Subsurface Characterization at Ground Failure Sites in Adapazari, Turkey

Abstract

Ground failure in Adapazari, Turkey during the 1999 Kocaeli earthquake was severe. Hundreds of structures settled, slid, tilted, and collapsed due in part to liquefaction and ground softening. Ground failure was more severe adjacent to and under buildings. The soils that led to severe building damage were generally low plasticity silts. In this paper, the results of a comprehensive investigation of the soils of Adapazari, which included cone penetration test ͑CPT͒ profiles followed by borings with standard penetration tests ͑SPTs͒ and soil index tests, are presented. The effects of subsurface conditions on the occurrence of ground failure and its resulting effect on building performance are explored through representative case histories. CPT-and SPT-based liquefaction triggering procedures adequately identified soils that liquefied if the clay-size criterion of the Chinese criteria was disregarded. The CPT was able to identify thin seams of loose liquefiable silt, and the SPT ͑with retrieved samples͒ allowed for reliable evaluation of the liquefaction susceptibility of fine-grained soils. A well-documented database of in situ and index testing is now available for incorporating in future CPT-and SPT-based liquefaction triggering correlations.

CPTu Simplified Stress-Based Model for Evaluating Soil Liquefaction Potential

“…To this end, it is of interest to demonstrate this capability by back-analysis of well documented case histories from the August 17, 1999 Kocaeli earthquake that involved soils considered to be``too clay-rich to liquefy.'' An extensive site investigation program, including 135 CPT proˆles and 46 exploratory SPT borings with energy measurements, was conducted in Adapazari, Turkey after the Kocaeli earthquake (Bray et al, 2004). All available CPTu sounding proˆles were analyzed in this study and similar results were obtained.…”

“…These cases were derived from the 1964 Niigata, Japan earthquake (Mw＝7.5), the 1976 Tangshan, China earthquake (Mw＝8.0), the 1977 Vrancea, Romania earthquake (Mw＝7.2), the 1979 Imperial Valley, California earthquake (M w ＝6.5), the 1980 Mexicali, Mexico earthquake (Mw＝6.2), the 1983 Borah Peak, Idaho earthquake (Mw＝6.9), the 1987 Edgecumbe, New Zealand earthquake (Mw＝6.6), the 1987 Elmore Ranch, California earthquake (Mw＝6.2), the 1987 Superstition Hills, California earthquake (M w ＝6.6), the 1989 Loma Prieta, California earthquake (Mw＝7.0), the 1995 HyogokenNanbu, Japan earthquake (Mw＝7.2), the 1999 Chi-Chi, Taiwan earthquake (Mw＝7.6), and the 1999 Kocaeli, Turkey earthquake (Mw＝7.4). The binary criterion of liquefaction/no-liquefaction was primarily based on surface manifestation of liquefaction, such as sand boils, ground settlement, and lateral spreading (or lack thereof), and in some cases (such as those reported by Bray et al, 2004), critical layers were identiˆed byˆeld observations supplemented with detailed dynamicˆnite element analyses or conˆrmed by multiple existing liquefaction evaluation methods. Figure 1 shows the soils in these cases in the soil behavior type classiˆcation chart.…”

“…Two sets of CPTu sounding proˆles along with results of the analysis are presented as examples. Figure 13 shows the proˆles from CPTu sounding C4 which was conducted at the site of Building C2 (Bray et al, 2004). Included in thisˆgure are qt, Rf, u2 (or Pw), Ic, RW, Ic, and soil classiˆcation as per an adjacent soil test boring.…”

“…Included in thisˆgure are qt, Rf, u2 (or Pw), Ic, RW, Ic, and soil classiˆcation as per an adjacent soil test boring. The critical layer marked in thisˆgure is one that was judged to have liqueˆed in the 1999 earthquake by Bray et al (2004) based onˆeld observations and analysis of in situ test data. The layer marked with``FSº1'' is the layer that was considered liqueˆable by Bray et al (2004) based on their analysis.…”

“…This concept is re‰ected in the three boundary curves corresponding to three ranges ofˆnes content (FCÃ5z, 5zºFCÃ35z, and FCÀ35z) recommended by Seed et al (1985), which has been well accepted by the profession. However, liquefaction of soils with highˆnes content (as high as 90z) in the past earthquakes has been observed (Kishida, 1969;Tohno and Yasuda, 1981;Bray et al, 2004). Laboratory cyclic simple shear tests, cyclic ring-shear tests, and cyclic triaxial tests of these soils (for example, Ishihara, 1993;Perlea et al, 1999;Guo and Prakash, 1999;Gratchev et al, 2006) suggest that the soil plasticity, and not necessarily theˆnes content alone, plays a major role in the liquefaction resistance behavior, i.e., the liquefaction resistance increases as the plasticity index increases.…”