PURPOSES: The objective of this study is to evaluate the structural capacity of asphalt pavement in subsurface cavity sections using falling weight deflectometer (FWD) backcalculation method.
METHODS: It is necessary to analyze the reduction of structural capacity in asphalt pavements due to the occurrence of subsurface cavities. The FWD testing was conducted on the cavity and intact asphalt pavement in the city of Seoul. The GAPAVE, backcalculation program for FWD deflections, was utilized to determine the layer moduli in asphalt pavements. The remaining life of asphalt pavements in cavity sections were predicted using the pavement performance model for fatigue cracking. The backcalculated layer moduli between cavity and intact sections were compared to determine the reduction of structural capacity due to subsurface cavity. The relationship between the reduction of layer modulus and cavity depth/length was analyzed to estimate the effect of cavity characteristics on the structural capacity degradation.
RESULTS: According to the FWD backcalculation results, the modulus of asphalt layer, subbase, and subgrade in cavity sections are generally lower than those in intact sections. In the case of asphalt layers, the backcalculated modulus in cavity section was reduced by 50% compared to intact section. A study for the prediction of remaining life of cavity section shows that the occurrence of subsurface cavity induces the decrease of the pavement life significantly. It is found that there is no close relationship between the backcalculated modulus and cavity length. However, the reduction of asphalt layer modulus is highly correlated with the cavity depth and was found to increase with the decrease of cavity depth.
CONCLUSIONS : This reduction of structural capacity due to the occurrence of cavities underneath asphalt pavements was determined using FWD backcalculation analysis. In the future, this approach will be utilized to establish the criteria of road collapse risk and predict the remaining life of cavity sections under numerous varied conditions.

ABSTRACT
1. 서론
2. 현장 GPR 및 FWD 시험
3. FWD 역산 프로그램
4. 동공구간 아스팔트 포장 FWD 처짐값 분석
5. 동공구간 아스팔트 포장체 역산 탄성계수분석
6. 동공구간 아스팔트 포장의 잔존수명 산정
7. 역산탄성계수와 도로동공 특성간의 상관성분석
8. 결론
REFERENCES

• 박희문(한국건설기술연구원 인프라안전연구본부) | Park Hee Mun (Research Fellow Korea Institute of Civil Engineering and Building Technology) 교신저자
• 최연우(서울특별시 도로관리과 도로관리팀장) | Choi Yeon Woo