JP2003239276A - Construction method for road - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method for a road which can be inexpensively constructed in a relatively short construction period, suppresses consolidation settlement caused by a dynamic load in the use of the road constructed on soft ground by filling, and prevents a step from being generated in a boundary between an upper part of an underground structure of the road and a part adjacent to the upper part in the use of the road crossing an area above the underground structure such as a covered conduit provided on the soft ground. <P>SOLUTION: A plurality of columnar bodies 20, which are short enough to prevent an arrival at a bearing layer below the soft ground 11, are constructed in the soft ground 11 of a road foundation at an improvement rate of 10-50%, a net-like body 21 for reinforcement is laid on the columnar bodies 20; either or both of an additive material and an additive agent is or are further added to sediment and a solidifying material, and fixed for solidification, so that a shallow-layer improving soil layer 13 can be laid on the net-like body 21; and a road pavement 18 is constructed on the soil layer 13. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a construction method for constructing a road by embankment on soft ground. The present invention also relates to a method of constructing a road crossing over an underground structure such as an underdrain provided on soft ground by embankment.

[0002]

2. Description of the Related Art The following construction method is adopted when constructing a road by embankment on a soft ground having a thick layer of buried soil or alluvium. First, as shown in FIG. 9, the cement-based solidifying material is dry-mixed in the shallow layer portion of the soft ground 1 and then solidified to form the shallow-layer improved soil layer 2a, thereby improving the rigidity of the shallow layer 2 and the improved ground 2. Alternatively, as shown in FIG. 10, quick lime is dry-mixed in the shallow layer portion of the soft ground 1 and then solidified to form a shallow improved soil layer 2b, and Fe lime is further formed on the shallow improved soil layer 2b. Is mixed by dry mixing and then solidified to form a shallow-layer improved soil layer 2c, thereby forming the improved ground 2 having an increased rigidity of the shallow layer. Next, as shown in FIGS. 9 and 10, the improved ground 2 is used as a subgrade, and an embankment composed of a crusher run layer 3a and a crushed stone layer 3b for particle size adjustment is provided on the subgrade to form the subbase 3 and then the subgrade 3 Asphalt concrete layer 4
Has been paved. In this specification, the roadbed and the pavement are not separated but are referred to as road pavement.

Further, as shown in FIG. 11 or FIG. 12, an underground structure 6 such as an underdrain whose settlement is suppressed is provided in the shallow layer portion of the soft ground 1 where the buried soil layer and the alluvial layer are thick When constructing a road crossing the structure 6 by pavement on the soft ground 1 other than the underground structure 6 and the underground structure, first, in the deep portion of the soft ground 1, the lower part of the soft ground is supported. After supporting the underground structure 6 with the support piles 8 that reach the layer 7, in the shallow layer portion of the soft ground 1 other than the underground structure,
After forming the improved ground 2 and the roadbed 3 as in FIG. 9 or 10, the asphalt / concrete layer 4 is provided on the roadbed 3 for paving. At the mounting part of the bridge, the stepping method is used as a measure to prevent a step near the abutment due to the subsidence of the backfill soil layer or the embankment layer of the abutment.

[0004]

A static load due to embankment and a dynamic load due to running of an automobile are applied to the roadbed of the road, and these loads are transmitted to the roadbed. When the embankment thickness is as thin as about 1.0 m, the dynamic load is comparable to the static load and has a property of repeatedly acting for a long period of time. Therefore, if the degree of ground improvement is not sufficient, even if it can sufficiently withstand the consolidation settlement due to static load, it will not be able to withstand several times that dynamic load, and the road will continue to undergo consolidation settlement due to the dynamic load. It will be. On the other hand, if the ground is sufficiently improved, it is possible to suppress consolidation settlement due to dynamic load, but the relationship between the degree of ground improvement and the suppression effect of consolidation settlement due to dynamic load is not fully understood. For this reason, excessive attempts were made to suppress consolidation settlement, resulting in excessive ground improvement and unnecessarily prolonging the construction period, resulting in wasted construction costs.

In the case of constructing by constructing an underground structure and a soft ground other than the underground structure by paving the road,
Since the underground structure is supported by the support piles, it does not sink, and even if it sinks, it is very small. When the static load and the dynamic load described above are applied to the road constructed by traversing the underground structure which hardly causes the subsidence, as shown by the broken line in FIG. 11 or FIG. A step A is formed at the boundary with the adjacent portion, which hinders smooth running of the automobile. Such steps are repeatedly generated even when repaired.

An object of the present invention is to provide a road construction method which can be constructed at a relatively short construction period at low cost and which suppresses consolidation settlement due to dynamic load when a road constructed by embankment on soft ground is used. To provide. Another object of the present invention is a relatively short construction period, which can be constructed inexpensively, and when a road crossing over an underground structure such as an underdrain provided on soft ground is used, the underground structure of the road is used. It is to provide a road construction method that does not cause a step at the boundary between the upper portion and the adjacent portion.

[0007]

The invention according to claim 1 is
As shown in FIG. 1, a plurality of pillars 20 are constructed on the soft ground 11 of the road foundation with a length that does not reach the supporting layer below the soft ground and with an improvement rate of 10 to 50%. By laying a reinforcing mesh body 21 on the body 20 and further adding either or both of an additive material and / or an additive to the earth and sand and the solidifying material on the reinforcing mesh body 21 to solidify The shallow improved soil layer 13 is laid, and this shallow improved soil layer 1
3 is a road construction method characterized in that a road pavement 18 is constructed on top of the construction No. 3. Reinforcing net 21 on top of column 20
Is laid, and one or both of the additive and the additive are further added to the soil and the solidifying material, and mixed and solidified to lay the shallow improved soil layer 13, and the road pavement 18
By doing so, the thickness of the crusher run layer 3a shown in FIGS. 9 and 10 can be reduced, and the consolidation settlement due to the dynamic load on the road can be further suppressed. Further, since the columnar body 20 has a length that does not reach the supporting layer below the soft ground 11, the construction period is shortened and the construction cost is reduced.

In the invention according to claim 2, as shown in FIG. 2, a plurality of columnar bodies 20 are provided in the soft ground 11 in the vicinity of the underground structure 12 which is buried in the soft ground 11 of the road foundation and whose settlement is suppressed. Constructed at an improvement rate of 10 to 50% such that the length does not reach the support layer 16 below the soft ground and becomes gradually shorter as the distance from the underground structure 12 increases, and the reinforcing net-like structure is provided on the plurality of columnar bodies 20. The road construction method is characterized in that a body 21 is laid and a road pavement 18 is constructed on the underground structure 12 and the reinforcing net 21. Columnar body 20
By performing the road pavement 18 through the reinforcing net 21 on the above, the improved ground 2 shown in FIGS. 11 and 12 can be omitted, and the consolidation settlement due to the dynamic load of the road can be suppressed, Moreover, since the plurality of columnar bodies 20 are gradually shortened as the distance from the underground structure 12 is increased, when the road is used, the consolidation settlement is suppressed as much as possible in the vicinity of the underground structure 12, and the distance is gradually increased as the distance increases. Allow a certain degree of consolidation settlement. Accordingly, it is possible to suppress the step generated at the boundary between the portion above the underground structure 12 of the road and the portion adjacent thereto. Further, since the columnar body 20 has a length that does not reach the support layer 16 below the soft ground 11, the construction period is shortened and the construction cost is reduced.

In the invention according to claim 3, as shown in FIG. 3, a plurality of columnar bodies 20 are provided in the soft ground 11 near the underground structure 12 which is buried in the soft ground 11 of the road foundation and whose settlement is suppressed. Constructed at a rate of improvement of 10 to 50% so that the length does not reach the support layer 16 below the soft ground and becomes gradually shorter as it goes away from the underground structure 12, and solidification with earth and sand on these plural columnar bodies 20. A road construction method characterized by laying a shallow improved soil layer 13 by mixing and solidifying materials and constructing a road pavement 18 on the underground structure 12 and the shallow improved soil layer 13. is there. The invention according to claim 4 is the invention according to claim 3, wherein either one or both of the additive and the additive are further added to the earth and sand and the solidifying material, and they are mixed and solidified to form a shallow layer improved soil layer. It is a road construction method for laying 13. A shallow improved soil layer 13 is laid on the columnar body 20 by further adding one or both of the additive and the additive to the solidifying material and the solidifying material to solidify, and the road pavement 18 is laid on this. By performing
Also, the thickness of the crusher run layer 3a shown in FIG. 12 can be reduced to suppress consolidation settlement due to a dynamic load on the road, and the plurality of columnar bodies 20 are gradually shortened as they are moved away from the underground structure 12. Therefore, as in the invention according to claim 2, when the road is used, a step is not generated at the boundary between the portion above the underground structure 12 of the road and the portion adjacent thereto. Further, since the columnar body 20 has a length that does not reach the support layer 16 below the soft ground 11, the construction period is shortened and the construction cost is reduced.

In the invention according to claim 5, as shown in FIG. 4, a plurality of columnar bodies 20 are provided in the soft ground 11 near the underground structure 12 which is buried in the soft ground 11 of the road foundation and whose settlement is suppressed. Constructed at an improvement rate of 10 to 50% such that the length does not reach the support layer 16 below the soft ground and becomes gradually shorter as the distance from the underground structure 12 increases, and the reinforcing net-like structure is provided on the plurality of columnar bodies 20. The body 21 is laid, and the shallow improved soil layer 13 is laid by further adding one or both of the additive and the additive to the solidifying material on the reinforcing net 21 and mixing and solidifying However, the road construction method is characterized in that the road pavement 18 is constructed on the underground structure 12 and the shallow layer improved soil layer 13. The reinforcing net 21 is laid on the columnar body 20, and the sand and the solidifying material are further added with either one or both of the additive material and the additive, and the mixture is mixed to solidify the shallow layer improved soil layer. By laying 13 and further performing road pavement 18, the thickness of the crusher run layer 3a shown in FIGS. 11 and 12 can be reduced, and the consolidation settlement due to the dynamic load of the road can be further suppressed. Further, since the plurality of columnar bodies 20 are gradually shortened as the distance from the underground structure 12 is increased, as in the invention according to claim 2, when the road is used, the top of the underground structure 12 of the road is increased. It is possible to suppress the step generated at the boundary between the portion of and the portion adjacent thereto. Further, since the columnar body 20 has a length that does not reach the support layer 16 below the soft ground 11, the construction period is shortened and the construction cost is reduced.

The invention according to claim 6 is the invention according to claim 1, 4 or 5, wherein either one or both of the additive and the additive are further added to the earth and sand and the solidifying material, and the mixture is wet-mixed and solidified. This is a road construction method for laying the improved shallow soil layer 13. By wet mixing, dust generation by powder at the construction site is suppressed, and the environment near the site is not contaminated with powder. In addition, the wet mixing method does not require compaction and can reduce variations in quality.

The invention according to claim 7 relates to claims 1, 4, 5
Or the invention according to 6, wherein the additive material is foamed beads or rice husks, the additive is a bubble generator, and either one or both of the additive material and the additive is foamed beads, rice husks and bubble generators It is a road construction method that is one or more low-density bodies selected from the group. Shallow layer improved soil layer 1 by adding low density material as additive or additive
3 can be made lighter and the static load due to the shallow layer improved soil layer can be reduced. Further, since the low density body absorbs the vibration due to the dynamic load, the amount of dynamic consolidation settlement can be reduced.

The invention according to claim 8 relates to claims 1, 4, and 5.
Or the invention according to 6, wherein the additive material is a road construction method in which the additive material is a clinker formed by incineration of industrial waste. According to this construction method, it is possible to effectively utilize the clinker which is formed by the incineration of industrial waste and is in need of disposal.

The invention of claim 9 relates to claim 1, 4, 5
Or the invention according to 6, wherein the additive is an inorganic fiber or a synthetic fiber. By adding the above fibers as an additive, the shallow improved soil layer 13 is reinforced,
Prevents cracking of the improved ground due to traffic load and improves the durability of the improved ground. Further, even if the layer thickness is made thinner than the shallow improved soil layer containing no fibers, the same durability as that of the shallow improved soil layer containing no fibers can be obtained.

The invention according to claim 10 is the invention according to any one of claims 1 to 3 or 5, which is a columnar body 20.
Is a road construction method with ready-made piles or ground improvement columns. By using ready-made piles for the pillars, it is possible to construct at a lower construction period and at a lower cost, and by using the ground improvement pillars, it is possible to more reliably prevent consolidation settlement of roads.

As shown in FIG. 5, the invention according to claim 11 is the invention according to any one of claims 1 to 3 or 5, wherein the columnar body 20 is a ground improvement columnar body. This is a road construction method in which a body portion 20a of a body 20 has a node portion 20b. By providing the node portion 20b on the trunk of the ground improvement columnar body, the sinking resistance of the ground improvement columnar body is increased,
The settlement of roads can be prevented more reliably.

As shown in FIG. 6, the invention according to claim 12 is the invention according to any one of claims 1 to 3, 5 or 11, wherein the columnar body 20 is a ground improvement columnar body,
The tip of the columnar body 20 has an enlarged portion 2 having a diameter larger than that of the body portion 20a.
It is a road construction method with 0c. By providing the enlarged portion 20c having a larger diameter than the trunk portion at the tip of the soil improvement columnar body, the settlement resistance of the soil improvement columnar body is increased, and the consolidation settlement of the road can be prevented more reliably.

The invention according to claim 13 is the invention according to any one of claims 1 to 3, 5, 11 or 12, wherein the columnar body 20 is a ground improvement columnar body.
Is a road construction method that includes inorganic fibers or synthetic fibers.
By including the fibers in the columnar body, even if a crack is generated in the columnar body due to the lateral flow of the soft ground, the bending resistance of the columnar body is exerted, and the lateral flow thereafter can be suppressed.

The invention according to claim 14 is the invention according to any one of claims 1 to 3, 5 or 11 to 13, wherein the columnar body 20 is a ground improvement columnar body. It is a road construction method constructed by mechanical stirring or high-pressure jet stirring. By constructing the ground improvement columnar body by the mechanical agitation method, it is possible to inexpensively build the outer diameter of the improvement body regardless of the soil quality. Further, by constructing the ground improvement columnar body by the high-pressure injection stirring method, the construction machine can be made smaller and lighter, and the construction machine can be constructed even in a narrow place or under an existing step plate.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, a columnar body which does not reach a supporting layer below the soft ground is constructed on a soft ground, and a reinforcing net or a shallow improved soil layer or a reinforcing net is formed on the pillar. And the improved shallow soil layer. When the above-mentioned combination is adopted, the value L obtained by adding the thickness of the shallow layer improved soil layer to the length of the columnar body and the thickness of the road pavement suppresses the consolidation settlement due to the traffic load, that is, the dynamic load. It is a big condition. Build the improvement rate of the columnar body in the range of 10-50%,
Moreover, if this value L is set to 4 m or more, consolidation settlement due to a dynamic load can be substantially eliminated. Here, the improvement rate of the columnar body means the percentage of the cross-sectional area of the columnar body to the unit area of the improved ground when the columnar body is viewed from above as shown in FIGS. 7 and 8. If the improvement rate of the columnar body is less than 10%, consolidation settlement cannot be sufficiently suppressed, and if it exceeds 50%, there is a problem that the construction period and the construction cost are rather increased. Preferably, this improvement rate is 15 to 30%.

The above value L is required to be 4 m or more, but even if it is increased, the effect of suppressing the dynamic consolidation settlement is not so great. However, as the value L increases, the effect of suppressing static consolidation settlement increases accordingly. In the present invention, in order to avoid excessive ground improvement, the lower end of the columnar body does not reach the support layer 16 below the soft ground 11 as shown in FIGS. Although the support layer is not shown in FIG.
0 does not reach the support layer. The maximum value of this value L is appropriately determined in consideration of the layer thickness of the soft ground and its softness, the load condition, the economical efficiency and the like. As shown in FIG. 2, the road improved pavement 1 is directly provided on the reinforcing net 21 without providing the improved shallow soil layer.
When 8 is applied, it is necessary to increase the improvement rate of the columnar body 20. As shown in Fig. 2 to Fig. 4, when the long pillars are constructed near the underground structure, and the pillars are gradually shortened as they are separated from the underground structure, the step eliminating method is efficient and economical. Since it is necessary to do so, the conditions for ground improvement near the underground structure are the same as those for the improvement over the entire length of the road shown in Fig. 1, and the length of the pillar gradually shortens as the distance from the underground structure increases. , And finally becomes zero.

The reinforcing net 21 of the present invention shown in FIGS. 1, 2 and 4 is a net formed of a material such as an inorganic fiber, a synthetic fiber, a synthetic resin or steel. The mesh-like body made of inorganic fibers or synthetic fibers is a string-like body made of the fibers and meshed. Inorganic fibers are glass fibers, synthetic fibers are polyamide-based nylon fibers,
Examples include polyolefin-based polyethylene fibers and polypropylene fibers. Examples of the synthetic resin include polyethylene and polypropylene resin. The reticulate body made of steel is formed by making a large number of cuts in parallel with each other in a plate-shaped steel leaving a peripheral edge and then pulling both edges of the plate-shaped steel in a direction orthogonal to the cuts. The mesh size of the mesh is 10 to 200 mm, and one reinforcing mesh or a plurality of reinforcing meshes may be used depending on the required degree of reinforcement.

The shallow improved soil layer 13 of the present invention shown in FIGS. 1, 3 and 4 is earth and sand, a cement in the form of powder or slurry, a cement-based solidifying material, a solidifying material such as quick lime, an additive material or It is laid by uniformly mixing one or both of the additives and solidifying. Depending on the water content of the target ground, it may be mixed and compacted to form a shallow improved soil layer, or it may be formed without compaction. When the water content of the target ground is low, if a solidifying material in the form of a slurry is used, and either one or both of the additional material or the additive is further added to this solidifying material and earth and sand and wet mixed, powder at the construction site Dust generation is suppressed and the environment near the site is not contaminated with powder.

Examples of the additive of the present invention include foamed beads, low-density materials such as rice husks, clinker formed by incineration of industrial waste, inorganic fibers or synthetic fibers. Further, the additive of the present invention includes a bubble generator. The above-mentioned additives or additives may be added singly or as a mixture of two or more kinds. You may mix an additive and an additive. Foamed beads are 2 per 100% by volume of the material forming the shallow soil layer.
Add 0-50% by volume. If it is less than 20% by volume, the purpose of addition cannot be achieved, and if it exceeds 50% by volume, the strength of the shallow-layer improved soil layer when solidified decreases. By adding the low density body, the shallow layer improved soil layer can be made lighter in weight, the static consolidation settlement amount can be reduced, and the elastic coefficient of the shallow layer improved soil layer can be reduced to absorb the dynamic load due to traffic load. . Along with this, even if the length of the columnar body is shortened, consolidation settlement can be prevented.

Examples of the low-density air bubble generator include polyoxyethylene alkyl ether compounds and higher alcohol sulfate ester compounds. This bubble generator is a liquid before mixing, but is a substance that entrains bubbles in the layer when forming the shallow improved soil layer. When the rice husk is made into a low-density body, the rice husk contains a large amount of SiO ₂ so that it has a high corrosion resistance, and because of its shape, it has a resistance to traffic load in order to increase the shear strength of the shallow improved soil layer for a long time. large. The diameter formed by incineration of industrial waste is 5
When a clinker having a diameter of mm or less is used as the additive, the clinker that is in need of disposal can be effectively used.

When an inorganic fiber or a synthetic fiber is used as the additive, the inorganic fiber such as a steel fiber having a length of about 2 to 4 cm, or the polyamide type nylon fiber or the polyolefin type polyethylene fiber having a length of about 4 to 7 cm is preferable. A synthetic fiber made of polypropylene fiber is used. When the length is less than the above lower limit, the reinforcing effect is poor, and when the length exceeds the above upper limit, it becomes difficult to handle when mixing with other materials. By adding the above fibers as an additive, the shallow improved soil layer is reinforced and cracks of the improved ground due to traffic loads are prevented,
The durability of the improved ground is improved. Further, even if the layer thickness is made thinner than the shallow improved soil layer containing no fibers, the same durability as that of the shallow improved soil layer containing no fibers can be obtained. In order to achieve the above object, rice husks, inorganic fibers or synthetic fibers are 0.1 to 5.0% by volume, preferably 0.2 to 2 with respect to 100% by volume of the material for forming the shallow layer improved soil layer. 0.0% by volume, and the clinker is added at 30% by volume or less. The bubble generator is 0.01 with respect to 100% by weight of the material forming the shallow soil layer.
.About.1.0 wt%, preferably 0.1 to 0.5 wt%.

The method of constructing the columnar body includes a method of driving a prefabricated pile such as a wooden pile, a prefabricated concrete pile, and a steel pile into the deep ground, and a method of constructing a ground improvement columnar body. By using ready-made piles for the pillars, it is possible to construct at a lower construction period and at a lower cost, and by using the ground improvement pillars, it is possible to more reliably prevent consolidation settlement of roads. There are mechanical agitation method and high-pressure jet agitation method as construction methods for constructing this soil improvement columnar body, but if the soil improvement columnar body is constructed by the mechanical agitation method, it will be cheaper and the outer diameter of the improvement body will be constant regardless of the soil quality. can do. Further, by constructing by a high-pressure jet agitation method, the construction machine can be made smaller and lighter, and the construction machine can be constructed even in a narrow place or under an existing step plate. When constructing this soil improvement columnar body, as shown in FIG. 5, the node portion 20b is provided on the body portion 20a of the soil improvement columnar body 20.
Can also be formed. As a result, the frictional force on the peripheral surface of the soil improvement columnar body increases, the settlement resistance increases, and the consolidation settlement of the road can be prevented more reliably. There is also an advantage that lateral flow of soft ground is less likely to occur. Further, when constructing the soil improvement columnar body, as shown in FIG. 6, an enlarged portion 20c having a diameter larger than the trunk portion 20a is provided at the tip of the soil improvement columnar body 20.
Can also be formed. As a result, the settlement resistance of the ground improvement columnar body is further increased, and the consolidation settlement of the road can be prevented more reliably.

Further, the ground improvement columnar body 20 may contain inorganic fibers or synthetic fibers. In this case, preferably, the inorganic fibers are steel fibers having a length of about 2 to 4 cm,
As the synthetic fiber, polyamide-based nylon fiber, polyolefin-based polyethylene fiber or polypropylene fiber having a length of about 4 to 7 cm is used. When the length is less than the above lower limit, the reinforcing effect is poor, and when the length exceeds the above upper limit, it becomes difficult to handle when mixing with other materials. This fiber is contained in an amount of about 0.2 to 2.0% by volume based on all materials forming the ground improvement columnar body. By including the fibers in the columnar body, even if a crack is generated in the columnar body due to the lateral flow of the soft ground, the bending resistance of the columnar body is exerted, and the lateral flow thereafter can be suppressed.

By constructing the columnar body, lateral flow of the ground due to dynamic load can be prevented. A method of constructing the columnar body when viewed from above will be described based on FIGS. 7 and 8. Considering the efficiency and economy of construction, the planar arrangement of the pillars should be a lattice arrangement as shown in FIG. 7 or a non-contact staggered arrangement as shown in FIG. It is preferable to suppress it. Improvement rate of 10
When the lattice-like arrangement shown in FIG. 7 is set in the range of 50%, the lattice spacing d ₁ (however, the lattice spacing d ₁ ≧ the lattice spacing d ₂ )
Is less than or equal to twice the height from the upper end of the columnar body to the road pavement surface, and similarly, 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 and the columnar body spacing d ₃ (wherein the columnar body spacing d ₃ ≧ columnar body spacing d ₄ ) is not more than twice the height from the upper end of the columnar body to the road pavement surface. The static load and the dynamic load, respectively, are reliably transmitted to the columnar body, and the lateral flow of the ground can be sufficiently prevented.

As shown in FIGS. 1 to 4, the road pavement 18 of the present invention comprises a crusher run layer 18a and a particle size adjusting crushed stone layer 1
8b and asphalt concrete 18c.
1 to 4, the crusher run layer 18a is 5 to
The thickness of the crushed stone layer 18b is 10 to 30
cm thickness, asphalt concrete 18c
Are laid to a thickness of 10 to 40 cm.

[0031]

Embodiments of the present invention will now be described with reference to the drawings together with comparative examples. <Example 1> As shown in FIG. 1, a ground improvement columnar body 20 was constructed on a target soft ground 11 by a mechanical stirring method with a length that did not reach a supporting layer below the soft ground 11. At this time, each columnar body has a diameter a of 80 cm and a length L ₄ of 400 cm.
And the intervals d ₃ and d ₄ shown in FIG.
m, improvement rate 25.7%, non-contact staggered construction. On the ground improvement columnar body 20, a reinforcing net 21 made of glass fiber is laid, on which cement powder is added to excavated soil and separately prepared earth and sand, and rice husk as a low density body is further added as an additive. After adding 20% by weight of the whole material, dry-mixing, and compacting
It was laid to a thickness of ₅ = 60 cm. A crusher run layer 18a is laid on this layer with a thickness of 30 cm, and a particle size adjusting crushed stone layer 18b is laid on it with a thickness of 10 cm, and an asphalt concrete 18b with a thickness of 5 cm is laid on it.
Paved with. The total length L shown in FIG. 1 was 505 cm. <Comparative Example 1> As shown in FIG. 9, the same target soft ground 1 as in Example 1 is excavated, a cement-based solidifying material is added to the excavated soil and separately prepared earth and sand, and the mixture is dry-mixed and then compacted. As a result, the shallow layer improved soil layer 2a was laid in a thickness of 60 cm. A crusher run layer 3a having a thickness of 30 cm is provided thereon, and a crushed stone layer 3b for particle size adjustment is further laid thereon to have a thickness of 10 cm, and the upper layer is paved with asphalt concrete 4 having a thickness of 5 cm. . The total length L shown in FIG. 9 was 105 cm. <Comparative Example 2> As shown in FIG. 10, the same target soft ground 1 as in Example 1 was excavated, and quick lime was added as a solidifying material to the excavated soil and separately prepared earth and sand, and the mixture was dry-mixed and then compacted. Thus, the shallow layer improved soil layer 2b was laid to a thickness of 150 cm. Fe lime was dry-mixed on the shallow improved soil layer 2b and then solidified to form a shallow improved soil layer 2c having a thickness of 30 cm. After providing the crusher run layer 3a with a thickness of 30 cm on the shallow improved soil layer 2c, a crushed stone layer 3b for grain size adjustment is further laid with a thickness of 10 cm on the crusher run layer 3a.
5 cm thick asphalt concrete on it 4
Paved with. The total length L shown in FIG. 10 was 225 cm. <Example 2> As shown in FIG. 2, the same soft ground 11 as in Example 1 was excavated, and the underdrain which was the underground structure 12 was supported on the support layer 16 through the support piles 17. Each of the target soft ground 11 in the vicinity has a diameter a by mechanical stirring method.
A ground improvement columnar body 20 having a length of 80 cm was constructed with a length that does not reach the support layer 16 below the soft ground 11. At this time, the ground improvement columnar body 20 was constructed so that the columnar body was gradually shortened as the columnar body moved away from the underdrain. The length L ₇ of the columnar body closest to the underdrain is 400 cm, and the columnar bodies have the intervals d ₁ and d ₂ shown in FIG. 8 of 125 cm, respectively, and the improvement rate is 25.7%.
Then, it was constructed in a non-contact staggered arrangement. Ground improvement columnar body 20
Laying a reinforcing net 21 made of glass fiber on the
A crusher run layer 18a having a thickness of 30 cm is laid on the crusher run layer 18a, and a crushed stone layer 18b having a particle size adjustment of 10 cm is further provided on the crusher run layer 18a.
Of the asphalt concrete 18c having a thickness of 5 cm. The depth L ₆ from the lower end of the longest ground improvement column shown in FIG. 2 to the support layer 16 is 2
It was 0 m, and the total length L was 445 cm. <Embodiment 3> As shown in FIG. 3, the same soft ground 11 as in Embodiment 1 is excavated, and after supporting the underdrain 12 on the support layer 16 in the same manner as in Embodiment 2, the soft ground in the vicinity of this underdrain. 11
As in Example 2, the ground-improving columnar bodies 20 each having a diameter a of 80 cm were mechanically agitated so that the columnar bodies gradually became shorter as they moved away from the underdrain, and did not reach the supporting layer 16 below the soft ground 11. I built it. The length L ₉ of the columnar body closest to the underdrain was 400 cm, and the columnar bodies were constructed in a non-contact staggered arrangement with intervals d ₃ and d ₄ shown in FIG. 8 of 125 cm and an improvement rate of 25.7%. . On the ground improvement columnar body 20, the slurry type cement-based solidifying material is added to the excavated soil and the separately prepared earth and sand, and 30% by volume of the low-density foamed beads as an additive material is added to the whole material, and the mixture is wet mixed. Then, the improved shallow soil layer 13 was laid in a thickness of L ₁₀ = 30 cm. A crusher run layer 18a was laid on this to a thickness of 30 cm, a particle size adjusting crushed stone layer 18b was further laid on this to a thickness of 10 cm, and an asphalt concrete 18c having a thickness of 5 cm was paved on it. The depth L ₈ from the lower end of the longest ground improvement column shown in FIG. 3 to the support layer 16 is 20 m, and the total length L is 475 cm.
Met. <Embodiment 4> As shown in FIG. 4, the same soft ground 11 as in Embodiment 1 is excavated, and after supporting the underdrain 12 on the support layer 16 in the same manner as in Embodiment 2, the soft ground in the vicinity of this underdrain. 11
As in Example 2, the ground-improving columnar bodies 20 each having a diameter a of 80 cm were mechanically agitated so that the columnar bodies gradually became shorter as they moved away from the underdrain, and did not reach the supporting layer 16 below the soft ground 11. I built it. The length L ₁₂ of the columnar body closest to the underdrain was 400 cm, and the columnar bodies were constructed in a non-contact staggered arrangement with intervals d ₃ and d ₄ shown in FIG. 8 of 125 cm and an improvement rate of 25.7%. . On the ground improvement columnar body 20, a reinforcing net 21 made of glass fiber is laid, on which cement powder is added to excavated soil and separately prepared earth and sand, and rice husk as a low density body is further added as an additive. 20% by volume of the entire material was added, dry-mixed, and then compacted to form a shallow-layer improved soil layer 13 with L ₁₃ = 3.
It was laid to a thickness of 0 cm. A crusher run layer 18a is laid on this to a thickness of 30 cm, and a particle size adjusting crushed stone layer 18b is further laid on this to a thickness of 10 cm, and 5
It was paved with 18 cm thick asphalt concrete 18c. The depth L ₁₁ from the lower end of the longest soil improvement columnar body to the support layer 16 shown in FIG. 4 is 20 m, and the total length L is 4
It was 75 cm. <Comparative Example 3> As shown in FIG. 11, the same soft ground 1 as in Example 1 was excavated, and the underdrain 6 was supported on the support layer 7 via the support piles 8 in the same manner as in Example 2, and then, The soft ground 1 near the underdrain is excavated, the cement-based solidifying material is added to the excavated soil and the separately prepared soil, the mixture is dry-mixed, and then the shallow-improved soil layer 2a is laid to a thickness of 60 cm by compaction. did. A crusher run layer 3a having a thickness of 30 cm is provided thereon, and a crushed stone layer 3b for particle size adjustment is further laid thereon to have a thickness of 10 cm, and the upper layer is paved with asphalt concrete 4 having a thickness of 5 cm. . The total length L shown in FIG. 11 was 105 cm. <Comparative Example 4> As shown in FIG. 12, the same soft ground 1 as in Example 1 was excavated, and the underdrain 6 was supported on the support layer 7 via the support piles 8 in the same manner as in Example 2, and then, Excavating the soft ground 1 in the vicinity of the underdrain, adding quicklime to the excavated soil and separately prepared earth and sand as a solidifying material, dry-mixing, and then compacting to lay a shallow improved soil layer 2b to a thickness of 150 cm. did. Fe lime was dry-mixed on the shallow improved soil layer 2b and then solidified to form a shallow improved soil layer 2c having a thickness of 30 cm. A crusher run layer 3a having a thickness of 30 cm is provided on the shallow improved soil layer 2c, and a crushed stone layer 3b for particle size adjustment is further laid on the crusher run layer 3a having a thickness of 10 cm. Paved with asphalt concrete 4. The total length L shown in FIG. 12 was 225 cm. <Comparative Example 5> An example except that the ground improvement columnar body 20 shown in FIG. 3 was elongated and the lower end of the columnar body was embedded in the lower support layer 16 of the soft ground (not shown). The ground was improved in the same manner as 3. <Comparative Test and Results> Regarding the amount of subsidence and the occurrence of steps of roads constructed by the various construction methods of Examples 1 to 4 and Comparative Examples 1 to 5, from the time of construction to the time of starting use And the period from the start of use until 720 days have passed. Further, with respect to the construction cost required for road construction, the estimated values of other examples and comparative examples when Example 1 was set to 100 were examined. The results are shown in Table 1.

[0032]

[Table 1]

(A) About the amount of subsidence and occurrence of steps:
As is clear from Table 1, both the road constructed by the construction method of Example 1 and the road constructed by the construction methods of Comparative Examples 1 and 2 have a settlement amount by static load until the start of use. It was small, and no significant difference was observed between the construction method of Example 1 and the construction methods of Comparative Examples 1 and 2. However, after the road was used, due to the dynamic load, the road subsidence by the construction method of Comparative Examples 1 and 2 was large, whereas the road subsidence by the construction method of Example 1 was small. .

When a columnar body is constructed in the vicinity of the underdrain which is an underground structure, the road constructed by the construction method of Examples 2 to 4 and the road constructed by the construction method of Comparative Example 5 are started to be used. The amount of subsidence due to the static load up to the point is small, and the step A shown in FIGS. 11 and 12 is not seen,
No significant difference was found between the construction method of Examples 2 to 4 and the construction method of Comparative Example 5. Moreover, it cannot be said that there is a significant difference among the three examples. However, the roads constructed by the construction methods of Comparative Examples 3 and 4 have a relatively large subsidence amount due to static load until the start of use, and thus the roads between the construction methods of the other Examples 2 to 4 and the construction method of Comparative Example 5 are relatively large. There was a significant difference. In addition, after the road was used, due to the dynamic load, Comparative Example 3,
The subsidence amount of the road by the construction method of No. 4 was remarkably large, and the step A clearly appeared, whereas the subsidence amount of the roads by the construction methods of Examples 2 to 4 and Comparative Example 5 were all small, and no step was generated. . Among the roads produced by the construction methods of Examples 2 to 4, particularly, Examples 2 and 3 have a relatively small subsidence amount,
The value was comparable to that of Comparative Example 5. (b) Construction cost: When the construction cost of the construction method of Example 1 is 100, the estimated construction cost of each construction method of other Examples 2 to 4 is:
Although it was more expensive than the estimated value of the construction cost of each of the construction methods of Comparative Examples 1 to 4 with a large subsidence amount, about the estimated value of the construction cost of the construction method of Comparative Example 5 in which the lower end of the columnar body was embedded in the support layer. 20% ~
It was as low as about 27%.

[0035]

As described above, according to the present invention, a road can be constructed at a low cost in a relatively short construction period without excessive ground improvement that unnecessarily prolongs the construction period. It is possible to suppress consolidation settlement due to dynamic load when a road constructed by embankment is used. Also,
When a road crossing an underground structure such as an underdrain installed on soft ground is used, a step may be created at the boundary between the upper part of the underground structure and the adjacent part. There is no excellent effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view seen from a direction orthogonal to a road direction constructed by a construction method according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view seen from a direction orthogonal to a road direction constructed by a construction method according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view seen from a direction orthogonal to a road direction constructed by a construction method according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view seen from a direction orthogonal to a road direction constructed by a construction method according to a fourth embodiment of the present invention.

FIG. 5 is a front view of a ground improvement columnar body having a knotted portion on the body of the present invention.

FIG. 6 is a front view of a ground improvement columnar body having an enlarged portion at the tip of the present invention.

FIG. 7 is a plan view of a ground improvement columnar body arranged in a grid pattern according to the present invention.

FIG. 8 is a plan view of a ground improvement columnar body arranged in the non-contact staggered pattern of the present invention.

FIG. 9 is a cross-sectional view seen from a direction orthogonal to the road direction constructed by the method of Comparative Example 1.

FIG. 10 is a cross-sectional view seen from a direction orthogonal to the road direction constructed by the construction method of Comparative Example 2.

FIG. 11 is a cross-sectional view seen from a direction orthogonal to the road direction constructed by the method of Comparative Example 3.

FIG. 12 is a cross-sectional view seen from a direction orthogonal to a road direction constructed by a construction method of Comparative Example 4.

[Explanation of symbols]

11 soft ground 12 Underground structure 13 Shallow layer improved soil layer 16 Support layer 17 Support pile 18 road pavement 18a Crusher run layer 18b Grain size adjusted crushed stone layer 18c asphalt concrete 20 columns 20a body 20b node 20c Enlarged section 21 Reinforcing mesh

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 000133881             Tenox Co., Ltd.             6-13-7 Akasaka, Minato-ku, Tokyo (71) Applicant 000006264             Mitsubishi Materials Corporation             1-5-1 Otemachi, Chiyoda-ku, Tokyo (72) Inventor Tetsuhiko Miura             12-4 Tatemachi, Saka City, Saga Prefecture (72) Inventor Kazuyuki Fujikawa             Stock number 2-34-5 Minamiikebukuro, Toshima-ku, Tokyo             Company Diamond Consultant (72) Inventor Takeaki Hama             2-4-4 Sotokanda East, Chiyoda-ku, Tokyo             Inside Kyoho Co., Ltd. (72) Inventor Hideki Tanaka             4-1-1 Tenjin, Chuo-ku, Fukuoka City, Fukuoka Prefecture             Tenox Kyushu Co., Ltd. (72) Inventor Shigeru Yoshida             6-13-7 Akasaka, Minato-ku, Tokyo Co., Ltd.             In Tenox (72) Inventor Isao Kobayashi             3-5-1 Otemachi, Chiyoda-ku, Tokyo             Ryo Materials Co., Ltd. F-term (reference) 2D040 AB05 AB14 AB16 AC05 BB02                       BD00 BD02 BD05 BD06 CA01                       CA03 CA10 CB01 CB03                 2D051 AA09 AD07 AE04 AF01 AF02                       AH01 CA01 CA04 CA05 CA09

Claims (14)

[Claims] 1. Construction of a plurality of pillars (20) on a soft ground (11) of a road foundation with a length not reaching a supporting layer below the soft ground (11) and with an improvement rate of 10 to 50%. Then, the reinforcing net (21) is laid on the plurality of columnar bodies (20), and either one of the additive or the additive to the earth and sand and the solidifying material on the reinforcing net (21). Alternatively, both are further added and mixed to solidify to lay a shallow improved soil layer (13), and a road pavement (18) is constructed on the shallow improved soil layer (13). Road construction method. 2. The soft ground (11) in the vicinity of an underground structure (12) embedded in the soft ground (11) of a road foundation and restrained from sinking.
A plurality of columnar bodies (20) in a length that does not reach the supporting layer (16) below the soft ground (11) and becomes 10 to 50% so as to become gradually shorter as the distance from the underground structure (12) increases. Constructed at an improvement rate of, the reinforcing net (21) is laid on the plurality of columnar bodies (20), and the underground structure (12) and the reinforcing net.
Road construction method characterized by constructing road pavement (18) on (21). 3. The soft ground (11) in the vicinity of an underground structure (12) embedded in the soft ground (11) of a road foundation and restrained from sinking.
A plurality of columnar bodies (20) in a length that does not reach the supporting layer (16) below the soft ground (11) and becomes 10 to 50% so as to become gradually shorter as the distance from the underground structure (12) increases. Constructed at a rate of improvement of, the shallow improved soil layer (13) is laid by mixing and solidifying earth and sand and a solidifying material on the plurality of columnar bodies (20), and the underground structure (12) And a road construction method characterized by constructing a road pavement (18) on the shallow improved soil layer (13). 4. The shallow improved soil layer (13) is laid by further adding one or both of an additive and an additive to the soil and the solidifying material and mixing and solidifying them. Construction method. 5. The soft ground (11) in the vicinity of an underground structure (12) embedded in the soft ground (11) of a road foundation and suppressed in settlement.
A plurality of columnar bodies (20) in a length that does not reach the supporting layer (16) below the soft ground (11) and becomes 10 to 50% so as to become gradually shorter as the distance from the underground structure (12) increases. Constructed at a rate of improvement, laying a reinforcing mesh body (21) on the plurality of columnar bodies (20), and adding material or addition to earth and sand and solidifying material on the reinforcing mesh body (21). Lay the shallow improved soil layer (13) by further adding either one or both of the agents and solidifying, and road over the underground structure (12) and the shallow improved soil layer (13). Road construction method characterized by building pavement (18). 6. The shallow improved soil layer (13) is laid by further adding either one or both of the additive and the additive to the soil and the solidifying material and wet mixing to solidify. Road construction method described in 5. 7. The additive comprises foam beads or rice husks,
The additive comprises a bubble generator, and one or both of the additive and the additive are one or more low-density substances selected from the group consisting of foam beads, chaff and bubble generator. The road construction method according to Item 1, 4, 5 or 6. 8. The road construction method according to claim 1, 4, 5 or 6, wherein the additive material is a clinker formed by incineration of industrial waste. 9. The road construction method according to claim 1, 4, 5 or 6, wherein the additive material is an inorganic fiber or a synthetic fiber. 10. The road construction method according to claim 1, wherein the pillars (20) are ready-made piles or ground improvement pillars. 11. The columnar body (20) is a ground improvement columnar body, and a trunk portion (20a) of the columnar body (20) has a node portion (20b), according to any one of claims 1 to 3 or 5. Road construction method described in. 12. The columnar body (20) is a ground improvement columnar body, and the tip of the columnar body (20) has an enlarged portion (20c) having a larger diameter than the trunk portion (20a). The road construction method according to any one of 5 and 11. 13. The columnar body (20) is a ground improvement columnar body, and the columnar body (20) contains an inorganic fiber or a synthetic fiber, according to any one of claims 1 to 3, 5, 11 or 12. Road construction method. 14. The columnar body (20) is a ground improvement columnar body, and the columnar body (20) is constructed by a mechanical stirring method or a high-pressure jet stirring method.
3. The road construction method according to any one of items.