JP2006002529A - Liquefaction prevention structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquefaction prevention structure capable of preventing liquefaction of ground by preventing a drain material from clogging and preventing ground from becoming liquid. <P>SOLUTION: A surface layer G2 is provided in the liquefaction prevention structure 1, and further, the liquefaction prevention structure is provided with a trench section 10 in which fine sand grains 11 are filled to collect rainwater, etc. a water permeable first drain member 20 which is embedded in the substantially horizontal direction in the trench section 10, and a second drain member 30 which is embedded in the depth direction down to the liquefaction layer G1. In the second drain member 30, the liquefaction layer embedded part 31 embedded in the liquefaction layer G1 has a water permeability. The water permeable constant of the liquefaction layer G1 is 10<SP>-4</SP>(cm/sec) order and the water permeable constant of the liquefaction layer embedded part 31 is ≥10<SP>-3</SP>(cm/sec). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquefaction prevention structure for discharging groundwater from a liquefied layer and preventing liquefaction of the liquefied layer.

Conventionally, in order to prevent the liquefaction phenomenon of the ground due to earthquake motion, a liquefaction prevention structure may be provided on the ground. For example, in the liquefaction prevention structure shown in Patent Document 1, a drainage material having water permeability, in which a filter such as a nonwoven fabric is attached, is embedded in the vertical direction up to a liquefaction layer such as a sandy soil layer constituting the ground. In addition, when ground vibration occurs, the liquefaction phenomenon is prevented by discharging the groundwater of the liquefied layer to the outside of the ground through the drain material.
JP 2004-44224 A

  In the liquefaction prevention structure described above, in order to guide the groundwater of the liquefied layer into the drain material, it is necessary to make the hydraulic conductivity of the drain material larger than the hydraulic conductivity of the liquefied layer. In order to secure such a large hydraulic conductivity, when the filter attached to the drain material is roughened, the soil of the liquefied layer flows into the drain material together with the ground water, and the drain material is clogged. Distribution becomes worse and countermeasures against liquefaction become insufficient. In particular, when the standby period until an earthquake occurs extends over several years, there is a concern that the drainage function of the drain material left in the ground may be fatal.

  An object of the present invention is to provide a liquefaction prevention structure capable of preventing clogging of a drain material and preventing a ground liquefaction phenomenon.

The present invention has a liquefied layer capable of causing a liquefaction phenomenon and a surface layer on the ground surface side of the liquefied layer, and in the ground supporting the building by the surface layer, groundwater is discharged from the liquefied layer during an earthquake. A liquefaction prevention structure for discharging and preventing liquefaction of the liquefied layer, the trench being provided on the surface layer and filled with coarse-grained soil to collect rainwater and the like, and the trench A first drain material embedded in the substantially horizontal direction and having water permeability, and a second drain material connected to the first drain material and embedded in the depth direction to the liquefied layer, The second drain material is characterized in that at least a liquefied layer embedded portion embedded in the liquefied layer has water permeability. At this time, the hydraulic conductivity of the liquefied layer buried portion is 10 ⁻³ (cm / sec) or more (that is, 10 ⁻⁵ (m / sec)) or more, and the average hydraulic conductivity is 10 ⁻² (cm / sec). Can do. The coarse-grained soil is preferably fine-grained sand. The first drain material may be slightly inclined as in the case of providing a water gradient or the like, for example. Further, the second drain material is not limited to the vertical direction, and may be provided obliquely from the periphery of the building to the lower side of the building.

  According to the present invention, since beautiful rainwater and the like filtered by coarse-grained soil is collected in the trench portion during rainfall, the collected beautiful rainwater and the like flow into the first drain material. Then, the liquid flows backward from the liquefied layer buried portion to the liquefied layer side through the second drain material. For this reason, the soil particles adhering to the liquefied layer buried portion of the second drain material can be pushed out to the liquefied layer side, and thereby the liquefied layer buried portion can be washed and clogging can be prevented. Since clogging of the liquefied layer buried portion is prevented in this way, when earthquake motion occurs, the second water of the liquefied layer is passed through the liquefied layer buried portion of the second drain material having a water permeability coefficient. It can be discharged from the drain material to the first drain material, and the liquefaction phenomenon of the ground can be prevented.

  In the liquefaction prevention structure described above, the liquefied layer burying portion of the first drain material and the second drain material may be configured to include a fiber material made of synthetic resin such as polypropylene. According to such a configuration, the second drain material or the first drain material is not corroded or rusted.

  In the above liquefaction prevention structure, a connection member for connecting the first drain material and the second drain material may be provided, and a detachable lid member may be attached to the surface layer side of the connection member. Good. According to such a configuration, it is possible to inspect and clean the inside of the second drain material as necessary by attaching and detaching the lid member attached to the surface layer side of the connection member.

  In the above liquefaction prevention structure, the trench part may be formed at least one of the periphery of the building and the lower side of the building. In the above liquefaction prevention structure, the building may be a house.

  According to the liquefaction prevention structure of the present invention, there is an effect that the drain material can be prevented from being clogged and the ground liquefaction phenomenon can be prevented.

Hereinafter, a liquefaction prevention structure according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a state in which the liquefaction prevention structure 1 according to the present embodiment is constructed on the ground G. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is an enlarged longitudinal sectional view showing a portion A of FIG. As shown in FIG. 1, the ground G includes a liquefied layer G1 that can cause a liquefaction phenomenon, and a surface layer G2 on the ground surface side of the liquefied layer G1. The liquefied layer G1 is composed of, for example, a sandy soil layer, and has a water permeability coefficient of the order of 10 ⁻⁴ (cm / sec) or more. The surface layer G2 is unlikely to cause a liquefaction phenomenon, and is composed of, for example, a viscous soil layer, and its water permeability coefficient is an order smaller than 10 ⁻⁵ (cm / sec). A house 100 is constructed on the surface layer G2.

  The liquefaction prevention structure 1 includes a trench portion 10 provided so as to surround the periphery of the house 100 on the surface layer G2, and a plurality of rows of first drain materials 20 embedded in the trench portion 10 in a substantially horizontal direction, for example, For example, a plurality of second drain members 30 embedded in a vertical direction to the formation layer G1 and a branch pipe 40 as a connecting member for connecting the first drain member 20 and the second drain member 30 are provided. . The first drain material 20 may be slightly inclined as in the case of providing a water gradient or the like, for example, and the second drain material 20 is inclined obliquely from the periphery of the house 100 to the lower side of the house 100. It may be provided.

  As shown in FIG. 2, the trench part 10 is formed in a trapezoidal cross section having a depth of about 30 cm and a width of about 30 cm, for example, and is connected to a sewer (not shown). The trench portion 10 is filled with fine-grained sand 11 as coarse-grained soil around the first drain material 20, and garden soil 12 and lawn 13 are provided on the surface layer side of the fine-grained sand 11. For this reason, at the time of rain, the trench section 10 collects rainwater and the like filtered through the garden soil 12, the lawn 13, and the fine-grained sand 11, and guides the collected rainwater and the like to the sewer. In this way, since dirty rainwater or the like does not flow into the second drain material 30, clogging inside the second drain material 30 can be prevented.

The first drain material 20 is a water permeable tube that functions as a filter in which a polypropylene fiber material is configured in a three-dimensional net shape. The water permeability coefficient is 10 ⁻³ (cm / sec) or more, and the average water permeability coefficient is 10 ^−2. (Cm / sec). As the first drain material 20, for example, a registered trademark “CP drain” manufactured by Chisso Corporation can be adopted.

The second drain material 30 is composed of a liquefied layer embedded portion 31 embedded in the liquefied layer G1 and a surface layer embedded portion 32 embedded in the surface layer G2. The liquefied layer burying portion 31 can employ the same member as the first drain material 20. That is, the liquefied layer burying portion 31 is a water permeable tube that functions as a filter in which a polypropylene fiber material is configured in a three-dimensional network, and its water permeability coefficient is 10 ⁻³ (cm / sec) or more, and the average water permeability coefficient is It is about 10 ⁻² (cm / sec). Further, the surface buried portion 32 can employ, for example, a water distribution pipe made of resin such as polyvinyl chloride, and does not need to have water permeability. However, if necessary, the surface layer embedded portion 32 and the liquefied layer embedded portion 31 may be integrally formed of the same material so that the whole has water permeability. The 2nd drain material 30 is installed so that the upper end of the surface layer embedding part 32 may protrude in the trench part 10, and the installation number should just specify based on the assumption amount of groundwater in the liquefied layer G1, etc. . In addition, the 2nd drain material 30 is installed in the ground G by insertion combined with a boring, or press fit, and the clearance gap between the 2nd drain material 30 and the ground G is filled with a medium grain sand etc., and, thereby, a ground surface or a house 100 sinking can be prevented.

  As shown in FIG. 3, the branch pipe 40 includes a branch pipe body 41 having a T-shaped cross section that joins two adjacent first drain materials 20 and one second drain material 30, and a branch pipe body. 41 is provided with a lid 42 detachably attached to the surface layer side of 41 by screwing or the like. If necessary, the inside of the second drain member 30 located below the branch pipe 40 can be maintained and inspected by releasing the screw or the like and removing the lid member 42 from the branch pipe main body 41. it can. As shown in FIG. 1, the branch pipe 40 has a cross-section L in order to join one first drain material 20 and one second drain material 30 at the left and right ends in the drawing. It is formed in a letter shape.

The liquefaction prevention structure 1 of the present embodiment operates as follows.
When seismic motion occurs in the ground G, the pore water pressure increases, and the groundwater in the liquefied layer G1 passes through the liquefied layer burying portion 31 having a larger permeability than the liquefied layer G1. 2 Naturally enters the drain material 30. At this time, since the liquefied layer embedded portion 31 functions as a filter, the soil particles of the liquefied layer G1 remain outside the liquefied layer embedded portion 31. Further, the groundwater that has entered the second drain material 30 is discharged to the first drain material 20 through the surface buried portion 32 and finally flows to the sewer. Thus, since the groundwater of the liquefied layer G1 is positively discharged to the outside of the ground G, the liquefaction phenomenon of the ground G can be prevented.

  In addition, when it rains, rainwater or the like poured on the ground G is collected into the trench portion 10 through the garden soil 12, the lawn 13, and the fine sand 11, and the collected rainwater or the like is collected in the first drain material 20. Flows in. In addition, since rainwater or the like flowing into the first drain material 20 is filtered by the garden soil 12, the lawn 13, and the fine-grained sand 11, it is further filtered by the filter function of the first drain material 20, It becomes clean rainwater that contains almost no soil particles. The clean rainwater or the like reaches the liquefied layer buried portion 31 through the surface buried portion 32 of the second drain material 30, and is discharged from the liquefied layer buried portion 31 having water permeability to the liquefied layer G1. At this time, the clean rainwater or the like is liquefied by extruding soil particles or the like adhering to the outside of the liquefied layer buried portion 31 due to, for example, fluctuations in water pressure due to minute vibrations or the like to the liquefied layer G1 side. The layer burying part 31 is washed.

The present embodiment has the following effects.
(1) Since the filtered beautiful rainwater or the like passes through the first drain material 20 and the second drain material 30 and is discharged from the liquefied layer burying portion 31 to the liquefied layer G1 side, for example, due to minute vibrations or the like Soil particles adhering to the outer periphery of the liquefied layer buried portion 31 due to water pressure fluctuation or the like can be pushed out to the liquefied layer G1 side, and clogging of the liquefied layer buried portion 31 can be prevented. At this time, since clean rainwater or the like enters the liquefied layer G1, the groundwater in the liquefied layer G1 can be circulated, and the groundwater can be kept clean. According to this embodiment, this state is maintained over many years under natural circulation.

  (2) Since the liquefied layer buried portion 31 always maintains a good water permeability, the ground water of the liquefied layer G1 is drained by the second drain material 30 and the first drain material 20 installed in the ground G. It can be reliably discharged to the outside of the ground G, and the liquefaction phenomenon of the ground G when an earthquake occurs can be prevented.

  (3) Since the first drain material 20 and the liquefied layer buried portion 31 are made of a fiber material made of polypropylene, and the surface layer buried portion 32 is made of a resin such as polyvinyl chloride, the drain materials 20, 30 Corrosion and rust do not occur.

  (4) Since the branch pipe 40 is provided with the detachable lid member 42, the inside of the second drain member 30 is cleaned or inspected as necessary by detaching the lid member 42 from the branch pipe main body 41. can do. For example, by selecting one or several second drain members 30 at positions that do not interfere with the house 100 and inspecting the selected second drain members 30, Maintenance can be easily performed.

  (5) Since the trench part 10 is formed in the outer periphery of the house 100, the present liquefaction prevention structure 1 can be constructed later on an existing house.

  (6) Since clogging of the liquefied layer burying portion 31 can be naturally prevented by rainwater or the like, the liquefaction preventing structure 1 that has not been constructed so much in conventional houses can be easily applied to ordinary houses.

  (7) In the second drain material 30, water permeability is ensured only in the liquefied layer burying portion 31 embedded in the liquefied layer G1, so that groundwater is discharged more than necessary from the surface layer G2, etc., which is not subject to the liquefaction phenomenon. Therefore, the settlement of the house 100 can be prevented.

In addition, this invention is not limited to the said embodiment. In the said embodiment, although the trench part 10 was formed only in the outer periphery of the house 100, for example, when there are many amounts of groundwater, you may form in the lower side of the house 100. Moreover, in the said embodiment, although the water-permeability coefficient of the liquefied layer embedding part 31 was 10 ^{< -3} > (cm / sec) or more and the average water-permeability coefficient was about 10 ^<-2 > (cm / sec), a water-permeability coefficient becomes object. If it is larger than the liquefied layer G1, it will not be limited to such a numerical value. Moreover, in the said embodiment, although the liquefied layer embedding part 31 of the 1st drain material 20 and the 2nd drain material 30 was comprised with the fiber material made from a polypropylene, you may comprise with resin other than a polypropylene. Moreover, in the said embodiment, although the building was set as the house 100, it may not be a house.

It is a longitudinal section showing signs that liquefaction prevention structure 1 concerning one embodiment of the present invention was built in ground G. It is the II-II top view of FIG. It is a longitudinal cross-sectional view which expands and shows the A section of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquefaction prevention structure 10 Trench part 11 Fine grain sand 12 Garden soil 13 Lawn 20 1st drain material 30 2nd drain material 31 Liquefaction layer buried part 32 Surface layer buried part 40 Branch pipe 41 Branch pipe main body 42 Cover material 100 Housing G Ground G1 Liquefaction layer G2 Surface layer

Claims (6)

In the ground that has a liquefied layer that can cause a liquefaction phenomenon and a surface layer on the ground surface side than the liquefied layer, and supports the building on the surface layer, the groundwater is discharged from the liquefied layer at the time of an earthquake, A liquefaction prevention structure for preventing liquefaction of the liquefied layer,
A trench portion that is provided in the surface layer and is filled with coarse-grained soil to collect rainwater and the like,
A first drain material embedded in the trench portion in a substantially horizontal direction and having water permeability;
A second drain material connected to the first drain material and embedded in the depth direction to the liquefied layer;
The second drain material is a liquefaction prevention structure characterized in that at least a liquefied layer embedded portion embedded in the liquefied layer has water permeability. In the liquefaction prevention structure according to claim 1,
The liquefaction prevention structure characterized in that a water permeability coefficient of the liquefied layer buried portion is 10 ⁻³ (cm / sec) or more. In the liquefaction prevention structure according to claim 1 or 2,
The liquefaction prevention structure characterized in that the liquefied layer burying portion of the first drain material and the second drain material includes a fiber material made of synthetic resin. In the liquefaction prevention structure in any one of Claims 1-3,
A connection member for connecting the first drain material and the second drain material;
A liquefaction prevention structure, wherein a detachable lid member is attached to a surface layer side of the connection member.   The liquefaction prevention structure according to any one of claims 1 to 4, wherein the trench portion is formed in at least one of a periphery of the building and a lower side of the building. Liquefaction prevention structure. The liquefaction prevention structure according to any one of claims 1 to 5, wherein the building is a house.

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