JP4915827B1 - Ground strengthening system and ground strengthening method - Google Patents

Abstract

A ground strengthening system and a ground strengthening method having a function of a drainage drain together with strong support to the ground.
SOLUTION: An elongated columnar body 3 formed by restraining a crushed stone 6 with a water-permeable sheet 4 having a mesh made of a polymer fiber material is vertically disposed inside a ground 1 on which the building is built. Arrange. The columnar body 3 includes a spherical portion 3A that protrudes in a spherical shape larger than the column portion at the lower end, and the crushed stone 6 receives a compressive force in the vertical direction from the load from above and the tip support force of the spherical portion 3A from below. The internal pressure is increased and the strength is maintained by suppressing the bulging to the side by the tensile strength of the water-permeable sheet 4. Therefore, the columnar body 3 reliably supports the ground 1 from the load of the building, and has flexibility to follow deformation from the side of the ground 1 from its flexible structure, and can be buckled by the force. Absent. Moreover, the columnar body 3 drains out of the ground 1 promptly when rainwater or groundwater pressure rises as a crushed stone drain.
[Selection] Figure 1

Description

  The present invention relates to a soft ground strengthening technique for strengthening the ground where a building stands and a liquefaction prevention technique corresponding to the liquefaction of the ground, and in particular, to realize the ground ground strengthening of a detached house at a low cost. The present invention also relates to a ground strengthening system and a ground strengthening method for reducing ground liquefaction.

  For relatively large-scale reinforced concrete buildings and steel buildings such as buildings and condominiums, a foundation pile structure that reaches a solid ground foundation layer deep in the ground of the erected land is buried, and the foundation pile structure is placed on the foundation pile structure. Built. As construction methods of foundation pile structures of these large-scale buildings, various foundation pile materials such as steel pipe piles and PHC piles are constructed by various embedment methods that embed the land into the ground by cutting or hammering or hydraulic pressure. .

  On the other hand, in the construction of detached houses and relatively small apartment houses, full-scale foundation pile construction as described above is often difficult due to cost problems. In the case of soft ground that is determined not to meet certain standards, the ground surface improvement work (soil replacement, etc.) is carried out, and then a simple reinforced concrete housing foundation is applied to build the house. It is normal.

  On the other hand, the collapse of house ground due to large earthquakes and landslides caused by heavy rains in recent years has frequently occurred on soft ground or sloped land that has been buried in fields, rivers or sea.

  When building a house on soft ground, it is clear that conventional ground reinforcement measures by surface improvement of land cannot cope with ground depression, uplift or liquefaction caused by earthquakes of a certain scale or larger. It has become.

  As reinforced soil wall construction methods for landslides caused by earthquakes or heavy rains on slopes, a number of anchor type reinforced soil walls, tail armure construction methods, geotextile reinforcement walls (see, for example, Patent Document 1), and the like are known.

  And when the land of a detached house is soft ground that does not meet the prescribed criteria, not only surface improvement work (such as soil replacement) of the land, but also low-cost reinforced soil pile construction is performed As an example of such a simple reinforced soil pile method, geotextile (high-textured) is obtained by mixing expansive material with cement-based (calcium or lime-based) water absorption into cutting soil, waste glass or demolition glass, etc. There is known a technique in which a water-permeable sheet made of molecular chemical fiber material) is tightly wound in a cylindrical shape and used as a reinforcing pile (for example, see Patent Document 2).

JP 2010-90592 A JP-A-7-305334

  However, N value (value indicating the strength of the ground required in the standard penetration test, using a boring hole, the tip of the rod rod (steel rod) is 5.1 cm in diameter and 81 cm in length. A sample with a hollow cylindrical sampler was dropped freely from a height of 75 centimeters with a hammer weighing 63.5 kilograms and the number of impacts required for penetration per 30 centimeters of penetration depth was 4 or less. In the case of a soft ground, a highly rigid pile or reinforced pile construction method is dangerous because it is likely to break due to a deformation strain force applied to the ground by an earthquake. In particular, when the ground intermediate layer has an N value of 4 or less, the risk of failure is particularly high. Therefore, in the case of the ground of a detached house, it has a flexible structure with respect to deformation strains up to a certain degree, so that it can withstand deformation strains exceeding a predetermined level without being cramped while following the deformation of the ground. It must have a flexible structure.

  In addition, in the case of the ground of a detached house, in order to prevent or reduce the liquefaction of the ground due to earthquake motion, if the groundwater level rises and is pushed up into the ground, a drainage drain that allows water to pass through Must have function.

  In addition, hexavalent chromium contained in the cement-based solidifying agent has a risk of leaching into the land depending on the soil quality, and contaminates the ground soil.

  However, in the method for producing the reinforced soil pile and the reinforced soil pile described in Patent Document 2, the tubular geotextile filling member is made of ground excavated soil, glass waste material, demolition glass, etc. Due to the construction to expand the volume, the drainage is poor and it does not have a function as a drainage drain.

  In view of the above, it is an object of the present invention to provide a ground strengthening method and a ground strengthening system which have a deformable structure capable of following the deformation of the ground as well as having a strong support to the ground and also have a function of a drainage drain. .

In order to solve the above-mentioned problems, a ground reinforcement system according to the present invention is a ground reinforcement system that reinforces a ground on which a building is constructed, and a water-permeable sheet having a mesh composed of crushed stone made of a polymer fiber material. A columnar body constrained in a columnar shape, and a spherical part at the lower end of the columnar body, the crushed stone being compacted and the diameter of which is larger than the diameter of the columnar part of the columnar body, The load of the building is supported by the peripheral frictional force of the columnar body and the tip support force of the spherical portion .

  Further, a permeation layer is provided between the columnar body and the foundation of the building.

A ground strengthening method according to the present invention is a ground strengthening method for strengthening a ground on which a building is constructed, and includes a first step of excavating the ground and forming a plurality of excavated holes at intervals in the horizontal direction. And a second step of installing a cylindrical water-permeable sheet having a mesh made of a polymer fiber material in each of the excavation holes, and after putting crushed stone under the water-permeable sheet, a third step of the compacting rod to form a spherical section compacting the crushed stone inserted into the hollow portion of the water flow sheet, the charged crushed stones of medium filling the hollow portion of the water flow sheet the compacting rod possess a fourth step of producing a columnar body compacted, and the spherical portion is characterized by configuring overhangs larger sphere than the diameter of the columnar portion.

  Then, the first step is performed by excavating the excavation hole by rotating the casing containing the water flow sheet by a rotary press-fitting machine, and the second step is performed after the excavation. When the casing is pulled out from the ground, it is constructed by opening the bottom of the casing and pulling out the water-permeable sheet. Furthermore, the surface of the casing is characterized in that a projection for compacting the excavated soil to the wall surface of the excavated hole is formed.

  And in the said 3rd process, whenever the said crushed stone reaches predetermined | prescribed height, it is characterized by compacting with the said rolling rod.

As described above , according to the present invention , the columnar body is secured with sufficient strength by the shear strength of the crushed stone and the tensile strength of the water-permeable sheet composed of the polymer fiber material, and thus the load of the building is increased. In order to support by the peripheral frictional force of the columnar body and the tip support force of the spherical portion, a ground strengthening system and a ground strengthening method ensuring sufficient strength are provided. And since the columnar body which consists of a combination of a crushed stone and a water-permeable sheet | seat has a soft structure, it also has the softness | flexibility which follows the deformation | transformation of a ground. Furthermore, since both the columnar body and the spherical portion are made of crushed stone, it can function as a drain for drainage and can prevent liquefaction of the ground.

The explanatory view explaining the ground reinforcement system concerning the present invention is shown. The explanatory view explaining the arrangement composition of the columnar object in the ground reinforcement system concerning the present invention is shown. Explanatory drawing explaining the structure of a columnar body is shown. Explanatory drawing explaining the process of the ground reinforcement method which concerns on this invention is shown. Explanatory drawing explaining the structure of the casing of a rotary press-fitting machine in a cross section is shown.

  The structure of the ground reinforcement system according to the present invention is shown in FIG. The ground 1 supports a building (not shown) and its foundation 2, and in order to strengthen the supporting force by the ground 1, the ground 1 has a vertical height of 3.5 m to 5.m as shown in FIG. 2. A plurality of columnar bodies 3 having an elongated shape of about 5 m are embedded at intervals in the horizontal and vertical directions and at intervals according to the softness of the ground 1. The columnar body 3 is configured by constraining the crushed stone 6 with a water-permeable sheet 4 having a mesh made of a polymer fiber material, and the water-permeable sheet 4 has a mesh 5 from which a part of the crushed stone 6 protrudes. . The particle size of the crushed stone 6 is preferably about 20 mm to 60 mm. A permeation layer 8 is provided between the foundation 2 and the upper end surface of the columnar body 3. The columnar body 3 has a spherical portion 3A according to the strength of the ground 1 but will be apparent later.

  The water-permeable sheet 4 is composed of fibers of a polymer material having a high tensile strength used for civil engineering. Examples of the material include a geotextile. Geotextiles include geotextiles in a narrow sense, geogrids, geonets, and others. In addition, geotextiles in this narrow sense include woven fabrics (geo-wovens), non-woven fabrics (geonon-wovens), and knitted fabrics (geo-nits). Among these, in the field of ground reinforcement, a geogrid having particularly excellent tensile resistance and creep resistance is preferable.

  As shown in detail in FIG. 3, the water-permeable sheet 4 that restrains the crushed stone 6 has a cylindrical shape, and in the columnar body 3 that is used in the soft ground whose N value of the ground 1 is 4 or less, the spherical portion 3A. Form. By forming such a spherical portion 3 </ b> A projecting in a spherical shape larger than the columnar portion at the lower end of the columnar body 3, the tip support force of the columnar body 3 can be increased.

  Further, depending on the properties of the ground 1, the spherical portion 3 </ b> A may need to be solidified using a solidifying material. In this case, it is preferable to select a solidifying material in consideration of hexavalent chromium, although it is only the portion of the spherical portion 3A limited in the entire columnar body 3.

Further, when the crushed stone 6 is restrained, the crushed stone 6 of the spherical portion 3A is compacted by being compacted by a pressure of about 500 kN / m ³ , and the crushed stone packed in the water flow sheet 4 is 0 in the longitudinal direction. Each time it is filled at a height of 0.5 m, it is rolled at the same pressure and compacted. Although the crushed stone 6 is a crushed stone with a large shear strength, the shear strength can be further increased by further compaction. Thus, the crushed stone 6 with high shear strength and the binding force of the water-permeable sheet 4 with high tensile strength combine, and the columnar body 3 has high strength against the load from the building from above.

  Further, the columnar body 3 may be partially injected with cement milk in advance in order to prevent pore wall destruction due to water pressure and earth pressure applied to the side surface from the outside.

  When the load of the foundation 2 and the building constructed on the ground 1 is transmitted, the columnar body 3 having such a structure is supported by the spherical portion 3A and peripheral surface friction. For this reason, since the crushed stone 6 packed in the middle has a high shear strength, the columnar body 3 tries to counter this load by the shear force of the crushed stone 6 by externally restraining and reinforcing the columnar body 3 from the outside with the water-permeable sheet 4. That is, the crushed stone 6 tends to protrude laterally by receiving a compressive force in the vertical direction from the load from above and the tip supporting force of the spherical portion 3A from below. However, at this time, the extension of the crushed stone 6 is suppressed by the tensile strength of the water-permeable sheet 4 that restrains the crushed stone 6 packed in the middle, and the columnar body 3 increases the internal pressure by suppressing its shape change, thereby increasing the shear strength. The ground 1 can be reliably supported against the load from above.

  In the case of a relatively hard ground whose N value is sufficiently higher than 4, the spherical portion 3A does not have to be particularly formed on the columnar body 3, and in this case, the columnar body 3 is formed at the lower end portion because the ground is strong. The load of the building can be received, and sufficient rigidity as the columnar body 3 can be secured by the expansion force of the crushed stone 6 due to the load and the tensile strength of the water-permeable sheet 4.

  Further, since a part of the crushed stone 6 protrudes from the mesh 5 on the surface of the columnar body 3 by the water flow sheet 4, the frictional force between the columnar body 3 and the ground 1 is increased, and the settlement of the columnar body 3 is also prevented. Has been.

  And since the columnar body 3 is a flexible structure of the structure which restrains the individual crushed stone 6 with the water sheet 4, it has the flexibility which can follow the deformation | transformation of the ground 1, and the columnar body Even if a strong force is applied to one of the three places, the force does not break in order to spread this force throughout, and it has excellent impact resistance. Therefore, when receiving the force of seismic motion, it is deformed integrally with the ground 1 so that it is not broken, and support for the load from above can be maintained.

  However, for example, when the content member of the water-permeable sheet 4 is configured by being hardened with an expansion material or a solidifying material, since it does not have a flexible structure, the ground 1 against the load of the building is destroyed depending on the strength of the earthquake motion. There is a risk that it will lose the supporting ability of the building at once, causing collapse of the building and landslide. As described above, the spherical portion 3A of the columnar body 3 may be hardened with a solidifying material depending on the properties of the ground 1, but since it is substantially spherical, it is not broken.

  Similarly, when the groundwater pressure increases due to seismic motion or the like, the groundwater from the side surface direction of the columnar body 3 (in the direction of arrow a in FIG. 1) becomes a crushed drain and drains to the permeable layer in the ground 1 or Since groundwater is drained out of the ground 1 that is reinforced by permeating the groundwater in the flow direction, liquefaction of the ground 1 is prevented.

  Next, the ground reinforcement method combining such a crushed stone and a water flow sheet will be described.

  As shown in part (A) of FIG. 4, first, excavation is performed while rotating the casing 11 with high torque into the ground 1 located directly below the foundation 2 of the building to be built by rotating the casing 11 with high torque. .

  As shown in the sectional view of FIG. 5, the casing 11 is provided with three protrusions 12 having a taper in the circumferential direction on the surface thereof along the longitudinal direction. Accordingly, when the casing 11 rotates to perform excavation, the protrusion 12 presses and presses the waste soil against the wall surface of the excavation hole 15 by the rotation, thereby solidifying the wall surface of the excavation hole 15. Thereby, the strength of the wall surface of the excavation hole 15 can be increased to prevent the wall surface from collapsing. Further, the waste soil is pressed downward and pressed by the rotation of the casing 11. Therefore, waste soil from excavation is not discharged to the ground surface.

  The excavation hole 15 for embedding the columnar body 3 in the ground 1 is formed by excavating from 3.5 m to 5.5 m using a casing 11 having a diameter of 300φ, for example. The diameter D and the depth H of the excavation hole 15 are determined by the weight of the building to be built and the properties of the ground 1.

  The casing 11 is provided with an opening / closing mechanism 12 at the tip, and the rotary presser 10 excavates with the cylindrical water-permeable sheet 4 stored in the casing 11 with the opening / closing mechanism 12 closed.

  Next, as shown in part (B) of FIG. 4, the opening / closing mechanism 12 of the casing 11 is opened to leave the water-permeable sheet 4 and the casing 11 is pulled out from the ground 1. Or it may be disposable.

And although the crushed stone 6 is thrown into the cylindrical water-permeable sheet 4 and the columnar body 3 is produced, before producing the columnar body 3 which has the spherical part 3A, it is to (C) part (side cross section) of FIG. As shown, first, an amount of crushed stone 6 for forming the spherical portion 3 </ b> A is introduced into the bottom of the excavation hole 15. The rolling pressure rolling the crushed stone 6 which supplied with intensifier by compaction, but rolling intensifier is rolling in the range from 500 kN / ^{m 3} Insert the compacting rod 13 of 267.4φ the drilling hole 15 to 1000 kN / ^{m 3} A spherical portion 3A is produced by applying pressure and compacting.

  Next, as shown in FIG. 4D (side cross section), the crushed stone 6 packed in the water-permeable sheet 4 is put into the excavation hole 15, and is stacked about 0.5 m from the spherical portion 3A. Then, the rolling rod 13 is inserted again, and the same rolling force as described above is applied and tightened.

  And as shown to the (E) part (side cross section) of FIG. 4, the columnar body 3 becomes the inside of the ground 1 by repeating the injection | throwing-in of the stuffed crushed stone, and the compaction by the rolling rod 13 for every 0.5 m interval. The ground strengthening work is completed.

  The above ground reinforcement system and ground reinforcement method according to the present invention ensure the strength to support the ground 1 against the load of the building by the combination of the crushed stone 6 and the water flow sheet 4, while seismic motion from the flexible structure. In order to follow the ground 1 and be deformed by receiving the force of the above, it will not break, and the strength is integrated with the ground 1. And rainwater drains from the ground 1 as a crushed stone drain, and strengthens the ground 1 from both a ground support surface and a drainage surface.

  The effectiveness of strengthening the ground using crushed stone in this way is proved by, for example, the effect when crushed stone is laid under sleepers on railroad tracks. In other words, by supporting the sleepers that fix the rails through which the train passes with crushed stone, the load of the train concentrated in one place can be dispersed and received by crushed stone, and the rainwater can be quickly retained by crushed stone. It has been demonstrated that it can be drained to prevent flooding of the track.

  Based on the same principle, the ground reinforcement system and the ground reinforcement method according to the present invention receive the load of the building and the force from the side of the ground 1 with the crushed stone 6 restrained by the water flow sheet 4. Since the accumulated water in the ground 1 is drained through the crushed stone 6, the ground subsidence and landslide can be suppressed effectively.

  The present invention provides a ground reinforcement system and a ground strengthening method for strengthening a ground on which a building stands, and has industrial applicability.

DESCRIPTION OF SYMBOLS 1 Ground 2 Foundation 3 Columnar 3A Spherical part 4 Water flow sheet 5 Mesh 6 Crushed stone 10 Penetration layer 10 Rotary press-fit machine 11 Casing 12 Protrusion 13 Rolling rod 15 Excavation hole

Claims (6)

A ground strengthening system that strengthens the ground on which a building is built,
A columnar body formed by restrained compacted at a predetermined pressure above the cylindrical shape by water-permeable sheet having a crushed stone constituted by polymeric fibrous material networks,
A spherical portion at the lower end of the columnar body, the crushed stone being compacted and the diameter of which is larger than the diameter of the columnar portion of the columnar body;
The ground strengthening system is characterized in that the load of the building is supported by the peripheral frictional force of the columnar body and the tip support force of the spherical portion . The ground reinforcement system according to claim 1 , wherein a permeation layer is provided between the columnar body and the foundation of the building. A ground strengthening method for strengthening a ground on which a building is constructed,
A first step of excavating the ground to form a plurality of excavated holes spaced horizontally from each other;
A second step of installing a cylindrical water-permeable sheet having a mesh composed of a polymer fiber material in each of the excavation holes;
After throwing crushed stone below the water flow sheet, a third step of forming a spherical portion by inserting a rolling rod of a compactor into the hollow portion of the water flow sheet and compacting the crushed stone;
A fourth step in which a crushed stone filled in the hollow portion of the water flow sheet is charged and compacted by the rolling rod to produce a columnar body;
It has a, ground reinforcement wherein said spherical portion is characterized in that it constitutes overhangs larger sphere than the diameter of the columnar portion. The first step is performed by excavating the excavation hole by rotating the casing containing the water flow sheet with a rotary press-fitting machine,
In the second step, when the casing is pulled out from the ground after the excavation, it is constructed by opening the bottom of the casing and pulling out the water-permeable sheet.
The ground strengthening method according to claim 3 , wherein: 4. The ground strengthening method according to claim 3 , wherein a projection for compacting the excavated soil on the wall surface of the excavated hole is formed on the surface of the casing. The ground strengthening method according to claim 3 , wherein, in the fourth step, the crushed stone is compacted by the rolling rod every time the crushed stone reaches a predetermined height.

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