Ground improvement methods

Abstract

To provide a method for improving ground by forming a drainage channel simply and firmly under the ground even in a narrow place in a mountainous region by forming the drainage channel not from the slope of an embankment but from the upper surface side. [Solution] The ground improvement method of the present invention includes: (1) creating a first excavation hole 1 by rotating and inserting an auger 10 from the top surface of the ground toward the ground, and pouring drainage material 7 into the first excavation hole 1; then, (2) creating a second excavation hole 2 by inserting and rotating an auger 10 from the top surface of the ground toward the ground at a position close to the first excavation hole 1 toward the ground, and pouring drainage material 7 into the second excavation hole 2; and further, (3) digging up the boundary area 3 between the first excavation hole 1 and the second excavation hole 2 with the auger 10 to connect the first excavation hole 1 and the second excavation hole 2, and mixing the drainage materials 7 from both holes to form a drainage channel 4.

Description

[Technical field]

[0001] The present invention relates to a method for improving a ground formed by embankment, and more particularly to a method for improving a filled ground by forming a drainage channel in the embankment from the ground surface side using an auger. [Background technology]

[0002] In recent years, earthquakes have been occurring frequently in the Japanese archipelago, and roads in mountainous areas have been closed due to ground collapses caused by earthquakes. When building roads in mountainous areas, soil from land that is higher than the road is usually piled up on land that is lower than the road to build the road.

[0003] In mountain roads built in the old days, when embankments were built on low-lying land, there are many cases where the embankments were built without creating drainage channels for rainwater and groundwater to pass through. Even if drainage channels are formed in the embankments, they may not function as drainage channels because they have not been adequately maintained for many years or the amount of rainfall recorded exceeds the amount expected at the time of construction. In such roads, the embankments contain a lot of water, and when an earthquake occurs, the ground collapses and the road itself built on the embankments, as well as the embankments around the roads, may collapse.

[0004] In order to avoid such situations, in recent years, various techniques have been proposed for reinforcing the ground formed by embankments to solve drainage problems within the embankments, such as burying drainage material using casing pipes from the slope (face) of the embankment (prior document 1) or inserting new drainage pipes from the slope (prior document 2)). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-130793 A [Patent Document 2] JP 2021-152313 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the reinforcement work of drainage channels, which is performed by inserting casing pipes or drainage pipes into the embankment, the pipes must be inserted from the slope direction. In the sloped embankment on the side of the road in mountainous areas, the slope is exposed on the road surface, so when the reinforcement work of the exposed part is possible on the road, it is sometimes possible to install a drainage channel from the side wall part, which is the slope. However, generally, when inserting drainage materials such as pipes or drainage channels from the slope direction, sufficient working space is required in the slope direction, but the slope direction is inclined and the working space is small, making it difficult to set up the equipment for the work. In addition, when the ground of the embankment is relatively hard, it is necessary to apply a considerable amount of pressure to insert the pipes into the embankment, but there are problems in the construction, such as the inability to apply sufficient pressure from the slope direction.

[0007] In fact, in mountainous areas, when the road itself is built on an embankment, the slope is usually steep, making it impossible to drive pipes from the slope direction, and making it difficult to reinforce the drainage channel under the road.

[0008] In view of the above, the present invention aims to provide a ground improvement method that forms a drainage channel simply and firmly under an embankment, even in narrow areas in mountainous regions, by forming the drainage channel from the top side of the embankment rather than from the slope. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the ground improvement method of the present invention is characterized in that: (1) a first excavation hole is made by inserting and rotating an auger from the top surface of the ground toward the ground, and drainage material is poured into the first excavation hole; (2) a second excavation hole is made by inserting and rotating an auger from the top surface of the ground toward the ground at a position close to the first excavation hole, and drainage material is poured into the second excavation hole; and (3) the boundary area between the first excavation hole and the second excavation hole is excavated with the auger, thereby connecting the first excavation hole and the second excavation hole to form a drainage channel.

[0010] The method for improving ground according to the present invention is characterized in that an auger is inserted from the surface of the boundary area toward the ground and rotated to dig up the boundary area, and the two drainage materials are mixed together.

[0011] The method for improving ground according to the present invention is characterized in that the auger is reinserted into the first or second excavation hole, and the boundary area is eroded by rotating the auger while applying pressure in the direction of the boundary area, thereby mixing both drainage materials.

[0012] The method for improving ground according to the present invention is characterized in that a rust-proofed steel sheet pile having a flow path hole is buried in the ground in which the drainage channel is formed.

[0013] The ground improvement method of the present invention is characterized by burying a retaining wall consisting of a series of H-shaped steel piles that have rust-proofed treatment and flow path holes in the ground where the drainage channel is formed.

[0014] The ground improvement method according to the present invention is characterized in that the retaining wall consisting of the continuous piles is formed by using a plurality of H-shaped steel piles, each having a pair of flange portions and a web portion connecting the pair of flange portions, and is arranged alternately in a position where one H-shaped steel pile is approximately in contact with another H-shaped steel pile, the length of the flange portion of one H-shaped steel pile is shorter than the web portion of the other H-shaped steel pile and the length of the web portion is longer than the flange portion of the other H-shaped steel pile, and the flange portion of one H-shaped steel pile is arranged within the area surrounded by the flange portions and web portions of the other H-shaped steel pile so as to be approximately parallel to the web portion of the other H-shaped steel pile.

[0015] The ground improvement method according to the present invention is characterized in that the steps (1) and (2) are carried out simultaneously using a plurality of augers.

[0016] The method for improving ground according to the present invention is characterized in that sand, gravel, gravel, drainage material or a mixture of the above materials is used as the drainage material.

[0017] The method for improving ground according to the present invention is characterized in that an auger is inserted and rotated using an apparatus having an excavation capability using an auger.

[0018] The ground improvement method according to the present invention is characterized in that it uses as the device a construction machine having a boom whose tip position can be moved in three dimensions, and a rotational drive mechanism equipped with a vertical rotation shaft suspended from the tip of the boom. Effect of the Invention

[0019] In the method according to the present invention, an auger is used to drill a hole from the top of the embankment toward the ground, and then the boundary area is excavated to form a drainage channel, so that it is possible to work from the top of the embankment (above the road, if there is one) rather than from the slope of the embankment, and sufficient work space can be secured, making it possible to form a new drainage channel in the embankment even in narrow places such as mountainous regions. Also, even if the ground is somewhat solid, since work can be done from the top of the embankment (above the road, if there is one), a large load can be applied from above, and even at sites with a steep slope, the method according to the present invention makes it easy to form a drainage channel in the embankment below the road. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view illustrating an embodiment of a ground improvement method according to the present invention. [Diagram 2] FIG. 1 is a cross-sectional view illustrating an embodiment of a ground improvement method according to the present invention. [Diagram 3] FIG. 1 is a top view illustrating an embodiment of a ground improvement method according to the present invention. [Figure 4] FIG. 2 is a plan view of an auger excavating movement to explain another embodiment of the ground improvement method according to the present invention; [Diagram 5] FIG. 1 is a cross-sectional explanatory diagram of a side view and a plan view illustrating another embodiment of the ground improvement method according to the present invention. [Figure 6] FIG. 1 is a perspective explanatory diagram showing an earth retaining wall made of a series of H-shaped steel piles used in the ground improvement method according to the present invention. [Figure 7] FIG. 1 is a perspective explanatory diagram showing an example of a steel sheet pile and an H-shaped steel pile used in the ground improvement method according to the present invention. [Figure 8] FIG. 1 is a side view of an example of a device (hole digging pole vehicle) used in the ground improvement method according to the present invention. [Figure 9] FIG. 1 is a side view and a plan view illustrating an example of an auger used in a ground improvement method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The ground improvement method according to the present invention, as shown in Figures 1 to 3, includes the steps of: (1) forming a first excavation hole 1 by rotating and inserting an auger 10 from the top surface of the piled ground toward the ground, and pouring an appropriate amount of drainage material 7 into the first excavation hole 1; (2) forming a second excavation hole 2 by inserting and rotating the auger 10 from the top surface of the ground toward the ground at a position close to the first excavation hole 1 toward the ground, and pouring an appropriate amount of drainage material 7 into the second excavation hole 2; and (3) digging up the boundary area 3 between the first excavation hole 1 and the second excavation hole 2 with the auger 10 to connect the first excavation hole 1 and the second excavation hole 2, and mixing the drainage materials 7 from both holes to form a drainage channel 4.

[0022] The specific method for improving the embankment is as follows:

[0023] First, a marker 12 is placed on the ground (top surface of the embankment) of the embankment to indicate the position where the drainage channel will be formed in the embankment. The marker 12 is placed on the ground at the position where the drainage channel will be formed, and serves as a guide for forming an excavation hole using an auger according to the marking, or for proceeding with the erosion of the boundary area, and is placed, for example, by drawing a white line on the ground, scraping the soil on the ground, or, if the ground portion is an asphalt road, scraping the asphalt portion at the position where the excavation hole will be formed. However, the method is not limited to this, and any method may be used as long as the position where the drainage channel will be formed can be seen from the ground.

[0024] Next, as shown in Figures 1 and 2, the auger 10 is aligned with the mark 12, and the rotary drive mechanism 54 of the device 5 as shown in Figure 8 is driven to rotate the auger 10 while digging to a predetermined depth. After reaching the predetermined depth, the auger 10 is pulled up to the ground and then removed, thereby forming a first excavation hole 1 from the top surface of the embankment toward underground.

[0025] After the first excavation hole 1 is formed, an appropriately selected amount of drainage material 7 suitable for draining water present in the ground, such as sand, gravel, gravel, drainage material, or a mixture of the above materials, is poured into the first excavation hole 1. The amount of drainage material to be poured is adjusted appropriately depending on the shape of the excavation hole, the size of the drainage channel to be formed, etc.

[0026] Again, using device 5 or the like, auger 10 is further drilled along marker 12 at a position close to the first excavation hole 1 already formed, from the surface of the ground (top surface of the embankment) toward the ground to a predetermined depth, and after reaching the predetermined depth, auger 10 is pulled up to the ground and removed, thereby forming a second excavation hole 2 from the top surface of the embankment toward the ground.

[0027] After the second excavation hole 2 is formed, an appropriately selected amount of the aforementioned drainage material 7, which may be sand, gravel, gravel, drainage material, or a mixture of the above materials, is poured into the second excavation hole 2. Again, the amount of the drainage material poured is appropriately adjusted depending on the shape of the excavation hole, the size of the drainage channel to be formed, etc.

[0028] The first and second excavated holes 1 and 2 are excavated until they reach the position where the drainage channel 4 is to be provided in the embankment, and if the depth of the drainage channel 4 is to be constant in the embankment, the depth of the excavated holes is made uniform, whereas if the drainage channel is to have an incline in the embankment, the depth of the excavated holes can be changed. The size of the excavated holes is changed appropriately according to the width of the drainage channel to be formed, and can be adjusted by the shape of the auger, etc.

[0029] After the first and second excavated holes 1 and 2 are formed, as shown in Figures 1 to 3, the boundary area 3 between the first and second excavated holes 1 and 2 is excavated with an auger 10 to connect the first and second excavated holes 1 and 2 to form a drainage channel 4. The boundary area 3 refers to the area from the ground surface to the ground that exists between the outline of the first and second excavated holes 1 and 2.

[0030] In the method according to the present invention, it is meaningful to collapse the boundary area 3. That is, when a first excavation hole 1 is formed and a second excavation hole 2 is formed in a position close to it, if the distance is too close, the auger will interfere with the first excavation hole 1 already excavated during excavation, and the second excavation hole 2 cannot be formed in the desired position, so a certain distance must be provided. On the other hand, if the distance between the first excavation hole 1 and the second excavation hole 2 is large, the boundary area 3 between them will become a wall, and it will be impossible to form a drainage channel 4 in the depth direction in the embankment. In this respect, as a similar technology, there is a case where an auger is used to pre-dig the ground in order to bury sheet piles, steel sheet piles, piles, etc. in the ground. In this case, even if there is a wall in the boundary area 3, pressure is applied to the boundary area when burying the sheet piles, etc., and the wall will be naturally collapsed, so even if there is a certain distance, there is no problem and there is no need to treat the boundary area 3 separately. On the other hand, in one embodiment of the present invention, the drainage channel 4 can be simply provided under the embankment without burying sheet piles or the like, and in such a case, if there is no process of digging up the boundary area 3, a wall will remain in the boundary area 3, making it impossible to construct the drainage channel 4. Therefore, the present invention is characterized in that it includes a process of digging up the boundary area 3 with an auger 10.

[0031] As a method of digging up the boundary area 3 between the first excavated hole 1 and the second excavated hole 2 with the auger 10, for example, the auger 10 can be inserted and rotated from the surface (top surface of the embankment) of the boundary area 3 toward the ground to dig up the boundary area 3. Specifically, as shown in Fig. 2, using a device 5 as shown in Fig. 8 or the like, the tip of the auger 10 is set on the ground surface of the boundary area 3, and pressure is applied toward the ground while rotating the auger 10 with a rotary drive mechanism 54, thereby digging up the wall of the boundary area 3 from the top surface. The amount of pressure to be applied is appropriately adjusted depending on the thickness, hardness, etc. of the wall of the boundary area.

[0032] Also, instead of inserting the auger 10 into the surface of the boundary region 3, the auger 10 can be inserted again into the first excavated hole 1 or the second excavated hole 2, and the boundary region 3 can be collapsed by rotating the auger 10 while applying pressure obliquely downward toward the boundary region 3 (toward the excavated hole into which the auger is not inserted). In this case, the auger 10 is driven using a device 5 as shown in FIG. 8 or the like.

[0033] When the auger 10 that has excavated the boundary area 3 is pulled out, the auger 10 is slowly rotated in the reverse direction, leaving the mixed drainage material adhering to the auger 10 in the excavated hole.

[0034] Thereafter, the hole formed by the auger 10 is backfilled with soil or the like up to the top of the hole, completing the drainage channel 4.

[0035] So far, we have explained how to form two excavation holes, the first excavation hole 1 and the second excavation hole 2, and then form a drainage channel 4 by eroding the boundary area 3 with an auger 10. However, it is of course also possible to form a long drainage channel by forming multiple excavation holes and then eroding the boundary area.

[0036] For example, a further excavation hole (not shown) is formed near the above-mentioned second excavation hole 2, and then other excavation holes are formed in the same manner in the locations where the drainage channel 4 is to be provided, following the marker 12, and drainage material is poured into the excavation holes. Then, the boundary areas between the second excavation hole 2 and the adjacent excavation holes, and further between the adjacent excavation holes, are excavated with the auger 10 in sequence, so that the drainage channel 4 of the desired length can finally be formed.

[0037] In the above example, a method of using one auger has been described, but as shown in FIG. 4, a method of using a plurality of augers can also be used. For example, the auger 10 is buried to a predetermined depth using the device 5, the auger 10 is removed from the device 5, an auger 11 different from the auger 10 is connected to the device 5, and the auger 11 is buried to a predetermined depth in a position adjacent to the already buried auger 10. Thereafter, the auger 11 is removed from the device 5, the already buried auger 10 is reconnected to the device 5, and the rotary drive mechanism 54 of the device 5 is rotated to raise the auger 10 to the ground, and the auger 10 is pulled out, a drilled hole is formed, and an appropriate amount of drainage material 7 is put into the drilled hole. Next, the pulled out auger 10 is buried again in a position adjacent to the auger 11. After the auger 10 is buried again, the auger 11 is pulled out, a drilled hole is formed, and an appropriate amount of drainage material 7 is put into the drilled hole. Furthermore, the auger 11 is reburied to a predetermined depth in a position adjacent to the reburied auger 10. This process is repeated to form a plurality of excavation holes, and then the boundary areas between the excavation holes are excavated with the auger 10 to form the drainage channel 4. The same process can be carried out when three or more augers are used.

[0038] In the method using two augers described above, when burying auger 11, the top end of auger 10 protrudes above ground, so by using this as a landmark and burying it to the same depth as auger 10, the depth direction of the excavated hole can be aligned, making it easy to form a drainage channel at a constant depth. In addition, the peripheral surface of auger 10 remaining in the ground continues to press against the surface of the hole to prevent it from collapsing, forming a retaining wall, making the wall of the excavated hole less likely to collapse, and there is less collapse than with the method of digging with one auger, then immediately pulling it out and digging the next hole.

[0039] As described above, the present invention uses a method in which an auger is used to drill multiple excavation holes from above ground toward the ground, and then the boundary areas between the drilled holes are excavated, making it possible to easily form drainage channels from the top surface of the embankment (above the road, if there is one) rather than from the slope of the embankment. As a result, for example, as shown in Figure 5, the present invention makes it easy to form a network of drainage channels 4 (drainage ditches 64 at the ends) in an embankment 62 on a road 63 built on an embankment 62 facing natural ground 61.

[0040] In the present invention, as shown in Figure 5, in a road 63 built on an embankment 62 facing a natural ground 61, in order to further reinforce the embankment 62 or to reinforce the road 63 itself, steel sheet piles 8 and retaining walls 9 can be further formed not only at the position where the drainage channel 4 is formed or on the drainage channel 4 but also at any position within the embankment 62.

[0041] Specifically, the equipment 5 is used to place the steel sheet piles 8 and H-shaped steel piles 91, 92 at desired positions, which are then erected and buried by methods such as pressing in or driving. However, when the earth retaining wall 9 consisting of the steel sheet piles 8 and the continuous piles of H-shaped steel piles is provided in the embankment 62, it is necessary to devise a method for preventing the earth retaining wall 9 consisting of the steel sheet piles 8 and the continuous piles of H-shaped steel piles from impeding drainage within the embankment 62.

[0042] In order not to impede drainage in the embankment 62, it is considered to install steel sheet piles 8 and earth retaining walls 9 on the drainage channel 4 in the embankment 62 as much as possible. However, as shown in FIG. 5, there are cases where it is necessary to install them on the drainage channel 4. In this case, it is preferable to use steel sheet piles 8 and earth retaining walls 9 with structures different from those of conventional ones. Specifically, it is preferable to use steel sheet piles 8 having flow holes 85, 95 at the intersection with the drainage channel 4 or earth retaining walls 9 consisting of continuous piles of H-shaped steel piles, in order to improve drainage in the embankment. It goes without saying that the steel sheet piles 8 and earth retaining walls 9 having the flow holes 85, 95 may be installed not only on the drainage channel 4 but also in places in the embankment 62 where there is no drainage channel 4.

[0043] The steel sheet piles 8 and the earth retaining wall 9 made of continuous piles of H-shaped steel piles used in the present invention are not temporary but permanent. For example, the steel sheet piles 8 are originally used for on-site water protection work, and when the water level at the site is high, the steel sheet piles 8 are driven, and when the water protection work is completed, the temporary steel sheet piles 8 are removed. However, the steel sheet piles 8 buried in the present invention are permanently installed in the embankment 62, and are intended to protect the embankment 62 and the road 63 semi-permanently, so it is necessary to subject the steel sheet piles 8 themselves to rust prevention treatment. Therefore, the steel sheet piles 8 delivered to the site and before driving are subjected to rust prevention treatment, and then driven. The H-shaped steel piles used for the earth retaining wall 9 made of continuous piles are also subjected to rust prevention treatment in the same way before driving. As for the method of rust prevention treatment, any existing rust prevention technology may be used appropriately.

[0044] As the retaining wall 9 consisting of a series of H-shaped steel piles, for example, as shown in FIG. 6, a plurality of H-shaped steel piles each having a pair of flanges and a web connecting the pair of flanges are used, and one H-shaped steel pile 92 is alternately arranged at a position where it is approximately in contact with another H-shaped steel pile 91, and the length of the flange of one H-shaped steel pile 92 is shorter than the web of the other H-shaped steel pile 91, the length of the web of the other H-shaped steel pile 91 is longer than the flange of the other H-shaped steel pile 91, and the flange of one H-shaped steel pile 92 is arranged in an area surrounded by the flange and web of the other H-shaped steel pile 91 so as to be approximately parallel to the web of the other H-shaped steel pile 91. In this case, it is preferable to use one in which a part of the web of one H-shaped steel pile 92 is pierced using an oxyacetylene cutting machine or the like to form a flow path hole 95 at the part where it intersects with the drainage channel 4, because this makes it easier to drain. The shape, size, and position of the flow path hole 95 of the H-shaped steel pile are appropriately selected according to the situation at the site.

[0045] The steel sheet pile 8 may be a commercially available one, and then, as shown in Fig. 7(a), a part of the pile may be perforated using an oxyacetylene cutting machine or the like to form a flow passage hole 85 at the part where the pile intersects with the drainage channel 4. The shape, size, and position of the flow passage hole 85 in the steel sheet pile may be appropriately selected according to the site conditions.

[0046] As described above, the present invention utilizes a method in which an auger is used to drill multiple excavation holes from above ground toward underground, and then the boundary areas between the excavation holes are excavated, making it possible to easily form a drainage channel from the top surface of the embankment (or above the road, if there is a road), rather than from the slope of the embankment.

[0047] 8 shows the configuration of an example of the device according to the present invention used for excavation with an auger, embedding steel sheet piles and H-shaped steel piles, etc. Any machine capable of excavating with an auger can be used as the device 5, and for example, the device 5 has a power unit 52 having a boom 51 whose tip position can be moved in three dimensional directions, and a rotary drive mechanism 54 having a vertical rotary shaft suspended from the tip of the boom 51, and the auger, steel sheet pile, pile, etc. are connected to the rotary shaft 55 of the rotary drive mechanism 54.

[0048] Specifically, for example, it is a four-wheeled self-propelled truck with a power unit 52 and a rotary drive mechanism 54 mounted on the bed, and outriggers are provided near the four corners of the bed to stably hold the bed on the ground. The one shown in FIG. 8 uses a hole-digging pole-setting vehicle, but a mini-shovel, a shovel, other driving machines with leaders, vehicle-based construction machines, mobile crane construction machines, etc. can also be used, or these vehicles can be modified to be used as machines with excavation capabilities using an auger. Unlike driving machines that can only work in fixed areas with leaders, if a pole-setting vehicle with a boom is used, it is possible to set the vehicle on the road and move the boom to perform work on forming a drainage channel from the ground to the ground, even on the sloping ground on both sides of the road.

[0049] The power unit 52 may be a power unit part of a pole hole digger, a mini shovel, a shovel, a driving machine with a leader, a vehicle-type construction machine, a mobile crane construction machine, etc., which may be used as is or may be modified from these.

[0050] The rotary drive mechanism 54 is equipped with a vertical rotary shaft 55 suspended from the tip of the boom 51, and serves to rotate the auger attached below the rotary shaft, and can utilize existing technology. The boom 51 is configured to be able to move anything it lifts in three dimensions by telescoping, swinging, turning, etc. The boom 51, via the power unit 52, serves to position the auger, steel sheet piles, piles, etc.

[0051] The shape, diameter, length, material, etc. of the auger used in the present invention are appropriately selected using the ordinary knowledge of a person skilled in the art depending on the on-site conditions, the location of the drainage channel, the size of the drainage channel, the width and hardness of the boundary area, etc.

[0052] For example, as shown in Fig. 9, the auger 10 (11) is made of a steel pipe or the like, and has a pointed tip (lower end) or a steel pipe provided with a raking mechanism 17 made of an iron bar with spiral blades or the like for raking up soil generated during excavation on its outer periphery, and the outer diameter of the steel pipe can be selected as appropriate. Also, an engagement screw or pin 18 or the like is provided at the upper end of the auger, and is engaged with a rotating shaft 55 of the rotary drive mechanism.

[0053] When selecting the shape of the auger, consideration should be given to the shape that makes excavation easy, that does not produce surplus soil, and that leaves as large a hole as possible when the auger is pulled out. For example, for a shape that makes excavation easy, it is preferable to have a pointed tip (lower end) and a scraping mechanism 17 on the outer periphery. Also, the larger the scraping mechanism 17, the easier the excavation will proceed and a larger hole can be formed by the scraping mechanism 17, but more surplus soil will be produced. On the other hand, if the scraping mechanism 17 is made smaller, the amount of surplus soil will decrease, but the excavation speed will decrease and the size of the hole formed will also be smaller. Regarding the size of the steel pipe, if it is made thicker, the hole can be formed as large as possible, but the thicker the steel pipe, the more power is required to rotate and excavate. Taking into consideration the various points above, the shape of the auger is selected appropriately according to the situation. EXAMPLES

[0054] A case where the present invention is implemented using one auger with a hole digging pole installation vehicle 5 will be described. Note that two or more augers may be used, and a vehicle other than a hole digging pole installation vehicle may be used.

[0055] A positioning mark 12 is placed on the ground at the location where the drainage channel 4 is to be formed in advance, and a hole digging and post erection vehicle 5 is prepared near the mark 12. A rotary drive mechanism 54 equipped with a vertical rotary shaft 55 suspended from the tip of a boom 51 is attached to the hole digging and post erection vehicle 5.

[0056] At the start of work, the auger 10 is engaged and connected to the rotary drive mechanism 54, the boom 51 is operated, the lower end of the auger 10 is moved to directly above the excavation position according to the marker 12, the rotary drive mechanism 54 is operated, the auger 10 is rotated, excavation is started, and excavation is performed to a predetermined depth (e.g., 3 meters). Once excavation to the predetermined position is completed, the rotary drive mechanism 54 is rotated to pull the auger 10 out to the ground, and the first excavated hole 1 is formed.

[0057] After the first excavation hole 1 is formed, an appropriate amount of gravel 7 is poured as a drainage material into the first excavation hole 1 up to about halfway from the bottom, and the gravel is spread over the inside.

[0058] Again, using the hole digging pole vehicle 5, the auger 10 is moved further along the marker 12 to a position directly above the already formed first excavated hole 1, the rotary drive mechanism 54 is operated to rotate the auger 10, and excavation is started to a predetermined depth (for example, 3 meters). Once excavation to the predetermined position is completed, the rotary drive mechanism 54 is rotated to pull the auger 10 out to the ground, and the second excavated hole 2 is formed.

[0059] After the second excavation hole 2 is formed, an appropriate amount of gravel 7 is poured as a drainage material into the second excavation hole 2 up to about halfway from the bottom, and the gravel is spread over the inside.

[0060] Furthermore, using a hole digger 5, the auger 10 is moved to a position immediately above the position close to the second excavated hole 1 already formed, and another excavated hole is formed by further digging with the auger 10, and thereafter, following the markers, excavation holes are formed in the same manner in the locations where the drainage channel 4 is to be provided. After these excavation holes are formed, an appropriate amount of gravel 7 is poured as drainage material into the excavated holes about halfway from the bottom, and the gravel is spread over the entire area.

[0061] After forming the first excavation hole 1, the second excavation hole 2, and multiple adjacent excavation holes, the post hole digger 5 is used to sequentially move the auger 10 to directly above the boundary area 3 between the adjacent excavation holes that have already been formed, and the rotary drive mechanism 54 is operated to rotate the auger 10 and begin excavation. By applying pressure underground, the wall of the boundary area 3 is excavated from above, and the gravel 7, which is the drainage material for both, is mixed to form a drainage channel 4 at the desired location.

[0062] Furthermore, when driving the steel sheet pile 8 on the drainage channel in the embankment 62, a hook equipped on the post hole digger 5 arranged on the road 63 is used to lift the steel sheet pile 8 with the flow path hole 85 shown in Fig. 7(b), and the boom 51 is operated to move it to the location where the drainage channel 4 is formed using the auger, and further pressure is applied underground to press or drive the steel sheet pile 8 so that the flow path hole 85 of the steel sheet pile 8 is located on the drainage channel, and the steel sheet pile 8 is buried on the drainage channel 4 in the embankment 62. Similarly, when burying an earth retaining wall 9 consisting of a series of H-shaped steel piles, the H-shaped steel piles are pressed or driven and buried on the drainage channel 4 in the embankment 62. [Industrial Applicability]

[0063] The present invention is not limited to the above-described embodiment, and includes various modified designs within the scope of the gist of the invention. [Explanation of symbols]

[0064] 1 First drill hole 2. Second drill hole 3 Boundary area 4 Drainage channel 5 Equipment 7 Drainage materials 8 Steel sheet piles 9 Mountain retaining wall 10 Auger 11 Auger 12 Landmark 17 Raking mechanism 18 Screws or pins 51 Boom 52 Power plant 54 Rotational drive mechanism 55 Rotation axis 61 Natural ground 62 Embankment 63 Road 64 Drain 85 Flow Hole 91 Other H-shaped steel piles 92 One H-shaped steel pile 95 Flow Hole

Claims

1. (1) inserting an auger into the ground from the top surface thereof and rotating it to form a first excavation hole, and pouring drainage material into the first excavation hole; (2) inserting and rotating an auger from the top surface of the ground toward the ground at a position adjacent to the first excavation hole to form a second excavation hole, and pouring drainage material into the second excavation hole; (3) A boundary area between the first excavated hole and the second excavated hole is excavated with an auger to form a drainage channel by connecting the first excavated hole and the second excavated hole. A method for improving ground, comprising:

2. The method for improving ground according to claim 1, characterized in that an auger is inserted from the surface of the boundary area toward the ground and rotated to dig up the boundary area, and mix both drainage materials.

3. The method for improving ground according to claim 1, further comprising the steps of: inserting an auger into the first or second excavated hole again; applying pressure toward the boundary region while rotating the auger to excavate the boundary region, thereby mixing the two drainage materials.

4. 4. The method for improving ground according to claim 1, further comprising burying a rust-proofed steel sheet pile having a flow path hole in the ground where the drainage channel is formed.

5. The method for improving ground according to any one of claims 1 to 3, characterized in that a retaining wall made of a series of H-shaped steel piles having a flow path hole and treated with rust prevention is buried in the ground in which the drainage channel is provided.

6. The method for improving ground according to claim 5, characterized in that the retaining wall made of the continuous piles is formed by using a plurality of H-shaped steel piles each having a pair of flange portions and a web portion connecting the pair of flange portions, and alternately arranging one H-shaped steel pile in a position where it is approximately in contact with another H-shaped steel pile, the length of the flange portion of the one H-shaped steel pile is shorter than that of the web portion of the other H-shaped steel pile, the length of the web portion of the one H-shaped steel pile is longer than that of the flange portion of the other H-shaped steel pile, and the flange portion of the one H-shaped steel pile is arranged in a region surrounded by the flange portions and web portions of the other H-shaped steel pile so as to be approximately parallel to the web portion of the other H-shaped steel pile.

7. The method for improving ground according to claim 1, characterized in that the steps (1) and (2) are carried out simultaneously using a plurality of augers.

8. 2. The method for improving ground according to claim 1, wherein the drainage material is sand, gravel, gravel, drainage material, or a mixture of the above materials.

9. The method for improving ground according to claim 1, characterized in that the auger is inserted and rotated using a device having an excavation capability using an auger.

10. The method for improving ground according to claim 9, characterized in that the device used is a construction machine having a boom whose tip position can be moved in three dimensional directions, and a rotary drive mechanism having a vertical rotary shaft suspended from the tip of the boom.

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