PURPOSES: The purpose of this study is to evaluate and improve the potential risk of road cave-ins due to subsurface cavities based on the deflection ratio measured with light falling weight deflectometer (LFWD) tests.
METHODS : A cavity database for Seoul was developed and sorted. LFWD tests based on the database were conducted on pavement sections with and without road cavities detected by ground-penetrating radar (GPR) tests; after excavating the area, the cavity sizes were measured. The deflection ratio was applied and analyzed by cavity management grade methods of Japan and Seoul.
RESULTS : The results of comparative analysis show that the deflection method can detect road cavities in areas of the narrow road (or in narrow areas of the road). The average deflection ratio of the cavity sections to the robust sections were 2.48 for high-risk cavities, 1.85 for medium-risk level cavities, and 1.49 for low-risk cavities. Risk levels in Japan and Seoul were reclassified according to the deflection ratios.
CONCLUSIONS : LFWD test results can be applied to verify and improve the subsurface cavity risk level by comparing maximum deflection and deflection ratio between cavity area and non-cavity area at the loading center. LFWD devices also have more advantages compared with larger NDT(Nondestructive test) because FWD and GPR encounter difficulties in traffic control and they could not get in a narrow roads.

ABSTRACT
 1. 서론
 2. 기존 연구 및 문헌고찰/국내외 동향 조사
  2.1. 국내연구
  2.2. 국외연구
 3. 서울시 도로동공 DB(Database) 구축
  3.1. 도로동공 DB 프로그램
  3.2. DB를 활용한 동공관리 인자의 영향분석
 4. 처짐비를 활용한 도로함몰 위험도 평가 개선 방안 개발
  4.1. LFWD장비의 사용적정성 검토
  4.2. 현장조사 시험결과 분석
  4.3. 처짐비를 이용한 동공관리등급 개선
 5. 결론
 REFERENCES

• 김경수(인덕대학교 산학협력단) | Kim Kyung soo
• 최준성(인덕대학교 토목환경공학과) | Choi Junseong 교신저자
• 윤진성(서울특별시 안전총괄본부 도로관리과) | Yoon Jin-sung