JP6308491B2 - Pile-type liquefaction countermeasure structure and its construction method - Google Patents

Description

  The present invention relates to a pile type liquefaction countermeasure structure for a ground having a liquefied layer and a construction method thereof, and relates to a technique for preventing lateral flow of the liquefied layer during an earthquake.

  In order to improve the ground where the liquefied layer is present, a deep mixing treatment method in which a cement-based solidifying agent is stirred and mixed to solidify the ground into a columnar shape is widely used. Since the deep mixing treatment method has less vibration and noise during construction, its high applicability to construction in urban areas and construction close to existing structures is evaluated. As an improved form of the deep mixed processing method, an alignment arrangement in which a plurality of independent piles 3 as shown in FIG. 13 (A) are arranged at the vertices of a continuously arranged square, or an independent arrangement as shown in FIG. 13 (B). A plurality of piles 3 are arranged in each row as shown in FIG. 13 (C) in addition to a pile-type improvement such as a staggered arrangement in which two congruent equilateral triangles are combined and arranged at the top of a rhombus continuously arranged. Wall type improvement that forms a wall-like improved body by connecting the piles 3 in an overlapped state, as shown in FIG. 13 (D), a lattice type in which the wall-like improved bodies are arranged in a square lattice shape Improvements and block improvements that improve the entire ground are known.

  Among these improvements, the improvement effects such as improvement of the ground support and prevention of liquefaction of the ground are the highest in the block type improvement and the lowest in the pile type improvement. On the other hand, since the pile type improvement does not have an overlap portion of the pile, it has a feature that the construction efficiency is higher than that of the block type improvement and the lattice type improvement, and the material cost can be kept low. Therefore, there is a certain advantage in the pile type improvement in the ground improvement such as the harbor part where the heavy structure is not constructed in the upper part. In addition, when performing ground improvement by arranging a plurality of piles so as to be separated from each other in this way, not only the improved pile (pile-shaped improved ground) by the above-mentioned deep mixed treatment method but also ready-made piles and cast-in-place piles It is also possible to use.

  As a method of improving the effect of preventing liquefaction by improving the pile type, Patent Document 1 discloses that a wall-like improvement body formed by a deep mixing treatment method is formed in an annular shape along the outer periphery of the area to be improved, and the wall-like improvement body is surrounded by In the area to be improved, a liquefaction countermeasure method has been proposed in which a pile-type improvement method using a deep mixed processing method is performed using a cement-based material that expands during curing.

  Moreover, as described above, in the pile type improvement, the alignment arrangement and the staggered arrangement are common, but in such an arrangement, there is an unimproved area between pile rows, and this unimproved area extends in the row direction. As it is easy to liquefy due to the presence of multiple piles, it is arranged as if they were randomly arranged while arranging multiple piles with a certain regularity. A method of arranging piles (Patent Document 2) that has been shortened to suppress liquefaction of the ground has also been proposed. In patent document 2, the improvement layer is constructed | assembled in the upper part of the ground, and the fall of each pile at the time of an earthquake etc. is aimed at by connecting the head of a some pile with an improvement layer.

Japanese Patent No. 3624514 JP 2011-196173 A

  However, the liquefaction countermeasure method described in Patent Document 1 uses a special material that expands during curing, which increases the material cost. Moreover, since this method cannot prevent the pile from falling, it is difficult to suppress the lateral flow of the ground when the ground is liquefied.

  On the other hand, even if the improvement layer is constructed so as to connect the heads of the piles as in Patent Document 2, the pile is prevented from overturning against a lateral force exceeding the frictional force between the improvement layer and the upper surface of the pile. Can not. And in the ground where there is uneven earth pressure such as revetment, such a large force may occur due to liquefaction, and when liquefaction occurs in such ground, the pile will have its upper surface against the improved layer. The revetment wall may be damaged by the overburden pressure increased by liquefaction and the lateral flow of the liquefied ground.

  The present invention has been made in view of such a background, and can prevent the lateral flow of the liquefied layer easily and inexpensively without using a special material. And it aims at providing the construction method.

  In order to solve the above-mentioned problems, the pile type liquefaction countermeasure structure (1) of the ground according to the present invention has a plurality of structures constructed so as to be separated from each other on the ground (G) where the liquefied layer (5) exists. A pile (3) and a plate-like structure (6) provided so as to surround the head (3a) of each pile, and the head of each pile extends over a predetermined height (t) The structure is fixed to the structure.

  According to this structure, since the plate-like structure fixes the head of each pile over a predetermined height, when the liquefied layer is liquefied, the pile is prevented from overturning, and the liquefied ground side flow Can be suppressed.

  Moreover, according to one aspect of the present invention, the plate-like structures are connected to each other, and a plurality of plate pieces (precast) in which a plurality of through holes (10) are formed in advance corresponding to the positions of the piles. It can be configured by a concrete plate 7).

  When a plate-like structure is composed of an improved layer, the thickness of the improved layer must be increased in order to fix the pile head to the extent that the pile can be prevented from falling when the ground liquefies. Therefore, it takes cost and labor. On the other hand, according to this configuration, a plate-like structure can be easily constructed. Also, if the plate-like structure has a predetermined strength and is previously installed on the ground, even if the ground is so weak that it is necessary to take measures against scaffolding such as a laid iron plate for heavy machinery for pile construction Without taking such measures, it is possible to carry heavy equipment for building piles onto the ground. Moreover, since the several through-hole is previously formed in the plate-shaped structure, a plate-shaped structure can be used as a ruler, and the positioning of a pile can be made unnecessary. In addition, when performing positioning, there is a possibility that the construction will be interrupted until the mark disappears during construction and the positioning is performed again, but the through hole indicates the position of the pile, and the position becomes unknown Since this is not the case, such a situation can be prevented.

  Moreover, according to one side of this invention, the structure by which the head of each said pile was fixed to the said plate-shaped structure with the filler (13) with which it filled between the said plate-shaped structure and the said pile, and can do.

  According to this structure, the head of a pile can be reliably fixed to a plate-like structure regardless of the type of the pile.

  Moreover, according to one aspect of the present invention, the plurality of piles (3) are deep mixed piles formed by using at least a high-pressure injection method, and a solidifying material is applied to the inner surface of the through hole of the plate-like structure. It can be set as the structure by which each pile was fixed to the said plate-shaped structure by spraying so that it may reach and forming the pile head.

  According to this structure, the head of a pile can be fixed to a plate-shaped structure, without filling the filler which solidifies between the through-hole of a plate-shaped structure, and the said pile. Therefore, construction can be facilitated.

  Moreover, in order to solve the said subject, the construction method of the pile-type liquefaction countermeasure structure (1) of the ground which concerns on this invention is a plate-like structure on the ground (G) in which a liquefaction layer (5) exists. A step of installing (6), a step of constructing a plurality of piles (3) spaced apart from each other in the ground on the plate-like structure, and a head (3a) of each pile having a predetermined height (t ) Over the plate-like structure.

  According to this method, since the plate-like structure can be installed on the ground in advance, even if the ground is soft enough to require scaffolding measures such as a laying iron plate for heavy machinery for pile construction, Without taking such measures, it is possible to carry heavy equipment for pile construction onto the ground. Moreover, since the plate-like structure fixes the head of each pile over a predetermined height, when the liquefied layer is liquefied, the pile is prevented from falling and the lateral flow of the liquefied ground is suppressed. Can do.

  Further, according to one aspect of the present invention, in the step of installing the plate-like structure (6), a plurality of plate pieces (precast concrete plate 7) are arranged on the ground and adjacent plate pieces are arranged. In the step of installing a plate-like structure having a plurality of through-holes (10) spaced apart from each other and constructing the plurality of piles (3), a configuration in which each pile is constructed at the position of the through-holes It can be.

  When a plate-like structure is composed of an improved layer, the thickness of the improved layer must be increased in order to fix the pile head to the extent that the pile can be prevented from falling when the ground liquefies. Therefore, it takes cost and labor. On the other hand, according to this method, a plate-like structure can be easily constructed. Moreover, according to this structure, since the several through-hole is previously formed in the plate-shaped structure body, a plate-shaped structure body can be used as a ruler and the positioning of a pile can be made unnecessary. In addition, when performing positioning, there is a possibility that the construction will be interrupted until the mark disappears during construction and the positioning is performed again, but the through hole indicates the position of the pile, and the position becomes unknown Since this is not the case, such a situation can be prevented.

  Moreover, according to one side of this invention, in the step which fixes the head (3a) of each said pile to the said plate-shaped structure, the through-hole (10) of the said plate-shaped structure, the said pile (3), It can be set as the structure filled with the filler (13) which solidifies between.

  According to this method, the head of the pile can be reliably fixed to the plate-like structure regardless of the type of the pile.

  According to one aspect of the present invention, in the step of constructing the plurality of piles (3), a deep mixed pile is constructed using at least a high-pressure injection method, and the heads (3a) of the respective piles are In the step of fixing to the plate-like structure, the solidified material is sprayed so as to reach the inner surface of the through-hole (10) of the plate-like structure to form a pile head (3a), whereby each pile is formed into the plate-like structure. It can be set as the structure fixed to a structure.

  According to this method, the head of the pile can be fixed to the plate-like structure without filling the filler that solidifies between the through hole of the plate-like structure and the pile. Therefore, construction can be facilitated.

  Thus, according to the present invention, there is provided a pile-type liquefaction countermeasure structure for ground and a method for constructing the same, which can suppress the lateral flow of the liquefied layer easily and inexpensively without using a special material. can do.

Sectional view of a pile type liquefaction countermeasure structure according to the present invention Plan view of the pile type liquefaction countermeasure structure shown in FIG. Main part perspective view of the pile type liquefaction countermeasure structure shown in FIG. Explanatory drawing of the construction method of the pile type liquefaction countermeasure structure shown in FIG. Explanatory drawing of the construction method of the pile type liquefaction countermeasure structure shown in FIG. Cross-sectional view of relevant parts of a pile-type liquefaction countermeasure structure according to a modification The principal part perspective view of the pile type liquefaction countermeasure structure which concerns on other embodiment) Plan view of a pile type liquefaction countermeasure structure according to another embodiment Sectional drawing of the principal part of the pile type liquefaction countermeasure structure which concerns on other embodiment Pile surfacing diagram of a pile type liquefaction countermeasure structure according to another embodiment Plan view of the pile type liquefaction countermeasure structure shown in FIG. Plan view of a pile type liquefaction countermeasure structure according to another embodiment Pile pile diagram showing examples of pile arrangement according to the prior art

  Hereinafter, a pile type liquefaction countermeasure structure 1 and a construction method thereof according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, the pile type liquefaction countermeasure structure 1 according to the present embodiment is applied to the ground G in which the liquefied layer 5 exists on the non-liquefied layer 4 divided by the revetment structure 2. Has been. Revetment structure 2 is composed of a like vertically installed steel sheet pile or steel sheet pile at the boundary between land and sea, it is entered with a predetermined embedment length L ₁ in the non-liquefaction layer 4. The revetment structure 2 may be a self-supporting type, a tie rod type, or other types. The soil pressure is acting on the upper part of the revetment structure 2, and if the liquefied layer 5 is liquefied, the uneven pressure increases and the revetment structure 2 may be damaged. The structure 1 is applied.

The pile type liquefaction countermeasure structure 1 includes a plurality of piles 3 constructed on the ground G, and a plate-like structure 6 constructed on the top of the ground G so as to connect the heads 3a of the plurality of piles 3. It is a pile-type structure provided. Pile 3 in this embodiment is used off-the-shelf piles, and the non-liquefaction layer 4 rush with predetermined embedment length L _2. As shown in FIG. 2, the piles 3 are arranged (arranged) in a lattice shape at equal intervals in two directions orthogonal to each other on the horizontal plane (hereinafter referred to as X direction and Y direction). As the pile 3, for example, a concrete pile, a steel pipe pile, an SC pile (Steel and Concrete Composite pile) or the like can be used.

  In addition, as the pile 3, the deep mixed pile constructed | assembled by the deep mixed process can also be used. When the pile 3 is a deep mixed pile, the deep mixed pile may be constructed by any of the mechanical stirring method, the mechanical stirring combined use type high pressure injection method, and the high pressure injection method.

  The plate-like structure 6 is integrated by connecting a plurality of precast concrete plates 7 by a connecting mechanism 8 (connecting means). In addition, between the precast concrete board 7 closest to the revetment structure 2 and the revetment structure 2, a connecting portion 9 made of cast-in-place concrete is constructed, so that the plate-like structure 6 becomes the revetment structure 2. It does not move to the side (sea side). A plurality of through holes 10 are formed at positions corresponding to the piles 3 in the plate-like structure 6, and the piles 3 are constructed so that the heads 3 a are accommodated in the respective through holes 10.

Each precast concrete plate 7 is the size of the square having twice the dimension L ₄ of the X and Y directions to the distance L ₃ of each pile 3 in plan view, all the precast concrete plate 7 are the same size And the same shape. Each through-cast concrete plate 7 is formed with four through holes 10.

  As shown in FIG. 3, in the vicinity of each side of the precast concrete plate 7, a bolt provided with a bolt insertion hole 11 that is recessed so as to open on the upper surface and opens on the inner surface and the side surface of the precast concrete plate 7. Two boxes 12 (concave portions) are formed. That is, in this embodiment, the precast concrete boards 7 adjacent to each other are connected by unillustrated cutting bolts (full screws) and nuts installed in the respective bolt boxes 12 facing each other, and these bolts, nuts, and bolt boxes 12 are connected. Thus, the connecting mechanism 8 is configured.

  The through-hole 10 of the precast concrete plate 7 is larger than the outer diameter of the pile 3 so that a gap S is generated between the pile 3 (the outer peripheral surface of the head 3a) and the precast concrete plate 7 (the inner surface of the through-hole 10). The diameter is large, and here, the cross-sectional shape is a columnar shape. However, it is good also as a taper shape easy to remove in consideration of the effort at the time of manufacturing the precast concrete board 7. FIG.

  The pile 3 installed inside the through hole 10 is constructed such that the upper end 3 b is flush with the upper surface of the plate-like structure 6. The gap S between the pile 3 and the precast concrete plate 7 is filled with a filler 13 such as a non-shrink mortar. Thus, the plate-like structure 6 surrounds the head 3a of the pile 3 over the entire thickness t, and connects the heads 3a of all the piles 3 whose lower ends are fixed by the non-liquefaction layer 4. Thus, each pile 3 is fixed with the whole thickness t. The thickness t of the precast concrete board 7 is preferably 500 mm or more and less than 1000 mm. When the thickness t is smaller than 500 mm, the effect of fixing the head of the pile 3 is lowered. On the other hand, when the thickness t is 1000 mm or more, the handling of the concrete plate 7 is complicated although it is advantageous for fixing the head of the pile. It is.

  Next, with reference to FIG. 4 and FIG. 5, the construction method of the pile type | mold liquefaction countermeasure structure 1 is demonstrated. First, as shown in FIG. 4A, the ground G partitioned by the revetment structure 2 is leveled and flattened. At this time, the height of the ground G is set lower than the upper end of the revetment structure 2 so that the plate-like structure 6 to be constructed can be connected to the side surface of the revetment structure 2. Thereafter, the plate-like structure 6 constructed on the ground G is positioned. In order to locate the plate-like structure 6, it is only necessary to mark one corner and only the direction of one side constituting the corner, but it is preferable to mark four corners and four sides.

  Next, as shown in FIG. 4 (B), adjacent precast concrete plates 7 are connected to each other by a connecting mechanism 8 (see FIG. 3) while laying the precast concrete plates 7 at predetermined positions, so that the plate-like structures 6 Build up. After connecting all the precast concrete plates 7, the concrete is placed between the precast concrete plate 7 closest to the revetment structure 2 and the revetment structure 2 to construct the connecting portion 9.

After the construction of the plate-like structure 6, as shown in FIG. 4C, the pile 3 is constructed in the ground G from the through hole 10 of the plate-like structure 6 on the plate-like structure 6. In addition, the pile 3 may be constructed by any method such as a press-fitting method, a batting method, a pre-boring method, a digging method, and a rotating method. In any construction method, a heavy machine is usually used when constructing the pile 3, but since the plate-like structure 6 is constructed first, the heavy machine can be carried directly onto the ground G. The pile 3 has a predetermined penetration length L ₂ with respect to the non-liquefied layer 4, the upper end 3 b is set to a length that matches the upper surface of the plate-like structure 6, and the pile 3 is placed in all the through holes 10. To construct.

  In the state where the pile 3 is constructed, as shown in FIG. 5C, the head 3a of the pile 3 is accommodated inside the through hole 10 of the plate structure 6, and the pile 3 and the plate structure 6 (through hole) A gap S is formed between the inner surface 10 and the inner surface 10. Alternatively, when the earth and sand of the ground G has entered the gap S, the earth and sand are removed, and the gap S is formed over the thickness t of the plate-like structure 6.

  Then, as shown in FIG. 5D, the gap S is filled with a filler 13 such as a non-shrink mortar. Thereby, when the filler 13 is solidified, the pile 3 and the plate-like structure 6 are integrated, and the heads 3 a of all the piles 3 are fixed by the plate-like structure 6.

  In addition, it is good to provide the grout injection | pouring hole 21 penetrated up and down in the appropriate place in the precast concrete board 7, as shown with an imaginary line in FIG. Note that the grout injection hole 21 is closed by a ridge when not in use. If the grout injection hole 21 is provided, the grout can be injected from the grout injection hole 21 when it is desired to fill a gap generated between the precast concrete plate 7 and the ground G. When such an operation is performed, the operation may be performed after the filling operation of the filler 13 in FIG. Moreover, even if it is not necessary to inject grout into the lower surface of the plate-like structure 6 when the pile type liquefaction countermeasure structure 1 is constructed, if the grout injection hole 21 is provided, the pile type liquefaction countermeasure structure is provided. When a cavity is generated under the plate-like structure 6 due to liquefaction due to earthquake after the construction of the body 1, it can be used as an injection hole for filling the cavity with grout. It is possible to facilitate the restoration work of the countermeasure structure 1.

Thus, according to configuration or the constructed pile type liquefaction countermeasure structure 1, the liquid of the liquid layer 5 by pile 3 is installed at a predetermined density corresponding to the distance L ₃ and pile diameter in plan view While the liquefaction is suppressed, even if the liquefied layer 5 is liquefied due to a large shaking, the flow to the side (sea side) of the liquefied liquefied layer 5 is suppressed by the pile 3. Further, the liquefied liquefied layer 5 tries to flow laterally while the pile 3 is overturned, but the pile 3 is fixed to the head 3 a (side surface) by the plate-like structure 6. Therefore, the lateral flow of the liquefied layer 5 can be suppressed.

  Moreover, in this embodiment, since the ready-made pile which is a general purpose product is used for the pile 3, the pile 3 can be constructed | assembled easily and the plate-shaped structure 6 can be constructed | assembled cheaply. Further, since the plate-like structure 6 is constructed by connecting a plurality of precast concrete plates 7, the pile 3 can be constructed after the plate-like structure 6 in which the through-holes 10 are formed in advance is installed on the ground G. There is no need to lay iron sheets for carrying in. Moreover, it is not necessary to position the pile 3. In addition, when positioning is performed, there is a possibility that the construction is interrupted until the mark disappears during construction and the positioning is performed again. However, the through hole 10 indicates the position of the pile 3, and the position is This situation does not occur because there is nothing that can be lost. Therefore, construction is easy.

  In this embodiment, since the filler 13 is filled between the plate-like structure 6 and the pile 3 and the head 3 a of each pile 3 is fixed to the plate-like structure 6, it depends on the type of the pile 3. It is possible to securely fix the head 3 a of the pile 3 to the plate-like structure 6.

  In addition, as shown in FIG. 6 which shows a modification, by providing the unevenness | corrugation 14 in at least one of the inner surface of the plate-like structure 6, and the side surface of the head 3a of the pile 3, the plate-like structure 6 and the pile 3 are provided. The bond strength can be improved.

  Next, with reference to FIG. 7, the pile type | mold liquefaction countermeasure structure 1 which concerns on other embodiment is demonstrated. In addition, the same code | symbol is attached | subjected to the member and site | part which are common in the said embodiment, and the overlapping description is abbreviate | omitted. The same applies to other embodiments described below.

  In the present embodiment, a mortise joint is used as the coupling mechanism 8 instead of the bolt and nut. That is, tenons 15 (protrusions) that widen toward the front end in a plan view are provided on two sides that are one of the two opposite sides of the precast concrete board 7, and a plan view is provided on the other two sides. A mortise groove 16 (a dovetail groove) is formed which widens toward the groove bottom. The mortise 15 and the mortise groove 16 have a constant cross-sectional shape and extend in the vertical direction. The precast concrete board laid later in the mortise 15 or the mortise groove 16 of the precast concrete board 7 laid first. By inserting the ten mortise grooves 16 or the tenon grooves 15 from above, the tenon grooves 15 and the tenon grooves 16 are engaged with each other, and the precast concrete adjacent to each other is connected.

  In the illustrated example, two mortises 15 are formed on each of the two sides of the precast concrete plate 7 and two mortise grooves 16 are formed on each of the other two sides. A form in which one or three or more tenon grooves 16 are formed, a form in which tenon 15 and tenon grooves 16 are formed on each side, and the like can also be employed.

  By using a tenon joint as the connecting mechanism 8 in this manner, the fastening work between the bolt and the nut, which is necessary in the above embodiment, can be omitted, and the construction can be made easier.

  In addition, when using the tenon joint as the connection mechanism 8, it is necessary to provide play at the engaging portion between the tenon 15 and the tenon groove 16 from the viewpoint of workability, and the adjacent precast concrete plates 7 are brought into close contact with each other. It is difficult. Therefore, the joint material may be filled in the gap between the precast concrete plates 7 adjacent to each other. When the joint material is not filled, the precast concrete plates 7 adjacent to each other are connected only in the horizontal direction. However, by filling the joint material, the precast concrete plates 7 adjacent to each other are also connected in the vertical direction. A fixed state can be obtained, and the lateral flow of the liquefied layer 5 when the liquefied layer 5 is liquefied can be more effectively suppressed.

  Furthermore, with reference to FIG. 8, the pile type | mold liquefaction countermeasure structure 1 which concerns on other embodiment is demonstrated. In the present embodiment, the tension material 17 is used as the connecting mechanism 8. In each precast concrete plate 7, a sheath (not shown) for inserting the tension material 17 in a position avoiding the through hole 10 is embedded in the X direction and the Y direction, and after laying all the precast concrete plates 7, The plurality of precast concrete plates 7 are integrated by inserting the tension members 17 into the continuous sheaths and tensioning the tension members 17 at both ends of each row of the precast concrete plates 7 to apply post tension. As the tension material 17, a PC steel wire, a PC steel rod, a PC steel strand, an aramid fiber, or the like can be used. The tendon 17 may be fixed by injecting grout into the sheath, or may be fixed by installing fixing tools (not shown) at both ends of the plate-like structure 6. Thus, when integrating the several precast concrete board 7 with the tension material 17, about the connection part 9 which is a part of the plate-shaped structure 6, after integrating all the precast concrete boards 7, it is concrete. To cast.

  Thus, by using the tension material 17 as the connection mechanism 8, a plurality of precast concrete plates 7 can be connected at a time. Therefore, construction efficiency can be improved.

  Next, with reference to FIG. 9, the pile-type liquefaction countermeasure structure 1 which concerns on another embodiment, and its construction method are demonstrated. In the present embodiment, as the pile 3, a deep mixed pile constructed by a mechanical stirring combined type high pressure injection method or a high pressure injection method is used, and the pile 3 is integrated with the plate-like structure 6 without using the filler 13. I am letting. The through holes 10 of the plate-like structure 6 are provided with irregularities 14 on the inner surface in order to increase the bonding strength with the pile 3. The pile 3 is constructed after constructing the plate-like structure 6 as in the above embodiment.

  Hereinafter, the construction procedure of the pile 3 will be described. The pile 3 is constructed upward from the lower end by mechanically stirring the solidified material in the ground G or by high-pressure injection. Here, the lower part 3c below the head 3a of the pile 3 is constructed so as to have a constant cross-sectional shape smaller than the through hole 10 of the plate-like structure 6 by a mechanical stirring method. On the other hand, the upper part (head 3a) of the pile 3 is constructed so as to have a larger cross-sectional shape than the lower part 3c constructed by a mechanical stirring method using at least a high-pressure injection method. Therefore, the entire region in the through hole 10 is the pile 3 inside the through hole 10 of the plate-like structure 6, and the diameter of the pile 3 is smaller than the diameter of the through hole 10 immediately below the plate-like structure 6. Is also getting bigger.

  By constructing the pile 3 in this way, the pile 3 is integrated with the plate-like structure 6 at the same time as construction (simultaneously with solidification), and the pile 3 and the plate-like structure 6 are filled after the pile 3 is constructed. There is no need to fill the material 13, and construction is easy. Moreover, the head 3a of the pile 3 is constructed by using a high-pressure injection method together, and has a higher strength than that of the lower portion 3c because the amount of the solidified material is larger than that of the lower portion 3c. Therefore, even if the force which falls by the liquefaction of the liquefied layer 5 acts on the pile 3, it is suppressed that the pile 3 is damaged in the part directly under the plate-like structure 6 where stress concentrates.

  Next, with reference to FIG. 10 and FIG. 11, the pile-type liquefaction countermeasure structure 1 which concerns on another embodiment, and its construction method are demonstrated. In this embodiment, the piles 3 are arranged as if they were random. First, the arrangement of the piles 3 will be described with reference to FIG. First, an arbitrary X direction on the plane of the ground G to be improved and a Y direction that intersects the X direction at a predetermined angle (90 degrees here) are set. Then, the pile 3 is arranged at an arbitrarily set point p1, and a point p2 having a distance d1 from the point p1 in the X direction and a point p3 having a distance d2 (here d2 = d1) from the point p1 to the Y direction. The pile 3 is arranged at a point p4 having a distance d2 from the point p2 in the Y direction (having a distance d1 from the point p3 in the X direction), and these four piles 3 are defined as one pile group P. In addition, m columns (m is an integer of 2 or more, m = 2 here) are arranged in the X direction with a center distance of d1, and n columns (n is an integer of 2 or more) in the Y direction with a center distance of d2. Here, n = 2) One pile group P may be configured from the m × n piles 3 arranged.

  Next, the center of the pile group P, that is, the center of a square formed by connecting the point p1, the point p2, the point p4, and the point p3 in this order is defined as a group center C. Then, with respect to one pile group P, another pile group P is disposed adjacent to the substantially X direction, and another pile group P is disposed adjacent to the substantially Y direction. The “abbreviation” here will be described later. Hereinafter, in order to specify each pile group P and each group center C according to the arrangement, the reference numbers P and C indicate the array numbers in the approximate X direction and the approximate Y direction in parentheses after the symbols P and C. For example, a reference pile group P is written as a pile group P (1, 1), and a pile group P arranged adjacent to the substantial X direction is written as a pile group P (2, 1). The pile group P arranged adjacently in the substantially Y direction is referred to as a pile group P (1, 2). An arbitrary pile group P is referred to as a first pile group P (n, n), and the pile group P arranged adjacent to the arbitrary pile group P in the substantially X direction is a second pile group P (n + 1, The pile group P which is referred to as n) and is adjacent to the arbitrary pile group P in the substantially Y direction will be referred to as a third pile group P (n, n + 1).

  The arrangement of the pile groups P is specifically performed as follows. First, a distance of d1 × m (here d1 × 2) in the X direction from the group center C (n, n) of the first pile group P (n, n) and a distance of d2 × 0.5 in the Y direction The m × n (in this case, four) piles 3 constituting the second pile group P (n + 1, n) are arranged at each point (four in this case) so that the points separated by a distance become the group center C (n + 1, n). Here, it arrange | positions to p1-p4). The arrangement direction of the pile group P shifted by 0.5 rows in accordance with such a predetermined rule is referred to as “substantially X direction” in this description. Further, the distance from the group center C (n, n) of the first pile group P (n, n) in the Y direction is d2 × n (here d2 × 2), and the distance in the X direction is d1 × 0.5. The m × n (in this case, four) piles 3 constituting the third pile group P (n, n + 1) are arranged at the respective points (four in this case) so that the points separated by a distance become the group center C (n, n + 1). Here, it arrange | positions to p1-p4). The arrangement direction of the pile group P according to such a predetermined rule is referred to as “substantially Y direction” in the present description.

  In this procedure, all the pile groups P are assumed to be the first piles P (n, n), and then adjacent to the second pile group P (n + 1, n) that is substantially adjacent to the X direction and substantially Y direction. A third pile group P (n, n + 1) is arranged. Then, the group center C (n + 1, n + 1) of the pile group P (n + 1, n + 1) arranged adjacent to the second pile group P (n + 1, n) in the substantially Y direction, and the third pile group P (n , N + 1) and the group center C (n + 1, n + 1) of the pile group P (n + 1, n + 1) arranged adjacent to each other substantially in the X direction are both the group center C ( n, n) to the X direction, d1 × (m + 0.5), (here d1 × 2.5), and Y direction d2 × (n + 0.5), (here d2 × 2.5) They will come to a position that is a distance away, and will match each other. That is, the group center C of each pile group P becomes a lattice point of a plane lattice, and a total of four pile groups P of 2 groups in the substantially X direction and 2 groups in the substantially Y direction repeatedly appear. In this way, the above procedure is performed for all the pile groups P, and m × n (here, 4) piles 3 are sequentially arranged at each point (here, p1 to p4), while following a certain rule. The piles 3 are arranged as if they were randomly arranged in all the improvement target areas of the ground G. In addition, the arrangement | positioning of the pile 3 is adjusted suitably in the outer periphery vicinity of the improvement object area.

  In the pile type liquefaction countermeasure structure 1 in which the piles 3 are arranged in this way, the unmodified areas formed between the piles 3 extend in the X direction and the Y direction by the piles 3 of the adjacent pile group P. Since it is blocked, the improvement effect is enhanced as compared with a pile-type foundation structure having the same improvement rate in which the piles 3 are arranged by a normal method.

  Next, the plate-like structure 6 with respect to the pile 3 arrange | positioned in this way is demonstrated. As shown in FIG. 11, also in this embodiment, the plate-like structure 6 is integrated by connecting a plurality of precast concrete plates 7 by a connecting mechanism 8 (connecting means) (not shown). The concrete board 7 is not a rectangle, but a hexagon in which a pair of diagonals of a rectangle are cut off with a straight line. Even if it is arrangement | positioning of such a pile 3, the plate-shaped structure which fixes the head 3a of all the piles 3 by arrange | positioning several precast concrete boards 7 of the same dimension and the same shape sequentially in the same direction. 6 can be configured.

  Furthermore, as shown in FIG. 12, when the pile group P is arranged in either one of the X direction and the Y direction (here, the X direction), it is shifted by 0.5 columns to either one (here, the Y direction). In this case, by alternately setting a distance of d × 0.5 (here d2 × 0.5) and a distance of d × −0.5 (here d2 × −0.5), the pile 3 Even if it is arranged in a random manner, the heads 3a of all the piles 3 are fixed by arranging a plurality of precast concrete plates 7 having the same dimensions and the same shape while alternately changing the directions. The plate-like structure 6 can be configured. In addition, in the case of such arrangement | positioning, the shape of the part which each precast concrete board 7 protrudes can be set arbitrarily.

  This is the end of the description of the specific embodiments. However, the present invention is not limited to these embodiments, and the above-described embodiments can be combined and modified as long as they do not depart from the spirit of the present invention. Is possible.

  For example, in the said embodiment, although the upper end 3b of the pile 3 is matched with the height of the upper surface of the plate-shaped structure 6, if the shear strength of the pile 3 and the plate-shaped structure 6 can be ensured, a pile will be sufficient. 3 is set to a position lower than the upper surface of the plate-like structure 6, and the height dimension surrounded or fixed by the plate-like structure 6 of the pile 3 is made smaller than the thickness t of the plate-like structure 6. May be. In such a case, if concrete is placed on the upper part of the through hole 10 (above the pile 3) and the pile 3 is covered with concrete, the aesthetics can be improved.

  Moreover, in the said embodiment, although the X direction and the Y direction have formed two rows and the total four through-holes 10 in one precast concrete board 7, it is not limited to two rows in both directions. Furthermore, it is not necessary to arrange the through holes 10 so as to be accommodated in one precast concrete plate 7. For example, a semicircular cutout is formed on the side edge of the precast concrete plate 7, and two precast concrete plates 7 are formed. The through hole 10 may be formed in a state where the two are connected. Moreover, in the said embodiment, although the pile 3 is arrange | positioned at the grid | lattice form, if it arrange | positions with a fixed rule, you may arrange | position the pile 3 in zigzag (triangle), a pentagon, and a hexagon, for example. In this case, the planar shape of the precast concrete board 7 is not a rectangle, but may be an appropriate shape such as a triangle, a parallelogram, a pentagon, or a hexagon. Moreover, the connection part 9 can be installed arbitrarily.

  Moreover, in the said embodiment, although the plate-shaped structure 6 is comprised with the precast concrete, you may comprise the plate-like structure 6 with a steel plate, a FRP board, the improvement layer by a shallow layer mixing process, etc. In the case of using a steel plate or an FRP plate, it is preferable to prepare a plurality of plate pieces and connect them to form the plate-like structure 6 as in the case of a concrete plate. On the other hand, when the plate-like structure 6 is constituted by the improvement layer, the integral plate-like structure 6 may be constructed instead of such a construction method. In this case, if the pile 3 is constructed first, it is difficult to construct an improved layer around the head 3a without damaging the pile 3, so that the improved layer is constructed first and penetrates the improved layer. It is better to build the pile 3 later.

  In addition, the specific shape, arrangement, quantity, dimensions, work procedure, and the like of each element can be changed as appropriate without departing from the spirit of the present invention. On the other hand, all the elements and work procedures of the pile type liquefaction countermeasure structure 1 according to the present invention shown in the above embodiment are not necessarily essential, and can be selected as appropriate.

DESCRIPTION OF SYMBOLS 1 Pile type liquefaction countermeasure structure 3 Pile 3a Head 5 Liquefaction layer 6 Plate-like structure 7 Precast concrete board (plate piece)
10 Through-hole 13 Filler G Ground t Thickness of plate-like structure 6 (predetermined height)

Claims (6)

A plurality of piles constructed to be separated from each other on the ground where the liquefied layer exists;
A plate-like structure that is provided so as to surround the heads of the plurality of piles over a predetermined height and fixes the heads of the piles ;
The plurality of stakes have n rows of points having a center distance of d1 in the X direction and a center distance of d2 in the Y direction on a plane in which the X direction and the Y direction intersect with each other. It comprises a plurality of pile groups constituted by a plurality of piles arranged at all of the plurality of points arranged in a row, and pile groups adjacent to each other in the X direction are arranged shifted by d2 × 0.5 in the Y direction, The pile groups adjacent to each other in the Y direction are arranged with a deviation of d1 × 0.5 in the X direction,
The plate-like structure is composed of a plurality of plate pieces having the same size and the same shape in which m × n holes are formed in advance corresponding to the positions of the piles of each pile group. A pile type liquefaction countermeasure structure. The pile type liquefaction according to claim 1 , wherein a head of each pile is fixed to the plate structure by a filler filled between the plate structure and the pile. Countermeasure structure. The plurality of piles are deep mixed piles formed using at least a high-pressure injection method,
By formed a pile head a solidifying material injection to so as to reach the inner surface of the hole of the plate-like structure, characterized in that each pile is fixed to the plate-like structure, to claim 1 The pile type liquefaction countermeasure structure described. Installing a plate-like structure having a plurality of holes spaced from each other on the ground on which the liquefied layer exists;
Carrying heavy machinery onto the plate-like structure, and using the heavy machinery to construct a plurality of piles that are separated from each other in the ground at the position of the hole ;
And securing to the plate-like structure of the head of the pile over a predetermined height seen including,
In the step of constructing the plurality of piles, on the plane in which the X direction and the Y direction intersecting each other are set, m rows of points having a center-to-center distance in the X direction are the centers of d2 in the Y direction. It has a plurality of pile groups composed of a plurality of piles arranged at all of a plurality of points arranged in n rows with a distance between them, and the pile groups adjacent to each other in the X direction are shifted by d2 × 0.5 in the Y direction The plurality of piles are constructed such that pile groups adjacent to each other in the Y direction are arranged with a deviation of d1 × 0.5 in the X direction,
In the step of installing the plate-like structure, a plurality of plate pieces having the same size and the same shape in which m × n holes are formed in advance corresponding to the position of the pile of each pile group are laid out. And the construction method of the pile-type liquefaction countermeasure structure characterized by installing the said plate-shaped structure by connecting mutually adjacent board pieces . The pile according to claim 4 , wherein in the step of fixing the head of each pile to the plate-like structure, a filler is filled between a hole of the plate-like structure and the pile. Method of constructing a formula liquefaction countermeasure structure. In the step of constructing the plurality of piles, a deep mixed pile is constructed using at least a high-pressure injection method,
In the step of fixing the heads of the respective piles to the plate-like structures, the piles are formed by injecting solidifying material so as to reach the inner surfaces of the holes of the plate-like structures, thereby forming the pile heads. The method for constructing a pile type liquefaction countermeasure structure according to claim 4 , wherein the pile type liquefaction countermeasure structure is fixed to a shaped structure.

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