JP7195232B2 - Core material for earth retaining wall and removal method of upper core material - Google Patents

Description

The present invention provides a core material for an earth retaining wall composed of a lower core material and an upper core material (especially a core material structure in which the upper core material can be removed after construction), and an upper core material from the earth retaining wall. Regarding removal method.

A core material (H-shaped steel) are placed. Soil mortar is used as a water impermeable wall, and the core material is used as a retaining material (stress member). You can build underground structures. After constructing the underground structure, it will be backfilled.

In this type of earth retaining work, it may be required to remove the core material from the ground surface to a predetermined depth after the completion of backfilling.

In such a case, as shown in Patent Document 1 and the like, a core material made of H-shaped steel for earth retaining walls is provided as a connecting structure between the lower core material and the upper core material, and the lower core material is used when backfilling. It is performed to separate the upper core material from and make it removable.

In particular, in the connection structure between the lower core material and the upper core material described in Patent Document 1, the outer surface of the excavation side flange and the outer surface of the ground side flange are provided in a form that straddles the lower core material and the upper core material. A splicing plate (joining plate) is provided, and a long bolt is passed from the excavation side through the excavation side splicing plate, the excavation side flange, the ground side flange, and the ground side splicing plate, and the long bolt on the ground side The tip is screwed into a nut fixed to the splicing plate on the rock side and tightened.

In such a connection structure, when backfilling (more specifically, at the time when the lower core material and the upper core material are backfilled to the vicinity of the connection position), the heads of the long bolts are rotated from the excavation side to connect with the nuts. By pulling out the long bolt after releasing the screwing, the connection between the lower core member and the upper core member can be released. This allows the upper core material to be pulled out of the soil mortar.

Japanese Patent No. 3404315

However, the structure described in Patent Document 1 has the following problems.
During backfilling, that is, when earth pressure and water pressure are acting from the outside, the connection between the lower core material and the upper core material is released, so the bending moment cannot be resisted and the core material is damaged. there is a risk of

If the separation depth is as shallow as 1-2m, the earth pressure and water pressure are small, and the core material may be stable even if the long bolt is pulled out, but if the separation depth is as deep as 5-6m or 7-8m , Earth pressure, and water pressure are large, and there is concern that the upper core material may become unstable after the long bolt is pulled out (after disconnection).

In view of such circumstances, the present invention provides a core for earth retaining wall that allows the upper core material to be safely removed after backfilling, not during backfilling, and even at a considerable cut-off depth. An object of the present invention is to provide a material and a method for removing the upper core material.

A core material (structure) for an earth retaining wall according to the present invention includes: a lower core material; a splicing plate disposed so as to straddle the splicing plate and the upper core member; first fixing means for fixing the lower portion of the splicing plate and the lower core member; and the upper portion of the splicing plate. and second fixing means for fixing the upper core member.
Here, the second fixing means is a bolt that penetrates through the joint surface of the upper core member and the splice plate and tightens them, and the bolt connects the upper core member and the splice plate. It is characterized by having a cross-sectional defect at the position of the joint surface.

A method for removing an upper core material according to the present invention is a method for removing the upper core material from the core material having the structure built into the soil mortar retaining wall while leaving the lower core material,
a step of applying a downward impact to the upper end portion of the upper core member to break the bolt having the cross-sectional defect, thereby releasing the fixation between the upper core member and the splice plate;
a step of removing the upper core material by pulling it upward after releasing the fixation;
characterized by comprising

According to the present invention, the upper core material can be removed only by hitting the upper part of the upper core material and pulling it out, so that the upper core material can be safely removed after the backfilling, not during the backfilling.
Also, since the bolts fixing the upper core member and the splicing plate are broken and the splicing plate is left in place, it is sufficient to simply pull out the upper core member alone. can also respond.

Diagram showing an example of construction using earth retaining wall Front view and side view of the connection part (X part in FIG. 1) of the core material in the first embodiment Illustration of bolt with slit Diagram showing how a bolt breaks (shear failure) Diagram showing how bolts break one after another Process diagram showing how to remove the upper core material after construction The front view and side view of the connection part (X part of FIG. 1) of the core material in 2nd Embodiment. Enlarged view of Y section of FIG. 7 and its right side view Diagram showing tensile failure of a bolt Front view and side view of the connection part (X part in FIG. 1) of the core material in the third embodiment Enlarged view of part Z in FIG. 10 and its right side view

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a diagram showing an example of construction using an earth retaining wall.

When constructing and constructing an underground structure (buried frame) under the ground 1, prior to this, the depth reaching the underground impermeable layer 2 for the purpose of retaining the construction site (and stopping water) A retaining wall 3 is constructed so as to partition the excavation side (planned excavation area) and the ground side (non-excavation area).

When the SMW construction method is used as a method for constructing the earth retaining wall 3, holes (drilling grooves) are made in the ground with a multi-shaft kneading auger in a beaded shape in a plan view, and cement milk is discharged from the tip as a solidification material, A wall body 4 made of soil mortar is formed by mixing and stirring with excavated soil, and this is repeated to form a continuous wall of columnar type in the ground.

In addition, when using the TRD construction method, a chainsaw type cutter post built in the ground is moved laterally to excavate the groove while injecting cement milk and mixing and stirring with the excavated soil to create soil. A wall 4 made of mortar (in this case, a continuous wall of equal thickness) is constructed.

In the earth retaining wall 3, inside the wall body 4 made of soil mortar by the SMW construction method or the TRD construction method, core materials (pile) 5 are arranged at predetermined intervals in the continuous direction of the wall body 4 before the soil mortar is hardened. is erected.
Therefore, the earth retaining wall 3 includes a wall body 4 made of soil mortar and a plurality of core members 5 arranged therein.

The core 5 is basically made of H-section steel, and therefore has a pair of front and rear flanges parallel to each other and a web connecting the central portions of both flanges. I-type steel is similar to H-type steel. It only has relatively short flanges compared to H-beams. Therefore, even if it is called "I-shaped steel", if it has a pair of front and rear flanges that are parallel to each other and a web that connects the central parts of both flanges, it is defined in this specification as Included in "H-shaped steel".

A core member 5 made of H-shaped steel is installed in the earth retaining wall 3 so that a pair of front and rear flanges of the core material 5 face each other in the width direction of the earth retaining wall 3 . Therefore, for two core members 5 adjacent to each other in the continuous direction of the earth retaining wall 3, the webs thereof face each other in the continuous direction of the earth retaining wall 3.

Here, the wall body 4 made of soil mortar is formed to a depth reaching the underground impermeable layer 2 so as to function as an impermeable wall, while the core material 5 is formed to the planned excavation depth (floor Below the surface 6), the depth of set-up is determined so as to perform the required function as a stress member.

After the construction of the earth retaining wall 3, the inside of the earth retaining wall 3 (the scheduled excavation area) is excavated, and the wale 7 and the strut 8 are installed each time the predetermined depth is excavated, and these are repeated to excavate. Excavate to the planned depth (floor surface) 6 (state shown in FIG. 1).
After that, an underground structure (not shown) is built on the floor surface 6, and the top is backfilled to complete construction.

In construction using such a retaining wall 3, after construction, the upper part of the core material 5 installed in the retaining wall 3, specifically, in preparation for future road construction and various burying works on the ground surface side. Practically, there are cases where it is required to remove a range up to a predetermined depth (for example, 8m) from the ground surface side.

In such a case, according to the present invention, the core material 5 is preconfigured to have a connecting structure between the lower core material 11 and the upper core material 12, and the upper core material 12 can be removed while leaving the lower core material 11 after construction. do.
The structure of the core material 5 will be described below.

The core material 5 is divided into a lower core material (lower H-shaped steel) 11 and an upper core material (upper H-shaped steel) 12, and the lower core material 11 and the upper core material 12 are spliced together. It has a structure to be connected using a plate 13 . More specifically, the upper end portion of the lower core member 11 and the lower end portion of the upper core member 12 are connected to each other using the splicing plate 13 while facing each other with a gap therebetween.

Here, the length of the upper core member 12 (the connection position between the lower core member 11 and the upper core member 12) is set based on the depth to which removal of the core member 5 is required.

Next, the lower core member 11, the upper core member 12, and their connection structure (splice plate 13, etc.) will be described in detail with reference to FIG.

FIGS. 2A and 2B show the structure of the connecting portion (X portion in FIG. 1) of the core material in the first embodiment, FIG. 2A being a front view and FIG. 2B being a side view. FIG. 2C is a side view showing the bolt insertion holes of the upper core member and the lower core member with the splicing plate removed.

The lower core member 11 is H-shaped steel, and is composed of a pair of left and right flanges 11a, 11a parallel to each other, and a web 11b connecting the central portions of both flanges 11a, 11a.
The upper core member 12 is an H-shaped steel having the same cross-sectional shape as the lower core member 11, and is composed of a pair of left and right parallel flanges 12a, 12a and a web 12b connecting the central portions of both flanges 12a, 12a. .

Here, the lower core material 11 and the upper core material 12 are opposed to each other with a gap C of about 50 mm between the upper end of the lower core material 11 and the lower end of the upper core material 12. .

The connection means between the lower core material 11 and the upper core material 12 is composed of at least two splice plates 13 arranged so as to straddle the lower core material 11 and the upper core material 12, and the splice plates 13 first fixing means (15, 16) for fixing the lower part of the splice plate 13 and the lower core material 11; and second fixing means (17, 18) for fixing the upper part of the splicing plate 13 and the upper core material 12; Consists of

The splicing plate 13 is applied to the outer surfaces of the flanges 11 a and 12 a so as to straddle the lower core member 11 and the upper core member 12 .
Although the splicing plate 13 is shown as a flat plate in the drawing, it may have appropriate reinforcing ribs or the like for improving strength.

The first fixing means comprises a bolt 15 and a nut 16 for fixing the lower part of the splicing plate 13 and the upper part of the lower core member 11 (flange 11a).
However, since it is not necessary to separate the lower core member 11 and the splice plate 13, the first fixing means may be of any type and may be fixed by welding.

The second fixing means comprises bolts 17 and nuts 18 for fixing the upper portion of the splicing plate 13 and the lower portion of the upper core member 12 (flange 12a).
The bolt 17 penetrates the splice plate 13 and the upper core member 12 (flange 12a), and tightens them between the head of the bolt 17 and the nut 18. A bolt insertion hole is formed in the member 12 (flange 12a).

Here, as for the second fixing means, the upper core member 12 and the splice plate 13 can be separated from the upper core member 12 and the splice plate 13 as the bolts 17 instead of ordinary bolts. Use a bolt with a cross-sectional defect at the position of the joint surface, specifically a bolt with a slit.

As shown in FIG. 3, the slitted bolt 17 has a slit (annular groove) 17s at an appropriate position of the shaft portion of the bolt 17 (the position of the joint surface between the upper core member 12 and the splice plate 13). The slit 17s has a depth of 2.5 mm, for example, in the case of an M22 bolt. In this case, the diameter of the slit 17s is 17 mm, and the remaining cross-sectional area is about 60% of the cross-sectional area of the bolt shaft.

According to experiments, the tensile strength of a bolt with a cross-sectional defect does not decrease until about 60% of the remaining cross-sectional area, but the shear strength is proportional to the cross-sectional area and becomes about 60%.

Therefore, by applying a downward impact force (impact load) to the upper portion of the upper core member 12, the upper core member 12 moves relative to the splice plate 13 as shown in FIG. Then, the slitted bolt 17 can be broken (shear breakage), whereby the upper core member 12 can be pulled out.

However, there are a large number of bolts 17, for example, 3×2=6 bolts on one splice plate 13, totaling 12 bolts, and it is difficult to break all of them at the same time.

Therefore, in the present embodiment, at least in the vertical rows, the bolts 17 are devised so that they can be destroyed one by one or by a small number of bolts with a time lag.

In FIG. 2(C), the bolt insertion holes 19a to 19f provided in the upper core member 12 are elongated in the vertical direction, and the length of each elongated hole, particularly the position of the upper edge, is adjusted to, for example, It is changed by 10mm. However, 19a may be a round hole.

As a result, when a downward impact force is applied to the upper portion of the upper core member 12 to move the upper core member 12 relative to the splice plate 13, the bolt insertion holes 19a→19b→19c shown in FIG. →19d→19e→19f, the corresponding bolts 17 can be shear fractured one after another.

FIG. 5 shows this state, and it can be seen that the upper bolt 17 is sheared in FIG. 5(A)→(B), and the lower bolt 17 is sheared in FIG. 5(B)→(C). .

FIG. 6 shows a method of removing the upper core material after construction.
From the state of FIG. 6(A), as shown in FIG. 6(B), an impact (impact load) is applied downward from the upper end of the upper core member 12 . The impact can be applied using a press fitting machine or the like. As a result, the slitted bolt 17 fixing the lower end portion of the upper core member 12 and the upper portion of the splice plate 13 is sheared, and the fixation of the upper core member 12 and the splice plate 13 is released.

Next, as shown in FIG. 6C, the upper core member 12 is pulled upward and removed. Extraction can be performed using an extraction machine (reversing the press fitting machine), a jack, wire traction, or the like. The lower core member 11 and splice plate 13 are left.

After the backfilling is completely completed, the connection is released by hitting and the upper core material is pulled out, and the work is easy and safe. Naturally, the work can be carried out more efficiently than the conventional method.
In addition, since the bolts can be broken one by one or in small numbers (by group) in order, the connection mechanism can be broken without requiring a large impact load.

In addition, since the impact load is sufficiently transmitted to a depth of 5 to 8 m, it is easy to separate and remove the upper core material at a deep depth.
In addition, since only the upper core member 12, that is, only the H-shaped steel having the same cross-sectional shape from top to bottom can be pulled up, leaving the lower core member 11 and the splice plate 13, the pull-out resistance can be kept extremely low. can.

Next, a second embodiment will be described.
FIGS. 7A and 7B show the structure of the connecting portion (X portion in FIG. 1) of the core material in the second embodiment, FIG. 7A being a front view and FIG. 7B being a side view. FIG. 7C is a side view showing the bolt insertion holes of the upper core member and the lower core member with the splicing plate removed.
8(A) is an enlarged view of the Y portion of FIG. 7(A), and FIG. 8(B) is a right side view of FIG. 8(A).

In this embodiment, the bolt insertion holes 19a to 19f in the upper core member 12 are all elongated holes elongated in the vertical direction.
Then, when the upper core member 12 moves to the lower core member 11 side, the bolt 17 head is integrated with the mounting surface (the flange inner surface in this example) of the upper core member 12 for the bolt 17 head. A wedge member 20 (20a to 20f) is provided to enter under the seating surface of the seat.

Each pair of wedge members 20a to 20f are provided along both sides of the bolt insertion holes (long holes) 19a to 19f.

A plurality of wedge members 20a to 20f are also provided corresponding to the plurality of bolts 17a to 17f, and the distances between the bolts 17a to 17f and the corresponding wedge members 20a to 20f are different for each bolt. .

Therefore, in the case of this embodiment, when a downward impact force is applied to the upper portion of the upper core member 12 to move the upper core member 12 relative to the splice plate 13, first, FIG. As shown in B), the wedge member 20a enters under the seating surface of the head of the bolt 17a. Thereby, a tensile force acts on the bolt 17a with the slit, and the bolt 17a can be broken (tensile fracture).
After that, the corresponding bolts 17b, 17c, 17d, 17e and 17f can be tensile fractured one after another in the order of the wedge members 20b, 20c, 20d, 20e and 20f of FIG.

The maximum height of each wedge member 20a-20f is about 10 mm. This is because a bolt with a width of about 40 mm between the two steel plates (separation between the bolt and nut) breaks at about 5 mm of elongation.

Next, a third embodiment will be described.
10A and 10B show the structure of the connecting portion (X portion in FIG. 1) of the core material in the third embodiment, FIG. 10A being a front view and FIG. 10B being a side view. FIG. 10C is a side view showing the bolt insertion holes (slots) of the upper core member and the lower core member with the splicing plate removed.
11(A) is an enlarged view of the Z portion of FIG. 10(A), and FIG. 11(B) is a right side view of FIG. 10(A).

In this embodiment, the wedge members 20a, 20c, and 20e are integrated with different heights. Similarly, the wedge members 20b, 20d, and 20f are integrated with different heights. Correspondingly, the lengths of the bolts 17a-17f are changed. The action is the same. The wedge members 20a, 20c, 20e and the wedge members 20b, 20d, 20f may be independent or continuous.

In this embodiment, instead of the bolt insertion holes (long holes) 19a to 19f in the first and second embodiments, bolt insertion holes (slots) 21a and 21b are provided.

The bolt insertion hole 21a is an elongated hole formed by connecting the bolt insertion holes 19a, 19c, and 19e in a row, and is a slot hole whose one end (lower end) reaches the lower end of the upper core member 12 and opens. It's becoming
The bolt insertion hole 21b is an elongated hole formed by connecting the bolt insertion holes 19b, 19d, and 19e in a row, and is a groove hole whose one end (lower end) reaches the lower end of the upper core member 12 and opens. It's becoming

With such a slot system, the upper core member 12 can be pulled out simply by loosening the bolts 17a to 17f by the tensile action without breaking the bolts 17a to 17f by the wedge members 20a to 20f.

It should be noted that the illustrated embodiment is only a schematic illustration of the present invention, and that the present invention, in addition to what is directly indicated by the described embodiment, can also be made by those skilled in the art within the scope of the claims. Needless to say, it includes the improvement and change of

1 ground 2 impermeable layer 3 earth retaining wall 4 wall made of soil mortar 5 core material (H-shaped steel)
6 floor surface 7 wale 8 strut 11 lower core 12 upper core 13 splicing plate 15 bolt 16 nut 17 (17a to 17f) bolt with slit 17s slit 18 nut 19a to 19f bolt insertion hole 20 (20a ~20f) Wedge members 21a, 21b Bolt insertion holes (slots)

Claims (6)

A core material built into a soil mortar retaining wall,
a lower core material;
an upper core material in which the upper end of the lower core material is opposed to the lower end with a gap;
a splicing plate disposed so as to straddle the lower core material and the upper core material;
a first fixing means for fixing the lower part of the splicing plate and the lower core material;
a second fixing means for fixing an upper portion of the splicing plate and the upper core member;
including
The second fixing means is a bolt that penetrates through the joint surfaces of the upper core member and the splice plate and tightens them. A core material for an earth retaining wall, characterized by having a cross-sectional defect at a position. A plurality of the bolts are provided at least in the vertical direction,
The plurality of bolt insertion holes provided in the upper core member corresponding to the plurality of bolts are long holes elongated in the vertical direction,
2. A core material for an earth retaining wall according to claim 1, wherein the distance between each bolt and the upper edge of each corresponding elongated hole is different for each bolt. The bolt insertion hole in the upper core member is an elongated hole elongated in the vertical direction,
A wedge member that is integrated with the mounting surface of the bolt head of the upper core member and that enters under the bearing surface of the bolt head when the upper core member moves toward the lower core member. A core material for a retaining wall according to claim 1, further comprising: A plurality of the bolts are provided at least in the vertical direction,
A plurality of the wedge members are also provided corresponding to the plurality of bolts,
4. The core material for an earth retaining wall according to claim 3, wherein the distance between each bolt and each corresponding wedge member is different for each bolt. 5. A core material for an earth retaining wall according to claim 3, wherein said elongated hole is a slotted hole whose one end reaches the lower end of said upper core material and opens. A method for removing the upper core material from the core material according to any one of claims 1 to 5 built into a soil mortar retaining wall while leaving the lower core material,
a step of applying a downward impact to the upper end portion of the upper core member to break the bolt having the cross-sectional defect, thereby releasing the fixation between the upper core member and the splice plate;
a step of removing the upper core material by pulling it upward after releasing the fixation;
A method for removing an upper core material, comprising:

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