PSI - Issue 28

M.L. Puppio et al. / Procedia Structural Integrity 28 (2020) 330–343 Puppio M.L. et al/ Structural Integrity Procedia 00 (2020) 000–000

335

6

On March 3rd, 2014, also the Etruscan Spur close to Place Martiri della Libertà in Volterra collapsed (Fig. 7). Even earlier than March 2014 the spur presented some problems exacerbated by the heavy rainfall of that period. Some steel tie-rods were pulled to unsuccessfully prevent the overturning of the wall.

Fig. 7. Collapse of the “Ancient Spur” of Volterra, March 2014.

2.5. San Gimignano On April 3rd, 2018, a section of about 20 m of the Medieval walls of San Gimignano (Siena), near Porta Pisana, collapsed without any evident warning sign. Also in this case, the failure occurred after intense rainfalls.

(a)

(b)

Fig. 8. View after the collapse in San Gimignano (a); deep cracks in another critical section (b).

3. Method of survey (GIS data Vs direct measurements) To perform a methodology of structural survey for extensive urban walls ensuring quick and efficient results, it is necessary to evaluate (1) topographical, (2) hydrogeological and (3) structural aspects [5][7]. The topographical condition should evaluate upstream and downstream type conditions and slope of the earth. The hydrogeological condition refers to water infiltrations and ineffective draining. Soil saturation determines a double effect: (i) the growth