Geo-engineering characterization and an approach to estimate the in-situ long-term settlement of a peat deposit at an industrial district


Ozcan N. , ULUSAY R. , IŞIK N. S.

ENGINEERING GEOLOGY, cilt.265, 2020 (SCI İndekslerine Giren Dergi) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 265
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1016/j.enggeo.2019.105329
  • Dergi Adı: ENGINEERING GEOLOGY

Özet

Peats, which have high compressibility, considerably high water content and low shear strength, are often unsuitable for supporting structures of any kind since they mainly cause excessive and differential settlement and slope instability problems. Peats cover about 8 % of the earth's land surface and particularly are common in Canada, Russia, Malaysia and Indonesia, while Turkey has limited areas of peatland when compared to these countries. However, some of the peatlands in Turkey are located at or close to settlement areas and cause some structural damages. One of the well-known peatlands in Turkey is found in the Ambarkoy district of Kayseri city where two large industrial districts were constructed on the peat and evidences of excessive settlement on some buildings are clear. By considering the lack of geomechanical behavior of the peats and the presence of some settlements next to peaty areas in Turkey, and the ground problems associated with settlement of some structures founded in the above mentioned rapidly growing industrial region, this study has been carried out. This study aims to assess compression characteristics of these peats and to develop an approach for the prediction of in-situ settlement based on the laboratory experiments and field monitoring conducted on these peats. For these purposes, in order to investigate the in-situ characteristics of the peat deposit, boreholes were drilled, trial pits were excavated and seismic surveys were carried out and long-term field settlement was monitored from an externally loaded concrete platform which was constructed on the peat. In the second stage of the investigation; mineralogical, some index and compression characteristics of the peat samples collected from the site were determined in laboratory. The compression process of the investigated peat realized in three stages, namely primary consolidation and secondary and tertiary compressions. The primary consolidation of the peat has been completed shorter than one minute under normal stresses smaller than 54 kPa and its secondary compression indices showed an increase in a non-linear trend. The results of the back-analysis, using the average values of laboratory determined compressibility characteristics of the peat, indicated that the calculated settlement was greater than that measured from the monitoring platform. This was due to that the idealized compressibility parameters, which have been determined from the laboratory tests, correspond to a stress level greater than those imposed by the monitoring platform onto the peat. By considering this, back-analyses based on the use of the compression characteristics, which were re-evaluated, yielded amount of settlements consistent with those measured in the field from the monitoring platform. Therefore, it is suggested that the amount of settlement can be more precisely estimated if the compression characteristics of the peat are re-evaluated and used in the analyses by following the approach suggested in this study.