Roman Aqueduct of Segovia
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STRUCTURAL ANAL YSIS OF HISTORICAL CONSTRUCTrONS P. Roca, J.L. González, A R. Mar( and E. Oi'tate (Eds.) e CIMi\:E, Barcelona 1996 ROMAN AQUEDUCT OF SEGO VIA F. Jurado Jiménez E.T.S. de Arqllitectllra de Madrid cf José Fentanes 20 28035 Madrid Spain HISTORlCAL AND DESCRIPTIVE DATA The origin of the water conduct is located in the high course ofthe "RIO Frio" river The dam, small tapping prey ofthe waters, is formed by granite pieces clamped with plates ofiron received with lead. 11 can derive near 50 liters ofwater per mil1ute . It s buried conduet, about 11 ,4 km long, was piped in ! 929 through a pipeJine of cemem of50 and 40 cm diameter, making 110 registration tanks that mark contour, a1most completely original. It possess a first "casteHum aquae", call ed The Stone I-Iouse, a 5,50 x 5,90 m rectangular building of masonry \\Iith lime mortar, with a pointed vauil and a 2,25 x 3, lO m underground deposit \V il h a depth of2 m From this house begins lhe granile channel carvcd in "U" fonn . It crosses under the current 5an IIdefonso highway A secti on was dismantled upon the variation ofthe levei ofthe highway and has been 10s1. The high section begins with XV II eentury eylindrical ashlars that form an obelisk where one ean find a parchment supported by two arms wilh lhe representation oflhe aqueducI According 10 Somorroslro, these ashlars were found near 5an Matias hermitage, in "La Santa Cruz" road and were pUI on this site on 1951 After 141.5 m ofhigh cond uet (wall of 1,4 m broad and 1,4 to 3,5 m high). onearrives to the second castellum aquae, 8,90 x 7.50 m decanting building, wilh a 4,25 x 2, 18 m and 2.90 m of deplh inner pie also covered with a poinled vault From this point lhe si mple areade and the numbered pillars thal we alt: u~ing as referenee begin So thatthere exists a first alignrnent of6 arches. a 25 arches sccond alignlllcnt and a third Orle wilh 44 arches. unlil il arrives 10 lhe 75 1h pillar, where the sharper alignment ehange is produced and it bceames a double series of archs From the 35 110 pillar to 51 1h therc are diverse reconstruetions, one ofthem daled in 1868 according to the cxisting inscriplion in an ashlar. Thc double arcade is composed of 43 double arches that reach more than 28 m in height over the eause\Vay In I Oi", 108 111 and 109111 pillars a cartel appears (the "sotabanco") where Iherc exisled lelter inscriptions (presumably eneased with lead in the granite 308 STRUCTURAL ANALYSIS OF HISTOR ICAL CONSTRUCTIONS bronze Ictters). The 108th pillar is thicker in lhe superi or part and has two niches (original, by the inside fingerprints oflhe boisting cJamp), where two seulptures were put on 1520. Crossing the medieval defensive walls (in the place called " Postigo") the conduet continues in a walJ and other three arches, an almost in right angle alignment change and otber 43.7 In long \Vali with the conduct in it s upper parto From here, lhe aqueducI's conduet returns to be buried under the slreets until arriving 10 lhe "Alcázar", by a way of underground stone ehannel s ofmore Ihan 1 km, known in many sections for lhe excavations, and havillg served in some cases 10 condue! residual walers. A total of 15 km of aqueducI wilh a 958 m high water conduct and wilh variable slopes, lhe minimal slope in the central part (88th to 1 13 th pillars) at 0,3%. The currenl 30 x 30 cm upper channel, c10sed aI the sides with masollry, is not the o riginal eondue!. This was lower down (rcmains still ex ist with ali assurance) and had a section about 60 x 60 cm. STUDIES AND INTERVENTlONS THAT IT HAVE BE EN CA RRJED O UT SINCE 1992 Stop or the traflie or vehicles u"der the Aqueduct. The decision was taken dircctly by the Segovia municipal govcrnment.. even though il generales evident int ernai IraOie problems in Segovia, it has been a drastic decision to eliminate the most probable cause ofthe current deterioration ofthe Roman Aqueduct. SCllfToldings alld prcvcntlllivc props Ill:1CC for proteclion and inspection. The scaffoldings were built sin ce July 27th to August, 1992. They have been used up until 1l0W for lhe prolection and inspection. Delailed Visual Recognition. An urgent inspection was ordered for lhe section between pillar 50 and lhe " Postigo" wall, !hat is to say, the highest part, the most monumental. Said inspection report warned of the dangers of fal1ing stones from detachments, local breaks and deteriorations and other damage observed in the ashlars, wilh a cJear concentration in lhe area of the greatest now of vehicJes. th The inspection began on August 13 , 1992 and was ended in November ofthis same year. Later, in March of 1. 993 lhe inpeclion was amplified to lhe scaffolding zane. Surnrnary or lhe exisling documentation. Asidc from the vast bibliographical documentation, ali lhe available information on last interventions o n the Aqueduct have been gathered. In particular, o lle must to hig hlight the interesting photographs (obtained from the files of!he Ministry ofCulture) taken by Laurent ( 1863) or by Cli lTord (1853), tha! have served to compare, in a detailed way, the slate lha! lhe ashlars had !hen wlth lhe eurrent sI ate, seeing the great acceleration of the deterioration in these last ycars. F. JURADO JIr..'IÉNEZ I Rom:m :J.qucduct or Scgovia 309 In effect, it is easy to appreciate the delerioration that has rounded lhe corners of the pillars 50 that now it is difficult to see the carved li ne ofthe pillars' corners, that is easily observed in lhe photographs of a century ago. Whal are, then, lhe factors Ihat have appeared in these last one hundred years to deteriorate lhe stone more Ihan in lhe eighleen previous centuries? The answer 15 evidently: the traflic ofvehicles and the atmospherical poll ution. Then, Ihese t\Vo imporlant causes are emphasized as the way to investigate lhe origi n of lhe current degradation Ihat we already observed in the aqucduct visually. PolIUlion and in-missions measuremenl At first , in October of 1992, measurement is taken from a mobile unit, and, si nce January of 1993, a fixed unit Is installed in coordinalion with the town hall of Segovia. Climatological paramelcr measures were taken as well as magnitudes based on the seasonal cycle. The traffic was already slopped under lhe Aqueduct, therefore the obtained graphics correspond to a situation less contaminated by lhe passing vehicles than thal which existed before July, 1992, when this decision was taken. In spite ofall, it can be observed thal, in winler monlhs, Ihere is a clear increase alllong lhe emissions of, for example, carbon monoxide and sulphur dioxide, which Illeans thal lhe housing healing has a great influence on the pollulion. Bi ological deterioralion a nalysis. From March lo July of 1993 the Microbiological Leclure ship of Alcalá Universily ha s been conducling sludies 011 lhe microorganisms lha! by biochemical and biophisical actions possess the capacity to deteriorate granile. Microorganisms that they have isolaled and identified and Ihat, witholll doubl, co ll aboralc with other higher organisms: vcgelables and animais (birds, over ali). An ab normal levei of microorganisms was observed, very high for granile. II is evidenl Ihat microorganisms ofthe sulphur cyclc and those oflhe nit rogen cycle have lhe possibility of convcrting elements lha! exist in lhe environment into acid, due to lhe almospherical pollution, assaulting Iherefore lhe granite. Sludy of lhe foreign ma teriais to lhe Aqueducl (used in the res tora tion of 1973). As hislorical doclIrnenlation we had lhe inlervenlion Ihal look place in 1973 by the engineers, Fernández Casado and Aurelio Ramirez, widely described in the book "Thc AqucdllcI of Segovia, lhe survival of a hydraulic work" of Aurelio Ramírez, asidc from having lhe volllnlary collaborali on oflhis same aulhor. Ilowever, lo prove lhe 5COpC of th C5C works and lhe state of conservatiol1 and / or delerioration ofthe materiais and products lhat were used, thi s study was cOllductcd and endcd in March of 1993 . Among other things, sample were taken oflhe Iransvcrsc "boltings" made wilh brass bars and resins, as wel! as the zones thal were made wilh cement grout injeclions. Al so. samples were taken ofthe walerproofing ofthe upper channel. As cO ll sequence oflhis sllldy we observed Ihal lhe Slale oflhe brass boltings, lhe epo;.;i resi n and lhe channcl waterproofing , was in peffecI condilioll. In particular, Ihere is no Iype ofmicrofi ssurali on in lhe face oflhe grallit e in lOuch wilh lhe resin, which gives lIS an expert "mallomeler", submittcd to lhe outdoors during Iwenly years, so Ihat ifwe 310 STRUCTURAL ANALYSIS OF 1I1STOR1CAL CONSTRUCT10NS need to relurn 10 make a "suture" of this kind, we can use the same material with the guarantee of ils unalterabilily As for lhe venical cement grout injections, fortunalely we found few remains. We say fOl1unalely, because Ihi s is an issue Ihat we should criticize afthe 1973 reslOralian: in lhe errort to till in lhe spaces among the sla nes in arder lo produce a certain monolithic eITec! Many perforations were tOlally cmpty : we do no! know iflhe grour flowed and il did not ever arrive la filllhe perforalion or if. with time, il has been degradare 50 Ihat il has becn lotally 10st. We agree therefore with lhe transverse boltings Ihal \Vere made in 1973, since the only thi ng what was intended with this was to join lhe stones Ihat had splil and acles as a hobble among lhe Iwo ashlar leaves ofthe upper part oflhe Aqueduct, however, as we have alrcady said.