JP4498047B2 - Reinforcement method for ground and / or underground objects - Google Patents

Description

  The present invention temporarily fixes a geogrid embedded in excavated ground for the purpose of reinforcing the ground or reinforcing the underground buried object to maintain the buried shape during the buried construction period, and backfill the soil material. The present invention relates to a temporary pile to be pulled out and a method for reinforcing a ground and / or an underground object using the pile. In particular, the provision of a geogrid used to prevent ground reinforcement of soft ground, or uneven subsidence of buried pipes in soft ground, high groundwater level, or floating of buried pipes due to ground liquefaction during an earthquake. Relating to retained piles.

  A lightweight and strong geogrid is a useful civil engineering material that can be used to reinforce, fix, or strengthen the ground. For example, when constructing a built-up structure on a foundation ground or surface foundation where the bearing capacity is insufficient, the soil of the surface layer is discharged, and high-quality soil or cement-based solidified material is mixed into the mountain sand instead of the discharged soil. A method of strengthening the ground by replacing it with soil is known. When the lower part of the improved ground obtained by this construction method is soft, there is a disadvantage that ground subsidence easily occurs due to an increase in weight due to the ground improvement. For this reason, a construction method for reducing the weight by replacing a soft portion of the ground with light soil is also known. However, this method has a limit in ground strength, and there is a risk that the built structure will be damaged by the buoyancy generated based on the fluctuation of the water level in the ground. As a construction method for avoiding this, it is effective to dispose a lightweight structure material, for example, a reinforcing structure in which a lightweight aggregate is wrapped with a geogrid, on a ground foundation to be reinforced.

  Conventionally, PVC pipes and ceramic pipes having a diameter of about 150 to 450 mm have been used in sewage pollution pipe burying work. In this case, in order to avoid damage to the pipe, sandy soil is used for backfilling around the pipe, and a crushed stone foundation with good drainage performance is used in the lower part, especially in soft ground. In the crushed stone foundation, it was necessary to provide a ladder shell foundation to prevent uneven settlement. However, in recent years, ribbed PVC pipes with excellent damage resistance and light weight have become widespread, making it possible to use crushed stone foundations that do not have problems with sand foundation runoff in soft ground, and excavation depth of the foundation part. Although it was possible to reduce the size of the ladder, ladder ladders were still necessary to prevent uneven settlement. However, by placing a geogrid on the foundation ground instead of the ladder trunk, placing a crushed stone and a tubular body above this, surrounding at least a part of the crushed stone layer, and making it an embedded structure that integrates, It became possible to prevent the uneven settlement of the tubular body.

  Moreover, in the buried pipes for gas, power cable, water supply, agricultural water, etc., a plurality of pipes having a larger diameter than those described above, for example, a 100 to 400 cm diameter tubular body may be buried. In this case, it is necessary to dig a large amount of the ground, especially in the ground with high groundwater level, or in the event of earthquake liquefaction, the tubular body is buried deeply to resist the floating of the tubular body. It was necessary to secure a large amount of earth covering. For this reason, excavation of buried trenches requires excavation and transportation of a large amount of earth and sand, which has the problem that the construction cost increases and the construction period is prolonged.

  In order to improve the above drawbacks, attempts have been made to improve the efficiency of burying work by taking measures to prevent the tubular body from rising and burying the tubular body in a shallow groove. For example, prior to placing one or a plurality of tubular bodies in the excavation groove and backfilling with soil material, it is effective to lay the geogrid so as to cover the tubular body and the excavation groove with the geogrid. The body is prevented from rising and the shallow burial method is possible.

  In the reinforcement method of the ground and / or underground buried object using the geogrid as described above, the geogrid is laid so as to form a U-shaped portion consisting of at least a bottom surface portion and a rising portion, on which A method of backfilling the soil material is employed, and a reinforcing effect is exhibited by constructing a structure that three-dimensionally surrounds part or all of the soil material by a geogrid. That is, in each of the above-described examples, the geogrid is bent at a right angle at the side of the excavation groove side wall, and in the example of laying so as to cover the tubular body, it reaches from the foundation ground portion to the covering portion of the upper surface of the tubular body. At the rising part, the geogrid is bent at a right angle. However, since the geogrid is poor in sustainability, it is difficult to maintain a desired bending angle when the soil material is backfilled. As a result, the back of the upright portion of the geogrid may not be completely filled with soil material, creating cavities, and it is difficult to form a desired surrounding structure using geogrid for the soil material or tubular body. It was.

  Accordingly, an object of the present invention is to maintain the geogrid in a predetermined shape during the backfilling period and then pull it out in order to make full use of the performance of the geogrid in the ground and / or underground buried reinforcement method as described above. It is to provide a pile for temporary anchoring. The present invention also provides geogrid laying and use of such temporary anchoring piles, which are excellent in workability, strengthen the ground, or reinforce and fix the underground buried object and / or reinforce the ground and / or underground buried object. To provide a construction method.

  According to the present invention, a geogrid is laid on the excavated ground so as to form a U-shaped portion composed of a bottom surface portion and a rising portion, and the soil material is sprinkled into the U-shaped portion so that a part of the soil material is formed. Alternatively, in the ground and / or underground buried reinforcement method for constructing a structure that surrounds the whole three-dimensionally, in the vicinity of the rising portion of the bottom of the geogrid, the temporary piles are buried in the excavated ground so as to be buried to the vicinity of the horizontal streaks. The geogrid is fixed on the excavated ground by the transverse bars, and then the soil material is spun out to a height near the hook portion, and then the temporary pile is pulled out to reinforce the ground and / or underground buried object Construction methods are provided.

  The pile for temporary anchoring of the present invention is a geogrid temporary pile for underground burying composed of a rod-shaped body having a hook portion at the tip and a horizontal stripe at the middle portion. The hook portion preferably has a U-shaped tip portion and a tip downward.

  According to the preferred embodiment of the reinforcing method, it is preferable to use a coarse filler such as crushed stone or gravelly soil as the soil material in consideration of the reinforcing effect and the pullability of the temporary pile. In general, after the temporary pile is pulled out, the construction is completed by adding the same or different soil material.

  According to the preferred embodiment of the reinforcing method, it can also be used for embedding a tubular body. At this time, at least a part of the tubular body is preferably disposed so as to be located within the U-shaped portion of the geogrid. Moreover, in construction on soft ground, it is preferable to backfill with the coarse-grained soil material as described above, particularly crushed stone, up to the vicinity of the upper portion of the tubular body.

  According to another preferred embodiment of the present invention, the present invention is applied to an embedment work of one or a plurality of tubular bodies, and after laying the tubular body, the geogrid is covered with an upper portion of the tubular body, and the tubular body. This method is applied to a method of laying so as to form a U-shaped portion between the tubular body and the excavated ground side wall or between the tubular body and the excavated ground side wall and between the tubular bodies. In this aspect, it is preferable to provide a semicircular groove for laying the tubular body in advance on the excavated ground and place the tubular body thereon.

  In the above tubular body embedding method, the geogrid can be laid continuously in the longitudinal direction of the tubular body or intermittently in the longitudinal direction of the tubular body.

  According to the present invention, when a geogrid is buried underground, it is excellent in safety and geogrid shape maintainability when used for strengthening the ground, or for strengthening or fixing an underground buried object, and soil quality. It is possible to provide a temporary anchoring pile excellent in pullability after material backfilling.

  According to the present invention, geogrits can be laid in a desired structure with good workability, and an excellent ground reinforcement structure or a structure for fixing and holding underground objects can be constructed. In particular, it is effective for the formation of reinforcement foundations in soft ground, and is useful for the formation of reinforcement foundations for overlay structures such as embankments, concrete retaining walls, and box culverts. In addition, it can be suitably used for the method of burying tubular bodies that are excellent in preventing the underground pipe from floating due to the uneven settlement of the buried pipe in soft ground, the ground with high groundwater level, or the liquefaction phenomenon of the ground when an earthquake occurs. .

  As shown in FIG. 4, the underground laying geogrid temporary pile 11 of the present invention comprises a rod-like body 14 having a hook portion 12 at the tip and a horizontal bar 13 at the middle portion. The temporary pile 11 is driven into the ground after the geogrid is laid at a predetermined position, and the horizontal stripe 13 suppresses the geogrid and the upper part from the horizontal stripe suppresses the deformation of the rising portion of the geogrid. Thus, the shape of the geogrid is fixed. After placing the temporary pile, it is backfilled with soil material to a position lower than the height of the hook, and after the geogrid is embedded in a predetermined shape, the temporary pile is pulled out using the hook 12 and finishes its role. is there.

  The geogrid for underground laying is laid in the excavated ground so as to form at least a U-shaped part consisting of a bottom surface part and a rising part, and at least a part of the soil material is refilled by refilling the soil material thereon. By taking a structure that surrounds three-dimensionally, a reinforcing effect is exhibited. On the geogrid, an underground object such as a tubular body may be laid together with the soil material, and at this time, at least a part of the tubular body is three-dimensionally surrounded by the geogrid together with the soil material. Can be taken. The temporary pile is placed in the vicinity of the rising portion of the bottom portion of the geogrid.

  As the geogrid used for the above purpose, those having high rigidity, high strength, excellent weather resistance, water resistance, chemical resistance, light weight, workability and the like are preferable. From such a point of view, it is preferable to use a stretched plastic network. Particularly, a perforated sheet is produced from a polyolefin such as polyethylene or polypropylene containing a filler such as carbon black, and this is uniaxial or biaxial. It is preferable to use a network produced by stretching on the shaft. FIG. 1 is a partial perspective view of a uniaxially stretched geogrid 31, and FIG. 2 is a partial perspective view of a biaxially stretched geogrid 32. As such a uniaxial or biaxially stretched polyolefin geogrid, for example, one sold by Mitsui Chemicals Co., Ltd. under the trade name Tensor (registered trademark) is available on the market.

  Hereinafter, an example of a ground and / or underground buried reinforcement method using the temporary pile according to the present invention will be described with reference to the drawings. FIG. 3 shows a geological material in which a geogrid is laid in a U-shape on the foundation ground and along the groove side wall in the excavation groove, a crushed stone layer is provided thereon, and a tubular body is further placed thereon. It is sectional drawing which shows the embedding structure of the tubular body obtained by the construction method which backfills. This construction method is preferably applied to a tubular body having a relatively small diameter, for example, a tubular body having a diameter of about 100 to 900 mm. A normal straight pipe can be used as the tubular body, but it is particularly preferable to use a ribbed pipe excellent in light weight and damage resistance. Moreover, as a soil material used for backfilling, 1 type or 2 or more types, such as fine-grained soil material, such as sandy soil, coarse-grained soil material, such as gravel soil, crushed stone, can be mentioned, It is not always necessary to form a single layer, and a plurality of layers having different soil properties can be provided in the height direction for backfilling. In particular, in construction on soft ground, it is preferable to use a crushed stone layer up to the vicinity of the upper part of the tubular body, and to provide a sandy layer or a plurality of layers consisting of a sandy layer and a crushed stone layer thereon. Hereinafter, it will be described in detail with reference to the drawings.

  In FIG. 3, a geogrid 3 is laid in a U-shape on the foundation ground 2 of the excavation groove 1 and along the side grooves 4a and 4b provided along the sheet pile 21 driven into the paved road 10, and a crushed stone is formed thereon. After the layer 5 is provided, the tubular body 6 is placed, backfilled with the crushed stone 22 up to the vicinity of the upper portion of the tubular body 6, then backfilled with the sandy soil 7 and the crushed stone 8, and further paved with a two-layer structure thereon 9a and 9b are made.

  In this construction method, it is preferable to use a biaxially stretched geogrid having a mesh size of about 1 to 10 cm on one side and having a small difference in strength between the vertical direction and the horizontal direction. The geogrid can be laid continuously or intermittently in the longitudinal direction of the tubular body and the excavation groove, but is preferably laid continuously. In that case, it is preferable to use a plurality of geogrids connected by arbitrary means so that adjacent end portions overlap each other. Further, the laying height of the geogrid along the side wall grooves 4a and 4b is, for example, about 5 to 50 cm.

  In this embodiment, after the geogrid 3 (31, 32) is laid on the foundation ground 2 and along the side wall grooves 4a and 4b, the temporary pile 11 having the hook portion 12 at the above-described tip and the horizontal stripe 13 at the intermediate portion. The geogrid bend is maintained at a right angle by fixing the geogrid by hitting. As the temporary pile 11, it is preferable to use an inexpensive metal one. For repeated use or when left in the ground, there is a risk that the corrosion may promote corrosion of the tubular body. 12 is provided so that it can be pulled out after the soil material is backfilled. By making the hook portion 12 of the temporary holding pile into an inverted U-shape and having its tip faced downward, it is easy to pull out, and it is possible to avoid a stab trouble of an operator in the operation in the groove, and safety is ensured. Further, since the horizontal bars 13 of the temporary pile 11 are for pressing and fixing the meshes of the geogrid, it is preferable that they have at least a length equal to or greater than the pitch between the meshes of the geogrid, considering the pressing effect and ease of pulling out. Then you can decide the length. Further, since the temporary pile 11 is driven into the foundation ground up to the horizontal bar 13, the mounting position of the horizontal bar 13 may be set so as to maintain the driving stability of the temporary pile. For example, the temporary pile 11 Is about 10 to 100 cm from the lower end. Moreover, in order to maintain the upright stability of the geogrid along the side groove, the height above the horizontal bar 13 of the temporary pile 11 is preferably substantially the same as the laying height of the geogrid, for example, about 5 to 50 cm. .

  3, the details of the portion where the temporary pile 11 is driven in the vicinity of the side grooves 4a and 4b of the excavation groove 1 (for example, the portion shown in FIG. 3A) and the geogrid 32 is fixed are shown in FIGS. FIG. 5 is a cross-sectional view showing a driving situation of the temporary pile 11, and FIG. 6 is a front view. 5 and 6, the temporary pile 11 is driven into the foundation ground 2 immediately before the upright portion of the square mesh geogrid 32 bent at a right angle in the side groove 4 a, and the horizontal stripes 13 are meshed with the mesh of the geogrid 32. The geogrid is fixed while maintaining a right angle by pressing down and suppressing the deformation of the upstanding geogrid by the vertical stripes 14. The temporary pile 11 is driven along the longitudinal direction of the excavation groove at predetermined intervals, thereby maintaining the right angle of the geogrid along the longitudinal direction.

  After the temporary pile 11 is driven, the crushed stone layer 5 is provided on the geogrid. The laying height of the crushed stone layer 5 is preferably at least 5 cm, particularly 10 cm or more from the viewpoint of preventing the uneven settlement of the tubular body, but is preferably about 30 cm or less from the viewpoint of economy. Further, the height of the geogrid along the side groove is desirably laid at least higher than the height of the crushed stone layer in order to hold and fix the crushed stone layer 5 integrally.

  After the crushed stone layer 5 is provided, the tubular body 6 is placed and backfilled with a soil material. In the backfilling of the earth material, the role of the temporary pile 11 is finished when it reaches the vicinity of the height of the hook portion 12 of the temporary pile 11, so that the corrosion of the tubular body is prevented for reuse. Pulled out for. In FIG. 3, the crushed stone layer 22 is formed up to the vicinity of the upper height of the tubular body, and the sand excavated soil is further refilled thereon to form the sandy soil layer 7 and the crushed stone layer 8. To do. Next, after the sheet pile 21 is pulled out, the pavement layers 9b and 9a are formed by two steps of pavement work, and the tubular body burying work is completed.

  As another preferred specific example of using the underground underground geogrid temporary pile of the present invention, after placing one or more tubular bodies in the excavation groove, the geogrid covers the tubular body and the foundation ground, and then A method of backfilling with soil material can be mentioned. This method is suitable for embedding a large-diameter tubular body, for example, a tubular body having a diameter of about 100 to 400 cm. In this case, it is desirable to provide a semicircular groove for laying a tubular body in advance on the foundation ground in the excavation groove.

  FIG. 7 is a cross-sectional view showing a method for embedding two tubular bodies using a uniaxially stretched geogrid 31 in the excavation groove. Two semicircular grooves for placing the tubular body are provided in parallel on the foundation ground 16 in the excavation groove 15, and the tubular bodies 17a and 17b are placed. Next, the geogrid 31 is laid along the side wall 18, the foundation ground 16, the upper part of the tubular body 17 a, the foundation ground 16, the upper part of the tubular body 17 b, the foundation ground 16 and the sidewall 19. At this time, the geogrid 31 forms U-shaped portions between the side wall 18 and the tubular body 17a, between the tubular body 17a and the tubular body 17b, and between the tubular body 17b and the side wall 19, respectively. A temporary pile 23 is placed in the vicinity of the rising portion of the bottom surface of each U-shaped part, and the geogrid is firmly fixed on the foundation ground by pressing down the mesh of the geogrid by the horizontal streak. Yes. This makes it possible to maintain the geogrid's U-shape during the backfill period of the soil material, and it can form an excellent reinforcement structure of the geogrid, and without any voids, It becomes possible to backfill the material evenly. A sufficient effect can be obtained by forming a large number of reinforcing structures as described above intermittently along the longitudinal direction of the tubular body.

  FIG. 8 is a partial perspective view showing a state in which the temporary pile 11 on the tubular body side is driven at the side end portion of the geogrid 31 on the foundation ground 16. In FIG. 8, a geogrid 31 is disposed on the foundation ground between the tubular body 17a and the tubular body in front of the tubular body 17a, and a side end portion along the tubular body on the foundation ground of each geogrid. 2, two temporary piles 23 are driven. The horizontal streak 25 of the temporary pile 23 holds the geogrid firmly on the foundation ground 16 by pressing the mesh of the geogrid 31, whereby the bent portion of the geogrid is fixed and held, and is tubular from the rising portion. It is in close contact with the body 17a. Since the temporary pile 23 is driven into the foundation ground up to the horizontal bar 25, the mounting position of the horizontal bar 25 may be a position where the driving stability of the temporary pile is maintained. About 10 to 60 cm from the lower end. Further, the height above the horizontal bars 25 of the temporary pile 23 is preferably set to such a height that the bent rising portion of the geogrid is completely fixed by the formation of the backfill layer, for example, about 30 to 150 cm.

  After the geogrid 31 is laid as shown in FIG. 7 and the temporary pile 23 is driven, it is backfilled with soil material. At this time, in the backfilling between the tubular bodies, first, the backside of the temporary piles 23 is backfilled to the vicinity of the hook portion 24, and then the temporary piles 23 are pulled out and the backfilling is continued. Complete. According to this preferred embodiment, sandy soil is preferably used as the soil material.

  9 and 10 are diagrams for explaining the formation of a reinforcing structure for strengthening the ground using the geogrid 32 and the temporary holding pile 33. FIG. Such a reinforcing structure can be suitably used as a foundation ground such as embankment, concrete retaining wall, and box culvert. In FIG. 9, a geogrid 32 is laid with a U-shaped portion extending along the side wall and bottom surface of the excavation groove 27 formed in the foundation ground 26 so that both ends are left at the top. A temporary pile 33 similar to that described above is placed in the vicinity of the rising portion of the bottom surface of the geogrid 32, and the geogrid 32 is firmly fixed by the horizontal streak 34 and is in close contact with the ground 26. The formed U-shaped groove is filled with crushed stone 35, which is a soil material, up to the height near the hook portion of the temporary pile 33, the temporary pile is pulled out, and the crushed stone surface is covered with the surplus geogrid. Complete the surrounding structure of the crushed stone 35. Thereafter, the surrounding structure is filled with a soil material 36, preferably a sand material, to complete a reinforced ground.

It is a fragmentary perspective view which shows an example of the geogrid which can be used in this invention. It is a fragmentary perspective view which shows an example of the geogrid which can be used in this invention. It is sectional drawing which shows an example of the embedding structure of the tubular body using the geogrid temporary holding pile of this invention. It is drawing which shows an example of the pile for geogrid temporary attachment of this invention. It is a cross-sectional view which shows an example of the driving | running state of the geogrid temporary pile in this invention. It is a front view which shows an example of the driving | running state of the geogrid temporary pile in this invention. It is sectional drawing which shows an example of the embedding structure of the tubular body using the geogrid temporary holding pile of this invention. It is a fragmentary perspective view which shows an example of the driving | running state of the geogrid temporary pile in this invention. It is sectional drawing which shows the usage example of the pile for geogrid temporary attachment of this invention for reinforcement of the ground. It is sectional drawing which shows the reinforced ground structure constructed | assembled using the geogrid temporary holding pile of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Excavation groove 2 Foundation ground 3 Geogrid 31 Geogrid 32 Geogrid 4 Side wall 5 Crushed stone layer 6 Tubular body 7 Sandy layer 8 Crushed stone layer 9 Pavement layer 10 Paved road 11 Suspension pile 12 Hook part 13 Horizontal bar 14 Vertical bar 15 Excavation Groove 16 foundation ground 17 tubular body 18 side wall 19 side wall 21 sheet pile 22 crushed stone layer 23 pile for temporary retention 24 hook part 25 transverse reinforcement 26 ground 27 excavation groove 33 pile for temporary retention 34 transverse reinforcement 35 crushed stone 36 soil material

Claims (9)

A geogrid is laid on the excavated ground so as to form a U-shaped part consisting of a bottom surface part and a rising part, and a soil material is sprinkled into the U-shaped part to partly or entirely part of the soil material. In the reinforcement method for the ground and / or underground structure that constructs the surrounding structure, in the vicinity of the rising part of the bottom part of the geogrid, a pile for temporary anchoring comprising a rod-like body having a U-shaped hook at the tip and a horizontal bar at the middle After the geogrid is fixed on the excavation ground by the horizontal streak portion, the soil material is spun out to the height near the hook portion, and then the pile for temporary suspension is pulled out. Reinforcement method for ground and / or underground objects characterized by The ground and / or underground buried reinforcement method according to claim 1, wherein the soil material is a coarse-grained soil material. The method for reinforcing ground and / or underground objects according to claim 1 or 2, wherein after the pile for temporary anchoring is pulled out, the same or different soil material is further added. The ground and / or underground buried article according to any one of claims 1 to 3, wherein the underground buried object is a tubular body, and the tubular body is disposed so that at least a part of the tubular body is located within the U-shaped portion of the geogrid. Reinforcement construction method. The ground and / or underground buried reinforcement method according to claim 4, wherein crushed stone is used as a soil material up to the vicinity of the upper portion of the tubular body. The underground buried object is one or a plurality of tubular bodies, and the geogrid covers the upper part of the tubular body and between the tubular body and the excavated ground side wall, or between the tubular body and the excavated ground side wall. The ground and / or underground buried object reinforcing method according to any one of claims 1 to 3, wherein the ground and / or underground buried object is laid so as to form a U-shaped portion between the tubular body and the tubular body. The ground and / or underground buried reinforcement method according to claim 6, wherein a semicircular groove for laying a tubular body is provided in advance on the excavated ground, and the tubular body is placed thereon. The reinforcing method for ground and / or underground objects according to any one of claims 4 to 7 , wherein the geogrid is laid continuously in the longitudinal direction of the tubular body. The reinforcing method for ground and / or underground objects according to any one of claims 4 to 7 , wherein the geogrid is laid intermittently in the longitudinal direction of the tubular body.

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