Embedded structure construction method

Abstract

To provide a method for pulling out an embedded structure without settlement of the surrounding ground, generation of cracks or the like.SOLUTION: This method is a construction method of an embedded structure. The construction method of an embedded structure comprises: a step of pulling out the embedded structure from the ground from an injection pipe while injecting an injection material having a gel time of 5 to 120 sec.; and a step of pulling out the injection pipe after the end of pulling out a prescribed embedded structure, restriking the injection pipe into a position where the injection material has not completely hardened, and injecting the injection material from the restruck injection pipe while pulling out an adjacent embedded structure yet to be pulled out.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for constructing buried objects such as earth retaining members. [Background technology]

[0002] Excavation work is carried out on the ground to build the foundations of buildings and to install culvert boxes, which are used to house communication lines, etc. When the ground to be constructed is near a coast or river and has a high groundwater level, the bearing capacity of the ground is low, making construction difficult. Therefore, work is carried out to drain the groundwater and lower the groundwater level. Well-point construction and deep well construction methods are known as methods for lowering the groundwater level.

[0003] When using the well point method to lower the groundwater level, the drop in the groundwater level may affect the surrounding ground, causing subsidence and cracks in the surrounding ground. The ground does not subside uniformly (differential settlement), and if there are buildings nearby, they may tilt. Therefore, soil-retaining materials such as steel sheet piles are erected to surround the construction area, and then the well point method is used for construction.

[0004] It is desirable to recover the retaining wall materials rather than leaving them behind, in order to make effective use of resources and reduce greenhouse gas emissions. However, simply pulling them out and removing them can cause the surrounding ground to subside and cracks to form.

[0005] Therefore, as a technique for removing the earth retaining member from the ground, a technique has been proposed in which an injection pipe is inserted into the ground and the earth retaining member is pulled out while injecting an injection material (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-223148 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above-mentioned conventional technology is only applicable to the removal of retaining members, and when it comes to erecting the retaining members, they are erected using conventional methods such as pressing in, which creates cavities between the retaining members and the members during erection, which can become water channels, allowing external groundwater to flow in and causing subsidence or cracks in the surrounding ground. [Means for solving the problem]

[0008] According to an embodiment of the present invention, there is provided a method for constructing a buried object, comprising the steps of: The present invention provides a method for constructing buried objects, which includes the steps of: extracting the buried objects from the ground while injecting an injection material having a gel time of 5 to 120 seconds from an injection pipe; and, after the predetermined buried objects have been extracted, extracting the injection pipe, re-driving the injection pipe at a position where the injection material has not yet hardened, and injecting the injection material from the re-driving injection pipe while extracting adjacent buried objects that have not yet been extracted. [Effects of the Invention]

[0009] By employing the method of the present invention, buried objects can be erected without causing subsidence or cracks in the surrounding ground, and buried objects can also be extracted with high efficiency. [Brief explanation of the drawings]

[0010] [Figure 1] A diagram explaining the well point method. [Figure 2] A diagram showing the sheet pile installation work. [Figure 3] A diagram explaining the state of the ground when sheet piles are erected. [Figure 4] 1 is a flowchart showing the process of erecting sheet piles. [Figure 5] FIG. 1 is a diagram showing an example of the configuration of an injection plant. [Figure 6]FIG. 10 is a diagram showing an example of a connection between an injection plant and an injection pipe. [Figure 7] FIG. 10 is a diagram showing a first example of the structure of the injection pipe. [Figure 8] FIG. 10 is a diagram showing a second example of the structure of the injection pipe. [Figure 9] FIG. 10 is a diagram showing a third example of the structure of the injection pipe. [Figure 10] A diagram showing an example of the installation position of a sheet pile adjacent to an injection pipe. [Figure 11] A diagram showing the injection pipe pushing the adjacent sheet pile. [Figure 12] A diagram explaining the penetration of injection material into the ground. [Figure 13] 10 is a flowchart showing the process of removing sheet piles. [Figure 14] FIG. 2 is a diagram showing an example of the configuration of a switching device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Figure 1 is a diagram illustrating the well point method as an example of a construction method for ground surrounded by sheet piles, which are a type of buried object. The well point method is a construction method in which a pumping pipe 10 is erected into the ground to be constructed, and water is pumped up through a water collection pipe 12 using a vacuum pump 11 to lower the groundwater level. Here, construction using the well point method to lower the groundwater level is given as an example, but the construction is not limited to this type of construction.

[0012] The well point method is used to smoothly carry out underground construction work in ground with low bearing capacity and difficult underground construction work. A similar method is the deep well method, in which a well is dug deep, groundwater is collected in the well by gravity, and the water is then drained using a submersible pump.

[0013] The lift pipes 10 are equipped at their tips with well points 10a each having a mesh strainer. As a result, groundwater containing components smaller than the mesh of the strainer is sucked into the lift pipes 10 and pumped to the surface. The multiple lift pipes 10 are connected to a single collection pipe 12, and a vacuum pump 11 is connected to each collection pipe 12. As a result, the groundwater pumped up each lift pipe 10 is collected in the collection pipe 12, treated as necessary, and released into rivers or sewers.

[0014] When groundwater is sucked up by the vacuum pump 11, negative pressure is created within the ground, and this negative pressure spreads to the surrounding ground. This then draws in groundwater from the surrounding ground, causing the surrounding ground to sink. To prevent this, the sheet piles 13 separate the ground under construction from the surrounding ground.

[0015] The sheet piles 13 are made of ribbed steel plates with a certain strength, and are connected by connecting joints on both sides. By connecting and erecting multiple sheet piles 13, the ground to be constructed is surrounded. This makes it possible to lower the groundwater level by draining only the groundwater in the ground to be constructed while preventing groundwater from flowing in from outside. After the groundwater level has been lowered, excavation is carried out and construction work such as the installation of culvert boxes is carried out.

[0016] Figure 2 shows the operation of erecting sheet piles. The sheet pile 13 can be erected (inserted) into the ground using a pressing machine such as a vibro hammer, silent piler, or crush piler. A vibro hammer is a machine that forcibly vibrates the sheet pile 13, rapidly and temporarily reducing the frictional resistance at the tip and pressing it in. A silent piler is a machine that grasps multiple sheet piles 13 and presses them in with a static load generated by hydraulic pressure, using their pull-out resistance as a counterforce. A crush piler is a machine that performs core-insertion by linking auger excavation and pressing in to press into hard ground containing boulders, gravel, etc. In the example shown in Figure 2, the sheet pile 13 is pressed in using a silent piler 14.

[0017] The silent piler 14 is equipped with a chuck 15 for gripping the sheet pile 13, and a lifting device 16 for raising and lowering the chuck 15. The top of the chuck 15 has a circular opening large enough for the sheet pile 13 to pass through. The silent piler 14 is equipped with multiple gripping portions 17 for gripping the tops of the sheet piles 13 buried in the ground. The gripping portions 17 receive a reaction force from the sheet piles 13 buried in the ground, and the chucks 15 press the sheet piles 13 into the ground. The silent piler 14 is configured so that it can move along the tops of a row of sheet piles 13 in the direction of their arrangement.

[0018] The Silent Piler 14 presses the sheet piles 13 into the ground so that the joints of the sheet piles 13 catch on each other, and presses the sheet piles 13 into the ground so that they surround the ground to be worked on. The Silent Piler 14 is a vibration-free press-in machine, and is useful when there are buildings or other structures near the ground to be worked on.

[0019] Here, with reference to Figure 3, the state of the ground when the sheet pile 13 is being driven will be described. The sheet pile 13 can be driven using a silent piler 14, but in hard ground, it may not be possible to drive the pile using the silent piler 14 alone. In such cases, the silent piler 14 can be used in combination with a water jet. The water jet is high-pressure water that penetrates between the soil particles, creating a condition in which the soil particles can move more easily, reducing the penetration resistance of the sheet pile 13. For even harder ground, a crush piler is used, which drills a hole and simultaneously drives the sheet pile 13 into the ground.

[0020] When the sheet pile 13 is driven using a combination of the silent piler 14 and water jet, a cavity 18 formed by the water jet remains even after the sheet pile 13 is pressed in, as shown in Figure 3(a), and if the cavity 18 is left as is, it will become a water path. The cavity 18 also occurs when the sheet pile 13 is pressed in using only the silent piler 14, a crush piler, or a vibro hammer, and therefore a water path is formed.

[0021] The water path is formed by connecting one side (outside) of the sheet pile 13 through the tip in the depth direction to the other side (inside). Therefore, even if the edge is cut off with the sheet pile 13, groundwater will flow in from the outside through the water path. This will cause the groundwater level in the surrounding ground outside to drop, which could cause subsidence.

[0022] Therefore, as shown in Figure 3(b), the injection material is injected while pressing the sheet pile 13. The formation of water paths can be prevented by instantly filling the cavity 18 with the injection material 19. For ease of understanding, Figure 3(b) shows that a water path of a certain width is formed along the surface of the sheet pile 13, but the shape of the water path is not limited to this. This also applies to the following explanation.

[0023] The grouting material 19 is preferably a low-viscosity material, since it instantly fills the cavity 18. Furthermore, it is desirable for the grouting material 19 to maintain its fluidity while the sheet pile 13 is being pressed into place, and to have a short gel time (the time it takes for the fluidity to be lost and the viscosity to suddenly increase) once the pressing is complete. Such a material may be composed of two liquids, which harden when the two liquids are mixed. When the two liquids are designated as liquid A and liquid B, liquid A may contain cement, water, water glass (aqueous solution of sodium silicate), and an accelerator, while liquid B may contain a hardener, water glass, and water as needed. Liquids A and B may be adjusted so that their gel time after mixing is 5 to 120 seconds.

[0024] Figure 4 is a flowchart showing the procedure for erecting the sheet piles 13. The work begins in step 100, and in step 101, preparations for the erection work are made. The preparations include bringing in the injection plant for injecting the grout into the cavity 18, preparations for filling such as assembly, confirmation of the installation position of the sheet piles 13, and bringing in and installing the silent piler 14 and reaction frame. A weight is placed on the reaction frame according to the soil conditions, the length of the sheet piles 13, etc.

[0025] When erecting the sheet piles 13, one injection pipe can be used for one or more sheet piles 13. In addition, a reaction stand and a weight are used until the press-in machine becomes self-propelled, and the weight loaded on the reaction stand is used as a reaction force.

[0026] In step 102, a plurality of sheet piles 13 are grouped into a group, and a group of sheet piles 13 is selected. The sheet pile 13 at either the left or right end of the selected group includes one sheet pile with an injection pipe placed adjacent to it. In step 103, the injection pipe and the injection plant are connected by a pipe. The sheet pile 13 and the injection pipe may be fixed so as to be detachable.

[0027] In step 104, the selected set of sheet piles 13 are pressed into the ground while the injection material is injected from the injection pipe of the sheet pile 13. The injection material can be injected into the ground while checking whether it leaks to the ground surface depending on the speed at which the sheet piles 13 are pressed in (insertion speed). If there is a large amount of leakage, the pump discharge rate can be reduced because the injection amount is large, and if there is no leakage, the pump discharge rate can be increased. This allows the cavity 18 formed by pressing in the sheet piles 13 to be filled reliably and densely. Note that the injection material can also be filled in voids other than the cavity 18.

[0028] In step 105, it is confirmed whether there is a sheet pile 13 without an injection pipe attached in the selected group. If there is not, the process proceeds to step 102 to select the next group. On the other hand, if there is, the process proceeds to step 106 to erect the sheet pile 13 without an injection pipe in the same group while injecting the injection material from the injection pipe used in step 104.

[0029] In step 107, it is confirmed whether the sheet piles 13 have been installed for all pairs. If not, the process returns to step 102; if installed, the process proceeds to step 108. In step 108, the pipe connecting the injection plant to the injection pipe is removed, the silent piler 14 and injection plant are removed, and the work ends in step 109.

[0030] FIG. 5 is a diagram showing an example of the configuration of an injection plant. The injection plant has the same configuration as an injection plant used when only conventional sheet pile removal work is performed. The injection plant supplies liquid A and liquid B that make up the injection material. The injection plant includes a supply pump 20 that supplies liquid A, a supply pump 21 that supplies liquid B, mixers 22 and 23 for preparing liquid A and liquid B, respectively, and containers 24 to 27 that contain water, hardener, accelerator, cement, water glass, and other ingredients that are used to make liquid A and liquid B, respectively. The injection plant also includes a submersible pump 28 for supplying water and a generator 29 that supplies power to the supply pumps 20 and 21 and the mixers 22 and 23, etc.

[0031] It is desirable that the injection plant be mounted on a vehicle such as a truck and made portable, as this makes it easy to transport the injection plant to the construction site, eliminates the need for installation work for the injection plant, and shortens the construction time.

[0032] The supply pumps 20, 21 are pumps capable of supplying two liquids separately, and for example, positive displacement reciprocating pumps can be used. As the positive displacement reciprocating pump, a dual liquid plunger pump, which can easily change the discharge volume, can be used. The dual liquid plunger pump has two mechanisms for reciprocating rod-shaped pistons using a cam or crank. Here, two supply pumps 20, 21 are used, but this is not limited to this, and two pumps for each liquid may be used, for a total of four pumps. Note that an even number of pumps, six or more, may be used.

[0033] If the two liquids are designated as liquid A and liquid B, liquid A is a liquid prepared by adding cement, water glass, and an accelerator to water, while liquid B is a liquid prepared by adding a hardener and water glass to water. Liquid A is prepared by adding an appropriate amount of water from container 24 using submersible pump 28, and then adding appropriate amounts of cement (e.g., 187.5 kg) and accelerator (e.g., 40 kg) from containers 27 and 25 to mixer 22 and kneading them. Liquid B is prepared similarly by adding an appropriate amount of water from container 26 using submersible pump 28, and then adding an appropriate amount of hardener (e.g., 50 kg) from container 26 to mixer 23 and kneading them. The amount of water added to liquids A and B affects the final mix, so a certain level of accuracy is required. It is desirable to measure the amount using a water meter.

[0034] 6 is a diagram showing an example of connections between an injection plant and injection pipes. The injection plant is connected to a pipe 30 for liquid A, which is connected to a supply pump 20 that supplies liquid A, and a pipe 31 for liquid B, which is connected to a supply pump 21 that supplies liquid B. Pipes 30 and 31 are connected to a Y-shaped pipe 32 via a joint. Y-shaped pipe 32 is connected to an injection pipe 40 via a single mixing pipe 33 and a three-way valve 34.

[0035] The injection pipe 40 includes a connection part (swivel) 41 having two hollow cylindrical members inside that are configured to be freely rotatable with respect to each other at two connection points. The two hollow cylindrical members of the swivel 41 are connected to the three-way valve 34 by two pipes 35 and 36.

[0036] Liquids A and B are mixed in a Y-shaped pipe 32, become one liquid in a mixing pipe 33, flow through pipe 35 or pipe 36 opened by a three-way valve 34, and are supplied to one of the hollow cylindrical members.

[0037] Fig. 7 shows a first example configuration of injection pipe 40. Fig. 7 shows views from the front and side. Injection pipe 40 includes a swivel 41, a rod 42, and a monitor 43. Rod 42 is a tubular member having one end connected to each of two hollow cylindrical members inside swivel 41. The other end of rod 42 is connected to injection material discharge portion 44 provided on monitor 43, which extends horizontally.

[0038] The discharge section 44 is closed with a cap 45 to prevent surrounding soil and sand from flowing in during filling, and the gap in the cap 45 is sealed with a sealing material such as silicone. When the grouting material supplied into the rod 42 flows out, the cap 45 is pushed by the grouting material and blown into the surrounding ground, allowing the grouting material to be injected.

[0039] The injection pipe 40 continuously injects the grout while the specified number of sheet piles 13 are being erected. After the injection of the grout is completed, a small amount of water is immediately supplied into the injection pipe 40 to wash it out. Although a small amount of water is injected into the ground, it is a small amount, and since the grout has already hardened in the cavity 18, it does not affect the surrounding ground.

[0040] The injection pipe 40 is attached to the flat surface of the sheet pile 13 on the side facing the ground (outside). Therefore, the injection pipe 40 has a flat surface adjacent to the flat surface of the sheet pile 13. In addition, the monitor 43 at the tip of the injection pipe 40 in the insertion direction is tapered in the insertion direction of the injection pipe 40 to make it easier to insert the sheet pile 13.

[0041] When erecting the sheet pile 13, for example, a liquid grout is supplied into one of the rods 42 of the injection pipe 40, and the grout is injected from one of the discharge ports 44. The inside of one of the rods 42 and the discharge port 44 are washed with water when erection is complete, and can be used when subsequently pulling out the sheet pile 13. For this reason, the other rod 42 and discharge port 44 can be used as a spare. At this time, a cap can be fitted onto the hollow cylindrical member inside the swivel 41 connected to the rod 42 used during erection, and the rod 42 can be closed to prevent soil and sand flowing backward into the injection plant.

[0042] It may be difficult to completely remove soil and sand from the inside of the rod 42 and the discharge part 44 even when washed with water, so the other spare rod 42 and discharge part 44 can be used when subsequently pulling out the sheet pile 13. For this reason, the injection pipe 40 can be left in place in the ground until the time of pulling out, and can remain attached up to the swivel 41. This makes it easier to change connections and shortens the construction time.

[0043] The injection pipe 40 may be left attached to the sheet pile 13 from the time the sheet pile 13 is erected until it is pulled out so that it can be used immediately when the sheet pile 13 is pulled out. Also, the swivel 41, rod 42, and monitor 43 may be welded together and used.

[0044] FIG. 8 shows a second configuration example of the injection pipe 40. In the injection pipe 40 shown in FIG. 8, the length of the rod 42 is different, and the position of the discharge part 44 is also different. When two rods 42 and two discharge parts 44 are used for both erection and extraction, the injection material moves toward the ground surface where pressure is lower, so it is desirable to inject it from as low as possible during erection. On the other hand, when extracting, it is desirable to inject it from as high as possible during extraction in order to fill the area near the ground surface as quickly and densely as possible to prevent ground subsidence. For these reasons, as shown in FIG. 8, the length of the rod 42 and the position of the discharge part 44 can be changed.

[0045] In the example shown in Figure 8, when erecting, the rod 42 is long and the discharge part 44 is located near the tip of the sheet pile 13, and is used on the right side of the page. When pulling out, the rod 42 is short and the discharge part 44 is located near the top of the sheet pile 13, and is used on the left side of the page.

[0046] The discharge part 44 may be closed with a cap 45 and silicone, but as shown in Figure 8, it can also be closed using a sphere (ball) 46 and an elastic body such as a coil spring 47 to prevent soil and sand from entering the rod 42 depending on whether or not injection material is being supplied.

[0047] In this configuration, before the injection material is supplied, the coil spring 47 is extended and the ball 46 is positioned above the discharge part 44. The ball 46 has a diameter approximately the same as the cross-sectional diameter of the hollow part of the rod 42, and one end of the coil spring 47 is connected below the discharge part 44, while the other end is connected to the ball 46, so that soil and sand that has entered the discharge part 44 is prevented from moving toward the swivel 41. This prevents soil and sand from flowing back toward the injection plant.

[0048] On the other hand, when the grout is supplied, the pressure of the grout pushes the ball 46 downward, causing the coil spring 47 to contract, opening the discharge port 44 and allowing the grout to flow out from the discharge port 44. This eliminates the need for the cap 45 and silicone. In the example shown in Figure 8, both the cap 45 and the ball 46 are provided to provide a double layer of protection against backflow of soil and sand.

[0049] Fig. 9 is a diagram showing a third configuration example of injection tube 40. In the example shown in Fig. 9, two rods 42 have approximately the same length, and discharge portions 44 are also positioned approximately in the same place, with balls 46 and coil springs 47 provided on both.

[0050] In the configuration shown in Figure 8, the rod 42 with the upper discharge portion 44 is pulled out, and the rod 42 with the lower discharge portion 44 is used for erection. If the rod 42 and discharge portion 44 can be cleaned to some extent when erection is completed and can be reused, it may be desirable to use the rod 42 and discharge portion 44 used for erection to pull out the rod, and then use the other spare rod 42 and discharge portion 44 in case of any trouble. In such a case, an injection pipe 40 with the configuration shown in Figure 9 can be used.

[0051] Figure 10 shows an example of the installation position of sheet piles 13 when multiple sheet piles 13 are connected and installed. Although it is possible to install only the sheet piles 13 connected together, this is costly and requires time and effort to replace the injection plant every time a sheet pile 13 is installed. Therefore, it is possible to install injection pipes adjacent to the sheet piles 13, with one injection pipe per many sheet piles 13.

[0052] It is desirable to install one injection pipe for every 1 to several tens of sheet piles 13. While it is also possible to install one injection pipe for every 12 or more sheet piles 13, the distance from the injection pipe increases, making it difficult to instantly inject the material into the cavity 18. Furthermore, in a preferred embodiment, injection is performed from the injection pipe at either the left or right end of multiple consecutive sheet piles 13, for example, 15 or more consecutive sheet piles 13. After a predetermined number of sheets have been extracted and filled, the injection pipe is then extracted. The extracted injection pipe is then re-inserted adjacent to the extracted end of the last sheet pile 13. Since the injection material has not yet been injected for long, it has gelled but has not yet fully hardened, making it easy to insert the injection pipe. The injection pipe can be inserted at the position where the sheet pile 13 was extracted, or at a position in the temporarily weakened ground near the extracted sheet pile 13. Once the installation of the injection pipe is complete, the injection of the grouting material is repeated using the relocated injection pipe while the remaining sheet piles 13 are being extracted. According to this preferred embodiment, efficient simultaneous filling and extraction work is possible without being limited by the number of consecutive sheet piles 13.

[0053] If there are buildings or heavy objects nearby, the ground is subject to load, which makes it easy for the ground to tilt due to the occurrence of cavities 18. For this reason, in areas where there are buildings or heavy objects nearby, the proportion of sheet piles 13 adjacent to injection pipes can be increased, and in areas where there are no buildings or heavy objects nearby, the proportion of sheet piles 13 adjacent to injection pipes can be reduced. By quickly injecting injection material from the injection pipes of the sheet piles 13, it is possible to fill cavities 18 with injection material as soon as they occur.

[0054] In Figure 10, in areas where buildings or heavy objects are nearby, sheet piles 13 are installed at a ratio of one injection pipe for every 1 to 6 sheet piles 13, and in areas where there are no buildings or heavy objects nearby, sheet piles 13 with adjacent injection pipes are installed at a ratio of one injection pipe for every 7 to 11 sheet piles 13. In this way, costs can be reduced by increasing the number of injection pipes in areas where buildings or heavy objects are nearby and the injection material must be packed densely to prevent tilting, but by reducing the number of injection pipes in other areas.

[0055] The location where the sheet pile 13 adjacent to the injection pipe is to be installed can be determined during the design stage, taking into consideration factors such as the log (geological cross section), the injection machine to be used, the permeability coefficient, the surrounding ground, and the presence or absence of buildings or heavy objects. The log is a diagram showing the order and rock type of the layers that make up the geological strata in the area in the form of a column. The permeability coefficient is a coefficient that indicates the degree of permeability of the strata. In addition, in the case of soft ground with a high groundwater level, the number of injection pipes can be increased and the ground can be packed densely.

[0056] 11 is a diagram showing the state in which the sheet pile 13 is erected. Two pipes 30 and 31 are connected to the injection pipe 40, and for example, a single-liquid injection material is supplied only to the pipe 35 to erect the sheet pile 13.

[0057] In hard ground such as boulders and gravel, the sheet pile 13 can only be pressed into at a low speed even when a large force is applied. On the other hand, in soft ground such as silt, the sheet pile 13 can be pressed into at a relatively high speed even with a small force. Therefore, the sheet pile 13 is pressed into the ground at a speed proportional to the force applied by the press machine, which can be changed depending on the geology.

[0058] The speed at which the sheet pile 13 is pressed into the ground can be determined taking into account the geology, the type of pressurizing machine used, and other factors. The injection amount of the grout can be determined based on the determined speed. Because the sheet pile 13 is composed of plates with a constant thickness, the volume of the sheet pile 13 pressed into the ground per unit time can be calculated from the determined speed. The injection amount can be 1 to 10 times the calculated volume, preferably 3 to 5 times. Therefore, each supply pump 20, 21 can supply each liquid so that this injection amount is achieved. The injection rate can be, for example, 20 to 200 L / min. The diameters of the hollow cylindrical member of the swivel 41 and the rod 42 can be appropriately determined to supply this amount of grout, and can be larger than the diameters required in conventional systems where liquid A and liquid B are supplied separately.

[0059] Generally, when a sheet pile 13 is pressed into the ground, as shown in Figure 11(a), a shear force acts on the ground near the sheet pile 13, pulling the ground downward and causing a large depression centered on the sheet pile 13, which in turn causes the surrounding ground to tilt. The tilting range extends several meters from the sheet pile 13, specifically, up to a range of 4 to 5 m.

[0060] However, if the sheet pile 13 is pressed into place while the injection material is being injected, the depression centered on the sheet pile 13 becomes very small, as shown in Figure 11(b). In this case, the range of tilt is only a few tens of centimeters. Therefore, if a building or heavy object is more than 1 meter away, the sheet pile 13 can be erected without the building or heavy object tilting.

[0061] The injection material is not a solution type with high permeability, but a suspension type that emphasizes strength and contains particles such as cement, and does not shrink or separate. Therefore, it does not penetrate widely between the fine soil particles, can instantly fill the cavity 18, and because it does not shrink, it can prevent the ground from tilting.

[0062] FIG. 12 illustrates the penetration of the grout injected through the injection pipe 40 into the ground while the sheet pile 13 is being erected. When the grout is discharged from the horizontally oriented discharge port 44 of the injection pipe 40, it penetrates toward the ground surface, where pressure is low, at an angle of approximately 45°, as shown in FIG. 12. The grout penetrates into gaps between boulders and gravel in the ground and into areas where groundwater is present, filling the gaps and displacing stagnant groundwater. To fill the gaps and replace the groundwater, the grout is supplied in an amount several times greater than the amount required to fill the gaps and replace the groundwater. This allows for instantaneous filling of the gaps and displacing the groundwater. Furthermore, the grout has a short gel time and is a non-shrinking material, reliably preventing ground subsidence.

[0063] Next, the work of removing the erected sheet piles 13 will be explained. The sheet piles 13 surrounding the ground to be constructed are pulled out and removed after construction work such as the installation of culvert boxes is completed. After being removed, the sheet piles 13 can be reused. When the sheet piles 13 are pulled out, the surrounding soil and sand flow into the voids left behind, causing the surrounding ground to subside. For this reason, the sheet piles 13 are pulled out while filling the voids with injection material.

[0064] The same grouting material as used during erection can be used, and the injection amount can be determined according to the extraction speed. In this case, the volume of the sheet pile 13 extracted per unit time can be calculated from the determined speed, and the injection amount can be 1 to 10 times the calculated volume. The injection amount is preferably 3 to 5 times the calculated volume. The injection of the grouting material during extraction is carried out by the negative pressure generated by the extraction of the sheet pile 13, in addition to the pumping pressure and earth pressure of the supply pumps 20, 21 used during erection.

[0065] To remove the sheet pile 13, the sheet pile 13 is pulled out while the grout is being injected through the injection pipe. A press-in machine such as the Silent Piler 14 can also be used to pull out the sheet pile 13. The injection pipe can be the injection pipe attached to the sheet pile 13. The rod 42 and discharge part 44 that injects the grout may be the same as the rod 42 and discharge part 44 that were cleaned when the pile was erected, or a different rod 42 and discharge part 44 from the one used when the pile was erected may be used.

[0066] The work of removing the sheet pile 13 will be described with reference to Figure 13. The work starts in step 200, and preparations for the removal work are made in step 201. The preparations include installing the silent piler 14 and injection plant, and confirming the order in which the sheet pile 13 will be pulled out.

[0067] In step 202, a set of sheet piles 13 is selected. In step 203, the injection pipes of the selected set are connected to the injection plant with the injection pipes of the adjacent sheet piles 13 to prepare for the supply of injection material.

[0068] In step 204, it is confirmed whether there are any sheet piles 13 to be extracted in the selected group. If there are, the process proceeds to step 205, where the silent piler 14 is used to extract the sheet piles 13 in the same group while the injection pipe of the selected group injects grout from the injection pipe of the adjacent sheet pile 13. On the other hand, if there are no sheet piles, the process proceeds to step 207.

[0069] In step 206, it is checked whether there are any unpulled sheet piles 13 in the same group. If there are, the process returns to step 205, and the unpulled sheet piles 13 without injection pipes are pulled out while injecting the injection material. If there are no unpulled sheet piles, the process proceeds to step 207.

[0070] In step 207, since there are no sheet piles 13 in the selected group or all sheet piles 13 without injection pipes have been pulled out, the sheet piles 13 in the selected group are pulled out last together with their injection pipes. At this time, injection material is injected from the injection pipe adjacent to the sheet pile 13, while the sheet pile 13 and the injection pipe are pulled out. After that, the injection pipe is driven into the ground adjacent to the sheet pile 13 that has not yet been pulled out, from which the sheet pile has already been pulled out, and the remaining sheet piles 13 are filled with injection material at that position while being pulled out.

[0071] In step 208, it is confirmed whether all the sheet piles 13 have been pulled out. If not, the pulled out injection pipe or a spare injection pipe is driven near another set of sheet piles 13 that have already been pulled out, and then the process returns to step 202, another set is selected, and the sheet piles 13 are pulled out in the same manner. On the other hand, if the process is complete, the process proceeds to step 209, where the injection plant is dismantled and loaded onto a truck or the like for transport, and the silent piler 14 is also loaded onto a low-bed trailer or the like for transport, and the work ends in step 210.

[0072] In this case too, when only a few sheet piles 13 remain, a reaction force stand is brought in and set up, a weight is loaded on it, and the weight on the reaction force stand is used as a reaction force, allowing the remaining sheet piles 13 to be pulled out continuously without any limit on the number.

[0073] In sandy ground, when injection material is injected, the sand particles move with the injection material, filling the gaps between the sand particles and making them denser, which increases the frictional force with the sheet pile 13. This increase in frictional force is called jamming. When jamming occurs, the sheet pile 13 cannot be pulled out.

[0074] However, in this method, jamming can be prevented by supplying a large amount of grout, several times the required amount, in accordance with the speed at which the sheet pile 13 is erected or pulled out. This is because by quickly injecting a large amount of grout, the grout can fill the gaps before the sand particles move, and the fluidity of the grout is maintained near the sheet pile 13 as the sheet pile 13 is pressed in or pulled out.

[0075] The injection pipe 40 is kept installed in the ground from the time it is erected until it is pulled out, so that the condition of the surrounding ground can be checked, an injection plant can be connected as needed, and the injection material can be injected.

[0076] The sheet pile 13 erection and extraction work can be performed by continuously erecting and extracting the sheet pile 13, and continuously injecting the grout. However, this is not limited to this. For example, the sheet pile 13 may be erected and extracted by repeating the step of injecting a certain amount of grout every time the sheet pile 13 is erected to a certain height and every time it is extracted. In this case, it is possible to check whether a certain amount of grout has been injected at each step. Whether a certain amount of grout has been injected can be checked, for example, by checking whether the grout has leaked to the ground surface.

[0077] In the explanation so far, the connection between the injection pipe of the sheet pile 13 and the injection plant was changed each time a group of sheet piles including one sheet pile 13 was erected or each time a group of sheet piles was pulled out.

[0078] However, such reconnection takes time and effort. Therefore, a switching device 60 as shown in Figure 14(a) can be used to make the switching easier. The switching device 60 includes two three-way valves 61 with inlets and outlets for fluids in three directions. The three-way valves 61 have one inlet and two outlets.

[0079] One inlet of the three-way valve 61 is connected to a pipe (hose) 62 that supplies, for example, a single-liquid injection material, and the two outlets are connected via hoses 65 and 66 to a swivel 63 of the injection pipe 40 to which the injection material is to be supplied and a swivel 64 of the next injection pipe 40 that supplies the injection material.

[0080] The inlets of the hollow cylindrical members of the swivels 63, 64 on the sides to which the hoses 65, 66 are not connected are closed with caps 67, 68. If there are gaps around the caps 67, 68, the gaps can be filled with silicone.

[0081] The three-way valve 61 has a lever 69 that can rotate approximately 90 degrees, and inside it, as shown in Figure 14(b), has a cylindrical cavity 70, three communication passages 71 to 73 that connect the cavity 70 to each inlet and outlet, and an L-shaped passage 74 that rotates as the lever 69 rotates.

[0082] As shown in Figure 14(c), when lever 69 is at position D, that is, when the other end of lever 69, which rotates around one end, is at position D, L-shaped passage 74 connects communicating passage 72, to which hose 62 is connected, with communicating passage 71, to which hose 65 is connected, and causes the injection material, which is made up of one liquid and has flowed down hose 62, to flow into hose 65 and be supplied to swivel 63.

[0083] When the other end of lever 69 is tilted in the direction of arrow E to rotate lever 69, the internal L-shaped passage 74 also rotates as lever 69 rotates. When the other end of lever 69 reaches position F, passage 74 connects communicating passage 72, to which hose 62 is connected, with communicating passage 73, to which hose 66 is connected. This allows the single-component injection material that has flowed through hose 62 to flow into hose 66 and be supplied to swivel 64.

[0084] When switching is performed, the injection material is no longer supplied to swivel 63, so that further switching is possible by disconnecting hose 65 from swivel 63 while supplying injection material to swivel 64 and then connecting hose 65 to the swivel of the next injection pipe 40.

[0085] The injection plant may be equipped with two or more sets of supply pumps 20, 21 for supplying liquid A and liquid B, and may be capable of simultaneously supplying the grouting material to two or more injection pipes 40. Also, two or more injection plants may be used to simultaneously supply the grouting material to two or more injection pipes 40. In the case of a plant capable of simultaneously supplying the grouting material to two or more injection pipes 40, two or more switching devices 60 may be used to facilitate switching to the next two or more injection pipes 40.

[0086] As explained above, by adopting this method, buried objects can be erected and removed while appropriately injecting the grout. Therefore, even if a building or heavy object is located nearby, buried objects can be erected and removed while preventing the building or heavy object from sinking. Furthermore, this method allows for efficient extraction of buried objects while injecting grout, thereby enabling simultaneous filling and extraction to be performed with high efficiency.

[0087] Up to this point, the buried object construction method of the present invention has been described in detail with reference to the embodiment shown in the drawings, but the present invention is not limited to the above-mentioned embodiment, and can be modified within the scope of what a person skilled in the art can conceive, such as other embodiments, additions, changes, deletions, etc., and any aspect is included in the scope of the present invention as long as it achieves the functions and effects of the present invention. [Explanation of symbols]

[0088] 10...Rising pipe 10a...Well Point 11...Vacuum pump 12...Water collection pipe 13...Sheet pile 14...Silent Piler 15...Chuck 16...Lifting device 17...Grip part 18...Cavity 19...Injection material 20, 21...Supply pump 22, 23...Mixer 24~27…Container 28...Submersible pump 29...Generator 30, 31, 33, 35, 36...tube 32...Y-shaped tube 34...Three-way valve 40...Injection tube 41...Swivel 42...Rod 43...Monitor 44...Discharge part 45...Cap 46...Ball 47...Coil spring 50, 51...Hose 60...Switching device 61...Three-way valve 62, 65, 66...Hose 63, 64...Swivel 67, 68...Cap 69...Lever 70...Cavity 71~73…Communication path 74...Aisle

Claims

1. A method for constructing a buried object, comprising: a step of extracting the buried object from the ground while injecting an injection material having a gel time of 5 to 120 seconds from an injection pipe; After the extraction of the predetermined buried objects has been completed, the injection pipe is extracted, the injection pipe is re-cast in a position where the grouting material has not yet hardened, and the grouting material is injected from the re-cast injection pipe while extracting the adjacent buried objects that have not yet been extracted. A method for constructing buried objects, including:

2. 2. The construction method according to claim 1, wherein the injection amount of the injection material is 1 to 10 times the calculated volume of the buried object to be extracted.

3. 3. The construction method according to claim 1, wherein the position where the injection material has not completely hardened is a position where the buried object has been extracted or a position in the ground near the position where the buried object has been extracted.

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