Structural Analysis of Historical Constructions - Modena, Lourenço & Roca (eds) © 2005 Taylor & Francis Group, London, ISBN 04 15363799 Saving minarets at risk in Afghanistan G. Macchi Deparlmenl ofSiruclural Mechanics, University of Pavia, Ifa/y ABSTRACT: The minaret of Jam is now included in the World Heritage List. Such an outstanding tower built in the 12th century A.D., 65 m high and isolated in the mountains at the altitude of 1900 m, has exceptional value from the architectural and historical points of view. The author, on behalf ofUNESCO, undertook investigations intended to assess the structural stability of the tower, including static and dynamic verifications. The study ofthe seismic hazard of Iam was the occasion to reconsider a catalogue of 1300 seismic events which reconfirm the high seismic risk of the city of Herat, where another set of important archaeological remains is also under the highest attention of UNESCO. fNTRODUCTION The reasons of the dramatic loss of the architectural heritage in Afghanistan are not only earthquakes, but also destructions due to war. The minarets to be saved are a fundamental testi­ mony of the ancient roots of such unhappy people. Adding the minaret of Iam to the World Heritage List UNESCO is working for the preservation of such memories and for the civic and cultural reconstruc­ tion ofthe Country. The safeguard ofthe five minarets remained in Herat is part ofthe same project. The knowledge of the Afghan civilization dates back to the end of the second millennium B.C. when Figure I. Herat. The 9 minareIs oflhe Musallah in lhe year the Aryan people had their capital in Herat, called Aria 1915 . at that time. Zoroaster's teachings and monotheistic doctrine started in northern Afghanistan around the year 600 B.C. and are known to us through the "Avesta" During the 15th centllry Herat was again the cap­ books, which influenced the religion in Iran for about ital of a splendid empire with the Timurid dynasty twelve hllndred years. (Shah Rukh, Tamerlane's Slln, and the famous qlleen Alexander the Great founded new towns in the Gawhar-Shad). It was a golden era for literature, art area and built the citadel of Herat, called at that time and architecture. The nine minareIs ofFigure I are the Alexandria Ariana, (330 B.C.). vestiges ofa large religious complex destroyed dllring The country professed then for centuries Hindu and lhe 19th century wars. Some ofthe most famous mys­ Buddhist religion under variolls dynasties as Mall­ tical Islamic poets of the SlIfism as lami were active rians, Bactrians, Kushans and Sassanids, lIntil the there, following the ancient tradition dating back to Islamic conquest (Ghazni in the year 869 A.D.). Amr el Makki, Ansari, Sanai, lalalllddin Rumi who left The Islamic dynasties of Samanides and Ghaz­ Balkh before the advancing hordes of Genghis Kahn navides developed culture and art. The outstanding (Schimmel 1973). minaret of Iam was built by the Ghurid sultan Ghiya­ At the beginning of the 19th century a period suddin (1157- 1202, buried in Herat) just before the of nearly continuolls destructive wars began, during entire destruction of lhe region due to Genghis Kahn which Persians, British and Russians contended for in 1222. Afghanistan involving local fights. 1375 Figure 2. Herat. The remaining minareIs of the Musallah are only S in lhe year 2003. Figure 3. Herat MS - damages. Crack a! the base. After 40 years of a monarchal parenthesis, in 1973 a CONCRE TE new terrible period ofwar began and is still devastating BlOCK N the Country. Many Afghans left the Country severa I years ago; thousands of refugees of the 2002 war are coming back now and try to rebuild a destroyed society with productive activities and schools. 2 WHAT HAS TO BE SAVED? Among the hundreds of archaeological sites, a number of important ancient buildings need urgent safeguard CQNCRETE works, among them the minaret of Jam and the five BLOCK S mi narets ofHerat. Many mi narets were lost in the past and the ones still existing are exposed to a serious risk of coll apse for the seismic actions together wi th the effects of their dangerous inclination and the deficient state of the masonry. The architect Andrea Bruno began in 1961 surveys and projects for the restoration of Afghan monllments ~39. 50 together with the ltalian lnstitute rSMEO, and then surveys and restorations in Iam and Herat from 1976 26.50 ;: d~~ ~ 2 cables00.6" to 1979 for UNDP and UNESCO (Bruno 1981). The 3.00 allthor, as Scientif ic Advisor of UNESCO, undertook 4.50 recently (2002) investigations intended to assess the i ( /. 3.00 structural stability and seismic risk of th e minarets in ~--~L. 2.50 Iam and Herat and cooperate with A. Bruno for their restoration. Figure 4. Hera! MS - emergency safeguard. 3 EMERGENCY SECURlNG OF THE The tower is on the verge of coll apse. This opinion, MINARET FIVE IN HERAT expressed by ali the experts hav ing had the opportunity to see it, was confi rmed by the assessment performed Minaret 5 is a brickwork tower 42 m high with a diam­ by the author on the geometrical survey of Santana eter of 5 m only at the base. 11 is built with hard and Stevens (2002) and the direct site measurements bricks and was once at the corner of the demolished by precision instruments during the 2003 UNESCO Musallah and stands now isolated in the garden of the mission. The out-of-plumb is 2.70 m and a large hor­ Mallsoleum of Gawhar-Shad. izontal crack is present at the he ight of 3111 from the The surface has an elegant kashi decoration with a base. The strllctllral analysis showed that th e eccen­ geometrical pattern filled in with bllle tiles (Fig. 7). tricity of the self-weight is sllch that the cross section 1376 Figure 5. Herat M5 - emergency intervention: model. Figure 6. Hera! M5 - equipment. is cracked for one third of the diameter, and the edge ofthe masonry is subject to a very high compression, 1.2 MPa. 80th data show that even a very moderate earthquake or a strong wind would cause the collapse of the minaret, as already happened to the four other minarets which were still standing in 1915 (Fig. I). The author undertook precise measurements in July 2003 with a Huggenberger removable deformeter and a high precision tiltmeter. In the space offour days of strong wind the strains measured across the horizon­ tal crack showed a continuous periodic opening with a frequency ofO.5 Hz and a slight but continuous open­ ing of the crack and an increase of the tower leaning (about 10 arcsec). The present tilt ofthe tower is prob­ ably due to severa I successive earthquakes; we are not sure ofits evolution in time, but according to the avai l­ able information the out-of-plumb was only 0.90 m in 1977. Other evident damages, as a wide opening in the shaft caused by a missile during the war, are less alarming than the overall lean, which may lead to a sudden collapse. 80th the numerical assessment and the site mea­ Figure 7. Herat M5 - cable in stallation. surements showed such an extremely alarming sit­ uation and that emergency measures were evidently needed. There was not enough time for the imple­ implementation in few weeks, as suggested by the risky mentation of the structural intervention prepared by situation ofthe monument. the author and approved by UNESCO in April 2003, The concrete blocks, built by local workers, were i.e. a stabilization of the foundation by means of sin­ embedded in the soil at a distance of 25 m from the gle bar micropiles and strengthening of the elevation basis of the tower. The centers of the blocks were by means of a vertical prestress applied through high placed on two axes 15 0 far from the maximum lean strength steel bars directly connected to the micropile plane in order to secure the tower for an angle of30°. In bars. Therefore, emergency measures were applied to each block 4 steel pipes were embedded in the concrete the minaret during July, August and September 2003. in order to accommodate 4 stays and their anchorages. The emergency securing was obtained by means of Each stay was made with a single 0.6" strand of gal­ 2 simple steel stays anchored to concrete blocks poured vanised high tensile steel (area of 150 111m , strength in the natural soil (out of any remains), avoiding in 265 kN). Each stay was applied along a precisely this way the necessity of driving piles as fixed points. defined path (see Fig. 4 and the modeI ofFig. 5): each The proposal was conceived in such a way to use only strand starts from a concrete block and reaches the means available on site for the anchoring to the soil, tower surface with the appropriate inclination, then and steel cables sent from Italy (together with their is winded to it along a variable angle spiral until a anchorages, hydraulic jacks etc.) in order to allow the sub horizontal circle allows to begin a symmetrical 1377 descending path towards the other concrete block and its anchor. Thi s arrangement ofthe stays was essential in order to transfer to the tower the vertical component ofthe stabilizing action through the steel-to-masonry friction, therefore wi thout slip and without heavy steel fastenings. In that way the small force of 100 kN only, applied by jacks to each of the 4 strands, has been sufficient to close the base crack, to decrease the eccentricity of 0.65 m and therefore bring back the masonry to a state oftotal compression; the maximum stress was reduced to 0.6 MPa.