JP7820907B2 - Earth retaining wall construction method and soil cement diaphragm wall - Google Patents

Description

The present invention relates to a method for constructing an earth retaining wall and a soil cement continuous wall.

When constructing the foundation or underground portion of a building, an earth retaining wall may be constructed on the ground surrounding the building. For such earth retaining walls, a soil cement continuous wall (SMW method) in which in-situ soil is mixed with a cement-based solidification material to produce soil cement is widely used (see, for example, Patent Document 1).
In soil cement diaphragm walls, core material is generally installed over almost the entire height. However, unnecessary portions of the retaining wall may be removed if they interfere with the construction of the structure or with exterior construction or piping work after the structure is constructed.
When removing a soil-cement diaphragm wall, the soil cement adhering to the core material must be removed and then the core material must be cut, which is a time-consuming process. Furthermore, the removed soil-cement fragments and core material must be disposed of as industrial waste, which increases costs and hinders efforts to reduce environmental impact.
Therefore, Patent Document 2 discloses a construction method in which a retaining wall is constructed with a steel cylinder having an inner diameter larger than the outer diameter of the core material placed on top of the core material to be left in place, and after constructing a structure inside the retaining wall, the steel cylinder is pulled out, thereby removing the upper part of the retaining wall.
Furthermore, Patent Document 3 discloses a construction method in which a core material is placed in a borehole together with pliers to form a retaining wall, and the pliers are then removed after excavating the inside of the retaining wall.
In the construction methods of Patent Documents 2 and 3, steel cylinders or pliers are erected into the excavated hole along with the core material to form a retaining wall, which requires the same number of steel cylinders or pliers as the core material, which hinders cost reduction.

Japanese Patent Application Publication No. 9-151450 JP 2013-227737 A Japanese Utility Model Application Publication No. 8-416

The objective of the present invention is to propose a method for constructing an earth retaining wall and a soil cement diaphragm wall that allows for the simple and inexpensive creation of a soil cement diaphragm wall in which core materials are erected only in necessary locations.

The method for constructing an earth retaining wall according to the present invention for solving the above-mentioned problems includes a drilling step of drilling a hole from the ground surface inside an existing basement wall to form a borehole, and a core material installation step of installing a core material into the borehole. In the drilling step, in-situ soil and cement slurry are mixed in the borehole to produce soil cement. In the core material installation step, the core material is inserted from the bottom of the existing basement wall to a position deeper than the bottom of the existing basement wall using pliers that hold the upper end of the core material. The core material is then suspended from a platform installed above ground . Finally, the pliers are removed while the core material is suspended. This results in an earth retaining wall formed along the inside of the existing basement wall at a position deeper from the ground surface than the bottom of the existing basement wall and deeper than the bottom of the new building. The core material of the soil cement continuous wall is located in the middle of the soil cement continuous wall, and the core material is not located at the bottom or top of the soil cement continuous wall.
In this earth retaining wall construction method, pliers are used to place the core material in a predetermined position. Furthermore, by removing the pliers, a soil cement continuous wall can be constructed without a core material on top. This reduces the effort and cost required to remove the core material. Furthermore, because the pliers are removed while the core material is suspended on a platform installed above ground, the pliers can be removed before the cement slurry hardens. In other words, the pliers can be quickly diverted to the construction of other core materials, thereby reducing costs.
The method may further include a curing step of curing the core material while suspended by the hangers held by the frame, and then removing the hangers once the soil cement has developed a predetermined strength. In this way, a soil cement continuous wall can be constructed with the core material disposed at a predetermined depth. Furthermore, because the hangers are removed, they do not interfere with subsequent construction.
Furthermore, if the core material and the pliers are connected via a joint pin connected to a hydraulic unit, the hydraulic unit can be operated during the extraction work to release the connection by the joint pin before the pliers can be extracted. In this way, the core material and the pliers can be released from the soil cement in a simple mechanism.

The soil cement diaphragm wall of the present invention is constructed along an existing basement wall, such as an earth retaining wall or the exterior wall of an existing structure, on the ground inside the existing basement wall, and the upper end of the core material of the soil cement diaphragm wall is located at a depth below the lower part of the existing basement wall. The lower end of the core material is disposed deeper than the lower end of the existing basement wall and deeper than the bottom surface of the new building, and the soil cement diaphragm wall is formed along the inside of the existing basement wall, from the ground surface to a position deeper than the lower end of the existing basement wall and deeper than the bottom surface of the new building . The core material of the soil cement diaphragm wall is disposed in the middle of the soil cement diaphragm wall, and no core material is disposed at the lower or upper end of the soil cement diaphragm wall.
With such a soil cement diaphragm wall, the core material of the soil cement diaphragm wall is placed deeper than the bottom of the existing basement wall, so when constructing a structure inside the existing basement wall or when connecting pipes to the structure, the core material of the soil cement diaphragm wall is unlikely to interfere with work. Also, because the soil cement diaphragm wall is formed deeper than the existing basement wall, a new structure can be constructed deeper underground than the existing basement wall.

The earth retaining wall construction method and soil cement diaphragm wall of the present invention make it possible to easily and inexpensively form a soil cement diaphragm wall in which core materials are erected only in necessary locations.

FIG. 2 is a cross-sectional view of an earth retaining wall according to the present embodiment. 1 is a flowchart of a method for constructing an earth retaining wall according to the present embodiment. 1A and 1B are cross-sectional views showing the construction status of the earth retaining wall construction method, in which (a) is the drilling process, (b) is the insertion work in the core material installation process, and (c) is the extraction work in the core material installation process. 1A and 1B are diagrams showing pliers, in which (a) is a front view and (b) is a plan view seen from the bottom. 1A to 1C are diagrams showing the joint between the core material and the pliers, where (a) is a front view, (b) is a side view, and (c) is a cross-sectional view. 10A and 10B are front views showing the construction status of the replacement work, in which FIG. 10A shows the state before the replacement and FIG. A plan view showing the excavation holes of this construction cycle and the excavation holes of the next construction cycle.

This embodiment describes the construction of a new building S, which has a deeper underground section than the existing building (existing basement wall 1), on the site where the existing building has been demolished, by utilizing a portion of the basement wall (existing basement wall 1) of the existing building. The new building S is constructed by constructing an earth retaining wall 2 along the inside of the existing basement wall 1, and then forming the inner portion of the earth retaining wall 2 in the excavated area. The earth retaining wall 2 is a soil cement continuous wall constructed along the existing basement wall 1. Figure 1 shows the earth retaining wall 2. As shown in Figure 1, the earth retaining wall 2 is formed from the ground surface to a position deeper than the bottom end of the existing basement wall 1, and a core material 3 made of H-shaped steel is disposed only in the range from the bottom of the existing basement wall 1 to a position deeper than the bottom end 11 of the existing basement wall 1 and deeper than the bottom surface Sb of the new building S. Furthermore, the earth retaining wall 2 of this embodiment also has a section at the bottom (for example, within approximately 3 m from the bottom end) where the core material 3 is not disposed.

Next, the earth retaining wall construction method of this embodiment will be described. A flowchart of the earth retaining wall construction method of this embodiment is shown in Figure 2. As shown in Figure 2, the earth retaining wall construction method of this embodiment includes a hole drilling step S1, a core material installation step S2, and a curing step S3.
In the drilling step S1, the ground is drilled to form a borehole 4. FIG. 3( a) shows the construction status of the drilling step S1. As shown in FIG. 3( a), the borehole 4 is drilled along the inner surface of the existing basement wall 1 so that the hole bottom 41 reaches a position deeper than the lower end of the existing basement wall 1. In this embodiment, the drilling is performed using a multi-shaft auger 5 equipped with three agitation shafts 51 (only one is shown in the drawing) arranged side by side. In the drilling step S1, as the borehole 4 is excavated, cement slurry discharged from the agitation shafts 51 is mixed with the in-situ soil in the borehole 4 to produce soil cement 6. Note that the residual soil discharged from the borehole 4 following the injection of the cement slurry (drilling of the borehole 4) is transported away.

In the core material erection process S2, the core material 3 is erected in the excavation hole 4. As shown in Figure 2, in the core material erection process S2, the core material 3 is erected at a predetermined position (depth position) by performing an insertion operation S21, a replacement operation S22, and a withdrawal operation S23. Figure 3(b) shows an overview of the core material erection process S2.
In the insertion operation S21, as shown in Figure 3(b), the core material 3 is inserted to a predetermined depth using pliers 7 that hold the upper end of the core material 3. First, the core material 3 is inserted into the drilling hole 4. Once the core material 3 has been inserted to a position where only the head of the core material 3 protrudes from the drilling hole 4, the pliers 7 are connected to the head of the core material 3 (see Figure 5). Then, the core material 3 is lowered to the predetermined depth using the pliers 7.
The pliers 7 are inserted into the drill hole 4 while holding the core material 3, and guide the core material 3 to a predetermined depth position within the drill hole.

Figure 4 shows the pliers 7. As shown in Figure 4, the pliers 7 include a main body 71 made of an H-shaped steel; clamping sections 72, 72 made of a pair of steel members (e.g., channel steel) that protrude downward from the lower end of the web of the main body 71 and are attached to the web of the core material 3; and guide members 73 that protrude downward from the lower ends of both flanges of the main body 71 and are attached to the outer surfaces of the flanges of the core material 3. In this embodiment, the main body 71 is made of an H-shaped steel with the same cross section as the H-shaped steel that constitutes the core material 3. In addition, the clamping section 72 in this embodiment is bolted to the main body 71. In addition, the guide members 73 in this embodiment are welded to the flanges of the main body 71. A pin insertion hole 74 is formed in the protruding portion of the clamping section 72 from the main body 71, through which a joint pin used to join the core material 3 is inserted. The portions of the clamping sections 72, 72 that protrude from the lower end of the main body 71 face each other with a gap that allows the web of the core material 3 to be inserted. Additionally, a gap is formed between the clamping portion 72 at the portion protruding from the lower end of the main body portion 71 and the guide member 73, allowing the flange of the core member 3 to be inserted.

Figure 5 shows the joint between the core material 3 and the pliers 7. In this embodiment, an H-beam is used as the core material 3. As shown in Figures 5(a) to 5(c), the core material 3 is connected to the pliers 7 with its web inserted between the clamping portions 72 of the pliers 7 and its flange inserted between the clamping portions 72 and the guide members 73. In other words, by inserting the core material 3 between the clamping portions 72 and between the guide members 73, it is guided so that its axis is aligned or nearly aligned with that of the pliers 7. A pin insertion hole 31 is formed in the web of the core material 3 at a position corresponding to the pin insertion hole 74 of the clamping portion 72. The core material 3 and the pliers 7 are connected via a joint pin 75 that passes through the pin insertion holes 31 and 74. The joint pin 75 is connected to a hydraulic unit 76 that controls the insertion and removal of the joint pin 75 into the pin insertion hole 74.

As shown in Figure 5(a), a suspension member 8 is pre-connected to the core member 3. The suspension member 8 is made of rebar or threaded rebar with a threaded tip, and is connected to the core member 3 by threading it into a long nut 32 fixed to the top of the core member 3. The suspension member 8 is long enough that its upper end protrudes from the drilling hole 4 when the core member 3 is placed in its designated position. When inserting the core member 3 into the drilling hole 4, the suspension member 8 extends along the corner between the flange and web of the pliers 7. As shown in Figure 5(b), the body 71 of the pliers 7 has a recess 77 formed by cutting out a portion of the flange. The recess 77 is a cutout portion that prevents tools or the worker's arm from coming into contact with the flange when the suspension member 8 is rotated and threaded onto the long nut 32. In this embodiment, the suspension member 8 is visible through the recess 77 when the pliers 7 are viewed from the side.

In the transfer operation S22, the core material 3 is suspended by a platform 9 installed on the ground. Figure 6 shows the construction status of the transfer operation S22. As shown in Figure 6(a), the platform 9 is formed in advance on the ground above the borehole 4. The platform 9 is formed by combining steel materials (e.g., H-shaped steel). In the transfer operation S22, as shown in Figure 6(b), the load of the core material 3 is transferred from the pliers 7 to the platform 9 by engaging the suspension material 8 with a support material 91 provided on the platform 9.
Once the core material 3 is secured to the platform 9, drilling (drilling process S1) of the next section (adjacent borehole 4) begins. If the section in question is the final section of the day, drilling of the next section is not carried out. Figure 7 shows the borehole 4 of this section and the borehole 4 of the next section (next cycle). As shown in Figure 7, the boreholes 4 of adjacent sections partially overlap. Note that the receiving material 91 is omitted from Figure 7.

In the pulling-out operation S23, as shown in Figure 3(c), only the pliers 7 are pulled out while the core material 3 is suspended (with the core material 3 engaged with the receiving material 91). The pliers 7 are pulled out after the adjacent borehole 4 has been drilled (see Figure 7). If the construction section in question is the final construction section of the day, the pliers 7 are pulled out of the borehole 4 once the hanging material 8 has been engaged with the platform 9.
In the pulling-out operation S23, the hydraulic unit 76 is operated to release the connection by the joint pin 75 (after releasing the connection between the core material 3 and the pliers 7), and then the lifting machine M is used to lift the pliers 7.

In the curing step S3, the soil cement 6 is cured.
In the curing step S3, as shown in Fig. 6(b), the soil cement 6 is cured while the core material 3 is suspended by engaging the hanger 8 with the receiving material 91. When the soil cement 6 has attained a predetermined strength through curing, the hanger 8 is removed (the hanger 8 is rotated to remove it from the long nut 32 and pulled out of the borehole 4).

After constructing the earth retaining wall 2 within the specified area, the existing basement wall 1 and the interior portion of the earth retaining wall 2 are excavated, and the new building S is constructed (see Figure 1). At this time, in the portion shallower than the core material 3, the beam Sa is attached to the bracket 12 attached to the existing basement wall 1. Furthermore, in the underground portion of the new building S at the depth where the core material 3 is installed, the beam Sa is connected to the bracket 21 attached to the earth retaining wall 2 (fixed to the core material 3).

According to the earth retaining wall construction method of this embodiment, the core material 3 of the earth retaining wall 2 (soil cement continuous wall) is placed deeper than the bottom of the existing basement wall 1, so the core material 3 of the earth retaining wall 2 is less likely to interfere with work when constructing a new building S inside the existing basement wall 1 or when connecting pipes to the new building S. Furthermore, because the earth retaining wall 2 is formed deeper than the existing basement wall 1, the new building can be constructed deeper underground than the existing basement wall 1.
Furthermore, the core material 3 can be placed in a predetermined position (depth and horizontal position) using the pliers 7, and by pulling out the pliers 7, a soil cement continuous wall (earth retaining wall 2) can be constructed with no core material 3 at the top. This reduces the effort and cost required to partially remove the earth retaining wall 2.

Furthermore, since the pliers 7 are connected to the core material 3 via a joint pin 75 connected to the hydraulic unit 76, the connection between the core material 3 and the pliers 7 can be easily released. Therefore, even though it is a simple mechanism, the connection between the core material 3 and the pliers 7 can be released within the soil cement 6, and therefore the pliers 7 can be easily removed.
Since a recess 77 is formed in the pliers 7, the flange of the pliers 7 does not get in the way when installing the hanging material 8 on the core material 3, making it easy to work with.
At the connection between the pliers 7 and the core material 3, the web of the core material 3 is inserted between the clamping portions 72, 72 of the pliers 7, and the flange of the core material 3 is inserted into the clamping portion 72 of the pliers 7 and the guide material 73, so that the core material 3 and the pliers 7 are connected with as little rattle as possible. Therefore, when the core material 3 is inserted into the drilling hole 4, the core material 3 can be positioned with precision.

Furthermore, because the pliers 7 are pulled out while the core material 3 is suspended from the stand 9 installed on the ground via the hanging members 8, the pliers 7 can be pulled out before the cement slurry hardens. In other words, the pliers 7 can be quickly diverted to the erection work of other core materials 3, thereby reducing costs. Furthermore, because the core material 3 is supported by rebar as the hanging members 8, it is possible to prevent the core material 3 from shifting position due to vibrations when or after the pliers 7 are pulled out.
Furthermore, since the hanging material 8 is removed after the soil cement 6 has cured, the hanging material 8 does not get in the way when removing unnecessary parts of the retaining wall 2 during construction of a new building.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-described components can be appropriately modified within the scope of the invention.
In the above embodiment, the core material 3 and the pliers 7 are connected using a joint pin 75, but the method of connecting the core material 3 and the pliers 7 is not limited, and for example, a jig other than the joint pin 75 may be used, or a gripping means may be used.
In addition, in the above embodiment, the case where the joint pin 75 is controlled by the hydraulic unit 76 has been described, but the control means for the joint pin 75 is not limited thereto, and for example, a pneumatic unit, magnetic force, electrical control means, etc. may also be used.
In the above embodiment, the core material 3 of the retaining wall 2 is arranged at a position deeper than the lower part of the existing underground wall, but the depth position at which the core material 3 is arranged is not limited, and it may be, for example, at a position deeper than the middle part of the existing underground wall 1.
In the above embodiment, the case where the new building S is constructed using the existing basement wall 1 has been described, but the existing basement wall 1 does not necessarily have to be used as part of the new building S.

1. Existing basement wall 2. Retaining wall (soil cement continuous wall)
3 Core material 31 Pin insertion hole 32 Long nut 4 Drilling hole 5 Multi-shaft mixing auger machine 51 Stirring shaft 6 Soil cement 7 Pliers 71 Main body 72 Clamping part 73 Guide material 74 Pin insertion hole 75 Joint pin 76 Hydraulic unit 77 Recess 8 Hanging material 9 Stand

Claims (4)

a drilling step of drilling a hole from the ground surface into the ground inside the existing underground wall to form a borehole;
A core material erection process for erecting a core material into the excavation hole,
In the drilling step, in-situ soil and cement slurry are mixed in the drilled hole to produce soil cement,
The core material installation process involves inserting the core material from the bottom of the existing basement wall to a position deeper than the bottom end of the existing basement wall and deeper than the bottom surface of the new building using pliers that hold the upper end of the core material; replacing the core material by suspending it on a platform installed on the ground; and pulling out the pliers while the core material is suspended .
A retaining wall is formed along the inside of the existing basement wall from the ground surface to a position deeper than the lower end of the existing basement wall and deeper than the bottom surface of the new building,
A method for constructing an earth retaining wall, characterized in that the core material of the earth retaining wall is arranged in the middle part of the earth retaining wall, and the core material is not arranged at the lower end and upper end of the earth retaining wall. The method further includes a curing step of curing the soil cement,
2. The earth retaining wall construction method according to claim 1, wherein in the curing step, the core material is cured in a suspended state by hanging materials held by the frame, and then the hanging materials are removed when the soil cement has developed a predetermined strength. The core material and the pliers are connected via a joint pin connected to a hydraulic unit,
3. The method for constructing an earth retaining wall according to claim 1 or claim 2, characterized in that, in the pulling-out operation, the hydraulic unit is operated to release the connection by the joint pin, and then the pliers are pulled out. A soil cement continuous wall constructed along the existing underground wall on the ground inside the existing underground wall,
The upper end of the core material of the soil cement continuous wall is located at a depth position below the lower part of the existing underground wall,
The lower end of the core material is disposed at a position deeper than the lower end of the existing basement wall and deeper than the bottom surface of the new building ,
The soil cement continuous wall is formed along the inside of the existing basement wall from the ground surface to a position deeper than the lower end of the existing basement wall and deeper than the bottom surface of the new building,
A soil cement continuous wall characterized in that the core material of the soil cement continuous wall is arranged in the middle part of the soil cement continuous wall, and the core material is not arranged at the lower end and upper end of the soil cement continuous wall.