Assessment of dynamic site response of the peat deposits at an industrial site (Turkey) and comparison with some seismic design codes

Peat is an organic soil type with properties of high compressibility and high water content. Peat deposits are often unsuitable for supporting structures of any kind due to their susceptibility to cause a number of geo-engineering problems, such as settlement, slope instability and soil amplification. There are peatlands in Turkey, although these are not so extensive as in other countries, such as Canada, where peatlands are very common. One of the peat deposits in Turkey is located close to the city of Kayseri (Central Anatolia), and industrial structures have been built on these deposits. This paper focuses on one part of a comprehensive research project conducted by the authors on various geo-engineering aspects of the peat deposits in this industrial site, with the main aims to investigate and assess some of the dynamic properties of the peat deposits in this area, to determine and assess their seismic site response and to compare them with the design spectra recommended in the current seismic codes of Turkey and Europe. In the study shear wave velocities of the peat deposits were determined with seismic measurements, and some dynamic properties of the peat were obtained from the resonant column and torsional shear tests. Then site response analyses were carried out and the results were compared with the design spectra recommended for loose-soft soils by the Turkish Seismic Design Codes and European Construction Design Codes. The comparisons suggest that the response spectra of the investigated peat deposits are greater than those recommended in the Turkish Seismic Codes and that at periods of > 0.3–0.5 s the peat will cause an increase in amplification. Although the response spectra of the peat tested show a better agreement with those recommended in the European codes, they show differences at periods of > 1 s.