JP3605725B2 - U-shaped groove - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a U-shaped groove that can be used for agricultural and industrial waterways and drainage channels, and general civil waterways and drainage channels.
[0002]
[Prior art]
The U-shaped ditch used as a side gutter or drainage for civil engineering development sites and general roads in Yamano, when buried in soft ground areas, especially in areas with slopes such as Yamano, the installation position of the U-grooves during rainfall is improper. May be stable. When rainwater is absorbed from the ground, it flows down the ground and flows downward, contacts the outer wall side of the buried U-shaped groove, and then flows along the bottom surface from the outer wall side of the U-shaped groove. It is believed that the water flows further downward and gradually erodes the soil around the U-shaped ditch together with the rising groundwater. If this situation is left unchecked, the soil around the U-groove will be gradually cut down, causing the U-groove to shift in position and causing the ground to collapse around the U-groove. The function as a water flow path may not be able to be exhibited.
On the other hand, there are conventionally known several documents relating to a U-shaped groove provided with an anti-floating material in order to prevent the U-shaped groove from floating (JP-A-61-162645, JP-A-2-39913, etc.). . In these methods, a rod body or the like is provided in a U-shaped groove as an anti-floating material, covered with soil at the time of construction, fixed and buried, or anchored in the soil.
[0003]
[Problems to be solved by the invention]
However, not only ordinary U-shaped grooves, but also U-shaped grooves provided with the above-mentioned anti-floating material, especially when buried beside slopes, in areas with a large amount of rainfall, or when the ground is soft Under bad conditions, such as when water is likely to be absorbed, the soil around the U-shaped ditch during rainfall, especially the soil that was covered to fix The potential for erosion and erosion by groundwater increases. That is, the conventional U-shaped groove has not yet reached an effective solution for preventing the erosion of the surrounding soil by water.
For this reason, a technique capable of protecting the soil around the U-shaped groove from water erosion, particularly during rainfall, and providing a U-shaped groove capable of always exerting its function in a stable state. Is desired.
[0004]
The present invention has been completed on the background of the above-described conventional technology, is a U-shaped groove made of a hard synthetic resin or a fiber-reinforced resin, forms a wall having a U-shaped cross section, and from the bottom of the wall. By forming a concave portion and a convex portion extending to the upper part of the right and left wall side portions alternately and continuously in the longitudinal direction of the U-shaped groove, a U-shaped rigid synthetic resin or fiber-reinforced resin formed into a corrugated shape is formed. A groove-shaped main body, comprising a plurality of sign marks attached to the outer surface of the left side, right side, or both left and right side walls of the main body, where a place where a groundwater inflow hole should be drilled can be visually recognized. A U-shaped groove,
The mark is a substantially conical depression corresponding to the shape of the tip of the drill, and a plurality of the mark is provided at the height position different height , U-shaped groove.
In another preferred aspect of the present invention, the marker mark is provided at a height position within a range of 1/4 to 3/4 of the height of the main body from the bottom surface of the U-shaped groove main body. U-shaped groove.
[0005]
As described above, erosion of the soil around the buried U-shaped groove is prevented by providing one or more holes as groundwater inflow holes on the left, right, or both left and right side walls of the U-shaped groove. It is possible to do. That is, rainwater that is absorbed into the ground during rainfall and originally contacts the side of the U-shaped groove and should flow toward the bottom, and groundwater whose water level has risen to the side of the U-shaped groove, are discharged from this groundwater inflow hole into the U. By allowing the water to flow into the U-shaped groove, the water around the U-shaped groove is quickly discharged, thereby preventing the erosion of the soil from the bottom of the U-shaped groove to the vicinity of the side wall by the water.
[0006]
However, if a worker drills by visual inspection without any mark at the construction site to provide a groundwater inflow hole in the U-shaped ditch, the position, especially the height position, is not necessarily constant, and the groundwater inflow It is considered that the U-shaped groove provided with the hole cannot sufficiently exhibit the original effect. The drilling point for the groundwater inflow hole cannot be determined completely arbitrarily. In some cases, it is required that the area is extremely narrow depending on the area where the U-shaped ditch is laid in a specific location and area. Because it is possible, it is difficult even for a skilled worker to drill a groundwater inflow hole at an accurate position by visual inspection without any mark. Therefore, in order to make it possible to accurately drill the target position, a marker mark on the side of the wall of the U-shaped groove, that is, a marker mark that allows the user to visually recognize the place where the groundwater inflow hole should be drilled, is provided. It becomes very important to apply. As a result, the operator can drill the target mark with the target mark, so that it is easy for the skilled worker as well as a beginner to work, and the drilling position of the groundwater inflow hole is far more than when drilling by visual measurement. Be accurate.
[0007]
During rainfall, part of the rainwater absorbed into the ground reaches a buried U-shaped ditch through a groundwater channel (water channel). In this case, if a groundwater inflow hole is formed in the side of the wall of the U-shaped groove, the groundwater that has reached the vicinity of the U-shaped groove flows into the U-shaped groove from the groundwater inflow hole. In general, since a considerable earth pressure is applied around the buried U-shaped groove, groundwater flows into the U-shaped groove vigorously. In addition, the level of underground groundwater generally fluctuates after rainfall and due to changes in temperature. Therefore, when the groundwater level rises to the wall side of the U-shaped groove, if a groundwater inflow hole is formed in the wall side of the U-shaped groove, the groundwater flows from the inflow hole into the inside of the U-shaped groove. Inflow. Since the groundwater around the U-groove can flow off through the flow path in the U-groove, the U-groove according to the present invention is provided with a groundwater inflow hole, which allows the groundwater to remove soil around the U-groove. Erosion can be effectively prevented.
Therefore, in order for this drainage function to be effectively exhibited, as shown in FIG. 1, the height position of the groundwater inflow hole, especially on the wall side of the U-shaped groove main body, is predicted by rainfall or environmental temperature change. It must be set lower than the normal groundwater level. If the height position of the groundwater inflow hole is higher than the groundwater level, it becomes difficult for groundwater to flow into the U-shaped groove (see FIG. 1). More specifically, the height position of the groundwater inflow hole, that is, the mark that is actually drilled among the mark marks that can visually confirm the drilling location, is determined by the rainfall and soil in the area where the U-shaped groove is buried. It is determined in consideration of the nature of the groundwater and the condition of the groundwater vein.
Even if the groundwater inflow hole is formed on the side of the wall of the U-shaped groove, the hole is not only relatively small, but also a considerable earth pressure is applied around the buried U-shaped groove. Therefore, there is almost no risk that water flowing in the U-shaped groove will flow out of the U-shaped groove through the groundwater inflow hole.
[0008]
The height of the groundwater level naturally differs depending on the region. Therefore, for example, it is necessary to set the height position of the groundwater inflow hole relatively high in an area where the amount of rainfall is relatively large, and to set the height position relatively low in an area where the amount of rainfall is relatively small. If the soil is clayey soil that is hardly absorbed into the ground, it is necessary to take measures such as increasing the number of groundwater inflow holes. Therefore, it is desirable that the above-mentioned marker mark is attached not only at a single height position but also at several different height positions. Note that the mark is usually provided at a plurality of locations along the longitudinal direction of the U-shaped groove at intervals of, for example, about 20 cm to 50 cm. With such a configuration, a sign mark at an appropriate height position is selected from a plurality of sign marks at different height positions in consideration of the rainfall amount, the nature of the soil, and the like in the area to be buried. An appropriate number of holes can be formed in the longitudinal direction of the groove. The range of the position of the groundwater inflow hole, that is, the position of the sign mark where the place to be drilled can be visually recognized, is such that the water flowing in the U-shaped groove during rainfall is about 1/4 of the height of the U-shaped groove. In order to prevent the water from seeping out of the groundwater inflow hole to the outside soil, the lower limit of the position of the mark is 1/1/1 of the height of the main body from the bottom of the U-shaped groove main body. It is preferable to set it to about 4, and even in areas where the amount of rainfall is large and the ground is soft, the height at which the groundwater level and the rainwater absorbed into the ground contact the U-shaped groove wall side is U-shaped. Since it is considered that it is unlikely that the height of the mark rises to ３ or more of the height of the groove, the upper limit of the position of the mark is set to about ／ of the height of the main body from the bottom surface of the U-shaped groove main body. Is preferred.
[0009]
Further, the U-shaped groove main body alternately and continuously forms, in the longitudinal direction of the U-shaped groove, concave and convex portions extending from the bottom of the U-shaped groove to the upper portions of the right and left side walls, thereby forming a waveform. When it is molded, when a mark is placed on the outer surface of the concave portion so that the position of the groundwater inflow hole can be visually recognized, or when groundwater flows into the rib protruding from the outer surface of the wall side of the U-shaped groove. In the case where a mark that allows the position of the hole to be visually recognized is attached, the mark that allows the position of the groundwater inflow hole to be visually recognized is perpendicular to the direction of the water flow flowing from the upstream side to the downstream side in the U-shaped groove. It is preferable that the groundwater inflow hole can be formed so as to intersect at an acute angle. When the groundwater inflow hole can be formed so as to intersect at an obtuse angle with respect to the direction of the water flow, when the water level in the U-shaped groove reaches the height of the groundwater inflow hole, the water flows into the U-shaped groove. This is because the water tends to ooze out of the groundwater inflow hole into the external soil by riding on the flow of water.
[0010]
The outer surface of the left, right, or left and right wall side portions of the U-shaped groove main body is preferable as a location where the mark is attached in terms of ease of drilling work before embedding. May be attached to the inner surface as needed if there is no serious problem. Preferably, the marker mark is selected from the group consisting of a substantially conical depression, a narrow groove, a fine line cut, a satin-finished surface, and a colored mark. These forms may be arbitrarily selected, but should be confirmed visually, and therefore, those that are easy to stand out are preferable. For example, if the color of the colored mark is yellow, green, red, etc., the shape is circular, triangular, square, etc., if the pattern is a roughened satin pattern, or a depression corresponding to the tip of the drill It may be. The mark can be easily applied by painting, polishing, processing the corresponding mold surface, or the like.
[0011]
The U-shaped groove of the present invention provided with a sign mark that allows the user to visually recognize the place where the groundwater inflow hole is to be drilled can be applied not only to construction on an inclined ground but also to burial on a flat ground. For example, when constructing on flat ground, use the mark as it is without drilling it.On the other hand, when constructing on an inclined surface, drill a mark at an appropriate position as the target as described above and make the groundwater inflow hole Applications can be used properly according to the situation at the site. Examples of the material of the U-shaped groove provided with a mark for visually confirming the place where the groundwater inflow hole of the present invention is to be formed include polyethylene resin, polyvinyl chloride, polypropylene, polyethylene terephthalate, polyamide, and polyphenylene sulfide. Hard synthetic resins and fiber reinforced resins such as FRP and FRTP are desirable. As the shape of the U-shaped groove main body, in addition to the original U-shape, a shape that rises vertically from the bottom of the wall or a shape that rises slightly outward toward the top may be used. The U-shaped groove of the present invention can be formed by blow molding, rotational molding or the like. Also, the U-shaped groove may be perforated for a groundwater inflow hole, and a conventional U-shaped groove floating prevention material may be used at the same time. Thereby, it can be expected that the soil around the buried U-shaped groove is prevented from being eroded by water and also has the effect of preventing floating.
[0012]
【Example】
The present invention will be described in more detail with reference to the drawings. The following examples are not intended to limit the invention.
[0013]
Embodiment 1 FIG.
One embodiment of the U-shaped groove of the present invention is shown in FIGS. FIG. 2 is a view for explaining the U-shaped groove 1 of the present embodiment, FIG. 3 is a plan view of the U-shaped groove 1 shown in FIG. 2, and FIG. 4 is a side view thereof. The U-shaped groove 1 is made of various products having dimensional standards of, for example, widths of 180 mm, 240 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, and 1000 mm, all of which are of a straight wall type.
As is clear from FIGS. 2 to 4, in the present embodiment, the U-shaped groove main body 2 made of polyethylene resin has a shape in which the left and right side walls 4, 4 respectively stand upright from the wall bottom 3. Concave portions 5... And convex portions 6... Extending from the bottom portion 3 to the upper portions of the left and right wall side portions 4 and 4 are alternately and continuously formed in the longitudinal direction of the U-shaped groove 1 to form a corrugated shape. ing.
As shown in FIG. 2 and FIG. 4, the recessed portions 5 extending to the upper part of the right and left wall side portions 4 of the U-shaped groove main body and the rib portions 15 projecting outwardly are provided with a groundwater inflow hole. A marker mark 12 that allows the user to visually recognize a location to be set is formed and attached to a recess having a shape corresponding to the shape of the tip of the drill. The marker mark is configured such that the groundwater inflow hole 13 can be formed at a right angle or an acute angle with respect to the direction of the water flow flowing from the upstream side to the downstream side in the U-shaped groove. After piercing and embedding, the water flowing in the U-shaped groove main body is effectively prevented from oozing out of the groundwater inflow hole to the outside soil by riding the flow. In addition, since the sign marks are provided at a plurality of different height positions, the sign marks at several different height positions are taken into account in consideration of the rainfall amount, soil properties, and the like in the buried area. It is possible to select a marker mark at an appropriate height from the marks, and to drill an appropriate number of groundwater inflow holes in the longitudinal direction of the U-shaped groove.
Further, as shown in FIGS. 2 and 4, an anti-floating material support groove portion 31 is formed at the bottom of the U-shaped groove main body 2, and a rectangular angle material 30 longer than the width of the U-shaped groove 1 is inserted as the anti-floating material. Has been supported. Thereby, in addition to the effect of preventing erosion of the soil around the U-shaped groove of the present invention, the effect of preventing the U-shaped groove from floating can be expected.
FIG. 6 is a cross-sectional view of the ridge portion 6 of the U-shaped groove main body 2 taken along the line AA in FIG. 3. As is clear from this figure, the ridge portions 6. , And extend to the upper ends of the left and right wall side portions 4 and 4 to form bridging material receiving portions 8 and 8.
FIG. 7 is a cross-sectional view of the concave portion 5 of the U-shaped groove main body 2 taken along the line BB in FIG. 3. As is clear from FIG. 7, the concave portions 5. At the upper part of the wall 4, it extends to the upper ends of the left and right wall side parts 4, 4 while taking inwardly curved shapes 5 a, and extends outward from the upper ends to be connected to the bridging member receiving parts 8, 8. . This shape further increases the rigidity against earth pressure from various load directions applied to the vicinity of the upper portions of the left and right wall side portions 4 and 4 which are the weak portions of the U-shaped groove main body 2 after the U-shaped groove 1 is laid. To give.
As shown in FIGS. 2 and 3, the left and right bridging member receiving portions 8, 8 are paired with holes 8a at regular intervals in the longitudinal direction at the upper positions of the ridge portions 6. As shown in FIGS. 11 and 12, a resin-made substantially L-shaped cross section 7A having holes 7a and 7a formed at both ends shown in FIG. 10 can be attached to this portion as shown in FIGS. it can. In this embodiment, since the U-shaped groove main body 2 itself has a portion for receiving the bridging material, other auxiliary members for disposing the bridging material are not required when using the bridging material.
The angle member 7A having a substantially L-shaped cross section is formed by aligning the holes 7a, 7a formed at both ends thereof with the holes 8a, 8a of the bridging material receiving portion, and attaching the rivets 9 to the U-shaped groove. It can be fixed to the upper part of the main body 2. The rivet 9 has a shape shown in FIG. 13 and is made of a resin made of the same material as that of the U-shaped groove main body 2, but other hard synthetic resin or fiber reinforced resin can also be used. The use of the rivets 9 makes it very easy to attach the bridging material as compared with the case of using screws, bolts, nuts and the like.
The surface of the substantially L-shaped angled member 7A shown in FIG. 10 (c) having no hole 7a is notched at both ends so that the surface (FIG. 10 (b)) has the hole 7a. Designed short. Therefore, the surface without the hole 7a (FIG. 10 (c)) can be attached downward into the U-shaped groove main body 2.
The U-shaped groove 1 of the present invention can obtain higher rigidity against earth pressure applied to both wall side portions 4 and 4 of the U-shaped groove main body 2 due to the horizontal suspension of the angle member 7A having a substantially L-shaped cross section, The deformation of the U-shaped groove main body 2 can be prevented. Moreover, since the angle member 7A having a substantially L-shaped cross section is attached without protruding upward, the safety of the worker can be further secured when the U-shaped groove is buried.
In addition to the angle member 7A having a substantially L-shaped cross section, an angle member 7B having an L-shaped cross section shown in FIG. 14 can be used as another bridging material. As shown in FIGS. 3, 15, and 16, the angle member 7B having an L-shaped cross section is configured so that both ends thereof are pushed open on both sides of the U-shaped groove wall side portions 4 and 4, and the U-shaped groove main body wall is opened. It can be mounted by simply fitting it into the receiving recesses 9, 9 provided in the side parts 4, 4, and does not require fixing tools such as screws, bolts, nuts, rivets, etc., so that mounting can proceed quickly. . Further, since the angle member 7B having the L-shaped cross section is used with the L-shaped bent portion having the mountain side facing upward, it does not protrude from the upper surface of the U-shaped groove after being attached, so that the safety of the worker can be further secured. By using the angle material A and the angle material B in a horizontal manner, the U-shaped groove 1 can obtain higher rigidity against earth pressure applied to both side walls 4 and 4 of the U-shaped groove main body 2. , U-shaped groove main body 2 can be prevented from being deformed.
The U-shaped groove 1 of the present embodiment is made of the same resin as the U-shaped groove main body 2 as an anti-floating material below the bottom 3 of the wall of the U-shaped groove main body 2 as shown in FIG. An angle member 30 having an L-shaped cross section longer than the width is provided.
As shown in detail in FIG. 9, the U-shaped groove main body 2 is configured such that a concave ridge portion 5 of a wall bottom portion 3 at a central portion thereof and two convex ridge portions 6, 6 adjacent to both sides thereof are a floating angle angle material. 30 are formed so as to form the anti-floating material support groove 31 having a structure capable of sandwiching both angle surface portions of the anti-floating member 30. The floating prevention angle angle member 30 is inserted into the groove 31 below the U-shaped groove main body wall bottom 3 from one side to the opposite side, and protrudes outward from both the wall side parts 4 and 4 of the U-shaped groove main body 2. It is installed to do. Therefore, there is no need for screws, bolts and nuts, or fixing tools such as rivets for attaching the floating prevention angle material 30 to the U-shaped groove main body 2. The mounting structure of the anti-floating angle material 30 has a very simple configuration. Therefore, no processing is required after the U-shaped groove main body 2 of the present invention is formed, and the work of attaching the floating prevention member is very simple.
As shown in FIGS. 2 to 4, the U-shaped groove main body 2 of the present invention described in the above embodiment is also provided with a recessed portion at a certain interval from the slightly lower portions of the left and right wall side portions 4, 4. The rib portions 15 projecting outward over the projecting portions 5 and the projecting ridge portions 6 are provided to further increase the rigidity of the U-shaped groove main body 2. The ribs 15 also project outward from the U-shaped groove wall side parts 4 and 4 when buried in the soil, where sediment accumulates and the load is applied. Therefore, the floating of the U-shaped groove main body 2 is prevented.
Further, as shown in FIGS. 3 and 4, one end of the U-shaped groove main body 2 of the present embodiment is an external fitting connection portion 2a whose inner wall is designed to be slightly larger than other portions. The other U-shaped groove main body 2 is designed so that the other end portion can be connected to the other U-shaped groove main body 2 as an inner fitting connection portion 2b. When connecting two U-shaped groove main bodies, the outer fitting connection portion 2a is fitted so as to cover the inner fitting connection portion 2b including the rib portion 15. In addition, in the connection method, in order to minimize water leakage at the connection part, the direction of water flow is from the inner fitting connection part 2b of the U-shaped groove body 2 to the outer fitting connection part 2a of the other U-shaped groove body 2. It is preferable that the connection be made as follows.
[0014]
As described above, the U-shaped groove of the present invention has a shape of a drill tip portion on the outer surface of the left, right, or both left and right wall side portions in which a place where a groundwater inflow hole should be drilled can be visually recognized. It is provided with a corresponding mark mark made of a corresponding substantially conical depression . Therefore, since the operator can drill the mark at the target, it is easy for the skilled person as well as a beginner to perform the drilling operation using the drill , and moreover, the groundwater inflow hole is more easily than when the drilling is performed by visual inspection. The height accuracy of the drilling position is much more accurate. In addition, by drilling the groundwater inflow hole, the erosion of the soil around the U-shaped groove by the water that penetrates into the ground during rainfall and the rising groundwater level is prevented, and the U-shaped groove always performs its function in a stable state. It becomes possible. Further, the sign mark is attached not only at a single height position but also at different height positions, so that it is appropriate in consideration of a rainfall amount, a property of soil, etc. in an area where the U-shaped groove is buried. It is possible to select and drill a mark at an appropriate height position. Further, the U-shaped groove main body is formed into a waveform by alternately forming the concave portions and the convex portions extending from the bottom of the wall to the upper portions of the left and right wall side portions in the longitudinal direction of the U-shaped groove. In the case where the sign mark is provided on the outer surface of the concave streak portion on the upstream side with respect to the direction of the water flow flowing in the U-shaped groove, the U-shaped groove main body is also provided. In the case where an outwardly protruding rib portion is provided on the outer surface of the left and right wall side portions, the marker mark is located on the upstream portion of the rib portion, that is, in the U-shaped groove, from the upstream side to the downstream side. With respect to the direction of the water flow flowing to the side, the water level in the U-shaped groove is set at the height position of the groundwater inflow hole by being provided at a position where the groundwater inflow hole can be formed so as to intersect at a right angle or an acute angle with the direction of the water flow flowing to the And the water rides on the flow of water in the U-shaped ditch, It is possible to effectively prevent the oozing from the inlet to the outside soil. Further, since the sign mark is provided in a conspicuous shape such as a substantially conical depression , a worker can easily confirm the drilling position visually and can easily perform the work of drilling the groundwater inflow hole.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the positional relationship between a water level in a U-shaped groove, a groundwater level, and a groundwater inflow hole.
FIG. 2 is a diagram illustrating one embodiment of a U-shaped groove of the present invention.
FIG. 3 is a plan view of a U-shaped groove showing one embodiment of the U-shaped groove of the present invention.
FIG. 4 is a side view of the U-shaped groove shown in FIG.
FIG. 5 is an enlarged view of a portion C in FIG. 3;
FIG. 6 is a sectional view of a protruding portion of the U-shaped groove main body cut along the line AA in FIG. 3;
FIG. 7 is a cross-sectional view of a concave portion of the U-shaped groove main body cut along a line BB in FIG. 3;
8A and 8B are a plan view (a) and a front view (b) of a square angle member as a floating prevention member of a U-shaped groove according to the present invention.
FIG. 9 is a view showing a state in which the square angle member of FIG. 8 is inserted into a floating prevention member supporting groove at the bottom of the U-shaped groove main body wall.
FIG. 10 is a plan view (a), a front view (b), and a side view (c) of a substantially L-shaped cross-section angle material serving as a bridging material that extends horizontally in a U-shaped groove according to the present invention.
11 is a partial view from above showing a state in which the angle member of FIG. 10 is bridged in the bridge member receiving portion of the U-shaped groove main body.
FIG. 12 is a sectional view taken along line CC of FIG. 11;
FIG. 13 is a plan view (a) and a front view (b) of a rivet for fixing a corner angle member.
FIGS. 14A and 14B are a front view (a) and a plan view (b) of an L-shaped cross-section angle member as a bridging member transversely extending in a U-shaped groove of the present invention.
15 is a partial view showing a state where the angle member shown in FIG. 14 is fitted into the receiving recess of the U-shaped groove main body as viewed from above.
FIG. 16 is a sectional view taken along line DD of FIG. 15;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 U-shaped groove 2 U-shaped groove main body 3 Wall bottom part 4 Wall side part 5 Concave part 5a Inwardly curved shape 6 Convex part 7A Cross-section substantially L-shaped angle material 7B Cross-section L-shaped angle material 8 Bridge material receiving part 9 Rivets 10 Receiving recess 12 Marking mark 13 for visually recognizing a place where a groundwater inflow hole should be drilled 13 Groundwater inflow hole 15 Rib portion 20 Reinforcement material 30 Floating prevention angle angle material 31 Floating prevention material support groove

Claims (2)

A U-shaped groove made of a hard synthetic resin or a fiber reinforced resin, forming a wall having a U-shaped cross section, and alternately forming a concave portion and a convex portion extending from the bottom of the wall to the upper portion of the left and right wall side portions. The U-shaped groove is formed continuously in the longitudinal direction of the U-shaped groove, so that the U-shaped groove body formed of a hard synthetic resin or a fiber-reinforced resin is formed into a corrugated shape, and the outside of the left, right, or both left and right wall sides of the main body. A U-shaped groove provided with a plurality of sign marks attached to the surface and capable of visually recognizing a place where a groundwater inflow hole is to be formed,
The mark is a substantially conical depression corresponding to the shape of the tip of the drill, and a plurality of the mark is provided at the height position different height, U-shaped groove. 2. The U-shape according to claim 1, wherein the mark is provided at a height within a range of 1/4 to 3/4 of a height of the U-shaped groove main body from a bottom surface of the U-shaped groove main body. groove.

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