This paper presents a computational fluid dynamics (CFD) analysis to investiagate the effect of expansion chamber on overpressure reduction in protective tunnels subjected to detonation of high explosives. A commercial CFD code, Viper::Blast, was used to model the blast waves in a protective tunnel with a length of 160 m, width of 8.9 m and height of 7.2 m. Blast scenarios and simulation matrix were establihsed in consideration of the design parameters of expansion chamber, including the chamber lengths of 6.1 m to 12.1 m, widths of 10.7 m to 97 m, length to width ratios of 0.0 to 5.0, heights of 8.0 m and 14.9 m, and ratios of chamber to tunnel width of 1.2 to 10.9 m. A charge weight of TNT of 1000 kg was used. The mesh sizes of the numerical model of the protective tunnel were determined based on a mesh convergence study. A parametric study based on the simulation matrix was performed using the proposed CFD tunnel model and the optimized shape of expansion chamber of the considered tunnel was then proposed based on the numerical results. Design recommendations for the use of expansion chamber in protective tunnel under blast loads to reduce the internal overpressures were finally provided.

Abstract
1. 서론
2. 방호터널의 확장챔버 설계변수
3. 폭압해석모델
    3.1 CFD 모델링
    3.2 메쉬수렴도 해석
4. 터널의 폭압해석
    4.1 폭발시나리오
    4.2 해석결과
5. 확장챔버의 폭압저감효과
    5.1 확장챔버길이-폭비(Lc/Wc)
    5.3 챔버폭-터널폭비(Wc/Wt)
6. 결론
감사의 글
References

• 신진원(가톨릭관동대학교 건축공학과 교수, 공학박사) | Shin Jinwon (Dept. of Architectural Engineering Catholic Kwandong University)
• 방승기(경민대학교 건축과 교수, 공학박사) | Pang Seungki (Dept. of Architecture, Kyungmin University)