BC by king Mahanaga (the first king of Mahanaga ), or by King Kavanthissa in first half of the second century BC. It appears that no restoration work was done on this stupa till the last half of the 19th century (1857-1900), after the last rifling of this stupa by King Magha(1215-1236 AD).
In early 1994, the Director General of Archaeology requested the SEC to submit proposal for the prevention of a catastrophic failure of the stupa, which was imminent. The proposal made by the SEC consisted of embedding horizontal reinforced concrete rings, nine in number, placed just below the surface of the dome, suitably spaced between the Pesawa and the Hatareskotuwa. This proposal was submitted after computer assisted structural analysis by our engineers using available data (the quality of the surface bricks), and was carried out with the help of the civil engineering department of the university of Paradeniya. This proposal was accepted and the SEC started work on the first ring at the top most part of the stupa on 14th june 1995.
To construct the RC ring beams in the dome, bricks on the surface of dome of dome had to be removed to a depth of about one foot and to a width of about a foot for each of the ring beams. Whist constructing the first beams , we noticed that the original cracks had developed further since the first inspection and also the number of cracks had also gone up to 16 from the initial 10 The Hareskotuwa also showed cracks at certain places. It was evident that any tampering with the existing dome such as construction of trenches to embed the RC ring would further weaken the structure, especially the trenches which would have to be made on the vertical part of the dome. Two internationally reputed conservation engineering experts, (Mr.Alan Baxter and Professor Crochi ) were consulted by the Dept. of Archaeology and they too expressed concern about removal of any brick work from the stupa dome. Therefore, it was decided to stop embedding RC rings after the top most beams, and seek further proposal from the local engineering organizations for a suitable method that does not involve further weakening of the structure even temporarily during application of preventive measures.
Author - Gamunu Silva
asa
2008/04/06
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