Methods for constructing buried structures

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

[0006] , , , , , ,

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

Background Art

[0002] The ground is excavated for constructing the foundation of a building and installing box culverts (culvert boxes) used for purposes such as accommodating communication lines. When the ground to be constructed is a ground with a high groundwater level near the coast, river, etc., the bearing capacity of the ground is low and the construction is difficult. Therefore, a construction is carried out to drain groundwater and lower the groundwater level. As a method for lowering the groundwater level, a well point method, a deep well method, etc. are known.

[0003] When carrying out a construction to lower the groundwater level using the well point method, the lowering of the groundwater level also affects the surrounding ground, and there is a possibility that settlement, cracks, etc. may occur in the surrounding ground. The ground does not settle uniformly (differential settlement), and if there are buildings, etc. in the vicinity, there is a possibility that the buildings, etc. may tilt. Therefore, an earth retaining member such as a steel sheet pile is driven in and the construction site is surrounded, and then the construction is carried out using the well point method.

[0004] In order to suppress the effective use of resources and the generation of greenhouse gases, it is desirable not to leave the earth retaining member unused but to recover it. However, if it is simply pulled out and removed, there is a possibility that the surrounding ground may settle and cracks, etc. may occur.

[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

Summary of the Invention

[0007] However, the above-mentioned conventional technology is only applicable to the removal of retaining wall members. When retaining wall members are installed, conventional methods such as press-in are used, which creates a cavity between the retaining wall member and the surrounding ground. This creates a water channel, allowing external groundwater to flow in, potentially causing subsidence and cracking of the surrounding ground. [Means for solving the problem]

[0008] According to an embodiment of the present invention, a method for constructing buried objects, A method for constructing buried objects is provided, comprising the steps of: withdrawing the buried object from the ground while injecting an injection material having a gel time of 5 to 120 seconds from an injection pipe; and, after the withdrawal of a predetermined buried object is completed, withdrawing the injection pipe, re-driving the injection pipe into a position where the injection material has not yet hardened, and injecting the injection material from the re-driving injection pipe while withdrawing adjacent buried objects that have not yet been withdrawn. [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 the buried objects can also be extracted with high efficiency. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram explaining the wellpoint construction method. [Figure 2] A diagram showing the process of installing sheet piles. [Figure 3] A diagram illustrating the ground conditions during the installation of sheet piles. [Figure 4] A flowchart illustrating the process of installing sheet piles. [Figure 5] A diagram showing an example of the configuration of an injection plant. [Figure 6]A diagram showing an example of the connection between an injection plant and an injection pipe. [Figure 7] A diagram showing the first example of the structure of an injection tube. [Figure 8] A diagram showing a second example of the structure of an injection tube. [Figure 9] A diagram showing a third example of the structure of an injection tube. [Figure 10] A diagram showing an example of the installation location of a sheet pile adjacent to an injection pipe. [Figure 11] A diagram showing how an injection pipe is embedded in an adjacent sheet pile. [Figure 12] A diagram illustrating the seepage of injection material into the ground. [Figure 13] A flowchart showing the process for removing sheet piles. [Figure 14] A diagram showing an example configuration of a switching device. [Modes for carrying out the invention]

[0011] Figure 1 illustrates the wellpoint method as an example of a construction method for ground surrounded by sheet piles, which are a type of buried structure. The wellpoint method involves installing a pumping pipe 10 into the ground to be constructed, and using a vacuum pump 11 to pump water through a collection pipe 12 to lower the groundwater level. Here, a construction project to lower the groundwater level using the wellpoint method is given as an example, but the construction is not limited to this project.

[0012] The wellpoint method is used to facilitate underground construction in areas with low bearing capacity and difficult underground work conditions. A similar method is the deep well method, which involves drilling a deep well, collecting groundwater into the well by gravity, and draining it with a submersible pump.

[0013] The lift pipe 10 is provided with a well point 10a having a net-like strainer at its tip. Therefore, groundwater containing components smaller than the mesh of the strainer is sucked into the lift pipe 10 and pumped up to the ground surface. A plurality of lift pipes 10 are connected to a single header pipe 12, and a vacuum pump 11 is connected to the single header pipe 12. Therefore, the groundwater pumped up by each lift pipe 10 is collected in the header pipe 12, and drainage treatment is performed as necessary, and then discharged into a river or sewer.

[0014] When the vacuum pump 11 sucks groundwater, the ground inside becomes negative pressure, and this negative pressure propagates to the surrounding ground. Then, the groundwater in the surrounding ground is sucked in, and the surrounding ground subsides. To prevent this, a sheet pile 13 is used to separate the ground to be constructed from the surrounding ground.

[0015] The sheet pile 13 has a predetermined strength and is made of ribbed iron plates as piles, and is connected by connecting the joints provided on both sides. By driving in a plurality of sheet piles 13 while connecting them, the ground to be constructed can be surrounded. As a result, it is possible to suppress the inflow of groundwater from the outside and drain only the groundwater in the ground to be constructed to lower the groundwater level. The ground with the lowered groundwater level is excavated, and work such as the installation of a culvert box is carried out.

[0016] Figure 2 is a diagram showing the state of the driving operation of the sheet pile. The sheet pile 13 can be driven (inserted) into the ground using a press-fitting machine such as a vibro hammer, a silent piler, or a crash piler. The vibro hammer is a machine that forcibly vibrates the sheet pile 13 to rapidly and temporarily reduce the frictional resistance at the tip and press it in. The silent piler is a machine that grasps a plurality of sheet piles 13 and presses the sheet pile 13 with a static load by hydraulic pressure using the pullout resistance as the reaction force. The crash piler is a machine that performs core extraction press-fitting in which auger excavation and press-fitting are interlocked in order to press into a hard ground containing gravel, sand, etc. In the example shown in Figure 2, the sheet pile 13 is being pressed in by the silent piler 14.

[0017] The Silent Piler 14 is equipped with a chuck 15 for gripping the sheet piles 13 and a lifting device 16 for raising and lowering the chuck 15. The top of the chuck 15 is provided with a circular opening large enough for the sheet piles 13 to pass through. The Silent Piler 14 is equipped with multiple gripping parts 17 for gripping the tops of the sheet piles 13 embedded in the ground. The gripping parts 17 take reaction force from the sheet piles 13 embedded in the ground and press the sheet piles 13 into the ground using the chuck 15. The Silent Piler 14 is configured to move along the tops of the sheet piles 13 arranged in a row and move in the direction of their arrangement.

[0018] The Silent Piler 14 presses in the sheet piles 13 so that their joints interlock, and installs the sheet piles 13 in the ground so that they surround the ground to be constructed. 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 constructed.

[0019] Here, referring to Figure 3, the condition of the ground when the sheet piles 13 are erected will be explained. The sheet piles 13 can be erected using a silent piler 14, but in the case of hard ground, it may not be possible to drive them using only the silent piler 14. In that case, the silent piler 14 can be used in combination with water jet water. Water jet water is high-pressure water that penetrates between soil particles, creating a condition in which soil particles can move easily, and reducing the penetration resistance of the sheet piles 13. Furthermore, for even harder ground, a crush piler is used, which drills holes and pushes the sheet piles 13 in at the same time.

[0020] When sheet piles 13 are driven using a silent piling machine 14 and a water jet, as shown in Figure 3(a), the cavities 18 formed by the water jet remain even after the sheet piles 13 are pressed in. If these cavities 18 are left as they are, they become water channels. Cavities 18 also occur when pressing in with only the silent piling machine 14, with a crush piling machine, or with a vibro hammer, thus forming water channels.

[0021] The water channel is formed by connecting one side (outside) of the sheet pile 13 through its tip in the depth direction to the other side (inside). Therefore, even if the sheet pile 13 is used to create an isolation barrier, groundwater can flow in from the outside through the water channel. This can cause the groundwater level of the surrounding ground (outside) to drop, potentially leading to subsidence.

[0022] Therefore, as shown in Figure 3(b), the injection material is injected while the sheet pile 13 is pressed in. By instantly filling the cavity 18 with the injection material 19, the formation of water channels can be prevented. In Figure 3(b), for ease of understanding, a water channel of a certain width is shown to be formed along the surface of the sheet pile 13, but the shape of the water channel is not limited to this. This is also true in the following explanation.

[0023] The injection material 19 should be a low-viscosity material in order to instantly fill the cavity 18. Furthermore, the injection material 19 should maintain fluidity while the sheet pile 13 is being pressed in, and have a short gel time (the time it takes for fluidity to be lost and viscosity to rapidly increase) once the pressing is complete. Such a material can be a two-component material that hardens when the two components are mixed. If the two components are designated as component A and component B, component A may contain cement, water, water glass (aqueous sodium silicate solution), and an accelerator, while component B may contain a hardening agent, water glass, and water as appropriate. Components A and B can be used with a gel time adjusted to 5 to 120 seconds after mixing.

[0024] Figure 4 is a flowchart showing the flow of the sheet pile installation work. The work starts from step 100, and in step 101, preparations for the installation work are carried out. Preparations include bringing in and assembling the injection plant for injecting the injection material into the cavity 18, confirming the installation position of the sheet pile 13, bringing in and installing the silent piler 14 and reaction frame. Weights are loaded onto the reaction frame according to the soil conditions and the length of the sheet pile 13.

[0025] When installing sheet piles 13, injection can be performed using one injection pipe for each sheet pile 13. In addition, a reaction force stand and weights are used until the press-in machine becomes self-propelled, and the weights loaded on the reaction force stand are used as the reaction force.

[0026] In step 102, multiple sheet piles 13 are grouped together, and a group of sheet piles 13 is selected. The selected group includes one sheet pile 13 at either the left or right end that has an injection pipe positioned adjacent to it. In step 103, the injection pipe and the injection plant are connected by a pipe. The sheet piles 13 and the injection pipe may be fixed in a way that allows them to be detachably attached.

[0027] In step 104, the selected set of sheet piles 13 are pressed into the ground and erected while the injection material is injected from the injection pipes of the sheet piles 13. The injection material can be injected into the ground while confirming that it leaks to the ground surface, depending on the speed at which the sheet piles 13 are pressed in (insertion speed). If the amount of leakage is large, the amount of injection is large, so the discharge rate of the pump can be reduced, and if there is no leakage, the discharge rate of the pump can be increased. This ensures that the cavities 18 formed by the pressing in of the sheet piles 13 are filled reliably and densely. The injection material can also be used to fill voids other than the cavities 18.

[0028] In step 105, check if the selected set contains any sheet piles 13 that do not have injection pipes attached. If not, proceed to step 102 and select the next set. If there are any, proceed to step 106 and install the sheet piles 13 from that same set without injection pipes, injecting the injection material through the injection pipe used in step 104.

[0029] In step 107, verify whether the sheet piles 13 have been installed for all sets. If they have not been installed, return to step 102; if they have been installed, proceed to step 108. In step 108, disconnect the pipes connecting the injection pipes to the injection plant, remove the silent pilers 14 and the injection plant, and complete the work in step 109.

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

[0031] It is desirable that the injection plant be mounted on a vehicle such as a truck and be mobile. This is because it facilitates the movement of the injection plant to the construction site, eliminates the need for installation work, and shortens the construction period.

[0032] The supply pumps 20 and 21 are pumps capable of supplying two liquids separately, and for example, positive displacement reciprocating pumps can be used. As a positive displacement reciprocating pump, a two-liquid plunger pump that allows for easy variation of the discharge rate can be used. A two-liquid plunger pump has two sets of mechanisms that reciprocate rod-shaped pistons using cams or cranks. Here, two supply pumps 20 and 21 are used, but this is not the only option; two pumps may be used for each liquid, for a total of four pumps. The number of pumps should be even, and six or more pumps may be used.

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

[0034] Figure 6 shows an example of the connection between the injection plant and the injection pipe. 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 to 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 fittings. The Y-shaped pipe 32 is connected to the injection pipe 40 via a mixing pipe 33 and a three-way valve 34.

[0035] The injection pipe 40 includes a connecting section (swivel) 41 which contains two hollow cylindrical members configured to rotate freely relative to each other at two connection points. The two hollow cylindrical members of the swivel 41 are connected by a three-way valve 34 and two pipes 35 and 36.

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

[0037] Figure 7 shows a first configuration example of the injection pipe 40. Figure 7 is a front and side view. The injection pipe 40 includes a swivel 41, a rod 42, and a monitor 43. The rod 42 is a tubular member with one end connected to each of the two hollow cylindrical members in the swivel 41. The other end of the rod 42 is connected to a discharge section 44 of the monitor 43 that extends horizontally for discharging the injection material.

[0038] The discharge section 44 is closed with a cap 45 to prevent surrounding soil and other debris from flowing in during installation, and the gap in the cap 45 is sealed with a sealing material such as silicone. The cap 45 is pushed out into the surrounding ground by the injection material as the injection material supplied into the rod 42 flows out. This enables the injection of the injection material.

[0039] The injection pipe 40 continuously injects the grout material while a predetermined number of sheet piles 13 are being erected. Immediately after the injection of the grout material is complete, a small amount of water is supplied to the inside of the injection pipe 40 to clean it. Although a small amount of water is injected into the ground, it is a small amount and the void 18 will not affect the surrounding ground because the grout material has already hardened.

[0040] The injection pipe 40 is attached to the flat surface on the side (outer side) of the sheet pile 13 that faces the surrounding ground. 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 toward the insertion direction of the injection pipe 40 in order to facilitate the insertion of the sheet pile 13.

[0041] In the injection pipe 40, for example, during installation, a liquid injection material is supplied into one rod 42, and the injection material is injected from one discharge port 44. The inside of one rod 42 and the discharge port 44 are washed with water when installation is complete and can be used again when the sheet pile 13 is withdrawn. For this reason, the other rod 42 and discharge port 44 can be kept as spares. At this time, a cap can be fitted onto the hollow cylindrical member inside the swivel 41 connected to the rod 42 used during installation, thereby closing off the backflow of soil and other materials inside the rod 42 to prevent them from entering the injection plant.

[0042] Furthermore, since it may be difficult to completely remove soil and other debris from inside the rod 42 and discharge section 44 even with water washing, the other spare rod 42 and discharge section 44 can be used when withdrawing the sheet pile 13. For this reason, the injection pipe 40 can be left installed in the ground and the swivel 41 attached until withdrawal. This makes reconnection easier and shortens construction time.

[0043] The injection pipe 40 may be kept attached to the sheet pile 13 from the time it is erected until it is removed, so that it can be used immediately when the sheet pile 13 is removed. In addition, the swivel 41, rod 42, and monitor 43 can be used in a form that has been welded together.

[0044] Figure 8 shows a second example configuration of the injection pipe 40. In the injection pipe 40 shown in Figure 8, the length of the rods 42 is different, and the position of the discharge section 44 is also different. When using two rods 42 and two discharge sections 44 for incorporation and withdrawal respectively, the injection material moves towards the ground surface where the pressure is lower, so it is desirable to inject from as low a position as possible when incorporation. On the other hand, when withdrawing, it is desirable to inject from as high a position as possible in order to densely fill the area near the ground surface as quickly as possible to prevent the ground from settling. For these reasons, as shown in Figure 8, the length of the rods 42 and the position of the discharge section 44 can be changed.

[0045] In the example shown in Figure 8, when installing, the rod 42 is longer and the discharge section 44 is located closer to the tip of the sheet pile 13, and the one on the right side of the page is used. When withdrawing, the rod 42 is shorter and the discharge section 44 is located closer to the top of the sheet pile 13, and the one on the left side of the page is used.

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

[0047] In this configuration, before the injection material is supplied, the coil spring 47 extends, and the ball 46 is positioned above the discharge section 44. The ball 46 has approximately the same diameter as the cross-sectional diameter of the hollow portion of the rod 42. One end of the coil spring 47 is connected below the discharge section 44, and the other end is connected to the ball 46. This prevents soil and other materials that have entered the discharge section 44 from moving towards the swivel 41. Therefore, it prevents soil and other materials from flowing back towards the injection plant.

[0048] On the other hand, when the injection material is supplied, the pressure of the injection material pushes the ball 46 downwards, compressing the coil spring 47, opening the discharge opening 44, and allowing the injection material to flow out from the discharge opening 44. Therefore, the cap 45 and silicone are unnecessary. In the example shown in Figure 8, both the cap 45 and the ball 46 are provided to prevent backflow of soil and other materials in a double layer.

[0049] Figure 9 shows a third configuration example of the injection pipe 40. In the example shown in Figure 9, the two rods 42 are of approximately the same length, the position of the discharge section 44 is also approximately the same, and both are provided with a ball 46 and a coil spring 47.

[0050] In the configuration shown in Figure 8, the end with the discharge section 44 on the upper side is withdrawn, and the end with the discharge section 44 on the lower side is used for upright installation. If the cleaning performed after upright installation is sufficient to allow for reuse, the rod 42 and discharge section 44 used during upright installation can be withdrawn, and in the event of any trouble, the other spare rod 42 and discharge section 44 may be available. In such cases, the 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. While it is possible to install only the sheet piles 13 by connecting them, this is costly, and changing the injection plant each time a sheet pile 13 is erected is time-consuming. Therefore, injection pipes can be installed adjacent to the sheet piles 13 at a ratio of one pipe per sheet pile 13.

[0052] It is preferable to install one injection pipe for every 1 to several tens of sheet piles 13. While one pipe for every 12 or more sheet piles 13 is also acceptable, the increased distance from the injection pipe makes instantaneous injection into the cavity 18 difficult. Furthermore, a preferred embodiment involves injecting into multiple sheet piles, for example, 15 or more consecutive sheet piles 13, from an injection pipe at either the left or right end, and after a predetermined number of sheets have been pulled out and filled, the injection pipe is withdrawn. The withdrawn injection pipe is then reinstalled adjacent to the end of the last sheet pile 13 that has already been pulled out. At this time, since the injection material has not been injected for long, it has gelled but has not yet fully hardened, making it easy to reinstall the injection pipe. This reinstallation location may be the location where the sheet piles 13 were pulled out, or it may be a location in the temporarily softened ground near where the sheet piles 13 were pulled out. Once the injection pipes have been installed, the injection of the injection material is repeated using the relocated injection pipes while the remaining sheet piles 13 are being pulled out. According to this preferred embodiment, efficient simultaneous filling and pulling work is possible without being limited by the number of consecutive sheet piles 13.

[0053] When there are buildings or heavy objects nearby, the ground is subjected to load, making it more likely for the ground to tilt due to the formation of voids 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, while in areas where there are no buildings or heavy objects nearby, the proportion of sheet piles 13 adjacent to injection pipes can be decreased. By quickly injecting the injection material from the injection pipes of the sheet piles 13, the voids 18 can be filled with the injection material at the same time they form.

[0054] Figure 10 shows that in areas near buildings or heavy objects, one injection pipe is installed for every 1 to 6 sheet piles 13, while in areas without nearby buildings or heavy objects, one injection pipe is installed 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 densely packed to prevent tilting, while decreasing the number of injection pipes in other areas.

[0055] The location where the sheet piles 13 adjacent to the injection pipes are installed can be determined during the design phase, taking into consideration the columnar section (geological cross-section), the injection machine to be used, the permeability coefficient, the surrounding ground conditions, and the presence or absence of buildings or heavy objects. A columnar section is a diagram that shows the order of layers and rock types that make up the geological strata of the area in a columnar shape. The permeability coefficient is a coefficient that indicates the degree of permeability of the geological layers. In addition, in the case of soft ground with a high groundwater level, the number of injection pipes can be increased and the area can be filled more densely.

[0056] Figure 11 shows the process of erecting the sheet pile 13. Two pipes 30 and 31 are connected to the injection pipe 40. For example, a single-component injection material is supplied to only pipe 35 to erect the sheet pile 13.

[0057] In hard ground containing boulders, sand, and gravel, even with a large force applied, the sheet piles 13 can only be driven in at a low speed. On the other hand, in soft ground such as silt, the sheet piles 13 can be driven in at a relatively high speed even with a small force. Therefore, the sheet piles 13 are driven into the ground at a speed proportional to the force applied by the driving machine, which can be changed according to the geological conditions.

[0058] The rate at which the sheet piles 13 are driven in can be determined considering the geological conditions and the driving machine used. The amount of grout injected can be determined according to the determined rate. Since the sheet piles 13 are made up of plates of a certain thickness, the volume of sheet piles 13 driven in per unit time can be calculated from the determined rate. The injection amount can be 1 to 10 times the calculated volume, and preferably 3 to 5 times. Therefore, each supply pump 20, 21 can supply each liquid to achieve this injection amount. The injection amount can be, for example, 20 to 200 L / min. The diameter of the hollow cylindrical member of the swivel 41 and the rod 42 can be set to an appropriate diameter to supply this amount of grout, and can be larger than the diameters used when liquid A and liquid B are supplied separately in the conventional method.

[0059] Generally, when a sheet pile 13 is driven into the ground, as shown in Figure 11(a), a shear force acts on the ground near the sheet pile 13, pulling the ground near the sheet pile 13 downwards. This causes a large depression around the sheet pile 13, and consequently, the surrounding ground tilts. The tilted area extends several meters from the sheet pile 13, specifically to an area of ​​4-5 meters.

[0060] However, when the sheet pile 13 is pressed in 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 area of ​​inclination is only about several tens of centimeters. Therefore, if the 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] Furthermore, the injection material is not a highly permeable solution type, but rather a suspension type that prioritizes strength and contains particulate matter such as cement, and does not shrink or separate. Therefore, it does not penetrate widely between fine soil particles, can instantly fill voids 18, and because it does not shrink, it can suppress the tilting of the ground.

[0062] Figure 12 illustrates the infiltration of the injection material into the ground while the sheet piles 13 are being erected. When the injection material is discharged from the horizontally oriented discharge section 44 of the injection pipe 40, it infiltrates at an angle of approximately 45° toward the ground surface where the pressure is lower, as shown in Figure 12. The injection material infiltrates into gaps between boulders and gravel in the ground, as well as into areas with groundwater, filling these gaps and displacing stagnant groundwater, filling the spaces and replacing the groundwater. In this way, to fill the gaps and replace the groundwater with the injection material, several times the amount necessary to fill the gaps and replace the groundwater is supplied. This allows for instantaneous filling of gaps and replacement of groundwater, and because the injection material has a short gel time and is a non-shrinking material, ground settlement can be reliably suppressed.

[0063] Next, we will explain the process of removing the installed sheet piles 13. The sheet piles 13 surrounding the ground to be constructed will be pulled out and removed after the completion of construction work such as the installation of the culvert boxes. After removal, the sheet piles 13 can be reused. When the sheet piles 13 are pulled out, surrounding soil and sand will flow into the void left by the removal, causing the surrounding ground to settle. Therefore, the sheet piles 13 are pulled out while filling the void with an injection material.

[0064] The same injection material used during installation can be used, and the injection amount can be determined according to the extraction speed. In this case as well, the volume of sheet piles 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. Preferably, the injection amount is 3 to 5 times the calculated volume. The injection of the injection material during extraction is carried out by the negative pressure generated by the extraction of the sheet piles 13, in addition to the pumping pressure and soil pressure from the supply pumps 20 and 21 used during installation.

[0065] The sheet pile 13 is removed by pulling it out while injecting the injection material from the injection pipe. A press-in machine such as a 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 for injecting the injection material may be the rod 42 and discharge part 44 that were cleaned during installation, or a different rod 42 and discharge part 44 may be used.

[0066] Referring to Figure 13, the procedure for removing the sheet piles 13 will be described. The procedure begins in step 200, and in step 201, preparations for the removal work are carried out. These preparations include setting up the silent piler 14 and injection plant, and confirming the order of pulling out the sheet piles 13.

[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 pipes of adjacent sheet piles 13 and to the injection plant, and preparations are made for the supply of the injection material.

[0068] In step 204, check if there is a sheet pile 13 to be pulled out in the selected set. If there is, proceed to step 205, where the silent piler 14 is used to pull out the sheet pile 13 of the same set, injecting the filler from the filler pipe of the selected set through the filler pipe of the adjacent sheet pile 13. If there is no sheet pile 13, proceed to step 207.

[0069] In step 206, check if there are any sheet piles 13 that have not been pulled out in the same set. If there are, return to step 205 and pull out the sheet piles 13 that have not been pulled out and do not have an injection tube, while injecting the injection material. If there are no sheet piles 13 that have not been pulled out, proceed to step 207.

[0070] In step 207, if the selected set does not have a sheet pile 13, or if all sheet piles 13 without injection pipes have been removed, the sheet piles 13 of the selected set are removed last, along with their injection pipes. At this time, the sheet piles 13 and injection pipes are removed while injecting the grout from the injection pipe adjacent to the sheet pile 13. After that, the injection pipes are set into the ground where sheet piles have already been removed, adjacent to the sheet piles 13 that have not yet been removed, and the remaining sheet piles 13 are removed while the grout is filled in at that location.

[0071] In step 208, it is checked whether all sheet piles 13 have been removed. If not, the removed injection pipes or spare injection pipes are driven into the ground near another set of sheet piles 13 that have already been removed, and then the process returns to step 202, another set is selected, and the sheet piles 13 are removed in the same manner. If the process is complete, the process proceeds to step 209, where the injection plant is dismantled and transported away on a truck or similar vehicle. The silent piler 14 is also loaded onto a low-bed trailer or similar vehicle and transported away, and the work is completed in step 210.

[0072] In this case as well, when only a few sheet piles 13 remain, the reaction force frame is brought in and installed, weights are loaded onto it, and the weights on the reaction force frame are used as a reaction force, allowing the remaining sheet piles 13 to be continuously pulled out without limit on the number.

[0073] Incidentally, in sandy ground, when grout is injected, the sand particles move due to the grout, filling the gaps between the sand particles and becoming denser, increasing the frictional force with the sheet pile 13. This increase in frictional force is called jamming. When jamming occurs, the sheet pile 13 becomes impossible to pull out.

[0074] However, in this method, a large amount of injection material, several times the required amount, is supplied in accordance with the rate at which the sheet piles 13 are erected or withdrawn, thereby suppressing the occurrence of jamming. This is because, by quickly injecting a large amount of injection material, the gaps can be filled with the injection material before the sand particles can move, and in the vicinity of the sheet piles 13, the fluidity of the injection material is maintained as the sheet piles 13 are pressed in or pulled out.

[0075] The injection pipe 40 is held in place within the ground from the time it is installed until it is withdrawn. Therefore, the condition of the surrounding ground can be checked, and the injection plant can be connected as appropriate to carry out the injection of the injection material.

[0076] The sheet pile 13 installation and removal operations can be carried out by continuously installing and removing the sheet pile 13, and by continuously injecting the injection material. However, the work is not limited to this. For example, the installation and removal operations may be carried out by repeating the step of injecting a certain amount of injection material each time the sheet pile 13 is installed to a certain height and each time it is removed. In this case, it is possible to confirm whether a certain amount of injection material has been injected at each step. Whether a certain amount of injection material has been injected can be confirmed, for example, by whether or not the injection material has leaked onto the ground surface.

[0077] In the previous explanation, the connection between the sheet pile 13's injection pipe 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 removed.

[0078] However, such switching is time-consuming and laborious. Therefore, a switching device 60, as shown in Figure 14(a), can be used to simplify the switching process. The switching device 60 includes two three-way valves 61, each having fluid inlets and outlets in three directions. Each three-way valve 61 has 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 an injection pipe 40 to which the injection material is to be supplied, and to a swivel 64 of an injection pipe 40 to which the next injection material will be supplied.

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

[0081] The three-way valve 61 has a lever 69 that can rotate approximately 90°, and its interior has, for example as shown in Figure 14(b), a cylindrical cavity 70, three connecting passages 71-73 that connect the cavity 70 to each inlet and outlet, and an L-shaped passage 74 that rotates in conjunction with the rotation of the lever 69.

[0082] As shown in Figure 14(c), when the lever 69 is in position D, that is, when the other end of the lever 69 which rotates around one end is in position D, the L-shaped passage 74 connects the connecting passage 72 to which the hose 62 is connected and the connecting passage 71 to which the hose 65 is connected, and the injection material consisting of one liquid that has flowed through the hose 62 flows to the hose 65 and is supplied to the swivel 63.

[0083] By tilting the other end of the lever 69 in the direction of arrow E, the lever 69 is rotated, and the internal L-shaped passage 74 also rotates along with the rotation of the lever 69. When the other end of the lever 69 reaches position F, the passage 74 connects the connecting passage 72 to which the hose 62 is connected and the connecting passage 73 to which the hose 66 is connected. This allows the injection material, consisting of a single liquid, that has flowed through the hose 62 to flow into the hose 66 and be supplied to the swivel 64.

[0084] When the switch is made, the injection material will no longer be supplied to swivel 63. Therefore, while the injection material is being supplied to swivel 64, the hose 65 can be removed from swivel 63, and then the hose 65 can be connected to the swivel of the next injection pipe 40, making it possible to make another switch.

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

[0086] As explained above, by adopting this method, it is possible to erect and remove buried objects while appropriately injecting the grout. Therefore, even if there are buildings or heavy objects nearby, it is possible to erect and remove buried objects while preventing the settlement of buildings or heavy objects. Furthermore, this method allows for highly efficient simultaneous extraction and filling of buried objects by efficiently pulling them out and injecting the grout.

[0087] The construction method for buried structures of the present invention has been described in detail with reference to the embodiments shown in the drawings. However, the present invention is not limited to the embodiments described above, and can be modified to include other embodiments, additions, changes, or deletions within the scope that a person skilled in the art can conceive. Any embodiment that achieves the function and effect of the present invention is included within the scope of the present invention. [Explanation of symbols]

[0088] 10... Pumping pipe 10a...Wellpoint 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 pumps 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... ​​hoses 63, 64... Swivel 67, 68... cap 69... Lever 70...Cavity 71~73…Communication path 74…Passageway

Claims

1. A method for constructing buried structures, The process involves extracting the buried object from the ground while injecting an injection material with a gel time of 5 to 120 seconds through an injection pipe, After the extraction of the specified buried object is completed, the injection pipe is withdrawn, the injection pipe is driven back into the ground in a position where the injection material has not yet hardened, and the injection material is injected from the newly driven injection pipe while the adjacent buried object that has not yet been extracted is being extracted. Construction methods for buried structures, including those mentioned above.

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

3. The construction method according to claim 1 or 2, wherein the location where the injection material has not fully hardened is the location where the buried object was removed, or the location of the ground near where the buried object was removed.

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