PURPOSES: This study developed a new backfill method for mini trenching. The purpose of this study is to evaluate the performance of the new backfill method in the field.
METHODS: In this study, asphalt pavement was created to verify mini trenching. Trenching test sections were then made in various trench widths in the asphalt pavement. The trench widths were 10 cm, 15 cm, 20 cm, and 25 cm. For the trenching test section, a general backfill method and new backfill method (2-layer SCB) were devised and applied. To evaluate the test section, a vehicle loading test and FWD (falling weight deflectometer) test were performed.
RESULTS : In the vehicle loading test, the duct vertical strain of the general section was up to 22 times larger than that of the 2-layer SCB section. According to the results of the FWD test, the D0 deflection of the 2-layer SCB section was smaller than that of the general section. These results indicate that 2-layer SCB has a good structural performance. With the use of FWD data, BLI (base layer index) and MLI (middle layer index) were analyzed. BLI is an indirect index for evaluating base layer. The BLI of the 2-layer SCB section was smaller than that of the general section, because the bottom layer (cellular mortar) of the 2-layer SCB is superior to that of the general section. MLI, on the other hand, is an indirect index for evaluating subbase layer. As the trench width increases, MLI increases. The MLI of the 2-layer SCB section was smaller than that of the general section. These results indicate that the damage is relatively greater when the trench width increases and that the 2-layer SCB strengthens a relatively weakened subbase. CONCLUSIONS: In this study, the performance of the 2-layer SCB was analyzed. The results of the study showed that good performance was obtained when 2-layer SCB was applied to a mini trenching section.

ABSTRACT
1. 서론
2. 마이크로/미니 트렌칭
    2.1. 마이크로/미니 트렌칭 정의
    2.2. 미니 트렌칭 시공방법
3. 미니 트렌칭용 되메움 방법 개발
    3.1. 2-Layer SCB(self compacting backfill)개발
    3.2. 하부층용 Cellular Mortar
    3.3. 상부층용 자가다짐 아스팔트 혼합물(SLAM)
4. 시험시공 및 성능평가
    4.1. 시험단면
    4.2. 관로 성능평가
    4.3. 차량하중재하시험
    4.4. FWD 재하시험
5. 결론
REFERENCES

• 전성일(한국건설기술연구원 노후인프라센터) | Jeon Sung IL
• 양성린(한국건설기술연구원 인프라안전연구본부) | Yang Sung Lin
• 노재면(한국건설기술연구원 인프라안전연구본부) | Roh Jae Myun
• 이문섭(한국건설기술연구원 인프라안전연구본부) | Lee Moon Sup 교신저자