인발시험을 통한 Spiral bolt의 지보 특성

Abstract

There is support system which keeps unstable massive slopes or rock structures balanced ; like anchor bolt, rock bolt and spiral bolt which is newly developed as a new type of support system. For this study, field pull-out test shows the characteristics of rock bolt that is most widely used and of spiral bolt that is newly developed. And the stability of tunnels are also examined by MIDAS/GTS, numerical analysis program. The pull-out test in tunnels calls for 4m lengths of rock bolt and spiral bolt, SD350 and SD500W of materials each and 45mm of borehole in diameter. By using displacement transducer, pressure transducer, hydraulic cylinder, hydraulic hand pump and data logger, they are tested three times each on 4 hours, 8 hours, 12 hours, 16 hours after charging the resin to study the characteristics of them as the charging time passes. The results are as follows: The test shows that the cross-sectional area of rock bolt is 1.37 times and the percentage of elongation of it is 1.22 times than those of spiral bolt on the mechanical properties. And the yield strength and the tensile strength of spiral bolt are 1.25 times and 1.06 times each than those of rock bolt. According to the results of this pull-out test in process of time, the longer the time is, the bigger maximum pull-out load of spiral bolt and rock bolt are. But in rock bolt, there is 7∼9 tons of difference of maximum pull-out load in the re-pull-out test in process of time, on the other hand, there makes almost no difference in spiral bolt. As for this re-pull-out test result, being tested for three times to study the changes of maximum pull-out load, spiral bolt is almost fixed irrespective of the number of times being tested, because there is no failure between spiral bolt and filler, even when support system reaches maximum pull-out load. On the other hand, the more the number of times of rock bolt pull-out test increases, the less pull-out load decreases, because there is the partial failure between rock bolt and filler when support system reaches maximum pull-out load. This study shows the stability of tunnel is secured by a numerical analysis. And the maximum axial forces of spiral bolt and rock bolt are 1.56kN and 2.51kN each at the emergency parking zone, 3.28kN and 4.8kN each at the adit zone. When applying a spiral bolt, the axial force of bolt declined by 21.07%(adit zone)∼37.85%(emergency parking zone) and it shows that supporting effect of spiral bolt is more advanced than rock bolt.