JP7637043B2 - How to remove earth retaining walls - Google Patents

Description

This disclosure relates to a method for removing an earth retaining wall.

Various methods for removing retaining walls have been known in the past. Patent No. 3940735 describes a retaining method. In this method, sheet piles are driven into the ground. A hardener injection pipe is attached to the sheet pile by an attachment means and a fastener. The hardener injection pipe is attached to the sheet pile in the longitudinal direction. The tip of the hardener injection pipe is formed with an outlet through which the hardener is sprayed.

When the sheet pile is driven into the ground, the hardener injection pipe also penetrates into the ground, making it possible to inject hardener into the ground from the hardener injection pipe. The tip of the hardener injection pipe is equipped with a plug that opens and closes the above-mentioned nozzle, and a biasing means that biases the plug so that it closes the nozzle. When injecting hardener into the ground, the plug is moved against the biasing force of the biasing means by the injection pressure, and the nozzle is opened into the ground, thereby spraying the hardener into the ground.

JP 2016-148137 A describes a method for removing an earth retaining portion. In this method, an earth retaining member, which is a steel sheet pile with a hat-shaped cross section, is excavated around the earth retaining member to form a recess in the ground surface around the earth retaining member, and the recess is filled with liquefied treated soil, and the earth retaining member is pulled out with a crane. When the earth retaining member is pulled out, a gap is formed between the earth retaining member and the ground that communicates with the recess, and the liquefied treated soil flows from the recess into the gap. In this way, the liquefied treated soil flows into the gap formed when the earth retaining member is pulled out, thereby reducing the impact on the surrounding ground, etc.

Patent No. 3940735 JP 2016-148137 A

The above-mentioned retaining construction method requires the installation of hardener injection pipes in advance, which can cause problems in that installation is difficult. In addition, in a method in which a recess formed on the ground surface is filled with liquefied treated soil, and then the retaining member is pulled out and the liquefied treated soil is poured into the gap between the retaining member and the ground, the gap may not be filled sufficiently with liquefied treated soil. Specifically, when the retaining member is pulled out, a gap is first formed between the bottom end of the retaining member and the ground.

However, since the void does not connect to the depression located on the ground surface, the void is not filled with liquefied treated soil. Therefore, with the above-mentioned retaining portion removal method, the void in the ground is not filled sufficiently with liquefied treated soil, and there is a concern that the void will be left behind. In this case, there is a concern that the ground will subside due to the void being left inside. In other words, since the void does not connect to the depression located on the ground surface, the liquefied treated soil is only filled into the void after the retaining member has been completely pulled out. In this case, there is a concern that the surrounding ground will collapse into the void, causing the ground to subside before the liquefied treated soil is filled.

The purpose of this disclosure is to provide a method for removing retaining walls that can be easily installed and can prevent ground subsidence.

The retaining wall removal method according to the present disclosure comprises the steps of: casting the retaining wall into the ground; excavating the ground located on one side of the retaining wall in a plan view; constructing a structure in the space formed by the excavation; filling the space between the retaining wall and the structure with a filler material that hardens over time; and pulling out the retaining wall from the ground before the filler material hardens. After the step of constructing the structure, the method further comprises the steps of installing a formwork between the retaining wall and the structure and backfilling the space between the formwork and the structure. The step of filling the filler further comprises the steps of filling the space between the retaining wall and the formwork after the backfilling step and pulling out the formwork from the ground after the step of filling the filler. The step of installing the formwork includes the step of interposing a camber between the retaining wall and the formwork, and the step of pulling out the formwork includes the step of pulling out the camber from the filler material.

In this method of removing an earth retaining wall, a structure is constructed in a space formed by excavating the ground on one side of the earth retaining wall, and then the earth retaining wall is pulled out from the ground. After the structure is constructed, a filler that hardens over time is filled in, and the earth retaining wall is pulled out before the filler hardens. Since the earth retaining wall is pulled out from the ground before the filler hardens, the filler can be densely filled in the gap left after the earth retaining wall is pulled out as the earth retaining wall is pulled out. By densely filling the gap with the filler, it is possible to prevent the ground around the earth retaining wall from collapsing into the gap. Therefore, it is possible to prevent the ground from subsiding after the earth retaining wall is pulled out. In addition, since it is only necessary to fill the gap between the earth retaining wall and the structure with the filler and pull out the earth retaining wall, work such as attaching a pipe to the earth retaining wall in advance is not required. Therefore, it is easy to install equipment to prevent ground subsidence.

The method for removing the retaining wall may include, after the step of constructing the structure, a step of installing a form between the retaining wall and the structure, and a step of backfilling between the form and the structure. In the step of filling with filler, the filler may be filled between the retaining wall and the form after the backfilling step. The method for removing the retaining wall may further include a step of pulling out the form from the ground after the step of filling with filler. In this case, the form is placed between the retaining wall and the structure, and the filler is filled between the retaining wall and the form. Therefore, the amount of filler can be reduced compared to when filler is filled between the retaining wall and the structure. As a result, the amount of filler used can be reduced, and the cost of the filler can be reduced.

The step of installing the formwork may include a step of interposing a camber between the retaining wall and the formwork. The step of removing the formwork may include a step of removing the camber from the filler. In this case, since the camber is disposed between the retaining wall and the formwork, the formwork can be easily removed.

The camber may be connected to the surface of the formwork facing the retaining wall via a hinge. In the process of pulling out the camber, the camber may be pulled out together with the formwork in a state in which it can rotate via the hinge. In this case, since the camber is connected to the formwork, it can be pulled out together with the formwork. Therefore, the formwork and the camber can be easily pulled out. Furthermore, the camber is connected to the formwork via a hinge so that it can rotate. Therefore, when the formwork is pulled out, it is possible to rotate the camber relative to the formwork, which prevents the camber from getting caught during pulling out and making it difficult to pull out. Therefore, it is even easier to pull out the formwork and the camber.

This disclosure makes installation easy and prevents ground subsidence.

1A is a vertical cross-sectional view showing a site where a retaining wall removal method according to an embodiment is applied, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 2(a) is a vertical cross-sectional view showing the state in which the earth retaining wall and the skeleton are constructed at the construction site of FIG. 1(a), and FIG. 2(b) is a cross-sectional view taken along line B-B of FIG. 2(a). 3A is a vertical cross-sectional view showing a state in which a formwork and a camber are installed at the site of FIG. 2A, and FIG. 3B is a cross-sectional view taken along line CC of FIG. 10A is an enlarged side view of a camber, and FIG. 10B is a side view of a camber according to a modified example. 5A is a vertical cross-sectional view showing a state where backfilling has been performed between the skeleton and the formwork at the construction site of FIG. 4A, and FIG. 5B is a cross-sectional view taken along line D-D of FIG. 5A. 6A is a vertical cross-sectional view showing a state where the filler material has been filled at the site of FIG. 5A, and FIG. 6B is a cross-sectional view taken along line E-E of FIG. FIG. 13 is a side view showing a schematic view of a camber that rotates when the form is pulled out. FIG. 11 is a side view showing a schematic diagram of a camber that rotates when an earth retaining wall is pulled out in a modified example.

Below, an embodiment of the retaining wall removal method according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, the drawings may be partially simplified or exaggerated to facilitate understanding, and the dimensions, ratios, angles, etc. are not limited to those shown in the drawings.

Figure 1(a) is a vertical cross-sectional view showing a site S to which the retaining wall removal method according to this embodiment is applied. Figure 1(b) is a cross-sectional view taken along line A-A in Figure 1(a). As shown in Figures 1(a) and 1(b), the site S has, for example, a structure T, which is an underground structure, constructed thereon. Around the structure T in plan view, a layer K is provided, which is formed by hardening of a filler material 10, which will be described later. The layer K has a flat first surface K1 facing the structure T and a corrugated second surface K2 facing away from the structure T.

For example, the structure T is an underground structure constructed underground and is buried in the ground B. As an example, the structure T includes a subway platform. In this case, the structure T has a space T1 inside the structure T through which a railway passes. However, the structure T does not have to be a subway platform and can include various structures.

The filler 10 is not hardened at the time of filling and has fluidity. The filler 10 hardens over time. For example, the filler 10 is liquefied treated soil. The liquefied treated soil contains cement, soil (construction waste soil as an example), and water. The liquefied treated soil may be soil mixed with water and a solidifying material.

For example, at the site S, a structure T is constructed in an underground space formed by a retaining wall 1 (see FIG. 2) described below, and after the structure T is constructed, backfilling is performed and the retaining wall 1 is pulled out from the ground B. However, simply pulling out the retaining wall 1 will result in a void in the ground B equivalent to the thickness of the retaining wall 1. If a void is left in the ground B, the ground B may collapse into the void, causing subsidence of the ground B, which is undesirable as it may also affect the building X constructed on the ground surface U. Therefore, a construction method is required that prevents voids from being formed in the ground B after the retaining wall 1 is pulled out.

The retaining wall 1 is used when constructing the structure T, and is removed after the structure T is constructed. As an example, the thickness of the retaining wall 1 is 15 mm. For example, the retaining wall 1 is made of leased material, and since its use is costly, it is desirable to remove it from the ground B. Furthermore, if the retaining wall 1 is left on the ground B for a long period of time, there is a possibility that it will hinder the flow of groundwater, and therefore it is desirable to remove the retaining wall 1 from this point of view as well.

The method for removing an earth retaining wall according to this embodiment will be described below. As shown in Figures 2(a) and 2(b), first, an earth retaining wall 1 is cast into ground B (the process of casting an earth retaining wall). The earth retaining wall 1 is composed of, for example, a number of steel sheet piles 1b. The steel sheet piles 1b have a trapezoidal shape in a cross section cut along a plane perpendicular to the longitudinal direction of the steel sheet piles 1b. In this cross section, the steel sheet piles 1b have a bottom 1c and a pair of legs 1d extending obliquely from both ends of the bottom 1c.

At the end of the leg 1d opposite the bottom 1c, a connection portion 1f is provided to which another steel sheet pile 1b is connected. The multiple steel sheet piles 1b are connected to each other by connecting a pair of connection portions 1f to each other. As an example, the connection portion 1f is U-shaped, and the pair of U-shaped connection portions 1f fit together to connect the pair of steel sheet piles 1b. The multiple steel sheet piles 1b are connected to each other so as to form a wave-shaped shape in plan view. In plan view, the retaining wall 1 is formed, for example, to form a rectangular frame shape.

After the retaining wall 1 is cast into the ground B, the ground B located on one side of the retaining wall 1 in plan view is excavated (ground excavation process). As an example, the inside portion of the frame-shaped retaining wall 1 in plan view is excavated. This excavation of the ground B forms a space C below the ground surface U for constructing the structure T. After the space C is formed, formwork is installed and concrete is poured, etc., to construct the structure T (structure construction process).

Then, as shown in Figures 3(a) and 3(b), the formwork 2 is installed between the structure T and the retaining wall 1 (the process of installing the formwork). As an example, the formwork 2 is made of wood. The formwork 2 has a first surface 2b facing the structure T side and a second surface 2c facing the retaining wall 1 side. For example, the coefficient of friction of the first surface 2b is smaller than the coefficient of friction of the second surface 2c. This allows the formwork 2 to be smoothly pulled out of the backfill soil Y, which will be described later.

For example, the support members 3 are interposed between the formwork 2 and the structure T (step of interposing the support members). The support members 3 are provided to prevent the formwork 2 from tipping over towards the structure T. As an example, multiple support members 3 are arranged in a line along the vertical direction. For example, the multiple support members 3 are removed one by one from the support members 3 located below as the backfill soil Y is backfilled.

The camber 5 is interposed between the formwork 2 and the retaining wall 1 (step of interposing the camber). The camber 5 is interposed between the formwork 2 and the retaining wall 1. The camber 5 ensures the spacing W, making it possible to fill the filler 10 with fewer pours when pouring the filler 10. In other words, when the camber 5 is provided, it becomes possible to fill a wide area with the filler 10 at one time. The camber 5 is made of wood, for example. Figure 4 (a) is an enlarged side view of the camber 5.

As shown in FIG. 4(a), the camber 5 has an upper surface 5b facing vertically upward, a lower surface 5c facing vertically downward, a first side surface 5d facing the formwork 2, and a second side surface 5f facing the retaining wall 1. The camber 5 is rotatably supported on the formwork 2, for example, via a hinge 6. As an example, the hinge 6 is fixed between the first side surface 5d and the lower surface 5c (the lower end of the first side surface 5d) and to the formwork 2, and the camber 5 is rotatable around the hinge 6.

For example, the vertical length of the second side surface 5f is shorter than the vertical length of the first side surface 5d. As an example, the camber 5 has an inclined surface 5g located between the top surface 5b and the second side surface 5f. The inclined surface 5g is formed between the top surface 5b and the second side surface 5f, and the vertical length of the second side surface 5f is shorter than the length of the first side surface 5d, making it easier to pull up the formwork 2 relative to the retaining wall 1.

The above describes an exemplary camber 5. However, the camber between the formwork 2 and the retaining wall 1 may have a configuration other than the camber 5, and may be, for example, the camber 5A shown in FIG. 4(b). The camber 5A has a columnar portion 5h that abuts against the formwork 2 and an inclined portion 5j that abuts against the retaining wall 1. For example, the inclined portion 5j is in the shape of a truncated cone.

As shown in Figures 3(a) and 3(b), the camber 5 is interposed between the formwork 2 and the bottom 1c of the retaining wall 1 that protrudes toward the formwork 2. This forms a gap W between the retaining wall 1 and the formwork 2 that is the length of the camber 5. For example, multiple cambers 5 are arranged in a line along the vertical direction.

Then, backfilling is performed between the formwork 2 and the structure T (backfilling process). At this time, backfill soil Y is filled from below into the space C between the formwork 2 and the structure T. As described above, the support members 3 are removed while the backfill soil Y is being filled. As shown in Figures 5(a) and 5(b), for example, backfilling with backfill soil Y is performed until the backfill soil Y reaches the ground surface U. Even in this state, the space C formed between the retaining wall 1 and the formwork 2 is maintained by the multiple cambers 5.

Then, as shown in Figures 6(a) and 6(b), filler 10 is filled into space C between retaining wall 1 and formwork 2. At this point, filler 10 has not hardened and is fluid. At this time, filler 10 is filled between multiple steel sheet piles 1b and formwork 2, and camber 5 is filled with filler 10. More specifically, filler 10 is filled between multiple bottoms 1c and multiple legs 1d and second surface 2c of formwork 2. Filler 10 is filled from the bottom surface of space C to a height equal to or higher than the ground surface U.

After filling the space C with the filler 10 as described above and before the filler 10 hardens, the formwork 2 is pulled out from the ground B (formwork pulling out process). As described above, the camber 5 is rotatably attached to the second surface 2c of the formwork 2 via the hinge 6, so that the camber 5 is pulled out from the filler 10 together with the formwork 2 as shown in FIG. 7 (camber pulling out process). At this time, the camber 5 is pulled out from the filler 10 together with the formwork 2 while rotating diagonally downward around the hinge 6 located at the lower end of the first side surface 5d.

Then, the retaining wall 1 is pulled out from the ground B before the filling material 10 hardens (the process of pulling out the retaining wall). The retaining wall 1 is pulled out, for example, by a hydraulic press-in and pull-out machine that grasps the retaining wall 1 and pulls it up from the ground B. The formwork 2 described above may also be pulled out by this hydraulic press-in and pull-out machine. For example, the formwork 2 is pulled out before the retaining wall 1 is pulled out. However, the formwork 2 may be pulled out after the retaining wall 1 is pulled out, and the order of the process of pulling out the formwork and the process of pulling out the retaining wall can be changed as appropriate.

When the retaining wall 1 is pulled out, the filler 10 enters sideways into the space in the ground B that is created when the retaining wall 1 is pulled out, and fills the space. As described above, the retaining wall 1 is pulled out and the space is densely filled with the filler 10. After a certain period of time has passed and the filler 10 has hardened, the series of steps is completed as shown in Figures 1(a) and 1(b).

Next, the effects of the retaining wall removal method according to this embodiment will be described. As shown in Figures 3(a), 3(b), 6(a) and 6(b), in the retaining wall removal method according to this embodiment, a structure T is constructed in a space C formed by excavating the ground B located on one side of the retaining wall 1, and then the retaining wall 1 is pulled out from the ground B. After the structure T is constructed, a filler 10 that hardens over time is filled in, and the retaining wall 1 is pulled out before the filler 10 hardens. Since the retaining wall 1 is pulled out from the ground B before the filler 10 hardens, the filler 10 can be densely filled into the gaps in the retaining wall 1 as the retaining wall 1 is pulled out.

By densely filling the ground B with the filler material 10, it is possible to prevent voids from being left in the ground B. Therefore, it is possible to prevent the ground B from subsiding after the retaining wall 1 is pulled out. In addition, since it is only necessary to fill the space between the retaining wall 1 and the structure T with the filler material 10 and pull out the retaining wall 1, work such as attaching pipes to the retaining wall 1 in advance is not required. Therefore, it is easy to install equipment to prevent the subsidence of the ground B.

The retaining wall removal method according to this embodiment includes, after the step of constructing the structure T, a step of installing a formwork 2 between the retaining wall 1 and the structure T, and a step of backfilling between the formwork 2 and the structure T. In the step of filling with the filler 10, the filler 10 is filled between the retaining wall 1 and the formwork 2 after the backfilling step. The retaining wall removal method according to this embodiment further includes a step of pulling out the formwork 2 from the ground B after the step of filling with the filler 10.

Therefore, the formwork 2 is placed between the retaining wall 1 and the structure T, and the filler material 10 is filled between the retaining wall 1 and the formwork 2. Therefore, the amount of filler material 10 can be reduced compared to when the filler material 10 is filled between the retaining wall 1 and the structure T. As a result, the amount of filler material 10 used can be reduced, and the cost of the filler material 10 can be reduced.

As mentioned above, when the filler 10 is liquefied treated soil, the cost of liquefied treated soil is generally high, which leads to an increase in costs. However, when the formwork 2 is placed as in this embodiment and the filler 10 is filled between the formwork 2 and the retaining wall 1, the amount of filler 10 can be kept to a minimum. Therefore, the cost of the filler 10 can be kept low.

In this embodiment, the process of installing the formwork 2 includes a process of interposing the camber 5 between the retaining wall 1 and the formwork 2, and the process of pulling out the formwork 2 includes a process of pulling out the camber 5 from the filler material 10. Therefore, since the camber 5 is disposed between the retaining wall 1 and the formwork 2, the formwork 2 can be easily pulled out.

In the retaining wall removal method according to this embodiment, as shown in Figures 4(a) and 7, a formwork 2 with a camber 5 is used that abuts against the retaining wall 1 before the retaining wall 1 is pulled out. By attaching the camber 5 to the formwork 2 in this way, the spacing W is ensured, and the filler 10 can be poured in a small number of times.

In this embodiment, the camber 5 is connected to the second surface 2c of the formwork 2 that faces the retaining wall 1 via a hinge 6, and in the process of pulling out the camber 5, the camber 5 is pulled out together with the formwork 2 in a state in which it can rotate via the hinge 6. Therefore, since the camber 5 is connected to the formwork 2, the camber 5 can be pulled out together with the formwork 2.

Therefore, the formwork 2 and the camber 5 can be easily pulled out. Furthermore, the camber 5 is rotatably connected to the formwork 2 via the hinge 6. Therefore, when the formwork 2 is pulled out, the camber 5 can be rotated relative to the formwork 2, which prevents the camber 5 from getting caught and becoming difficult to remove. This makes it even easier to pull out the formwork 2 and the camber 5.

The above describes an embodiment of the retaining wall removal method according to the present disclosure. However, the present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate within the scope of the gist described in the claims. In other words, the content and order of the steps of the retaining wall removal method according to the present disclosure can be modified as appropriate within the scope of the above-mentioned gist.

In the above-mentioned embodiment, an example was described in which the filler 10 was liquefied treated soil. However, the filler may be something other than liquefied treated soil, such as mortar. In the above-mentioned embodiment, an example was described in which the camber 5 was attached to the formwork 2. However, the camber may be attached to the retaining wall.

Figure 8 shows an example in which the camber 15 is attached to the retaining wall 11 via a hinge 16. As shown in Figure 8, the camber 15 has an upper surface 15b facing vertically upward, a lower surface 15c facing vertically downward, a first side surface 15d facing the retaining wall 11, and a second side surface 15f facing the formwork 12, and the hinge 16 is fixed between the first side surface 15d and the lower surface 15c and to the retaining wall 11. In the retaining wall 11 to which the camber 15 is attached via the hinge 16, the retaining wall 11 and the camber 15 can be easily pulled out, as in the formwork 2 described above.

In the above-described embodiment, an example in which the formwork 2 and the camber 5 are arranged has been described. However, it is also possible to omit at least one of the formwork 2 and the camber 5. For example, when the formwork 2 is omitted, after the structure T is constructed in the space C, the filler material 10 is filled between the retaining wall 1 and the structure T, and the retaining wall 1 is pulled out before the filler material 10 hardens. Even in this case, the same effect as the retaining wall removal method according to the embodiment can be obtained.

In the above-described embodiment, a retaining wall 1 that is a steel sheet pile 1b has been described. However, the retaining wall may be something other than a steel sheet pile 1b, for example, a parent pile. Also, in the above-described embodiment, an example has been described in which the retaining wall removal method according to this embodiment is applied to a site S where a structure T that is an underground structure is constructed. However, the retaining wall removal method according to the present disclosure is not limited to the site S, and can be applied to various sites.

DESCRIPTION OF SYMBOLS 1, 11... Earth retaining wall, 1b... Steel sheet pile, 1c... Bottom part, 1d... Leg part, 1f... Connection part, 2, 12... Formwork, 2b... First surface, 2c... Second surface, 3... Supporting member, 5, 5A, 15... Camber, 5b, 15b... Top surface, 5c, 15c... Bottom surface, 5d... First side surface, 5f... Second side surface, 5g... Slope, 5h... Column, 5j... Slope, 6, 16... Hinge, 10... Filler, 15d... First side, 15f... Second side, B... Ground, C... Space, K... Layer, K1... First surface, K2... Second surface, S... Site, T... Frame, T1... Space, U... Ground surface, W... Interval, X... Building, Y... Backfill soil.

Claims (2)

A process of casting an earth retaining wall into the ground;
excavating the ground located on one side of the earth retaining wall in a plan view;
constructing a structure in the space formed by the excavation;
filling a gap between the retaining wall and the structure with a filler that hardens over time;
Pulling out the earth retaining wall from the ground before the filler hardens;
Equipped with
After the step of constructing the skeleton, a step of installing a form between the retaining wall and the skeleton, and a step of backfilling the space between the form and the skeleton,
In the step of filling the filler, the filler is filled between the retaining wall and the formwork after the step of backfilling,
The method further includes a step of extracting the formwork from the ground after the step of filling the filler.
The step of installing the formwork includes a step of interposing a camber between the retaining wall and the formwork,
The step of extracting the form includes extracting the camber from the filler.
How to remove earth retaining walls. The camber is connected to a surface of the formwork facing the retaining wall via a hinge,
In the step of extracting the camber, the camber is extracted together with the formwork in a rotatable state via the hinge.
The method for removing an earth retaining wall according to claim 1 .

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