ABSTRACT:

Understanding of EDZ formation, properties and significance has increased recently. EDZ has been evaluated as long term safety issue in spent nuclear fuel disposal. The objective of the study was to characterize EDZ in varied blasting designs. D&B excavations were performed using emulsion explosive Kemiitti 810. GPR EDZ method was used in measuring EDZ extent. Five blasting rounds were excavated in crystalline rock. Blasting and geology relates studies were performed along the visual inspections. The difference in EDZ extend was almost nonexistent. Emulsion explosive Kemiitti 810 with nominal charge 400 g/m is suitable for sites requiring maximum EDZ extent of 400 mm. The GPR EDZ results were well in line with visual inspections. NDT method is suitable in EDZ extend definition. Formed EDZ has safety and economical perspective in mining and civil construction as well. Future investigations concentrates on time evolving EDZ due to rock mechanical pressure in the underground facility.

1 INTRODUCTION

Excavation Damaged Zone (EDZ) has been noticed to have impact to underground construction work as well as working safety. Overall understanding of the EDZ formation, properties and significance has increased recently. Posiva Oy and Swedish Nuclear Fuel and Waste Management Co (SKB) as well as other companies involved in spent nuclear fuel disposal research have evaluated the EDZ as a long term safety issue. Various testing methods in EDZ investigation has been tested and evaluated. Series of studies have been made to characterize and evaluate the significance of the EDZ.

This project named as LOVA was designed by group of companies working in excavation related field. Project participants are Posiva Oy (Posiva), Swedish Nuclear Fuel and Waste Management Co (SKB), Oy Forcit Ab (Forcit), Sandvik Mining and Construction Oy (Sandvik), EDZ-consulting AB and Geofcon as project leader. All of the participants bring different expertise to the project crew.

The objective of this project was to characterize EDZ in varied drill and blasting (D&B) blasting designs applying Kemiitti 810 emulsion explosive by Forcit. Ground Penetrating Radar (GPR) based GPR EDZ method was the central tool in measuring the EDZ extent.

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