JP2004300726A - Method for aseismically strengthening ground in drain placing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance earthquake resistance by imparting shear strength to ground in addition to the securement of a drainage function only by placing a drain material. <P>SOLUTION: In a drain placing method, a hole is bored by inserting a casing into the ground through the use of construction machinery for erecting the casing, the hollow cylinder-shaped drain material, wherein linear synthetic resins are piled, is inserted into the erected casing, and after that, the casing is extracted so that the drain material can be left in the ground, and the drain material 1 to be driven, which is set to have high compressive strength and great toughness against bending, in addition to the drainage function, is driven at a prescribed density. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for seismic reinforcement of ground in a drain casting method.
[0002]
[Prior art]
As a method of preventing liquefaction in sandy ground, there is a method of digging a kind of well in sandy ground and trying to suppress the liquefaction phenomenon by releasing the groundwater pressure that rose during the earthquake to the surface from the well. Conventionally, for example, a thin pipe-shaped filter material made of a woven fabric is wound around an outer peripheral surface of a drain pipe in which a number of holes are formed in a plastic pipe having a diameter of about 10 cm, in a sandy ground to be processed. A drain pipe method of burying a plurality of pipes in the vertical direction at a predetermined interval, and excavating a plurality of holes having a diameter of, for example, 50 cm and a depth of about 20 m at predetermined intervals in a sandy ground to be subjected, and putting crushed stone into the holes, The crushed stone drain method of filling and forming a crushed stone pile was adopted.
[0003]
In the drain pipe method, the outer surface of a plastic pipe with many holes is coated with a sheet-like filter material.If the space between the many holes is wide, drainage due to a sudden rise in groundwater pressure is not possible. In addition, the filter material corresponding to the perforated portion acts only locally, and the filter function may be significantly reduced. In addition, since the opening ratio of the drain pipe is 20 to 30%, there is a limit to the amount of pore water flowing in the horizontal direction, and there is a limit to the water permeability of the drain material.
[0004]
Conversely, if the interval between the many holes is narrowed, water collection improves, but the strength of the pipe itself, that is, the pressure resistance to earth pressure, deteriorates, and the pipe is crushed by earth pressure due to long-term burial and multiple small earthquakes. When it becomes necessary (when an earthquake of about 5 or more occurs in the seismic intensity class of the Japan Meteorological Agency), the function cannot be performed.
[0005]
In addition, in the crushed stone drain method, crushed stone is charged and filled into the excavated well hole, and the work is carried out, so the construction work is large and the workability is poor, and the use of a large construction machine is necessary. Not suitable for construction with structures or in narrow spaces. Furthermore, when the groundwater rises due to rainfall, earthquake, or the like, sand enters the gaps of the crushed stones and gradually fills the gaps, so that the function may not be able to be sufficiently performed when needed.
[0006]
In order to solve the drawbacks of the drain pipe method and the crushed stone drain method, there are the following patent publications.
[0007]
[Patent Document 1]
Japanese Patent No. 2556801
In this method, well holes having a predetermined size and a predetermined depth are drilled at predetermined intervals in the geology and ground of sand, and a resin string 9 as shown in FIG. Drainage material which is laminated in a hollow columnar shape having a predetermined hole 4 along the length direction of the portion, welds the contact portion of the resin string 9, and winds and arranges a filter material (not shown) on the outer peripheral surface. 2 are respectively buried.
[0009]
According to the liquefaction prevention method disclosed in Japanese Patent No. 2555681, the drainage material having a porosity of 80% or more is used in the well hole, so that all parts of the filter material wound around the outer peripheral surface are filled into the drainage material. Groundwater infiltrates, almost no clogging of the filter material is observed, sufficient drainage capacity can be maintained for a long time, and since the drainage material itself has excellent pressure resistance, the shape of the well hole for a long time It is said that maintenance is possible.
[0010]
[Problems to be solved by the invention]
However, the liquefaction prevention method disclosed in the above-mentioned Japanese Patent No. 2555681 does not contribute to the seismic reinforcement of the ground, although the drainage function is enhanced.
[0011]
Japanese Patent Application Laid-Open No. 2001-11848 discloses a gravel drain that simultaneously achieves ground liquefaction prevention and ground reinforcement during an earthquake and achieves effective use of resources.
[0012]
This means that among the materials selected according to the particle size, materials having a particle size in a range usable as a drain material are formed and arranged on the ground at predetermined intervals as gravel drain piles, and have a particle size in the other range. The material was formed and arranged as a compacted pile at the center of the gravel drain pile or around the gravel drain pile.
[0013]
For example, gravel drain piles for preventing liquefaction of the ground are arranged concentrically around the pile around a compaction pile for the purpose of reinforcing the ground. And the gravel drain pile is formed by using a material having a particle diameter in a range suitable for use as a drain material by selecting a material having a wide range of particle diameters according to the particle diameter. It is said that since the drain material is made of a material having a particle size in an unsuitable range for use, the useless portion of the material is reduced, and the liquefaction prevention and reinforcement of the ground during an earthquake can be achieved at the same time. You.
[0014]
Also in the gravel drain disclosed in Japanese Patent Application Laid-Open No. 2001-11848, the configuration of both the drain material and the compaction pile is combined, and the drain material does not make the ground seismic reinforcement.
[0015]
In addition, when an earthquake occurs, the ground fluidization may cut the gravel drain pile and drain material, making it impossible to ensure the drainage function.
[0016]
An object of the present invention is to solve the above-mentioned disadvantages of the conventional example, and to provide a drainage function by simply placing a drain material, in addition to securing a drainage function, to impart a shear strength to the ground, and to improve seismic resistance. It is an object of the present invention to provide a seismic retrofitting method for the ground.
[0017]
[Means for Solving the Problems]
The present invention, in order to achieve the above object, a hole is drilled by inserting a casing into the ground using a construction machine for casing construction, and a hollow cylindrical shape in which a linear synthetic resin is stacked in the built casing. In the drain casting method in which the drain material is inserted and then the casing is pulled out and the drain material is left in the ground, the drain material to be cast is added to the drainage function and the pressure resistance and toughness against bending are determined to be large. Drain material that is cast at a certain density and has high pressure resistance and toughness against bending in addition to drainage function.The synthetic resin of thermoplastic material is heated and melted and extruded from the nozzle into a string of a certain diameter. The irregularly curled resin strings are sequentially laminated by welding the mutually contacting portions to form a hollow cylindrical shape having a predetermined cavity in the center along the length direction. It is be mixed thick linear synthetic resin than the other part when it is an gist.
[0018]
According to the first aspect of the present invention, the cylindrical drain material in which the linear synthetic trees are overlapped has a porosity of 80% or more, and groundwater enters the drainage material from all parts, When the groundwater pressure rises rapidly due to an earthquake or the like, groundwater is quickly drained or ejected to the outside from the hole at the center of the drain material, so that liquefaction does not occur in the surrounding ground. Moreover, in addition to securing such a drainage function, by densely casting a drain material having high pressure resistance and bending toughness, it is possible to impart shear strength to the ground and improve earthquake resistance. In addition, since the drain material has high toughness and high flexibility, it is not cut by a slight deformation due to the flow of the ground, and the drainage function is secured.
[0019]
According to the second aspect of the present invention, in addition to the above-described functions, as an example of the drain material having high pressure resistance and toughness against bending, a cylindrical drain material formed by stacking linear synthetic resins has such properties. However, by mixing a linear synthetic resin that is thicker than the others into a part, it can be realized easily and inexpensively.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a front view showing one embodiment of a method of draining a ground by seismic reinforcement of the ground in the draining method of the present invention. To explain the drain material 1 to be cast first, as shown in FIG. It consists of a drainage material 2 and a filter 3 wrapped around the drainage material. The basic length of the drainage material 2 is about 3 to 4 m. To a length that can be installed into the ground at a predetermined depth.
[0021]
The drainage material 2 is formed, for example, by heating and melting a resin string, that is, a synthetic resin of a thermoplastic material such as polypropylene, polystyrene, polyethylene, or polyester, and forming a string having a constant diameter of about 1 to 6 mm (standard diameter 2 mm) from a nozzle. The resin strings 9 are sequentially laminated in an extruded and irregularly curled state, and a laminated string-like polypropylene or polystyrene or polyethylene or polyester interconnecting portion having a predetermined hollow hole 4 along its length in the center is formed. It is welded and formed into a hollow cylindrical shape, and has an outer diameter of 50 mm to 150 mm.
[0022]
The drainage material 2 has a predetermined hole 4 formed in the center thereof along the length direction, is substantially flexible and has high pressure resistance, and has a surface aperture ratio of 90 to 95% (varies depending on density). The porosity is 85 ± 5% (the density and the like can be adjusted).
[0023]
For example, assuming that the number of nozzles for extruding the synthetic resin of the thermoplastic material by heating and melting into a string having a constant diameter is 18, three of the nozzles are larger in diameter than the other nozzles and larger than the others. In order to form the resin string 9a, the drainage material 2 was partially mixed with a linear synthetic resin (resin string 9a) thicker than the other, as shown in FIG.
[0024]
Although the resin string 9 and the resin string 9a thicker than the others are used, the resin string 9 in the present invention is 1.5 to 2 mm as shown in FIG. , 2.5 to 3 mm, and the resin string 9a thicker than the others is about 5 to 6 mm.
[0025]
The resin string 9 and the resin string 9a thicker than the other are about 1/6 of the former, and the resin string 9a thicker than the other is curled while the length of the drainage material 2 in the longitudinal direction. It will be like a vertical member, so to speak.
[0026]
The drainage member 2 may be made of a thermoplastic material such as polypropylene, polystyrene, polyethylene, polyester, or a recycled material, which is a recycled material such as plastic bottles, styrofoam, waste materials of home appliances, and beverage bottle cases.
[0027]
As described above, the use of recycled materials for the drainage member 2 reduces the amount of waste disposal and contributes to effective use of resources, and is environmentally friendly.
[0028]
As shown in FIG. 3, first, drilling of the drain material 1 is performed by using a construction machine 6 such as a dedicated small boring machine or the like with the casing 8 of the tip end closing bit 7. The construction machine 6 is provided with a relatively short leader 13 that can be raised and lowered on a heavy machine 15 such as a small crawler, and moves the rotary drive device 14 of the casing 8 up and down along the leader 13.
[0029]
In this way, the construction machine 6 is built on the ground while rotating the casing 8. It should be noted that the casing 8 has a predetermined length by adding unit piece bodies until the distal end closing bit 7 reaches a predetermined depth.
[0030]
Then, the drain material 1 is inserted into the built casing 8, and the drain material 1 is inserted while drainage materials 2 of about 3 to 4 m are sequentially added by the joint 5. At this time, the filter 3 is mounted on the outer periphery of the drainage material 2.
[0031]
After the drain material 1 is inserted, the casing 8 is pulled out while leaving the tip closing bit 7 as a weight together with the drain material 1, and a head horizontal drain 10 such as a gravel mat or a water-permeable mat is provided as a drainage treatment facility for the surface layer. 1 is connected to the head horizontal drain 10. 11 is a liquefied layer, 12 is a non-liquefied layer.
[0032]
The drain material 1 is cast at a pitch of about 1 m, and has a staggered or triangular arrangement as shown in FIG. 5A, a lattice or square arrangement as shown in FIG. A circular arrangement may be used. In addition, the drain material 1 that is obliquely cast can be combined.
[0033]
In this manner, the drain material 1 has a porosity of 80% or more, and groundwater infiltrates into the drainage material from all parts, and when the groundwater pressure suddenly rises due to an earthquake or the like, the drain material 1 The groundwater is quickly drained or ejected to the outside from the hole at the center of the pit, so that liquefaction does not occur in the surrounding ground.
[0034]
Moreover, in addition to securing such a drainage function, by densely casting a drain material having high pressure resistance and bending toughness, it is possible to impart shear strength to the ground and improve earthquake resistance. Further, since the drain material 1 has high toughness and high flexibility, it is not cut by a slight deformation accompanying the flow of the ground as shown in FIG. 2, and the drainage function is secured. In the figure, α is a subsidence due to drainage, and such subsidence increases the ground density and rigidity.
[0035]
【The invention's effect】
As described above, the seismic strengthening method for the ground in the drain casting method of the present invention is to improve the seismic resistance by imparting shear strength to the ground in addition to securing the drainage function only by placing the drain material. It is possible.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of a drain driving method for seismic reinforcement of the ground in the drain driving method of the present invention.
FIG. 2 is a front view showing deformation during an earthquake.
FIG. 3 is an explanatory view showing a step of placing a drain material.
FIG. 4 is a perspective view of a drain material.
FIG. 5 is an explanatory view showing a placement arrangement of drain materials.
FIG. 6 is a perspective view of a drainage material among drain materials.
FIG. 7 is a perspective view of a conventional drainage drainage material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Drain material 2 ... Drainage material 3 ... Filter 4 ... Hole 5 ... Joint 6 ... Construction machine 7 ... Tip closure bit 8 ... Casing 9 ... Resin string 9a ... Resin string 9 thicker than others ... Gravel mat 11 ... Liquefaction layer 12: non-liquefied layer 13: leader 14: rotary drive device 15: heavy equipment

Claims (2)

Drilling is performed by inserting the casing into the ground using a construction machine for casing construction, inserting a hollow cylindrical drain material with linear synthetic resin layered into the built casing, and then pulling out the casing In the drain casting method where the lever material is left in the ground, the drain material to be cast shall have high pressure resistance and bending toughness in addition to the drainage function, and the drain material shall be cast at a constant density. A method of seismic reinforcement of the ground in drain construction method characterized by: The drain material, which has high pressure resistance and toughness against bending, in addition to the drainage function, heats and melts the synthetic resin of thermoplastic material, extrudes it from the nozzle into a string of a certain diameter, and the resin strings that are curled irregularly are in contact with each other. Are deposited one after the other, and when molded into a hollow cylindrical shape having a predetermined cavity along the length direction in the center part, a partly mixed linear synthetic resin thicker than others is drained Reinforcement Method for Ground in Japan

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