habitat rupestre.pdf - Società Friulana di Archeologia

THE INFLUENCE OF GEOLOGICAL AND GEOMORPHOLOGIC ASPECT IN THE REALIZATION OF ARTIFICIAL CAVESCRHIMA-CINP projectFig. 2 Entrance of the Seiano Cave between Naples and Pozzuoli. Thebreadth of the section is less than 2 meters (photo: N. Damiano).Fig. 3 Bauxite mine, Cusano Mutri –Matese Mountains. The surfacingstratigraphy reveals the mineral level in correspondence of the entrance tothe mine. (photo: F. Allocca, archives S. Del Prete).Fig. 4 Cinnabar mines in the Siele valley, Tuscany. Note the lithologictransition between lithoid rocks (marly limestone with good self supportingcharacteristics) and highly loading clay schist that needs walls coating(photo: S. Del Prete).IntroductionThe culture of subtractive building developed in the centuries,and it was spread all over the world, entwining differentpeople and culture.The realization of underground structures through hand excavationbrought to several typologies of works for differentdestinations.There are many reasons that brought different cultures to developsubtractive techniques and technologies: war (offenceand defence), religious, economical and social reasons. In anycase, the development of real underground cities was stronglyinfluenced by geographical, climate and geological aspects.The geological and morphological assessments played themost important role in the development of underground works.As it regards geological assessment, many factors contributeto the realization of artificial caves and underground settlements(Tab. 1). They can be more or less important dependingon the use of the artificial cave and on the intended benefits.Generally, the presence of tuff outcrops granted for undergroundquarries, from where building stones were extractedfor troglodyte and religious settlements; the location and thedevelopment of mines for the extraction of metal bearing rocksis conditioned by the deposit and the strength of the mineralvein, as well as by the available industrial technologies (forexample, the extraction of Bauxite).During the realization of aqueducts (Ashby, 1935; Bodon etal., 1994) or military corridors (VV. AA., 2005; Gherlizza &Radacich, 2005), the difficulties of excavating harder rocks(limestone, for example) were less important than the goal(bringing water to a town, or realizing strategic post). In thesecases, morphological factors, which are bound to the landscape,affected the courses and the development of the works;for open air aqueducts, variations could be significant (Fig. 1).The excavation difficulties due to lithologic characteristicswere generally balanced out by the realization of cavities withreduced section, though with an important spatial development.Roads needed to overcome the morphological obstacle, andthis led to the realization of tunnels. Ancient Etruscan andRomans were the masters of building narrow tunnels, where asingle file of wagons and horses could pass (Fig. 2).Big underground cavities (especially cisterns and tuff mines)changed frequently destination, turning into manufactories,bomb shelters, underground deposits, cemeteries, etc.Table 1 – Summary table of geological factors that affect the realization, the exploration and the preservation of an artifi cial cave.Geological factorsLithologyLithotechniqueGeotechniqueHydrogeologyMorphologyEndogenic factorsRocky nature (sedimentary, igneous, metamorphic rocks and relative mineralogical characteristics).Geological structure (faults and intersections of faults or of cross cutting folds, bedding, cleavage,folds and mineralization).Physical and mechanical properties of materials (angle of friction, compressive and shearstrength, porosity, permeability, specific weight, alteration, mineralogical composition, geologichistory, geomechanical assessment, etc.), swelling grounds or rock, undermining of bigrock wedges, decompression, and deformation.Groundwater, superficial hydrographical setting (lakes and endorheic basins), springs, acidwaters.Weathering (physical degradation and chemical alteration) and relative morphologies (slope,earth pyramids, pinnacles, butte, mesa, plateau, etc.)Presence of endogenous fluids or explosive and toxic gas pockets, high temperature, bradyseism.volumeRicerca_OK_2012-11-15.indd 20 16/11/2012 15:00:45