MASTERPIECES IN THE LOUVRE (PARIS, FRANCE) AS ANALOGUE MODELS FOR JOINT PROPAGATION

Masterpieces including those by Rembrandt, da Vinci, and David in the Louvre (Paris, France), like bedded sedimentary rocks, are jointed (i.e., cracked) composite materials with welded contacts between substrate and joint-bearing medium. The analogy goes even further because differences in properties between the substrate and the joint-bearing medium greatly influence a number of characteristics of the joint growth pattern including spacing, orientation, abutting, propagation direction, and degree of systematic development. In particular, the degree to which the joint-bearing medium is subject to ‘tectonic' stress predetermines the extent to which a number of these joint patterns develop. Regardless of the particulars, it is clear that the masterpieces and sedimentary rocks even share a common loading configuration (i.e., thermoelastic) under fixed-grips conditions (i.e., Engelder and Fischer, 1996). When ‘tectonic' stresses are not present mudcracks, columnar joints, and spiral joints propagate under thermoelastic loading. In the masterpieces, ‘tectonic' stresses arise from the way the substrate was stretched, dried, or woven and these stresses are responsible for controlling the orientation of systematic joints again under thermoelastic loading. Systematic joints may fan or curve if the substrate provides local stress concentrations (i.e., Rawnsley et al., 1992). Preparation may also cause the substrate to deform in oroclinal-like bends as indicated by concomitant jointing in the host medium (i.e., Engelder and Geiser, 1980). Cross joints are less systematic and, hence, the role of tectonic stress is less clear (i.e., Gross, 1993). Finally, joint (i.e., crack) growth in the masterpieces is consistent with subcritical propagation much like joints in sedimentary rocks (i.e., Savalli and Engelder, 2005).