The invention discloses a construction method for leading out a turnout extra-large-section tunnel in a railway
cave. The construction method comprises the following steps that 1, an extra-large-section
cave auxiliary excavation section is constructed; 2, expanding excavation is conducted on the auxiliary excavation section; 3, grouting is conducted on a middle
pipe shed; and 4, the extra-large-section
cave is excavated. According to the construction method for leading out the turnout extra-large-section tunnel in the railway cave, construction is flexible and changeable, the applicability is high, and the construction speed is high; by combining the characteristic that the
lithology of surrounding rock of the extra-large-section cave is good, a simple middle partition wall method and two large-
diameter steel
pipe temporary vertical supports are adopted on the upper half section of the extra-large-section cave, and excavation is conducted on the
lower half section of the extra-large-section cave through a
step method; a double-side-wall equal-large-section shallow-buried and soft rock construction method is replaced, so that a steel arch frame can be smoothly connected from the arch top to the two ends, the stress structure is stable, and enough operation space can be provided for large construction operation equipment; and the defects that according to the double-side-wall equal-large-section shallow-buried and soft
rock tunnel excavation construction method, large equipment is difficult to unfold, the construction speed is low, and the
safety risk is high are overcome, and the application range of the tunnel
step method excavation construction method is expanded.