다목적 지보재인 친환경 스파이럴 볼트의 지보특성에 관한 연구

Abstract

This study is to defined the characteristics of Eco-Spiral Bolt (ESB) as multipurpose support member which was developed for improvement of ground strength among various geotechnical problems. For this purpose, we analysed the difference of ground behavior along the twisted angle of Eco-Spiral Bolt, a ratio of borehole diameter and Eco-Spiral Bolt width, and ground structure of single layer and multi-layer using FLAC 3D based on Finite Difference Method (FDM). By the results of ground behavior along the twisted angles of Eco-Spiral Bolt, 0°, 15°, 30°, 45°, 60°, the pull-out load at 8 mm with the maximum displacement was 0°=63.9 kN, 15°=21.9 kN, 30°=62.9 kN, 45°=76.4 kN, 60°=135.3 kN, respectively. The maximum shear stress between Eco-Spiral Bolt and grout of the X-Y section at a depth of 70 cm was 0°=564.36 kPa, 15°=135.26 kPa, 30°=511.49 kPa, 45°=434.62 kPa, 60°= 411.69 kPa, and 0°=13.42 kPa, 15°=150.35 kPa, 30°=511.63 kPa, 45°=441.79 kPa, 60°=425.77 kPa in the X-Z section. In conclusion, it is considered that the optimal twisted angles of Eco-Spiral Bolt is most suitable between 30° and 45°. By the results of ground behavior along a ratio of borehole diameter and Eco-Spiral Bolt width (), 1.5, 2.0, 3.0, the pull-out load at the 8 mm with the maximum displacement was 1.5=187.57 kN, 2.0=425.85 kN, 3.0=741.02 kN, respectively. The maximum shear stress between Eco-Spiral Bolt and grout of the X-Y section at a depth of 70 cm was 1.5=1052.38 kPa, 2.0=2652.35 kPa, 3.0=4589.42 kPa, and 1.5=953.67 kPa, 2.0=3016.76 kPa, 3.0=6667.32 kPa in the X-Z section. In conclusion, it is considered that the maximum shear stress on the boundary between Eco-Spiral Bolt and grout increased with increasing a ratio of borehole diameter and Eco-Spiral Bolt width, and the optimal ratio of borehole diameter and Eco-Spiral Bolt width was 1.5. By the results of ground behavior along ground structure of single layer and multi-layer, the pull-out load at the 8 mm with the maximum displacement was 79.94 kN. The maximum shear stress between Eco-Spiral Bolt and grout of the X-Y and X-Z sections at a depth of 70 cm was 441.40 kPa and 452.02 kPa, respectively. In conclusion, it is considered that the support effect of Eco-Spiral Bolt was greater in multi-layer than single layer.