Adapazarı zeminlerinin geoteknik özellikleri

Abstract

ÖZET Anahtar Kelimeler: Türkiye, Marmara Bölgesi, Adapazarı, Sıvılaşma, Taşıma Gücü, Kayma Direnci, Veri Tabam, CBS, Zemin Haritaları, Jeomorfoloji, Menderesli Nehir Çökelleri, Fasiyes, Alüvyon, Fluviyal, Hasar. Sakarya Üniversitesi, Fen Bilimleri Enstitüsü, İnşaat Mühendisliği Anabilim Dalı, Geoteknik Programında doktora tezi olarak hazırlanan bu çalışmanın amacı; Adapazarı kent merkezi örneğinde olduğu gibi fluviyal karakterli derin aluviyal zeminlerin jeomorfolojik özelliklerini ortaya koymak ve bu çökel sistemi içinde farklı fasiyesleri birbirinden ayırmaktır. Araştırmanın diğer bir amacı ise ayırtlanan bu farklı fasiyeslerin zemin özelliklerinin geoteknik açısından irdelenmesinden oluşmaktadır. Çalışma konusu olan Adapazarı kent merkezi zemin özelliklerini açıklamakla; Adapazarı zeminlerinin oluşum mekanizmaları, sütlerin sıvılaşma yeteneği, depremde meydana gelen hasar dağılımlarında zemin haritalarının etkisi gibi konulara ışık tutulacak, gelecekte sağlıklı yapılaşmaya katkıda bulunulacaktır. XIII

GEOMORPHOLOGICAL AND GEOTECHNICAL PROPERTIES OF ADAPAZARI SOILS SUMMARY Keywords: Turkey, Marmara Region, Adapazarı, Liquefaction, Bearing Capacity, Shearing Resistance, Database, GIS, Soil Maps, Geomorphology, Meandering River Deposits, Facies, Alluvium, Fluvial, Damage. This thesis has been prepared in partial fulfilment for the degree of Doctor of Philosophy in the Department of Civil Engineering of the Graduate School of Sakarya University. Adapazarı, a city of 200.000 people in the Northwestern part of Turkey is unique due to several aspects. The city founded on alluvium with an estimated thickness of 1000 meters deposited by the River Sakarya during the past 7000 years which now flows along the eastern limits of the city. The alluvium has been deposited along the banks of moderately fast flowing streams, as sediments from almost annual flooding, as well as deposits in lakes and marshes. There is also evidence in the form of sand and gravel bedloads to convince the investigator that a `large alluvial river` has dissected the current city in the past. This whole process has created a highly variable soil profile. The silts and silty sands in the top 5 m have been observed to liquefy and together with the low to medium plasticity clays, possess low bearing capacity. The groundwater table is never lower than 3 m, occasionally surfacing during spring. Another interesting feature of Adapazarı is its proximity to the North Anatolian Fault (8 km) which generates M>7 earthquakes almost every decade. Heavy loss of life and widespread damage was caused by the 1999 earthquakes that lasted over 40 seconds. Current location of the city was condemned by the authories and areas of resettlement were created to move the residents northwards, on the hills. The aim of this thesis is primarily to evaluate the ground conditions in Adapazarı in order to prepare a usable geotechnical map of the city. 626 boreholes and 289 cone penetration tests were performed in collaboration with the University of California and relevant testing was performed at the Sakarya University laboratories. All other avaliable data was disregarded as they were not judged as reliable. The fluvial geomorphology of the city is discussed in detail and a relationship between different facies and soil profile is given. A lengthy discussion on the liquefaction of the silts is presented and `Adapazarı Criteria` are proposed. Layer maps for groundwater level, soil types, organic content, SPTNöo, liquefaction potential, undrained shear strength and allowable bearing capacity have been prepared for depths down to 15 m and a database for the city has been initiated. It is concluded that previous studies done in a haste do not represent the actual ground conditions in the city, especially regarding ground failure and it is possible to erect tall structures in certain parts with correct foundation systems. The widespread damage observed during the 1999 earthquake can largely be attributed to inferior structural design and substandard materials, as well as the low performence of the soils. XIV