JP2874906B2 - Shaft construction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a shaft construction method, and in particular, can easily construct a shaft as a starting point and a reaching point of a shield excavator for road construction. Shaft construction method improved in this way.

[Conventional technology]

Recent road construction has become deeper and higher water pressure, and in a series of road constructions, the difficulty of vertical shaft construction has increased and the construction conditions have become more severe. As a conventional shaft construction method performed under such conditions, a method using a continuous wall and a reverse winding method, or a pneumatic caisson method is known. In the former method, the side wall is constructed while digging into the ground. First, after excavating to a certain depth, the process of laying a reinforcing bar on the surrounding wall and placing and curing concrete is performed.
In this process, the above-described process is repeatedly performed while sequentially digging down to build a shaft having a desired depth. In the latter method, excavation is performed while supplying pressure air to the caisson lower chamber and balancing it with the groundwater pressure, submerging it to a predetermined depth while maintaining the horizontal state of the caisson, installing the caisson as it is as a shaft wall .

[Problems to be solved by the invention]

However, the above-mentioned conventional construction method is a method of sequentially constructing a shaft wall below, and also requires the installation of a reinforcing bar, which causes a problem that the construction period is prolonged. In the latter case, there is a possibility that noise and vibration may be generated due to the installation of the compressed air compressor, and environmental destruction to the surroundings may occur. In addition, depending on the soil properties, the surrounding ground may sink. In the pneumatic caisson method, there is a method of excavating and sinking while improving the ground at the lower part of the cutting edge to prevent inclination and self-settling of the cutting edge.However, due to the use of compressed air, work efficiency deteriorates. The problem of causing is not improved.

The present invention focuses on the above-mentioned conventional problems, and can significantly reduce the construction period for building a shaft,
It is an object of the present invention to provide an effective shaft construction method that does not generate vibration or noise during construction and does not adversely affect the surrounding ground.

[Means for solving the problem]

In order to achieve the above object, a shaft construction method according to the present invention comprises forming a continuous soil retaining wall surrounding the planned shaft portion in advance by a mud solidification method, and then forming an open caisson inside the continuous soil retaining water wall. Was constructed, and the caisson was laid down inside the continuous retaining water wall to construct a shaft. In this case, the continuous earth retaining wall sets the root length protruding downward from the shaft bottom to about the shaft width length, prevents water from flowing into the planned shaft part, and applies the open caisson method as it is. I can do it. Further, as another invention, a continuous soil retaining wall surrounding the planned shaft is formed in advance by a mud solidification method, and a ground portion is formed at the bottom of the continuous soil retaining wall by a ground improvement method such as jet grout. And separating the planned shaft part from the surrounding ground, then constructing an open caisson inside the continuous retaining water wall and sinking the caisson along the inner wall surface of the continuous retaining water wall, Was configured to be built.

[Action]

According to the above configuration, since the continuous retaining water blocking wall is first formed by the muddy water solidification method along the peripheral wall of the planned shaft, there is no rebar construction or concrete casting, and it hardens early, so a large late shortening effect. There is. And, since the open caisson is laid down along the inner wall inside the continuous retaining water stop wall, stable burying work can be performed. In this case, by setting the interval between the inner wall of the continuous soil retaining water wall and the caisson side wall in a range in which the caisson inclination is allowed, a settlement guide function can be provided. If the ground is soft and has high water pressure, the open caisson method is adopted by setting the root length of the continuous soil retaining wall to such a length that water does not flow in from the ground water pressure and the cross section of the shaft. Applicable as it is. In addition, the ground part is formed by the ground improvement method such as jet grout at the lower part of the continuous soil retaining water wall,
If it is configured so that the planned shaft portion is separated and shielded from the surrounding ground in conjunction with the continuous soil retaining wall, the effect of preventing water rotation can be obtained as compared with the case where a deep continuous soil retaining water wall is formed. Therefore, groundwater does not flow into the planned shaft, and there is no adverse effect such as settlement of the surrounding ground. An open caisson is constructed in the enclosed shaft and is laid along the inner wall of the continuous retaining water wall, so that stable burial is performed and there is no compressor, so noise, vibration, and other pressure The construction can be carried out quickly without affecting the local residents due to air supply and exhaust.

〔Example〕

Hereinafter, specific examples 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 by a shaft construction method according to an embodiment. This vertical shaft construction method first forms a continuous earth retaining wall surrounding the planned shaft, so that the root cut length does not allow groundwater pressure in the surrounding ground to sneak into the interior surrounded by the continuous earth retaining wall. Set to. Thereafter, an open caisson is laid along the inner wall of the continuous retaining water wall in the separated planned shaft portion to construct a shaft.

First, the continuous soil retaining wall 12 is constructed around the planned shaft 10, which is constructed by mud solidification. That is, the groove 14 is excavated by a crawler bucket or the like so as to surround the area of the planned shaft 10. This groove
Reference numeral 14 denotes a width corresponding to the bucket width, and the groove 14 is excavated with a length of about 2 to 3 m as one element. After the first pre-drilling, a mud treatment facility is installed and a stable liquid (specific gravity: 1.15 to 1.20) mainly composed of bentonite is supplied to the groove 14 to excavate to a depth deeper than the caisson burial depth while muddy water is formed. . After the excavation, the muddy water is stirred and mixed by an air jet, and a hardening agent composed of sodium silicate and cement / additive is injected into the muddy water to be hardened. Such a process is performed over the entire circumference to construct a continuous retaining water stop wall 12 as shown in FIG. 3 (FIG. 1 (1)). In this case, if necessary, a continuous retaining water blocking wall 12 can be formed by inserting a reinforcing bar or a precast plate into the groove 14 and performing a reinforcing treatment. The continuous retaining water blocking wall 12 has an interval of 60 to 70 cm with a caisson described later, allows the caisson to be inclined at a certain limit, and supports a further inclination by the continuous retaining water blocking wall 12.

As described above, the continuous soil retaining wall 12 is set to be deeper than the planned pit depth H by a caisson, but in particular, the planned vertical shaft portion surrounded by the continuous soil retaining wall 12 from the surrounding ground.
The continuous retaining water barrier wall 12 is constructed deeper by the root cutting depth h necessary to prevent the water from flowing into the inside. This may be determined by a predetermined design procedure based on the water pressure of the surrounding ground, the sectional area of the shaft, and the like.

After performing the above pretreatment, a caisson 20 is constructed in the planned shaft 10. In this embodiment, as described above, since the continuous soil retaining wall 12 is constructed with the root cutting depth h that does not allow water to flow from the periphery than the planned shaft depth H and the waterproof wall is constructed, the open caisson method is used. The caisson 20 is an open caisson. First,
Firstly, primary excavation is performed on the surface of the planned shaft 10 for stable subsidence of the caisson 20. This is using a backhoe etc.
Drilling to a depth of ~ 2m, installing caisson blade 22,
Constructing the first lot skeleton 24 ₁ (FIG. 1 (2)). After the construction of the frame 24, the outer periphery of the blade 22 is backfilled. After that without a settlement excavation with building a second lot building frame 24 _2,
The work is repeatedly performed up to the setting depth of the shaft (the n-th lot body 24 _n ) (FIG. 1 (3)).

After the caisson 20 has been laid down to the planned shaft depth H in this manner, concrete is poured into the floor of the cutting edge 22 of the caisson 20 to form the floor 26, thereby forming the shaft 26.
28 will be built.

When the shaft 28 is used as a starting shaft of a shield excavator, a shield entrance 30 is opened on the inner wall of the shaft 28, but before the opening, the caisson 20 and the continuous retaining water stop wall 12 are opened.
When there is a risk that the ground between the two walls may collapse, the ground between the walls is hardened by injecting a chemical solution into the ground.
(Fig. 4). The hardened improved ground 32 does not erupt even when the shield entrance 30 is opened, so that the ground in the continuous retaining water blocking wall 12 does not sink. After such processing, the shield excavator
34 is lowered, the shield excavator 34 is launched from the opened shield entrance 30, and the back truss 3
6. The improved ground 32 and the continuous retaining water blocking wall 12 are penetrated through the temporary segment 38 to form a road (FIG. 1 (5)).

According to the shaft construction method according to the first embodiment,
Since the continuous retaining water barrier wall 12 is constructed in advance around the planned shaft 10 by mud solidification in advance, there is no need to build steel bars or cast concrete, and the construction period is significantly reduced compared to the reverse winding method. I can do it. Moreover, since the caisson method is in a state of being isolated from the surrounding ground by the continuous retaining water blocking wall 12, there is no groundwater flowing into the planned shaft 10 and the settlement of the surrounding ground due to the settlement of the caisson 20 and the underground Fluctuations in water level can be prevented. Further, since water is prevented from flowing into the planned shaft 10, it is not necessary to use the pneumatic caisson method. As a result, there is no noise and vibration associated with the use of the compressor due to air pressure,
The problem of the generation of oxygen-deficient air, the occurrence of occult disease and the reduction of work efficiency due to the correction of air pressure are also eliminated. In addition, since the improved ground 32 formed in the feeling of the wall of the continuous earth retaining wall 12 and the caisson 20 particularly when the shield excavator 34 starts moving is an improvement in a confined space, the improvement effect is large, and the shield entrance 30
The safety of opening work is improved and it is also economical.

FIG. 2 is a sectional view showing a construction procedure by a shaft construction method according to a second embodiment. In this shaft construction method, a continuous ground retaining wall surrounding the planned shaft is formed first, and a bottom part is formed by jet grout below the continuous ground retaining wall to make the planned shaft surrounding ground. Separate from Thereafter, an open caisson is laid along the inner wall of the continuous retaining water wall in the separated planned shaft portion to construct a shaft.

First, a continuous soil retaining wall 12 is constructed around the planned shaft 10, which is constructed by a mud solidification method as in the first embodiment. In other words, the stabilizing liquid is
And digging to a position slightly deeper than the caisson burial depth while muddy water is supplied. A hardener is injected and hardened while the muddy water is stirred and mixed by an air jet. Such processing is performed over the entire circumference to construct a continuous retaining water stop wall 12 as shown in FIG. 3 (FIG. 2 (1)).
This continuous soil retaining wall 12 also takes a distance of 60 to 70 cm with the caisson, allows the caisson to tilt at a certain limit,
Further inclinations are to be supported by the continuous retaining wall 12.

After constructing the continuous soil retaining wall 12, in the second embodiment, a step of closing the lower part of the continuous soil retaining wall 12 to separate the surrounding ground from the planned shaft 10 is performed. This is constructed by, for example, jig grout, and a pipe is inserted from the surface of the planned shaft 10 to a depth equivalent to the lower end of the continuous retaining water stop wall 12, and cement milk is introduced into the ground from a jet nozzle drilled at the tip of the pipe. Allow to penetrate and cure.
As a result, a core 16 is formed, and the pipe is inserted and grouted at regular intervals so that the core 16 is connected. By such processing, FIG. 2 (2)
As shown in the figure, a bottom portion 18 is constructed below the continuous retaining water blocking wall 12, and the inside of the planned shaft 10 is separated from the surrounding ground to provide a water blocking function.

After performing the two-step process as described above, a caisson 20 is constructed in the planned shaft 10. In this embodiment as well, the open caisson method can be adopted since the water blocking wall is constructed by the continuous retaining water blocking wall 12 and the open bottom portion 18, so that the caisson 20 is an open caisson. First, the planned shaft
The first excavation will be conducted on 10 surfaces for stable sinking of caisson 20 first. This is a primary excavation using a backhoe, etc.
Installation caisson cutting edge 22, to construct the first lot skeleton 24 ₁ (FIG. 2 (3)). After the construction of the frame 24, the outer periphery of the blade 22 is backfilled. Thereafter no subsidence drilling with constructing the second lot skeleton 24 ₂ repeatedly construction to shafts setting depth (the n lot skeleton 24 _n) (FIG. 2 (4)).

After the caisson 20 has been submerged in this way, the cutting edge 22 of the caisson 20 has come into contact with the bottom portion 18 or has reached a depth near the bottom portion 18.
The shaft 28 will be constructed by forming

When the shaft 28 is used as a starting shaft of a shield excavator, a shield entrance 30 is opened on the inner wall of the shaft 28, but before the opening, the caisson 20 and the continuous retaining water stop wall 12 are opened.
If there is a risk that the ground between the two walls may collapse, a chemical solution is injected into the ground between the walls to improve the hardened ground (second ground).
(FIG. 5). After such processing, the shield excavator 34 is lowered into the shaft 28, and the opened shield entrance 30 is opened.
Then, the shield excavator 34 is started, and the improved ground 32 and the continuous retaining water stop wall 12 are penetrated through the back truss 36 and the temporary segment 38 on the rear wall of the shaft 28 to form a road (FIG. 2). (6)).

FIG. 5 is a flowchart illustrating the steps of the second embodiment.

According to the shaft construction method according to the second embodiment,
Similar to the first embodiment, since the continuous retaining water barrier wall 12 is constructed in advance around the planned shaft 10 by the mud solidification method, there is no need to lay a reinforcing bar or cast concrete, and compared with the reverse winding method. Even so, the construction period can be significantly reduced. In particular, in the second embodiment, since the caisson method is in a state of being isolated from the surrounding ground by the continuous retaining water stop wall 12 and the bottom portion 18, it is possible to completely prevent groundwater from flowing into the planned shaft 10. The settlement of the surrounding ground due to the settlement of the caisson 20 and the fluctuation of the underground water level can be more reliably prevented. Since there is no need to use the pneumatic caisson method, there is no noise and vibration associated with the use of the compressor due to the pneumatic pressure, the effect on the surrounding basement and wells, the generation of oxygen-deficient air, the occurrence of scabs and the correction of pneumatic pressure. As in the first embodiment, there is no problem of lowering the work efficiency due to the above.

Note that the first embodiment and the second embodiment differ depending on whether the root depth h of the continuous retaining water blocking wall 12 is set to be long, or is shortened to construct the bottom 18 by the ground improvement method. But,
It is sufficient to adopt a construction method with low stability and construction cost in consideration of the current situation of the surrounding ground.

〔The invention's effect〕

As described above, according to the shaft construction method according to the present invention, the continuous retaining water blocking wall surrounding the planned shaft is formed in advance by the muddy water solidification method, and if necessary, the root cutting depth without water spillage. h, or by forming a ground portion at the bottom of the continuous retaining water blocking wall by a ground improvement method such as jet grout, to separate the planned shaft from the surrounding ground, and thereafter, the inside of the continuous retaining water blocking wall In order to construct an open caisson, to sink the caisson along the inner wall of the continuous soil retaining wall to build a shaft, it is possible to significantly reduce the construction period for the construction of the shaft, An excellent effect is obtained in that there is no generation of vibration, noise, or the like at the time of construction, and no adverse effects on the surrounding ground.

[Brief description of the drawings]

FIGS. 1 (1) to 1 (5) are explanatory views showing working steps of a shaft construction method according to a first embodiment of the present invention, and FIGS.
(6) is an explanatory view showing the working process of the shaft construction method according to the second embodiment, FIG. 3 is a plan view of the shaft construction state, FIG. 4 is a longitudinal sectional view of the same, and FIG. 5 is the second embodiment. It is a flowchart of the working process of the shaft construction method in FIG. 10 ... Scheduled shaft, 12 ... Continuous earth retaining wall, 18 ... Bottom, 20 ... Open caisson, 32 ... Improved ground.

Claims (2)

(57) [Claims] 1. A method for solidifying a continuous retaining water wall surrounding a planned shaft portion by a mud solidification method in advance by setting a root cutting length projecting downward from a shaft bottom portion to approximately a shaft width length, and then forming the continuous water blocking wall. A shaft construction method, comprising: constructing an open caisson inside a retaining water wall, and constructing a shaft by sinking the caisson inside the continuous retaining water wall. 2. A continuous retaining water wall surrounding the planned shaft is formed in advance by a mud solidification method, and a bottom portion is formed on the bottom of the continuous retaining water wall by a ground improvement method such as jet grout. Separate the planned shaft from the surrounding ground,
Thereafter, an open caisson is constructed inside the continuous retaining water wall, and a shaft is constructed by sinking the caisson inside the continuous retaining water wall.