JP2021031985A - Soil improvement body, and construction method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground improvement body capable of further shortening the construction period while maintaining the strength of the ground improvement body while coping with a phenomenon when the ground improvement body is adjacent to a rigid body. SOLUTION: A first level L1 to a fourth level L4 are set in this order from the deepest side in the ground 10 to be improved, and the first level L1 is made variable. The improved body includes a short column 11 group formed by a column construction machine 30 that reaches from the first level L1 to the second level L2 and rotates in a horizontal plane, and a slab body 20 supported by the short column 11 group. To be equipped. The slab body 20 is formed by a vertical slab construction machine 40, and has a slab main body 21 from the third level L3 to the fourth level L4 and a beam from the second level L2 to the third level L3 directly under the slab main body 21. The unit 22 is provided. The slab body 20 has a T-shape in a vertical cross-sectional view, and the first level L1 is set shallower as it goes deepest in the vicinity of the rigid body X and away from the rigid body X. [Selection diagram] Fig. 5

Description

The present invention relates to a ground improvement body and a method for constructing the same, for constructing a road, a railway, or the like by embankment on the ground to be improved.

The applicants have already proposed and put into practical use a technique suitable for such a purpose and capable of shortening the construction period (see Patent Document 1: Japanese Patent No. 3528950).

Hereinafter, a method of constructing a conventional ground improvement body will be described with reference to FIGS. 20 to 21. FIG. 20 is a vertical sectional view showing a ground improvement body by a conventional construction method, and FIG. 21 is a horizontal sectional view thereof.

Eventually, the embankment 3 (which may include pavement) is applied on the constructed ground improvement body, and the vehicle 4 runs on it. As a result, the eccentric load of the vehicle 4 dynamically acts on the ground improvement body.

Focusing only on the area below the embankment 3, the following levels are set in order from the deepest underground of the ground 10 to be improved. The column bottom level LA is the lowest level of column 1 constructed by a column construction machine equipped with an auger motor. The column top level LB is the highest level of the column 1 and the lowest level of the slab 2. The slab top level LC is the highest level of the slab 2 and the level in contact with the bottom of the embankment 3.

As shown in FIG. 21, the improvement rate by column 1 (the density of column 1, for example, 14.5%, etc.) is determined in consideration of the properties of the ground 10 to be improved.

The construction method is as follows. First, using a column construction machine, a group of columns from the column bottom level LA to the column top level LB is formed. Next, a slab 2 from the column top level LB to the slab top level LC is formed by using a heavy machine such as a backhoe.

As described above, each column 1 is formed from the bottom portion 1a to the top portion 1b thereof, and abuts on the bottom surface of the slab 2 to support the slab 2. Here, in the present specification, the column 1 in which the top portion 1b abuts on the bottom surface of the slab 2 is referred to as a "normal column".

Here, as described in Patent Document 5 (Japanese Patent No. 31077774), not only is the ground improvement body constructed on the ground 10 to be improved, but also when the rigid body X is adjacent to the ground improvement body, the following Further ingenuity is required as described.

The "rigid body" here is an object that shows strong resistance to subsidence, for example, a bridge, a culvert, a building foundation (including the case where the lower part is supported by a column or the like), a bedrock, or the like. And these are considered to be non-sinkable by design.

If the ground improvement body is constructed without any consideration, the rigid body does not sink, whereas the ground improvement body sinks to some extent, so that a significant step is generated at the boundary 50 between the rigid body and the ground improvement body. This is extremely inconvenient because it results in damage to the interests of a third party, such as severe vertical movement of the traveling vehicle and damage to the bottom of the vehicle.

In order to avoid such a situation, as shown in FIG. 20, it is desirable to set the depth of the column to be maximum in the vicinity of the rigid body X and decrease as the distance from the rigid body X increases.

As described above, by combining Patent Document 1 and Patent Document 5, it is expected that the construction period can be shortened to a certain extent while coping with the phenomenon when the ground improvement body is adjacent to the rigid body.

However, the present inventors have completed the present invention by devising the structure of the slab by diligently studying whether or not the construction period can be further shortened.
Japanese Patent No. 3528950 Japanese Patent No. 4038525 Japanese Patent No. 3432802 Japanese Patent No. 45004095 Japanese Patent No. 31077774

That is, the present invention provides a ground improvement body and related technology capable of further shortening the construction period while maintaining the strength of the ground improvement body while coping with the phenomenon when the ground improvement body is adjacent to the rigid body. With the goal.

The ground improvement body according to the first invention is a ground improvement body adjacent to a rigid body, and the first level, the second level, the third level, and the first level, the second level, the third level, and the ground improvement body from the deep side to the shallow side in the ground to be improved. The four levels are set in this order, the first level is variable, and a group of short columns and columns formed by a column construction machine that reaches from the first level to the second level and rotates in a horizontal plane. A slab body supported by a group of short columns is provided, and the slab body is a slab body formed by a vertical slab construction machine that reaches the third to fourth levels and rotates in the vertical direction, and the slab body. Immediately below, from the second level to the third level, the slab body is formed by a vertical slab construction machine and is provided with a beam portion connected to the top of a group of short cylindrical columns, and the slab body is T in a vertical cross-sectional view. It is cylindrical and the first level is set deepest in the vicinity of the rigid body and shallower as it moves away from the rigid body.

The "rigid body" here is a bridge, culvert, building foundation, rock mass, etc. that does not subside, and is not allowed to subside by design, but when the bottom of the rigid body is supported by a column or the like. And both cases where it is not supported are included.

Since the first level is set deepest in the vicinity of the rigid body and shallower as the distance from the rigid body increases, the subsidence of the ground improvement body in the vicinity of the rigid body is significantly suppressed, and at the boundary between the rigid body and the ground improvement body. The step can be effectively reduced. Therefore, the vehicle can smoothly travel from the ground improvement body to the rigid body, or vice versa.

Here, the columnar short columns may be arranged in a grid pattern in a plan view, or may be arranged in a staggered pattern in a plan view.

In addition, an embankment (including pavement) is usually laid on the upper part of the slab body.

Further, a plurality of normal column groups from the first level to the third level, the top of which supports the slab body, may be further provided.

Here, the slab body has a beam portion connected to the top of the columnar short column group to form a T shape in a vertical cross-sectional view, so that a load from above by a vehicle or the like acts on the ground improvement body. However, this load is dispersed, the acting stress on the ground to be improved existing between the beams is reduced, and uneven subsidence is suppressed.

Further, the bending tensile stress between the beam portions can be reduced, and the column improvement rate can be reduced.

The traffic direction of the vehicle may be one that crosses the ground improvement body or one that traverses the ground improvement body. In other words, the width direction and the length direction of the ground improvement body may be changed as appropriate.

As will be described in detail below, according to the present invention, smooth vehicle running is possible by significantly suppressing the step at the boundary between the rigid body and the ground improvement body. Moreover, the improved volume is almost the same as that of the conventional technique, and the construction period can be reduced by about 20%.

Moreover, this point is possible while maintaining the strength of the ground improvement body, and has a high practical effect such as leading to a significant reduction in the overall construction cost.

(Embodiment 1)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing a ground improvement body according to the first embodiment of the present invention, and FIG. 2 is a horizontal sectional view thereof.

First, in the ground improvement body according to the present embodiment, as shown in FIG. 1, the first level L1, the second level L2, the third level L3, and the first level L3 and the third level L3 are directed from the deep side to the shallow side in the ground 10 to be improved. The 4th level L4 is set in this order.

The first level L1 is variable and is the deepest (maximum) (L1 (1)) in the vicinity of the rigid body X and the shallowest (minimum) (L1 (7)) at the farthest point. Normally, the first level L1 is set to be shallow in proportion to the distance from the rigid body X. However, even if the relationship is not proportional, if the increase / decrease relationship is the same, for example, by logarithm, quadratic function, etc., it can be used without any problem, and thus it is also included in the protection scope of the present invention.

The first level L1 is the lowest level of the short column 11 constructed by the column construction machine 30 (see FIG. 3) equipped with an auger motor. If the grounding method is adopted, the first level L1 can be set to the level of the bottom to be touched or lower, and if the floating method is adopted, it can be set to the level floating above the bottom. .. Please refer to the previous paragraph for the variability of the first level L1.

The second level L2 is the highest level of the short column 11 and the lowest level of the beam portion 22 of the slab body 20.

The third level L3 is the highest level of the beam portion 22 of the slab body 20, the lowest level of the slab body 21 of the slab body 20, and also the highest level of the normal column 1 (see FIG. 20).

The fourth level L4 is the highest level of the slab main body 21 of the slab body 20 and the lowest level of the embankment (not shown).

That is, the slab body 20 includes a slab main body 21 having a horizontal equal thickness, and a plurality of beam portions 22 extending downward from the slab main body 21 and continuously provided so as to be in contact with the top portion 11b of the short column 11. The slab body 20 is a continuous body having a T shape in a vertical cross-sectional view. If the two beam portions 22 are taken out, it can be said that the slab body 20 has a π-shape.

In a plan view, as shown in FIG. 2, a plurality of short column 11 groups are located directly under each of the plurality of beam portions 22.

Here, for convenience of explanation, the horizontal dimension B in FIG. 2 is referred to as the road length, and the vertical dimension A is referred to as the improved width. As described above, the vehicle 4 (see FIG. 20) is composed of the slab body 20. It must be understood that the T-shaped structure may be crossed or traversed, and the length and width can be interchanged.

As described above, after setting the level etc. in advance, the actual construction will be started.

First, as shown in FIGS. 3 and 4, a plurality of short column 11 groups are constructed from the first level L1 (1) to L1 (6) to the second level L2 by using the column construction machine 30. .. At this time, the column construction machine 30 is usually attached to a base machine 31, a leader 32 that stands vertically, a rotation shaft 33 that is supported so as to be able to rotate horizontally with respect to the leader 32, and a tip portion of the rotation shaft 33. It includes a head portion 34 to be attached. The change of the first level L1 can be easily realized by appropriately changing the target depth in the column construction machine 30.

The head portion 34 stirs a predetermined portion of the soil 10 and discharges and mixes cement milk to construct a group of short columns 11 made of soil cement. Incidentally, the head portion 34 has an auger and preferably includes a screw and a co-rotation prevention blade, but the screw and the co-rotation prevention blade may be omitted.

As shown by hatching in FIG. 4, even when all the short column 11 groups are constructed, the space for the slab body 20 composed of the slab body 21 and the beam portion 22 is hollow or soil. It is arbitrary whether it is filled with, but the short column 11 group is not constructed up to this space.

Next, the construction of the slab body 20 is started. As shown in FIGS. 5 to 8, in this embodiment, the slab main body 21 from the third level L3 to the fourth level L4 and the second level are used by using the vertical slab construction machine 40 in consideration of work efficiency. The slab body 20 including the beam portion 22 from L2 to the third level L3 is collectively constructed. However, it is also possible to construct only the beam portion 22 first and then construct the slab main body 21.

The vertical slab construction machine 40 has an operating portion 42 that rotates in the vertical direction to excavate, discharge cement milk, and agitate, and a main body 41 that applies a driving force to the operating portion 42. It is arbitrary as long as the depth reached by 42 can be controlled. For example, by rotary (see Patent Document 2: Patent No. 4038525), by trencher (see Patent Document 3: Patent No. 3432802), by chain conveyor cutter (see Patent Document 4: Patent No. 4504095). ) May be used.

To form only the slab body 21, the reach depth H3 is set to the third level L3 to the fourth level L4, and to form the slab body 21 and the beam portion 22, the reach depth (H3 + H2) is set to the second level. It may be from L2 to the fourth level L4.

The comparison with the prior art, the first embodiment and the next second embodiment will be described together at the end.

(Embodiment 2)
In the first embodiment, as shown in FIG. 9, the column group is composed of only the short column 11 group. However, in the second embodiment, as shown in FIG. 11, the column 1 group is usually arranged at a place where the beam portion 22 is not formed.

Except for this point, it is the same as that of the first embodiment. As described above, in the normal column 1 in the second embodiment provided in the place where the beam portion 22 is not formed, the bottom portion 1a thereof is located at the first level L1 (1) to L1 (6), and the bottom portion 1a thereof is located. The top 1b is located at the third level L3.

(Comparison of Conventional Technology, Embodiment 1 and Embodiment 2)
FIG. 10 shows an example of the calculation result regarding the slab body in the first embodiment. The bending stress σ obtained by dividing the bending moment M by the section modulus Z is 38 [kN / m ² ], which is less than the reference value (80 [kN / m ² ]) and is safe.

Similarly, FIG. 12 shows an example of the calculation result regarding the slab body in the second embodiment. The bending stress σ obtained by dividing the bending moment M by the section modulus Z is 65 [kN / m ² ], which is less than the reference value (80 [kN / m ² ]) and is safe.

(Table 1) shows the numerical values of the prior art, the first embodiment, and the second embodiment in comparison from the left.

In (Table 1), the ground improvement bodies in any of the prior art, the first embodiment, and the second embodiment have the same strength and external dimensions. On the other hand, in the prior art, the first embodiment, and the second embodiment, the column improvement rates are 14.5, 9.3, and 9.8%, respectively, and the first and second embodiments are the prior art. It can be seen that it has the same strength, albeit at a lower improvement rate.

Further, the total of the improved volumes is almost the same as 96% in the first embodiment and 103% in the second embodiment, assuming that the conventional technique is 100%. Further, the total number of construction days (construction period) can be reduced by about 20%, which is 74% in the first embodiment and 80% in the second embodiment, assuming that the conventional technique is 100%.

From this, it is understood that according to the present invention, while ensuring the same strength as the conventional technique, the improved volume is the same as that of the conventional technique, the construction period can be reduced by about 20%, and the entire construction cost can be significantly suppressed. Will be done. Of course, the numerical values shown in FIGS. 10, 12 and (Table 1) are merely examples, and the present invention is not limited to these numerical values, and the respective numerical values are not limited to these numerical values unless the gist of the present invention is changed. Is included in the scope of protection of the present invention even if various changes are made. In the above, the case where a road or a railroad is laid at the site has been described, but as is obvious to those skilled in the art, the site of the present invention is not limited to this.

Next, various configuration examples of the beam portion 22 and the short column 11 will be described with reference to FIGS. 13 to 15. Needless to say, the following description is merely an example, and as long as it does not deviate from the gist of the present invention, it belongs to the scope of protection of the present invention even if various changes (not shown) are made. In particular, the normal column 1 may be added or changed as needed.

By the way, in the example shown in FIG. 2, the beam portion 22 is arranged in parallel with the improved width A, and the short column 11 is arranged in a grid pattern in contact with the beam portion 22.

Instead of this, as shown in FIG. 13, short columns 22 may be arranged in a staggered manner on the beam portion 22 parallel to the improved width A. Further, as shown in FIG. 14, the beam portion 22 may be arranged in parallel with the road length B.

Here, the short columns 11 may be arranged in a grid pattern as shown in FIG. 14, or may be staggered instead.

Further, as shown in FIG. 15, the beam portions 22 themselves are formed so as to intersect each other vertically and horizontally, the beam portions 22 themselves are formed in a grid pattern, and the short columns 11 are arranged at desired positions of the beam portions 22. You may. In this way, the upper layer portion of the ground is surrounded by the beam portion 22 and is restrained. As a result, steps at the boundary of structures caused by earthquakes, etc. are suppressed, and in areas where ground improvement bodies are being constructed, temporary restoration work for the passage of emergency vehicles is not required, and immediately after a disaster occurs. It is a great profit, such as being able to drive a vehicle.

Next, the phenomenon before and after the settlement will be described with reference to FIGS. 16 to 19.

(1st example)
In this example, as shown in FIG. 16, the rigid body X is located in the center, and a pair of ground improvement bodies are symmetrically constructed on both sides of the rigid body X. In the case of constructing the ground improvement body only on one side of the rigid body X, it is sufficient to pay attention to only one side of the rigid body X in FIGS. 16 and 17.

By the way, in the state where subsidence does not occur, as shown in FIG. 16, the pair of slab bodies 20 and 20 are in a horizontal state, and there is a step at the boundary 50 with the rigid body X or the boundary 51 on the opposite side. Has not occurred.

However, when the vehicle 4 or the like travels and a dynamic load acts on the slab bodies 20 and 20, as shown in FIG. 17, the slab bodies 20 and 20 are higher when they are closer to the rigid body X and lower when they are farther from the rigid body X. , Tilt.

This sets the first level L1 to L1 (1)> L1 (2)> L1 (3)>...> L1 (7).
This is because the resistance to subsidence has the same magnitude relationship.

As a result, it should be noted that the step formed is gentle at both the boundary 50 near the rigid body X and the boundary 51 far from the rigid body X, so that the vehicle 4 and the like can smoothly travel and pass.

(2nd example)
In this example, as shown in FIG. 18, a pair of rigid body groups X and X exist on both sides, and the grounds 10 and 10 between these rigid bodies X and X are improved by a pair of ground improvement body groups. Is.

In this case, the first level L1 (1) on the side close to the rigid bodies X and X is maximized, and the first level L1 (7) in the central portion between the rigid bodies X and X is minimized.

When a dynamic load from the vehicle 4 or the like acts and subsidence occurs, as shown in FIG. 19, a pair of slab bodies are formed so that the vicinity of the rigid body X is high and the distance is low (approximately V-shaped in the central portion). 20 and 20 are tilted.

In this case as well, it should be noted that the step formed is gentle at the boundary 50 near the rigid body X and at the boundary 51 far away, so that the vehicle 4 and the like can smoothly run and pass. ..

A vertical sectional view showing a ground improvement body according to the first embodiment of the present invention. Horizontal sectional view which shows the ground improvement body in Embodiment 1 of this invention A vertical sectional view showing a ground improvement body according to the first embodiment of the present invention. Horizontal sectional view which shows the ground improvement body in Embodiment 1 of this invention A vertical sectional view showing a ground improvement body according to the first embodiment of the present invention. Horizontal sectional view which shows the ground improvement body in Embodiment 1 of this invention A vertical sectional view showing a ground improvement body according to the first embodiment of the present invention. Horizontal sectional view which shows the ground improvement body in Embodiment 1 of this invention Horizontal sectional view which shows the ground improvement body in Embodiment 1 of this invention The figure which shows the cross-sectional property of the slab body in Embodiment 1 of this invention. Horizontal sectional view which shows the ground improvement body in Embodiment 2 of this invention The figure which shows the cross-sectional property of the slab body in Embodiment 2 of this invention. Horizontal sectional view showing a layout in another embodiment of the present invention. Horizontal sectional view showing a layout in another embodiment of the present invention. Horizontal sectional view showing a layout in another embodiment of the present invention. Longitudinal sectional view showing a rigid body and a ground improvement body in the first example (before subsidence) of the present invention. Longitudinal sectional view showing a rigid body and a ground improvement body in the first example (after subsidence) of the present invention. Longitudinal sectional view showing a rigid body and a ground improvement body in the second example (before subsidence) of the present invention. Longitudinal sectional view showing a rigid body and a ground improvement body in the second example (after subsidence) of the present invention. Vertical cross-sectional view showing the ground improvement body by the conventional construction method Horizontal cross-sectional view showing the ground improvement body by the conventional construction method

1 Normal columns 1a, 11a, 22a Bottom 1b, 11b Top 2 Slab 3 Filling 4 Vehicle 10 Ground to be improved 11 Short column 20 Slab body 21 Slab body 22 Beam 30 Column construction machine 31 Base machine 32 Leader 34 Head 40 Vertical Type slab construction machine 41 Main body 42 Acting part 50, 51 Boundary A Improved width B Road length L1 1st level L2 2nd level L3 3rd level L4 4th level LA Column bottom level LB Column top level LC Slab top level H1 Column Long H2 Beam height H3 Slab thickness X Rigid body

Claims (10)

A ground improvement body adjacent to a rigid body,
The first level, the second level, the third level, and the fourth level are set in this order from the deeper side to the shallower side in the ground to be improved, and the first level is made variable.
A plurality of columnar short column groups formed by a column construction machine that reaches from the first level to the second level and rotates in a horizontal plane.
A slab body supported by the columnar short column group is provided.
The slab body
A slab body formed by a vertical slab construction machine that reaches the fourth level from the third level and rotates in the vertical direction, and
Immediately below the slab main body, a beam portion that reaches the third level from the second level, is formed by the vertical slab construction machine, and is continuously provided at the top of the columnar short column group is provided.
The slab body has a T-shape in a vertical cross-sectional view.
The ground improvement body is characterized in that the first level is set deepest in the vicinity of the rigid body and shallower as the distance from the rigid body increases. The ground improvement body according to claim 1, wherein the rigid body is any one of a bridge, a culvert, a building foundation, or a bedrock. The ground improvement body according to claim 1 or 2, wherein the columnar short column group is arranged in a grid pattern in a plan view. The ground improvement body according to claim 1 or 2, wherein the columnar short column group is arranged in a staggered manner in a plan view. The ground improvement body according to any one of claims 1 to 4, wherein an embankment is laid on the upper part of the slab body. The ground improvement body according to any one of claims 1 to 4, further comprising a plurality of normal column groups from the first level to the third level, the top of which supports the slab body. It is a method of constructing a ground improvement body adjacent to a rigid body.
The process of setting the first level, the second level, the third level, and the fourth level in this order from the deeper side to the shallower side in the ground to be improved, and making the first level variable.
A process of providing a plurality of columnar short column groups from the first level to the second level using a column construction machine that rotates in a horizontal plane.
Including a step of providing a slab body supported by the columnar short column group by using a vertical slab construction machine that rotates in the vertical direction.
The slab body
The slab body from the third level to the fourth level,
Immediately below the slab main body, a beam portion that reaches the third level from the second level and is continuously provided at the top of the cylindrical short column group is provided.
The slab body has a T-shape in a vertical cross-sectional view.
A method for constructing a ground improvement body, wherein the first level is set deepest in the vicinity of the rigid body and shallower as the distance from the rigid body increases. The method for constructing a ground improvement body according to claim 7, wherein the rigid body is any one of a bridge, a culvert, a building foundation, and a bedrock. The method for constructing a ground improvement body according to claim 7 or 8, wherein the vertical slab construction machine uses at least one of a rotary, a trencher, and a chain conveyor cutter. The method for constructing a ground improvement body according to claim 7 or 8, further comprising a step of providing a plurality of normal column groups whose tops support the slab body from the first level to the third level.

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