Structural Analysis of Historical Constructions - Modena, Lourenço & Roca (eds) © 2005 Taylor & Francis Group, London, ISBN 04 15363799 Study of Place Stanislas coloured pavement for its historical restoration J.M. Mechling Université Hel1l'i Poincaré - Nancy 1, Dpt Génie Civil - IUT de Nancy-Brabois, Villers-Iés-Nancy, Fran ce R. Elter INRAp, Ludres, Fi'ance ABSTRACT: Listed as a World Patrimony by UNESCO, the Place Stanislas (Stanislas Square) in Nancy (France) was built in 1755. The ground ofthe Square will soon undergo a complete remodelling which aims at restoring it to its original glory. To prepare the project, a historical and geological study was carried. The research into the archives helped us to discover some unpublished documents. They present the initial state ofthe ground and appearance ofthe Square, previously unknown. They gave some valuable indications about the cobblestones (red and black limestones, layout, geometric design ... etc.) and information about the approximate cobblestone quarries. A geological study was necessary to define the nature and origin of the black cobblestones but doubt remains about the real coloured aspect of the red ones. Some chromatic analyses indicate that ali the different red rocks likely to have been used relatively close to the same ochre brown colour. INTRODUCTlON but has since been replaced by a statue of the Polish King and last Duke of Lorraine. 1.1 S/anislas Square origin Listed as a World Patrimony by the UNESCO, Stanis­ 1.2 Res/oration goal las Square was built from 1752 to 1755 by Stanislas Leszczynski, former king of Poland (1677- 1766). To celebrate the 250th anniversary ofthe Square'scom­ It is located south of the Carritire Square between pletion, the urban council ofNancy and its agglomer­ the medieval town and the seventeenth century new ation are undertaking a complete remodelling of lhe town (Pfister 1974). The Square was named Place Square which aims at restoring the original ground Royale until 1792 (French Revolution), to become and the vicinity ofthe Square. The current weight con­ Place Stanislas in 183 I. The Square used to feature the straints used for a public square have to be respected statue of King Louis XV ofFrance, Stanislas' step-son (pedestrian space with some occasional heavy weight Figure I. Actual aspect ofthe Stanislas Square (photography: Town ofNancy). 265 vehic\es passages for special events that demand bleachers or stands, tents, etc.). The Chief Architect at Historical Monuments is supervising the project. A study of the archives has been conducted to prepare the ground restoring project. The aim was to discover documents about the original pavement. Search has to be conducted by a geological study to detail the different aspects and colours of the pavement mentioned in the archives. Figure 2. A view of the Stanislas Square sourced from lhe painting ofPange. (Photography: Town ofNancy). 2 NEW HlSTORlCAL DATA sizes had to be of approximately 0.25 to 0.29 m in length, 0.20 to 0.26 m in width and 0.26 to 0.29 m in Until recently, the official known documents of the high. They couldn't be sensitive to frost. Another doc­ Stanislas Square didn't indicate the use of colour nor ument specifies the use ofa good quality rock without geometric design ofthe pavement. In May 2003, orig­ imperfections particularly the c\ay beddings. inai documents were discovered in the Public Record The cobblestones were carried to the bui lder's yard Office ofNancy (Archives 1755). One ofthese docu­ by the pavers (Archives 1755). Thereafter, the cob­ ments, a quantity survey conducted by the architect blestones were placed on a sand or gravei levei with to pay the pavers reveals the component and the a disposition that allowed for crossed joints. The exact geometric designs of the Square grounds at the pavement was then covered with sand. time of its inauguration. Some contracts agreed with the pavers and the quarrymen gave information con­ 2.4 Remarks abotll this new documentation cerning the origin, the quality and the sizes of the cobblestones. Surprisingly, the documents found in the archives gave new information about the two colours of the pave­ ment and their geometric designs totally ignored by 2. 1 Geometric design ofthe square the official iconography. The pavement was essentially red in colour, underlined Only one painting, which can be seen in the castle with black cobblestones lines. The black cobblestones of Pange (sixteen kilometres to the north of Nancy), were located around the base of Louis XV's statue shows how the cobblestones were installed (Fig. 2) . and along the square lateral gutters. They represented Red and black cobblestones are visible as the black the four diagonais between the corners and the central diagonais that leading to the corners to the statue of statue (Fig. 2). Louis XV This pavement was preserved as far as the French Revolution. A new quantity survey from May 30th 1789 indicated that refection works were neces­ 2.2 Quarries location sary (Archives 1789). They were eventually stopped by Other documents gave a wide range of information the Revolution. The monarchy marks as the statue di s­ about the work order from the quarry to the grounds. appeared in 1792. The first geometric pavement design The stones were ali extracted from less than ten kilo­ to highlight the statue were changed and disappeared metres from the Square. They carne from different from the collective memory ofthe inhabitants. local towns, Art-sur-Meurthe for the black cobble­ stones, Dommartemont, Malzéville, Pixérécourt and Vandoeuvre for the red ones. Today, these sites are too 3 FIRST GEOLOGICAL ARGUMENTATION vast and contain different rocks than the past black and red cobblestones. Special geological investigations 3.1 Nancy geological context will be necessary (refer to below). From a geological point of view, Nancy is located on the eastern fringe of the sedimentary basin of Paris. 2.3 Cobblestones and characteristics ofthe The town and its vicinity grow in a c\ayey dip, sur­ builder s yard mounted by a calcareous table-Iand and its residual hill, respectively to the west and north-east. A river The cobblestones were sized on the quarrying place. lhe Meurthe runs inside the dip not far from Nancy's As shown in an agreement between the architect and city centre. Local stratigraphy (dated from the Juras­ the local paver Jean Maizieres on July 15th 1754 sic period) also shows two blocks. At the bottom the and as found in the archives, the work had to be first layer (geological stages Hettangian-Sinemurian, very precise. Indeed, the layout of the pavement pre­ Pliensbaschian, Toarcian) mainly contains c\ays with scribed a selection of cobblestones in the quarries; a few limestones and sandstones on 250 to 270 metres 266 high. The second layer (geological stages Aalenian Table I. Links between the Archives localities and the and Bajocian) is a continuai succession of severa I geological stages. limestones lithofacies on 120 metres deep. The rocks susceptible to have been used for the pavement have to Stages Petrography Colours Local towns be found in some geological strong sedimentary beds White, grey in exclusion oftoo many clayey materiais. These rocks Mid. Bajocian Limestone Low. Bajocian Limestone Ochre brown must correspond to the initial colours criteria. Histori­ Grey Malzéville cal archives could help us to determine more precisely Aalenian Limestone Red, orange Pixérécourt locations of ancient quarries. Brown Vandoeuvre Green, grey Toarcian Marle 3.2 Colours present in locallithostratigraphy Pliensbaschian MarJe/ Dark grey Sandstones Black ArtIMeurthe In this lithostratigraphy, we can effectively find again Hettangian - MarJous- BJue-ish the different colours described in the historical writ­ Sinemurian caJcareous ten documents. The oldest sedimentary beds from Hettangian-Sinemurian, Pliensbashian and Toarcian contain dark lithofacies of grey, blue-ish and black colours. With the exception of a particular limestone black cobblestones whereas Aalenian andlor lower bank of a I or 2 metres thick, named Calcaires ocreux; Bajocian limestones have furnished red materiais. initially black, it can progressively takes a rusty colour We have to complete these previous indications with with the weather alteration. some field observations to confirm the real aspects of Just above, Aalenian geological stage coincides the two sorts of cobblestones. with the regional iron ore well known as Minette Lorraine and extracted during the nineteenth and the first part ofthe twentieth centuries. Its petrographical 4 PETROGRAPHICAL ASPECTS OF THE aspects and colours do vary. In this geological sedi­ COBBLESTONES mentary beel, shades encountered are caused by iron oxides variation and concentration. They can be grey, 4.1 Black cobblestones green, reei, brown, with many sort of rust or orange The case of the black cobblestones is simple beca use shades (Bubenicek 1961). sedimentary bed Calca ires à Gryphées is the only Above, lower Bajocian allows calcareous rocks still one allowing black or dark grey limestone in the containing a few iron oxides. The shades are there­ local statigraphy. Furthermore, they could be no doubt fore systematically ochre brown, rust or even red about the black cobblestones origin as its presents in with a more or less grey colour adjunction. Local Art-sur-Meurthe, was mentioned in the archives. encrinitic limestone, Calca ires à entroques, is occa­ Today, there isn 't any quarry visible in this local area sionally named red rock, Roche rouge, by quarrymen but archives also mentioned a special tenancy rental and geologists. contract for the purpose of extracting those stones. At the top of the local stratigraphic series, colours The original cobblestones sources was about 30 cm from the middle Bajocian are very different from the cubic and covered approximately 7.5% of the Square previous rocks. Shades are typically white-ish like the (about 850 m2 compared to 11300 m2) representing a white oolite sedimentary beel, Oolilhe blanche, or grey­ total volume of 240 m3 .