JP5013948B2 - Building foundation construction method - Google Patents

Description

  The present invention relates to a technique for creating a foundation in a ground that may cause liquefaction such as a sand ground or other ground.

In FIG. 16, the building 1 is formed on the sand ground 3 that may cause liquefaction. This building 1 is built on a solid foundation 8A.
The foundation 8A is constructed in a range from the ground surface GL to the stable ground 5. The stable ground 5 is located below the sand ground 3.

Since the foundation 8A of FIG. 16 has reached the stable ground 5, even if the sand ground 3 is liquefied by an earthquake, the building 1 can be stably supported.
However, in the foundation 8A as shown in FIG. 16, the displacement or vibration caused by the earthquake is directly input to the building 1 through the solid foundation 8A, and the building 1 is damaged by the displacement or vibration caused by the earthquake. End up.

On the other hand, although not shown in FIG. 16, a seismic isolation device can be installed between the foundation 8A and the building 1 to absorb and reduce vibration and displacement caused by the earthquake through the foundation 8A. Has been done conventionally.
However, when using such a seismic isolation device, if the elastic material is rubber, it is necessary to ensure that there is no variation in the elastic coefficients (so-called spring constants) of the plurality of seismic isolation devices. At the same time, in consideration of the non-linear spring constant inherent to rubber, it must be installed so that there is no difference in initial strain in each seismic isolation device. Installation of such a seismic isolation device is not an easy task at a construction site.

Moreover, when arranging a plurality of vibration isolation devices, it is necessary to consider the structure and weight distribution of the building.
Furthermore, when the rubber material of the vibration isolator is exposed to the air, there is a problem that deterioration is unavoidable and must be replaced at an appropriate time.

As another conventional technology, when creating the foundation of a building on the ground that may cause liquefaction, such as sand ground, the ground that may cause liquefaction, the area that maintains its properties, and liquefaction There is disclosed a technique of dividing into a non-improvement region (for example, see Patent Documents 1 to 3).
However, these technologies have problems in concrete implementation and difficulty in predicting effects not only in the occurrence of earthquakes but also in the current situation where the seismic intensity and frequency of earthquakes cannot be predicted. is doing.

Also disclosed is a technology in which a support pile or a cement wall is formed on a support ground located below the sand ground (no risk of liquefaction), and a vibration isolator is disposed above the support pile or cement wall. (For example, see Patent Document 4).
However, in such a technique, for example, a vibration isolator having a constant spring constant needs to be arranged at a predetermined position on the support pile or the cement wall. The most common vibration isolator uses rubber as an elastic material, but the spring constant of the rubber material, including nonlinear characteristics, is not easy to suppress, for example, about 10%, and the cost increases. End up.

Similarly to the case of the seismic isolation device using rubber described in relation to FIG. 16, if a plurality of vibration isolation devices are arranged, it is necessary to consider the relationship between the structure of the building and the weight distribution. is there. Furthermore, when the rubber material of the vibration isolator is exposed to the air, deterioration is unavoidable and must be appropriately replaced.
JP 2000-96580 A JP 2003-20659 A JP 11-315544 A JP 2001-32570 A

The present invention has been proposed in view of the above-mentioned problems of the prior art, and is a foundation built on a ground that may cause liquefaction like a sand ground, and is constructed even if liquefaction occurs. The object of the present invention is to provide a method for constructing a foundation of a building that can support the object and can provide the building with seismic isolation.
In addition, the present invention does not break the boundary between the building and the foundation even if an earthquake occurs, and can sufficiently absorb or attenuate the energy of the earthquake to improve the seismic strength. The purpose is to provide a method that can be used to create the foundation of a building.

  According to the present invention, the boring hole is drilled from the ground surface (GL) through the sand ground (3) to the stable ground (5) by the boring hole drilling device (6), and the boring hole (7) The solidified material injection device (11, 11A) is inserted into the ground, the solidified material injection device (11, 11A) is rotated while the solidified material is injected, and the solid material is pulled up to reach a stable ground (5) in the ground. In the construction method of the foundation of the building for constructing the improved body (8), the solidified material is injected from the solidified material injection device (11, 11A) from the bottom of the boring hole (11) to the predetermined depth (D) to the lower part. The improved portion (8b) is formed, and from the predetermined depth (D) to the vicinity of the ground surface (GL), the solidified material and the elastic material are mixed and injected to form the upper improved portion (8b).

  Moreover, according to this invention, the said underground improvement body is comprised by the some improvement body (18).

  And according to this invention, the said underground improvement body is comprised with the continuous-wall-like improvement body (19).

In the present invention, the improved body (8) is preferably a continuous wall.
For example, the connecting walls are preferably arranged in a grid pattern or a grid pattern.

  According to the present invention having the above-described configuration, the improved body in the ground reaches the stable region (the region that does not liquefy), and therefore, even if the ground liquefies, the stable region (the region that does not liquefy) Since the improvement body that has reached) does not fluidize, the building constructed on it is not affected by the liquefaction of the ground.

  Further, according to the present invention, since the elastic material (for example, rubber chip, foam material, asphalt) is uniformly mixed and injected into the solidified material, the improved body (for example, the region near the building 1) is elastic. is there. Therefore, for example, even if there is a lateral shaking earthquake, the lateral elasticity in the improved body absorbs the displacement or vibration caused by the earthquake and functions as a seismic isolation structure.

In addition, for example, with regard to vertical vibration, the vertical elasticity of the improved body absorbs the displacement and vibration, so that the vertical displacement acting on the building on the foundation is absorbed to prevent the building from being damaged. Function.
That is, not only the lateral vibration but also the vertical vibration can be absorbed.

According to the building foundation construction method of the present invention having the above-described configuration (Claims 5 and 6), the solidifying material (for example, cement milk) and the minute elastic material (for example, rubber chip) are sprayed from the spraying means. The improved body is created in the ground.
Here, in the foundation (Gc) in which a minute elastic material (rubber chip) is mixed, even if the stress that can be applied (σ axis in FIG. D) is similar to that of the conventional foundation, allowable strain (FIG. D The ε-axis) is much larger. Therefore, the seismic energy that can be absorbed (damped) by the foundation (Gc) is much larger than that of the conventional foundation (see FIG. D).

  Therefore, even if the seismic intensity is considerable, the earthquake energy is absorbed by the foundation (Gc), and the earthquake energy acts intensively on the fixed part of the building (1) and the foundation (Gc). There is no. Therefore, it is possible to prevent the fixed portion between the foundation (Gc) and the building (1) from breaking. And, due to the excellent seismic energy absorption capacity (damping characteristics) in the foundation (Gc), the foundation or the structure fixed to the foundation has good earthquake resistance.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
In the seismic isolation device according to the illustrated embodiment, damage to the liquefaction of the sand ground 3 is avoided, and the foundation 8A described with reference to FIG. It is configured to reduce the transmission.

1 to 6 show a first embodiment of the present invention.
The foundation created by the construction method according to the first embodiment is indicated by reference numeral 8 in FIG.
In FIG. 1, an unstable ground 3 such as a sand ground, which has a fear of liquefaction, is located in an area reaching the ground surface GL above a stable ground 5 such as a clay ground or a rock ground that is not liable to be liquefied. Existing.

In FIG. 1, an improved body 8 having a height H is formed so as to reach the stable ground 5 from the ground surface GL of the unstable ground 3. In the stable ground 5, the improved body 8 reaches an appropriate depth.
The improved body 8 is formed by, for example, injecting and mixing the solidifying material 17 into the grounds 3 and 5.
For simplification, only one columnar improvement body is shown in FIG. 1, but in actual ground improvement, a plurality of columnar improvement bodies are created to form a connecting wall and the like. ing.

In FIG. 1, the improvement body 8 consists of the lower improvement part 8b and the upper improvement part 8a.
The lower improvement part 8b has the intensity | strength of the grade which does not lose a supporting force, even if the in-situ soil and the solidification material of the ground 3 are mixed and stirred, for example, even if the sand ground 3 liquefies.
The upper improvement part 8a is formed by mixing the in-situ soil of the ground 3 and the solidified material, for example, an elastic material 21 such as a rubber chip, a foaming agent, and asphalt, and also mixing the elasticity and stirring it. Has been.

  A building 1 is built in the shape of the improved body 8. The bottom 1a of the building 1 is in close contact with the upper part of the upper improvement part 8a.

FIG. 2 represents the improved body 8 in FIG. 1 imitating a mechanical model.
The lower improvement portion 8b (that is, the stable ground 5) corresponds to the floor surface in the mechanical model, and the spring 8a that is provided above the lower improvement portion 8b and bends in the vertical direction corresponds to the upper improvement portion 8a.

In the model shown in FIG. 2, when an earthquake occurs and the lower improved portion 8b causes a so-called vertical runout (displacement in the vertical direction), the upper improved portion 8a corresponding to a spring is compressed or extended to construct a building. Move 1 up and down.
If the repetition of the vertical displacement speed of the lower improvement portion 8b, that is, the frequency is higher than the upper and lower natural frequency formed by the building 1 and the spring constant of the spring 8a, the displacement of the building 1 is reduced by the lower improvement portion 8b. It becomes smaller than the vertical displacement, and the vibration transmissibility is reduced.
In FIG. 2, the case where the spring constant is the vertical spring constant has been described, but the same applies to the relationship between the lateral spring constant (sender direction spring constant) and the lateral displacement.

The creation of the improved body 8 as described above will be described below with reference to FIGS.
First, as shown in FIG. 3, the boring hole 7 is drilled by the boring drilling device 6 from the ground surface GL through the sand ground 3 to the stable ground 5. In FIG. 3, the depth of the bore hole 7 is indicated by the symbol H.

When the drilling of the boring hole 7 is completed, the solidified material injection device 11 as shown in FIG. 4 is inserted into the boring hole 7.
The solidifying material injection device 11 is a device for injecting the solidifying material in a horizontal direction at a high pressure from the inside of the boring hole 7 into the ground to be improved. By injecting the solidifying material into the ground and pulling up the solidifying material injection device 11 while rotating, a plurality of columnar (pile-shaped) underground consolidated bodies are formed. About the solidification material injection apparatus 11, a well-known thing is used.

Here, the solidifying material injection device 11 as shown in FIG. 4 is a type that injects the solidified material jet J in the horizontal direction, but as shown in FIG. 5, the solidifying material jet Ja intersects and collides. Further, it is possible to adjust the radial dimension of the improved body 8 with high accuracy by preventing the solidified material jet Ja from proceeding outside the intersection.
The solidified material injection device 11A of the type shown in FIG. 5 (the type in which the jets Ja intersect and collide) is a device (monitor) that injects a so-called “cross jet” or “cross jet”.

FIG. 6 shows an embodiment in which a solid cylindrical solid body is formed using the solidifying material injection devices 11 and 11A as shown in FIG. 4 or FIG.
As described above, the solidifying material injection device 11 (or 11A) is inserted into the boring hole 7, and the solidified material jet J or Ja is supplied to the stable ground 5 and the sand ground 3 (the ground that may be liquefied). While injecting, the solidifying material injection devices 11 and 11A are rotated and pulled up.
Thereby, it stirs with a solidification material, cutting the in-situ soil of the stable ground 5 and the sand ground 3, and the improvement body 8 is created.

When the improved body 8 is created, only the solidified material is sprayed onto the sand ground 3 and the stable ground 5 in a region below a predetermined depth D (see FIG. 6). Accordingly, the lower improved portion 8b having sufficient strength to support the building 1 (see FIG. 1) is created.
In the region from the vicinity of the ground surface GL to the predetermined depth D, in addition to the solidified material, for example, an elastic material such as a rubber chip, a foam material, and asphalt is uniformly mixed and sprayed onto the sand ground 3. Accordingly, the upper improved portion 8a having elasticity is formed.
Thereby, the improved body 8 is formed by laminating the upper improved portion 8a having elasticity on the upper portion of the lower improved portion 8b having sufficient strength to secure a necessary supporting force.

As described above, the lower improvement portion 8b formed by mixing and stirring the solidified material and the in-situ soil is the building 1 built on the improved body 8 even if the sand ground 3 in the surrounding area is liquefied. It has sufficient strength to support
On the other hand, the upper improved portion 8a formed by mixing and stirring the solidified material, the elastic material, and the in-situ soil of the sand ground 3 is lower in rigidity or strength than the lower improved portion 8b, and the elastic modulus is small. Therefore, even if the ground 5 vibrates in the event of an earthquake, the vibration is absorbed by the elasticity of the upper improved portion 8 a, attenuated, and transmitted to the building 1 built on the improved body 8. That is, the upper improvement part 8a has the same effect as a seismic isolation device.

7 and 8 show a foundation built by the construction method according to the second embodiment of the present invention.
7 and 8 constitute the foundation of the building 1 by a plurality of small-diameter improvements 18.
Here, FIG. 7 is a top view, and FIG. 8 is a side view of FIG.
The improvement body 18 has the structure which laminated | stacked the upper improvement part 18a which comprises elasticity, and the lower improvement part 18b which has required support strength similarly to having demonstrated in FIGS.

In the construction method according to the second embodiment, that is, in FIG. 7 and FIG. 8, the construction method for constructing each of the nine improved bodies 18 is the same as the construction method described with reference to FIGS.
A plate-like body 22 is placed on the improved body 18, and the building 1 is built on the plate-like body 22.
The maintenance of the supporting force when the sand ground is liquefied and the effect of seismic isolation against the earthquake are the same as those of the improved body 8 described with reference to FIGS.

9 and 10 show an improved body created by the method according to the third embodiment of the present invention.
In the construction method according to the third embodiment shown in FIGS. 9 and 10, the improved body 19 formed is formed in a cross beam shape with continuous wall surfaces (continuous walls).
Here, FIG. 9 is a top view, and FIG. 10 is a side view of FIG.
The improvement body 19 created by the construction method according to the third embodiment is similar to the improvement bodies 8 and 18 created by the construction method according to the embodiment of FIGS. 1 to 8, and the upper improvement portion 19a having elasticity, The lower improvement portion 19b is formed by mixing and stirring the solidified material and the in-situ soil.

  9 and 10 (the construction method for creating the improved body 19) also cuts the original soil, while the original soil and the solidified material (in the upper improved body 19a, the solidified material and the elastic material). And are mixed and stirred.

That is, when creating the continuous wall-shaped improvement body 19, the solidifying material injection devices 11, 11 </ b> A are pulled up without rotating, or correspond to the wall thicknesses t <b> 1, t <b> 2 of the cross-girder-shaped improvement body 19. In order to cut only the in-situ soil in the range to be cut, the solidifying material injection devices 11 and 11A are intermittently reciprocally rotated by an angle corresponding to the wall thicknesses t1 and t2 in the continuous wall-shaped improvement body 19 ( Pull up while swinging).
Alternatively, the continuous wall-like improvement body 19 can be formed without swinging the solidifying material injection devices 11 and 11A. Furthermore, it is also possible to constitute a continuous wall by a plurality of columnar improvements.

Other configurations in the construction method according to the third embodiment in FIGS. 9 and 10 are the same as those described in FIGS.
9 and 10 also, only the solidified material is sprayed onto the sand ground 3 and the stable ground 5 in the region below the predetermined depth D (see FIG. 10). On the other hand, in the region from the vicinity of the ground surface GL to the predetermined depth D, in addition to the solidified material, for example, an elastic material such as a rubber chip, a foam material, and asphalt is uniformly mixed and sprayed onto the sand ground 3. And the upper improvement part 19a provided with elasticity is laminated | stacked on the upper part of the lower improvement part 19b which has sufficient intensity | strength to ensure required support force.
The seismic isolation effect is also substantially the same as the improved bodies 8 and 18 described with reference to FIGS.

FIG. 11 shows an improved body created by the construction method according to the fourth embodiment of the present invention.
The improved body 20 shown in FIG. 11 is configured in a lattice shape with continuous wall surfaces.
In FIG. 11, the code | symbol 20a has shown the space in a grid | lattice-like continuous wall.
Although not clearly shown in FIG. 11, the improvement body 20 is also constituted by an upper improvement portion having elasticity and a lower improvement portion formed by mixing and stirring the solidified material and the in situ soil. Yes.

The construction method of the improved body 20 shown in FIG. 11 is the same as the construction method of the improved body 19 shown in FIGS.
That is, when the improved body 20 is created, the solidifying material injection devices 11 and 11A are pulled up as they are without rotating, or the solidifying material injection devices 11 and 11A are wall thickness in the continuous wall-shaped improved body 20. It is lifted while being intermittently reciprocated (oscillated) by an angle corresponding to t3 and t4.
In this case, it is possible to create the continuous wall-shaped improvement body 20 without swinging the solidifying material injection devices 11 and 11A. Furthermore, you may comprise a continuous wall by a some cylindrical improvement body.

Also when the improved body 20 shown in FIG. 11 is formed, the lower improved portion is formed by mixing and stirring the solidified material and the in-situ soil in the stable ground 5 and the sand ground 3. Then, in addition to the solidified material, for example, an elastic material such as a rubber chip, a foam material, and asphalt is uniformly mixed, mixed with the sand ground 3 and stirred to form an upper improved portion having elasticity, and necessary support An upper improved portion having elasticity is laminated on the upper portion of the lower improved portion having sufficient strength to secure a force.
Other configurations in the construction method according to the fourth embodiment of FIG. 11 are the same as those of the third embodiment of FIGS.

FIG. 12 shows a fifth embodiment of the present invention.
In FIG. 12, the foundation portion 1b of the building 1 is surrounded by an improved portion 31a having elasticity. The improved portion 31 a having elasticity penetrates the sand ground 3 and reaches the stable ground 5.

In the fifth embodiment shown in FIG. 12, since the improved portion 31a having elasticity reaches the stable ground 5, even if the sand ground 3 is fluidized, the improved body 31a is not fluidized, and the building 1 is not adversely affected by the liquefaction of the sand ground 3. And it can reduce that the vibration displacement by an earthquake transmits to the building 1 with the elasticity of the improvement part 31a.
Other configurations and operational effects are the same as those of the embodiment described with reference to FIGS.

13 to 15 show a sixth embodiment of the present invention.
In the sixth embodiment, in a building in which a pile-like solid body that reaches the stable ground 5 is already installed, an improved body having elasticity is created later, and vibration due to an earthquake is transmitted to the building 1. Is mitigating.

In FIG. 13, the building 1 already has pile-like solid bodies 42 and 42 extending in the underground direction from the foundation portion 1 b, and the pile-like solid bodies 42 and 42 have reached the stable ground 5. .
As is clear from FIG. 13, the foundation portion 1b of the building 1 is surrounded by an improved portion 31a having elasticity. In other words, the peripheral region of the foundation portion 1b of the building 1 is configured by the improved portion 31a having elasticity.
In addition, it is the area | region of the sand ground 3 that the improvement part 31a provided with elasticity is created.

In the configuration as shown in FIG. 13, since the existing pile-like solid bodies 42, 42 reach the stable ground 5, even if the sand ground 3 is liquefied, the pile-like solid bodies 42, 42 Since the building 1 is supported by the stable ground 5, it is safe.
In addition, in the case of an earthquake, in particular, a so-called “rolling” earthquake, the vibration due to the earthquake is attenuated or absorbed by the improved portion 31 a having elasticity. As a result, the building 1 is prevented from being damaged by vibration.

Next, referring to FIG. 14 and FIG. 15 for a mode of forming the improved portion 31a having elasticity as shown in FIG. 13 in the peripheral region of the foundation portion 1b where the pile-like solid bodies 42, 42 are already provided. To explain.
First, as shown in FIG. 14, from a place separated in the horizontal direction (left-right direction in FIG. 14) from the building 1 where the pile-like solid bodies 42, 42 extending in the underground direction from the foundation portion 1b are installed. Then, the small-diameter boring rod 46 having flexibility is excavated along the curved excavation line to the peripheral region of the base portion 1b by using the boring rod mounting device 48 (so-called “curved boring”).

By using a flexible small-diameter boring rod 46, a curved boring hole is drilled. The curved boring hole reaches a region 31a-1 (a region indicated by hatching in FIG. 14) immediately below the base portion 1b.
Using such a curved boring hole, an improved portion having elasticity is formed in the region 31a-1 immediately below the base portion 1b by a known method.

If an improved portion having elasticity is created in the region 31a-1 directly below the base portion 1b, as shown in FIG. 15, the region 31a-2 (FIG. 15) extending from the adjacent region of the region 31a-1 to the ground surface GL immediately above. In FIG. 2, two portions are shown, but in reality, an improved portion having elasticity is created in a known manner.
If the improvement part provided with elasticity in area | region 31a-1 and area | region 31a-2 is created, the improvement part 31a shown in FIG. 13 will be comprised.

First, an improved portion having elasticity is formed in the annular region 31a-2 using a known technique, and then the region 31a immediately below the base portion 1b is used by using a small-diameter boring rod 46 having flexibility. The improved portion 31a shown in FIG. 13 may be formed by creating an improved portion having elasticity at -1.
Other configurations and operational effects in the sixth embodiment of FIGS. 12 to 16 are the same as those of the above-described embodiments.

17 to 20 show a seventh embodiment of the present invention.
The seventh embodiment of FIGS. 17 to 20 relates to the creation of a foundation capable of improving the earthquake resistance, and is mainly intended for liquefaction countermeasures like the embodiments of FIGS. is not.
In FIG. 17, the building 1 to be built is indicated by a dotted line. In FIG. 17, in the ground G, a boring hole 7a is drilled in a region where the foundation of the building 1 to be built is to be created. Although the specific mode of the hole drilling is not clearly shown in FIG. 7, the hole drilling may be performed by applying a known technique.

Next, as shown in FIG. 18, the solidifying material injection device 11a is inserted into the boring hole 7a. The solidifying material injection device 11a is provided at the tip of the rod 72a. The rod 72a is connected to a rotation and insertion / pull-up mechanism (not shown), and can be rotated and moved vertically as will be described later. It has become.
A supply device 73 (a known and commercially available device can be applied as it is) is interposed in the rod 72a, and a cement milk supply source 74 is connected to the supply device 73 via a supply line L1, and A rubber chip supply source 76 is connected via the supply line L2. The solidifying material injection device 11a is configured such that cement milk as a solidifying material is supplied from a cement milk supply source 74 and rubber chips as a minute elastic material are supplied from a rubber chip supply source 76.

In the process shown in FIG. 19, the solidifying material injection device 11 a injects the jets J and J, which are a mixture of cement milk and rubber chips, into the ground G. At the same time, the rod 72a is rotated (arrow R in FIG. 19) and pulled upward (arrow UM in FIG. 19). Thus, the chopped soil, the cement milk, and the rubber chips are uniformly mixed while the cement milk and the rubber chips jets J, J chop the soil in the ground G.
In FIG. 19, the mixture of shredded soil, cement milk, and rubber chips is denoted by reference numeral Mc.

When the area near the ground surface is shredded with jets J and J, the soil, cement milk and rubber chips are uniformly mixed, and after a predetermined solidification period has elapsed, as shown by reference numeral Gc in FIG. The foundation is established. When the foundation Gc is created, the building 1 is constructed immediately above it (FIG. 20).
In FIG. 20, after building a cylindrical (pile-shaped) foundation Gc, the upper edge Gcu of the foundation Gc is fixed to the building 1.

  Here, in FIGS. 19 and 20, the foundation Gc formed by rotating the solidified material injection device 11 a while rotating is used as a rotating body (cylindrical shape), but the foundation Gc is not only a rotating body but also a flat plate shape. It is possible to create it in other shapes.

With reference to FIG. 21, the attenuation characteristic (or absorption capability) of the seismic energy in the created foundation Gc will be described.
In FIG. 21, the vertical axis indicates the stress σ acting on the constructed foundation, and the horizontal axis indicates the foundation strain ε.
According to the inventor's experiment, the seismic energy attenuation characteristic is shown by a characteristic curve PA in FIG. 21 on the basis of a conventional ground consolidated body composed only of cement milk and in-situ soil. On the other hand, the attenuation characteristic of the seismic energy in the foundation Gc according to the seventh embodiment (the foundation of the underground consolidated body formed by mixing cement milk, rubber chips and in-situ soil) is indicated by a characteristic curve PI.

In the inventor's experiment, the allowable strain ε in the conventional foundation (ground solid body without mixing rubber chips) is about 1%. On the other hand, the allowable strain ε in the case of mixing rubber chips increases to about 5% as in the base Gc according to the seventh embodiment.
As the strain ε increases, even if the loadable stress σ is approximately the same, absorption of seismic energy in the foundation Gc according to the seventh embodiment (a foundation formed by mixing cement milk, rubber chips, and in-situ soil) The capacity or damping characteristics are much greater compared to conventional foundations that do not mix rubber chips.

The seismic energy absorption capacity on the basis of only the conventional cement milk and in-situ soil is shown in FIG. 21 by the area of the hatched portion below the curve PA. That is, the area of the portion surrounded by the curve PA, the line of ε = 1%, and the ε axis (horizontal axis).
On the other hand, the seismic energy absorption capacity of the foundation according to the seventh embodiment described with reference to FIGS. 17 to 20 (the foundation formed by mixing cement milk, rubber chips and in-situ soil) is shown in FIG. This is indicated by the area of the portion with the hatching on the side (hatching different from the hatching on the lower side of the curve PA). That is, the area of the portion surrounded by the curve PI, the line of ε = 5%, and the ε axis (horizontal axis).

As is clear from the comparison between the two, the foundation constructed by mixing the cement milk, rubber chips and in-situ soil according to the first embodiment has a seismic energy absorption capacity compared to the conventional foundation (characteristic curve PA). Has improved.
Since the seismic energy absorption capacity (damping characteristics) of the foundation Gc is very good, even if the seismic intensity is considerable, the earthquake energy is absorbed by the foundation Gc and concentrated at a fixed location with the building 1 There is no end. Therefore, it is possible to prevent the fixed portion between the foundation Gc and the building 1 from being broken. Further, due to the excellent seismic energy absorption capacity (damping characteristics) of the foundation Gc, the earthquake resistance of the foundation or the building fixed thereto is also improved.

22 and 23 show an eighth embodiment of the present invention.
The eighth embodiment shown in FIGS. 22 and 23 is similar to the seventh embodiment shown in FIGS. 17 to 20, but differs in the manner of forming a cylindrical foundation (reference numeral Gc in FIG. 20).
FIG. 21 shows a state in which the solidifying material injection device 11b is inserted into the boring hole 7a, as shown in FIG. In FIG. 21, a supply device 73 (a known and commercially available device can be applied as it is) is interposed in the rod 72a, and a cement milk supply source 74 and a rubber chip supply source 76 communicate with the supply device 73. . Further, a cutting fluid supply source 78 communicates with the supply device 73 via a line L3.

FIG. 23 shows a step of filling the mixture of cement milk and rubber chips while chopping the soil in the ground G using the solidifying material injection device 11b.
In FIG. 23, the cutting fluid supplied from the cutting fluid supply source 78, for example, high-pressure water, is jetted as a jet Jc from the side of the solidifying material injecting device 11b in the horizontal direction to shred the ground. At the same time, the mixture M of cement milk and rubber chips is injected into the soil shredded by the cutting fluid jet Jc from below the solidifying material injection device 11b.

When the rod 72a is rotated (arrow R in FIG. 23) and pulled up (arrow UM in FIG. 23), the soil, cement milk, and rubber chips shredded by the cutting fluid jet Jc are mixed uniformly. . In FIG. 23, the mixture (mixture of shredded soil, cement milk, and rubber chips) is indicated by a symbol Mc.
Other configurations and operational effects in the eighth embodiment of FIGS. 22 and 23 are the same as those of the seventh embodiment of FIGS.

  It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.

The front view which shows the foundation constructed | assembled by the construction method which concerns on 1st Embodiment of this invention. The figure which shows FIG. 1 typically in a mechanical model. The figure which shows the state which drills a boring hole. The figure which shows a solidification material injection apparatus. The figure which shows the solidification material injection device of the type which injects a cross jet. Explanatory drawing explaining creation of the foundation by a cylindrical improvement body. The top view showing the foundation concerning a 2nd embodiment. FIG. 8 is a side view of FIG. The top view which shows the cross-shaped foundation based on 3rd Embodiment. The B arrow side view of FIG. The top view which shows the grid | lattice-like foundation which concerns on 4th Embodiment. The front view which shows 5th Embodiment. The front view which shows 6th Embodiment. The front view which shows 1 process in construction of 6th Embodiment. The front view which shows the process different from FIG. 14 in 6th Embodiment. The block diagram which shows the conventional foundation. The front view which shows 1 process in construction of 7th Embodiment. The front view which shows the process different from FIG. 17 in 7th Embodiment. The front view which shows another process of 7th Embodiment. The front view which shows the foundation and building created in 7th Embodiment. The stress-strain diagram which shows the effect | action of 7th Embodiment. The front view which shows 1 process in construction of 8th Embodiment. The front view which shows the process different from FIG. 22 in 8th Embodiment.

Explanation of symbols

GL ... Ground G ... Ground Gc ... Foundation J ... Solid jet 1 ... Building 3 ... Land liquefied sand 5 ... Liquid Stable ground 6 without fear of forming ... Boring drilling device 7, 7a ... Boring hole 8 ... Improved bodies 11, 11a, 11b ... Solidified material injection means 17 ... Solidified Material 18 ... Consolidated pile 19 ... Cross-girder-like connection wall 20 ... Grid-like connection wall 21 ... Elastic material 22 ... Plate-like body

Claims (3)

A boring hole is drilled from the ground surface (GL) through the sand ground (3) to the stable ground (5) by the boring hole drilling device (6), and the solidified material injection device ( 11, 11A) is inserted, the solidified material injection device (11, 11A) is rotated while spraying the solidified material, and is pulled up to reach the stable ground (5) in the ground. In the construction method of the foundation of the building to be constructed, the solidified material is injected from the solidified material injection device (11, 11A) from the bottom of the boring hole (11) to a predetermined depth (D) to form the lower improvement portion (8b). Construction of the foundation of a building, characterized in that, from a predetermined depth (D) to near the ground surface (GL), a solidified material and an elastic material are mixed and injected to create an upper improved portion (8b). . The construction method for a foundation of a building according to claim 1, wherein the underground improvement body is a plurality of improvement bodies (18). The construction method for a foundation of a building according to claim 1, wherein the underground improvement body is a continuous wall-like improvement body (19).

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