JP5542633B2 - Ground improvement body and horizontal strength calculation method of ground improvement body - Google Patents

Description

  The present invention relates to a ground improvement body and a horizontal strength calculation method for the ground improvement body.

  In soft ground or the like, a structure is constructed on the ground improvement body that has been improved. The ground improvement body suppresses the sliding of the foundation by the frictional resistance between the foundation of the structure and the ground improvement body, and reduces the horizontal force acting on the pile. However, when a large horizontal force acts on the ground improvement body due to seismic force or uneven earth pressure, the friction resistance force between the foundation of the structure and the ground improvement body is insufficient, and the space between the foundation and the ground improvement body slides. .

  In order to prevent this sliding, there is a choice to increase the pile diameter, but the construction cost increases. For this reason, a non-slip mechanism such as an uneven part for transmitting a shearing force or a shear key (transmission member) is provided between the foundation and the ground improvement body (Patent Document 1).

  As shown in FIG. 10, the anti-slip mechanism 108 of Patent Document 1 constructs a ground improvement body 114 between the soil slab 110 and the ground 112, and joins between the soil slab 110 and the ground improvement body 114 with an uneven portion 116. This is the configuration. The depth of the ground improvement body 114 is set to the bottom surface of the foundation footing 118, and the bottom surface of the ground improvement body 114 is in contact with the ground 112 in a plane. Further, the periphery of the soil slab 110 and the ground improvement body 114 is in contact with the foundation footing 118 in the horizontal direction.

As a result, the soil slab 110 and the ground improvement body 114 are integrated, and slides between the bottom surface of the ground improvement body 114 and the ground 112 when receiving a horizontal force during an earthquake.
That is, Patent Document 1 merely changes the sliding position between the soil slab 110 and the ground improvement body 114 and between the ground improvement body 114 and the ground 112, and uses the characteristics of the ground improvement body 114. I can't say that.

  Also, no specific calculation method is described for the horizontal strength of the ground improvement body 114 provided with the anti-slip mechanism 108.

JP 2007-321402 A

  In view of the above-described facts, an object of the present invention is to provide a slip prevention mechanism that takes advantage of the characteristics of the ground improvement body and a method for calculating the horizontal strength of the ground improvement body provided with the slip prevention mechanism.

  In the horizontal yield strength calculation method according to the first aspect of the present invention, an uneven portion is formed on the head, the structure is supported by a ground improvement body in which the protrusion is swallowed into the structure body, and the horizontal force is A method for calculating a horizontal strength of a ground improvement body, which is transmitted from a frame to the ground improvement body, wherein a slope angle of a shear fracture surface generated when the convex portion is broken by the horizontal force with respect to a horizontal plane is a shear plane slope angle. When the structure is displaced along the shear plane inclination angle α, the amount of work consumed when the structure is displaced against the gravity is added to the horizontal strength of the ground improvement body. It is characterized by that.

According to the first aspect of the present invention, the amount of work consumed when the structure is displaced against the gravity along the shear plane inclination angle α and the horizontal strength of the ground improvement body are added together to add the ground. The horizontal strength of the improved body is calculated. That is, by appropriately selecting the shear plane inclination angle α, the horizontal force at the time of the earthquake can be attenuated in the form of work consumed when the structure is displaced against the gravity.
Thereby, the burden of a ground improvement body can be reduced and the calculation method of the anti-slip | skid mechanism which utilized the characteristic of the ground improvement body can be provided.

ここに The horizontal yield strength calculation method according to the invention described in claim 2 is the horizontal yield strength calculation method according to claim 1, wherein the horizontal yield strength calculation method includes the shear plane inclination angle α and the horizontal yield strength F of the ground improvement body. From the horizontal proof stress characteristic calculation step for calculating the horizontal proof stress characteristic indicating the relationship of (α) and the horizontal proof stress characteristic, the shear plane inclination angle αp that minimizes the horizontal proof stress F (α) is obtained, And a minimum proof stress calculating step in which the horizontal proof stress F (αp) at the shear plane inclination angle αp is set as the horizontal proof stress of the ground improvement body.

here

Ｄｅ：地盤改良体の奥行き方向の有効幅（ ｍ ）
Ｌａ：地盤改良体の凸部の水平長さ（ ｍ ）
Ｈ ：地盤改良体の凸部の高さ（ ｍ ）
Ｆｃ：躯体のコンクリートのせん断強度（ｋＮ／ｍ^２）
Ｎ：地盤改良体の凸部の総数（ 個 ）
Pf: Vertical force (kN) at the frictional resistance surface between the ground improvement body and the body boundary
Ps: Vertical force (kN) on the shear resistance surface of the ground improvement body
α: Shear surface inclination angle of ground improvement body (degree)
φ: Friction angle of ground improvement body (degree)
μ: Coefficient of friction between the ground improvement body and the frame interface (-)
S: Area per shear surface of ground improvement body (m ² )

De: Effective width of the ground improvement body in the depth direction (m)
La: Horizontal length of convex part of ground improvement body (m)
H: Height of convex part of ground improvement body (m)
Fc: Shear strength (kN / m ² ) of the concrete of the frame
N: Total number of convex parts of ground improvement body ()

According to the second aspect of the invention, the horizontal proof stress F (αp) of the ground improvement body is calculated through the horizontal proof stress characteristic calculating step and the minimum proof stress calculating step.
That is, the horizontal strength of the ground improvement body can be calculated based on the weight of the structure, the strength of the ground improvement body, and the shape of the uneven portion of the head of the ground improvement body. At this time, since it is assumed in the formula (1) that there are a plurality of uneven portions, it is possible to install small uneven portions densely, improving the workability, and necessary horizontal strength F (Αp) can be secured.

Moreover, if the ratio of the horizontal length La of the convex part in the concavo-convex part, the horizontal length Lb of the concave part, and the height H of the convex part is constant, the horizontal proof stress of the ground improvement body obtained by the equation (1) is the same value. It becomes. From this, the shape of the concavo-convex portion can be changed according to the workability.
In addition, by making the size of the uneven part a dimension (about 2 to 5 times) corresponding to the shear strength ratio (about 2 to 5 times) between the uneven part and the body side concrete, the body side concrete is made bare. This also makes it possible to reduce construction costs and save labor.

  The invention according to claim 3 is the horizontal yield strength calculation method according to claim 2, wherein the horizontal yield strength characteristic calculation step, and the preset horizontal strength F (αq) at the shear plane inclination angle αq is a minimum value. Adjusting the height H of the convex part of the concavo-convex part so that the horizontal proof stress characteristic corresponding to the height H after the adjustment is calculated by the formula (1), a minimum value, And a minimum proof stress calculating step in which the horizontal proof stress F (αq) is used as the horizontal proof stress of the ground improvement body.

According to the invention described in claim 3, the height of the convex portion is set so that the horizontal proof stress F (αq) at the shear plane inclination angle αq becomes a minimum value using the horizontal proof stress characteristic calculated by the equation (1). H is adjusted. By appropriately adjusting the height H of the convex portion, the preset value of the horizontal proof stress F (αq) at the shear plane inclination angle αq can be minimized.
That is, the position of the shear fracture surface (shear surface inclination angle αq) can be set in advance at the design stage.

The invention according to claim 4 is characterized in that, in the horizontal proof stress calculation method according to claim 3, the shear surface inclination angle αq is set to 0 degree (horizontal plane).
According to invention of Claim 3, a shear fracture surface can be produced in a horizontal surface.
Thereby, the shear strength of the ground improvement body can be utilized to the maximum, and the horizontal proof stress F (αq) can be maximized.

  The invention according to claim 5 is characterized in that, in the horizontal proof stress calculation method according to claim 3, the shear surface inclination angle αq is any one within a range of 10 to 45 degrees.

According to the fifth aspect of the present invention, the shear plane inclination angle αq can be selected at any angle within the range of 10 to 45 degrees.
As a result, even if the convex portion receives a horizontal force exceeding the ultimate slip resistance force and is partially damaged, the remaining portion of the convex portion ensures a certain residual slip resistance force and the anti-slip mechanism resistance force. Can be prevented.

ここに The ground improvement body which concerns on invention of Claim 6 is a ground improvement body which forms an uneven | corrugated | grooved part in a head, makes a convex part squeeze into a housing | casing, and transmits horizontal force to the said housing | casing, The inclination angle of the shear fracture surface generated when the convex portion adjacent to the concave portion is destroyed with respect to the horizontal plane is defined as the shear surface inclination angle α, and the shear surface inclination angle α calculated by the following equation and the horizontal surface of the ground improvement body In the horizontal proof stress characteristic indicating the relationship of the proof stress F (α), the height H of the convex portion in the concavo-convex portion is set so that the horizontal proof stress F (αq) at the shear plane inclination angle αq set in advance is a minimum value. The horizontal length La of the convex portions and the total number N of the convex portions are adjusted.

here

Ｄｅ：地盤改良体の奥行き方向の有効幅（ｍ）
Ｌａ：地盤改良体の凸部の水平長さ（ｍ）
Ｈ ：地盤改良体の凸部の高さ（ｍ）
Ｆｃ：躯体のコンクリートのせん断強度（ｋＮ／ｍ^２）
Ｎ：地盤改良体の凸部の総数（個）
Pf: Vertical force (kN) at the frictional resistance surface between the ground improvement body and the body boundary
Ps: Vertical force (kN) on the shear resistance surface of the ground improvement body
α: Shear surface inclination angle of ground improvement body (degree)
φ: Friction angle of ground improvement body (degree)
μ: Coefficient of friction between ground improvement body and frame interface (-)
S: Area per one shear surface of the ground improvement body (m ² )

De: Effective width in the depth direction of ground improvement body (m)
La: Horizontal length of convex part of ground improvement body (m)
H: Height of convex part of ground improvement body (m)
Fc: Shear strength (kN / m ² ) of the concrete of the frame
N: Total number of convex parts of the ground improvement body (pieces)

According to invention of Claim 6, the uneven | corrugated | grooved part as a non-slip | skid mechanism is formed in the head of the ground improvement body, and the convex part is swallowed by the housing. Thereby, the horizontal force can be transmitted from the frame to the ground improvement body.
The horizontal proof stress F (α) of the ground improvement body is (2) when the inclination angle with respect to the horizontal plane of the shear fracture surface generated when the convex portion adjacent to the concave portion is destroyed by the horizontal force is the shear plane inclination angle α. It can be calculated by a formula.

  When the characteristic indicating the relationship between the shear surface inclination angle α and the horizontal strength F (α) of the ground improvement body is defined as the horizontal strength characteristic, the preset horizontal strength F (αq) at the shear surface inclination angle αq becomes the minimum value. As described above, the height H of the convex portions in the concave and convex portions, the horizontal length La of the convex portions, and the total number N of convex portions are adjusted.

  Thereby, the ground improvement body from which the horizontal proof stress F ((alpha) q) in the shear plane inclination-angle (alpha) q set in advance becomes the minimum value can be provided. That is, the position of the shear fracture surface (shear surface inclination angle αq) can be set in advance at the design stage.

The invention according to claim 7 is the ground improvement body according to claim 6, wherein the shear surface inclination angle αq is set to 0 degree (horizontal plane).
That is, a shear fracture surface can be generated in the horizontal plane. Thereby, the shear strength of the ground improvement body can be utilized to the maximum, and the horizontal proof stress F (αq) can be maximized.

The invention according to claim 8 is the ground improvement body according to claim 6, wherein the shear surface inclination angle αq is any angle within a range of 10 to 45 degrees.
That is, the shear plane inclination angle αq can be selected at any angle within the range of 10 to 45 degrees. Thereby, even if the convex portion receives a horizontal force exceeding the ultimate slip resistance force and is partially damaged, the remaining portion of the convex portion ensures a certain residual slip resistance force, and the anti-slip mechanism Can prevent a sudden drop in the resistance.

  The invention according to claim 9 is the ground improvement body according to any one of claims 6 to 8, wherein the ground improvement body is configured as a wall body in which columnar improvement pillars having improved ground are wrapped with each other. The concave portion of the concavo-convex portion is formed in a groove shape that crosses the head in the width direction of the wall body, and the direction in which the concave portion crosses has an angle with respect to the length direction of the head in plan view. It is characterized by crossing.

According to invention of Claim 9, the ground improvement body is comprised as a wall body which mutually wrapped the improvement pillar. Further, the concave portion in the concavo-convex portion is formed in a groove shape that crosses the head portion in the width direction of the wall body, and the direction in which the concave portion crosses intersects with the length direction of the head portion at an angle in plan view. ing.
Thereby, slip resistance can be exhibited also in the out-of-plane direction of the ground improvement body.

  The invention according to claim 10 is the ground improvement body according to any one of claims 6 to 8, wherein the wrap portion where the improvement pillar is wrapped is orthogonal to the length direction of the wall body. And the said recessed part formed in the rectangular shape is arrange | positioned, It is characterized by the above-mentioned.

  According to invention of Claim 10, the rectangular recessed part is formed in the lap | wrap part of the improvement pillar. Thereby, the excavation and removal work of the uneven part formed on the head of the ground improvement body can be saved. Further, the horizontal proof stress can be determined from the depth and width of the rectangular recess to be constructed, and the anti-slip mechanism can be constructed with the minimum necessary excavation amount.

  Invention of Claim 11 is the ground improvement body of any one of Claims 6-8, In the center part of the said improvement pillar, the said recessed part formed in the column shape is the said wall body. It is characterized by being provided at a predetermined depth from the head.

According to invention of Claim 11, a recessed part is formed in the center part of an improvement pillar, and the recessed part is formed in the column shape by predetermined depth from the head of a wall body.
That is, by using a core cutter, a cylindrical recess can be easily constructed, and the workability is improved.

The invention according to claim 12 is characterized in that in the ground improvement body according to any one of claims 6 to 11, the depths of the adjacent concave portions are made different.
According to the eleventh aspect of the present invention, the depths of the adjacent recesses are different from each other. Thereby, it can prevent that a shear fracture surface generate | occur | produces continuously in a horizontal direction, and can increase the horizontal proof stress of a ground improvement body.

  The invention according to claim 13 is the ground improvement body according to any one of claims 6 to 12, wherein the concave-convex portion is formed on a head of the ground improvement body in a length direction of the wall body. It is characterized by being formed in plural.

According to the invention described in claim 13, the ground improvement body satisfies the shape ratio (ratio of the height H of the protrusion to the horizontal length La, etc.) of the unevenness determined from the horizontal force at the time of the earthquake. A plurality of concavo-convex portions are formed in the head portion of the head in the length direction of the wall.
Thereby, the surface area which a frame and a ground improvement body contact can be enlarged. Moreover, since the amount of excavation of the head of the ground improvement body can be reduced, the amount of frame concrete can be reduced.

  The invention described in claim 14 is the ground improvement body according to any one of claims 6 to 13, wherein fibers for reinforcing toughness are mixed in a head of the ground improvement body. It is said.

  In the invention described in claim 14, fibers for reinforcing toughness are mixed in the head of the ground improvement body. Thereby, the toughness of the head where local stress concentrates can be reinforced. In addition, earthquake resistance can be improved. In addition, a uniform horizontal force can be transmitted to the lower portion of the ground improvement body that is not reinforced with a fiber by a load dispersion effect.

  Since this invention is set as the said structure, the calculation method of the horizontal strength of the ground improvement body which provided the antiskid mechanism which utilized the characteristic of the ground improvement body, and the antiskid mechanism can be provided.

It is sectional drawing which shows the basic structure of the anti-slip | skid function for demonstrating the calculation method of the ground improvement body which concerns on the 1st Embodiment of this invention, and the horizontal strength characteristic figure of a ground improvement body. It is sectional drawing which shows the basic composition of the ground improvement body which concerns on the 2nd Embodiment of this invention, and the horizontal strength characteristic figure of a ground improvement body. It is a schematic diagram which shows the horizontal proof stress characteristic figure of the ground improvement body which concerns on the 3rd Embodiment of this invention, and the resistance force of a ground improvement body. It is sectional drawing which shows the position of the shear fracture surface of the ground improvement body which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the basic composition of the ground improvement body which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the basic composition of the ground improvement body which concerns on the 5th Embodiment of this invention. It is sectional drawing which shows the basic composition of the ground improvement body which concerns on the 6th Embodiment of this invention. It is sectional drawing which shows the basic composition of the ground improvement body which concerns on the 7th Embodiment of this invention. It is sectional drawing which shows the mixing condition of the fiber mixed in the ground improvement body which concerns on the 8th Embodiment of this invention. It is a figure which shows the basic composition of the ground improvement body of a prior art example.

(First embodiment)
The calculation method of the ground improvement body which concerns on 1st Embodiment is a calculation method of the horizontal proof stress F of the anti-slip | skid mechanism 10 shown to sectional drawing of FIG. The anti-slip mechanism 10 is a joint portion between the ground improvement body 12 having an uneven portion 24 formed on the head and a housing 16 of a structure (not shown) that enters the recess 22, and the horizontal force R at the time of an earthquake is This is transmitted to the ground improvement body 12 via the part 24.

  Here, the ground improvement body 12 mixes and stirs excavated soil and cement milk while excavating the original ground with an auger (not shown) to form a column body, and wraps the outer peripheral portions of the column body to form a wall shape. This is the configuration. The horizontal strength per unit area of the ground improvement body 12 is smaller than the horizontal strength per unit area of the concrete used for the frame 16 because the ground improvement body 12 contains excavated soil.

The head of the ground improvement body 12 is provided with a concavo-convex portion 24 in which a plurality of convex portions 14 (width La) having a depth H1 are continuously formed across the concave portion 22 (width Lb). A casing 16 is formed on the concavo-convex portion 24, and the convex portion 14 is encased in the concrete of the casing 16.
In this configuration, when the convex portion 14 is broken by the horizontal force R at the time of the earthquake, the ground improvement body 12 is broken at the position of the shear fracture surface 18 that forms an angle α with the horizontal plane 20. The horizontal proof stress at this time is the horizontal proof stress at the position of the shear fracture surface 18 of the ground improvement body 12 and the work consumed when the structure is displaced along the shear plane inclination angle α against gravity. Calculated by adding.

That is, by destroying the ground improvement body 12 at the position of the shear plane inclination angle α, the horizontal force during the earthquake is attenuated in the form of work consumed when the structure is displaced against gravity. Can do.
As a result, the burden on the ground improvement body 12 is reduced, and a method for calculating the anti-slip mechanism that makes use of the characteristics of the ground improvement body 12 can be provided.

ここに Here, the amount of work consumed when the structure is displaced against the gravity can be determined by the mass of the structure and the shear plane inclination angle α. Moreover, the horizontal proof stress F of the anti-slip | skid mechanism 10 can be calculated in the following procedure.
First, a horizontal proof stress characteristic calculation step is executed. When the horizontal proof stress of the ground improvement body at the shear surface inclination angle α is F (α), the horizontal proof stress characteristic P indicating the relationship between the shear surface inclination angle α and the horizontal proof strength F (α) is calculated by the following equation.

here

Ｄｅ：地盤改良体の奥行き方向の有効幅（ｍ）
Ｌａ：地盤改良体の凸部の水平長さ（ｍ）
Ｈ ：地盤改良体の凸部の高さ（ｍ）
Ｆｃ：躯体のコンクリートのせん断強度（ｋＮ／ｍ^２）
Ｎ：地盤改良体の凸部の総数（個） Pf: Vertical force (kN) at the frictional resistance surface between the ground improvement body and the body boundary
Ps: Vertical force (kN) on the shear resistance surface of the ground improvement body
α: Shear surface inclination angle of ground improvement body (degree)
φ: Friction angle of ground improvement body (degree)
μ: Coefficient of friction between ground improvement body and frame interface (-)
S: Area per one shear surface of the ground improvement body (m ² )

De: Effective width in the depth direction of ground improvement body (m)
La: Horizontal length of convex part of ground improvement body (m)
H: Height of convex part of ground improvement body (m)
Fc: Shear strength (kN / m ² ) of the concrete of the frame
N: Total number of convex parts of the ground improvement body (pieces)

  FIG. 1B shows the result of calculating the value of the horizontal strength characteristic F (α) by the above formula using the physical property values of the ground improvement body 12. The horizontal axis is the shear plane inclination angle α (degrees), and the vertical axis is the horizontal proof stress F (α) (kN).

  The calculated horizontal strength characteristic P1 is indicated by a solid line. The shear plane inclination angle α shows a high value in the vicinity of the horizontal (about 0 to 10 degrees) and the vicinity of the vertical (about 65 to 75 degrees), and a low value in the middle range. It can be seen from the calculated horizontal proof stress characteristic P1 that it is easily broken in an intermediate range.

  Next, a minimum yield strength calculation step is executed. The procedure obtains a position where the horizontal proof stress F (α) is the smallest in the horizontal proof stress characteristic P1 shown in FIG. Thereafter, the shear plane inclination angle αp at the position where the extracted horizontal proof stress F (α) is the smallest is obtained. At the same time, the value of the horizontal proof stress F (αp) at the shear plane inclination angle αp is obtained and used as the horizontal proof stress F (α) of the ground improvement body 12.

Specifically, the minimum value of the horizontal strength F (α) of the horizontal strength property P1 is a position surrounded by a circle M1. The shear plane inclination angle αp at the position surrounded by the circle M1 is 28 degrees from the scale on the horizontal axis, and the horizontal proof stress F (α) at the circle M1 is 120,000 (kN) from the scale on the vertical axis.

Through the above-described procedure, the horizontal proof stress F is calculated as 120,000 (kN). Here, the above equation can be obtained by the following procedure.

ここに、 The vertical force P (kN) acting on the head of the ground improvement body 12 is the sum of the shared vertical stress Ps in the fracture region As (m ² ) due to friction and the shared vertical stress Pf in the fracture region Af (m ² ) due to shear. And can be obtained by the following procedure.
P = Ps + Pf

here,

P: Vertical force (kN) of ground improvement body (in-plane wall) head
Pf: Vertical force (kN) at the frictional resistance surface between the ground improvement body and the body boundary
Ps: Vertical force (kN) on the shear resistance surface of the ground improvement body
La: Horizontal length of ground improvement body convex part (m)
Lb: Horizontal length of ground improvement body recess (m)
Lc: Horizontal length of the shear failure area of the ground improvement body (m)
H1: Height of ground improvement body convex part (m)

ここで、地盤改良体１２のせん断強度τｆは、次式で表わされる。

The horizontal strength F of the head of the ground improvement body 12 is represented by the sum of the frictional resistance Ff at the boundary surface between the frame 16 and the ground improvement body 12 and the shear fracture resistance Fs of the convex portion 14 of the ground improvement body 12. It is.
F = Ff + Fs
The frictional resistance force Ff and the shear fracture resistance force Fs can be expressed by the following equations.

Here, the shear strength τf of the ground improvement body 12 is expressed by the following equation.

From the above, the horizontal proof stress F (α) of the ground improvement body 12 (in-plane wall) is the above-described equation (3).
Further, the horizontal yield strength F (α) can be determined by obtaining the shear plane direction angle α of the ground improvement body 12 when the horizontal yield strength F (α) is minimized by using the equation (3). .

  As described above, according to the present embodiment, the horizontal proof stress F (α) of the ground improvement body 12 can be calculated through the horizontal proof stress characteristic calculating step and the minimum proof stress calculating step. That is, the horizontal strength F (α) of the ground improvement body 12 is determined based on the building weight, the strength of the ground improvement body 12, the shape of the uneven portion 24 of the head of the ground improvement body 12, and the like. At this time, as will be described later, the presence of a plurality of concave and convex portions 24 is assumed in the expression (3). That is, by installing the small uneven portions 24 densely, it is possible to improve the workability of the uneven portions 24 and to secure the necessary horizontal proof stress F.

  Moreover, if the ratio of the horizontal length La of the convex part 14 in the uneven | corrugated | grooved part 24, the horizontal length Lb of the recessed part 22, and the height H of the convex part 14 is constant, the ground improvement body 12 obtained by (3) Formula. The horizontal proof stress F (α) is the same value. From this, the shape of the uneven | corrugated | grooved part 24 can be selected according to construction property.

  Moreover, the dimension which made the dimension of the uneven | corrugated | grooved part 24 respond | correspond to the shear strength ratio (about 2 to 5 times) of the uneven | corrugated | grooved part 24 and the housing 16 side concrete, ie, the horizontal length La of the convex part 14, is the housing 16 side concrete. By setting it to about 2 to 5 times the (horizontal length Lb of the concave portion 22), it is possible to make the frame 16 side concrete straight, and it is possible to reduce the construction cost and save labor.

(Second Embodiment)
As shown in the cross-sectional view of FIG. 2, the ground improvement body 28 according to the second embodiment is provided with an uneven portion 52 at the head, and constitutes an anti-slip mechanism 34 with the housing 36.

The ground improvement body 28 is different from the ground improvement body 12 described in the first embodiment only in the shape of the uneven portion 52. That is, a plurality of convex portions (width Ld) having a depth H2 are continuously formed on the head of the ground improvement body 28 with the concave portion (width Lf) interposed therebetween. A casing 36 is formed on the concavo-convex portion 52, and the convex portion 48 is encased in the concrete of the casing 36. The horizontal force R at the time of an earthquake is transmitted to the housing 36 through the uneven portion 52.

  In the uneven portion 52, the convex portion 48 is broken from the lower end portion of the surface adjacent to the concave portion 50 when a horizontal force R greater than the breaking strength of the ground improvement body 28 is applied. The shear fracture surface 18 at this time is formed so as to be generated from the lower end of the convex portion 14 at a position parallel to the horizontal plane 20 (angle α = 0).

Specifically, the horizontal strength characteristic P2 indicating the relationship between the shear plane inclination angle α and the horizontal strength F (α) of the ground improvement body 28 is calculated by the above-described equation (3), and the calculation result is shown in FIG. The dimension of the concavo-convex portion 52 is determined so as to have the characteristic P2 indicated by the solid line.

As a result, in the horizontal proof stress characteristic P2, the shear plane inclination angle α when the horizontal proof stress F (α) is the smallest is a position (angle α = 0) parallel to the horizontal plane 20 indicated by the arrow M2. And the horizontal proof stress F ((alpha)) at this time will be 180000 (kN) from the scale of a vertical axis | shaft.
Thus, by setting the shear plane inclination angle α to a position parallel to the horizontal plane 20, the shear strength of the ground improvement body 28 can be utilized to the maximum, and the horizontal proof stress F (α) can be maximized.

  The configuration of the joint structure 34 between the other ground improvement body 28 and the frame 36 is the same as the joint structure 10 described in the first embodiment, and the description thereof is omitted.

Next, a method for calculating the horizontal strength of the ground improvement body according to the second embodiment will be described.
First, a horizontal proof stress characteristic calculation step is executed. This step is the same as that of the first embodiment described above, and a description thereof will be omitted. By this step, a horizontal proof stress characteristic P2 indicated by a solid line in FIG.

Next, the uneven | corrugated | grooved part adjustment step is performed. That is, when the horizontal strength characteristic P2 calculated in the horizontal strength characteristic calculation step is not set to a minimum value at a preset position where the shear plane inclination angle α is parallel to the horizontal plane 20 (angle α = 0). The height H2 of the convex portion 48 of the concave and convex portion 52 is adjusted so as to be the minimum value. And the horizontal proof stress characteristic P2 corresponding to the height H2 of the convex part 48 after adjustment is again calculated by Formula (3).
This step is repeated until the flat proof stress characteristic P2 reaches a minimum value at a position where the shear plane inclination angle α is set in parallel with the horizontal plane 20 (angle α = 0).

Finally, the minimum yield strength calculation step is executed. That is, the horizontal proof stress F (α) at the position where the shear plane inclination angle α is parallel to the horizontal plane 20 is defined as the horizontal proof stress F (α) of the ground improvement body 12.
Thereby, the shear fracture surface 18 can be generated in a plane parallel to the horizontal plane 20. Moreover, the shear strength of the ground improvement body 28 can be utilized to the maximum, and the horizontal proof stress F (α) can be maximized. Further, the position of the shear fracture surface 18 (shear surface inclination angle αq) can be set in advance at the design stage.

(Third embodiment)
A ground improvement body (not shown) according to the third embodiment is different from the ground improvement body 28 according to the second embodiment shown in FIG. 2 only in the shape of the uneven portion 52. Hereinafter, the difference will be mainly described.

The uneven portion (not shown) has a shape having the horizontal strength characteristic P3 shown in FIG. That is, the minimum value in the horizontal proof stress characteristic P3 is set to any angle within the range of the shear plane inclination angle α of 10 to 45 degrees indicated by the arrow M3.

As a result, even if the convex portion receives a horizontal force exceeding the ultimate slip resistance force and is destroyed at the position of the shear plane inclination angle α (within a range of 10 to 45 degrees), the angle is partially damaged at any angle. The Rukoto.
As a result, as shown in the schematic diagram of FIG. 3B, the relationship between the horizontal displacement and the resistance force is as follows. Here, the horizontal axis represents horizontal displacement and the vertical axis represents resistance.

  The solid line A shows the characteristic of horizontal fracture in which the position of the shear plane inclination angle α is parallel to the horizontal plane 20. Although a large resistance force RA is temporarily generated at the initial stage of the horizontal displacement, the resistance force rapidly decreases after the convex portion is destroyed.

  On the other hand, as shown by the broken line B, the initial maximum resistance force RB of the horizontal displacement is lower than the resistance force RA by controlling to leave a certain amount of residual slip resistance force, but even after the convex portion is destroyed It is possible to leave a mountain-shaped mechanical engagement between the housing and the improved body. As a result, the remaining portion of the convex portion ensures a certain amount of residual slip resistance, and can prevent a sudden drop in the resistance of the anti-slip mechanism.

Next, a method for calculating the horizontal strength of the ground improvement body described in the first development example will be described.
First, a horizontal proof stress characteristic calculation step is executed. This step is the same as that of the first embodiment described above, and a description thereof will be omitted. In this step, the horizontal strength characteristic P3 is calculated.

  Next, the uneven | corrugated | grooved part adjustment step is performed. That is, when the horizontal strength characteristic P3 calculated in the horizontal strength characteristic calculation step is not the minimum value at the preset shear plane inclination angle α, the horizontal strength characteristic P3 is set at the preset shear plane inclination angle α. The height H2 of the convex portion 14 in the concave and convex portion 24 is adjusted so as to be the minimum value. And the horizontal yield strength characteristic P3 corresponding to the height H of the convex part 14 after adjustment is calculated by (3) Formula.

This step is repeated until the flat proof stress characteristic P3 reaches a minimum value at a preset shear plane inclination angle α.
Finally, the minimum yield strength calculation step is executed. That is, the horizontal proof stress F (α) set to the minimum value is set as the horizontal proof stress F (α) of the ground improvement body 12.

  With the above procedure, the horizontal strength F (α) of the ground improvement body can be calculated.

Next, advantages of forming a plurality of uneven portions will be described.
As shown in FIG. 4A, the conventionally used large concave portion 70 is provided with a protrusion 74 into which concrete has entered from the side of the housing 72, and ensures resistance. In this method, if the recesses 70 are provided close to each other, there is a problem in that the resistance per unit decreases, and it is necessary to provide the large recesses 70 at sparse intervals. In such a case, when the ultimate resistance is exceeded, passive fracture occurs around the recess 70 of the ground improvement body 74, and at the same time, a compressive fracture 92 due to stress concentration occurs. As a result, the resistance force rapidly decreases.

  On the other hand, as shown in FIG. 4B, in the present embodiment, by repeatedly providing the concave portions 76 and the convex portions 78, the horizontal force R can be dispersed in the plurality of concave portions 76 and the convex portions 78. Compressive fracture due to stress concentration can be prevented, and mountain-like engagement can be maintained. As a result, the residual stress can be increased.

  Thereby, at the end of a large earthquake, the head of the ground improvement body 90 can cause a shear fracture at the position of the solid line 94 to absorb energy. In addition, it is possible to provide an anti-slip mechanism with increased residual resistance so as to ensure resistance against aftershocks after a large earthquake.

Furthermore, the surface area which the housing 16 and the ground improvement body 12 contact can be enlarged. Moreover, since the amount of excavation of the head of the ground improvement body 12 can be reduced, the amount of concrete frame can be reduced.

(Fourth embodiment)
As shown in the cross-sectional views of FIGS. 5A and 5B, the ground improvement body 30 according to the fourth embodiment has an uneven portion 31 at the head of the ground improvement body 30. 5B is a side view of the anti-slip mechanism 88, and FIG. 5A is a cross-sectional view taken along line XX of FIG. 5B.

The anti-slip mechanism 88 includes a ground improvement body 30 and a frame 86, and the ground improvement body 30 is configured as a wall body obtained by wrapping columnar ground improvement bodies obtained by improving the original ground.

The recess 32 of the uneven portion 31 of the ground improvement body 30 is formed in a groove shape that crosses the head in the width direction of the wall body. Further, the concrete of the casing 86 enters the recess 32, and the direction in which the recess 32 crosses intersects the longitudinal direction of the head with an angle β in plan view.

  Thereby, the horizontal force R at the time of an earthquake is transmitted from the frame 86 to the ground improvement body 30. At this time, although the rigidity of the resistance force to the horizontal force R in the out-of-plane direction of the ground improvement body 30 is low, the foundation slab of the frame 86 and the ground improvement body 30 are integrated to be surrounded by the wall body of the ground improvement body 30. Therefore, it can be expected to prevent deformation of the ground and prevent liquefaction. In the present embodiment, the horizontal resistance force can be expressed in the out-of-plane direction simultaneously with the horizontal resistance force in the in-plane direction.

Other configurations are the same as those of the second embodiment, and a description thereof will be omitted.
As shown in FIG. 5C, the angle β of the recess 32 is not limited to an acute angle, and the acute angle β and the obtuse angle γ may be combined alternately. Furthermore, only the obtuse angle γ may be used.

(Fifth embodiment)
As shown in the cross-sectional view of FIG. 6, the ground improvement body 40 according to the fifth embodiment has an uneven portion 45 on the head of the ground improvement body 40. 6B is a side view of the anti-slip mechanism 96, and FIG. 6A is a cross-sectional view taken along line XX of FIG. 6B.

The anti-slip mechanism 96 includes a ground improvement body 40 and a frame 43, and the ground improvement body 40 is configured as a wall body in which the outer peripheral portions of columnar ground improvement bodies obtained by improving the original ground are wrapped together.
In the lap portion where the outer peripheral portion is wrapped, a concave portion 42 formed in a rectangular shape is arranged in a direction orthogonal to the length direction of the wall body of the ground improvement body 40. The concrete of the frame 43 enters the recess 42 and transmits the horizontal force R at the time of the earthquake from the frame 43 to the ground improvement body 40.

Thereby, the excavation and removal work of the uneven part formed on the head of the ground improvement body 40 can be saved. Further, the horizontal proof stress F can be determined by the depth D, width W, and thickness T of the rectangular recess to be constructed, and the anti-slip mechanism 96 can be constructed with the minimum necessary amount of excavation.
Other configurations are the same as those of the second embodiment, and a description thereof will be omitted.

(Sixth embodiment)
As shown in the cross-sectional view of FIG. 7, the ground improvement body 44 according to the sixth embodiment has an uneven portion 49 at the head of the ground improvement body 44. 7B is a side view of the anti-slip mechanism 98, and FIG. 7A is a cross-sectional view taken along the line XX of FIG. 7B.

The anti-slip mechanism 98 includes a ground improvement body 44 and a frame 48, and the ground improvement body 44 is configured as a wall body in which outer peripheral portions of columnar ground improvement bodies obtained by improving the original ground are wrapped together. An uneven portion 49 is formed at the head of the ground improvement body 44, and a concave portion 46 formed in a columnar shape is provided at a depth D2 from the head of the wall body at the center of the columnar ground improvement body 44. ing. The concrete of the frame 48 enters the recess 46, and the horizontal force R at the time of the earthquake is transmitted from the frame 48 to the ground improvement body 44.

In this way, by making the recess 46 of the anti-slip mechanism 98 cylindrical, a dedicated instrument called a core cutter can be used even when the ground improvement body 44 is formed with high strength. Thus, the cylindrical recess 46 can be constructed to improve the workability.
Other configurations are the same as those of the second embodiment, and a description thereof will be omitted.

(Seventh embodiment)
As shown in the cross-sectional view of the anti-slip mechanism 66 in FIG. 8, the ground improvement body 54 according to the seventh embodiment has an uneven portion 60 on the head of the ground improvement body 54. The anti-slip mechanism 66 includes a ground improvement body 54 and a frame 68, and the ground improvement body 54 is configured as a wall body in which the outer peripheral portions of columnar ground improvement bodies obtained by improving the original ground are wrapped together. It is joined to the concrete with the uneven portion 60.

The concave / convex portion 60 has different depths of the concave portions 58 and 62 formed on both sides of the convex portion 56. That is, a concave portion 58 having a depth H3 is formed at one end portion of the convex portion 56, and a concave portion 62 having a depth H4 shallower than the depth H3 is formed at the other end portion.

As a result, the shear fracture surface 64 generated at the convex portion 56 includes a shear fracture surface 64 generated at the end portion on the concave portion 58 side and a shear fracture surface 64 generated on the end portion on the concave portion 62 side, as indicated by a broken line 64. However, it becomes the characteristic which continues with an angle on the way.

Thereby, it can prevent that the shear fracture surface 64 generate | occur | produces linearly in a horizontal direction, and can increase the horizontal proof stress F of the ground improvement body 54. FIG.
Other configurations are the same as those of the second embodiment, and a description thereof will be omitted.

(Eighth embodiment)
The ground improvement body which concerns on 8th Embodiment is the structure by which the fiber which reinforces toughness was mixed in the head of the ground improvement body 12 shown in FIG. The appearance and shape are the same as those of the ground improvement body 12 described above, and illustration and description thereof are omitted, and the description will focus on fibers that are different points.

  As shown in FIG. 9, by mixing the fiber 100 into the ground improvement body 12, the shear fracture surface 106 is reinforced by the frictional resistance of the fiber 100.

  The fiber 100 mixed to reinforce the shear fracture surface 106 preferably has mechanical properties with a breaking strength of 200 to 1200 MPa and a Young's modulus of 2 to 15 GPa. For example, polypropylene fiber is applicable.

Further, the diameter of the fiber 100 is preferably within a range of 10 to 50 μm. This is because a certain amount of size is necessary to sufficiently ensure the contact between the ground improvement body 12 and the fiber 100. On the other hand, if the diameter of the fiber 100 becomes too large, the fiber 100 is bent to each other. This is because the size is limited because it becomes difficult to intertwine.

  In addition, when the shape of the fiber 100 is a straight line, even if the diameter is an appropriate size, the fibers 100 are not entangled with each other, and a sufficiently large frictional resistance cannot be obtained, as shown in FIG. As shown, it is desirable to mix fibers 100 and fibers 100 so that they are intertwined with each other.

Thereby, a sufficiently large frictional resistance can be applied between the ground improvement body 12 and the fiber 100. By this frictional resistance, generation of the fracture surface 106 on the surface of the ground improvement body 12 and growth of the fracture surface 106 can be suppressed. That is, the toughness of the head where local stress is concentrated can be reinforced. In addition, earthquake resistance can be improved. Furthermore, a uniform horizontal force can be transmitted to the lower part of the ground improvement body in which the fibers 100 are not reinforced by the load dispersion effect.

  Other configurations are the same as those of the second embodiment, and a description thereof will be omitted.

DESCRIPTION OF SYMBOLS 10 Anti-slip mechanism 12 Ground improvement body 14 Convex part 16 Housing 18 Shear fracture surface 20 Horizontal surface 22 Concave part 24 Concavity and convexity part 28 Ground improvement body 104 Fiber

Claims (14)

An uneven portion is formed in the head, the structure is supported by a ground improvement body in which the convex portion is swallowed into the structure body, and horizontal force is transmitted from the body to the ground improvement body. Yield calculation method,
When the horizontal force causes the inclination angle of the shear fracture surface generated when the convex portion is destroyed with respect to the horizontal plane to be the shear surface inclination angle α, and when the structure is displaced along the shear surface inclination angle α, A horizontal strength calculation method for adding a work amount consumed when a structure is displaced against gravity to a horizontal strength of the ground improvement body. The calculation method of the horizontal proof stress is:
A horizontal yield characteristic calculating step for calculating a horizontal yield characteristic indicating the relationship between the shear plane inclination angle α and the horizontal yield strength F (α) of the ground improvement body, according to the following equation:
The shear surface inclination angle αp that minimizes the horizontal strength F (α) is obtained from the horizontal strength characteristics, and the horizontal strength F (αp) at the shear surface inclination angle αp is defined as the minimum horizontal strength of the ground improvement body. Yield calculation step,
The horizontal proof stress calculation method of Claim 1 which has these.

Where Pf: vertical force (kN) on the frictional resistance surface between the ground improvement body and the body boundary
Ps: Vertical force (kN) on the shear resistance surface of the ground improvement body
α: Shear surface inclination angle of ground improvement body (degree)
φ: Friction angle of ground improvement body (degree)
μ: Coefficient of friction between ground improvement body and frame interface (-)
S: Area per one shear surface of the ground improvement body (m ² )

De: Effective width in the depth direction of ground improvement body (m)
La: Horizontal length of convex part of ground improvement body (m)
H: Height of convex part of ground improvement body (m)
Fc: Shear strength (kN / m ² ) of ground improvement concrete
N: Total number of convex parts of the ground improvement body (pieces) The horizontal yield strength calculating step;
The height H of the convex portion of the concavo-convex portion is adjusted so as to correspond to the height H after adjustment so that the horizontal proof stress F (αq) at a preset shear plane inclination angle αq is a minimum value. An uneven portion adjusting step for calculating the horizontal proof stress characteristic by the equation (1),
A minimum proof stress calculating step in which the horizontal proof stress F (αq) set as the minimum value is a horizontal proof stress of the ground improvement body;
The horizontal proof stress calculation method of Claim 2 which has these. The horizontal proof stress calculation method according to claim 3, wherein the shear plane inclination angle αq is set to 0 degree (horizontal plane). The horizontal proof stress calculation method according to claim 3, wherein the shear plane inclination angle αq is any angle within a range of 10 to 45 degrees. Forming a concavo-convex portion on the head, and squeezing the convex portion into the housing to transmit a horizontal force to the housing;
The shear surface inclination angle α calculated by the following equation (2) is defined as the inclination angle α of the shear fracture surface with respect to the horizontal plane generated when the convex portion adjacent to the concave portion is destroyed by the horizontal force. And the horizontal proof stress indicating the relationship between the horizontal proof strength F (α) of the ground improvement body and the uneven portion so that the horizontal proof strength F (αq) at the shear plane inclination angle αq is set to a minimum value. The ground improvement body in which the height H of the said convex part in H, the horizontal length La of the said convex part, and the total number N of the said convex part are adjusted.

here,
Pf: Vertical force (kN) at the frictional resistance surface between the ground improvement body and the body boundary
Ps: Vertical force (kN) on the shear resistance surface of the ground improvement body
α: Shear surface inclination angle of ground improvement body (degree)
φ: Friction angle of ground improvement body (degree)
μ: Coefficient of friction between ground improvement body and frame interface (-)
S: Area per one shear surface of the ground improvement body (m ² )

De: Effective width in the depth direction of ground improvement body (m)
La: Horizontal length of convex part of ground improvement body (m)
H: Height of convex part of ground improvement body (m)
Fc: Shear strength (kN / m ² ) of ground improvement concrete
N: Total number of convex parts of the ground improvement body (pieces) The ground improvement body according to claim 6, wherein the shear plane inclination angle αq is 0 degree (horizontal plane). The ground improvement body according to claim 6, wherein the shear surface inclination angle αq is any angle within a range of 10 to 45 degrees.   The ground improvement body is configured as a wall body in which columnar improvement pillars having improved ground are wrapped together, and the concave portion of the uneven portion is a groove that crosses the head of the ground improvement body in the width direction of the wall body. The direction which the said recessed part crosses the said head is formed in shape, and cross | intersects at an angle with respect to the length direction of the said wall body in planar view. Ground improvement body.   9. The concave portion formed in a rectangular shape is disposed in the wrap portion where the improved pillar is wrapped, and is orthogonal to the length direction of the wall body. Ground improvement body.   The ground improvement according to any one of claims 6 to 8, wherein the recess formed in a columnar shape is provided at a predetermined depth from a head of the wall body at a center portion of the improvement pillar. body.   The ground improvement body of any one of Claims 6-11 which varied the depth of the said adjacent recessed part.   The ground improvement body of any one of Claims 6-12 in which the said uneven | corrugated | grooved part is formed in multiple in the length direction of the said wall body in the head of the said ground improvement body.   The ground improvement body of any one of Claims 6-13 in which the fiber which reinforces toughness is mixed in the head of the ground improvement body.

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