Tünellerde Kullanılan Püskürtme Beton Kalitesini Etkileyen Agrega Özellikleri


Thesis Type: Postgraduate

Institution Of The Thesis: Kocaeli University, Mühendislik Fakültesi, Jeoloji Mühendisliği, Turkey

Approval Date: 2021

Thesis Language: Turkish

Student: Ercan Güngören

Consultant: Özkan Coruk

Abstract:

INVESTIGATION OF AGGREGATE PROPERTIES AFFECTING SHOTCRETE PROPERTIES USED IN TUNNELS

One of the main problems that arise in the application of shotcrete, whose area of ​​use is increasing, is that the shotcrete does not adhere to the applied surface or to the previously sprayed layers. Rebound (bounce) this non-adherent concrete generally cannot be used.  This material, which bounces during the application of shotcrete, has negative effects on the environment and economy.  In this study, the effect of aggregates with different characteristics on the rebound and shotcrete quality in shotcrete was investigated in order to minimize the amount of rebound.  Engineering properties of aggregates affect the strength of shotcrete, the amount of cement and chemical additive used. Therefore, the mineralogical and petrographic structure and physical and mechanical properties of aggregates should be well known. Since all these properties significantly affect the performance and durability of the concrete, it is inconvenient to make any investments without determining the compliance of the produced aggregates to the standards.

For this purpose, the effects of aggregates of different origin used in shotcrete on the quality of shotcrete were investigated in the Sapanca-Geyve High Speed ​​Train Line T2 Tunnel project.  In the study, experiments were carried out to determine the engineering properties of limestone and dolomite based crushed stone and stream aggregate. The rebound amounts and proctor penetrometer values ​​of the shotcrete produced with these aggregates were determined in the field. During the application, the test was made and the strength of the prepared core samples was determined.  Thus, the usability of the aggregates in the concrete mixture produced for all types of aggregates, the strength and rebound amounts in the concrete were determined.

According to the test results, the initial hardness, setting time and strength values ​​required in shotcrete concretes produced from limestone and dolomite aggregates were reached. The strength and setting time of the concrete produced with stream material are below the limit values. When all results are evaluated, it is determined that aggregate properties affect the shotcrete quality and control the project cost.  In order to meet the project criteria, materials had to be procured from relatively distant crushed stone quarries.

Keywords: Railway, Infrastructure, Shotcrete, Aggregate.