A construction method for primary support intrusion limit and arch replacement of large-section loess tunnel

Abstract

The invention discloses a method for beyond-limit arch replacing construction during preliminary bracing of a large-section loess tunnel. The method includes the steps of firstly, conducting radial grouting reinforcement on an arch wall, wherein radial grouting reinforcement is conducted on an arch replacing required section where arch replacing is required in the constructed loess tunnel from back to front; and secondly, conducting arch replacing construction, wherein a reinforced preliminary bracing structure in the arch replacing required section is detached, and preliminary bracing construction is conducted on the arch replacing required section synchronously in the detaching process. The method is simple in step, reasonable in design, simple in construction and good in use effect; theradial grouting reinforcement is conducted on the arch wall to reinforce the arch wall of a tunnel hole first, so the structural stability of the tunnel in the arch replacing process is ensured; segmented reinforcing is conducted on the preliminary bracing structure of the tunnel through a plurality of sleeve arch units for a reinforced sleeve arch in the arch replacing required section, so detaching is convenient; and moreover, the sleeve arch units are complementary and together improve the supporting force, so the adverse effects on the structural stability of the tunnel in the detaching process of each sleeve arch unit can be effectively reduced, and the safety and reliability of the arch replacing construction process are ensured.

Description

technical field [0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a large-section loess tunnel initial support invasion limit arch replacement construction method. Background technique [0002] Loess refers to sediments of yellow silt transported by wind during the Quaternary period in the geological era. Loess collapsibility coefficient (also called collapsibility coefficient) is a mechanical parameter to evaluate the collapsibility of loess. Under a certain pressure, loess collapsibility coefficient refers to the ratio of the difference between the height of the soil sample before and after soaking in water and the original height of the soil sample. The collapsibility coefficient of loess is an important index to evaluate the collapsibility of loess, which can be directly measured by experiment. According to the different collapsibility coefficient of loess, loess can be divided into collapsible loess and non-collaps...

AI Technical Summary

Problems solved by technology

While this traditional arch replacement method affects the progress of tunnel excavation, it still has potential safety hazards and certain defects: for example, the longitudinal and horizontal directions of single-point vertical or diagonal braces are not connected, the foundation is not stable, and impact crushing is often used to demolish concrete. Hammer, it is easy to cause the arch to collapse due to uneven force on the vertical or oblique fulcrum; in severe cases, it will cause "door closing" accidents

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