JP2015063866A - Base structure for counteracting liquefaction and construction method for counteracting liquefaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple base structure for counteracting liquefaction requiring small construction cost while effectively counteracting liquefaction, and a construction method for counteracting liquefaction.SOLUTION: A base structure A for counteracting liquefaction in a building in an earthquake comprises: a lower ground improver 1 whose upper surface 1A is arranged below the ground GL; a plurality of friction piles (P, P,...) extending downward from the lower surface 1B of the lower ground improver 1 and comprising a plurality of concrete piles (4, 4,...) as preservative piles whose lower edges are arranged below the ground water level WL and whose upper parts are engaged in a plurality of pile supporting holes (h, h,...) vertically penetrating the lower ground improver 1, and wood piles (5, 5,...) connected to and fixed on lower end parts of the concrete piles (4, 4,...); an upper ground improver 2 formed on the lower ground improver 1; and base 3 of the building established on the upper ground improver 2.

Description

  The present invention relates to a simple foundation structure and a construction method that are effective for countermeasures against liquefaction during an earthquake and have low construction costs.

The Tohoku-Pacific Ocean Earthquake that occurred at 14:46 on March 11, 2011 was due to the sliding failure of the plate boundary between the Pacific plate and the North American plate on which Tohoku Japan is located. It was estimated to be about 200 km from east to west, and it was the largest super-earthquake in Japan's observation history, reaching a moment magnitude (Mw) of 9.0. Furthermore, because the plate slip failure region was huge, the time from the start to the end of the failure was very long compared to previous earthquakes (about 5 minutes). Because the ground was shaken for a long time in this way, the acceleration level on the ground surface was not so high, and very large liquefaction occurred at a place far away from the epicenter (such as Urayasu City in Chiba Prefecture). Occurring and causing great damage due to the sideways movement and settlement of the building, its restoration is extremely difficult economically.
In view of such a situation, in the future, more rigorous liquefaction determination and implementation of a countermeasure method based on the determination result will be required.
On the other hand, various liquefaction countermeasure methods at the time of earthquake already exist and are being implemented, but most of them are very large and large-scaled by special heavy machinery (for example, Patent Documents 1 and 2). (Refer to the above)) Applicability is low for low-rise and small-scale individual buildings because it is relatively expensive.
From this point of view, construction with ordinary heavy machinery at the construction site is possible, and development of a liquefaction countermeasure construction method that is simple and low in construction cost is desired. There is one in which a wooden pile is placed, the heads of the wooden pile are connected with a connecting material such as a reinforcing bar, and a foundation board is constructed on the plurality of piles with a light cement solidified soil (see Patent Document 3). .

Japanese Patent Publication No. 04-54004 Japanese Patent Laid-Open No. 10-46619 JP2013-124511A Japanese Patent No. 3608568

In the liquefaction countermeasure method of Patent Document 3, the ground (2) is dug down, a wooden pile (14, 14,...) Is placed, and the head of the wooden pile (14, 14,. ), And then a lightweight cement solidified soil is placed so that the heads of the wooden piles (14, 14,...) And the connecting material (16) are buried, thereby constructing a flat foundation (12). According to the procedure, the foundation structure (10) of the building is constructed. Here, the foundation board (12), which is a light cement solidified soil, is constructed at a level lower than the groundwater level (W.L).
In such a liquefaction countermeasure construction method, the heads of the wooden piles (14, 14,...) Are connected by the connecting material (16). When the two are connected, it is necessary to dig up the entire ground, so as to reduce the weight of the ground improvement body as in Patent Document 4, while suppressing the uneven settlement and the lateral flow of the unmodified soil below. A shallow ground improvement body having a shape that is very effective for the purpose, that is, a horizontal plate-like upper improvement body, an outer peripheral improvement body that forms an outer frame depending on the lower surface of the upper improvement body, and the upper improvement Combined with a shallow ground improvement body having a shape composed of at least one internal improvement body that hangs down from the lower surface of the body and connects the outer frames to partition the inner area of the outer peripheral improvement body into a plurality of areas Cannot be used.

Furthermore, after digging the ground (2) and placing the wooden piles (14, 14,...), The heads of the wooden piles (14, 14,...) Are connected by a connecting material (16) such as a reinforcing bar. Therefore, after this work, the heads of the wooden piles (14, 14,...) Are connected by a connecting material (16) such as a reinforcing bar.
Therefore, since the ground cannot be improved by mixing and stirring while injecting the solidified material and water using the local soil without being dug down, it takes man-hours and the construction cost increases.
Furthermore, since the heads of the wooden piles (14, 14,...) Are connected by a connecting material (16) such as a reinforcing bar, each of the wooden piles (14, 14,...) Is connected by the connecting material (16). The integrity of the movement (displacement) of the pile head is considered to increase, but in combination with the fact that the construction cost increases if the height of the foundation (12) constructed lower than the groundwater level is increased. In the event of an earthquake, the inclination of the wooden piles (14, 14,...) Cannot be sufficiently restrained so as to suppress the shear deformation of the soil elements between the wooden piles (14, 14,...). The liquefaction suppression effect cannot be obtained.
Moreover, in order not to decay the wooden piles (14, 14,...), The foundation board (12) is constructed lower than the groundwater level (W.L), so the ground water level (W.L.). ) Is close to the ground surface (for example, when the groundwater level (W.L) is within 0.5 m from the ground surface), there is no problem, but when the groundwater level (W.L) becomes deeper. Since the depth of digging down the ground (2) (the height position for constructing the foundation (12)) becomes deep, the construction cost increases.

  Therefore, in view of the above-described situation, the present invention provides a liquefaction countermeasure basic structure and a liquefaction countermeasure construction method that are simple and low in construction cost while being able to effectively perform liquefaction countermeasures. In the point.

  Inventors of the present invention are able to effectively implement liquefaction countermeasures in view of the damage situation caused by a wide range of liquefaction phenomenon in the Great East Japan Earthquake caused by the Tohoku Earthquake, but it is simple and reduces the construction cost. The present invention has been completed by conducting intensive studies on possible foundation structures and conducting comparative studies through simulations and the like.

  That is, the liquefaction countermeasure foundation structure according to the present invention is a foundation structure for taking measures against liquefaction of a building during an earthquake in order to solve the above-mentioned problem, and the upper surface is positioned below the ground surface. A lower ground improvement body, and a plurality of wooden piles or bamboo piles whose upper parts are fitted in a plurality of pile support holes penetrating the lower ground improvement body vertically, depending on the lower surface of the lower ground improvement body A plurality of friction piles, an upper ground improvement body formed on the lower ground improvement body, and a foundation of the building placed on the upper ground improvement body. 1).

According to such a configuration, the friction pile is installed at an appropriate interval and number according to the ground condition where liquefaction is expected to occur, and the upper part is fitted to a pile support hole that vertically penetrates the lower ground improvement body. Thus, the loose liquefaction layer is compacted and the shear deformation at the time of earthquake is suppressed, so that liquefaction and lateral flow and settlement can be suppressed.
In addition, since the friction pile is composed of a wooden pile or a bamboo pile, the cost is low, and the lightness and the frictional resistance of the surface are large.
In addition, when wooden piles are used, a large amount of timber (thinned wood) is used and fixed underground, which not only promotes forestry, but also contributes to CO ₂ reduction due to the carbon storage effect. When piles are used, a large amount of fast-growing bamboo is harvested and used effectively, which can further reduce costs and protect the rich forest by mass-cutting bamboo that destroys the rich ecosystem of the forest. it can.

  Further, the liquefaction countermeasure basic structure according to the present invention is a foundation structure for performing liquefaction countermeasures for buildings during an earthquake in order to solve the above-mentioned problem, and the upper surface is located below the ground surface. A lower ground improvement body, a plurality of non-septic piles whose upper ends are fitted in a plurality of pile support holes penetrating vertically through the lower ground improvement body, and whose lower ends are positioned below the groundwater level, and the non-septic properties A plurality of friction piles hanging from the lower surface of the lower ground improvement body, which are constituted by wooden piles or bamboo piles connected and fixed to the lower end of the pile, and an upper ground improvement body formed on the lower ground improvement body And the foundation of the building placed on the upper ground improvement body (claim 2).

  According to such a structure, while exhibiting the effect similar to the effect of the invention which concerns on the said Claim 1, it connects to a non-perishable pile on the upper side of a wooden pile or a bamboo pile, and is used as a friction pile, and groundwater Since there is only a non-rotatable pile above the position, the wooden pile or bamboo pile does not decay because it does not touch the air, so the strength does not decrease over a long period of time.

Here, it is preferable that the lower ground improvement body is formed with a plurality of holes penetrating vertically so as to divide the inner region into a plurality (Claim 3).
According to such a configuration, since the lower ground improvement body is formed with a plurality of holes penetrating vertically, the lower ground improvement body further suppresses settlement by reducing the weight of the lower ground improvement body, and the lower side of the upper ground improvement body. Since the dent is formed, the effect of suppressing the uneven settlement and the effect of suppressing the lateral flow of the lower unmodified soil are enhanced.

Further, it is preferable that a fixing member press-fitted between the pile support hole of the lower ground improvement body and the upper portion of the friction pile is provided.
According to such a configuration, since the upper part of the friction pile is firmly fixed to the lower ground improvement body by the fixing member, in the event of an earthquake, the shear deformation of the soil element between the friction piles in the immediately lower ground is suppressed. In addition, since the inclination of the friction pile can be sufficiently restrained, a sufficient liquefaction suppressing effect can be obtained.

  In order to solve the above problems, the liquefaction countermeasure method according to the present invention includes a lower ground improvement body having an upper surface located below the ground surface, a plurality of friction piles whose upper portions are supported by the lower ground improvement body, It is a construction method for building liquefaction countermeasures in the event of an earthquake, which constructs an upper ground improvement body on the ground improvement body and a liquefaction countermeasure foundation structure consisting of the foundation of the building on the upper ground improvement body. The surface layer of the ground where liquefaction is expected to occur is matched to the planar shape of the lower ground improvement body, and a dug process for digging the upper side of the lower ground improvement body, and the shape of the lower ground improvement body Drilling the surface layer, mixing and stirring while injecting solidified material and water, then compacting to form the lower ground improvement body, wooden pile or bamboo pile, or non-rotating pile and the non-rotating Connected to the lower end of A plurality of friction piles composed of fixed wooden piles or bamboo piles are suspended from the lower surface of the lower ground improvement body through the primary improvement process and vertically through the lower ground improvement body in an unconsolidated state. Friction pile placing process to be placed, and soil dug down by the dug down process is backfilled on the upper side of the lower ground improvement body, the surface layer portion of the ground is excavated into the shape of the upper ground improvement body, solidified A secondary improvement process for forming the upper ground improvement body by mixing and stirring after injecting material and water, and a foundation placing process for placing the foundation of the building on the upper ground improvement body (Claim 5).

According to such a construction method, the primary improvement step for forming the lower ground improvement body and the secondary improvement step for forming the upper ground improvement body are methods of compacting after mixing and stirring while injecting the solidifying material and water. The construction cost can be reduced.
In addition, since the friction piles are driven so as to hang down from the lower surface of the lower ground improvement body through the lower ground improvement body in an unconsolidated state through the primary improvement process, the continuity of construction is improved. Therefore, the construction cost can be further reduced.
Furthermore, the liquefaction countermeasure basic structure constructed by such a construction method has the same effects as the inventions according to claims 1 and 2.

Here, it is preferable that the lower ground improvement body is formed with a plurality of holes penetrating vertically so as to divide the inner region into a plurality of parts (Claim 6).
According to such a construction method, according to the planar shape of the lower ground improvement body, the amount of soil to be dug by the dug process to dug the upper side of the lower ground improvement body, and backfilled to the upper side of the lower ground improvement body after the friction pile placing process Since the amount of soil is reduced, the construction cost can be reduced.
Moreover, the liquefaction countermeasure basic structure constructed by such a construction method has the same effects as the invention according to claim 3.

Moreover, it is preferable to provide a fixing member press-fitting step of press-fitting a fixing member between the through hole of the lower ground improvement body through which the friction pile penetrates and the upper portion of the friction pile after the friction pile placing step. Item 7).
The liquefaction countermeasure basic structure constructed by such a construction method has the same effects as the invention according to claim 4.

As described above, according to the liquefaction countermeasure basic structure according to the present invention,
(A) The friction pile with the upper part fitted in the pile support hole that penetrates the lower ground improvement body up and down compacts the loose liquefaction layer and suppresses shear deformation during earthquakes, so liquefaction and lateral flow And being able to control settlement
(B) When friction piles including wooden piles or bamboo piles are used, they are low in cost, and are light and have a large surface frictional resistance, so the settlement suppression effect is great.
(C) When friction piles including wooden piles are used, a large amount of timber (thinned wood) is effectively fixed and fixed underground, so that not only forestry promotion but also carbon storage effects can contribute to CO ₂ reduction. ,
(D) When using a friction pile with the upper part being a non-permanent pile, the lower wooden pile or bamboo pile is constructed so as not to touch the air, so that the strength does not decrease over a long period of time.
(E) In the structure in which a plurality of holes penetrating vertically are formed in the lower ground improvement body, the settlement is further suppressed by weight reduction, the effect of suppressing the uneven settlement and the lateral flow of the unmodified soil in the lower part are suppressed. Increase effectiveness,
(F) In the configuration with a fixed member press-fitted between the pile support hole of the lower ground improvement body and the upper part of the friction pile, the slope of the friction pile is inclined so as to suppress the shear deformation of the ground directly under the earthquake. Can be sufficiently restrained, so that a sufficient liquefaction suppression effect can be obtained,
There are remarkable effects such as.

Further, according to the liquefaction countermeasure method according to the present invention,
(G) The primary improvement process to form the lower ground improvement body and the secondary improvement process to form the upper ground improvement body are methods of compacting after mixing and stirring while injecting solidifying material and water, thus reducing construction costs. What you can do,
(H) Since the friction pile is driven so as to hang down from the lower surface of the lower ground improvement body through the lower ground improvement body in the unconsolidated state through the primary improvement process, the continuity of construction is improved. Therefore, the construction cost can be further reduced,
(K) In a structure in which a plurality of holes penetrating vertically are formed in the lower ground improvement body, the amount of soil to be dug in accordance with the planar shape of the lower ground improvement body, and the upper side of the lower ground improvement body after the friction pile placing process Because the amount of soil to be backfilled is reduced, the construction cost can be reduced,
There are remarkable effects such as.

It is a longitudinal cross-sectional view which shows the principal part of the liquefaction countermeasure foundation structure which concerns on embodiment of this invention. It is a plan view, (a) is a state where the lower ground improvement body is formed through the primary improvement process, and the friction pile is driven through the friction pile driving process, (b) is the lower part through the secondary improvement process The state which the upper ground improvement body was formed on the ground improvement body is shown. It is arrow XX sectional drawing of FIG.2 (b). It is a longitudinal cross-sectional view which shows an example of a connection member. It is a longitudinal cross-sectional view which shows an example of a fixing member (fixing member press-fit process). (A) is a longitudinal cross-sectional view which shows another example of a fixing member (fixing member press-fit process), (b) is a ZZ cross-sectional view of (a).

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments shown in the accompanying drawings, and includes all the embodiments that satisfy the requirements described in the claims. It is a waste.

As shown in the longitudinal sectional view of FIG. 1, the liquefaction countermeasure basic structure A according to the embodiment of the present invention is constructed on the ground G where the occurrence of liquefaction is predicted, and the upper surface 1A is below the ground surface GL. Are located in the lower ground improvement body 1 and the plurality of pile support holes h, h,... Vertically passing through the lower ground improvement body 1 and a plurality of frictions depending on the lower surface 1B of the lower ground improvement body 1 Pile P, P,..., Upper ground improvement body 2 formed on the lower ground improvement body 1, and building foundation 3 placed on the upper ground improvement body 2.
Further, as shown in the longitudinal sectional view of FIG. 1 and the plan view of FIG. 2, the lower ground improvement body 1 is formed with a plurality of holes H, H,. Is done.

In addition, the friction pile P has a concrete pile 4 that is a non-rotatable pile (corrosion-resistant pile), the lower end of which is located below the groundwater level (groundwater surface) WL, and a connecting member at the lower end of the concrete pile 4. The upper wooden pile 5 connected and fixed by C, and the lower wooden pile 5 connected and fixed by the connecting member C to the lower end of the upper wooden pile 5, the ground G in which the occurrence of liquefaction is predicted Installed at appropriate intervals and number according to the situation.
Here, instead of the concrete pile 4, other non-destructive piles such as steel piles may be used, and instead of the wooden pile 5, bamboo piles such as 孟 mong bamboo with appropriate processing are used. May be.
In addition, when the groundwater level WL is shallow (when the distance from the ground surface GL to the groundwater surface is short), the friction pile P is made of wooden piles 5, 5, It may be constituted only by.

Next, the construction method of the liquefaction countermeasure basic structure A will be described.
(Drilling process)
First, in order to form the lower ground improvement body 1 in which the upper surface 1A is located below the ground surface GL shown in the longitudinal sectional view of FIG. The surface layer portion is subjected to a digging process for digging the upper side of the lower ground improvement body 1 in accordance with the planar shape of the lower ground improvement body 1 by, for example, cutting off with a backhoe.

(Primary improvement process)
Next, excavate the surface layer of the ground G into the shape of the lower ground improvement body 1 with a backhoe equipped with a mixing fork as an attachment, and mix and stir while injecting solidification material such as cement-based solidification material and water. And the primary improvement process which compacts with a roller etc. and forms the lower ground improvement body 1 is performed.

(Friction pile placing process)
Next, a plurality of friction piles P, P,... Are penetrating from the lower surface 2B of the lower ground improvement body 1 through the lower ground improvement body 1 that has not been consolidated through the primary improvement process and vertically. Friction pile driving process is performed by placing a dedicated pile driver or a backhoe equipped with a pile driving attachment (showing the state where the friction piles P, P,... Have been driven through the friction pile driving process) (Refer to the plan view of FIG. 2A.)

(Secondary improvement process)
Next, the soil dug down by the dug process is backfilled on the upper side of the lower ground improvement body 1 with a backhoe and the upper ground improvement of the surface layer portion of the ground G from the ground surface GL by a backhoe fitted with a mixing fork as an attachment. Excavated into the shape of the body 2, mixed and stirred while injecting the solidified material and water, and compacted with heavy machinery and rollers, etc., to perform the secondary improvement process to form the upper ground improvement body 2 (the lower part through the secondary improvement process) (See the plan view of FIG. 2 (b) and the longitudinal sectional view of FIG. 3) showing a state in which the upper ground improvement body 2 is formed on the ground improvement body 1.
Here, in the longitudinal cross-sectional view shown in FIG. 3, the thickness D1 of the lower ground improvement body 1 is about 1-2 m, the thickness D2 of the upper ground improvement body 2 is about 0.6-1.2 m, and a friction pile. The length L of P is 20 m or less, the cross-sectional shape of the friction pile P is circular, the diameter d is about 0.15 to 0.2 m, and the installation pitch of the plurality of friction piles P, P,. The center distance between P and P is about 0.5 to 1.5 m.

(Basic placement process)
Next, in the state shown in the plan view of FIG. 2B and the longitudinal sectional view of FIG. 3, foundation excavation is performed with a backhoe or the like, and the bar arrangement and concrete of the foundation 3 of the building are placed on the upper ground improvement body 2. A foundation placing step for placing is performed, and a liquefaction countermeasure foundation structure A as shown in the longitudinal sectional view of FIG. 1 is constructed.

Next, a configuration example of the connecting member C will be described.
In the configuration example of the friction pile P shown in the longitudinal sectional views of FIGS. 1 and 3, three piles, that is, a concrete pile 4 and wooden piles 5 and 5 are connected and fixed using two connecting members C and C. And integrated. The number of piles to be connected and fixed using the connecting member C (the number of piles constituting the friction pile P) may be two or four or more.

With reference to the longitudinal cross-sectional view of FIG. 4, the structural example of the connection member C which connects the upper and lower wooden piles 5 and 5 is demonstrated.
In the state where the lower surface 5B of the upper wooden pile 5 and the upper surface 5A of the lower wooden pile 5 are in contact with each other, the annular wedges 7, 8, 9 are inserted into the steel pipe 6 located radially outward of the connecting position. , And the wedge 8 is driven in the axial direction toward the wedge 9 (downward in FIG. 4) and the wedge 9 is driven in the axial direction toward the wedge 8 (upward in FIG. 4). , 5 are firmly connected and fixed.
In addition, the connection fixation of the upper wooden pile 5 and the concrete pile 4 of the upper side can also be performed by the connection member C of the same structure.
By using such a connecting member C, it is possible to easily form the friction pile P in which the non-rotatable pile and the wooden pile 5 are connected and fixed, and in the thinned wood where it is difficult to obtain a long material, it is easy to obtain. A low-priced thinned lumber of the required thickness can be connected to form the friction pile P of the required length.

Next, the fixing member F press-fitted between the pile support hole h of the lower ground improvement body 1 and the upper part of the friction pile P will be described.
In the state where the friction piles P, P,... Are placed so as to penetrate the lower ground improvement body 1 that has not been consolidated through the primary improvement process in the friction pile placement process, the lower ground improvement body 1 is cured. Depending on the degree, looseness (gap) may occur between the pile support hole h, that is, the through hole h that penetrates the lower ground improvement body 1 and the upper portion of the friction pile P.
In FIG. 5 and FIG. 6 described below, the looseness (gap) is shown enlarged (exaggerated) for convenience of explanation (for ease of viewing).

If there is such a looseness (clearance), the upper support of the friction pile P is not sufficient, and the friction pile P is controlled so as to suppress the shear deformation of the soil element between the friction piles P, P,. , P,... Cannot be sufficiently restrained, so that the mortar 10 as the fixing member F is pumped between the through hole h and the upper portion of the friction pile P as shown in the longitudinal sectional view of FIG. Press-fit with etc.
The fixing member press-fitting step for press-fitting the mortar 10 as the fixing member F may be performed after the friction pile placing step.
Further, as the fixing member F, as shown in the longitudinal sectional view of FIG. 6A and the cross-sectional plan view of FIG. 6B, the fixing member F is interposed between the through hole h and the upper portion of the friction pile P. Arc-shaped plate members 11, 11, 11 having a thickness of about 1 cm may be press-fitted using an arm of a heavy machine at a normal construction site.
Or when the friction pile P is comprised only with the wooden piles 5, 5, ..., the radial direction cut | offset of the radial direction of about 3 cm or three in the circumferential direction equally on the upper surface of the top wooden pile 5 is carried out. The upper portion of the wooden pile 5 is enlarged by inserting a tapered timber (for example, 5 mm thick at the tip and 15 mm thick at the leading end) into the cut with a mallet or the like. You may do it.

According to the liquefaction countermeasure basic structure A as described above, pile supports that are installed at an appropriate interval and number according to the situation of the ground G where liquefaction is expected to occur and penetrate the lower ground improvement body 1 up and down. Friction piles P, P, ... fitted with holes (through holes) h, h, ... to compact a loose liquefied layer and suppress shear deformation during an earthquake, so liquefaction and lateral flow And subsidence can be suppressed.
Moreover, since the whole or a part of the friction pile P is comprised by the wooden pile 5 or the bamboo pile, while being low-cost, since it is lightweight and the frictional resistance of a surface is large, the settlement suppression effect is large.
Furthermore, when wooden piles 5, 5, ... are used, a large amount of timber (thinned wood) is effectively secured and fixed underground, which not only promotes forestry but also contributes to CO ₂ reduction through carbon storage effects. When bamboo piles are used, a large amount of fast-growing bamboo is harvested and used effectively, further reducing costs and making a rich forest by mass harvesting bamboo that destroys the forest's rich ecosystem. I can protect it.

Furthermore, the friction pile P is composed of a non-rotating pile whose lower end is located below the groundwater level WL and a wooden pile 5 or a bamboo pile connected and fixed to the lower end of the non-rotating pile. Since there are only non-decayable piles above the groundwater level WL, the wooden piles 5 or bamboo piles do not touch the air so that they do not decay, so the strength does not decrease over a long period of time.
Further, by forming a plurality of holes H, H,... Vertically passing through the lower ground improvement body 1 so as to divide the inner region into a plurality of parts, the lower ground improvement body 1 further suppresses settlement by reducing the weight. In addition, since a depression is formed on the lower side of the upper ground improvement body 2, the effect of suppressing the uneven settlement and the effect of suppressing the lateral flow of the lower unmodified soil are increased.
Furthermore, by providing the fixing members F, F,... Press-fitted between the pile support holes h, h,... Of the lower ground improvement body 1 and the upper portions of the friction piles P, P,. Because the upper part of the friction piles P, P,... Is firmly fixed to the lower ground improvement body 1, the shear deformation of the soil elements between the friction piles P, P,. Thus, since the inclination of the friction piles P, P,... Can be sufficiently restricted, a sufficient liquefaction suppression effect can be obtained.

According to the liquefaction countermeasure construction method as described above, the primary improvement process for forming the lower ground improvement body 1 and the secondary improvement process for forming the upper ground improvement body 2 are mixed and stirred while injecting solidified material and water. Since it is the method of compacting after doing, construction cost can be reduced.
Further, in the friction pile placing step, the friction piles P, P so as to pass through the lower ground improvement body 1 that has not been consolidated through the primary improvement step and hang down from the lower surface 1B of the lower ground improvement body 1. ,... Are placed, so that the continuity of construction is improved, and construction costs can be further reduced.
Further, the lower ground improvement body 1 is formed with a plurality of holes H, H,... That vertically penetrate so as to divide the inner region into a plurality of parts, thereby improving the lower ground according to the planar shape of the lower ground improvement body 1. Since the amount of soil to be dug down by the digging process to dig up the upper side of the body 1 and the amount of soil to be backfilled on the upper side of the lower ground improvement body 1 after the friction pile placing process or the fixing member press-fitting process is reduced, the construction cost is reduced. Can be reduced.

A Liquefaction countermeasure basic structure C Connecting member D1 Lower ground improvement body thickness D2 Upper ground improvement body thickness d Friction pile diameter F Fixed member G Ground GL Ground surface H Hole h Pile support hole (through hole)
L Length of friction pile P Friction pile WL Groundwater level (groundwater surface)
1 Lower ground improvement body 1A Upper surface 1B Lower surface 2 Upper ground improvement body 2A Upper surface 2B Lower surface 3 Building foundation 4 Concrete pile (non-rotatable pile)
5 Wooden pile 5A Upper surface 5B Lower surface 6 Steel pipe 7, 8, 9 Wedge 10 Mortar 11 Arc-shaped board

That is, the liquefaction countermeasure foundation structure according to the present invention is a foundation structure for taking measures against liquefaction of a building during an earthquake in order to solve the above-mentioned problem, and the upper surface is positioned below the ground surface. A lower ground improvement body, and a plurality of wooden piles or bamboo piles whose upper parts are fitted in a plurality of pile support holes penetrating the lower ground improvement body vertically, depending on the lower surface of the lower ground improvement body A plurality of friction piles, an upper ground improvement body formed on the lower ground improvement body, a foundation of the building placed on the upper ground improvement body, and a pile support hole of the lower ground improvement body And an arcuate plate material press-fitted between the upper part of the friction pile (claim 1).

According to such a configuration, the friction pile is installed at an appropriate interval and number according to the ground condition where liquefaction is expected to occur, and the upper part is fitted to a pile support hole that vertically penetrates the lower ground improvement body. Thus, the loose liquefaction layer is compacted and the shear deformation at the time of earthquake is suppressed, so that liquefaction and lateral flow and settlement can be suppressed.
In addition, since the friction pile is composed of a wooden pile or a bamboo pile, the cost is low, and the lightness and the frictional resistance of the surface are large.
In addition, when wooden piles are used, a large amount of timber (thinned wood) is used and fixed underground, which not only promotes forestry, but also contributes to CO ₂ reduction due to the carbon storage effect. When piles are used, a large amount of fast-growing bamboo is harvested and used effectively, which can further reduce costs and protect the rich forest by mass-cutting bamboo that destroys the rich ecosystem of the forest. it can.
In addition, the upper part of the friction pile is firmly fixed to the lower ground improvement body by an arc-shaped plate pressed between the pile support hole of the lower ground improvement body and the upper part of the friction pile. Since the inclination of the friction pile can be sufficiently restrained so as to suppress the shear deformation of the soil element between the friction piles in the ground, sufficient liquefaction suppression effect can be obtained.

Further, the liquefaction countermeasure basic structure according to the present invention is a foundation structure for performing liquefaction countermeasures for buildings during an earthquake in order to solve the above-mentioned problem, and the upper surface is located below the ground surface. A lower ground improvement body, a plurality of non-septic piles whose upper ends are fitted in a plurality of pile support holes penetrating vertically through the lower ground improvement body, and whose lower ends are positioned below the groundwater level, and the non-septic properties A plurality of friction piles hanging from the lower surface of the lower ground improvement body, which are constituted by wooden piles or bamboo piles connected and fixed to the lower end of the pile, and an upper ground improvement body formed on the lower ground improvement body And the foundation of the building placed on the upper ground improvement body, and an arcuate plate material press-fitted between the pile support hole of the lower ground improvement body and the upper part of the friction pile. It is characterized (claim 2).

In order to solve the above problems, the liquefaction countermeasure method according to the present invention includes a lower ground improvement body having an upper surface located below the ground surface, a plurality of friction piles whose upper portions are supported by the lower ground improvement body, It is a construction method for building liquefaction countermeasures in the event of an earthquake, which constructs an upper ground improvement body on the ground improvement body and a liquefaction countermeasure foundation structure consisting of the foundation of the building on the upper ground improvement body. The surface layer of the ground where liquefaction is expected to occur is matched to the planar shape of the lower ground improvement body, and a dug process for digging the upper side of the lower ground improvement body, and the shape of the lower ground improvement body Drilling the surface layer, mixing and stirring while injecting solidified material and water, then compacting to form the lower ground improvement body, wooden pile or bamboo pile, or non-rotating pile and the non-rotating Connected to the lower end of A plurality of friction piles composed of fixed wooden piles or bamboo piles are suspended from the lower surface of the lower ground improvement body through the primary improvement process and vertically through the lower ground improvement body in an unconsolidated state. Friction pile placing step for placing and after the friction pile placing step, an arc plate is press-fitted between the through hole of the lower ground improvement body through which the friction pile has penetrated and the upper portion of the friction pile The fixing member press-fitting step and the soil dug down by the dug-down step are backfilled on the upper side of the lower ground improvement body, the surface layer portion of the ground is dug into the shape of the upper ground improvement body, and solidified material and water are injected. A secondary improvement step of forming the upper ground improvement body by compacting after mixing and stirring, and a foundation placement step of placing the foundation of the building on the upper ground improvement body. (Claim 3 ).

As described above, according to the liquefaction countermeasure basic structure according to the present invention,
(A) The friction pile with the upper part fitted in the pile support hole that penetrates the lower ground improvement body up and down compacts the loose liquefaction layer and suppresses shear deformation during earthquakes, so liquefaction and lateral flow And being able to control subsidence,
(B) When friction piles including wooden piles or bamboo piles are used, they are low in cost, and are light and have a large surface frictional resistance, so the settlement suppression effect is great.
(C) When friction piles including wooden piles are used, a large amount of timber (thinned wood) is effectively fixed and fixed underground, so that not only forestry promotion but also carbon storage effects can contribute to CO ₂ reduction. ,
(D) When using a friction pile with the upper part being a non-permanent pile, the lower wooden pile or bamboo pile is constructed so as not to touch the air, so that the strength does not decrease over a long period of time.
(E) is provided with the arcuate plate member that is press-fitted between the piles supporting hole of the lower ground improvement body and upper friction piles, during an earthquake, the friction piles so as to suppress the shear deformation of the ground immediately below Can sufficiently restrain the inclination of the liquefaction, so that a sufficient liquefaction suppression effect can be obtained,
There are remarkable effects such as.

Further, according to the liquefaction countermeasure method according to the present invention,
( F ) The primary improvement process to form the lower ground improvement body and the secondary improvement process to form the upper ground improvement body are methods of compaction after mixing and stirring while injecting solidified material and water, thus reducing construction costs. What you can do,
( G ) Since the friction pile is driven so as to hang down from the lower surface of the lower ground improvement body through the unconsolidated lower ground improvement body up and down through the primary improvement process, the continuity of construction improves. Therefore , the construction cost can be further reduced ,
There are remarkable effects such as.

It is a longitudinal cross-sectional view which shows the principal part of the liquefaction countermeasure foundation structure which concerns on embodiment of this invention. It is a plan view, (a) is a state where the lower ground improvement body is formed through the primary improvement process, and the friction pile is driven through the friction pile driving process, (b) is the lower part through the secondary improvement process The state which the upper ground improvement body was formed on the ground improvement body is shown. It is arrow XX sectional drawing of FIG.2 (b). It is a longitudinal cross-sectional view which shows an example of a connection member. (A) is a longitudinal cross-sectional view which shows the example of a fixing member (fixing member press-fit process), (b) is a ZZ cross-sectional view of (a).

Next, the fixing member F press-fitted between the pile support hole h of the lower ground improvement body 1 and the upper part of the friction pile P will be described.
In the state where the friction piles P, P,... Are placed so as to penetrate the lower ground improvement body 1 that has not been consolidated through the primary improvement process in the friction pile placement process, the lower ground improvement body 1 is cured. Depending on the degree, looseness (gap) may occur between the pile support hole h, that is, the through hole h that penetrates the lower ground improvement body 1 and the upper portion of the friction pile P.
In FIG. 6 described below, the looseness (gap) is enlarged (exaggerated) for convenience of explanation (in consideration of visibility).

If there is such a looseness (clearance), the upper support of the friction pile P is not sufficient, and the friction pile P is controlled so as to suppress the shear deformation of the soil element between the friction piles P, P,. , P,... Cannot be sufficiently constrained, and therefore , as shown in the longitudinal sectional view of FIG. 6A and the cross-sectional plan view of FIG. between the arcuate plate 11, 11, 11 having a thickness of about 1cm which is a fixed member F, press-fitted by using an arm or the like of heavy equipment in the usual construction site.
Or when the friction pile P is comprised only with the wooden piles 5, 5, ..., the radial direction cut | offset of the radial direction of about 3 cm or three in the circumferential direction equally on the upper surface of the top wooden pile 5 is carried out. The upper portion of the wooden pile 5 is enlarged by inserting a tapered timber (for example, 5 mm thick at the tip and 15 mm thick at the leading end) into the cut with a mallet or the like. You may do it.

A Liquefaction countermeasure basic structure C Connecting member D1 Lower ground improvement body thickness D2 Upper ground improvement body thickness d Friction pile diameter F Fixed member G Ground GL Ground surface H Hole h Pile support hole (through hole)
L Length of friction pile P Friction pile WL Groundwater level (groundwater surface)
1 Lower ground improvement body 1A Upper surface 1B Lower surface 2 Upper ground improvement body 2A Upper surface 2B Lower surface 3 Building foundation 4 Concrete pile (non-rotatable pile)
5 Wooden pile 5A Upper surface 5B Lower surface 6 Steel pipe 7, 8, 9 Wedge 11 Arc-shaped board

It is a longitudinal cross-sectional view which shows the principal part of the liquefaction countermeasure foundation structure which concerns on embodiment of this invention. It is a plan view, (a) is a state where the lower ground improvement body is formed through the primary improvement process, and the friction pile is driven through the friction pile driving process, (b) is the lower part through the secondary improvement process The state which the upper ground improvement body was formed on the ground improvement body is shown. It is arrow XX sectional drawing of FIG.2 (b). It is a longitudinal cross-sectional view which shows an example of a connection member. (A) is a longitudinal cross-sectional view which shows the example of a fixing member (fixing member press-fit process), (b) is a ZZ cross-sectional view of (a).

Next, the fixing member F press-fitted between the pile support hole h of the lower ground improvement body 1 and the upper part of the friction pile P will be described.
In the state where the friction piles P, P,... Are placed so as to penetrate the lower ground improvement body 1 that has not been consolidated through the primary improvement process in the friction pile placement process, the lower ground improvement body 1 is cured. Depending on the degree, looseness (gap) may occur between the pile support hole h, that is, the through hole h that penetrates the lower ground improvement body 1 and the upper portion of the friction pile P.
In FIG. 5 described below, the looseness (gap) is shown enlarged (exaggerated) for convenience of explanation (for ease of viewing).

If there is such a looseness (clearance), the upper support of the friction pile P is not sufficient, and the friction pile P is controlled so as to suppress the shear deformation of the soil element between the friction piles P, P,. , P,... Cannot be sufficiently constrained. Therefore, as shown in the longitudinal sectional view of FIG. 5A and the cross-sectional plan view of FIG. In between, arc-shaped board | plate material 11,11,11 about 1 cm thick which is the fixing member F is press-fit using the arm of a heavy machine in a normal construction site, etc.
Or when the friction pile P is comprised only with the wooden piles 5, 5, ..., the radial direction cut | offset of the radial direction of about 3 cm or three in the circumferential direction equally on the upper surface of the top wooden pile 5 is carried out. The upper portion of the wooden pile 5 is enlarged by inserting a tapered timber (for example, 5 mm thick at the tip and 15 mm thick at the leading end) into the cut with a mallet or the like. You may do it.

Claims (7)

A basic structure for taking measures against liquefaction of buildings during an earthquake,
Lower ground improvement body whose upper surface is located below the ground surface,
A plurality of friction piles hanging from the lower surface of the lower ground improvement body, constituted by a plurality of wooden piles or bamboo piles whose upper portions are fitted in a plurality of pile support holes penetrating the lower ground improvement body up and down;
An upper ground improvement body formed on the lower ground improvement body, and
The foundation of the building placed on the upper ground improvement body,
A liquefaction countermeasure basic structure characterized by comprising: A basic structure for taking measures against liquefaction of buildings during an earthquake,
Lower ground improvement body whose upper surface is located below the ground surface,
The upper part is fitted into a plurality of pile support holes penetrating the lower ground improvement body up and down, and the lower end is connected and fixed to the lower end part of the non-destructive pile and the non-destructive pile located below the groundwater level. A plurality of friction piles hanging from the lower surface of the lower ground improvement body, constituted by wooden piles or bamboo piles,
An upper ground improvement body formed on the lower ground improvement body, and
The foundation of the building placed on the upper ground improvement body,
A liquefaction countermeasure basic structure characterized by comprising:   The liquefaction countermeasure foundation structure according to claim 1 or 2, wherein the lower ground improvement body is formed with a plurality of holes penetrating vertically so as to partition the inner region into a plurality of parts.   The liquefaction countermeasure foundation structure according to any one of claims 1 to 3, further comprising a fixing member press-fitted between a pile support hole of the lower ground improvement body and an upper portion of the friction pile. A lower ground improvement body having an upper surface located below the ground surface, a plurality of friction piles supported by the lower ground improvement body, an upper ground improvement body on the lower ground improvement body, and the upper ground improvement body This is a construction method for liquefaction countermeasures for buildings in the event of an earthquake.
A digging process for digging the upper side of the lower ground improvement body in accordance with the planar shape of the lower ground improvement body, the surface layer portion of the ground where liquefaction is expected to occur,
Excavating the surface layer portion of the ground into the shape of the lower ground improvement body, primary improvement step of forming the lower ground improvement body by compacting after mixing and stirring while injecting solidified material and water;
A plurality of friction piles made up of wooden piles or bamboo piles, or non-decayable piles and wooden piles or bamboo piles that are connected and fixed to the lower end of the non-decayable piles are not solidified through the primary improvement process. Friction pile driving step for driving the lower ground improvement body in a bonded state vertically and penetrating from the lower surface of the lower ground improvement body,
The soil dug down by the dug process is backfilled above the lower ground improvement body, the surface layer portion of the ground is dug into the shape of the upper ground improvement body, and mixed and stirred while injecting solidifying material and water, and then compacted. Secondary improvement step for forming the upper ground improvement body,
A foundation placing step of placing the foundation of the building on the upper ground improvement body;
A liquefaction countermeasure method characterized by containing.   The liquefaction countermeasure method according to claim 5, wherein the lower ground improvement body is formed with a plurality of holes penetrating vertically so as to partition the inner region into a plurality. 7. The fixing member press-fitting step of press-fitting a fixing member between the through hole of the lower ground improvement body through which the friction pile penetrates and the upper portion of the friction pile after the friction pile placing step. The liquefaction countermeasure method described.

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