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Geomechanics and Engineering
  Volume 21, Number 2, April25 2020, pages 207-213

Shear strength behaviors of grouts under the blasting induced vibrations
Myung Sagong, Il Yoon Choi, Jun S. Lee and Chung-sik Cho

    Umbrella Arch Method (UAM) often employed in the tunnel construction under poor rock mass conditions in Korea. Insertion of steel pipes at the periphery of the tunnel and infiltration of grouts along the pipes into the rock masses increases tunnel stability. There are two major effects of grouts expected at the tunnel face: 1) increase of face stability by enhancing the frictional resistance of discontinuities and 2) decrease of permeability along the rock masses. Increase of resistance and decrease of permeability requires a certain curing time for the grout. In Korea, we require 24 hours for curing of grout, which means no progress of excavation for 24 hours after infiltration of grouts. This step delays the tunnel construction sequences. To eliminate such inefficiency, we propose MTG (Method for Tunnel construction using Grouting technology), which uses extended length of steel pipes (14 m) compared to conventional pipe roof method (12 m). The merit of MTG is the reduction of curing time. Because of the approximately 2 m extension of the length of steel pipe, blasting can be done after infiltration of grouting. For this paper, we conducted experiments on the shear strength behaviors of grout infilled rock joint with elapsing of curing time and blasting induced vibration. The results show that blasting induced vibration under MTG does not influence the mechanical features of grout material, which indicates no influence on the mechanical behaviors of grout, contributing to the stability of tunnels during excavation. This result indicates that MTG is a cost effective and fast construction method for tunneling in Korea.
Key Words
    umbrella arch method (UAM); method for tunnel construction using grouting technology (MTG); grouting; tunnel reinforcement
Myung Sagong, Il Yoon Choi and Jun S. Lee: Department of Advanced Track & Civil Engineering, KRRI, Uiwang, 16105, Korea

Chung-sik Cho: Geotech Engineering Co. Ltd. Anyang, Korea

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