Complementary circulating digging method for floated pebble stratum large section tunnel

Abstract

The invention discloses a complementary circulating digging method for a floated pebble stratum large section tunnel. The digging method includes: using dug dregs at different parts to complement eachother; alternatively and circularly backfilling and stabilizing arc feet; canceling advance supports and system anchoring rods in a support system so as to reduce surrounding rock disturbance; adopting small-bore dual-layer reinforcing meshes; reinforcing a supporting and restraint function of foot locking anchoring rods for steel frames by increasing the group number of the self-propelled foot locking anchoring rods and reduce the length of the self-propelled foot locking anchoring rods; and using a monitoring system including deformation monitoring and foot locking anchoring rod axial forcemonitoring to master a safe state of surrounding rocks and a structure in real time from deformation and stress dual views. The digging method can fully consider the features of a floated pebble stratum, can reinforce a horizontal restraint effect of the support system on the surrounding rocks, can effectively reduce surrounding rock disturbance, can improve the construction efficiency, can savethe project cost, can ensure the safety of the structure and the stability of the surrounding rock in an early tunnel construction process.

Description

technical field [0001] The invention belongs to the technical field of construction and excavation of large-section highway tunnels in boulder formations, and in particular relates to a complementary circulation excavation method suitable for large-section tunnels in boulder formations. Background technique [0002] At present, a large number of large-section tunnels have been built in rocky and uniform soil strata in my country, but there are very few large-section tunnels built under dense boulder strata, and there is a lack of empirical summary and theoretical research on its excavation methods. . The boulder and sandy pebble formations are typical heterogeneous formations, which have the characteristics of poor cementation, easy to slide and fall off, and it is difficult to install bolts, and the formation structure is dense and easy to overbreak. The Chengdu Metro was constructed in the sandy pebble stratum, and concluded that less disturbance in the sandy pebble stratu...

AI Technical Summary

Problems solved by technology

The floating pebble tunnel that can be excavated has a dense structure, but it cannot be blasted. If the CD method, CRD method and other partial excavation methods are adopted, it will bring great difficulties to machinery and labor, and the construction speed will be very slow.

It is more reasonable to adopt the step method for excavation, and it can also ensure the progress of the tunnel construction. However, due to the particularity of the boulders, the conventional drilling anchors are prone to collapse and cannot form holes, while the self-propelled anchors are easy to push against the boulders and cannot be drilled. Drilling to the design depth, the position of the arch foot of the tunnel lacks effective constraints, the lateral deformation is relatively large, and there is a possibility of slippage if there is any carelessness

The current mature rock tunnel and soil tunnel excavation methods are difficult to meet the technical and safety requirements of boulder stratum excavation

In order to solve the problem of tunnel construction in boulder stratum, it is necessary to solve the problems of insufficient restraint of arch foot, easy over-excavation of tunnel, easy sliding of side wall, easy falling of vault and the monitoring of these risks

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