Development and Mechanical Performance Study of a New Type of Flexible Protective Geogrid for Tunnel Rock Burst.

Deep buried tunnels face high in-situ stress during the construction process, which can easily trigger rock burst. Flexible protective system is an important way to achieve disaster control. Regarding the problem of low toughness and inability to resist instantaneous impacts in the existing flexible protective materials, this study develops a high-strength and high-toughness flexible geogrid based on three deformation modes that may occur when it intercepts explosive blocks. This process considers the selection of polymer fiber filaments, optimization of weaving methods, and improvement of fabric structure. The stress and deformation characteristics of flexible geogrids are analyzed through single-rib tensile, nodal peel, and static jacking tests. The tests showed that mechanical performance of the flexible geogrid can meet requirements for strong and below level rock burst. To analyze the effects of strip strength strip, elongation at break, and nodal strength on the characteristics of jacking deformation, numerical simulations are conducted based on the discrete element method. The results showed that the elongation at break is controlled within 13%, the strip strength is greater than 0.8 GPa, and the nodal strength is increased to 0.075 GPa or above, which can significantly improve the rock-burst protection ability of the flexible geogrid. Finally, the impact energy absorbed by the flexible geogrid reached 74.23 kJ through the falling ball impact experiment, and the engineering application of the flexible geogrid is achieved in the rock-burst section of the Duoji Tunnel on the CZ Railway. [ABSTRACT FROM AUTHOR]