What are the key points for tunnel lining quality control?

Tunnel lining plays an important role in the support of tunnel engineering. It is to prevent deformation or collapse of surrounding rock. The permanent support structure built along the periphery of the tunnel body requires quality control of four major links in actual construction. Look down.

1. Construction of tunnel lining

(1) The secondary lining must be carried out when the deformation of the surrounding rock and the initial support is basically stable, and the displacement convergence speed is obviously slowing down, and the various displacements must reach 80% to 90% of the estimated total displacement.

(2) Before the construction of the lining, the waist line must be measured to control the deviation of the invert and foundation pouring, and the lining section base surface and vault elevation should be detected. The thickness error of the tunnel lining meets the design requirements to ensure the clearance height in the tunnel.

(3) The thickness and compactness of the lining must be checked after the construction of the lining, and the electrical signal of the corresponding frequency is generated by the transmitter according to the command of the control unit for detection.

(4) The construction site of the lining must be continuously measured, and continuously collected along the measuring line during the inspection, paying attention to stable movement and uniform speed.

The tunnel concrete maintenance formwork

2. Construction of tunnel lining structure

(1) Strictly control the mixing ratio of concrete, check the quality of raw materials before mixing, and do not change at will after verification by tests. Add accelerator according to the construction environment temperature.

(2) In order to ensure the quality of concrete, it must be sprayed and sprayed continuously; check whether the mechanical equipment is operating normally before construction.

(3) The steel mesh for lining must be spot welded into blocks at the intersection, and the anchor rods must be laid after completion to ensure that the mesh is close to the initial spray surface. After the construction is completed, the thickness of the concrete protective layer and the connection performance of the steel must be tested.

3. Tunnel lining template construction

(1) Ensure that the formwork engineering support is firm and stable, and detect whether there is excessive deformation and subsidence; the rigidity of the formwork support at the large variable section must be checked, and the setting must be correct before installation.

(2) Ensure that the surface of the formwork is cleaned, and the mold release agent is applied to ensure the quality of the concrete molding; during the construction, pay attention to the joints are flat and tight, and there is no hidden danger of dislocation.

(3) The error of each part of the control structure meets the requirements, the elevation of the vault does not exceed 10mm, the error of the center line does not exceed 10mm, and the error of clearance does not exceed 10mm.

Tunnel waterproof board laying formwork

4. Treatment of lining cracks

(1) The fine cracks can be painted with epoxy resin slurry after cleaning, and then the surface of the concrete can be treated with scraping material and toning material to achieve a beautiful effect.

(2) For penetrating cracks, V-shaped grooves must be cut along the direction of the cracks, and holes shall be drilled across the cracks in the grooves. After removing the debris, the epoxy cement mortar shall be used to anchor, and the same strength grade cement shall be used to smooth it.

(3) Dense cracks must be additionally waterproofed and reinforced. Cement mortar shall be injected into the cracks to ensure full grouting; anchor pads shall be installed 1 day after grouting, and then filled with epoxy mortar.

In summary, there are four points about the quality control of tunnel lining during the construction process. Only by doing these can the quality and safety of the tunnel be guaranteed.

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