Abstract
Tunnelling or undertaking below‐ground construction in squeezing ground can always present many engineering surprises, in which this complicated geology bring a series of tunnelling difficulties. Obviously, if the major affecting factors and mechanism of the structure damage in these complicated geological conditions are determined accurately, fewer problems will be faced during the tunnel excavation. For this study, reference is made to four tunnel cases located in the Qingling‐Daba mountainous squeezing area that are dominated by a strong tectonic uplift and diversified geological structures. This paper establishes a strong support system suitable for a squeezing tunnel for the purpose of addressing problems exhibited in the extreme deformation of rock mass, structure crack, or even failure during excavation phase. This support system contains a number of temporary support measures used for ensuring the stability of tunnel face during tunnelling. The final support system was constructed, including some key techniques such as the employment of the foot reinforcement bolt (FRB), an overall strong support measure, and more reserved deformation. Results in this case study showed significant effectiveness of the support systems along with a safe and efficient construction process. The tunnel support system proposed in this paper can be helpful to support design and provide sufficient support and arrangement before tunnel construction in squeezing ground.
Highlights
Study AreaMain body of the Qingling-Daba mountainous area is located in southern Shaanxi province, in which its administrative division includes Hanzhong, Ankang, and Shangluo
Tunnelling or undertaking below-ground construction in squeezing ground can always present many engineering surprises, in which this complicated geology bring a series of tunnelling difficulties
Reference is made to four tunnel cases located in the Qingling-Daba mountainous squeezing area that are dominated by a strong tectonic uplift and diversified geological structures. is paper establishes a strong support system suitable for a squeezing tunnel for the purpose of addressing problems exhibited in the extreme deformation of rock mass, structure crack, or even failure during excavation phase. is support system contains a number of temporary support measures used for ensuring the stability of tunnel face during tunnelling. e final support system was constructed, including some key techniques such as the employment of the foot reinforcement bolt (FRB), an overall strong support measure, and more reserved deformation
Summary
Main body of the Qingling-Daba mountainous area is located in southern Shaanxi province, in which its administrative division includes Hanzhong, Ankang, and Shangluo. Ere are significant signs of neotectonics in southern Shaanxi, and differential movement of fault blocks is obvious after inheriting the Himalayan orogeny at the end of the tertiary period It has a profound impact on the formation and development of the landforms which can be reflected by the formation of mountainous regions with high mountain, deep valley caused by continuous rising, and wide and flat basins induced by continuing decline since Quaternary. Karst ssure water is the main form of groundwater, which is in great quantities, but not a large distribution area, accounting for more than half of the total reserves. It is mainly distributed in Ningqiang county, Zhenba county, and the eastern region of Xunyangba. Undeveloped rock ssures coupled with steep terrain cause most part of the precipitation lost in the form of the surface runo , which is unfavourable for groundwater recharge
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