JPH116164A - Construction method for underground structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a deep underground structure without using such methods as pumping or freezing of underground water, and chemical grouting, prevent problems associated with pumping, reduce effects on the neighboring ground significantly, simplify an earth retaining wall and improve the quality of a building frame. SOLUTION: An earth retaining wall 10 is built in a position equivalent to an external wall of an underground structure, the ground inside the earth retaining wall 10 is excavated while pumping water there, beams 15a, 15b of the main body of a structure are built by a reverse winding method to a critical depth where they may not cause heaving. And then water is filled inside the earth retaining wall 10, the ground inside the earth retaining wall 10 is underwater-excavated to a final design depth without supporting, a slab for the main body of the structure for a position just above the underground water level inside the earth retaining wall 10 is placed, a space surrounded by the slab and the earth retaining wall 10 is made a sealed pace, underground water inside the earth retaining wall 10 is pushed down by supplying air to the sealed space, and the foundation and sole plates of the structure body are built in the sealed space in the air-compressed state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a high groundwater level,
The present invention relates to an underground structure construction method that is suitably used when a large depth structure such as a building basement or an underground parking lot is constructed on a ground where a large amount of groundwater springs, such as a highly permeable gravel ground.

[0002]

2. Description of the Related Art Conventionally, the following method has been generally used as a method of constructing a deep underground structure on a ground having a high groundwater level and high permeability. (1) Pumping method After closing off at the mountain retaining wall, the groundwater inside is pumped up with a deep well, etc., and excavation is performed while lowering the water level. This is a construction method. (2) Chemical solution injection method, ground improvement method After closing with a mountain retaining wall, a chemical solution is injected from the ground surface so that the ground deeper than the planned flooring floor becomes an impermeable layer to a depth that does not cause bulging. This is a method of mixing and stirring cement milk. (3) Freezing method With the same purpose as the method described in (2) above, this method is to freeze the ground deeper than the planned flooring board to build an impermeable layer. (4) Caisson method This is a method in which the inside of a building constructed on the ground or semi-underground is excavated underwater (open caisson), or dry excavation is performed while feeding air to a pressure balanced with the groundwater pressure, and the sediment is settled sequentially.

[0003]

However, the above-mentioned conventional method has the following problems. In the method (1), in the case of permeable ground with high groundwater level,
There were problems such as deformation of the surrounding ground due to pumping, damage to houses, well withering, deterioration of the quality of the building to be built, increased drainage sewage charges, increased construction costs due to the installation of wells, and long construction periods. In the method (2), when the construction area is large or when the ground to be impervious is deep, there are problems such as a significant increase in construction cost and construction period, and contamination of groundwater. The method (3) involves problems such as an increase in the construction cost and the construction period, a rise in the ground during freezing, and a decrease in the quality of the skeleton. In the construction method (4), in addition to the increase in construction cost and construction period, there are restrictions on the frame shape and wall thickness, as well as deformation of the surrounding ground and damage to the houses, alienation of the landscape at the time of construction, and pollution such as sound leakage. There were problems such as the generation of industrial waste associated with the removal of the temporary wall.

According to the present invention, when constructing a deep underground structure in a permeable ground having a high groundwater level, it can be constructed without taking a method of pumping and freezing groundwater, injecting a chemical solution, etc., thereby solving the above-mentioned problems. An object of the present invention is to provide an underground structure construction method that can be solved.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a mountain retaining wall is constructed at a location corresponding to the outer wall of an underground building, and the ground inside the mountain retaining wall is pumped while pumping. When the beam of the structure body is excavated to construct the beam of the structure body by the reverse winding method, and when the beam of the structure body is constructed to a predetermined depth, the inside of the retaining wall is flooded and the ground inside the retaining wall is unsupported. Underwater excavation to the final planned depth by the work, cast a structure body slab at a location just above the groundwater level inside the retaining wall, make the space surrounded by the slab and the retaining wall a sealed space, and It is characterized in that the air is supplied to push down the groundwater inside the retaining wall, and the foundation and bottom plate of the structure body are constructed in the sealed space in this compressed state. After the bottom is built, the air supply can be stopped and the rest can be built under normal pressure. In the invention according to claim 2,
When the mountain retaining wall is constructed, a straight pillar that can be used as a main body is constructed inside the retaining wall, and the straight pillar supports a beam and a slab of a structure body constructed by a reverse winding method. The invention according to claim 3 is characterized in that the structure slab is supported by a floating prevention anchor before air is supplied to the sealed space.

In the present invention, since the drainage for lowering the groundwater level is performed only to a shallow depth, there is almost no problem associated with pumping. Further, since the force acting on the retaining wall due to underwater excavation and pneumatic work can be reduced at a deeper depth, the influence on the surrounding ground can be significantly reduced, and the retaining wall can be simplified. Furthermore, since the pressure can completely prevent water leakage from the retaining wall, the quality of the skeleton is significantly improved. In addition, since the ground surface is completed early, regulations such as traffic regulations are completed in a short time.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an underground structure constructed by the method of the present invention. Here, an example of constructing an underground parking lot is shown. 1 (a) is a plan view of the first basement floor, FIG. 1 (b) is a plan view of the second basement floor, FIG. 2 is a sectional view taken along line AA of FIG. 1 (a), and FIG. It is sectional drawing which followed the surface. As shown in these figures, on the first basement floor, a plurality of incoming elevators 1..., A plurality of outgoing elevators 2
, And an entrance section 3 are provided, and the second basement floor below the elevator hall is a parking space 4.

The construction of such an underground structure is performed according to the following procedure. (1) Construction process of the retaining wall and the timber pillar As shown in FIG. 4, T is placed on the outer wall of the underground structure.
The retaining wall 10 is constructed by an RD continuous wall, a continuous underground wall, or the like. FIG. 4 shows an example in which a TRD connecting wall is constructed by the TRD excavator 10A. The mountain retaining wall 10 has sufficient strength and airtightness to withstand the pressure of the air fed from the inside as described later. In addition, a simple deep well 11 is installed in an inner portion surrounded by the retaining wall 10. This is for dry excavation to an excavation limit depth such as bulging of a board as described later. Further, in order to support a reverse-striking body, which will be described later,
From the ground. The straight pillar 12 is also used later as a permanent pillar. In FIG. 4, 13 is a reverse machine, 14
a indicates a first aquifer, 14b indicates a second aquifer, and 14c indicates a third aquifer.

(2) Construction process of RC section beam which also serves as slab beam of structure body by reverse winding method The skeleton of the underground structure is designed in advance with a beam structure, and as shown in FIG. While excavating, slab beams 15a, 15 of the main body of the structure are installed by installing anchor bars so as to be integrated with the retaining wall 10 and the trussed pillar 12.
b and the first basement side wall 16 are constructed. This method is repeated up to the excavation limit depth such as the bulging of the slab to construct a slab beam or the like of the structure body. These slab beams 15a, 15b and side walls 16 have an RC structure. In the figure, reference numeral 17 denotes a working truck crane.

(3) Final Flooring and Underwater Excavation Step As shown in FIG. 6, a temporary gantry 20 is laid on the uppermost slab beam 15a, and the inside of the retaining wall 10 is flooded. Underwater excavation is performed using the provided clamshell 21 and the like. The excavated soil is dehydrated by a pre-dryer or the like and then carried out. After the flooring is completed, the floating anchor 22 is pierced and fixed from the temporary gantry 20 using a boring machine 23 or the like.

(4) Construction of Structural Body Slab and Installation Process of Air Supply Device As shown in FIG. 7, after temporarily placing a base material 24 such as a reinforcing bar on a slab beam 15b on the second basement floor, a material lock 25a is provided. , A man lock 25b, and the like, and the structure main body slab 26 at a position just above the groundwater level is cast (see FIG. 8). That is, when the material lock 25a and the man lock 25b are closed, the structure main body slab 2 is closed.
A space 27 surrounded by the inner wall 6 and the retaining wall 1 is made a sealed space so that the space 27 can be kept airtight. In addition, after confirming the hardening of the concrete, the earth anchor 22 for preventing lifting is fixed to the structure main body slab 26 and the straight pillar 12.

(5) Compressed Air and Bottom Board Construction Process As shown in FIG. 8, a compressed air device 30 having a compressor 28, a receiver tank 29, and the like is installed on the ground, from which compressed air is sent to the sealed space 27 to remove groundwater. After being pushed down and completely removed, the overhead crane 31 is installed below the structure main body slab 26. Reference numeral 22a denotes a fixing portion of the earth anchor 22 to the frame of the structure main body. Further, in the dry state, the final floor is attached, a dowel is cast on the retaining core material and the timber pillar 12, and the foundation work of the structure body and the bottom concrete 33 are poured. All the necessary materials for these are put in the sealed space 27 before the air is compressed. As described above, since the operation is performed in the compressed air, water leakage from the retaining wall 10 and the connection portion of the main body can be completely prevented.

(6) Construction of the skeleton and the interior process While the pressure in the retaining wall 10 is being reduced, it is checked whether or not water has leaked. While stopping necessary water, the side walls 36 and the like on the second basement floor are sequentially wound under normal pressure. Build with. A dowel is cast into the core of the retaining wall and the timber pillar, and integrated with the structure body. After the construction of the structure body, the slab openings such as the stairs are removed. After that, if necessary, ancillary facilities such as elevators and interior work will be performed. In addition, the pillars and the earth anchors 22 for preventing lifting are fixed to the bottom of the structure main body as they are and used for lifting them. Through the above steps, the underground parking lot shown in FIGS. 1 to 3 can be constructed.

In the above-described embodiment, the slab 26 on the first basement floor is cast and the lower part of the slab is used as a sealed space. However, if the groundwater level is slightly lower, the slab on the second basement floor is used for forming a sealed space. May be used as a slab. In the above-described embodiment, the case where the underground parking lot is constructed by the method of the present invention has been described as an example. However, the method of the present invention can be applied to the case of constructing another underground structure.

[0015]

As described above, the present invention has the following excellent effects. The amount of pumped water for lowering groundwater will be greatly reduced, and problems such as deformation of the surrounding ground, well withering, and land subsidence will be reduced. The cross section of the retaining wall deeper than the underwater excavation portion can be small, and the deformation of the retaining wall is greatly reduced due to the formation of the support by reverse winding. Since the temporary gantry can be erected using the slab beam, the construction cost and the process are improved, and there is no deterioration in the frame quality such as box removal related to the support pile. As with caisson, air leakage from the cutting edge and earth and sand discharge is extremely small, and the air supply equipment can be small. There is no concern about pollution such as groundwater contamination related to chemical injection. There is almost no capacity burden on sewage and rivers for drainage, and construction costs related to sewage charges can be reduced. After the slab is constructed, the ground can be opened immediately, so there is little effect on the surroundings. In addition, if a straight pillar is constructed in advance and the beam of the structure body is supported by this, the beam of the structure body can be supported with high strength, which is suitable for constructing a large-scale underground structure. . Furthermore, if the structure slab is supported by the lifting prevention anchor, air can be sent to the sealed space under high pressure, and groundwater can be completely eliminated,
The lifting prevention anchor can be used for the main body as it is, and there are almost no unnecessary types of work after completion, such as pumping and ground improvement, and the cost and process are improved.

[Brief description of the drawings]

FIG. 1 shows an underground parking lot constructed by an underground construction method according to an embodiment of the present invention, wherein (a) shows an underground parking lot.
FIG. 2B is a plan view of the second floor of the basement.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a cross-sectional view along the other surface.

FIG. 4 is a sectional view showing a procedure of a method of constructing an underground structure according to the embodiment of the present invention.

FIG. 5 is a sectional view showing a procedure of a method of constructing an underground structure according to the embodiment of the present invention.

FIG. 6 is a sectional view showing a procedure of a method of constructing an underground structure according to an embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a procedure of a method for constructing an underground structure according to an embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a procedure of a method of constructing an underground structure according to an embodiment of the present invention.

FIG. 9 is a sectional view showing a procedure of a method of constructing an underground structure according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mountain retaining wall 12 Structural pillar 15a, 15b Slab beam 22 Earth anchor 26 Structure main body slab 27 Sealed space 30 Pneumatic device 33 Bottom concrete

Claims (3)

[Claims] An earth retaining wall is constructed at a location corresponding to an outer wall of an underground construction, and a ground inside the mountain retaining wall is excavated while pumping water to construct a beam of a structure main body by a reverse winding method. At the time of constructing to a predetermined depth, the inside of the retaining wall is flooded and the ground inside the retaining wall is excavated underwater to the final planned depth without any support, and hits directly above the groundwater level inside the retaining wall. A space surrounded by the slab and the retaining wall is cast into a sealed space, and air is supplied to the sealed space to push down the groundwater inside the retaining wall downward. The foundation of the structure itself in a sealed space,
Underground structure construction method characterized by the construction of a bottom. 2. The construction method according to claim 1, wherein when the retaining wall is constructed, a straight pillar is constructed inside the retaining wall, and the straight pillar supports a beam of a structure body constructed by a reverse winding method. Underground structure construction method described. 3. The underground structure construction method according to claim 1, wherein the structure slab is supported by an earth anchor for preventing lifting before air is supplied to the sealed space.