JPS6250594A - Primary coating of tunnel with concrete - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a concrete primary lining method for tunnels. This method adopts a method in which concrete is filled between the holes, and the formwork is a movable formwork, and the concrete to be filled develops strength in a short time and has a long pot life required for filling work. It is characterized by being an expandable concrete.

(Prior Art) Tunnel excavation is carried out every few meters in a cycle of drilling, charging, blasting, scraping, and spraying. The area excavated through this cycle is called a single excavation unit. When the excavation of one excavation unit is completed, a primary lining with concrete is immediately applied to preserve the surface of the ground excavation. Subsequently, excavation of the next excavation unit is started.

Currently, the primary concrete lining is carried out by concrete spraying, but a large amount of dust is generated during concrete spraying, which significantly worsens the working environment inside the tunnel, which is a closed space. Furthermore, the loss rate of concrete due to splashing and spalling is large, and there is also a problem in economic efficiency.

A concrete-method lining method (referred to as the formwork method) is performed by installing formwork within the excavation unit for primary lining and filling the gap between the excavated ground surface and the formwork with concrete. However, this method has the following drawbacks and is not suitable for implementation.

That is, the first drawback is that the assembly and disassembly of the formwork must be repeated for each excavation unit, making the work complicated. −The area near the tunnel face where the lining will be carried out is originally a narrow space.
The space has become increasingly congested due to the installation of machinery for excavating the face. Assembling and disassembling formwork within such a space poses operational problems. Second
The disadvantage of concrete is that the strength development of concrete is slow. −
Unless the concrete applied to the method lining reaches a certain strength, the next excavation unit cannot be started. This strength (referred to as demolding strength) is empirically estimated to be around 30 kf/-, but it takes K1 days to reach this strength with ordinary concrete, so the excavation speed of tunnels with long work intervals between excavation units is slow. Become.

The third drawback is that the degree of adhesion between the filled concrete and the excavated surface of the earth is low.The excavated surface of the earth is not smooth but has many irregularities, so simply filling the concrete and the excavated surface of the earth Good adhesion is difficult to obtain.

In the case of concrete spraying, there is no need for formwork, and since a fast-setting agent is used to prevent flaking, etc., the above-mentioned strength can be achieved in a short time. Furthermore, since the concrete adheres closely to the ground excavation surface due to the spraying pressure, there is no problem in terms of adhesion. For this reason, the spraying method is still practiced as a primary lining method, despite the serious problems such as dust generation.

(Problems to be Solved by the Invention) The present invention adopts a formwork method that does not have the disadvantage of deteriorating the working environment as a concrete method for lining tunnels.
The purpose of this method is to solve the above-mentioned problems in this method.

Thus, the first problem mentioned above, which is the complexity of assembling and disassembling the formwork, was solved by using a movable formwork that can be moved in the tunnel axis direction while the formwork is assembled. In addition, we decided to solve the second problem, which is that it takes a long time to reach demolding strength, by adding an accelerating agent, but adding an accelerating agent causes the concrete to slump rapidly. It becomes impossible to fill the formwork. In order to secure this working time, a retardant was added, and in the end,
The second problem was solved by the combined addition of an accelerating agent and a retarding agent. The third problem, which was that the degree of adhesion between the concrete and the ground excavation surface was low, was solved by adding foamable metal powder to give the concrete an appropriate expansion.

(Means for Solving the Problems) The present invention provides the following features: (a) - In the primary lining of the excavated ground surface of a tunnel with concrete, A movable formwork that can be moved in the assembled state in the direction of the axis of the tunnel is provided, and (b) an accelerating agent, a retarder, and a foaming metal powder are placed in the gap between the movable formwork and the ground excavation surface. (c) After the concrete reaches a predetermined demolding strength, move the movable formwork to the location of the next excavation unit, and repeat this process to remove concrete from the ground excavation surface. This is a concrete-method lining method for a tunnel, which is characterized by forming a lining.

The movable formwork has a length commensurate with the length of one excavation unit, and can be moved in the axial direction of the tunnel by means of rails laid within the tunnel. This formwork is designed to minimize the number of formwork reinforcement tools (shoring, reinforcing ribs, etc.) installed in the space so as not to interfere with work in the space where the tunnel formwork is installed, and to prevent protrusions. It is desirable that the structure is such that only Note that the distance between the movable formwork and the ground excavation surface is usually about 10 to 20 m.

The quick-setting agent used in the present invention is an admixture that has the ability to set concrete within a few minutes by adding a few inches (referred to as the amount used) based on the cement weight in concrete, and is used for spraying concrete. It is used as an quick setting agent.

To illustrate this, examples of inorganic salts include alkali carbonates, alkali aluminates, and mixtures of both, and examples of cements include calcium aluminates and calcium sulfoaluminates. There are also mixtures of inorganic salts and cement.

The retarders used in the present invention are those used as retarders for concrete, and examples include lignin sulfonate, oxycarboxylate (typically gluconate), hyrisaccharide (41F Kosho 42-
No. 12436), Steffen waste liquid system (Special Publication No. 1973-
28290), and mixtures of two or more thereof.

The foamable metal powder used in the present invention is a metal powder that generates gas by reacting with alkaline water in concrete, and includes aluminum powder, zinc powder, tin powder, etc., but is usually aluminum powder. is used.

In the present invention, any means may be used to incorporate the quick-setting agent, retarder, and foamable metal powder into the concrete, as long as these three are ultimately included. , the following embodiments are preferred. That is, concrete mixed in a plant outside the tunnel is transported to a location close to a concrete pumping device installed inside the tunnel. This concrete is placed in a remixer, and a retarder and foamable metal powder are added and remixed. This concrete is placed in a line mixer and an accelerating agent is added. A line mixer is a horizontal continuous mixer with a set of screws, and when concrete and quick-setting agent are continuously charged from one port, a uniform mixture of the two is continuously discharged from the other port. This discharged concrete is transported by a concrete pumping device (a pump, a placer 1, etc.) via a transport pipe to the location of the movable formwork, and is filled into the void space between the formwork and the ground excavation surface.

It is preferable to choose the timing of adding the quick setting agent so that the time interval from when it is added to the concrete until it is filled into the formwork is as short as possible, and it should be added at the latest time of all the admixtures. choose to It is preferable to add the retarder at the same time as or before the addition of the accelerating agent.

Since retardants generally also have the effect of increasing the slump of concrete, it is better to use this effect to also function as a fluidizer for fluidized concrete IJ - in order to improve the performance of concrete. It is preferable. The above-mentioned addition in the re-kneading mixer is intended to function as a fluidizing agent. Of course, the retarder may be added to the concrete from the beginning.

Since foaming of the foamable metal powder starts immediately when it is added to concrete, in order to effectively utilize the expansion of concrete due to foaming, it is preferable that the time interval between the addition of the powder and concrete construction be as short as possible. From this point of view, it is better to add it into a line mixer, but since line mixers have a short crosstalk time, it is difficult to expect uniform mixing of the foamable metal powder. For this reason, it is added to a remixing mixer (a normal tilting concrete mixer) which has a long kneading time and good kneading efficiency.

The appropriate slump of concrete to be filled into the gap between the movable formwork and the ground excavation surface is about 10 to 15 times.
It is necessary that the 6-hour strength be around 30 kr/J. In addition, in view of the requirements for primary covering concrete as a structural material, it is necessary that the 28-day strength be 180'q/l-1ili or more.

Further, it is also necessary that the workability of the concrete after addition of the quick-setting agent is such that the filling operation can proceed smoothly, that is, the pot life of the concrete is around 30 minutes.

Ready-mixed concrete can be used as the concrete mixed in the seven runts outside the tunnel in the above embodiment. Further, it is preferable to use an organic sizing agent such as methylcellulose or a fine mineral powder such as silica hneem in combination in order to improve the workability and performance of concrete.

The concrete-lined method of the present invention includes a full-section excavation method,
Applicable to tunnel-horizontal construction methods such as pincer cut construction method.

After the primary lining, a secondary concrete lining, which is full-scale concrete lining, will be constructed. In addition, during the primary lining,
It is more preferable to press the concrete against the formwork by applying a force that presses it in the direction of the excavated surface of the ground, in order to improve adhesion.

(Function) The quick-setting agent of the present invention speeds up the setting and hardening of concrete and shortens the time to reach the required demolding strength, but on the other hand, it has the disadvantage of causing the concrete to quickly lose its workability and shortening its pot life. . Since a retarder has the effect of retarding the setting of concrete, if it is used in combination with an accelerating agent, the disadvantage of shortening the pot life can be alleviated. However, using a retardant in combination tends to weaken the setting and hardening accelerating effect of the quick-setting agent, so the quick-setting agent should be used in order to achieve the required time to reach the required demolding strength, the required pot life, and the required 28-day strength. The combination of the type and amount of retarder to be used must be selected. Although these combinations vary depending on the type of cement, brand, construction temperature, and the type and amount of other admixtures used, generally preferred combinations are as follows. That is, a combination of an inorganic salt-based quick-setting agent and a polysaccharide or a stephen waste liquid-based retardant, and a combination of a cement-based quick-setting agent and an oxycarboxylic acid salt or a +7 gunin sulfonate. Therefore, the appropriate amounts to use are 3 to 10% for inorganic salt-based quick-setting agents, 3 to 10% for cement-based quick-setting agents, and 0.1 to 1% for polysaccharide and Steffen waste liquid-based retarders. (solid content equivalent)
, oxycarboxylic acid salts range from 0.05 to 0.5 thi, and lignin sulfonates range from 0.1 to 1 thi.

The foamable metal powder in the present invention gives expansion to concrete and has the effect of increasing the degree of adhesion between the concrete and the excavated surface of the earth. The appropriate amount to use is 0°001~0.1% (
Preferably it is 0.005 to 0.05 inch).

(Example) A test example in which an quick setting agent, a retarder, and foamable metal powder are added to concrete is shown below.

Concrete is produced using the fluidization method; the mix of concrete is as shown in Table 1.

Table 1 * - Zoris sro < yf Zoris Bussan ■ Released water-reducing agent standard form) 100 plums 25 Qml! Five minutes after finishing mixing the base concrete used, an accelerating agent, an arc retarder, and aluminum powder were added, and the mixture was re-kneaded and fluidized. The results are shown in Table 2.

In the above table, the pot life of Mu 2 and Ri 4 was about 30 minutes.

As is clear from the table above, when no retardant is used (41
and 43) immediately started to set and the workability was extremely poor, but when a retarder was used together (42 and A4)
The onset of setting was delayed, resulting in a pot life of about 30 minutes. Moreover, both the 6-hour strength and 28-day strength were able to meet the targets.

(Effects of the invention) Since the present invention performs concrete lining using a formwork method rather than a spraying method, there are disadvantages associated with the spraying method (deterioration of the working environment due to generation of large amounts of dust, splashing, flaking, etc.). The primary lining can be carried out without any loss of concrete due to oxidation, difficulty in controlling the concrete mix, etc.).

It has the following advantages compared to the conventional formwork method.

(a) Using a movable formwork also eliminates the need to assemble and disassemble the formwork for each excavation unit, resulting in a large labor-saving effect.

(b) By using a combination of an accelerating agent and a retarder, the time required to reach demolding strength is as short as when using only an accelerating agent, yet sufficient pot life can be ensured.

(c) As a result of expanding the concrete using the foamable metal powder, the degree of adhesion between the concrete and the excavated surface of the earth can be improved.

) There is no adverse effect on the 28-day strength development of concrete. (
The 28-day strength of Bread 2 and Bread 3 is slightly lower, but this is commensurate with the decrease in strength caused by the inclusion of air bubbles during expansion.) (E) When using the fluidization method, Ready Mix This makes it possible to use concrete, eliminating the need to set up a concrete plant at the tunnel site.

As described above, the present invention has solved many problems in the conventional concrete lining of tunnels.

Claims (1)

[Scope of Claims] 1. When performing primary lining of the excavated ground surface of the tunnel with concrete, (a) At the location of the excavation unit where the primary lining is to be performed, an assembled state in the axial direction of the tunnel is provided. (b) Fill the gap between the movable formwork and the ground excavation surface with concrete containing an quick-setting agent, a retarder, and foamable metal powder (c) After the concrete reaches a predetermined demolding strength, the movable formwork is moved to the location of the next excavation unit, and this process is repeated thereafter, thereby lining the excavated surface of the ground with concrete. Primary concrete lining method