Comprehensive Technology Study In Fast Construction Of Parallel Guide-Pit At Exit Section Of Qinling East Extra-long Tunnel

Located in the Shanxi Province, The East Qinling Tunnel with a 12,268m length is the first important project controlling the building time of the Xi'an-Nanjing railway. The leftward parallel adit is 30m from the main cavern, 6,129m long , with one section 6.15m×4.5m(net height×net width), 3,642m long the other section 4.5m×4.0m(net height×net width), 2,487m long. The trim size of parallel adit excavated is 25~32m2. The project has complicated geology such as rich underground water, short construction time and crossing 6 faultage. The paper systemically studies all kinds of key technologies of East Qinling tunnel exit guide pit as follows:1.Studying the reasonable cycle speed, fast excavation and drill blasting technology parameter and the double wedge-type, which are adapted for the 25~32m2 section and to enhance the effect of explosion.2.Adopting the method of mixed ventilation with pressure and drawing in different places of extra-long guide-pit, which effectively solves the problems in ventilation and smoke-out on guide-pit work face and on multi-faces of the main cavern;Summarizing out a set of technology to prevent leaking and decrease barrier such as wind pipe selection, installation, adoption and management in pipe lines aiming at decreasing the average wind-leaking rate per 100m pipe lines less than 1%;3.Putting forward a kind of mechanized construction model with reasonable match, which adapts to the fast construction in small section mainly for national machines produced in the homeland;4.Summarizing out a set of experiences in construction orgnization and management on the base of human, including construction speed, quality and safety control;The result of the paper not only saves the cost but also increases the work faces of the main cavern as well as excavates a long tunnel in shorter time, which greatly promote a fast construction in parallel adit and guarantee the speed of cavern work and a successful completion. A max record of monthly depth 292.5 was once created from commencement to crossing (6,129m long) of parallel adit, which is the first time to construct a long-large tunnel without any accidents and also supplies the precious experiences for similar parallel adit.