The main structure of the Poligon station, which is situated on route of Ü çyol-Ü çkuyular line as part of Izmir subway development works consists of diaphragm wall. Under the diaphragm wall, a tunnel is planned for docking the train to the station. Several old buildings with 8–10 stories are located near by the station structure. Many of which are not suited to new earthquake legislation. Condition of bed of tunnel is an alternation of claystone and sandstone, which consist of very weak and very strong units. Therefore, fore-support design was realized in this highly complex work environment in order to save the construction equipment and re-excavate T2 tunnel without damaging the structure of the station, substructure and surrounding buildings. In general, design system proposed here includes classical support systems, chemical injection and micro-cement injection. In this study, field studies for cross-failure at Izmir Subway Poligon Station, measurements, assessments, excavation and support design, which are suggested to re-excavate T2 tunnel are explained in detail.

1 Introduction

In the design of underground openings in soft ground, reinforcement such as shotcrete, rock bolts, concrete cementing, steel support, etc. Are specifically established after a certain delay that require short-to-medium term pre-stress and strain calculations. This also relates to the prediction of potential damage on the buildings in the influence area of subway tunnel excavations.

During the development works of Izmir Metro Project, T2 tunnel collapsed on March 21, 2012 near Poligon Metro Station, which is located on the route of Ü çyol-Ü çkuyular line and a work machine was buried in the rubble. A project was carried out to re-excavate the T2 tunnel and save the work machine without damaging the infrastructure of the station building in this rather complex environment which exhibits diaphragm walls, old buildings etc.

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