JP3107774B2 - Buildings around underground structures and construction method on soft ground - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a construction provided around an underground structure constructed on soft ground and a construction method thereof. More specifically, the present invention relates to a structure around an underground structure which is constructed prior to constructing an underground structure such as a drainage channel, an irrigation canal, and a culvert on a soft ground across a road, and a construction method thereof.

[0002]

2. Description of the Related Art When constructing underground structures such as drainage channels, irrigation canals, and culverts across a road on a soft ground where the thickness of a buried layer or an alluvial layer is thick, the bottom area of the underground structure It is necessary to excavate the soft ground deeply, almost correspondingly. Prior to this excavation, several steel sheet piles were driven into the part facing the side of the underground structure as earth retaining walls, and the surrounding area was surrounded by A construction method is known in which a cutting beam is passed between facing steel sheet piles to support the earth pressure from the side working on a retaining wall of the steel sheet pile by the compression resistance of the cutting beam. In addition, instead of steel sheet piles, a soil-cement column consisting of multiple soil-cement columns is obtained by mixing excavated soil and a filler such as cement-based solidification material by mechanical stirring at the part facing the side of the underground structure. There is also known a method of forming row piles and using the soil cement column piles as earth retaining walls. In these construction methods, multiple ready-made piles were driven as support piles for underground structures to reach the support layer below the soft ground, and the earth pressure from the side was supported by steel sheet piles and column piles. In this state, a portion surrounded by steel sheet piles or column piles is excavated to a predetermined depth to perform root cutting, and an underground structure is constructed on the ready-made pile in this portion.

[0003]

However, the former method of constructing a retaining pile using steel sheet piles and cutting beams and a supporting pile using ready-made piles has the following problems. Generates vibration and noise when driving steel sheet pile. Cut beams passed between steel sheet piles reduce the efficiency of underground construction work. When the steel sheet pile is pulled out, the steel sheet pile removes the surrounding earth and sand and loosens the ground. Due to steel sheet piles and ready-made piles, the bottom of the excavation cannot be reliably improved over the entire surface with an inexpensive construction method such as a soil cement column. Therefore, there is no water blocking that blocks groundwater during root cutting. Due to the lack of water barrier, drainage is always required during excavation work, and the buoyancy of the water may cause damage to the underground structure after construction is completed.
If a road that crosses over an underground structure is used and the ground of the road sinks due to traffic load, etc., the underground structure supported by the support pile does not sink, so the upper part of the road A step occurs at the boundary with the adjacent part, causing vibration and noise when the vehicle passes. Also, the latter method of constructing the earth retaining with the soil cement column pile and the supporting pile with the ready-made pile still has the above-mentioned problems due to the existence of the ready-made pile. In particular, as shown in FIG. 9, when the prefabricated pile 1 is driven and the soil cement column pile 2 is constructed by this method, at the same time, a portion corresponding to the bottom of the underground structure is preceded by an underground beam. An attempt was made to improve the bottom by constructing the soil cement column 3, but the soil cement column 3 could not be constructed close to the ready pile 1 due to the presence of the ready pile 1. Therefore, the excavation bottom surface could not be improved over the entire surface, and water was discharged from the unimproved portion 4 (hatched portion), and a complete water shielding effect could not be obtained. In addition, the part shown with the code | symbol 5 enclosed with the dashed-two dotted line is a part in which an underground structure is constructed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a soft ground which can be constructed at a low cost with a relatively short construction period, prevents flooding during construction of an excavated portion for constructing an underground structure, and prevents the underground structure from floating after construction. The present invention provides a structure around an underground structure and a construction method therefor. Another object of the present invention is to provide a method of using a road crossing over an underground structure such as a drainage channel, an irrigation canal, and a culvert provided on soft ground. It is an object of the present invention to provide a structure around an underground structure in a soft ground that does not cause a step at a boundary with an adjacent part, and a construction method thereof.

[0005]

The invention according to claim 1 is
As shown in FIG. 1 and FIG. 2 , an earth retaining portion 12 provided in the soft ground 10 of the road foundation or a portion facing the side of the underground structure 11 on the soft ground, and in the soft ground 10 or the soft ground A bottom portion 13 provided on a portion of the ground facing the bottom portion of the underground structure 11, and a lower end fixed to the support layer 14 below the soft ground 10 or an upper end located above the support layer and having an upper end Support pile 1 provided to be located at
6 and the soft ground 10 on the back side of the earth retaining portion 12.
The earth retaining portion 12, the bottom plate portion 13, and the support pile portion 16 are each composed of a plurality of first soil cement columns 21, and the first soil cement columns 21 have outer peripheral portions thereof. It is integrated by superimposing on the front, back, left and right in a planar shape, and the back part 17 is
Multiple lengths that are not reached and are provided with an improvement rate of 10-50%
Several second soil cement columns 22 and these second soils
From the shallow layer improvement body 23 formed on the cement column 22
It is a structure around an underground structure in soft ground characterized by becoming . As shown in FIG. 2 , since the soil retaining portion 12, the bottom portion 13, and the support pile portion 16 are integrated with the soil cement columns 21, respectively, a highly rigid and strong structural body can be obtained. In addition, the earth retaining section 12, the bottom section 13, and the supporting pile section 16 are constituted by a plurality of first soil cement columns 21 which are integrated by superposing the outer peripheral portions in a plane shape in front, rear, right and left directions, respectively, thereby forming an underground structure. The ground improvement rate facing the bottom of the base 11 is about 80% or more, and groundwater from below the base 13 is shielded. As a result, flooding during construction is prevented, and damage to floating underground structures after construction can be prevented. In addition, soil retaining part 12 and bottom part 13
Is formed by a plurality of first soil cement columns 21 which are integrated by superimposing the outer peripheral portion in front and rear and right and left in a plane shape, so that the bottom portion 13 acts as an underground beam, and The earth retaining part 12 supports the working side earth pressure.
The number of rows of the soil cement columns 21 can be reduced. The figure
In FIG. 2 , a hatched portion indicates the support pile 16. The support pile 16 may not be constructed in the form of a single soil cement column as shown in FIG. 2 but may be constructed in the form of a soil cement column or a block (not shown).

[0006] Further, in this structure, by constructing the back portion 17 as shown in FIG. 1, when the road is used, a step is formed at the boundary between the portion above the underground structure of the road and the portion adjacent thereto. Does not occur, or if it does occur, it is only slight.
Further, the earth pressure from the back side of the earth retaining portion 12 can be further reduced, and the number of rows of the soil cement columns 21 of the earth retaining portion 12 can be further reduced.

[0007] The invention according to claim 2 is the invention according to claim 1, such that the second soil cement pillar 22 of the plurality of, as shown in FIG. 1 becomes progressively shorter as the distance from the braced section 12 It is a construct provided. In order to eliminate the step, the length of the soil cement column 22 that has moved away from the earth retaining portion 12 may be short, in order to avoid excessive ground improvement.

[0008] The invention according to claim 3 is the invention according to claim 1 or 2 , wherein the lower end of the earth retaining portion 12 extends below the lower end of the bottom portion 13 as shown in FIG. It is. By increasing the length of the first soil cement column 21 constituting the earth retaining portion 12, heaving during root cutting is suppressed. When the back portion 17 is provided, the number of the second soil cement columns 22 can be reduced by providing the first soil cement columns 21 with the function of the second soil cement columns 22 constituting the back portion 17. .

As shown in FIG. 1, the invention according to claim 4 includes a soil retaining portion 12 provided in a soft ground 10 of a road foundation or a portion facing a side portion of an underground structure 11 on the soft ground. A bottom portion 13 provided in a portion facing the bottom portion of the underground structure 11 in the soft ground 10 or on the soft ground,
A support pile 16 having a lower end fixed to the support layer 14 below the soft ground 10 or positioned above the support layer and an upper end positioned at the bottom 13,
This is a construction method for constructing a back portion 17 provided on the soft ground 10 on the surface side , wherein the earth retaining portion 12, the bottom portion 13, and the support pile portion 16 are respectively formed by a plurality of first soil cement columns 21, and A plurality of the first soil cement columns 21 are integrated by superposing the outer peripheral portions of these first soil cement columns 21 in front, rear, left and right in a planar shape, and furthermore,
10 to 50% of the length of the surface portion 17 not reaching the support layer 14
Formed by a plurality of second soil cement columns 22 at an improvement rate of
On the second soil cement columns 22
Ru construction method der of underground structures around the construct in soft ground, which comprises construct a Yotai 23.

In this construction method, the earth retaining section 12, the bottom section 13, and the support pile section 16 are each constructed of the same soil cement column 21, and the back section 17 is also formed of the same type of soil cement column 2.
2, the soil cement pillars can be superimposed on each other in front, rear, left and right, and can be constructed in a relatively short construction period and at low cost.

[0011] The invention according to claim 5 is the invention according to claim 4, such that the second soil cement pillar 22 of the plurality of, as shown in FIG. 1 becomes progressively shorter as the distance from the braced section 12 This is the construction method to be provided. In order to eliminate the step, the length of the soil cement column 22 is gradually reduced as the distance from the earth retaining portion 12 increases.

According to a sixth aspect of the present invention, there is provided the construction method according to the fourth or fifth aspect , wherein the lower end of the earth retaining portion 12 extends below the lower end of the bottom portion 13 as shown in FIG. It is. By increasing the length of the first soil cement pillar 21 constituting the earth retaining portion 12, heaving during root cutting is suppressed. When the back part 17 is provided,
The second part forming the back part 17 on the first soil cement column 21
By having the function of the soil cement column 22, the number of the second soil cement columns 22 can be reduced.

The invention according to claim 7 is the invention according to claims 4 to 6
The invention according to any of the above, wherein the first soil cement pillar 2
This is a construction method in which the diameters of the first and second soil cement columns 22 are the same. First and second soil cement columns 21 and 2
By making 2 the same diameter, the soil cement column can be constructed with the same apparatus, and can be constructed more inexpensively with a shorter construction period.

In the first and fourth aspects of the present invention, "in the soft ground or on the soft ground" means that the earth retaining portion 12 or the earth retaining portion 12 and the bottom portion 13 are connected to the soft ground and the ground thereon. Including the case where it is built over both grounds.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first embodiment of the present invention,
As shown in FIG. 1, a soil retaining section 12, a bottom section 13, a support pile section 16, and a back section 17 are respectively constructed in a soft ground 10 by soil cement columns 21. The soil cement column 21 is construction by mechanical stirrer 30 shown in FIG. First, as shown in FIG. 4 (a), after the tip of the rod 31 of the mechanical stirring device 30 is aligned with the core of the soil cement column to be worked, the rod 31 is rotated, and as shown in FIG. Excavation to a predetermined digging depth. Next, a cement-based solidifying material liquid as a filler is injected from the tip of the rod 31, and the excavation is performed while rotating the blades 32, 33 and 34. Thereby, the filler and the excavated soil are mixed and stirred. As shown in FIG. 4C , the injection is stopped when a predetermined depth is reached, the rod 31 is reversed, and the rod 31 is pulled up to the ground while further mixing and stirring the filler and the excavated soil. By solidifying the filler, the soil cement column 21 shown in FIG. 4D is constructed. This soil cement column 21 has a diameter of about 80-100 cm,
Larger diameters can be used if the placement efficiency is good.

Note that in FIG. 4 , one rod 31
Although the example in which the soil cement columns 21 are constructed has been described, when a plurality of rows of the soil cement columns are constructed, a plurality of rows of the soil cement columns can be drilled at one time using a mechanical stirring device having a plurality of rods. If columns are constructed at the same time, construction can be performed more efficiently. As shown in FIG. 3 , when the soil cement column 21 is constructed so that the outer peripheral portion thereof is superimposed on the front, rear, left and right in a planar shape, a portion 36 surrounded by a two-dot chain line is formed.
The area occupied by the soil cement columns 21 is about 80% or more of the area. For reference, when the soil cement pillar is brought into contact with the soil cement pillar at the outer periphery thereof without being polymerized, the content is about 78.5%. That is, the area of the portion 37 (hatched portion) where the soil cement pillar 21 is not constructed is less than 20% of the area of the portion 36. In the present invention, even if the above-mentioned portion 37 is present, groundwater from soft ground can be completely shut off. This is thought to be because the solidified material column liquid penetrates from the construction part and blocks water when the surrounding soil cement column is constructed.

[0017] Next will be described on the basis of the earth retaining portion 12 and the Sokoban portion 13 and the supporting pile 16 to build method of the back portion 17 in FIGS. In this embodiment, as shown in FIG.
The earth retaining part 12, the bottom part 13 and the support pile part 16 are
Each is constructed by soil cement pillars 21 and the back 1
7 is constructed by soil cement columns 22. (a) Earth retaining part Earth retaining parts 12 are constructed on both sides of the part where the underground structure 11 is constructed. In this embodiment, the underground structure 11 of the irrigation canal is constructed orthogonal to the road direction (see FIG. 2 ). It is standard that each soil retaining portion 12 is constructed by constructing two or more rows of the soil cement column 21 so that the outer peripheral portion of the soil cement column 21 is superimposed on front and rear and left and right with each other, but when the root cutting depth is small. In some cases, one row may be sufficient.

(B) Bottom part While the soil cement column 21 of the bottom part 13 continuous with the earth retaining part 12 is superimposed on the soil cement pillar 21 of the earth retaining part 12, the soil cement pillar 2 constituting the bottom part 13 is also formed.
1 is constructed by constructing a plurality of rows of the bottom portion 13 so that there is no gap in the soft ground between the soil retaining portions 12 and 12 while the outer peripheral portions thereof are superposed on each other in a front-rear and left-right manner in a planar shape. Since the bottom 13 is entirely improved in this way, it is not necessary to divide the foundation of the underground structure. After excavating the root cutting depth as an empty digging depth without filling material, constructing the bottom part 13 by digging to a depth of about 1 to 2 m and constructing the soil cement column 21 while injecting the filling material I do. The soil cement column 21 may have a construction length of 2 m or more depending on the ground conditions and the root cutting depth.

(C) Support pile 16 The support pile 16 is constructed by constructing the soil cement column 21 while superimposing the soil cement column 21 of the bottom 12 when the bottom 13 is constructed. Is done. The support pile portion 16 is dug by the depth of the root cutting like the bottom plate portion 13, and then excavates while injecting a filler until it reaches the support layer 14. The support pile 16 and the bottom 1
With 3, the soft ground between the earth retaining portions 12, 12 is filled with the soil cement columns 21. The support layer 14 is a solid ground unlike the soft ground, and the support pile 16 supports the load of the underground structure 11 via the support layer 14 and prevents the subsidence thereof. The lower end of the supporting pile 16 when the load of the underground construction is small Ru More case be located above the support layer 14.

[0020] FIG. 1 for the construction method of the back surface portion 17 to the next,
A description will be given based on FIGS.

(D) Back section The back section 17 includes the earth retaining section 12, the bottom section 13, and the support pile section 16.
Is performed at the same time as the construction of the second soil cement column 22, and is composed of a plurality of second soil cement columns 22 and a shallow layer improved body 23 formed thereon.
For this reason, it is preferable that the second soil cement column 22 is constructed to have the same diameter as the first soil cement column 21 using the same mechanical stirring device. The second soil cement pillar 22
It is constructed by the method shown in FIG.
Is provided at an improvement rate of 10 to 50% so that the length of the wire does not reach the support layer 14 and gradually decreases as the distance from the retaining portion 12 increases. Soil cement column 22 and shallow layer improved body 2
When the rear part 17 is constructed by combining the four, the value L, which is the sum of the length of the longest soil cement column 22, the thickness of the shallow layer improvement body 24, and the thickness of the road pavement 26 described later, is the traffic load, that is, This is a great condition for suppressing consolidation settlement due to dynamic load. When the improvement rate of the columnar body is set in the range of 10 to 50% and the value L is set to 4 m or more, the consolidation settlement due to the dynamic load can be substantially eliminated.

The plurality of soil cement columns 22 continuously settle the amount of settlement between a road portion above an underground structure that does not sink after the underground structure is built and a road portion adjacent to the underground structure where settlement is expected. It is constructed as a sink control column for For this purpose, as shown in FIG. 1 , a long soil cement column 22 is constructed in the vicinity of the earth retaining portion 12, and a shorter soil cement column 22 is gradually constructed as the distance from the earth retaining portion 12 increases. No cement columns will be constructed. These soil cement columns 22 can prevent lateral flow of the soft ground surrounded by them.

Soil cement column 22 as viewed from above
Will be described with reference to FIGS. 5 and 6 . In consideration of the efficiency and economy of the construction, the planar arrangement of the soil cement columns 22 is a lattice arrangement as shown in FIG. 5 or a non-contact staggered arrangement as shown in FIG. It is preferred to keep it as low as possible. 10-5 improvement rate
In the case of the grid arrangement shown in FIG. 5 in the range of 0%, the grid interval d ₁ (however, the grid interval d ₁ ≧ the grid interval d ₂ )
Is less than twice the height from the top of the soil cement column to the road pavement surface, and also when the improvement rate is in the range of 10 to 50% and the non-contact staggered arrangement shown in FIG. When the direction of the road is D, the soil cement column spacing d ₃ (where soil cement column spacing d ₃ ≧ soil cement column spacing d ₄ ) is 2 of the height from the upper end of the soil cement column to the road pavement surface. If it is less than twice, static load,
The dynamic load is reliably transmitted to the soil cement column, and the lateral flow of the ground can be sufficiently prevented.

Here, the improvement rate of the soil cement column is
As shown in FIG. 5 and FIG. 6 , the percentage of the cross-sectional area of the soil cement column in the unit area of the improved ground when the soil cement column is viewed from above. If the improvement rate of the soil cement column is less than 10%, consolidation settlement cannot be sufficiently suppressed, and if it exceeds 50%, there is a problem that the construction period and construction cost are rather increased. Preferably, this improvement is 15-30%
It is. Although the value L is required to be 4 m or more, the effect of suppressing the dynamic consolidation settlement does not increase so much even if it is increased.
However, the greater the value L, the greater the effect of suppressing static consolidation settlement. In the present invention, in order to avoid excessive ground improvement, the lower end of the soil cement column does not reach the support layer 14 below the soft ground 10, as shown in FIG . The maximum value of the value L is appropriately determined in consideration of the thickness of the soft ground, the degree of softness thereof, the load condition, economy, and the like.

[0025] The shallow layer improved body 23 is a soil cement column 22.
It is built on the upper part of the subsidence control column group consisting of, and it is expected that the road section and the subsidence on the underground structure that does not subside after the underground structure is constructed after being integrated with the subsidence control column group It has the function of making the amount of settlement between the road section and the road section continuous. The shallow layer improved body 23 is formed by uniformly mixing and solidifying earth and sand and a solidified material such as powdered or slurry-like cement, cement-based solidifying material, quicklime, and the like. After the earth retaining part 12, the bottom part 13, and the support pile part 16 are constructed, and subsequently the back part 17 is constructed, the earth and sand above the bottom part 13 and the support pile part 16 are excavated to perform root cutting. After this Excavation to build an underground construction 11 to Excavation portion further performs road pavement 26 on the underground structures 11 and earth retaining portion 12 and the shallow improved body 26. Above the underground structure 11
When it becomes a road, the earth retaining part 12 and the underground structure 11
The road pavement 26 is performed thereon. Road pavement 26 is from lower to upper
To the crusher run layer, the crushed stone layer, and
It is laid in the order of sphalt concrete. This implementation
In the form, the crusher run layer has a thickness of 5 to 15 cm.
In addition, the size-adjusted crushed stone layer has a thickness of 10 to 30 cm.
Sphalt concrete is 10 to 40 cm thick.
Each is laid. In this construction method, by constructing the back part 17, the earth pressure acting on the earth retaining part 12 at the time of root cutting can be reduced.

Next, a second embodiment of the present invention will be described. As shown in FIG. 7 , in this embodiment, a soil retaining part 12, a bottom part 13 and a supporting pile part 16 are respectively provided on a soft ground 10 as in the first embodiment.
, And the back part 17 is constructed by the soil cement pillar 22. In this embodiment, the support pile portion 16 is located above the support layer 14 without being fixed to the support layer 14, and the lower ends of the plurality of first soil cement columns 21 constituting the earth retaining portion 12 are located at the bottom portion. A plurality of second soil cement columns 22 are provided so as to extend below the lower end of 13 and have the same length. The support pile 16 functions as a friction pile and supports the underground structure 11. Further, by increasing the length of the first soil cement column 21 constituting the earth retaining portion 12, heaving during root cutting is suppressed.
That is, the earth mass on the back side of the earth retaining portion does not cause plastic flow and goes around the tip of the soil cement column, so that the excavated bottom does not rise. At the same time, by providing the function of the second soil cement columns 22 constituting the back surface portion 17, the number of the second soil cement columns 22 can be reduced.

[0027]

[0028]

[0029]

[0030]

As described above, the construct of the present invention comprises:
Rather than using conventional off-the-shelf piles for the support piles, the support piles were integrally constructed with the same soil cement columns for both the earth retaining section and the bottom section to support the underground structure. It can be built inexpensively with a short construction period, and the bottom can be built with an improvement rate of about 80% or more. As a result, the soil retaining column and the soil cement column that constitutes the bottom part also polymerize,
It is possible to prevent flooding during construction of an excavated portion for constructing an underground structure, and prevent damage such as floating of the underground structure after construction. Also, since conventional steel sheet piles are not used, there are no cut beams between steel sheet piles, construction work of underground structures can be performed efficiently, vibration and noise when driving steel sheet piles are eliminated, and steel sheet piles are further eliminated. There is no ground subsidence like when removing the ground. Furthermore, since the bottom can be entirely improved, there is also an advantage that it is not necessary to divide the foundation of the underground structure. Further, according to the structure having a rear portion of the present invention, when a road that crosses over an underground structure such as a drainage channel, an irrigation channel, and a culvert, which is provided on soft ground, is used adjacent to the underground structure. Consolidation settlement due to the dynamic load of the road part is suppressed, and there is no step at the boundary between the part above the underground structure of the road and the adjacent part, and vibration and noise are generated when the vehicle passes Does not occur. Further, by constructing the back portion, there is an advantage that the earth pressure acting on the earth retaining portion at the time of root cutting can be reduced, whereby the number of rows of soil cement columns constituting the earth retaining portion can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a building according to a first embodiment of the present invention when viewed from a direction orthogonal to a road direction.

FIG. 2 is a cross-sectional view of a retaining part, a bottom part, and a support pile part of FIG.

FIG. 3 is an enlarged sectional view of a main part of FIG . 2 ;

4 (a) to 4 (d) are views showing a construction procedure of a soil cement column.

FIG. 5 is a plan view when a plurality of second soil cement pillars constituting a back surface portion are arranged in a lattice shape.

FIG. 6 is a plan view when a plurality of second soil cement pillars constituting the back surface are arranged in a non-contact staggered manner.

FIG. 7 is a cross-sectional view of a building according to a second embodiment of the present invention as viewed from a direction orthogonal to a road direction.

FIG. 8 is a cross-sectional view corresponding to FIG. 2 of a conventional trial construction.

────────────────────────────────────────────────── ─── Continued on the front page (73) Patent holder 000006264 Mitsubishi Materials Corporation 1-5-1, Otemachi, Chiyoda-ku, Tokyo (72) Inventor Tetsuhiko Miura 12-4, Tatemachi, Naka, Saga City, Saga Prefecture ( 72) Inventor Kazuyuki Fujikawa 3-1-2 Ikebukuro, Toshima-ku, Tokyo Inside Dia Consultant Co., Ltd. (72) Inventor Kosei Fukuda 6-13-7 Akasaka, Minato-ku, Tokyo Tenox Corporation (72) Invention Person Yoji Ueyama 4-1-1, Tenjin, Chuo-ku, Fukuoka City, Fukuoka Prefecture Tenox Kyushu Co., Ltd. (72) Inventor Akira Hamatake 2-4-4 Sotokanda, Chiyoda-ku, Tokyo Inside Tokyo Hoso Kogyo Co., Ltd. (72) Inventor Isao Kobayashi Mitsubishi Materials Co., Ltd., 1-5-1, Otemachi, Chiyoda-ku, Tokyo (56) Reference JP-A-7-305337 (JP, A) JP-A-4-323413 (JP, A) JP-A-5-59719 (JP, A) JP-A-6-257169 (JP, A) JP-A-6-41951 (JP, A) JP-A-8-74245 ( JP, A) JP-A-5-59717 (JP, A) JP-A-10-317307 (JP, A) JP-B-50-14803 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , (DB name) E02D 3/12 E02D 31/00-31/14

Claims (7)

(57) [Claims] An earth retaining portion (12) provided in a portion of a road foundation facing a side of an underground structure (11) in or on the soft ground of the road foundation, and the soft ground (10) Underground structure (1 in the middle or on the soft ground
A bottom portion (13) provided at a portion facing the bottom portion of 1), and a lower end is fixed to the support layer (14) below the soft ground (10) or an upper end is located above the support layer and the upper end is Bottom part (13)
The support pile portion (16) provided so as to be located at, and a back portion (17) provided on the soft ground (10) on the back side of the earth retaining portion (12), the earth retaining portion ( 12), the bottom part (13), and the support pile part (16)
Are each composed of a plurality of first soil cement columns (21), and the plurality of first soil cement columns (21) are integrated by superimposing their outer peripheral portions in a front-rear, front-rear, left-right direction with one another, The back portion (17) has a length not reaching the support layer (14).
A plurality of second soil cement columns (22) provided at an improvement rate of 0 to 50% and the plurality of second soil cement columns (22);
And a shallow layer improvement body (23) formed on the ground. 2. A plurality of second soil cement pillars (22) construct of claim 1, wherein provided so as progressively shorter as the distance from the braced section (12). 3. Retaining portion (12) construct a lower end bottom panel section (13) lower than the claim 1 or 2 wherein is provided extending downward of the. An earth retaining portion (12) provided in a portion of the road foundation that faces the side of the underground structure (11) in or on the soft ground of the road foundation, and the soft ground (10). A bottom portion (13) provided to be located at a portion facing the bottom of the underground structure (11) in or on the soft ground, and a lower end of the soft ground (10)
A support pile (16) which is fixed to the support layer (14) below or is provided above the support layer and the upper end is located at the bottom part (13), and the earth retaining part (12 A method of constructing a back part (17) provided on the soft ground (10) on the back side of the soil retaining part (12), the bottom part (13), and the support pile part (16).
Are formed by a plurality of first soil cement columns (21), respectively, and the outer peripheral portions of the plurality of first soil cement columns (21) are superimposed one on the other in a front-rear and left-right direction in a planar shape to thereby form the plurality of first soil cement columns (21). One soil cement pillar (21) is integrated, and a plurality of second soil cement pillars (22) are provided with the back portion (17) having a length not reaching the support layer (14) at an improvement rate of 10 to 50%. And constructing by constructing a shallow layer improved body (23) on the plurality of second soil cement pillars (22). Construction method. 5. The construction method according to claim 4 , wherein the plurality of second soil cement pillars (22) are provided so as to be gradually shortened as the distance from the earth retaining portion (12) increases. 6. The construction method according to claim 4, wherein a lower end of the earth retaining portion (12) is provided to extend below a lower end of the bottom portion (13). 7. Construction method of the first soil cement pillar (21) and claims 4 to 6, wherein either the diameter of the second soil cement pillar (22) are identical.