JPH02167999A - Cast-in-place lining method of shielded tunnel - Google Patents

Abstract

PURPOSE:To shorten the cycle of lining operation by dividing the pressing of placed concrete into two stages, pressing placed concrete by primary pressing, filling a lining space with concrete and further pressing placed concrete by secondary pressing. CONSTITUTION:A main bar 10 and a distribution bar 11 are arranged into a space formed by retracting the press ring 4 and a shielding jack 9 of a shielding excavator 21, inner forms 5 are assembled, and the press ring 4 and a spreader 8 are set again. Fresh concrete 6 is primarily pressed into a lining space 2 including a tail void 2a shaped by propulsion by the force of 0.1-0.5kgf/ cm<2> by the press ring 4 of a jack 4a for concrete lining from a placing hole 7. The jack 4a is operated and the press ring 4 is pressed by the force of 5kg/cm<2>, and concrete 6 is dehydrated. Accordingly, the initial strength of concrete can be increased.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for lining a shield tunnel, and more specifically, the present invention relates to a method for lining a shield tunnel, and more specifically, it is possible to quickly fill the lining space, including the tailboard, created by the excavation of a shield excavator. Moreover, the present invention relates to an on-site pouring method that allows the concrete to be densely filled and the strength of the concrete to be developed quickly.

(Prior Art) Generally, it is known that ready-made segments are used in the concrete lining method after excavation of a shield tunnel, but recently the construction of the segments has been omitted and the construction is directly covered with cast-in-place concrete. A new method of construction (hereinafter referred to as the ECL construction method) has been adopted.

To explain this ECL method, as shown in FIG. 7, after the shield excavator 21 is propelled, a concrete lining jack 4a is placed inside the tail plate 1 and operates in the axial direction of the tail plate l. The rod 4b is shortened, and a reinforcing bar (
(not shown), and a cylindrical inner formwork 5 is placed inside the reinforcing bars.Next, a space is defined between the tail plate 1, the existing lining portion 3, and the press ring 4. (hereinafter referred to as the lining space 2 including the tail board 2a) (hereinafter referred to as fresh concrete 6), by operating the concrete lining jack 4a while propelling the shield excavator 21. The fresh concrete 6 is pressed through the press ring 4 to fill the lining space 2 including the tail board 2a to form a new lining wall portion.

In this case, in order to fill concrete, it is necessary to have good workability (the degree of softness of concrete that is related to the difficulty of pouring work), and to ensure this workability, a slump test (JIS
The slump value in A 1101) is increased.

(Problems to be Solved by the Invention) By the way, the press ring 4 is pressed together with the propulsion of the conventional shield excavator 21 described above to fill the lining space 2 with fresh concrete 6 and to develop initial strength. With this method, it takes a long time for the poured concrete to harden, and the existing lining part has to be pressed and held for the required time using the press ring 4. Therefore, the concrete lining work cycle is long. In addition, the pressed fresh concrete 6 has a pressing force of, for example, 1 k.
If it exceeds gf/cut, rapid dehydration will occur, and the fluidity of the fresh concrete 6 will decrease (
As a result, the filling of the lining space 2, especially the tail board 2a, is not performed densely, and the adhesion of the poured concrete to the ground is reduced. Unfortunately, there was a risk that the earth and sand at the top of the tailboard would cave in due to the effect of surrounding earth pressure, leading to ground subsidence.

The object of the present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a shield tunnel that can precisely fill the lining space including the tail board with concrete and shorten the cycle of concrete lining work. The purpose of this invention is to provide an on-site lining method.

(Means for solving the problems) Solving the above problems of the on-site lining method according to the present invention,
The means to achieve the objective is to pressurize the poured concrete through a press ring fixed to the tip of a pressing means equipped on the shield excavator, and as the shield excavator of the shield tunnel is propelled. In an on-site lining method in which the lining space including the resulting tail board is filled with concrete, the pressure of the poured concrete is divided into two stages, the first stage of which impairs the fluidity of the poured concrete. The poured concrete is pressurized and filled into the lining space through primary pressurization, which is an unprecedented pressurization process, and in a second stage, secondary pressurization is applied to obtain a predetermined concrete strength. This consists in that the poured concrete is pressurized.

As described above, according to the method for filling the tail board of a shield tunnel according to the present invention, fresh concrete is pressurized and filled into the lining space including the tail board using a low primary pressure that does not reduce workability. The fresh concrete is densely filled into the lining space including the tailboard without impairing its fluidity.

Next, the fresh concrete is pressed and cured using secondary pressurization, which is pressurization that can quickly obtain the desired concrete strength, and the adhesion of the fresh concrete increases due to dehydration caused by the secondary pressurization. The initial strength is developed. This allows the press ring to be removed from the mold faster than before. Here, the reason why fresh concrete can be made to exhibit desired concrete strength by the secondary pressurization is considered to be as follows.

According to concrete pressurization experiments, as shown in FIG. 5, at the initial age of poured concrete, the concrete strength increases in proportion to the magnitude of the applied pressurizing force. In other words, the initial strength of fresh concrete that has just been placed is not due to the hydration reaction of cement, but is thought to be due to an increase in adhesive strength due to the dehydration effect caused by the pressurizing force applied to the fresh concrete. This is supported by the fact that the amount of water removed increases in proportion to the pressure applied to the concrete, as shown in FIG. 6, which supports the fact that the strength of concrete increases due to the action of water removal. Note that W/C in the figure represents the water-cement ratio.

(Example) An embodiment of the present invention will be described below with reference to the accompanying drawings.

1(a), 1(a), and 1(c) are partially enlarged sectional views showing the construction procedure of the on-site lining method for a shield tunnel of the present invention. 1 is a tail plate of a shield excavator 21; 2 is the tail board produced by propelling the shield excavator. 3 is the previously cast and hardened concrete. 4 is the press ring that is pressurized by the rod 4b of the concrete lining jack 4a. .5 is the inner formwork, 5
a is the inner formwork installed last time, 6 is the fresh concrete, 7 is the pouring hole, 8 is the spreader, and 9 is the shield jack.

As shown in Fig. 2, the construction procedure is to pull back the press ring 4 and shield jack 9 of the shield excavator 21, place the main reinforcement 10 and distribution reinforcement 11 in the space created by this, and then remove the inner formwork. 5 and set the press ring 4 and spreader 8 again. This press ring 4 is slid between the tail plate 1 and the spreader 8 in a watertight manner.

Then, fresh concrete 6 is poured into the pouring hole 7 provided in the press ring 4 using a concrete pump (not shown).

Next, as shown in FIG. 1(a), the shield excavator 21
Fresh concrete 6 is filled into the lining space 2 including the tail board 2a created by the excavation. At this time,
The concrete lining jack 4a is activated and the pressure applied to the fresh concrete 6 by the press ring 4 is 0.1.
~0.5 kgf/cnf.

This pressurization force is called primary pressurization, and this pressurization need only be slightly higher than the soil water pressure of the ground, and it may be a pressure that does not impair the fluidity of the fresh concrete 6 and can push it out. By this secondary pressurization, the above-mentioned slump value will not become less than 18 cm, and the fluidity of the fresh concrete 6 will not be impaired. The concrete 6 will be densely filled.

Thereafter, as shown in FIG. 1(B), the concrete lining jack 4a is operated and the press ring 4 is further pressurized to dehydrate the fresh concrete 6 and increase its initial strength. The reason for this increase in the initial strength of concrete is as described in the section of the effect.

At this time, the pressing force was 5 kg/-, and this was called secondary pressing, and the concrete curing time was 1 hour. As a result, the initial strength of the concrete reached 1 in 2 hours when the press ring 4 was removed from the mold, and the desired strength became greater than gf/ca1.

In this example, the water-cement ratio (W/C) is 50%, but in order to make watertight concrete, it is preferable to make the water-cement ratio 55% or less. This shows how to demold 4.

FIG. 3 shows a pressure pattern for filling the tailboard of poured concrete in two stages.

Furthermore, when comparing the tail board filling method using two-stage pressurization according to the present invention and the case using only primary pressurization, it was found that the fourth
As shown in the figure, concrete strength of 1 kgf/cnt is obtained in 2 hours when using only negative pressure.
With the two-stage pressurization method, a concrete strength of 1 kgf/crd could be obtained in 1 hour and 25 minutes, resulting in a time reduction of 35 minutes.

Comparing the cycle time and construction time per meter between the conventional segment shielding method and the tail board filling method of the present invention, it is approximately 207 m1n/a for the conventional method, and approximately 207 m1n/a for the method of the present invention. In the unreinforced case, it was 167 m1n/+, and in the reinforced case, it was 193 m1n/m, making it clear that the time was shortened.

(Effects of the Invention) As described above in detail, the on-site lining method for a shield tunnel according to the present invention has the following effects. *Ch. ■ Fresh concrete is filled in the lining space including the tail board that is generated as the shield excavator is propelled by the first stage of primary pressure using the press ring, so the fresh concrete is filled with the lining space including the tail board. The work space is densely filled. Therefore, the adhesion of concrete to the ground is improved, and ground subsidence, which was a problem with conventional methods, is reduced.

■ Furthermore, by performing the second stage of secondary pressing after the above-mentioned secondary pressing, it is possible to obtain the desired initial strength of concrete in a shorter time than before, which greatly contributes to shortening the construction period. Ta.

■ The fresh concrete filled into the tailboard becomes dense concrete, eliminating the need for conventional backfilling.

In this way, we have been able to provide a valuable on-site lining method.

[Brief explanation of the drawing]

Figures 1 (a), (c), and (c) are partially enlarged sectional views showing the construction order of the tail board filling method of the present invention, and Figure 2 is a
FIG. 3 is a partially enlarged sectional view during concrete pouring; FIG. 3 is a diagram showing the pressurization pattern of concrete; FIG. 4 is a comparison diagram of the demolding time of the press ring according to the present invention and the conventional method; FIG. 6 is a diagram showing the relationship between material age and compressive strength, FIG. 6 is a diagram showing the relationship between pressing force and dewatering rate, and FIG. 7 is a longitudinal sectional view of a conventional shield excavator. Ku1... tail plate, split tail board, 3...
Previously constructed wall, 4... Press ring, 5... Circular formwork, 6... Fresh concrete, 7... Casting hole, 8... Spreader, 9... Shield jack, 10 ...Main reinforcement, 11... Distribution reinforcement. Figure 1 (A) Figure 1 (D) Figure 1 Figure 2 Figure 3 Time (min)

Claims (1)

[Claims] By pressurizing poured concrete through a press ring fixed to the tip of a pressing means provided on the shield excavator, the tail board that is generated as the shield excavator advances in the shield tunnel. In the on-site lining method in which concrete is filled into the lining space including the concrete, the pressure of the poured concrete is divided into two stages, the first
In the step, the poured concrete is pressurized by primary pressurization that does not impair the fluidity of the poured concrete and is filled into the lining space, and in the second step, the concrete strength is increased to a predetermined level. A method for on-site lining of a shield tunnel, characterized in that the poured concrete is pressurized by secondary pressurization, which is the pressurization obtained.