JP5060579B2 - Ground improvement direct foundation method - Google Patents

Description

  The present invention relates to a ground improvement direct foundation method in which solidified material is mixed with soft ground to improve the ground, and a solid foundation such as a solid foundation is built on the ground. Specifically, when the improved improved ground is subsidized However, it is related to the improvement of ground improvement direct foundation method that can adjust unevenness.

  Conventionally, buildings with relatively small weight per building area, such as wooden houses, are soft ground (generally, ground with an N value of 4 or less for organic soil or clay soil, and an N value of 10 or less for sandy soil) In the case of construction on the same), the surface layer of the soft ground is mixed with the soil of the ground to improve the cement-based or lime-based solidified material (also referred to as ground improvement material or ground stabilization material). Improving the entire surface or the shape of a grid to improve the ground strength of the ground to make it a supporting ground, and on top of that a direct foundation such as a solid foundation (solid foundation, cloth foundation, independent foundation, etc. penetrates the surface layer ground below it) There is known a ground improvement direct foundation method for constructing a foundation that directly constructs the foundation on the surface ground without providing a support pile that reaches the strong support layer in the ground (the same applies hereinafter) (for example, Patent Document 1) ).

  In addition, in such a ground improvement direct foundation method, the foundation is constructed by combining the improved ground with the foundation and the foundation so that the building will not be damaged even if the soft ground subsides. Various ground improvement direct foundation methods with increased part rigidity have also been proposed (Patent Documents 2 to 4, etc.).

  For example, in Patent Document 2, in a solid foundation method for a wooden house or a low-rise house, the ground is improved by mixing and solidifying material mixed with vinylon-based or other reinforcing fibers and soil to improve the ground (stable Material), excavating a small groove for ribs on the upper surface of this improved wall and arranging the bars, and then building a solid foundation on it to integrate the rib and the solid foundation so that the solid foundation A solid foundation method for preventing settlement is disclosed.

  In Patent Document 3, the foundation is constructed by pointing the connecting bars to the improved ground (improved wall) subjected to ground improvement, constructing the foundation directly on it, and integrating the foundation slab and the improved ground directly. A method for constructing an integrated structure of a ground and a foundation with increased rigidity is disclosed.

  Further, in Patent Document 4, the soft ground is divided into several layers and deepened as it goes to the outer peripheral part of the building to form a multi-layered stepped ground, and a mesh body (mesh bar arrangement) is formed thereon. In addition to laying and arranging dowels so as to penetrate this mesh body, concrete is cast to build a solid foundation, and the improved ground and the solid foundation are integrated to suppress uneven settlement of the foundation. And the ground improvement solid foundation method which can improve the bearing capacity of the whole foundation is disclosed.

  However, the ground improvement direct foundation method described in Patent Documents 2 to 4 is to improve the rigidity of the foundation by integrating the improved ground and the foundation. ) It is not envisaged that the case itself will sink. In other words, although the subsidence can be suppressed by integrating the improved ground and the direct foundation, in the soft ground, the subsidence of the ground below the improved ground may occur due to the influence of an earthquake or groundwater. In that case, even if the collapse of the building is avoided due to the integration of the improved ground and the direct foundation, the problem remains that the improved ground and the foundation itself are tilted and the building can no longer be used. .

Japanese Patent Laid-Open No. 06-313314 Japanese Patent Laid-Open No. 08-232273 JP-A-11-269894 Japanese Patent No. 3608568

  Therefore, the present invention solves the above-mentioned problems of the prior art, prevents the horizontal displacement of the improved wall and the direct foundation, and increases the flexural rigidity of the direct foundation. However, the purpose is to provide a ground improvement direct foundation method that can continue to use the building by adjusting the unevenness by jacking up.

  In order to solve the above-mentioned problem, the invention according to claim 1 is to improve the ground by mixing the solidified material in the soft ground and stirring and then rolling to form an improved wall in a grid shape in plan view. In the ground improved direct foundation method for constructing a foundation directly on the improved wall, a step of installing a fastening member fixed to the direct foundation to fasten the improved wall and the direct foundation; and And a step of installing a protective mold for partitioning the tightly fitting portion so as not to be buried in the concrete.

  The invention according to claim 2 is the ground improvement direct foundation method according to claim 1, wherein a step of constructing a column of soil cement by mixing and stirring while discharging slurry containing water and cement to the soft ground is provided. It is characterized by having.

  The invention according to claim 3 is the ground improved direct foundation method according to claim 1 or 2, wherein the fastening member is installed in the vicinity of both ends of each street except the outer periphery of the improved wall. .

  According to a fourth aspect of the present invention, in the ground improved direct foundation method according to any one of the first to third aspects, the improved wall is rolled into a plurality of layers at a predetermined depth, and the fastening member is The lower wall of the improved wall is rolled in the excavation groove for the improved wall after rolling.

  According to a fifth aspect of the present invention, in the ground improved direct foundation method according to the fourth aspect of the present invention, the fastening member includes a U bolt having a thread formed at both ends, and substantially horizontally at both ends of the U bolt. A level material that is bridged, the center portion is fixed directly to the foundation, and both end portions are arranged in the protective mold, and the both ends of the level material are tightened by screwing with the thread of the U bolt. And a level adjusting nut to be fixed.

  The invention according to claim 6 is the ground improved direct foundation method according to any one of claims 1 to 5, wherein the protective form is a square sleeve that is openable and closable with a protective cap fitted into the upper part thereof. In this case, the protective mold is used as a driving mold without removing it.

  The present invention is as described above, and according to the invention described in claim 1, the ground is improved by rolling and pressing after mixing and stirring the solidified material in the soft ground, and the shape of the grid in plan view. In the ground improvement direct foundation method for forming a foundation directly on the improvement wall, and installing a fastening member that is fixed to the direct foundation and fastens the improvement wall and the direct foundation. , And a step of installing a protective mold that partitions the tightening portion of the tightening member so as not to be buried in the concrete. By preventing this, the improved wall and the foundation directly counteract the bending stress of the external force acting on the foundation, so that the bending rigidity of the foundation portion of the building can be increased. In addition, the tight part of the tightening member is not buried in the concrete due to the protective formwork, so the tightening part of the tightening member can be loosened even after completion of construction, and the improved wall itself will not sink due to the effects of earthquakes and groundwater, etc. Even in such a case, it is possible to adjust the unevenness by lifting the upper part from the direct foundation of the building by jacking up, and to continue using the building.

  According to the invention described in claim 2, in the ground improved direct foundation method according to claim 1, a soil cement column is constructed by mixing and stirring while discharging slurry containing water and cement to the soft ground. Therefore, in addition to the ground improvement direct foundation, piles of soil cement columns can be used in combination, and it is possible to obtain a ground strength that supports the building even on soft ground.

  According to the invention described in claim 3, in the ground improved direct foundation method according to claim 1 or 2, the fastening member is installed near both ends of each street except the outer periphery of the improved wall. The balance between the foundation and the improved wall on the flat surface is good, and the improved wall and the foundation can be directly opposed to each other regardless of the bending stress acting on the building from any direction. The weakness of the directionality on rigidity disappears.

  According to a fourth aspect of the present invention, in the ground improved direct foundation method according to any one of the first to third aspects, the improved wall is rolled and divided into a plurality of layers at a predetermined depth, and the tightening is performed. Since the member is installed in the excavation groove for the improved wall after the lowermost layer rolling of the improved wall, at least the lowermost layer portion of the improved wall exists under the fastening member, and the lowermost layer of the improved wall It becomes possible to adjust the unevenness of the tightening member by obtaining a reaction force from.

  According to a fifth aspect of the present invention, in the ground improved direct foundation method according to the fourth aspect of the present invention, the fastening member includes a U-bolt formed with screw threads at both ends, and substantially at both ends of the U-bolt. A level material that is horizontally stretched, the center portion is directly fixed to the foundation, and both end portions are disposed in the protective mold, and the both end portions of the level material are screwed into the thread of the U bolt. It is equipped with a level adjustment nut that is tightened and fixed, so even if the improved wall itself subsides due to the influence of an earthquake or groundwater, the level adjustment nut is used to obtain a reaction force from the bottom layer of the improved wall. Level can be taken easily.

  According to a sixth aspect of the present invention, in the ground improved direct foundation method according to any one of the first to fifth aspects, the protective form frame is formed of a square sleeve having a protective cap fitted into an upper portion thereof and freely openable and closable. In addition, since it is a driving mold without removing the protective mold, it is possible to eliminate the trouble of removing the protective mold and to expose the tightening portion of the tightening member by simply removing the protective cap from above the foundation. It is possible to easily adjust the unevenness by loosening the binding part.

It is a foundation plan which shows the plane shape of the solid foundation and improvement wall which are built with the ground improvement direct foundation method concerning Example 1. It is a vertical sectional view which mainly shows a solid foundation outer peripheral part same as the above. It is the elements on larger scale which mainly show the fastening part of the fastening member used with the ground improvement direct foundation construction method concerning Example 1. FIG. It is a vertical sectional view showing a modification of the above-described binding member. It is a photograph which shows the flooring process of the ground improvement direct foundation method which concerns on Example 1. FIG. It is a photograph which shows the marking process of the improved wall same as the above. It is a photograph which shows the excavation process of the improved wall part same as the above. It is a photograph which shows the solidification material and soil stirring process same as the above. It is a photograph which shows the process of refilling a solidification material and soil same as the above into an improved wall part. It is a photograph which shows the rolling process of the improved wall same as the above. It is a photograph which shows the unevenness adjustment process same as the above. It is a photograph which shows a moisture-proof sheet laying process same as the above. It is a photograph which shows a basic reinforcement and an outer periphery formwork installation process same as the above. It is a photograph which shows the raw concrete placement process of the pressure-resistant plate of a foundation same as the above. It is a photograph which shows the leveling process of the pressure | pressure-resistant version raw con. It is a photograph which shows the stand-up formwork installation process of a foundation same as the above. It is a photograph which shows the finishing condition of the foundation after a form-pasting process same as the above. It is a foundation plan which shows the plane shape of the solid foundation constructed by the ground improvement direct foundation method concerning Example 2, an improvement wall, and a soil cement column. It is a photograph which shows the stirring shaft setting condition of the soil cement column construction process of the ground improvement direct foundation method which concerns on Example 2. FIG. It is a photograph which shows the re-stirring condition of the soil cement column construction process same as the above. It is a schematic diagram which mainly shows schematic structure of the solid foundation constructed | assembled by the ground improvement direct foundation method which concerns on Example 2, an improved wall, and a soil cement column.

  An embodiment of the present invention will be described with reference to the drawings.

The ground improvement direct foundation method according to Example 1 of the present invention will be described in the order of steps with reference to FIGS.
In addition, as shown in FIG.1 and FIG.2, the direct foundation constructed | assembled by the ground improvement direct foundation method of a present Example is the pressure plate 10 with the rectangular planar shape laid over the building construction whole surface of the building, As shown in FIG. 1, the improvement wall 2 which is a solid foundation 1 composed of rises 11 provided around the four circumferences and is constructed by performing ground improvement is a plan view consisting of X1 to X4 and Y1 to Y3. The case where the wall is an improved wall with a grid pattern will be described. However, the photographs in FIGS. 5 to 17 are for explaining the process, and the shapes of the foundation and the improved wall are different in each photograph.

(Advance preparation)
As a preliminary preparation, the ground of the place where the building will be constructed will be surveyed using known ground survey techniques such as standard penetration tests and Swedish penetration tests. Then, when the survey result is determined to be soft ground, the ground improvement direct foundation method according to the present embodiment is applied. If the ground where the building is built is not soft ground, a relatively light building such as a wooden house can support the building simply by constructing a solid foundation such as a solid foundation. This is because it is not necessary to apply such a foundation improvement direct foundation method. In general, in the standard penetration test, when the soil has an N value of 4 or less in the case of organic soil or cohesive soil, and when the N value is 10 or less in the case of sandy soil, it is determined as soft ground.

(Drilling, flooring)
First, excavation heavy equipment such as a backhoe excavates from the design GL to a predetermined depth according to the structural design, and determines the depth of the bottom surface of the solid foundation by measuring the level difference from the design GL. As shown in FIG. To do. If necessary, the flooring surface may be laid with gravel (cutting stone) having a thickness of about 50 mm, rolled, and thrown away. Placing a throwaway container makes it easy to pick up the ink and accurately determines the position of the solid foundation.

(Ground improvement)
Next, according to the structural design, the portion for ground improvement is marked with slaked lime or the like (see FIG. 6), and excavated with a heavy excavator such as a backhoe to the depth that becomes the bottom of the improved wall to be constructed (see FIG. 7). Of course, the width and depth (height) of the ground improvement part (improvement wall) are determined according to the structural design. It is 450 mm and the depth is about 600 to 1200 mm. Then, the solidified material to be described later is mixed and stirred in the excavated soil (see FIG. 8), and the soil mixed with the solidified material is backfilled in the excavated portion (see FIG. 9). The improved wall 2 is constructed by pressing and compacting (see FIG. 10). In the present embodiment, the improvement wall 2 is divided into a plurality of layers for every 300 mm in depth so that the improvement wall 2 is compacted over the entire height direction. In this embodiment, a case where the improved wall 2 having a depth of 600 mm is rolled in two steps will be described.

(Solidification material)
Further, the solidifying material used in this example is a cement-based solidifying material (for example, registered trademark: Tough Rock (manufactured by Sumitomo Osaka Cement Co., Ltd.)) in which several types of additives such as gypsum and slag are added with cement as a main component. , Registered trademark: Youth Tabira (manufactured by Ube Mitsubishi Cement Co., Ltd.), registered trademark: Geoset (manufactured by Taiheiyo Cement Co., Ltd., registered trademark: Hard Keep (Tokuyama Co., Ltd.)). In addition, this solidifying material has the function of hydration reaction of the moisture in the soil and the cement in the solidifying material to solidify the soft ground and improve the soil strength. High organic soil such as highly hydrous mud soil and humus soil, which has been difficult to solidify, can be solidified by fixing the excess water in the soil due to the effect of additives, and generating hydrates that are not affected by organic matter. It has become. In addition, you may use the lime type solidification material which has quick lime or slaked lime as a main component according to the soil quality of the soil which performs ground improvement.

(Installation of U-bolts)
After rolling the first layer (lowermost layer) of the improved wall 2, the U-bolt 30 of the band connector 3 as a fastening member is placed in the excavation groove for the improved wall 2 at the position shown in FIG. Except Y1, Y3, X1, and X4 ways that hit the outer periphery of Y2, Y2 ways, X2 ways, and near both ends of X3 ways, and Y2 ways on both sides of X2 and X3 ways, a total of 10 places. Thereafter, the remaining second layer is backfilled and compacted and compacted to build the improved wall 2 in the ground.

(Structure of binding members)
As shown in FIG. 2, the band connector 3 includes a U-bolt 30, an L-shaped angle 31 that is a level material, and a level-adjusting nut 32 that includes one-to-two (total of four) nuts with washers. The pressure resistant plate 10 of the solid foundation 1 and the improved wall 2 are connected to each other so as not to be displaced in the horizontal direction. As shown in FIG. 2, the U-bolt 30 is a threaded U-bolt that is processed from a round steel having a diameter of 13 mm into a U-shape and has a thread formed at the upper end of the U-shape serving as both shaft ends. There is an L-shaped angle 31 to be described later on the threaded portions 30a, 30b in which the thread is formed.
Needless to say, the L-shaped angle 31 is not limited to an angle member as long as it has a predetermined rigidity, and may be a rectangular flat plate. Further, as shown in FIG. 4, the U bolt may be a U bolt 30 ′ whose bottom portion 30 c ′ is formed in a flat plate shape. With such a configuration, the U-bolt 30 ′ is self-supporting in the above-described U-bolt installation process, so that operations such as backfilling for the second and subsequent layers are facilitated.

(Non-land adjustment and moisture-proof sheeting)
When the rolling of the improved wall 2 is completed, the entire bottom portion of the pressure-resistant plate 10 (see FIG. 2) of the solid foundation 1 is rolled while measuring the level with a rolling machine such as a roller or a rammer, and is not landed. Adjustment is performed (see FIG. 11). Also, thin film-like resin sheets such as polyvinyl chloride sheets and polyethylene sheets are used to prevent moisture in the soil from rising below the floor of the building and to prevent insects such as ants from entering the ground. The moisture-proof sheet made of is placed on a portion other than the upper surface of the improved wall 2 and below the pressure-resistant plate 10 of the solid foundation 1 (see FIG. 12). In addition, since the upper surface of the improved wall 2 is tightly coupled to the solid base 1 in the subsequent process by the band connector 3, the moisture-proof sheet is not laid.

(Installation of basic reinforcement and outer formwork)
Next, the pressure-resistant plate 10 of the solid foundation 1 is arranged according to the structural design, and the outer peripheral formwork of the rising 11 of the solid foundation 1 is installed (see FIG. 13). At this time, if there is equipment piping penetrating the pressure plate, they are preceded by actual piping. This is because if the equipment piping is installed later, the bar arrangement of the pressure plate may be cut by core removal or the like. Subsequently, the rising portion of the foundation is placed (see FIG. 13).

(Installation of level materials and protective formwork)
Next, the L-shaped angle 31 is spanned over the screw portions 30a and 30b which are the upper end portions of the U bolts 30 installed in the previous process, and the level adjustment nut 32 is used to fix the level so that the level is approximately horizontal. At this time, a rectangular tube whose upper and lower sides are opened as protective molds for protecting concrete from entering the periphery of the screw portions 30a and 30b, which become the tightening portion of the band connector 3 (the portion where the tightened state is loosened or tightened, the same applies hereinafter). A square sleeve 4 is also installed. Specifically, a slit for inserting the L-shaped angle 31 is formed in advance in the pair of square sleeves 4, and the L-shaped angle is set together with the rectangular sleeve 4 in a state where both ends of the L-shaped angle 31 protrude from the slit. 31 is set so as to span the threaded portions 30a, 30b of the U bolt 30. As shown in FIG. 3, U-cuts (U-shaped notches) 31a are cut at both ends of the L-shaped angle 31, and screw portions 30a, 30b of the U bolt 30 are cut into the U-cut 31a. And is clamped by two nuts 32 (with washers) to be fastened to the U-bolt 30 so as to be substantially horizontal.

  Note that the L-shaped angle 31 is disposed above the bottom bar arrangement of the pressure-resistant plate 10 so that the central portion thereof is fixed to the pressure-resistant plate 10 of the solid foundation 1. Then, a protective cap 5 that closes the upper opening of the square sleeve 4 that is a protective mold is fitted (see FIG. 2), and when concrete is placed on the pressure-resistant plate 10 of the solid foundation 1 in a subsequent process, Prevent concrete from entering (see Fig. 14). Further, rubber packing P may be provided as shown in FIGS. 2 and 3 so that the concrete does not enter from the slit for inserting the L-shaped angle of the square sleeve 4 (see also FIG. 4). .

(Installation of pressure-resistant plate in raw concrete, installation of rising formwork)
Next, raw concrete (fresh concrete) is placed while confirming the level on the pressure-resistant plate portion of the foundation (see FIG. 14), and the top end is finished with a wooden mallet or the like (see FIG. 15). At this time, care should be taken so that the raw food container does not enter the square sleeve 4. When the ready-cured portion is hardened, the exact position of the rising portion of the foundation is marked and a rising form is installed (see FIG. 16). Next, live concrete is placed at the rising edge of the foundation.

(Formwork payment)
Curing is carried out for a predetermined period until strength is developed, and then the formwork is removed (removed), whereby the foundation work by the ground improvement direct foundation method according to Example 1 is completed (see FIG. 17). If the rise (height) of the foundation is small, the riser can be used as a floating formwork, and the raw concrete can be simultaneously placed on the foundation pressure plate part and the rise part. By doing so, the process can be shortened and there is a merit in terms of cost.
Further, the square sleeve 4 which is a protective formwork of the tightly connected portion may be removed together when the formwork is removed, but may be used as a driving formwork without being removed. This is because the trouble of removing the protective formwork can be saved.

  According to the ground improvement direct foundation method according to the first embodiment described above, the solid foundation 1 and the improved wall 2 are fastened with the band connector 3 which is a fastening member, so that the bending stress of the external force acting on the building is Since the improved wall and the direct foundation face each other, the bending rigidity of the foundation portion of the building can be increased.

In addition, since the band connector 3 is protected by the square sleeve 4 and is not cast with concrete, it can be exposed immediately by removing the protective cap 5, and the improved wall itself is affected by the effects of earthquakes and groundwater. Even in the event of subsidence, the solid foundation and the improved wall can be easily released, and the building can be lifted up by jacking up directly from the foundation of the building to keep the building in use. Is possible.
The space between the foundation and the improved wall generated by jacking up may be temporarily fixed with an iron plate or a concrete block, and then fluidized concrete or the like is poured into the space.

  In addition, as shown in FIG. 2, the improved wall 2 is rolled into a plurality of layers (two layers) at a predetermined depth (300 mm), and the U-bolt 30 of the band connector 3 is one layer of the improved wall 2. Since it is installed in the excavation groove for the improved wall after the rolling, the first layer of the improved wall 2 exists under the band connector 3, and even when the improved wall 2 itself sinks, The reaction force is obtained from the first layer, and the unevenness adjustment of the band connector 3 can be easily performed.

  In addition, the band connector 3 includes the Y1, Y3, X1, and X3 streets except for the Y1, Y3, X1, and X4 streets that hit the outer periphery of the improved wall 2, and both sides of the X2 and X3 streets of the Y2 street. Since the installation location is a total of 10 locations, the solid foundation 1 and the improved wall 2 are well balanced on the plane, and the solid foundation and the improved wall can be applied to any external bending stresses. 2 can be opposed to each other, and there are few weaknesses in the directionality in bending rigidity.

  Next, the ground improvement direct foundation method according to Embodiment 2 of the present invention will be described with reference to FIGS. The difference from the ground improvement direct foundation method according to Example 1 is only that a process for constructing an improved pile of the soil cement column by the soil cement method described later is added, and the rest is the same. Only the process of constructing an improved pile of il-cement columns will be described, and the description of the rest is omitted.

  Similar to the ground improvement direct foundation method according to the first embodiment, the ground at the place where the building is constructed is investigated, and when the N value is soft ground close to 0, the ground improvement direct foundation method according to the second embodiment is applied. Is done. That is, the ground improvement direct foundation method according to the second embodiment is further softened by adding the supporting force of the soil cement column described later to the supporting force of the foundation constructed by the ground improvement direct foundation method according to the first embodiment. It is a construction method that allows a building to be supported directly on the foundation without providing support piles that reach the support layer even on the ground.

(Construction of soil cement column)
First, the soil is located at the position between the streets of the improved wall 2 and the points of construction of the soil cement column C according to the structural design (in this embodiment, four points P1 to P4 shown in FIG. 18). Set the agitation shaft of the cement construction machine (pile driver) (see Fig. 19), rotate the agitation shaft to drill to a predetermined depth that will be the bottom of the soil cement column C (see Fig. 21) determined by the structural design ( Digging). Next, while discharging the slurry obtained by dissolving the cement-based solidifying material or cement in water, the stirring shaft is gradually pulled up, and the soil and the slurry are mixed and stirred. After pulling out the stirring shaft to the ground surface, the stirring shaft is lowered again while rotating to the bottom surface and stirred again (see Fig. 20), and water and cement hydrate and solidify so that the soil cement in the soft ground (See FIG. 21).
Note that the re-stirring is performed at a higher speed than when it is pulled out, and the top end of the soil cement column measures the level, and the high portion is subjected to pile head processing to set the top end level to a predetermined value according to the structural design.

  The construction process of this soil cement column can be performed even after the ground improvement process, if it is before the unevenness adjustment explained in the ground improvement direct foundation method according to Example 1, but it carries in the soil cement construction machine which is a heavy machine Therefore, it is desirable to complete the process before the excavation and flooring process. This is because even if excavation or flooring is performed, the level is disturbed by the movement of heavy machinery.

  According to the ground improvement direct foundation method according to the second embodiment, in addition to the direct foundation support force constructed by the ground improvement direct foundation method according to the first embodiment, the support force of the soil cement column is added. Even in a difficult ground, the building can be supported directly by the foundation without providing support piles.

  As described above, the direct foundation constructed by the ground improvement direct foundation method according to the first and second embodiments of the present invention is a solid foundation, and the pressure plate is illustrated with a double bar arrangement as an example. The pressure-resistant plate may be a single reinforcing bar, and in that case, the L-shaped angle 31 is arranged so that the L-shaped angle 31 is at least above the lowermost reinforcing bar so that the L-shaped angle 31 is fixed to the pressure-resistant plate 10. Moreover, the direct foundation constructed | assembled by the ground improvement direct foundation construction method which concerns on Example 1 and 2 is not restricted to a solid foundation, You may be other direct foundations, such as a cloth foundation. And although the improvement wall constructed by improving the ground has been described in the case of a grid, it can also be applied to the case where the ground is improved over the entire surface directly below the solid foundation. It should be noted that the illustrated shapes, such as the shape of the foundation, are merely examples, and it goes without saying that they can be changed within the scope described in the claims.

1 Solid foundation (direct foundation)
10 Pressure-resistant plate 11 Rise 2 Improved wall (improved ground)
3 Band connector (tightening member)
30 U bolt 31 L type angle (level material)
32 Level adjustment nut 4 Square sleeve (protective formwork)
5 Protective cap C Soil cement column

Claims (6)

Improving the ground by mixing the solidified material in the soft ground and stirring and then rolling to form an improved wall in the shape of a grid in plan view, and constructing a foundation directly on this improved wall In the construction method,
Installing a fastening member fixed to the direct foundation and fastening the improved wall and the direct foundation; installing a protective form that partitions the fastening portion of the fastening member so as not to be buried in concrete; A ground improvement direct foundation method characterized by having   The ground improvement direct foundation method according to claim 1, further comprising a step of constructing a column of soil cement by mixing and stirring while discharging slurry containing water and cement to the soft ground.   The ground improvement direct foundation method according to claim 1 or 2, wherein the tightening member is installed in the vicinity of both ends except for the outer periphery of the improved wall. The improved wall is rolled and divided into a plurality of layers at a predetermined depth,
The ground improvement direct foundation method according to any one of claims 1 to 3, wherein the tightening member is installed in the excavation groove for the improved wall after rolling the lowermost layer of the improved wall.   The binding member includes a U-bolt having screw threads formed at both ends thereof, and spans substantially horizontally between both ends of the U-bolt, and a central portion is directly fixed to the foundation, and both ends are within the protective mold. The ground according to claim 4, further comprising: a level member disposed on the ground, and a level adjusting nut that is screwed into a screw thread of the U bolt to fasten and fix both ends of the level member. Improved direct foundation method.   6. The protective mold frame according to any one of claims 1 to 5, wherein the protective mold frame is formed of a square sleeve that can be freely opened and closed with a protective cap fitted thereon, and further, the protective mold frame is a driving mold frame without removing the protective mold frame. The ground improvement direct foundation method described in crab.