JPH0381421A - Shaft construction method - Google Patents

Abstract

PURPOSE:To shorten the period of construction by forming a continuous water cut-off retaining wall surrounding the circumference of a site where a shaft is scheduled to be sunk, forming an open caisson inside the water cut-off wall, and sinking the caisson inside the water cut-off wall. CONSTITUTION:A continuous water cut-off retaining wall 12 surrounding the circumference of a site where a shaft is intended to be sunk, is formed. Plural lots of caissons are then formed inside the water cut-off wall in sequence to sink a caisson 20. Concrete is then placed on the floor face beneath a cutting edge part of the caisson 20 to form a floor ground 26, and then a shaft 28 is constructed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a shaft construction method, and in particular to a method for easily constructing a shaft that serves as a starting point and a destination point for a shield excavator for tunnel construction. Concerning a shaft construction method that has been improved to enable the construction of vertical shafts.

[Conventional technology]

Recently, tunnel construction has been carried out at great depths and under high water pressure, making vertical shaft construction more difficult and stricter in terms of construction conditions. Conventional shaft construction methods used under such conditions include the continuous wall and reverse winding method, and the Niematic caisson construction method.

In the former method, the side walls are built while digging into the ground.After first excavating to a certain depth, one step is to install reinforcing bars on the surrounding wall, and then to place and cure concrete. The process is repeated to build a vertical shaft of the desired depth.The latter method involves supplying pressurized air to the lower chamber of the caisson and excavating while balancing it with the groundwater pressure to maintain the horizontal state of the caisson. The caissons will be installed by being buried to a predetermined depth, and the caisson will be used as a shaft wall.

[Invention tries to solve! ! [lIB] However, in the above-mentioned conventional construction method, the shaft walls are constructed sequentially downward, and the installation of reinforcing bars is also required, so there is a problem that the construction period becomes long. Moreover, in the latter case, the installation of a compressor for compressed air generates noise and vibration, which may cause environmental damage to the surrounding area. Moreover, depending on the soil quality, there was a risk that the surrounding ground would sink. In addition, in the pressurized air caisson construction method, while improving the ground below the cutting edge to prevent the cutting edge from tilting and preventing scuttling, the work efficiency deteriorates due to the use of force mame, which is also known as a method of excavating and sinking. The problems causing this have not been improved.

The present invention focuses on the above-mentioned conventional problems, and can significantly shorten the construction period for constructing a shaft, and also eliminates the generation of vibrations and noise during construction, which does not adversely affect the surrounding ground. The purpose of this project is to provide an effective method for constructing a shaft that does not cause any damage.

(Means for Solving Problem L1) In order to achieve the above object, the shaft construction method according to the present invention includes forming a continuous earth retaining water-stop wall surrounding the planned shaft portion in advance by a mud solidification method, and then An open caisson is constructed inside the continuous earth retaining water cutoff wall, and a vertical shaft is constructed by sinking the caisson inside the continuous earth retention water cutoff wall.In this case, the continuous earth retention water cutoff wall If the length of the root cut protruding downward from the bottom of the shaft is set to approximately the width of the shaft, water will be prevented from entering the planned shaft area, and the open caisson construction method can be applied as is. In advance, a continuous earth retaining water stop wall surrounding the planned shaft area is formed using a mud solidification method, and a bottom layer is formed at the bottom of this continuous earth retaining water stop wall using a ground improvement method such as jet grouting to form a bottom part of the planned shaft area. is separated from the surrounding ground, and then an open caisson is constructed inside the continuous earth retaining water-stopping wall, and the caisson is sunk along the inner wall surface of the continuous earth-retaining water-stopping wall to construct a shaft. Configured.

[Effect]

According to the above configuration, a continuous earth retaining water stop wall is first formed along the circumferential wall of the planned shaft area using the mud solidification method, so there is no need to build reinforcing bars or place concrete, and it hardens early, resulting in a significant shortening effect in the later stages. There is.

Since the oven caisson is sunk along the inner wall inside the continuous earth retaining water stop wall, stable immersion construction can be performed. In this case, by setting the distance between the inner wall of the continuous earth retaining water stop wall and the caisson side wall to a range that allows the caisson inclination, a sinking guide function can be provided. If the ground is soft and the water pressure is high, the open caisson construction method can be used by making the cut length of the continuous earth retaining water stop wall long enough to prevent water from flowing around due to the ground water pressure and the cross-sectional area of the shaft. It can be applied as is. In addition, a bottom layer will be formed at the bottom of the continuous earth retaining water cutoff wall using a ground improvement method such as jet grouting, and together with the continuous earth retaining water cutoff wall, the planned shaft will be separated and shielded from the surrounding ground. Ba,
The effect of preventing water leakage can be obtained by forming a deep continuous earth retaining wall.

For this reason, groundwater will not flow into the planned shaft area, and there will be no adverse effects such as subsidence of the surrounding ground.Open caissons will be constructed in this enclosed planned shaft area, and will be installed along the inner wall of the continuous earth retaining water stop wall. Because the system is submerged, stable burying is achieved, and since there is no use of a compressor, construction can be carried out quickly without noise, vibration, or other effects on surrounding residents due to normal air supply and exhaust.

[Example] Hereinafter, a specific example of the shaft construction method according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing a construction procedure using a shaft construction method according to an embodiment. This shaft construction method first forms a continuous earth retaining water stop wall surrounding the planned shaft area, and the length of the root cut is such that groundwater pressure in the ground in the same area wraps around the area surrounded by the continuous earth retaining water cut wall. Set it so that there is no Thereafter, a shaft is constructed by sinking an oven caisson into the separated planned shaft portion along the inner wall of the continuous earth retaining water stop wall.

First, a continuous earth retaining water stop wall 12 is constructed around the planned shaft portion 10, and this is constructed by a muddy water solidification method. That is, a groove 14 is excavated using a crawler packet or the like so as to surround the area of the planned shaft portion 10 .

This groove 14 has a width corresponding to the packet width and a length of 2~
Excavate approximately 3m as one element. After the first shake, muddy water treatment equipment is installed and a stable liquid (specific gravity 1.15 to 1.20) mainly composed of bentonite is supplied to the trench 14 to turn it into muddy water. excavate until After this excavation, the muddy water is stirred and mixed using an air jut, and a hardening agent consisting of sodium silicate, cement, and additives is injected into the muddy water and hardened. This process is performed all around the 3rd I! I
A continuous earth retaining water stop wall 12 as shown in the figure is constructed (
In this case, reinforcing bars or precast plates may be inserted into the grooves 14 as needed to form an i-reading retaining water stop wall 12 that has been reinforced. This continuous earth retaining water stop wall 12 has an interval of 60 to 70 C1 between it and the caisson, which will be described later, and allows the inclination of the caisson within a certain limit.
A slope greater than that is supported by a continuous earth retaining water stop wall 12.

In addition, the continuous earth retaining water stop wall 12 is set deeper than the planned depth H of the shaft formed by the caisson as described above, but in particular, water from the surrounding ground into the planned shaft portion 10 surrounded by the continuous earth retaining water stop wall 12 is A continuous earth retaining water stop wall 12 is constructed deep by a root cutting depth h necessary to prevent detouring. This can be determined using a predetermined design procedure based on the water pressure of the surrounding ground, the cross-sectional area of the shaft, etc.

After performing the above-mentioned pretreatment, a caisson 20 is constructed in the planned shaft portion lO. In this embodiment, as described above, the continuous earth retaining water cutoff wall 12 is constructed with a cutting depth h that prevents water from entering from the surrounding area than the planned depth H of the shaft, and the water cutoff wall is constructed using the oven caisson construction method. Therefore, the caisson 20 is called an oven caisson.

First, the caisson 20 is first
Primary excavation is carried out to ensure stable burial of the caisson.
2, and construct the first lot frame 24 (the first
Figure (2)), after constructing this frame 24, the outer periphery of the cutting edge 22 is backfilled, and from then on, the second lot frame 24 is covered with snow and subsidence excavation is performed to reach the shaft setting depth (nth lot ant body 24). .) (1st rM (3)).

After the caisson 20 has been sunk to the planned depth H of the shaft in this manner, the shaft 28 is constructed by pouring concrete on the floor surface of the cutting edge 22 of the caisson 20 to form a floor plate 26. That will happen.

When the shaft 28 is used as a starting shaft for a shield excavator, a shield entrance 30 is opened in the inner wall of the shaft 28, but before this entrance, the ground between the caisson 20 and the continuous earth retaining water stop wall 12 collapses. If there is a risk of
A chemical solution is injected into the ground between the walls to harden the ground (Fig. 1 (4)).

The improved ground 32 hardened by this will not erupt even if the shield entrance 30 is opened, so the ground within the continuous earth retaining water stop wall 12 will not sink.After such treatment, the inside of the shaft 28 The shield excavator 34 is lowered to the ground, the shield excavator 34 is started from the opened shield entrance 30, and the back truss 36 is attached to the rear wall of the shaft 28, and the improved ground 32 is installed via the temporary segment 38, and the continuous earth retaining water stop g! 12 to form a tunnel (Fig. 1 (5)).

According to the shaft construction method according to the first embodiment, since the continuous earth retaining water stop wall 12 is constructed in advance around the planned shaft portion 10 by the mud solidification method, there is no need to build reinforcing bars or pour concrete. Moreover, compared to the reverse winding method, the construction period can be significantly shortened. Moreover, since the caisson construction method is isolated from the surrounding ground by the continuous earth retaining water stop wall 12, there is no leakage of groundwater into the planned shaft 10, and
Subsidence of the surrounding ground and fluctuations in underground water level due to the subsidence of the caisson 20 can be prevented. Since water is prevented from flowing into the planned shaft 10, there is no need to use the pressure caisson construction method.This eliminates the noise and vibrations associated with the use of compressors caused by pressure, and does not allow water to flow into surrounding basements or wells. This also eliminates the problems of the influence of water, the occurrence of oxygen-deficient air, the occurrence of latent disease, and a decrease in work efficiency due to air pressure correction. In particular, the improved ground 32 formed between the continuous earth retaining water stop wall 12 and the wall of the caisson 20 when the shield excavator 34 starts is improved in a restricted space, so the improvement effect is large, and the improvement effect is large. The safety of opening work is improved and it is also economical.

FIG. 2 is a sectional view showing a construction procedure using a shaft construction method according to a second embodiment. In this shaft construction method, a continuous earth retaining water stop wall is first formed surrounding the planned shaft area, and a bottom layer is formed by jet grouting at the bottom of this continuous earth retaining water stop wall, and the planned shaft area is connected to the surrounding ground. Separate from. Thereafter, a shaft is constructed by sinking an open caisson along the inner wall of the continuous earth retaining water stop wall in the separated planned shaft portion.

First, a continuous earth retaining water stop wall 12 is constructed around the planned shaft portion IO, which is constructed by the muddy water solidification method as in the first embodiment. That is, while supplying a stabilizing liquid to the groove 14 for each element to turn it into muddy water, excavation is carried out to a position slightly deeper than the caisson burial depth, and while the muddy water is stirred and mixed by an air jet, a hardening agent is injected and hardened. By performing this treatment all around the perimeter, a continuous earth retaining water stop wall 12 as shown in Figure 3 is constructed (Figure 2 (1)
), this continuous earth retaining water stop wall 12 also has an interval of 60 mm from the caisson.
~70 cm, allowing the inclination of the caisson within a certain limit, and further inclinations are supported by the continuous earth retaining water stop wall 12.

After constructing such a continuous earth-retaining water-stopping wall 12, in this second embodiment, a step is performed to close the lower part of the continuous earth-retaining water-stopping wall 12 to separate the surrounding ground from the planned shaft portion IO. For example, it is constructed using jet grouting, in which a pipe is inserted from the ground surface of the planned shaft portion IO to a depth equivalent to the lower end of the continuous earth retaining water stop wall 12, and cement milk is infiltrated into the ground from a jet nozzle drilled at the tip of the pipe. Let it harden. This forms the core 16, and the pipes are inserted and grouted at regular intervals so that the cores 16 are connected. Through such treatment, as shown in Fig. 2 (2), a bottom section 18 is constructed at the lower part of the continuous earth retaining water stop wall 12, and the inside of the planned shaft section 10 is separated from the surrounding ground to provide a water-blocking function. There is.

After performing the two-step treatment as described above, the shaft planned area 10
Construct caisson 20. In this embodiment as well, the water stop wall is constructed by the continuous earth retaining water stop wall 12 and the bottom plate 18, so the open caisson construction method can be adopted, and therefore the caisson 20 is an open caisson. First, primary excavation is performed on the ground surface of the planned shaft 10 in order to stably bury the caisson 20. This is done using a backhoe, etc., and the caisson tip 22 is installed, and the first lot inert body 24+ is constructed. (Fig. 2 0)), this frame 24
After construction, the outer periphery of the cutting edge 22 is backfilled.

Thereafter, the second lot frame 248 is constructed and submerged excavation is performed, and the construction is repeated until the vertical shaft is set to the depth (nth lot frame 24,) (FIG. 2 (4)).

After the caisson 20 has been sunk in this way, the cutting edge 22 of the caisson 20 touches the bottom plate 18 or has reached a depth close to the bottom plate 18, and concrete is poured on the floor surface to remove the bottom plate 26. By forming the shaft 28 will be constructed.

When the shaft 28 is used as a starting shaft for a shield excavator, a shield entrance 30 is opened in the inner wall of the shaft 2a. ! If there is a risk of the slab collapsing, improve the ground by injecting chemicals into the ground between the walls to harden it (Figure 2 (5)).

After such processing, a shield excavator 3 is installed in the shaft 28.
4 was lowered, the shield excavator 34 was started from the opened shield entrance 30, and the back truss 36 was inserted into the rear wall of the shaft 28, and the improved ground 32 and the continuous earth retaining water stop wall 12 were penetrated through the temporary segment 3 days. They form roads (Figure 2 (6)).

Section 5yJ shows a flowchart explaining the steps of the second embodiment described above.

According to the shaft construction method according to the second embodiment, similar to the first embodiment, in order to construct the continuous earth retaining water stop wall 12 in advance around the planned shaft portion 10 by the mud solidification method, the construction of reinforcing bars is required. There is no pouring or pouring of concrete, and the construction period can be significantly shortened compared to the reverse wrapping method. In particular, in this second embodiment, since the caisson construction method is used in a state where it is isolated from the surrounding ground by the continuous earth retaining water stop wall 12 and the bottom plate 18, it is possible to completely prevent groundwater from flowing into the planned shaft area IO. This makes it possible to more reliably prevent subsidence of the surrounding ground and fluctuations in the underground water level due to the subsidence of the caisson 20. Also, since there is no need to use the pressure caisson construction method, there is no noise or vibration associated with the use of compressors caused by pressure (
Similarly to the first embodiment, there are no problems of influence on surrounding basements and wells, occurrence of oxygen-deficient air, occurrence of incubation disease, and reduction in work efficiency due to air pressure correction.

In addition, the difference between the first and second embodiments is whether the root cut depth h of the continuous earth retaining water stop wall 12 is made longer, or whether it is made shorter and the bottom part 18 is constructed by the ground improvement method. However, this can be done by considering the current state of the surrounding ground and adopting a construction method that is more stable and less expensive.

〔Effect of the invention〕

As explained above, according to the shaft construction method according to the present invention, a continuous earth retaining water-stop wall surrounding the planned shaft area is shaped in advance by a mud water solidification method, and roots are cut as necessary to prevent water from entering. The planned shaft part is separated from the surrounding ground by forming a bottom part with a depth h or by forming a bottom part at the bottom of the continuous earth retaining water cut-off wall using a ground improvement method such as jet grouting, and then the continuous earth retaining water cut-off wall is An oven caisson is constructed inside the shaft, and the shaft is constructed by sinking the caisson along the inner wall of the continuous earth retaining water stop wall. Therefore, the construction period for constructing the shaft can be significantly shortened. In addition, excellent effects such as no generation of vibration or noise during construction and no adverse effects on the surrounding ground can be obtained.

[Brief explanation of drawings]

FIGS. 1 (1) to (5) are explanatory diagrams showing the work steps of the shaft construction method according to the first embodiment of the present invention, and No. 211ffl (1)
) to (6) are explanatory diagrams showing the work process of the shaft construction method according to the second embodiment, FIG. 3 is a plan view of the shaft construction state, and FIG.
The figure is a longitudinal sectional view of the same, and FIG. 5 is a flowchart of the working process of the shaft construction method in the second embodiment. 10... Planned shaft part, 12... Continuous earth retaining water stop wall, 18... Bottom plate part, 20...
Open caisson, 32...improved ground.

Claims (1)

[Scope of Claims] (1) After forming in advance a continuous earth retaining water cutoff wall surrounding the planned shaft portion by a mud water solidification method, an open caisson is constructed inside the continuous earth retention water cutoff wall, and the continuous earth retaining water cutoff wall is constructed in advance. A shaft construction method characterized in that a shaft is constructed by sinking the caisson inside a water-stop wall. (2) The method for constructing a shaft according to claim 1, wherein the continuous earth retaining water stop wall has a root cutting length that projects downward from the bottom of the shaft and is set to be approximately the width of the shaft. (3) In advance, a continuous earth retaining water stop wall surrounding the planned shaft portion is formed using the mud solidification method, and a bottom layer is formed at the bottom of this continuous earth retaining water cut wall using a ground improvement method such as jet grouting. Separating the planned portion from the surrounding ground, then constructing an open caisson inside the continuous earth retaining water cutoff wall, and constructing the shaft by sinking the caisson along the inner wall of the continuous earth retention water cutoff wall. A vertical shaft construction method characterized by: