Unexpected “Liquefaction-type” Behavior of Fine-grained Soils During the 1999 Kocaeli EQ:

1. Unexpected “Liquefaction-type” Behavior of Fine-grained Soils During the 1999 Kocaeli EQ: Carrefour Shopping Center J.R. Martin II, C.G. Olgun – Virginia Tech

2. Carrefour Shopping Center (~0.24g)

3. Carrefour Shopping Center – Typical Soil Profile:

4. Carrefour Shopping Center – Conditions During 1999 EQ: 50 m 50,000 m2 Jet Grouting completed; Building under construction Shopping Center Building 3.3-m surcharge fill in place; settlements being monitored at three locations Proposed Parking Garage Jet Grouting just beginning here Lot C SE-1 SE-3 SE-2

5. Surcharge Fill in Lot C and Settlement Monitoring: ~ 100 m

6. Settlement Monitoring in Lot C: Fill Settlement column schematic R-1 R-2 R-3 R-4 R-5 R-6 Fixed

7. (CH) (CH) (CH) (all ΔH’s occurred in < 24 hrs.) (ML/CL w/SP-SM) (ML/CL) w/ GC

8. Summary of Index properties: * Meets Chinese criteria, except for clay content (>15%); ** CH may be slightly sensitive.

9. Making sense of the measured settlements: • Are the settlement data “real” or erroneous? • How could settlements have occurred so quickly (< 24 hrs.) in these saturated fine-grained soils? • Were settlements due to constant-volume shearing distortion and lateral bulging, etc. due to the overlying fill? • What happened at neighboring sites? Also, is there precedent for this behavior?

10. Preliminary Numerical Modeling of Fill Settlements: (Colors indicate areas of higher strains) Vertical strain Lateral strain Shear strain

11. Significant Stiffness/Strength Degradation in ML/CL and CH Strata Appears to Explain Observations:

12. Predicted Fill Settlement Due to Stiffness Degradation: Original shape (pre- earthquake) Deformed shape (post-earthquake)

13. Soils Were Heavily Loaded Due to Earthquake Loading Combined With Driving Shear Stress (Fill):

14. Similar Behavior at Adjacent Loaded Sites: 10 to 15 cm settlement • Some bulging, but no sand boils

15. Summary and Preliminary Thoughts: • During design, the ML/CL and CH soil strata at Carrefour were not considered susceptible to “liquefaction-type” or significant strain-softening behavior • Soils heavily loaded by M7.4 earthquake • Surprisingly, settlements corresponding to almost 1% vertical strain occurred in ML/CL and CH strata beneath 3.3-m fill during M7.4 earthquake • Observed settlements appear to be free of instrument malfunctions

16. Summary and Preliminary Thoughts: • Adjacent structures on similar soils settled in similar manner • Preliminary numerical modeling suggests settlements can be explained by significant stiffness/strength degradation in ML/CL and CH • Thus, results imply that the ML/CL and CH soils at Carrefour and vicinity are susceptible to significant stiffness degradation • Mechanism appears to be mainly strain softening under driving shear stress

17. Summary and Preliminary Thoughts: • ML/CL soils appear to be similar to those associated with ground failures in Adapazari (Bray et al., 2001) • ML/CL soils would be considered liquefiable by Chinese criteria, except for clay content criterion • CH soils are suspected to be at least slightly sensitive • Field and laboratory tests to be performed on these Carrefour soils in early Spring 2004. Stay tuned! • This type of field measurement appears unprecedented

18. Planned Tests on Soils at Carrefour Site: • Field vane shear • Monotonic loading triaxial tests on undisturbed samples • Monotonic loading triaxial tests, followed by dynamic cyclic loading • Cyclic simple shear • Numerical modeling/analytical work

20. Carrefour Shopping Center – Site Plan Site is 50,000 m2

22. M7.4 Kocaeli Earthquake – Carrefour Site

23. Settlement column … R-1 R-2 R-3 R-4 R-5 R-6

24. vertical strain

25. Deformed Shape Due to Stiffness Degradation: Original shape (pre- earthquake) Deformed shape (post-earthquake) • Implication of numerical analysis both the ML/CL • and CH soils may be susceptible to significant • strength/stiffness degradation

26. horizontal strain