JP5296585B2 - Soil cement improved structure and piled raft foundation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the joint strength of a joint part between a foundation part and a soil-cement improvement body. <P>SOLUTION: The soil-cement improvement body 12 is continuously constructed in the ground 36. The soil-cement improvement body 12 is a wall body of a cylindrical column body and formed with recesses and projections 12S of circular arc shape at both side faces of the wall body. The foundation part 14 of a structure is constructed around a head 12H of the soil-cement improvement body 12, and a foundation beam 22 of the foundation part 14 is supported by a top part S1. The foundation part 14 is constituted to construct a foundation slab 23 on the ground 36 and to provide a floor slab 21 through the foundation beam 22. The periphery of the head 12H is excavated in a width dimension W and a depth dimension H, and the soil-cement improvement body 12 and the foundation slab 23 are joined with concrete 27. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

    The present invention relates to an improved structure of soil cement and a piled raft foundation.

  In soft ground and ground where liquefaction is expected, the foundation of the structure is supported by a direct foundation that is intended to improve soft ground and prevent liquefaction by improving the ground such as cement solidifying agent. Pile foundations are commonly used.

In recent years, as a rational foundation type, the application of piled raft foundations that use both direct foundations and pile foundations has been increasing. Although it has come to be seen when combined with piles, the horizontal force at the time of earthquake is currently designed only with pile foundations.
Under such circumstances, there has been proposed a technique that does not require a wide range of ground improvement and that causes the ground improvement body (soil cement improvement body) to bear a horizontal force during an earthquake (Patent Document 1).

  As shown in FIG. 11, the foundation structure 80 described in Patent Document 1 is supported by a pile 88 that reaches the support layer 86 in the structure 84 constructed on the ground 82 that may be liquefied. And the horizontal force which acts on the structure 84 at the time of an earthquake is transmitted to the non-liquefaction layer 83 through the ground improvement body 90. Here, the ground improvement body 90 has a hollow cylindrical shape and a depth at which the wall reaches the non-liquefaction layer 83. Thereby, the horizontal force which the pile 88 bears is reduced, without requiring the ground improvement of a wide range.

However, in the foundation structure 80, since the bottom surface of the structure 84 and the ground improvement body 90 are not joined together, slip occurs when the horizontal force is large, and the horizontal force that the ground improvement body 90 can no longer bear is generated by the pile 88. Have to bear. As a result, the cross-sectional area of the pile 88 cannot be reduced.
In order to solve this problem, techniques for eliminating slippage between the foundation and the ground improvement body have been proposed (Patent Documents 2 and 3).

  As shown in FIG. 12, in the joining method described in Patent Document 2, the protrusion 94 provided on the bottom surface of the foundation of the structure 84 is inserted into the recess on the top surface of the ground improvement body 91, and the horizontal movement is restricted. ing. Thereby, the horizontal force at the time of an earthquake is transmitted to the ground improvement body 91 via the junction part of a projection part and a recessed part. Further, the pile head of the pile 88 is not joined to the bottom surface of the structure 84. Thereby, the pile 88 bears only the vertical load of the structure 84, and the ground improvement body 91 bears all the horizontal force at the time of an earthquake.

  However, in the joining method described in Patent Document 2, since a hole is made in the head of the ground improvement body 91 and the protrusion 94 is inserted, a cross-sectional defect occurs in the ground improvement body 91 and the head of the ground improvement body 91 is damaged. There is a fear. For this reason, the ground improvement body 91 may not be able to appropriately bear the horizontal force at the time of the earthquake.

  As shown in FIG. 13, the joining method described in Patent Document 3 has a configuration in which the bottom surface of the foundation of the structure 84 and the top surface of the ground improvement body 92 are joined by a joining member. That is, the ground improvement body 92 and the foundation portion are joined by the cage wire 98 (FIG. 13B) or the H steel 99 with stud (FIG. 13C) which is a joining member. In addition, the pile head of the pile 89 is joined to the foundation bottom surface of the structure 84 by the pile head joining rebar 96. At this time, the joint portion is not fixed with concrete but is semi-rigid. Thereby, the ground improvement body 92 bears most of the horizontal force at the time of an earthquake.

  However, in the joining method described in Patent Document 3, since the ground improvement body 92 and the foundation portion are joined by the car reinforcement 98 or the H steel 99 with studs, the car reinforcement 98 or the H steel 99 with studs is connected to the ground improvement body 92. There is a risk of getting out of it. For this reason, the ground improvement body 92 may not be able to properly bear the horizontal force during an earthquake.

JP-A-6-294137 JP 2005-307594 A JP-A-11-200381

  An object of this invention is to provide the joining structure which raises the joining strength of the junction part of a foundation part and a soil cement improved body in view of the said fact.

The improved structure of the soil cement according to the first aspect of the present invention is a wall-shaped soil cement improvement in which pillars are constructed in a lattice shape in plan view continuously in the ground, and uneven portions are formed on the side surfaces. And a foundation embedded with the concavo-convex portion that is supported by the head of the soil cement improved body, transmits the load of the structure to the soil cement improved body, and extends along the side surface of the soil cement improved body And a portion.

According to invention of Claim 1, the uneven | corrugated | grooved part extended along the side surface of a soil cement improved body is embedded in the base part. As a result, the structure is supported by the head, the uneven portions on the side surfaces become resistance, and the bonding strength between the base portion and the joint portion of the soil cement improved body increases. As a result, the horizontal force received by the foundation during an earthquake can be properly transmitted to the soil cement improvement body in which the pillars are constructed in a grid pattern in plan view in a continuous manner, and the pile that bears the horizontal load of the structure The cross-sectional area of can be reduced. Moreover, the planar view of the soil cement improved body has a lattice shape. Thereby, the ground where liquefaction is predicted at the time of an earthquake can be surrounded by the soil cement improved body, and liquefaction can be prevented. Moreover, since it is set as the grid | lattice form, the horizontal proof stress of a soil cement improved body can be raised with respect to the horizontal force from any direction.

According to a second aspect of the present invention, in the joint structure of a soil cement improved body according to the first aspect, the foundation portion sandwiches the uneven portion from both sides of the soil cement improved body.
According to invention of Claim 2, a base part pinches | concludes an uneven | corrugated | grooved part from the both sides of a soil cement improved body. At this time, the fracture strength of the joint portion can be adjusted by changing the material of the base portion and the improved soil cement and adjusting the strength of the weaker member.

  This makes it possible to adjust the horizontal force during the earthquake borne by the soil cement improvement body and the set ratio of the horizontal force borne by the pile, and the cross-sectional area of the pile and the cross-sectional area of the soil cement improvement body can be optimized. The construction cost can be reduced and the construction period can be shortened.

For example, by making the soil cement improved body a material having a lower breaking strength than the foundation, the soil cement improved body is destroyed first, and the fracture strength can be adjusted by adjusting the dimensions of the joint of the soil cement improved body Can be set. Thereby, the cross-sectional area of a pile and the cross-sectional area of a soil cement improved body can be optimized.
In addition, the proof stress of soil cement improved body itself can be adjusted by increasing / decreasing the number of rows of soil cement improved bodies.

  According to a third aspect of the present invention, in the joint structure of the soil cement improved body according to the first aspect, the soil cement improved body is arranged in parallel with a predetermined gap therebetween, and the gap portion is formed as the base portion. It is characterized by being filled with.

  According to invention of Claim 3, a predetermined clearance gap is opened, the soil cement column improvement body is arrange | positioned in parallel, and the clearance gap part is joined by the base part. Thereby, the single side | surface and foundation part of a soil cement improved body are joined by simple structure. Further, the bonding strength can be adjusted.

  The invention according to claim 4 is the joint structure of the soil cement improved body according to any one of claims 1 to 3, wherein the ground supporting the foundation portion has an extending direction of the soil cement improved body. It is characterized by being matched with the direction of the single earth pressure received.

According to the fourth aspect of the present invention, the extending direction of the soil cement improved body is a direction that coincides with the direction of the single earth pressure received by the ground supporting the foundation.
Thereby, in the ground which receives a single earth pressure, it can adjust to the intensity | strength which requires the joint strength of the soil cement improved body and foundation part of the direction of a single earth pressure. In addition, it is possible to support the structure while receiving it while avoiding the soil cement improved body directly receiving the single earth pressure. As a result, the cross-sectional area of the pile and the body cross-sectional area of the soil cement improvement can be optimized, and the construction cost can be reduced.

  Invention of Claim 5 is the joining structure of the soil cement improved body of any one of Claims 1-4, The extending direction of the soil cement improved body of the junction part of the said uneven | corrugated | grooved part and the said foundation part The joint strength between the soil cement improved body and the base portion is changed by adjusting at least one of the length of the concave and convex portions and the height in the vertical direction of the joint portion of the base portion.

According to the invention described in claim 5, the bonding strength between the soil cement improved body and the base portion is the length of the uneven portion in the extending direction of the soil cement improved body and the base portion, and the uneven portion and the base portion. This can be changed by adjusting at least one of the vertical heights of the joints.
Thereby, adjustment of the joint strength of a soil cement improved body and a base part becomes easy.

The piled raft foundation which is the invention according to claim 6 is the soil cement improved body joined by the joint structure of the soil cement improved body according to claims 1 to 5 , and a supporting pile for supporting the structure. And a direct foundation on which the structure is placed.

According to the invention described in claim 6 , the piled raft foundation is mounted with the soil cement improved body joined by the joint structure of the soil cement improved body, the support pile for supporting the structure, and the structure. Has a direct basis.
Thereby, irrespective of the share of the vertical load in the piled raft foundation, the share of the horizontal force between the pile and the soil cement improved body can be arbitrarily set.

  Since this invention is set as the said structure, the joint strength of the junction part of a base part and a soil cement improved body can be raised.

It is a figure which shows the basic composition of the joining structure of the soil cement improved body which concerns on the 1st Embodiment of this invention. It is a figure which shows the AA line cross section of the joining structure of the soil cement improved body which concerns on the 1st Embodiment of this invention. It is a figure which shows the basic composition of the joining structure of the soil cement improved body which concerns on the 2nd Embodiment of this invention, and an AA line cross section. It is a figure which shows the cross section of the soil cement improved body which concerns on the 2nd Embodiment of this invention. It is a figure which shows the basic composition of the other Example of the joining structure of the soil cement improved body which concerns on the 2nd Embodiment of this invention, and an AA line cross section. It is a figure which shows the basic composition of the joining structure of the soil cement improved body which concerns on the 3rd Embodiment of this invention, and an AA line cross section. It is a figure which shows the basic composition of the joining structure of the soil cement improved body which concerns on the 4th Embodiment of this invention, and an AA line cross section. It is a figure which shows the joining structure of the soil cement improvement body of the piled raft foundation based on the 5th Embodiment of this invention. It is a figure which shows the basic composition of the piled raft foundation based on the 5th Embodiment of this invention. It is a figure which shows the basic composition of the piled raft foundation of a prior art example. It is a figure which shows the basic composition of the joining structure of the soil cement improved body of a prior art example. It is a figure which shows the basic composition of the joining structure of the soil cement improved body of a prior art example. It is a figure which shows the basic composition of the joining structure of the soil cement improved body of a prior art example.

(First embodiment)
As shown in FIG. 1, the soil cement improved body joint structure 10 according to the first embodiment includes a soil cement improved body 12 continuously constructed in the ground 36.
The soil cement improved body 12 is formed by stirring and solidifying a stabilizer based on a cement-based solidifying material in a slurry state and the soil in the local ground 36 with a stirrer, and a cylindrical column is continuously formed. It is made into a wall shape.

  The ground 36 is a liquefied layer in which liquefaction is expected to occur during an earthquake, and the depth of the soil cement improved body 12 is set to the bottom of the liquefied layer 36.

  A base portion 14 of a structure (not shown) is constructed around the head 12H of the soil cement improved body 12, and the base beam 22 of the base portion 14 is supported by the top S1 of the soil cement improved body 12. . Thereby, the vertical load of the structure is transmitted to the soil cement improved body 12.

  The foundation 14 is a direct foundation of a piled raft foundation, a foundation slab 23 is constructed on the ground 36, and a floor slab 21 is constructed via the foundation beam 22. The pile is not shown.

  The joint between the soil cement improved body 12 and the foundation portion 14 is obtained by excavating the ground 36 around the head 12H of the soil cement improved body 12 with a width dimension W and a depth dimension H, and surrounding the excavated head 12H. Reinforcing bars 16 and 18 are arranged on the ground, and concrete 27 is placed on the ground 36.

  As shown in the cross-sectional view taken along line AA in FIG. 2, the soil cement improved body 12 is formed in a wall shape by integrating adjacent column bodies with a part of the side wall in a continuous column body. Furthermore, the wall body of the same structure is arrange | positioned in parallel, and the column body which adjoins in the wall body arrange | positioned in parallel, and a part of side wall are shared and integrated. Thereby, the width direction (X-axis direction) is a double structure.

  On both side surfaces of the soil cement improved body 12, there are formed concavo-convex portions 12 </ b> S composed of arc-shaped convex portions, which are the outer peripheral portions of the central portion of the column body, and integrated concave portions at both ends of the column body. Yes. The uneven portion 12S is embedded in the concrete 27 of the foundation slab 23 to a depth H.

  As a result, the concave and convex portions 12S on both sides are surrounded by the concrete 27, and the concave portion is also filled with the concrete 27. As a result, the bonding strength between the head 12H of the soil cement improved body 12 and the foundation slab 23 can be increased, and the horizontal force during an earthquake can be transmitted from the foundation slab 23 to the soil cement improved body 12.

  That is, for the horizontal force F in the Y direction at the time of an earthquake, the friction resistance R1 (not shown) of the joint surface between the top S1 and the foundation slab 23 at the top S1 of the soil cement improved body 12 and the side surface In addition, since slippage does not occur due to the uneven portion 12S, resistance is generated by the shear resistance R2 generated on the inner surface S2 of the soil cement improved body 12.

  At this time, the base portion 14 is formed of reinforced concrete, and the soil cement improved body 12 is formed of soil cement and is made of different materials. The fracture strength of the joint can be adjusted by adjusting the shear resistance R2 of the soil cement improved body 12 having the smaller shear strength.

  Specifically, the area of the projection surface S2 in the X-axis direction of the joint between the uneven portion 12S and the basic slab 23 is adjusted. That is, if at least one of the extension length L (not shown) in the Y-axis direction of the soil cement improved body 12 and the height H in the Z-axis direction of the joint between the uneven portion 12S and the foundation slab 23 is adjusted, The joint strength between the soil cement improved body 12 and the base portion 14 can be changed.

As described above, according to the present embodiment, the bonding strength between the soil cement improved body 12 and the base portion 14 can be adjusted. Thereby, the horizontal force borne by the soil cement improved body 12 can be arbitrarily set, and the load on the pile can be reduced.
In addition, the intensity | strength of the X-axis direction of the soil cement improved body 12 can respond | correspond by increasing a column row | line | column.

(Second Embodiment)
As shown in FIGS. 3A and 3B, the soil cement improved body joint structure 30 according to the second embodiment includes a soil cement improved body 32 continuously constructed in the ground 36. Yes.

  The soil cement improved body 32 is a wall body in which cylindrical columns are continuously constructed in a line. Concave and convex portions are formed on both side surfaces of the soil cement improved body 32, and the head portion 32H of the soil cement improved body 32 is embedded in the foundation portion 14 of the structure.

The base portion 14 is joined by sandwiching both side surfaces of the head portion 32H of the soil cement improved body 32 with the concrete 27 between the width dimension W and the depth dimension H. At this time, the foundation beam 22 of the foundation part 14 is supported by the top part S <b> 1 of the soil cement improved body 32.
The other parts are the same as the joint structure 10 of the soil cement improved body in the first embodiment, and a description thereof will be omitted.

  Thereby, adjustment of the joint strength of the soil cement improved body 32 and the base part 14 is attained, and the horizontal force borne by the soil cement improved body 32 can be arbitrarily set. As a result, the burden on the pile can be reduced.

  In addition, as shown in FIG. 4, the soil cement improvement body 32 may form two adjacent pillars simultaneously. Thereby, the soil cement improved body 32 can be constructed | assembled rationally, and a construction period can be shortened.

  Moreover, as shown in FIG. 5, the cross-sectional shape of the soil cement improved body 32 may not be circular. For example, a rectangular column 33 having a quadrangular cross section is formed, and a continuous wall body is formed by sharing the corners of adjacent quadrangular columns 33 and projecting from the rectangular column 33 to the side surface of the wall body. Alternatively, the uneven portion 33S may be formed based on repetition of the convex portion of the corner portion and the concave portion of the joint portion.

(Third embodiment)
As shown in FIG. 6, the joint structure 40 of the soil cement improvement body of 3rd Embodiment has the two soil cement improvement bodies 32 made into wall shape.

  The soil cement improved body 32 is the same as the soil cement improved body 32 described in the second embodiment, and a description thereof will be omitted. The two soil cement improvement bodies 32 are arranged in parallel at a predetermined distance D. The top S <b> 1 is embedded in the concrete 23. In the predetermined interval D, the concrete 27 of the foundation portion 14 enters to the depth H, and the soil cement improved body 32 and the foundation slab 23 are joined.

  Thereby, the soil cement improved body 32 and the foundation slab 23 can be joined with a simple configuration of the foundation portion 14. At this time, if at least one of the extension length L (not shown) in the Y-axis direction of the soil cement improved body 32 and the height H in the Z-axis direction of the joint between the uneven portion 32S and the foundation slab 23 is adjusted. The joint strength between the soil cement improved body 32 and the base portion 14 can be changed, and the horizontal force can be transmitted from the base portion 14 to the soil cement improved body 32.

  Thereby, the horizontal force borne by the soil cement improved body 32 can be arbitrarily set, and the load on the pile can be reduced.

(Fourth embodiment)
As shown in FIG. 7, the joint structure 48 of the soil cement improved body of 4th Embodiment has the soil cement improved body 12 formed in wall shape.

  The soil cement improved body 12 has been described in the first embodiment, and a description thereof will be omitted. The soil cement improved body 12 is formed by protruding the head portion 12H on the surface of the ground 36 at a height H. And the protruded head 12H is swallowed by the lower surface of the base part 23 to the depth H.

  Thereby, it becomes unnecessary to dig around the head 12H, and the soil cement improved body 12 and the base portion 14 can be easily joined. At this time, if at least one of the extension length L (not shown) in the Y-axis direction of the soil cement improved body 12 and the height H in the Z-axis direction of the joint between the uneven portion 12S and the foundation slab 23 is adjusted. The joint strength between the soil cement improved body 12 and the base portion 14 can be changed, and the horizontal force can be transmitted from the base portion 14 to the soil cement improved body 32.

  Thereby, the horizontal force borne by the soil cement improved body 12 can be arbitrarily set, and the load on the pile can be reduced.

(Fifth embodiment)
As shown in FIG. 8, the piled raft foundation 34 according to the fifth embodiment is constructed such that the soil cement improved body 12 described in the first embodiment is constructed in the Y-axis direction except for the outer peripheral portion. It is joined to the part 14.

  Moreover, the soil cement improved body 32 demonstrated in 2nd Embodiment is constructed | assembled in the outer peripheral part and the X-axis direction, and is joined with the base part 14. FIG. The soil cement improved body 12 and the soil cement improved body 32 have a lattice shape in plan view.

  Further, in the lattice formed by the soil cement modified bodies 12 and 32, a pile 28 having a reduced diameter is provided to suppress the settlement of the piled raft foundation 34.

  As shown in the elevational view of FIG. 9, the piled raft foundation 34 has a foundation 14 that is a direct foundation on which a building 46 is placed, and a soil cement improvement that reaches the bottom of the liquefied layer 36 in a lattice shape. It has the piles 28 provided through the bodies 12 and 32 and the liquefied layer 36.

  At this time, by adjusting the joint strength between the soil cement improved bodies 12 and 32 and the foundation portion 14, the soil cement improved bodies 12 and 32 bear a part of the horizontal force applied to the pile 28 and the diameter is reduced. 28 bears the remaining horizontal force.

  That is, in the event of an earthquake, the soil cement improvement bodies 12 and 32 bear a set ratio of horizontal force, and at the same time, prevent liquefaction of the liquefied layer 36 surrounded by a lattice. As a result, the frictional force between the outer peripheral surface of the pile 28 and the ground 36 is maintained in the state before the earthquake, and the settlement of the building 46 can be suppressed even if the pile 28 has a reduced diameter.

  In this way, by adjusting the horizontal force at the time of earthquake borne by the soil cement improved body 12 and the set ratio of the horizontal force borne by the pile 28, the cross-sectional area of the pile 28 and the soil cement improved body 12 can be adjusted. The cross-sectional area can be optimized, the construction cost of the piled raft foundation 34 can be reduced, and the construction period can be shortened.

  On the other hand, as shown in FIG. 10, the conventional piled raft foundation 50 forms soil cement improvement bodies 52 in a wall shape in a row and arranges them in a lattice shape, and is used for liquefaction countermeasures. At the same time, the soil cement improved body 52 supports the vertical load and the horizontal force, and the pile 56 is used for suppressing settlement.

  Alternatively, the soil cement improved body 52 formed in a lattice shape is used for liquefaction countermeasures, and the soil cement improved body 52 is caused to bear the vertical load corresponding to the rigidity ratio with the pile 56 and the horizontal force corresponding to the frictional resistance. The pile 56 is caused to bear a vertical load corresponding to the rigidity ratio with the soil cement improved body 52 and a horizontal force that cannot be supported by the soil cement improved body 52.

  However, as described above, since the conventional piled raft foundation 50 cannot adjust the joint strength between the soil cement improved body 52 and the foundation part 54, the frictional resistance of the joint surface is the vertical load sharing of the piled raft foundation 50. It is determined uniquely by the rate.

  Specifically, when the horizontal force including the single earth pressure is very large, only about 50% of the total horizontal force can be borne by the soil cement improved body 52, and the pile 56 has a large diameter.

  Furthermore, since the joint strength with the base portion 54 cannot be adjusted, there is a problem that the high in-plane rigidity and shear strength of the soil cement improved body 52 cannot be fully utilized except for liquefaction countermeasures.

  On the other hand, in the present embodiment, as shown in FIG. 8, under the condition that a large single earth pressure is applied in the direction of arrow P, the soil cement improved body 12 formed in a double direction is parallel to the single earth pressure. By disposing in this manner, the bonding strength between the soil cement improved body 12 and the foundation portion 14 is increased, and the horizontal force received by the foundation portion 14 can be appropriately transmitted to the soil cement improved body 12. As a result, the cross-sectional area of the pile 28 and the cross-sectional area of the soil cement improved body 12 can be optimized, and the cross-sectional area of the pile 28 can be made smaller than that of the conventional pile 56.

  In addition, although all the above description was performed on the conditions which use the pile 28, depending on the property of the ground 36, a pile 28 may not be provided but only the soil cement improved body 12 and the foundation part 14 may bear a horizontal force. .

10 Joint structure of soil cement improved body 12 Soil cement improved body 12S Concavity and convexity 14 Base part 34 Piled raft foundation

Claims (6)

A wall-shaped soil cement improvement body in which pillars are constructed in a lattice shape in plan view continuously in the ground, and uneven portions are formed on the side surfaces,
A foundation portion that is supported by the head of the soil cement improvement body, transmits a load of a structure to the soil cement improvement body, and is embedded with the concavo-convex portion extending along a side surface of the soil cement improvement body;
Structure of improved soil cement having a structure.   The joint structure of the soil cement improved body according to claim 1, wherein the foundation portion sandwiches the uneven portion from both sides of the soil cement improved body.   The joint structure of the soil cement improved body according to claim 1, wherein the soil cement improved body is arranged in parallel with a predetermined gap therebetween, and the gap portion is filled with the foundation portion.   The joint of the soil cement improvement body of any one of Claims 1-3 which made the extending direction of the said soil cement improvement body correspond with the direction of the single earth pressure which the ground which supports the said foundation part has received. Construction.   The soil is adjusted by adjusting at least one of the length in the extending direction of the soil cement improvement body of the joint portion between the uneven portion and the base portion and the height in the vertical direction of the joint portion between the uneven portion and the base portion. The joint structure of the soil cement improvement body of any one of Claims 1-4 which changes the joint strength of a cement improvement body and the said foundation part. The soil cement improved body joined with the joint structure of the soil cement improved body according to claim 1, a support pile that supports the structure, and a direct foundation on which the structure is placed. Piled raft basics.

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