JP2019108677A - Drain pile and liquefaction countermeasures method - Google Patents

Abstract

To provide a drain pile capable of suppressing the influence of liquefaction that can be easily installed around an existing structure, and a liquefaction countermeasure method using this drain pile.SOLUTION: A drain pile 100 of a typical configuration according to the present invention is a tubular drain pile 100 embedded in the ground, and comprises a tapered tip portion 104 which is closed, a water inlet 108 which is formed on a side surface 106 and into which underground water flows, and a water outlet 110 which is open on the ground.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tubular drain pile embedded in the ground and a liquefaction prevention method using the drain pile.

  The area where urbanization is in progress is often a modified land where artificial topography has been changed. In particular, in areas near rivers and the sea in the plain area, soft ground containing a large amount of water, such as paddy field marks and landfill sites, has also been widely used and developed. Therefore, some cities are worried about the occurrence of liquefaction caused by the earthquake. When the liquefaction phenomenon occurs, the ground surface sinks, and the support on the ground may lose its supporting power and tilt.

  An example of a structure susceptible to the liquefaction phenomenon is a utility pole. A vertically elongated utility pole is easy to tilt because the center of gravity is also high. Then, the liquefaction measures of predetermined are conventionally taken to the utility pole built on soft ground.

  As measures against liquefaction of utility poles in the past, a rooting method, a gravel drain method (hereinafter, a gravel method) and the like are known. The rooting method is a method of installing rooting (rooting) in the lower part of the surface of the utility pole in order to expand the pressure receiving area of the utility pole from the ground. The foundation is a member made of concrete or resin attached to intersect with the utility pole, and is attached to the utility pole with a dedicated U-shaped bolt at a depth of about 0.3 m from the ground surface. The gravel construction method is a construction method of providing a pile-like area (crushed pile) in which crushed stone is embedded in a longitudinal direction in every corner of the installation part of the utility pole for the purpose of promoting drainage from the ground at the time of earthquake occurrence. In the crushed stone pile, a surrounding net is installed to prevent the inflow of earth and sand from the surrounding.

  The rootstock method and the gravel construction method are both performed using members other than utility poles, such as rootstocks and crushed stone piles. On the other hand, as a technology for applying measures to the utility pole itself, for example, Patent Document 1 proposes a technology for providing the hollow portion 2 in the rooting portion of the column 1. In this technology, the excess pore water pressure generated in the liquefied ground 11 is dissipated using the hollow portion 2 of the column 1 and the drainage member 6 on the outside of the hollow portion 2 to prevent the column 1 from falling and the like. .

JP-A-4-336111

  However, there are points to be considered in implementing each of the above measures. First of all, it is necessary to secure a wide construction range in the rootstock method and gravel method. For example, when building a telephone pole in a private area, it is often built near the border with other private areas or public roads such as public roads so as not to obstruct the landscape or hinder the access to the area. However, there are also many facilities such as block fences at the boundaries between lands. Therefore, in the vicinity of the boundary between lands, there may be a case where a sufficient construction range can not be secured when attaching a rootstock having a maximum width of about 1.2 m or providing crushed stone piles around a utility pole.

  In addition, it is also necessary to consider the labor of the workers. In the rooting method, in order to set the rooting to a depth of about 0.3m from the ground surface, it is necessary to excavate the ground around the utility pole by 0.3m plus the thickness of the rooting. In the gravel construction method, it is necessary to excavate wider than the original penetration area of the utility pole in order to provide the crushed stone pile around the utility pole. In addition, the foundation is about 70 kg made of concrete and about 30 kg made of resin, and the crushed stone pile also has a corresponding weight. Therefore, in both the root and gravel construction methods, the labor burden on workers is greatly increased in terms of drilling and transportation.

  Points to consider also exist in the technology of Patent Document 1. This technology is configured to release water into the hollow portion 2 of the column 1 and the drainage member 6 when an earthquake occurs. However, in the case of liquefied ground, the groundwater level is shallow, about 1.0 m from the ground surface. Therefore, water may already be accumulated in each member before the occurrence of the earthquake, and there is a possibility that a sufficient liquefaction suppressing effect can not be exhibited at the time of the occurrence of the earthquake. Moreover, it is necessary to provide a hole in the column 1 in order to connect the hollow part 2 and the member 6 for drainage, but the reinforcement of the column 1 may be damaged, or the hole provided in the vicinity of the ground may be a weak point when loaded. And the influence on the design load of the column 1 is also a concern.

  Above all, since the rootstock method and the gravel method are methods performed at the time of the utility pole facility, and the technology of Patent Document 1 is a technique applied to the column itself, none of them can be implemented for an existing utility pole. Although it is possible to carry out the erection method and the gravel method at the time of rebuilding of the utility pole, it is necessary to take off the installation pole of the electric wire etc. as well, so the implementation period is not easy and the implementation is not easy.

  In view of such problems, the present invention aims to provide a drain pile capable of suppressing the influence of liquefaction that can be easily installed around an existing structure, and a liquefaction countermeasure method using the drain pile. And

  In order to solve the above problems, a typical configuration of the drain pile according to the present invention is a tubular drain pile embedded in the ground, and a plurality of closed tapered tip portions and side surfaces are formed. It is characterized by comprising a water intake port into which the inside water flows and a drainage port opened on the ground.

  According to the above-described drain pile, it is possible to quickly dissipate pore water pressure in the ground, which causes liquefaction, by causing water in the ground to flow into the interior when an earthquake occurs. Therefore, by embedding in the periphery of the target structure, it becomes possible to suppress the influence of liquefaction such as settlement or inclination of the structure at the time of earthquake occurrence. Moreover, according to the above configuration, installation can be performed by a simple operation of embedding in the ground, and implementation is possible even for an existing structure even if the construction range is narrow. It is.

  The drain stake may be splittable into a plurality of parts in the longitudinal direction. According to this configuration, the drain pile can be efficiently embedded deeper in the ground.

  The drain pile further has a nose smaller in diameter than the underground portion where the water inlet is formed, connected to the upper end side of the underground portion, and partially exposed to the ground, and the drainage port is formed in the nose It may be done. This configuration makes it possible to make the ground part smaller and less noticeable while draining.

  The drain stake may further comprise a cover that hides the above-ground part where the drainage port is formed. By providing the cover, it is possible to prevent the entry of foreign matter into the drainage port, improve the appearance, and the like.

  The drain pile may further include a predetermined mesh covering the water inlet from the inside. By providing the mesh, it is possible to prevent the infiltration of earth and sand into the water intake.

  In order to solve the above-mentioned subject, the typical composition of the liquefaction measures construction method concerning the present invention is characterized by embedding the above-mentioned drain pile along a pillar built outdoors. The component corresponding to the technical idea in the drain pile mentioned above and its description are applicable also to the said liquefaction measures construction method. In particular, it is a simple operation only for embedding in the ground, and it can be carried out even for the existing structure even if the construction range is narrow, and the labor of the worker can be light.

  According to the present invention, it is possible to provide a drain pile capable of suppressing the influence of liquefaction, which can be easily installed around the existing structure, and a liquefaction preventing construction method using the drain pile.

It is a figure showing an outline of a drain pile concerning an embodiment of the present invention. It is a figure showing an outline of a liquefaction phenomenon. It is the figure which showed the further structure of the drain pile. It is the figure which showed the process of placement work of the drain pile. It is a figure showing the liquefaction measures construction method using a drain pile. It is a figure which shows the outline and result of a model test of the liquefaction measures construction method using a drain pile.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values and the like shown in the embodiments are merely examples for facilitating the understanding of the invention, and the invention is not limited except as otherwise described. In the present specification and drawings, elements having substantially the same functions and configurations are denoted by the same reference numerals to omit repeated description, and elements not directly related to the present invention are not illustrated. Do.

(Drain pile)
FIG. 1 is a diagram showing an outline of a drain pile 100 according to an embodiment of the present invention. GL in the figure shows the ground surface (Ground Line). The drain pile 100 is a member for releasing water in the ground when a liquefaction phenomenon occurs in the ground, and is used to suppress the settlement and inclination of the structure. In the present embodiment, it is assumed that a plurality of drain piles are embedded around the utility pole on the assumption that the implementation is performed as a measure for liquefaction of the utility pole 102.

  The drain pile 100 is formed of a straight steel pipe, and is vertically embedded in the ground along the utility pole 102 so as to reach deeper than the utility pole 102. The tip portion 104 has a closed tapered shape so as to be easily inserted into the ground. The tip portion 104 may have a conically pointed configuration, but may alternatively have a twisted groove, such as a drill. If it is a drill-like tip, it can be buried in the ground by a screwing operation.

  A plurality of water suction ports 108 are formed on the side surface 106. The water absorption port 108 is a hole through which water in the ground flows in when the liquefaction phenomenon occurs. The water suction ports 108 form a plurality of rows in the outer circumferential direction of the side surface 106, and are formed at equal intervals in the longitudinal direction of the side surface 106 for each row. At this time, the water absorption ports 108 can also be formed, for example, in a zigzag form with the next row. Further, the drain pile 100 is embedded until it reaches deeper in the ground than the lower end of the power pole 102, and the water inlet 108 is also disposed to a position deeper than the lower end of the power pole 102.

  The drainage port 110 is provided on the upper end side of the drain pile 100. The drain pile 100 is embedded in the ground such that the drainage port 110 is exposed to the ground. By opening the drainage port 110 on the ground, the pressure when water flows into the water absorption port 108 can be relieved, and the water can be overflowed to the ground to obtain a continuous drainage effect.

  The liquefaction phenomenon will be briefly described with reference to FIG. FIG. 2 is a diagram showing an outline of the liquefaction phenomenon. The liquefaction phenomenon is a phenomenon that occurs on sandy soils that are larger in particle size than clay. In particular, liquefaction is likely to occur in landfills near rivers and the sea. In such a landfill, a large amount of groundwater is contained, and the groundwater surface 114 (a surface where the pressure and pressure of the groundwater meet) is also located shallowly from the ground surface 112.

  As shown in the left diagram in FIG. 2, before the occurrence of an earthquake, an interlocking force (effective stress) is generated between the sand grains 116, and the ground is in a stable state. However, as shown in the central figure, when sand grains 116 are subjected to shear stress during an earthquake, the force (pore water pressure) to push out the water (pore water 118) present in the gaps between sand grains 116 increases. And the mesh between the sand grains 116 is lost. As a result, the sand grains 116 float in water (liquefied). At this time, a gushing 120 to the ground and a fountain 122 are also generated. In addition, heavy structures above the ground sink and light structures such as underground water pipes rise. Then, as shown in the right figure, after the occurrence of the earthquake, although the sand grains 116 contact with each other again, the sand grains 116 settle by the amount of the gap water 118 which has been dropped, and the ground surface 112 also settles.

  The above-mentioned drain pile 100 (see FIG. 1) causes the water pressure in the ground to be dissipated at an early stage by letting water in the ground flow into the inside from the water intake 108 at the time of the occurrence of an earthquake. Preventing the sinking and tilting of Therefore, according to the said drain pile 100, it becomes possible to suppress the influence of liquefaction, such as settlement of a structure, inclination, etc. at the time of an earthquake occurrence, by embedding at the periphery of the target structure.

  FIG. 3 is a view showing a further structure of the drain pile 100. As shown in FIG. FIG. 3A shows that the drain pile 100 is provided with a nose 124. The nose 124 is integrally formed with the cap 126, and is connected to the upper end of the underground portion 128 provided with the water inlet 108 of the drain pile 100 together with the cap 126, and a part thereof is exposed to the ground. The nose 124 is smaller in diameter than the underground portion 128 and has a drain 130 at its upper end. A narrow diameter nose 124 is beneficial in terms of aesthetics, as it allows drainage while making the above-ground portion of the drain pile 100 smaller and less noticeable.

  The water absorption port 108 and the drainage port 130 (including the drainage port 110 in FIG. 1) can be provided with a predetermined mesh inside. For example, by covering the inside of the water absorption port 108 with a mesh, it is possible to prevent the entry of soil and the like to the water absorption port 108 and the clogging thereof. Also, by providing the drainage port 130, it is possible to prevent the entry of foreign matter into the inside of the drain pile 100 and the like. Such a mesh can be implemented by a water-permeable sheet, a wire mesh, or an open-cast hard resin. Further, as in the case of the mesh, it is also possible to prevent the infiltration of foreign matter into the pile by filling the pile with the material of the water-permeable structure.

  FIG. 3 (b) shows the drain pile 100 provided with the cover 132. The cover 132 is a component that covers the above-ground portion of the drain pile 100 in which the drainage port 130 is formed. The cover 132 has a structure that does not obstruct the drainage port 130, such as forming a space between the cover 132 and the drainage port 130 (including the drainage port 110 in FIG. 1). The cover 132 can be implemented, for example, in the form of a divisible ring centered on the utility pole 102 or the like. By providing the cover 132, it is possible to prevent the entry of foreign matter into the drainage port 130, improve the appearance of the ground portion, and further prevent mischief.

  FIG. 4 is a view showing the process of placing the drain pile 100. As shown in FIG. FIG. 4A shows an outline of the placing operation. The drain pile 100 can be driven and installed on the ground along the power pole 102 using a pile driver 134. The drain pile 100 can be appropriately embedded in the ground by screwing work or by inserting it into a hole excavated in advance as long as it has the above-described drill-like tip, in addition to the pouring work. It is.

  The drain pile 100 can be divided into a plurality of parts in the longitudinal direction. For example, the drain pile 100 is divided into an A-part 100a including the tip portion 104, an intermediate B-part 100b, an upper end-side C-part 100c, and a nose 1124 integral with the cap 126 (see FIG. 3A) . This configuration makes it easy to carry out the placing operation with the pile driver 134, and the weight is dispersed to facilitate transportation and construction.

  FIG. 4 (b) shows a state during the placement work. In the drain pile 100, the A part 100a is driven by the pile driver 134, then the B part 100b is connected to the upper end of the A part 100a, and the B part 100b is driven again by the pile driver 134. FIG. 4 (c) shows the state when the setting work is completed. After the drain pile 100 is driven to the C part 100c, installation is completed by connecting the cap 126 to the upper end. Thus, since the drain pile 100 is divided in the longitudinal direction, it is easier to work in the operation of the pile driving machine 134 and the like than when driving one long pile, and from the lower end of the power pole 102 It is also possible to drive efficiently to deeper positions in the ground.

(Liquefaction countermeasure method)
FIG. 5 is a view showing a liquefaction countermeasure method using the drain pile 100. As shown in FIG. The liquefaction countermeasure method is characterized in that the drain pile 100 described above is embedded along a pillar such as a power pole which can be built outdoors.

  FIG. 5 (a) shows that the liquefaction countermeasure construction method is implemented on the existing power pole 102a. In FIG. 5A, a total of six drain stakes 100 are embedded uniformly around the existing power pole 102a. The drain pile 100 can be installed only by driving it into the ground with a pile driver 134 or the like as described with reference to FIG. 4 and does not require excavating work or a large-scale heavy machine. Therefore, if it is the said liquefaction measures construction method which used drain pile 100, compared with the conventional root girder construction method etc. work is easy, and it can carry out also to the existing power pole 102a easily.

  FIG.5 (b) is a mode that the said liquefaction measures construction method was implemented to the utility pole 102b enclosed by the crucible. The utility poles are often erected near the boundary between lands, and it is often the case that two sides are surrounded by a weir 136 like the utility pole 102b. In such a narrow place, it is difficult to carry out the rooting method or gravel method without modifying the weir 136. However, the drain pile 100 can be installed only by embedding vertically in the ground. Therefore, it is possible to absorb water at the time of liquefaction and suppress the inclination or the like of the utility pole 102b by, for example, only hitting three vacant portions in the periphery of the utility pole 102b.

  As described above, if it is the liquefaction countermeasure construction method, it can be carried out by a simple operation of embedding the drain pile 100 in the ground, so the labor burden on the workers is light and the construction range also for the existing structure Even if it is narrow, it can be implemented without problems and is preferable.

(Model experiment)
FIG. 6 is a diagram showing an outline and results of a model test of the liquefaction prevention method using the drain pile 100. As shown in FIG. In this model test, the effectiveness of the above-mentioned liquefaction prevention method was examined.

  FIG. 6A is a diagram showing an outline of a model experiment. The experiment is conducted by laying a silica sand 142 on the vibrating table 140, building a model of a utility pole (methods A to D, column 10) with each measure taken there, and applying a vibration simulating an actual earthquake wave. The As a model of the utility pole, assuming that the 14 m utility pole is scaled to 1/25, an aluminum pipe having a length of 560 mm and an outer diameter of 14 mm was prepared. In addition, a 45 mm steel pipe was prepared as a pile model. The models of the piles were all closed at the tip end, and those with and without water inlets were prepared.

  The experiment was conducted on five models, one in which the construction methods A to D were applied to the model of the utility pole and the other one in which no element 10 was applied. The methods A to D differ in the condition of the pile. First, Method A divides the outer periphery of the model of the electric pole into six equal parts, and secures a total of three piles without water inlets by bonding and bonding at each of three consecutive places. In method B, piles with water inlets were fixed at three locations similar to method A. In Method C, a total of six piles without water inlets were fixed at each location obtained by equally dividing the outer periphery of the model of the electric pole into six. In method D, piles with water inlets were fixed at six locations similar to method C.

  FIG. 6B shows the test result of the vibrating table 140 as viewed from above. The values of the vertical and horizontal axes are distances mm. The test results show how much the upper ends of the methods A to D and the column 10 are inclined with respect to the root. From the test results in FIG. 6 (b), it is found that the column 10 is most inclined, followed by method A (pile with no water inlet x 3) and method C (pile with water outlet x 6) I understand. On the other hand, it can be seen that the inclination of the method B (three piles with water absorption openings) and the method D (four piles with water absorption openings) is suppressed.

  FIG. 6C shows a test result of the vibrating table 140 viewed from the side. In FIG. 6C, the attitude of the model before the experiment is shown by a broken line, and the attitude of the model after the experiment is shown by a solid line. The horizontal axis is distance mm, and the vertical axis is height mm. Also from the test results in FIG. 6C, it can be seen that the column 10 is most inclined. In addition, the inclination of method B (three piles with water inlet) is smaller than that of method A (three piles without water inlet), and method C (six piles without water inlet) It can be seen that the inclination of the method D (pile with a water absorption opening x 6) is suppressed more than that.

  As described above, from the model test, it is confirmed that the electric pole provided with the pile can suppress inclination more than the column 10, and that the pile with the water inlet can suppress the inclination of the electric pole more than the simple pile. did it. Thereby, it was proved that the liquefaction countermeasure method using the drain pile 100 and the drain pile 100 described above is effective for suppressing the inclination and the settlement of the power pole 102 of the liquefied ground.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the appended claims, and of course these also fall within the technical scope of the present invention. It is understood.

  INDUSTRIAL APPLICABILITY The present invention can be used as a tubular drain pile embedded in the ground and a liquefaction countermeasure method using the drain pile.

DESCRIPTION OF SYMBOLS 10 ... Element pillar, 100 ... Drain pile, 100 a ... A part, 100 b ... B part, 100 c ... C part, 102 ... Electric pole, 102 a ... Existing electric pole, 102 b ... Electric pole surrounded by a weir, 104 ... Tip part, 106 ... side, 108, water intake, 110, drain, 112, ground surface, 114, underground water surface, 116, sand grains, 118, pore water, 120, sand, 122, fountain, 124, nose, 126, cap, 128, ... Underground part, 130 ... nose outlet, 132 ... cover, 134 ... pile driver, 136 ... 塀, 140 ... shaking table, 142 ... silica sand

Claims (6)

A tubular drain pile embedded in the ground,
An occluding tapered tip,
There are a plurality of water inlets that are formed on the side and into which underground water flows,
A drain opening at the ground,
A drain pile characterized by comprising:   The drain pile according to claim 1, wherein the drain pile can be divided into a plurality of parts in the longitudinal direction. The drain pile further includes a nose smaller in diameter than the underground portion where the water inlet is formed, connected to the upper end side of the underground portion and partially exposed to the ground;
The said drain outlet is formed in the said nose, The drain pile of Claim 1 or 2 characterized by the above-mentioned.   The drain pile according to any one of claims 1 to 3, wherein the drain pile further includes a cover that covers the part of the ground where the drainage port is formed.   The drain pile according to any one of claims 1 to 4, wherein the drain pile further includes a predetermined mesh covering the water inlet from the inside.   A liquefaction preventing method characterized in that the drain pile according to any one of claims 1 to 5 is embedded along a pillar built outdoors.

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