Pre-supporting with Horizontal Piles of Jet Grouting in Weak Loess Tunnel
Considering the characteristics of surrounding rock of one highway tunnel discussed in this paper, pre-supporting with horizontal piles of jet grouting was used in portal section in order to improve the bearing capability of highway tunnel foundation. Diameter, length, longitudinal intervals of horizontal piles of jet grouting were determined preliminary based on calculation and references of some other projects. According to the geological conditions of surrounding rock, different water cement ratios, pressures of jet grouting, velocities of lifting and other construction parameters were put to use to large-scale field test. Diameter, length, 3 d and 28 d compressive strength of all test piles were checked, on which pre-design were adjusted and design indexes, construction parameters were get. Engineering application has proved the strong adaptability and maneuverability, and bearing capability and stability of highway tunnel foundation were improved through this method, therefore, this paper can be used for reference in design and construction of highway tunnel in weak loess.