JP2010001718A - Shallow ground improving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shallow ground improving method for alleviating sinkage of an upper building and input vibrations to the upper building, reducing the construction cost compared with a conventional art, and improving an effect of preventing deformation of an improved layer. <P>SOLUTION: In the shallow ground improving method, an integrated improved ground is formed by laying a sheet of geotextile on a leveled ground surface, placing dry mixed mortar, and bonding foamed resin plates to each other. When the ground is particularly soft, more stable improved ground is formed by injecting a chemical liquid or laying a plurality of geotextile sheets. Further, when improvement in vibration control performance is required, a vibration control material is arranged between the foamed resin plates. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to ground improvement for supporting an upper load, reducing subsidence, and reducing input of ground vibration to an upper building, particularly when a building is constructed on soft ground.

A method of constructing a lower foundation structure by laying foamed resin is known when a building is constructed on soft ground or when reinforcing the ground of the lower part of an existing building. This construction method is shown in Patent Documents 1 to 3.
Summarizing the construction method of Patent Document 1, a drainage material and a fixed foamed resin material are laid at the bottom of a building foundation to construct a foundation structure that is excellent in earthquake resistance and easy to construct.
In summary, the construction method of Patent Document 2 excavates and discharges the lower part of the foundation of an existing building and installs a foamed resin board to prevent traffic vibrations, earthquakes, and land subsidence.
Furthermore, the construction method disclosed in Patent Document 3 is a construction method in which the ground is rooted, sand is directly spread, foamed resin blocks are arranged on the sandbed, and a building foundation is constructed on the foamed resin block. The effect is said to improve the earthquake resistance of the upper building and prevent the settlement of the supporting ground.
Japanese Patent Laid-Open No. 9-273160 Japanese Patent Laid-Open No. 11-256596 JP 2000-154550 A

Among the background arts, the technique according to Patent Document 1 has a problem that the drainage material is easily clogged, a predetermined drainage capacity cannot be obtained, and an adverse effect due to groundwater is caused on the upper building.
Moreover, about the technique which concerns on patent document 2, in order to excavate the lower part of the foundation of an existing building, it induces non-uniform subsidence, and the familiarity with the installed foam resin board and an upper building is bad, and upper part There is a problem of adversely affecting the structural safety of the building.
Furthermore, regarding the technique according to Patent Document 3, the method of laying the foamed resin block is simply placing the foamed resin block after laying the sand on the bottom surface of the rooting, and the sand flows out by groundwater, or Separation of the foamed resin blocks often causes uneven settlement in the upper building, and further, there is a problem that the horizontal accuracy of the foamed resin finished surface is poor and adversely affects the structure of the upper building. Furthermore, with regard to the vibration proof performance, there is a problem that it is difficult to absorb or reflect low frequency vibration.

The present invention is for solving the above-mentioned problems, and clogging of an underground drainage channel which has been a problem in Patent Document 1, adverse effects on structural safety of an upper building which has been a problem in Patent Document 2, Patent Document 3 solves the problem of the uneven settlement of the upper building, which has become a problem in 3, and the deterioration of the vibration-proof performance in the low-frequency region. And providing improved ground with seismic control effect.

A single layer of geotextile is laid on the bottom of the rooting, crushed stone is laid on the geotextile, empty paste mortar is laid on the crushed stone, and multiple layers of foamed resin boards are laid on the empty paste mortar. The foamed resin boards are bonded and fixed to each other with an adhesive, and the foamed resin boards are laminated in a plurality of layers so that the adhesive portions do not overlap with each other, and the geotextile matches the shape of the bottom of the rooting. It is characterized by being sewn together.

In addition, when it is required to have a more stable ground, a plurality of layers of geotextiles are laid in the construction method, and crushed stone / burial soil, cohesive soil, or quick lime is placed between the geotextiles. It is characterized by interspersed viscous soil.

In the case where the lower ground is particularly soft, the lower ground is reinforced by injecting a chemical solution for solidification into the lower part of the geotextile laying portion.
In this case, the layer thickness of the original ground layer interposed between the geotextile and the chemical solution injection part is within 2 m, and the chemical solution injected into the chemical solution injection is a water glass or cement material. .

When vibration-proof performance is particularly required, a damping member is laid between the upper and lower layers of the foamed resin plate. The damping member is a reinforced concrete plate, a damping rubber material, a flexible board, or a nonwoven fabric.

Effects of the present invention

When the lower ground of the building is rooted, the specific gravity of the foamed resin board is extremely small, so the increase in underground stress in the lower ground on the bottom of the rooting is reduced by the weight of the soil removed.
As a result, the amount of immediate settlement and consolidation settlement of the lower ground of the building after construction is greatly reduced. As a result, it is effective in reducing the settlement and uneven settlement of the entire building.

Since geotextiles generate frictional force with the surrounding soil, frictional force is generated with the soil on the bottom of the improved layer and the soil on the side surface. Therefore, upward frictional stress is applied to the improved layer due to the so-called hammock effect. As a result, it is effective in reducing the settlement of buildings.
In addition, since the geotextile is sewn in accordance with the shape of the bottoming bottom, the geotextile has a shape that wraps the crushed stone at the top, so that the crushed stone will dissipate in soft soil. There is an effect to prevent.

By laying crushed stones on the geotextile, it will serve as a channel in the groundwater ground. Specifically, if spring water from the ground or rainwater from the ground penetrates into the ground, it can flow freely in the crushed stone, staying in the lower part of the improved ground, and improving the adverse effects of water pressure Without giving to the ground, it will flow out of the improved ground. As a result, it has the effect of preventing adverse effects on the improved layer due to groundwater flow.

By laying the empty mortar, there is an effect of improving the adhesion between the upper foamed resin plate and the lower crushed stone and improving the integrity of the entire improved layer. That is, the empty mortar absorbs moisture immediately after laying and starts to harden. At that time, it has an action of being bonded to and integrated with the lowermost foamed resin plate and the lower crushed stone. Therefore, at the end of curing, the upper foamed resin plate, the empty mortar, and the lower crushed stone have an integrated strength as a whole. The empty mortar can ensure a good horizontal accuracy by finishing it to a smooth surface with a gold iron or the like during construction. For this reason, the horizontal accuracy of the foamed resin plate laid on the upper part of the empty paste mortar is improved. Also, it may be discarded concrete instead of empty mortar.

The foamed resin plate is very lightweight but has high compressive strength, and the vertical stress of the upper building is dispersed inside the foamed resin plate, which has the effect of reducing the increase in stress due to the construction of the upper building.
In addition, the foamed resin plates are firmly bonded with an adhesive, and the adhesive surfaces are arranged so that the joints of the foamed resin plates are misplaced. It has the effect of increasing the strength of the entire improved layer and the effect of preventing the subsidence of the improved ground.

Foamed resin board has a wide elastic region, so it becomes a kind of winkler spring, acts as a rocking spring for the upper building during an earthquake, prolongs the natural vibration period of the upper building, and inputs seismic energy to the upper building. Has the effect of reducing. This is particularly effective when the upper building has high rigidity and a large tower ratio.

The backfill layer around the foamed resin plate protects the foamed resin plate from external ultraviolet rays, and is effective in preventing deterioration of the entire improved layer and stabilizing the shape.

The layer improved by the ground solidifying chemical solution has an effect of injecting the chemical solution into the lower ground and further improving the supporting force of the improved ground when the lower ground is particularly soft. That is, if the lower ground is particularly soft, it is expected that ground deformation will occur due to lateral flow, but in preparation for lateral flow, by injecting water glass or cement-based chemicals, This improves the adhesiveness and water-stopping property and prevents lateral flow.
For this reason, as a result, the supporting force of the improved ground is improved and the effect of suppressing the settlement of the upper building is obtained.

The damping member is used particularly when a damping effect is required. When a damping rubber material, flexible board, or non-woven fabric is used as the damping member, the damping member and the foamed resin plate each absorb vibrations in different frequency bands, and the improved body as a whole absorbs vibration. To improve. Further, when a reinforced concrete plate is used as the vibration control member, the vibration impedance ratio between the reinforced concrete plate and the polystyrene foam is large, so that the efficiency of reflection of vibration is improved by the wave reflection theory. By this reflection effect, the wave absorption effect in the high frequency band of the polystyrene foam, and the mass effect of the reinforced concrete board, the vibration is efficiently absorbed or reflected, and the vibration input to the upper building is reduced.

By installing viscous soil mixed with quick lime between the longitudinal directions of geotextiles, solidifying the viscous soil and constructing multiple layers of layers, so-called "plate construction" principle, stable improvement over a long period of time It becomes the ground. At this time, it is preferable to use a non-woven material having high water permeability for the following geo-textile for securing a groundwater channel.

When buried in the vertical direction between geotextiles, the vertical direction of the upper building depends on the friction between the geotextile and the buried soil and the tensile strength of the geotextile itself. It becomes a stable improved ground to support the stress of At this time, it is preferable to secure an appropriate fixing length at the end of the geotextile, or to apply an area to the end of the geotextile.

Examples of the present invention will be described below.

FIG. 1 shows an example in which the present construction method is applied to a solid foundation.
First, the ground is cut down to a predetermined depth. The bottom cutting bottom 1 is sufficiently rolled to ensure horizontal accuracy, and the geotextile 2 is laid thereon. The geotextile 2 is integrally sewn in accordance with the shape of the bottoming bottom surface 1. The crushed stone 3 is laid on this and fully rolled. An empty mortar 4 is laid on the crushed stone 3. The top end surface of the empty mortar 4 is accurately leveled, and a gold trowel finish is desirable.
On the empty mortar 4, a first layer of foamed resin plate 5A is laid. When laying, it will be allocated based on a predetermined construction drawing. On the first layer, the second layer of the foamed resin plate 5B is applied and adhered between the lower layer of the foamed resin plate 5A and laid. At this time, it is preferable that the upper and lower layers are fastened by a skewer between the foamed resin plates 5A and 5B. The upper and lower layers are allocated so that the joints are so-called misplaced in a plane. Thereafter, the foamed resin plate 5C and the like are sequentially laid up to a predetermined layer in the same procedure, and finally the periphery of the foamed resin plate is backfilled by the backfill layer 7 to complete the improved layer as a whole.
The function and effect of each component are as follows. The geotextile 2 has an effect of insulating the original ground and the improved layer and reducing the uneven settlement of the improved layer by the frictional force with the original ground. The crushed stone 2 becomes a channel for groundwater, and prevents the improvement layer from being deformed due to the flow of groundwater or water pressure. The empty mortar 4 has an effect of bonding the upper foamed resin plate 5 and the lower crushed stone 3 and structurally integrating the entire improved layer. The foamed resin plate 5 has an effect of uniformly and dispersing the vertical load of the upper building and transmitting it to the lower ground.
Further, there is an effect of reducing an increase in underground stress in the lower ground for the weight of the soil discharged by the foamed resin plate 5, thereby reducing the uneven settlement of the upper building. Further, by adhering the foamed resin plates to each other with an adhesive, the improvement layer has an integral structure as a whole, and the effect of reducing the uneven settlement is improved.

FIG. 2 shows an example in which a plurality of geotextiles are laid.
Excavation up to the bottom 1 is the same as in the first embodiment. After laying the geotextile 2A (first layer), the clay 8 is laid on the geotextile 2A, and sufficient rolling is performed. In this case, the geotextiles 2A and 2B in contact with the viscous soil are preferably made of non-woven cloth from the viewpoint of ensuring water permeability.
The cohesive soil 8 is fully rolled and leveled, and then the geotextile 2B (second layer) is laid. The construction procedure is the same as in the case of Geotextile 2A. In some cases, it is also preferable to construct a similar geotextile and cohesive soil layer in a sandwich. Further, the crushed stone 3 is laid between the geotextile uppermost layer 2C and the foamed resin plate 5A on the top. This ensures the flow of groundwater. The construction procedure after the crushed stone 3 is the same as that in the first embodiment.
Of the actions and effects of the constituent elements, the differences from the technique according to the first embodiment are as follows. The geotextile 2A and the cohesive soil 8 have an integrated structure due to a large frictional force, and are a good improvement layer as a building support layer. Further, the geotextile 2C and the surrounding crushed stones 3A and 3B have an effect of suppressing deformation of the improved layer due to the groundwater flow and water pressure.

FIG. 3 shows an example in which the present construction method is applied to the fabric foundation 12. The construction method is the same as the procedure shown in FIG. 1. In this case, it is preferable to use the foam resin plate 5A at the lower part of the fabric foundation having a high compressive strength because the cloth foundation ground pressure is generally large. .
The function and effect of each component are the same as in the technique according to the first embodiment.

FIG. 4 shows an example in which the present construction method is applied to a particularly soft ground.
Before rooting the ground, the chemical solution is injected into the chemical solution injection unit 10 so as not to deviate from a predetermined depth and a range on a horizontal plane. The chemical solution is water glass or cement.
After chemical injection, root cutting is performed to a predetermined depth. Although the original ground layer 9 has a layer thickness of 2 m or less, the raw textile layer may be omitted and the geotextile 2 may be in contact with the chemical injection part 10 in some cases. The construction procedure after root cutting is the same as that in the first to third embodiments.
The differences between the functions and effects of the constituent elements from the technique according to the first embodiment are as follows. The chemical injection unit 10 has an effect of suppressing the lateral flow of the ground and preventing liquefaction during an earthquake in some cases. The raw ground layer 9 is interposed between the geotextile 2 and the chemical solution injection unit 10 and has an effect of dispersing the vertical stress of the upper building and transmitting it to the chemical solution injection unit 10.

FIG. 5 shows an example in which the present construction method is applied in order to improve the vibration isolation.
The construction from the root cutting to the first layer of the foamed resin plate 5A is the same as in FIG. A damping member is laid on the first layer of the foamed resin plate.
The damping member 11A is bonded onto the foamed resin plate 5A. At this time, when a reinforced concrete plate is used as the vibration control member, the reinforcing bar is placed on the upper concrete.
Further, the foamed resin plate 5B is bonded onto the vibration damping member 11A, and thereafter, the vibration damping material and the foamed resin plate are sequentially constructed in a sandwich shape, and the foamed resin plate 5C is constructed as the uppermost layer.
Subsequent construction procedures are the same as those in the first embodiment.
The differences between the functions and effects of the constituent elements from the technique according to the first embodiment are as follows. The damping member 11 has an effect of effectively absorbing or reflecting vibrations having a frequency that is difficult to be absorbed or reflected by the foamed resin plate 5.

FIG. 1 shows an example in which a single-layer geotextile is applied to a solid foundation and this method is applied. FIG. 2 shows an example in which a multi-layer geotextile is constructed on a solid foundation and the present construction method is applied. FIG. 3 shows an example in which the present construction method is applied to a fabric foundation. FIG. 4 shows an example in which a chemical solution injection work is performed when the present construction method is applied to a particularly soft ground. FIG. 5 shows an example in which a vibration control material is used in the present construction method in order to improve the vibration resistance of the ground.

Explanation of symbols

1. Bottom of root cutting 1. Geotextile 2. Crushed stone 4. Empty mortar 5. Foamed resin plate 6. Building foundation (solid foundation)
7). Backfill layer 8. Cohesive soil Original ground layer10. 10. Chemical solution injection part Damping member 12. Building foundation (cloth foundation)

Claims (5)

A single layer of geotextile is laid on the bottom of the root cutting, crushed stone is laid on the geotextile, empty mortar or discarded concrete is laid on the crushed stone, and foamed resin on the empty mortar or discarded concrete A plurality of plates are laid, and the foamed resin plates are bonded and fixed to each other with an adhesive, and the vertical surfaces of the foamed resin plates are arranged in a plurality of layers so that the adhesive portions do not overlap each other, the geotextile Is a shallow ground improvement method characterized by being integrally sewn according to the shape of the bottom of the bottoming. In the shallow ground improvement method according to claim 1, a plurality of geotextiles are laid, and between the geotextiles, clay soil, viscous soil, or viscous soil mixed with quick lime is interposed. A shallow ground improvement method characterized by this. The shallow ground improvement construction method of the shallow ground improvement construction method according to claim 1 or 2, further comprising a chemical injection portion into which a ground solidification chemical solution is injected at a lower portion of the geotextile laying portion. . The shallow ground improvement method according to claim 3, wherein a raw ground layer is interposed between the geotextile and the chemical solution injection part, and the layer thickness is within 2 m, and is injected into the chemical solution injection part. A shallow ground improvement method characterized in that the chemical solution to be used is a water glass-based or cement-based material. In the shallow ground improvement method according to claim 1 to claim 4, a damping member is laid between the upper and lower layers of the foamed resin plate, and the damping member includes a reinforced concrete plate, a damping rubber material, A shallow ground improvement method characterized by being made of flexible board or non-woven fabric.

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