9oct 2 bretschneider-a physically based scale

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9oct 2 bretschneider-a physically based scale

  1. 1. A PHYSICALLY-BASED SCALE APPROACH FOR THE ANALYSIS OF THE CREEP PROCESS INVOLVING MT. GRANIERI (SOUTHERN ITALY) A. Bretschneider1, R. Genevois2, S. Martino3, A. Prestininzi3, G. Verbena4 French Institute of Science and Technologies for Transport, Development and Network – Nantes, France University of Padua – Department of Geosciences – Padua, Italy 3 Sapienza University of Rome, CERI Research Centre and Dept. of Earth Sciences – Rome, Italy 4 Tecnostudi Ambiente s.r.l. Professional Company – Rome, Italy 1 2
  2. 2. OBJECTIVES AND METHODS Uniaxial creep tests
  3. 3. OBJECTIVES AND METHODS Creep tests on rock samples of Mt. Granieri - Dimensions (geometrical scaling) - Stress level - Duration of the creep process (time scaling) Real case: DSGSD Mt. Granieri
  4. 4. CASE STUDY 1000 m asl 200 m asl
  5. 5. Double crest Trench
  6. 6. Fiumara Allaro Mt. Granieri WSW ENE Metamorphic complex (Schists) Thermometamorphic contact belt Granitic complex
  7. 7. Mt. Granieri WSW Strath terraces correlated to: - geomorphological data on Serre massif et Aspromonte - marine terraces (after Miyauchi et al., 1994) ENE III order  ~1000ka IV order  ~ 950 ka V order  ~ 900ka VI order  ~ 400ka VII order  ~ 300ka
  8. 8. CREEP TESTS Sample 1 2 3 n (kN/m3) 26.2 26.7 25.6 c (MPa) 119.2 123.5 66.8 4 (Genevois & Prestininzi, 1979) 25.4 56.5 5 26.1 92.1 (Pa∙s) Ia (%) 11 13 11 25 10 55 1.7×10 1.4×10 6.3×10 10 44 11 36.9 8.2×10 1.1×10 Ia% = (altered feldspar/total feldspar)*100
  9. 9. UPSCALING RATIOS Dimensions: L* = Lmodel/Lprototype ≠1 Density: * = model/ prototype ~1 Gravity: g* = gmodel/gprototype =1 Viscosity: * = model/ prototype Example of upscaling procedure - medium alteration level - specimen length upscaled to 50 m ≠1 Strain rate: ˙* = ˙model/ ˙prototype ≠1 Time : t* = 1/ ˙* Laboratory Considering 3 different geometrical ratios… 5,4 cm 50 m 150 m 300 m (kg/m3) g (m/s2) L (m) Ratio 2610 2665 0.98 9.81 9.81 1 0.054 50 1.08×10-3 1.06×10-3 (Pa) . …and the corresponding stress ratios Slope (Pa∙s) (1/s) t (s) 1.1×1011 2.68×1021 4.14×10-11 3.91×10-8 2.55×107
  10. 10. Ia (%) t* for 50 m depth t* for 150 m depth t* for 300 m depth 13 3.35×107 1.12×107 5.58×106 25 4.15×107 1.38×107 6.91×106 37 2.55×107 1.72×107 8.60×106 44 6.73×107 2.24×107 1.12×107 55 8.83×107 2.94×107 1.47×107
  11. 11. Creep curves for sample 5 (medium alteration) Three levels of stress (scaling ratios)
  12. 12. CONCLUSIONS General facts i. ii. This type of analysis can be useful for a zonation of the DSGSDs (stress criterion) Can be useful when using monitoring data (time criterion) Case history facts iii. Tertiary-creep deformations of Mt. Granieri due to the highly altered portion of granites iv. Demostrate that deformations of the portion of the slope located a few hundred of meters from the valley bottom are dependent on a secondary creep stage.
  13. 13. Thanks for your kind attention Slide?!?

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