Turan Karadayılar’s research while affiliated with University of California, Berkeley and other places

Ground failure in Adapazari, Turkey during the 1999 Kocaeli earthquake (Mw=7.4) was severe. In four central downtown districts, where more than 1200 buildings collapsed or were heavily damaged, hundreds of structures tilted and penetrated into the ground due in part to liquefaction and ground softening. Based on a multi-institutional subsurface investigation program, soil conditions along four lines in which ground failure was surveyed after the earthquake are classified into four generalized subsurface site categories. This classification is primarily based on the presence or absence of shallow and intermediate depth liquefiable soils. Observations of ground failure are found to correlate well with site categories that are susceptible to liquefaction according to current state-of-the-art methods without strict adherence to the Chinese criteria. Soils that liquefied were found to meet the liquid limit and liquidity index conditions of the Chinese criteria. However, soils that liquefied did not typically meet the clay-size condition for liquefiable soils by the Chinese criteria.

Deep excavations and retaining structures are constructed in the city of Istanbul at different locations of the city due to the recent demand for the construction of high-rise structures and shopping malls having various basements. The main lithological unit of Trace Formation, i.e. alternating layers of sandstone, siltstone and claystone are encountered during these excavations. The lithological unit is extensively fractured. Conse- quently, stress relief in horizontal direction as a result of excavations is the main potential hazard that has to be handled with care. Istanbul is located at a very seismically active region and a major earthquake magni- tude of Mw>7.0 are expected to occur with a 65% probability within the next 30 years. It is well known that flexible earth retaining structures in cuts as soil nailed walls offer a great advantage under the described sub- soil and seismic conditions. As a result many soil nailed walls having various heights have been constructed recently in the city. The performances of these walls are monitored by means of inclinometers. The dis- placement data for various projects are evaluated in terms of various design parameters of the soil nailed walls and the excavation depth. In the paper the basic guidelines for soil nailed walls in typical greywacke formation of the city are developed for future applications.