tNCINI'.r.K • Vol. XXXX, No. 03, pp. 41-52, 20076 The Institution of Engineers, Sri Lanka

Conservation of Ancient Dagobas in Sri Lanka.W. N. G. Silva

Almliiirt: This paper relates a description of the conservation and restoration works carried out onli t s tupas (dagobas) of Sri Lanka during the past two centuries. The main focus is on the

, i | > l < l i < . i i m t i ol' engineering techniques while heeding archaeological requirements, in attending to thesenirt*»l vr masonry edifices, during the latter part of the 20th century. The Post-restorational failure of theMlrlntW'tiya Stupa is taken as an example to highlight causes of failure, and how this event coupledWith rtivh.ti'logical requirements led to the shift from complete restoration to conservation of othermajor n| upas such as Jethwanaramaya and Abhayagiriya, is described. Further, application of moderntinginrcring techniques used in circumventing imminent failure of earlier restored stupas such asH»«rtinnharamaya is described.

Keywords: Conservation, Restoration, Ancient Monuments, Dagoba

Hrl Lanka is a country rich in ancient religioustuimonts. It has four world heritageMi imrn t sites, the same number as it's much

Nggrr neighbour, India. Since Buddhismi •• • ,11 m- Hit- state religion of the country duringKing Hovanampiyatissa's time (3rd century BC),various Sinhala kings up to the time of the lasttilnhril.i k ing (19th Century), have builtM" .Master ies , temples etc. which included1 ' i M i m r i l y Dagobas or Stupas (basically11' miNphcrical brick edifices for enshrinement ofi n i l ' i i i i M l relics of the Buddha or of Disciples•ml noun-times to mark sacred spots), shrinerooms with colossal statues of the Buddha (bothItt monolithic stone or stucco), and single andMUltlltory buildings which were part ofmonastery complexes (sometimes housing asn u n h HN 5000 resident monks as in Abhayagirimonastery). Some of these Dagobas are• ••mpnrab lc in size to the Great Pyramids of

i. a iul some date back almost two millennia.

During the colonial era, the English rulers took• great interest in these ancient monuments.Wi th tin- formation of the Department ofArvluit'nlogy, foundations were laid for theroinrrvalion of these monuments. Most siteshave bt'i'ii surveyed, recorded, and declared asAM hrtt-ological sites. Few attempts were madeduring the latter half of the 19th century to

. r ive some of the dagobas in the ancientt IIU's of Auradhapura and Polonnaruwa. Thehinl comprehensive record of the ancient stupasWfl» otrried out by Mr. J. G. Smithers, in 1894.

< niist-rvation, restoration or reconstruction ofaiu it-tit stupas had been carried out by various

Ruwanveli Mahaseya - Before restoration

Sinhala kings, during the history of the Sinhalakingdom. However, conservation works duringthe colonial era probably commenced during thelast decade of the 19th century when the Englishattempted the restoration of Mirisavetiya, andconservation of Abhayagiri, and Jetavanastupas during the time of the ArchaeologicalCommissioner, Bell. With the Buddhist revivalwhich came in the latter half of the 19th century,different religious organizations undertookrestoration works of many historicallyimportant stupas such as Ruwanveliseya atAnuradhapura, Tissa Maha Stupa at Ruhuna,and Ambastala Stupa at Mihintala etc. TissaMaha Stupa at Tissamaharama was perhaps thefirst large stupa to be completely restored, thework being completed in 1898. Restoration ofRuwanweliseya was carried out around thethirties of the last century.

Eng. (Vidya Jyothi) W. N.Gamunu Silva B.Sc(Eng), D.I.C.Ae,M.LE(SL) Senior Engineering Consultant, Ministry of UrbanDevelopment and Sacred area Development and Reconstruction andDevelopment Agency of Ministry of Nation Building.

41 ENGINEER

Lankaramaya - Before restoration

Lankaramaya - After restoration

The Department of Archaeology appears to havehad no direct involvement in the restoration ofboth Tissa and Ruwanweli Dagobas and verylittle technical details are available of the workscarried out. Since the restoration works wereundertaken by restoration societies under theguidance of clergy, primarily for the purpose ofworship, the technical advice given by theDepartment of Archaeology though accepted incertain cases appears to have been accepted withcompromise or not at all in other instances.Kirivehera, one of the mega stupas ofPolonnaruwa was conserved by the Dept. ofArchaeology during Commissioner Bell's time.

With the formation of the Central Cultural Fund(CCF) in 1980, the Department of Archaeologyfound an able partner for extending and acceler-ating its activities. The projects falling within theCultural Triangle such as Jetavana, Abhayagirimonasteries in Anuradhapura, Alahana Pirivenaat Polonnaruwa, the rock temple at Dambulla,Sri Dalada Maligawa and the devala complex inMahanuwera were handled by the CCF. Allworld heritage monuments were started withfunds from UNESCO and funds generated

through Archaeo-tourism. The ArchaeologicalDepartment with Government funds was able tocarry on archaeological works in other parts ofthe country. Over 25 large and small ancientstupas have been either conserved, restored orreconstructed during the last century.

Mahaseya Mihinthale - Before restoration

During the last three decades of the 20thcentury, some major conservation works onstupas as well as other temples, undertaken bythe Central Cultural Fund as well as theDepartment of Archaeology include theconservation of Rankoth Vehera and TivankaPilimage in Alahana Pirivena in Polonnaruwa,the Jetavana Stupa and subsequently theAbhyagiri Stupa in Anurdhapura by the CentralCultural Fund, the stupa at Mihintale, theMirissavetiya Stupa in Anuradahapura,Somawathie in Polonnaruwa, Yatala, Sandagiriand Tissa maha Stupa at Tissamahrama,Dematamal Vehera at Buttala, Stupa atYudaganawa together with conservation ofancient Bodhisatva and Buddha statues atMaligawila, etc. by the Dept of Archaeology.

During this period, professional engineers hadan opportunity to work alongside archaeologistsand conservationists and all parties benefitedfrom this exercise. The engineers had anopportunity to learn ancient techniques ofconstruction and contribute substantiallytowards improvement of conservationtechniques especially through application ofmodern methods of structural analysis. Theneed for engineering inputs in conservation/restoration of ancient mega stupas wasespecially felt after the catastrophic failure ofpartly restored Mirissavetiya Stupa on 10-06-1987. The history of conservation attempts on

ENGINEER 42

Mirisavetiya, and the subsequent attempts on(Havana , and Abhyagiriya would showevolution of conservation techniques during thertvent past.

K irivehera Kataragama - Before restoration

Kirivehera Kataragama - After restoration

Restoration of Mirisavetiya Chaitya:

Although more than 25 large stupas had beenrestored or conserved during the previouscentury, some even bigger than Mirisavetiya,there had never been a failure of the magnitudethat occurred on 10.06.1987 on a partiallyrestored stupa. Although several vertical crackshad been noticed on the restored dome, theactual separation and movement of largesegments of new brickwork took place onlyseveral hours before the planned enshrinementof relics. This tragic event led to variousdiscussions and speculations among the generalpublic, the Buddhist clergy as well as among thearchaeologists and conservators, finally leadingto several engineering studies being conductedto ascertain the reasons for the failure. Amongthese studies those carried out by the CECB, theDepartment of Architecture of the University of

Moratuwa and by the State EngineeringCorporation in collaboration with StemsConsultants and the Faculty of Engineering ofthe University of Peradeniya are significant.

Mirisavetiya - Before restoration

Conservation principles;

If a cultural monument is in good condition,what is required is good maintenance.However, when it is in a state of decay, thedegree of intervention required whether it isconservation, restoration or reconstruction forpreservation of the cultural property is offundamental consideration. One of the cardinalrules of archaeological conservation is that norestoration should be attempted withoutexcellent physical and archaeological evidence.However, it appears that the completerestoration of stupas have been undertaken withconjectured shapes and dimensions based onproportions of later examples. The other mainguidelines of archeological conservation/restoration include retention of maximumoriginal structure, minimum use of modernmaterials, ability to remove these materials ifthey adversely affect the monument and use oftechniques that negate the need for future large-scale interventions.

During the last decade of the 19th century, thecolonial government carried out someconservation work on the "Hatareskotuwa"(The square) of the Jetavana Stupa (then calledAbayagiriya) and the "Devatakotuwa" (lowercylindrical section of the spire) of the Abayagiristupa (then called Jetavana). No attempt wasmade to either conserve or restore the domes ofthese large stupas. However they choseMirisavetiya, one of the smaller stupas forcomplete restoration. (According to Mr.

43 ENGINEER

Smithers' report the heights of the four majorstupa ruins were, Abayagiri-245 ft., Jetavana-232ft., Ruwanveliseya-180 ft., Mirisavetiya-80 ft.).

The

rrtrlxbahn

The public works department was responsiblefor the design and supervision of work. Theconservation proposal was to restore the stupaover the remaining ruins using a series ofcircular brick piers and arches, in order tominimize material requirements as well as thestructural load imposed on the old structure.The finished height of the completed stupa wasto be 205 ft. and the diameter of the dome 140.5ft. The engineers decided to use lime mortar(and not cement mortar). Work was abandonedwhen the height of the dome stood at 60 ft.

Mirisavetiya Stupa as well as all other ancientstupas are basically great mounds of burnt claybricks stacked into stable shapes (mound ofpaddy, bell, hemisphere etc.) using only "butterclay" (Navaneetha) as a binder. In all cases, itappears that these great brick mounds werebuilt on rock outcrops or on solid rock. The topof the mound had carried a square fence (whichgradually over the years was replaced by a solidbrick structure called the Square or theHatareskotuwa) and a single stone pillar at thetop (Upagala) with one or several stone discs(Chatras) of varying diameter attached to thispillar (somewhat like an umbrella), which overthe years was replaced by a solid brick spirecalled the Kothkerella. The whole brick structurewas protected from the elements by a thick limeplaster cover. The butter clay mortar probablyallowed movement of bricks without buildingup internal stresses.

Mirisavetiya - During restoration - 1906

As long as the bricks used were of good quality,(in fact they were found to be of excellentquality, and special brick kilns had to be startedto obtain the required comparable quality forrecent restoration works), and the lime plastercover was maintained, the ancient stupas wouldhave been stable and durable structures. Oncethe plaster cover is lost, plants would grow intothe structure and eventually lead to decay of thesurface of the dome. The first part to be affectedwould be the square and the spire. Collapse ofparts of the square in most ancient stupasappears to have damaged the dome more thanthe damage due to plants and erosion.

Mirisavetiya - During restoration - 1980

The second attempt at the restoration ofMirisavetiya stupa commenced in 1979 by aStupa Development Society with the Dept. ofArchaeology, advising, guiding andsafeguarding the archeological and architecturalevidence of the monument. The concept was torestore the stupa as a solid brick dome with asquare and a Kothkerella to a height of 187 ft.and a dome diameter of 143 ft as per thedrawings prepared by the Department. A set ofreinforced concrete rings was to be incorporatedonto the periphery of the dome at ten-footlevels. Cement mortar was to be used in the

ENGINEER 44

m'wr.il proportion of 1:5. Brickwork carried outIn the previous attempt was to be removed andI hi- now brickwork was to start from the originalI n n kwork (11 feet above the basal rings or'tVsawas').

Mirisavetiya - Failed restoration - 1980

In this attempt the original brickwork had beenstripped only to a depth of 2.5 feet from theouter face at the base. It was the opinion of theengineers that the main reason for failure of theilome was the crushing of the new brickwork atIts base, which was only 2-3 feet wide. It wasalso the opinion of the experts that total mass ofnew brickwork of the dome was made to bearon the base through an arch action oncontraction of the ancient brickwork done withday binder. Inadequate cleaning of decayed oldsurface brick work, improper keying of bricksbetween the old and the new, non inclusion ofthe proposed number of RC rings, (one insteadof six), ingress of water into old brick workduring and before construction were thought tobe other possible contributory factors.

HM-Mtfe„•»<.;« **

Y

The third attempt at restoration of Mirisavetiyastarted in 1990 by the Department ofArchaeology. A proposal for construction of a 12inch thick reinforced concrete shell covering theancient brick work and at the same timecarrying the load of the square chamber and thespire was not acceptable to the archaeologists

since it violated one of the basic principles ofconservation. A proposal made by the StateEngineering Corporation in collaboration withthe late Dr. Balasooriya of Stems Consultantsand the Dept. of Civil Engineering of theUniversity of Peradeniya was finally acceptedby the Department of Archaeology. Thisproposal was to restore the stupa as a solid brickstructure with the restored dome on top of theancient brick mass, and a new square chamberand a spire. Geotechnical investigations hadrevealed that bedrock was only a few feet belowthe stone paved terrace (Salapathala Maluwa).It was decided to use standard engineeringbricks of a particular strength (determinedthrough finite element analysis of the proposedmodel) and a very lean sand/lime/cementmortar (instead of butter clay), used successfullyby the Dept. of Archaeology in the past forconservation work on stupas for the restorationof the stupa above the "Salapathala Maluwa".Assuming that much of load transfer of the newbrick work would take place through arch action(with the possibility of separation taking placebetween old/new brick interface due todifferential movement: elastic, thermal andshrinkage), a minimum base width of 13 ftcircumferentially was insisted upon by theengineers leading to some ancient brick workbeing removed at some areas of the base (underprotest by some archeologists).

Mirisavetiya - All ancient brickworks carefullyremoved

In order to cater to the hoop tensile stress in newbrick work of the dome, a reinforcing system ofsteel bars (sand blasted and epoxy coated),placed circumferentially and radially, in 6"x6"channels formed in the brick work at 6 ft.intervals, both radially and circumferentiallyand subsequently filling them with concrete was

45 ENGINEER

recommended. This system of reinforcing was tobe repeated at every 6 ft vertical height of thenew brick work of the dome.

Pesawa basel rings were restored first and therevolving template for the reconstruction of the domewas installed

Prior to casting of Re-inforced concrete rings

Prior to casting of Re-inforced concrete rings

Both the Hatareskotuwa and the spire were tohave a RC framework. Work commenced in1990 and was completed with the pinnacleunveiling ceremony on the Poson Full MoonDay in 1993, about a month after the death ofPresident Premadasa who spearheaded thisrestoration work.

The biggest problem turned out be the supply ofthe required quality of standard engineeringbricks. The engineers had specified a minimumcrushing strength of 400 psi. The manufacturersof bricks had to be specially trained by expertsfrom NBRO in making and burning bricks to therequired standard and quality. A tunnel kilnespecially set up by CCF at Galkadawala inAnuradhapura (to manufacture larger sizedbricks for restoration of Jetavana stupa, whichhad also commenced around this time) wascommissioned to supply the quantities requiredfor the upper part of the dome, Hatareskotuwaand Kothkerella. It was decided by thearchaeologists not to plaster the restored stupa.Therefore for the surface of the dome, brickswith a higher clay content was obtained fromthe Ceramic corporations brick factory atElayapattuwa. However with pressure from thedevotees and the clergy the stupa wascompletely plastered in 1995 completing therestoration works.

Dome construction

Work commenced in 1990 and completed with thepinnacle unveiling ceremony on the Poson Full MoonDay in 1992, about a month after the death ofPresident Premadasa who spearheaded thisrestoration work.

ENGINEER 46

Ilif mtortd Mirissavetiya stupa being given a newft littler

t'onNcrvation of Jetavana Stupa;

i.iirhf line drawing of Jetavana Stupa

An early photograph of Jetavana Stupa

Restoration works on the Jetavana stupacommenced in 1981 by the Central CulturalFund. Built by King Mahasen (275-301 AD) onthe spot where Arahat Mahinda was cremated,the original height of the Jetavana stupa iscalculated to be 404 ft. That would have made itthe third tallest building in the world, aroundthe time of collapse of the Roman Empire. When

restoration works commenced, the originalstupa with various subsequent additions had anouter retaining wall and four gateways orWahalakadas, a sand terrace or a Welimaluwa,inner retaining wall, access steps, a stone pavedterrace or Salapathala Maluwa, 3 basal ring orPesawas, 4 stone altars or Ayakas facing cardinalpoints, stupa dome, a square box,(Hatareskotuwa or Harmika), and a phinial orKothkerella. Available evidence showed thatthe stupa was constructed as a series of solidlayers of burnt bricks creating a monolithicstructure.

The average size of the bricks used was large(18"x7"x 2-1/4") compared to modern claybricks. A finely graded aggregate of 70:30 sandclay mix had been used to manufacture theseancient bricks. Compression tests revealed anaverage strength of 650 psi. The bricks werebonded with a fine layer of Butter clay,(Navaneetha), The outer surface of the stupawas protected with a lime/sand plasterexecuted in three operations, The first levelinglayer of coarse sand and lime, (5"-3"), a secondlayer of finer sand and lime (1.5"-2"), finished offwith lime putty. The main structure was

Jethawanaramaya - Completely detached face of oneside of Hatharaskotuwa

47 ENGINEER

^T^L

founded on bedrock situated about 28' belowthe present stone paved terrace. Extreme careand control of both materials and workmanshiphad been exercised in the ancient foundationbrickwork. The dome brickwork too was ofexcellent quality.

At the beginning of the project Jetavana stupa toowas to be restored fully. Surveys had been carriedout to determine the shape of the stupa from thesurface bricks still intact on the bottom part of thedome. However by 1994 with the completerestoration of Mirisavetiya stupa, (using even aminimum quantity of reinforced concrete) therewere objections from archaeologists to a completerestoration using once again reinforced concretering beams as in Mirisavetiya.

After a long exchange of ideas, it was finallydecided that only a conservation of the stupashould be attempted and not a completerestoration. In order to preserve the ancientstructure, it was decided only to remove theovergrowth of trees on the dome surface, clear theloose and decayed surface bricks and relay a newbrick cover only a few bricks deep. Whereverlarge masses of brickwork were missing from thedome, a certain amount of new brickwork was tobe added for structural stability and to avoidponding of water. However, this was to be kept tothe bare minimum. Accordingly the steeltemplates installed to obtain the final finishedshape were removed since there was no necessityto keep to a determined shape.

Foundation brick work up to bed rock-jetavana stupa

Cleaning the surface and relaying the new coveron the dome commenced from the bottom of thestupa. Bricks made at the Galkadawala kiln ofthe CCF made to the same average size as theancient bricks, were used for this work. A verylean sand/lime/ cement mortar used by the

department of archaeology for conservationwork on earlier stupas was selected for use as thebinding mortar of the covering layer of newbrickwork. The new brick cover was to have abroken face on the surface and was to be pointed.

Exposed ancient brick work of the dome

The conservation of the dome by this processwas carried out successfully. However theconservation of the Hatareskotuwa which hadbeen previously conserved in the last decade ofthe 19th century posed a problem. Preliminaryexcavations carried out showed that in theprevious conservation works a limecrete wallhad replaced part of the original face of theSquare, with the space between the wall and theancient brickwork in the middle, bearing theKothkerella, filled with brickbat. Accumulationof water inside this "Tank" had caused thewestern wall to collapse a few years after theconservation works of the English. Excavationsat the base of the Hatareskotuwa also provedthat the early conservators had erred indetermining the position of the base of theconserved Hatareskotuwa. In fact excavationsunearthed the original top of the dome witheven the plaster intact, around 8 ft below thebase chosen for the conserved Hatareskotuwa.

Addition of new brick work enclosing the old brickwork-Jetavana Stupa

ENGINEER 48

Addition of new brick work enclosing the old brickwork-Jetavana Stupa

Segments of ancient brickwork unearthed inthese excavations showed certain aestheticfeatures that had not been incorporated into thepreviously conserved Hatareskotuwa. Therewere also large gaping cracks on two remainingsides of the Hatreskotuwa walls.

All these new discoveries as well as the structurallyimpaired Hatareskotuwa walls led the DirectorGeneral of Archaeology (assisted by an advisorycommittee of eminent archaeologists) to request theCentral Cultural Fund to remove additions by theEnglish conservators and to re build the outersections of Hatareskotuwa on all four sides leavingcertain ancient original brick work on some walls.

Originalplaster onthe top ofthe dome

Excavations unearthed the original top of the domewith even the plaster intact, around 8 ft below thebase chosen for the conserved Hatareskotuwa.

A segment of the old Hatreskotuwa missed by theEnglish conservators uncovered in recent excavations

Partly restored Hatareskotuwa and conserved dome.The new brick cover has a broken face on the bricksand were pointed

Work on the conservation of Jetavana is nowcomplete. No new engineering techniques havebeen applied in the conservation works on thisstupa except for a 6" thick RC concrete layerwith a stainless steel wire mat at the base of thenew wall of the Hatareskotuwa and a ring beamat the top.

49 ENGINEER

Conservation of Abhayagiri Stupa;

An Aerial view of the Abayagiri Stupa prior tocommencement of conservation

Built by King Vattagamini Abhya (89-77 BC), today in its ruined state is 72.6 meter to the top ofthe ruined spire from the basal terrace. With thelessons learnt from restoration and conservationworks on Mirisavetiya and Jetavana Stupas,conservation works on the Abhyagiri Stupacommenced around 1996.Although the originalproposal was for a Mirisavetiya type restorationthe same methodology was to be adopted as inJetavana for restoration works.

With new knowledge of conservation techniquesused in other countries for brick monuments,conservationists were objecting to the use ofcement in binding mortar of the external layer ofbricks, although lime was acceptable.Accordingly, a special mortar was developed bythe National Building Research Organizationusing lime with paddy ash, anthill clay andground clay tile powder. This special mortar hassince been used successfully on the dome.

Addition of new bricks was not required at thebeginning since the good ancient loose bricksobtained from the surface of the dome had beenadequate for the protective cover. However,new bricks were required to fill certain washedaway sections of the dome and to rebuild thedamaged Hatareskotuwa.

Conservation works on the Hatareskotuwa.Hatareskotuwa too is being conserved presently andit is evident that some additions during the lastconservation attempt would have to be removedsince they have been laid on loose and decayedancient brick work.

" • I

Conservation works of the Kothkerella-AbayagiriStupa

The Kothkerella which was in a very bad state hasalready been conserved.

Most of the unskilled labour and even some materials(ant hill clay, burnt paddy ash etc.) are presentlyprovided by volunteers who come in large numbersfrom all parts of the island daily to take part in theconservation works, lend a helping hand to thepermanent staff.

The outer layer of the dome used ancient bricks withthe NBRO lime/paddy ash/anthill clay, ground tilepowder, sand mix binder

ENGINEER 50

I'nirfKoncy conservation work on Tissamaharama Stupa;

Two other failures of restored dagobas haveIxvn reported recently. They are Tissamaharamauli i pa restored in last decade of 19th century and(i another small stupa close by called theStuidagiri stupa, restored during the last twodtrades. Tissamaharama stupa showed a largenumber of vertical cracks evenly spaced aroundthe dome around 15 years ago. Cracks alsoappeared on sections of the Hatareskotuwa, Thecracks were so large that engineers were of theopinion that a collapse was imminent.

At the request of the Department ofArchaeology, the State Engineering Corporationproposed a series of steel or RC rings spaced atsuitable intervals on the dome as an emergencymeasure. Two RC rings were constructed at thetop of the dome initially. However, it was theopinion of some experts that even removal ofcertain bricks on the surface on the dome tobuild the RC beam was not acceptable.

Therefore post tensioning the dome from thesurface with stainless steel cables running overstainless steel plates (pads), spaced arounddome was attempted as a desperate measure.

External stainless steel prestressed cables andstainless steel bearing pads

The segment of the Hatareskotuwa that showedearly signs of separation too had been externallytied up. This intervention has since decreasedsubstantially the rate of propagation of crackson the dome and would perhaps ceaseeventually.

Cable connectors There are four of these on each cable

One of the Reinforced concrete rings tying up the domeunder construction being inspected by Prod. Crochet

51 ENGINEER

Stressing of cables in progress

Sandagiri Seya after the recent collapse of the addedsegment in restoration works

'I'hi1 cracks have been already filled and a newpl.istor had been added since.

Saiuldgiri Stupa;

S.nu l , i j ' , i r i ship, i i -xpi - r i i -nced a catastrophicl . t i l u r v r ecen t ly with separation of largesegments of new brickwork very similar toMirisavetiya failure. Re-conservation works hascommenced. The reason for the failure appearsto be the same as in the case of Mirisavetiya. Theconservationists and engineers have finallydecided to use the very same technology usedby the original builders, for reconstruction of thedome, namely, the use of "Butter clay" as abinder with a lime mortar cover. This wouldperhaps fulfill all conditions laid downpresently for conservation of ancientmonuments.

ENGINEER 52