JPH01198995A - Cast-in-place lining method - Google Patents

Abstract

PURPOSE:To simplify a work, to increase a working speed, and to improve contraction property, by a method wherein a cage with holes containing reinforcing bars and coarse aggregates is situated between formed assembled in a tail and the tail, and a space between the forms and a bedrock with grout having high-early-strength is filled with grout. CONSTITUTION:A cage body 2 formed with a member, e.g., a wire net or an expand metal, having rigidity and filled with coarse aggregates 21, e.g. gravels, and in which reinforcing bars 22 are arranged is mounted on the outer peripheral surface of forms 1. The forms 1 are assembled inside a tail 3 so that a gap is provided between the outer peripheral surface of the cage body 2 and the tail 3. Gaps between the coarse aggregates 21 and a whole extending to a bedrock are enoughly filled through an injection hole 11 with grout 5, having excellent high-early-strength and fluidity, without a gap. The forms 1 are removed, and formation of a ring is completed in a state that the cage body 2 is left in concrete, and thereafter the same work is repeated as a shield machine is propulsively moved to perform a lining work.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a cast-in-place lining method using prepacked concrete.

Conventional technology> Cast-in-place lining has traditionally been one of the shield tunnel construction methods.

In shield construction, segment costs often account for as much as 30% of the construction cost.

Therefore, the cast-in-place lining method is a construction method in which concrete is poured on-site to serve as the -1 secondary lining, without performing the primary lining using segments, and as the final lining.

The outline of this method is as follows: First, a ring-shaped formwork is assembled inside the tail of the shield machine, and a bushing rod that transmits thrust is installed in this formwork.

Then, early-strength concrete is poured between the formwork and the ground and cured, and when the required strength is achieved, it is pressed down with a shield jack using a bushing rod as a reaction force receiver, and the shield machine is propelled. It is something that is repeated.

Problems to be Solved by the Present Invention> The conventional cast-in-place lining method described above has the following problems.

(ii) Cast-in-place concrete is susceptible to the effects of ground pressure and the reaction force of shield jacks while it hardens, causing problems with construction accuracy such as deformation of concrete structures.

Entrance: Concrete is poured directly between the formwork and the ground, making it difficult to fill it with enough concrete.

Therefore, after pouring, a gap (tail void) is created between the concrete and the ground, which may cause ground subsidence.

Kuha〉The work becomes difficult because it is necessary to install large machines such as concrete pumps in a small work space.

2) Because fluid concrete is poured, the concrete flows into the shield, making workability not very good.

OBJECTS OF THE INVENTION The present invention was made to solve the above problems, and an object of the present invention is to provide a cast-in-place lining construction method that is excellent in workability and construction efficiency.

<Configuration of the Present Invention> An embodiment of the present invention will be described below with reference to the drawings.

〉 Formwork and parts (Fig. 1) The formwork l is made of ordinary steel segments, etc., and has grout injection holes 11 opened therein.

The member 2 is a structure having a plurality of holes and made of a rigid member such as wire mesh or expanded metal.

This part body 2 is filled with coarse aggregate 21 such as gravel, and reinforcing bars 22 are further arranged.

In order to obtain the desired concrete strength, coarse aggregate 21 having a predetermined diameter is packed in an appropriate amount.

Then, this part body 2 is attached along the outer peripheral surface of the formwork 1.

Attachment is performed using bolts, nuts, etc., and when demolding, loosen the nuts and remove the formwork 1.

Installation of the formwork and parts (Fig. 2.3) As shown in Fig. 2.3, the formwork 1 with the parts 2 attached is assembled in a ring shape inside the tail 3 of the shielding machine.

During assembly, the reinforcing bars 22 of each part 2 are wrapped.

At this time, the width of the member 2 is set in advance so that there is a slight gap between the outer peripheral surface of the member 2 and the inner peripheral surface of the tail 3.

(c) Grout The present invention is a cast-in-place lining method using prepacked concrete.

Therefore, grout 5 that does not contain coarse aggregate is used.

This grout 5 uses a material with excellent early strength and fluidity, for example, early strength cement with a water-cement ratio of 40% and a cement-sand ratio of 1 = 1, a high performance water reducing agent, a superplasticizer, etc. A conceivable solution is one in which the flow value (P float) is set at around 20 seconds.

2〉Filling and promoting grout (Fig. 3.4) When filling, a water stop sheet 42 is temporarily installed to prevent grout 5 from flowing out from the end side of part 2, and is removed when installing the next lining. .

Then, the grout 5 is sufficiently filled from the injection hole 11 opened in the formwork 1 to the space between the coarse aggregates 21 in the part body 2 and the entire ground without any gaps.

At this time, since the member 2 of the present invention is a porous body, the filling process can be carried out while checking the filling condition inside.

After filling the grout 5, the formwork 1 is removed.

Then, as shown in FIG. 4, construction of one ring is completed with the member 2 remaining in the concrete.

After that, the same work is repeated while propelling the shield machine to complete the entire construction.

Water-stopping member, etc. (Fig. 3) In the above construction method, when the tail 3 of the shield machine is filled with grout 5, the tail 3 is restrained and smooth propulsion of the shield machine is hindered.

Further, if a cavity is formed between the tail 3 and the grout 5, water may enter the shield from the outside.

As a method to solve these problems, bags 4 and 41 are installed inside the tail 3, as shown in FIG.

During propulsion, the bags 4 and 41 are alternately inflated by water pressure or air pressure to promote smooth propulsion of the shield machine and to prevent water such as groundwater from entering the shield from the outside.

That is, the bags 4 and 41 are made of rubber, PVC sheet, etc.
When pouring the grout 5, the bag body 4 is inflated to secure a space between the tail 3 of the shield machine and the segment.

The bag 41 is then deflated to allow the grout 5 to be pushed out while resisting water ingress and to help fill the tail voids.

Further, when the shield machine excavates, the bag body 4 is deflated and the bag body 41 is inflated, and is brought into close contact with the existing shield lining to prevent water from entering.

Effects of the Present Invention> Since the present invention has been described above, the following effects can be expected.

In the conventional cast-in-place lining method, concrete mixed with coarse aggregate is placed directly between the formwork and the ground.

Therefore, while the concrete is hardening, it is susceptible to the effects of ground pressure and the reaction force of the shield jack, causing problems in construction accuracy such as deformation of the concrete structure.

In contrast, the present invention places a perforated cage with reinforcing bars and coarse aggregate inside between the tail of the shielding machine and the formwork, and fills the space between the formwork and the ground with early-strengthening grout. It is something.

Therefore, the perforated basket filled with this coarse aggregate can absorb and stop the reaction force of the ground pressure and shield jack.

Therefore, deformation of the concrete structure can be prevented and construction can be carried out favorably.

In the case of the cast-in-place lining method, concrete is placed directly between the formwork and the ground, so it is difficult to fill it with sufficient concrete.

Therefore, in the conventional method, a gap (tail void) is created between the concrete and the ground after pouring, which may cause ground subsidence.

However, in the present invention, coarse aggregate is not mixed, and a grout with extremely excellent fluidity is filled with a fluidizing agent and the like.

Therefore, it is possible to fill even a narrow place, and the grout can be sufficiently filled between the formwork and the ground without any gaps.

Therefore, the occurrence of tail voids can be prevented and the risk of ground subsidence can be avoided.

Previously, large machines such as concrete pumps had to be installed in a narrow work space, making it difficult to perform the work.

However, since the present invention uses grout, a simple injection machine is required, and the work can be simplified and speeded up.

Kuho〉In the past, in order to pour fluid concrete,
Workability is not very good as concrete flows into the shield.

However, in the present invention, semi-prefabrication can be achieved by surrounding the coarse aggregate and reinforcing bars with a thin body.

Therefore, it is possible to improve workability.

Kube> Since the member of the present invention is a porous body, the grouting can be carried out while checking the filling status of the grout inside.

Therefore, dense concrete structures can be constructed.

[Brief explanation of the drawing]

Figure 1: An explanatory diagram of the structure of the parts and formwork. Figure 2: An explanatory diagram of the state in which the formwork etc. are installed.

Claims (1)

[Claims] (1) Assemble the formwork inside the tail of the shield machine, and place a perforated cage with reinforcing bars and coarse aggregate inside between the tail and the formwork to prevent early strengthening between the formwork and the ground. A cast-in-place lining method in which a shield machine is propelled while filling with grout.