KR20050003726A - The Construction Method of Dividing the Concrete lining into the top and bottom - Google Patents

Abstract

PURPOSE: A construction method of concrete lining by dividing into top and bottom is provided to secure the stability and economical efficiency of concrete lining and to decrease the section of a tunnel by reducing the thickness of concrete lining. CONSTITUTION: The construction method of concrete lining by dividing into top and bottom comprises the steps of pre-constructing lower concrete lining(2) on the basis of a lateral wall inflection point(4) when placing concrete lining and to secure a support point of upper concrete lining(1) as a fixed support for reducing the stress occurred on the upper concrete lining, and after curing the surface of the lower concrete lining, filling up a space between a waterproof film and the lining(2) with grouting materials under pressure to secure the enough subgrade reaction factor for a plan for restraining the transformation toward an excavation plane by placing upper concrete lining.

Description

The Construction Method of Dividing the Concrete lining into the top and bottom}

The present invention relates to a tunnel concrete lining method applied to civil engineering fields, such as roads and subways, the concrete lining of the tunnel according to the purpose of use, the mechanical function as a structure, the pressure-resistance function in the non-drained tunnel and the durability as a permanent structure and maintain the appearance And so on.

In the conventional design and construction of concrete lining to be constructed for the above purpose has shown the following problems.

First, the concrete lining is not arched but elliptical. Therefore, it is not a structure subjected to axial force but a structure subjected to bending.

In the tunnel standard specification, the die screening time is based on the concrete lining strength of 30 kgf / ㎠ and on the site is 50 kgf / ㎠ considering stability. This is a typical concrete lining design standard strength of 270 kgf / ㎠ only 10-20%. The standard of this specification is for the arch structure of the concrete structure, and the elliptical structure cannot be applied because the stress generated during the form desertion exceeds the strength during form desertion.

In addition, in the concrete lining, the inflection point 4 is located on the spring line, so that not only the axial force but also the moment is generated against the self-weight. Exceed.

Second, as the concrete lining is placed on the shear surface, the quality is easily degraded due to material separation or compaction.

In the case of road tunnels, the cross section is roughly 12m in air width and 7m in height. If the lining length is 22m, the one-time extension is 9m, and the concrete lining thickness is 0.3m, the amount of one-time concrete is 60㎥. In addition, the concrete is not easy to compact and aggregate separation occurs because the work is made in a completely closed state when placing concrete. Therefore, the concrete quality is poor.

Third, the concrete lining of the road tunnel is a structurally unstable structure when there is not enough supporting reaction of the excavation surface.

This is a very important problem, in which the concrete lining will crack if the concrete lining does not have sufficient bearing reaction. On the other hand, when designing, it is interpreted as structurally stable by applying sufficient ground reaction coefficient. Actually, the composite support layer of concrete lining (1, 2) composed of ground, shotcrete (6), nonwoven fabric and waterproof membrane (7) There is no review at all. Soil reaction coefficient is closely related to soil shape, but Wolfer's formula, which is currently used in Korea, is not able to confirm the evidence and cannot be verified.

Therefore, there is a problem in the existing design method that relies on uncertain ground reaction force, so it is necessary to secure the ground reaction force for the safety-side design.

Fourth, it did not consider the drying shrinkage of the concrete lining, so that the consideration of deformation occurrence was omitted.

In the case of the existing tunnel lining concrete cracks, 86% of the total generation is concentrated in the top end, and the longitudinal direction (length direction) is the most frequent (83%). Occurrence is found after 3-4 months and reoccurs after repair. The causes of cracks have been suggested in various ways, but the main cause of the lack of concrete strength due to early desertion of formwork is considered.

If the lack of concrete strength is the cause of the cracks, it would be reasonable to occur within a month after curing of the concrete lining is completed. However, if it occurs three to four months after the concrete lining, it will be of significant relevance to dry shrinkage.

Dry shrinkage is about 20 to 30 days after the start of drying, but the amount of shrinkage is almost the same regardless of the age of the start of drying. The shorter the drying age is, the larger the deformation is, and it is a matter of course that the dry shrinkage of concrete is significantly different depending on the drying conditions.However, in the free shrinkage state, the strain is about 6-8 × 10-4 (10M in length). About 6 to 8 mm).

Since the internal tunnel width of road tunnel in Korea is about 12m, it is assumed that 6mm dry shrinkage has occurred, so the ground reaction force will not work at all until the 6m crack in the concrete lining ceiling occurs, and the top end crack of the lining can be clearly explained. .

In conclusion, the existing concrete lining design and construction methods have many problems. The point of view of the crack problem is a problem that must be solved because the cracks are related to the suppression of cracks, but are actually related to structural stability in design and construction. to be.

An object of the present invention is to economically secure the structural stability of the concrete lining and to remove the causes of cracking to be structurally advantageous by allowing the concrete lining to behave as an arched structure from the existing elliptical structure behavior. In addition, it is to improve the quality by facilitating compaction of the lower concrete lining.

For this purpose, by installing the lower concrete lining (2) after installation, the rear grouting and the steel wedge (9) are suppressed to exhibit sufficient ground force and deformation in the lower concrete lining, thereby reducing the amount of stress generated in the upper concrete lining (1), and ensuring sufficient compaction. It aims to improve quality by making it possible.

Efforts are needed to eliminate the space between the lower concrete lining and the ground, which may be caused by dry shrinkage, by filling the shrinkage grouting on the back after pre-installation.

1 is a conceptual diagram of pouring the upper concrete lining (1) by the method of the present invention

2 is a conceptual diagram of the grouting injection pipe 10 pre-installed for filling and grouting the steel wedges 9 after the lower concrete lining 2 is poured.

* Explanation of symbols for the main parts of the drawings

1: upper concrete lining 2: lower concrete lining

3: shear reinforcing bar 4: side wall inflection point

5: steel formwork 6: shotcrete

7: nonwoven fabric and waterproof film 8: vinyl film

9: steel wedge 10: grouting injection tube

The present invention consists of a method that allows the lower concrete lining (2) to serve as a fixed point of the upper concrete lining (1) with respect to the spring line in order to behave as a tunnel lining arched structure.

In order to act as a fixed point, the lower concrete lining must be in close contact with the ground and the required ground force must be secured.

Figure 1 shows the top and bottom of the concrete lining pour steel formwork (5) and pour form. Instead of the existing shearing formwork, the lower concrete lining is first casted based on the spring line, and the upper concrete lining is poured after completion of curing.

Figure 2 shows the steel wedge 9 and the grouting injection tube 10 for non-contraction mortar grouting to ensure sufficient ground force against the bottom concrete lining. Nonwoven fabric and waterproof membrane construction through Landel may cause back space when lining is placed, in which case the ground force coefficient is small and sufficient ground force is not exerted. It also plays a role in filling gaps in the back surface due to dry shrinkage during curing of the lower concrete lining.

Therefore, by grouting the lower concrete lining to remove the rear cavity and to secure the required ground force. For smooth back grouting, it is separated from the waterproof membrane by the pre-pour vinyl membrane (8).

Since the lower concrete lining is easy to inject and compact, it is advantageous to take concrete mix to reduce dry shrinkage.

As the concrete lining is separated from the upper and lower parts, the lower concrete lining can be sufficiently compacted, so quality improvement can be expected.

In addition, after curing the lower concrete lining, it is possible to secure sufficient ground reaction force by back grouting and wedge clamping and to prevent deformation, thereby securing the point of the upper concrete lining as a fixed point, thereby drastically reducing the stress generated in the upper half concrete lining The thickness can be reduced.

Therefore, it is possible to ensure the stability and economy of the concrete lining through the present invention. In addition, if the concrete lining thickness is reduced, the tunnel section can be reduced.

Claims (3)

When laying concrete lining, the lower concrete lining (2) is pre-installed based on the sidewall inflection point (4) to secure the support point of the upper concrete lining (1) as a fixed support to reduce the stress generated in the upper concrete lining After curing of the lower concrete lining is completed, the space generated between the waterproofing membrane 7 and the lining 2 is pressurized and filled with grouting to secure sufficient ground reaction coefficient required by the design. Method to suppress deformation The method of attaching the vinyl film 8 to the waterproofing membrane 7 when placing the lower concrete lining according to claim 2, filling the wedge 9 with the non-shrink mortar or mortar added with an expanding agent after curing is completed.