Evaluation of Reinforcement Effects According to Reinforcement Type and Grouting Method

지반보강재의 형상과 그라우팅 방법에 따른 보강효과 평가

Abstract

In order to ground reinforcement, the chemical grouting, the anchor, the soil nailing system, the micropile, etc. can be mentioned by the methods widely used in domestic. The above ground reinforcement methods are developed by various methods depending on the type of reinforcement, installation method, presence of prestress, grouting method, etc. However, in common, the strength of reinforcement, the friction force of grout and reinforcement and the friction force of grout and ground are the main design variables. Therefore, the optimized ground reinforcement is a material with a high tensile strength of the reinforcement itself, the friction force between the reinforcement and the grout is high, and the application of an optimal grouting method is necessary to improve the friction force between the grout and the ground. In this study, a total of 20 model tests were conducted to analyze the reinforcement effects according to the shape of the reinforcement and the grouting method. As a result of the test, As a result of the experiment, it is judged that the reinforcing effect is superior to the perforated + wing type reinforcement and post grouting method.

지반보강을 위해 국내에서 널리 사용되고 있는 공법으로 약액주입공법, 앵커공법, 소일네일공법 및 마이크로파일공법 등을 들 수 있다. 이러한 지반보강공법은 보강재의 종류, 설치방법, 프리스트레스의 유무 및 그라우팅 방법에 따라 다양한 공법으로 개발되고 있으나, 공통적으로 지반보강재의 강성, 그라우트와 보강재의 마찰력 및 그라우트와 지반의 마찰력이 주요 설계변수이다. 따라서, 최적화된 지반보강재는 보강재 자체의 인장강도가 큰 재료로써 보강재와 그라우트사이의 마찰력이 크며, 그라우트와 지반사이의 마찰력을 향상시킬 수 있는 최적의 그라우팅 방법의 적용이 필요하다. 이에, 본 연구에서는 보강재의 형상과 그라우팅 방법에 따른 보강효과를 평가하고자 총 20여개의 실내모형실험을 실시하였으며, 실험결과 타공+날개보강형과 포스트그라우팅 방법이 보강 효과가 가장 우수한 것으로 나타났다.

Fig. 1. Classification according to the grouting method

Fig. 2. Model box

Fig. 3. Excavation apparatus

Fig. 4. Pullout apparatus

Fig. 5. View of unconfined compression test of pipe type

Fig. 6. View of unconfined compression test of helical type

Fig. 7. View of unconfined compression test of disk type

Fig. 8. View of unconfined compression test of wing type

Fig. 9. Compressive load between grout and reinforcement bars

Fig. 10. View of unconfined compression test of hole type

Fig. 11. View of unconfined compression test of hole and wing type

Fig. 12. Compressive load with variation of hole type

Fig. 13. Pullout resistance stress according to reinforcement type

Fig. 14. Reinforcement effect according to reinforcement type

Fig. 15. Pullout resistance stress with variation of hole size

Fig. 16. Reinforcement effect according to variation of hole size

Fig. 17. Pullout resistance stress with variation of grouting method

Fig. 18. Pullout resistance stress according to variation of expansion ratio

Fig. 19. Reinforcement effect according to variation of expansion ratio

Table 1. Presumptive average ultimate bond stress for ground/grout interface along bond zone (Sabatini et al., 1999)

Table 2. Characteristics of weathered granite soil

Table 3. Shear strength of weathered granite soil

Table 4. Reinforcement bar

Table 5. Test series