JP4578340B2 - Embankment - Google Patents

Description

  The present invention relates to a bank body such as a river bank.

  The river embankment has a structure whose main purpose is to prevent river flooding. River inundation occurs when river embankments break down. River embankments break down due to erosion by rivers. Therefore, it is important that the river bank has a structure that eliminates erosion from the front slope, which is the river side of the river bank. Therefore, the structure of the dam body emphasizes waterproofness. For example, on the front side slope of the embankment embankment that is the foundation part of the embankment, a revetment structure consisting of a composite structure of a water shielding sheet and concrete is used to prevent the infiltration of water into the embankment embankment. The structural form is taken.

  FIG. 8 is a view for explaining the structure of a conventional bank body. The bank body in FIG. 8 is in contact with the front surface 11 of the bank body embankment 10 to form a bank protection structure 20.

As the bank embankment 10, a material having low water permeability, for example, a water permeability coefficient of 1.0 × 10 ⁻⁷ to 10 ⁻⁴ cm / sec is used. The revetment structure 20 formed on the front slope 11 of the bank embankment 10 has, for example, a cross-sectional structure as shown in FIG.
The revetment structure 20 includes a water shielding sheet 21, concrete 22, topsoil 23, and turf 24 from the side in contact with the front side slope 11 of the bank embankment 10. As the water-impervious sheet 21, for example, a sheet having a water permeability of 1.0 × 10 ⁻¹³ to 10 ⁻¹¹ cm / sec is used. The concrete 22 is formed by a connecting block or the like. The topsoil 23 is improved to a soil where the turf 24 is easy to grow, and the turf 24 prevents the topsoil 23 from flowing out. Such a revetment structure 20 prevents infiltration of water from the river to the bank embankment 10.

  Such a bank is in contact with the river at the front slope 11. In FIG. 8, a one-dot dashed line represents the position of the water surface of the river, H1 represents the water surface when the water level is low, and H2 represents the position of the water surface when the water level is high. Even if such a bank embankment 10 forms the revetment structure 20 which attached importance to waterproofing in the front side slope 11, water may infiltrate by various factors.

  In FIG. 8, a two-dot dashed line represents an infiltration line that is a residual water level when water infiltrates into the bank embankment 10, HI1 is an infiltration line at a low water level H1, and HI2 is an infiltration at a high water level H2. Represents a line. The water that has infiltrated the bank embankment 10 flows out from the bank protection structure 20 or from below the bank bank 10.

  When the stability of the levee body is obtained, it is important to quickly lower the residual water level in the dam body when the water level of the river changes from the high water level H2 to the low water level H1, for example. Since the amount of water flowing out from the lower side of the levee body is limited, it is important to quickly flow out water from the water shielding sheet 21.

  When the water is infiltrated, the portion of the levee embankment 10 becomes fragile, and when water flows out from between the water-impervious sheet 21 of the levee embankment 10 and the revetment structure 20, the surface of the embankment embankment 10 at the same time. It may be scraped off. When the bank body embankment 10 is cut, a gap is generated between the bank body bank 10 and the water shielding sheet 21 of the bank protection structure 20. Such a gap causes damage to the water shielding sheet 21. The breakage of the water-impervious sheet 21 causes an increase in the amount of water infiltrated into the bank body embankment 10. As a result, when the embankment embankment 10 contains a lot of water, the embankment is likely to break, and the most important function of preventing river flooding may not be performed.

  In view of the above problems, an object of the present invention is to provide a bank having a structure in which a gap is not easily generated between the bank embankment and the water shielding sheet.

The embankment of the present invention that solves the above problems has a water-permeable sheet having air permeability laid on at least the front slope of the bank embankment formed of a predetermined embankment material. The gas between the embankment embankment and the water-impervious sheet is configured to be vented to the outside.
Such a dam body allows the air between the embankment embankment and the water impervious sheet to pass through the water impervious sheet so that, for example, the air accumulated between the embankment embankment and the impermeable sheet can be extracted to the outside. become able to. Since air can be extracted, generation of unnecessary gaps between the embankment embankment and the water-impervious sheet is suppressed, and even if gaps are generated, the air can be quickly removed and the gaps can be eliminated. Therefore, various conventional problems caused by a gap between the bank embankment and the water shielding sheet can be solved. Further, even when a gap is generated between the embankment embankment and the water-impervious sheet when laying the water-impervious sheet, the air can be extracted from the gap after laying, so that the laying operation becomes easier than before. In addition, when the river level drops, air flows into the embankment embankment quickly, so saturated water in the embankment embankment moves quickly and is installed at the bottom of the embankment embankment. It is easy to drain the infiltrated water from the drainage section for discharging the water inside the bank embankment to the outside and the surface of the bank embankment.

The said water shield sheet used for embankment of the present invention may be a sheet of breathable example ^{220m 3 / m 2 / 24h~1200m 3} / m 2 / 24h. In addition, a sheet having a water permeability coefficient of, for example, 7.7 × 10 ⁻⁹ cm / sec to 8.6 × 10 ⁻⁵ cm / sec can be used.

  Such a dam body can prevent the inflow of water into the embankment embankment when the river has a normal amount of water if the impermeable sheet is laid on the front slope side. When the amount of water exceeds the height of the levee body, water flows from the portion other than the front slope of the embankment embankment. In order to prevent this, the water shielding sheet may be further laid on the rear slope of the bank embankment. If a water-impervious sheet is also laid on the backside slope, water infiltration from the backside slope to the embankment embankment during rainfall can be prevented, and the elasticity of the embankment embankment can be reinforced.

Moreover, the bank body of this invention may be the structure which further provided the nonwoven fabric on the said water shielding sheet. With this nonwoven fabric, the liquid flowing out from the bank body embankment is discharged through the water shielding sheet. Since the water-impervious sheet of the present invention has a higher water permeability coefficient than that of conventionally used water-impervious sheets, the amount of water that oozes from the bank embankment is greater than that of the conventional one. Therefore, if concrete is provided on the water-impervious sheet as in the conventional case, the influence of water on the concrete is likely to occur. In addition, since the concrete itself is heavy, the embankment embankment itself may be deformed. In this embodiment, by laying a non-woven fabric in place of concrete on the water-impervious sheet, liquid such as water exuding from the water-impervious sheet can be quickly discharged, and by using conventional concrete The problem can be solved.
The nonwoven fabric has a water permeability coefficient of, for example, 1.0 × 10 ⁻² cm / sec to 1.0 cm / sec.

Furthermore, a top soil may be piled up on the nonwoven fabric, and a plant for preventing the top soil from flowing out may be planted on the top soil. The plant is turf or the like, and it is possible to prevent the topsoil from flowing out by running water by rooting the topsoil. Since the water shielding sheet is excellent in air permeability, it is favorable for the growth of plants. Moreover, the beauty can be maintained by the plant.
Conventionally, in order to use concrete, it was necessary to carry out in order from laying a water-impervious sheet to planting. However, when the structure from the water-impervious sheet to the plant is integrated, it can be laid at a time and the construction is easier than before.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a view for explaining the structure of a bank body according to the present embodiment. The bank body has a bank body embankment 10 and a bank protection structure 30.

The bank embankment 10 is composed of three layers from a first layer 12 to a third layer 14. The innermost first layer 12 functions as a core of the bank body embankment 10, and is formed using a bank material having the lowest water permeability. The embankment material used for the embankment embankment 10 has higher water permeability as it goes outward from the first layer 12 to the second layer 13 and the third layer 14. The water permeability coefficient of the embankment material used for the first layer 12 to the third layer 14 is, for example, 1.0 × 10 ⁻⁷ to 10 ⁻⁴ cm / sec.

  A drainage portion is formed at the lower end portion of the back slope 15 located opposite to the river side of the bank embankment 10. The drainage part is constituted by a drain part 17, a dike channel 18, and a filter part 19. In the drain portion 17, water infiltrated into the bank embankment 10 is collected. The dike channel 18 is a channel for guiding the water collected in the drain portion 17 to a predetermined flow end. The water collected in the drain part 17 is surely drained by the dike channel 18. The filter unit 19 is provided so that soil particles do not move from each layer of the bank body embankment 10 and the drain unit 17 is not clogged. The drain part 17 has a larger water permeability than the embankment material of each layer of the bank body embankment 10. Therefore, it is necessary to prevent the clogging of the drain part 17 by providing the filter part 19 between the bank embankment 10 and the drain part 17.

  The revetment structure 30 has a structure as shown in FIG. The revetment structure 30 includes a water shielding sheet 31, a non-woven fabric 32, a top soil 23, and a lawn 24 from the side in contact with the front side slope 11 of the bank embankment 10.

The water-impervious sheet 31 is composed of a fibrous sheet having a property that allows air to pass through but prevents water from passing through. Water barrier sheet 31, for example air permeability ^{220m 3 / m 2 / 24h~1200m 3} / m 2 / 24h, permeability is ^{7.7 × 10 -9 cm / sec~8.6 ×} 10 -5 cm / sec This is a fibrous sheet. For example breathable water-impervious sheet 31 is 220m ³ / ^m 2 / 24h, hydraulic conductivity is 8.6 × ¹⁰ -9 cm / sec. If the water impervious sheet 31 having such a water permeability coefficient is used, it is possible to ensure the water tightness required for the bank body. By using the water-impervious sheet 31, it is possible to eliminate variations in the water permeability coefficient of the front slope 11 of the bank embankment 10, and to ensure the waterproof performance originally required for the front slope 11.

  Since this water-impervious sheet 31 tends to allow air to pass therethrough, even when a gap is formed between the water-impervious sheet 11 and the front-side slope 11, air can escape from the gap and the gap can be quickly filled. Since the gap is filled, there is a lower risk of breakage of the water-impervious sheet 31 than in the past. Further, since the water shielding sheet 31 easily allows air to pass therethrough, it is effective for maintaining and growing a plant such as the turf 24.

  FIG. 3 is a view for explaining the structure of the water shielding sheet 31. This water shielding sheet 31 has a structure in which a ventilation / waterproof layer 33 is sandwiched between reinforcing layers 34 and 35. The ventilation / waterproof layer 33 allows air to pass through the water-impervious sheet 31, and most of the water is blocked. The reinforcing layers 34 and 35 prevent deterioration and breakage of the ventilation / waterproof layer 33 due to external factors.

  The ventilation / waterproof layer 33 is made of, for example, a polyethylene continuous ultrafine fiber nonwoven fabric having a pore diameter of about 0.5 μm, and the reinforcing layers 34 and 35 are made of, for example, a nonwoven fabric. The diameter of the water droplet is usually 1000 to 3000 μm, and the diameter of the drizzle is usually 100 to 200 μm. If the pore diameter of the ventilation / waterproof layer 33 of the water-impervious sheet 31 is the above value, the diameter of the water droplet, the diameter of drizzle, etc. are larger than the pore diameter of the ventilation / waterproof layer 33. Never pass. Therefore, the water shielding sheet 31 has a waterproof property. The diameter of water vapor is usually 0.004 μm, and the diameter of carbon dioxide gas is usually 0.0023 μm. Since these diameters are smaller than the perforated diameter of the ventilation / waterproof layer 33, they pass through the ventilation / waterproof layer 33. Therefore, the water shielding sheet 31 has air permeability.

The non-woven fabric 32 is a geotextile having an excellent drainage function, and the residual water that has flowed out from the water-impervious sheet 31 is quickly drained out of the dam body. The water permeability coefficient of the nonwoven fabric 32 on the side of the water shielding sheet 31 is, for example, 1.0 × 10 ⁻² cm / sec to 1.0 cm / sec, and has drainage performance similar to that of a sand mat. For example, the water permeability coefficient is 5.0 × 10 ⁻¹ cm / sec.

  Such a nonwoven fabric 32 is a structure which the conventional seawall structure 20 does not have. In the conventional revetment structure 20, concrete 22 is used for the portion of the nonwoven fabric 32. When concrete 22 is used, a large load is applied to the front slope 11. Since the revetment structure 20 is used in units of decades once constructed, the use of the concrete 22 tends to induce deformation of the levee body, such as subsidence of the levee body and protrusion of the front slope 11. On the other hand, when the non-woven fabric 32 is used as in the present invention, the load on the front slope 11 is drastically reduced, so that the deformation of the levee body hardly occurs and it can withstand long-term use.

  The topsoil 23 is improved to a soil where the turf 24 is easy to grow, and the turf 24 prevents the topsoil 23 from flowing out. The grass 24 is an example of a plant grown on the topsoil 23. Even plants other than the grass 24 can prevent the soil from flowing out from the topsoil 23 by rooting.

4-6 is a figure for demonstrating the laying structure of the water-impervious sheet 31.
It is rare that the water-impervious sheet 31 can cover the entire front side slope 11 of the levee body with a single sheet. For this purpose, the front slope 11 is usually covered with a plurality of water-impervious sheets 31a, 31b, 31c. The water-impervious sheet 31 is laid on the front side surface 11 as shown in FIGS.

5 is a cross-sectional view taken along the line AA ′ in FIG. 4, and FIG. 6 is a cross-sectional view taken along the line BB ′ in FIG.
FIG. 5 shows how the water shielding sheet 31 a is fixed to the upper end and the lower end of the front slope 11. As can be seen from FIG. 5, the water-impervious sheet 31 a is embedded at the upper end of the bank embankment 10 so that the end is a key shape. Further, another end portion of the water shielding sheet 31 a is embedded in the lower end of the front side slope 11 perpendicularly to the front side slope 11. The water shielding sheets 31b and 31c are also fixed in the same manner.

  The boundary portion between the water shielding sheet 31a and the water shielding sheet 31b is as shown in FIG. Here, the water-impervious sheet 31c side is upstream, and water flows from the water-impervious sheet 31c side to the water-impervious sheet 31a side. The water-impervious sheet 31a and the water-impervious sheet 31b are overlapped so that the water-impervious sheet 31b is on top. This is to prevent water from entering from the end of the water shielding sheet 31a by running water. The portion of the water-impervious sheet 31a that overlaps the water-impervious sheet 31b is embedded in the front slope 11 under the water-impervious sheet 31b. The overlapping portion of the water shielding sheet 31 a and the water shielding sheet 31 b is fixed to the front slope 11 by the fixing member 25.

  Moreover, the water-impervious sheet 31 and the nonwoven fabric 32 may be integrally formed, and these may be laid on the front slope 11 of the bank embankment 10 as shown in FIGS. In any case, as shown in FIGS. 5 and 6, the water-impervious sheets 31a, 31b, and 31c (including the nonwoven fabric when the nonwoven fabric is integrally formed) are fixed, so the ends of the respective water-impervious sheets 31a, 31b, and 31c Water does not infiltrate in large quantities from the part to the bank embankment 10 side.

  FIG. 7 is a view for explaining the structure of another embodiment of a bank body having a higher function of the bank body. In this figure, the revetment structure 40 is laid so as to cover not only the front slope 11 of the bank embankment 10 but also the back slope 15 and the top face 16 thereof. Since the structure of the bank protection structure 40 is the same as the bank protection structure 30 of FIG. 1, detailed description is abbreviate | omitted. In the levee body having such a structure, the backside slope 15 of the dam body can have the same function as the front side slope 11.

  Therefore, even if the water level is higher than the height of the levee due to an unexpected amount of water, such as during a heavy rain, the dam can be prevented from eroding due to the overflow. You can delay the breakdown of your body. In addition, it is possible to prevent water from infiltrating directly from the back slope 15 due to rain.

  The water-impervious sheet 31 used for the revetment structure 40 has a property that prevents water from passing through, but does not mean that water cannot pass completely. For example, when the amount of water in a river increases or during heavy rains. It is conceivable that water infiltrates from the front slope 11 into the bank embankment 10 although the amount is small. The embankment embankment 10 usually contains air. When water infiltrates into the bank body embankment 10, this air is compressed and becomes a mass and is pushed to the rear side slope 15 side, and the pressure is increased. Thereby, it cannot be said that there is no possibility that the revetment structure 40 is damaged. In this embodiment, since the water shielding sheet 31 of the revetment structure 40 laid on the backside slope 15 has a property of allowing air to pass through, the mass of air pushed to the backside slope 15 is affected by the water shielding sheet 31. Since the dam body embankment 10 is pulled out of the bank, it can be said that there is almost no risk of breakage of the revetment structure 40 as described above.

  Even if the revetment structure 40 is laid on the front side slope 11 and the back side slope 15 except for the revetment structure 40 on the top surface 16 of the bank embankment 10, the infiltration of water from the back side slope 15 is caused. The structure is sufficient to prevent it.

The figure for demonstrating the structure of the bank body of this embodiment. The figure for demonstrating the structure of the bank protection structure of this embodiment. The figure for demonstrating the structure of a water-impervious sheet. The figure for demonstrating the laying structure of a water-impervious sheet. The figure for demonstrating the laying structure of a water-impervious sheet. The figure for demonstrating the laying structure of a water-impervious sheet. The figure for demonstrating the structure of the bank body of another embodiment. The figure for demonstrating the structure of the conventional bank body. The figure for demonstrating the structure of the conventional revetment structure.

Explanation of symbols

10 Embankment Embankment 11 Front Side Slope 12 First Layer 13 Second Layer 14 Third Layer 15 Back Side Slope 16 Top Surface 17 Drain Portion 18 Dyke Channel 19 Filter Portion 20, 30, 40 Revetment Structure 21, 31, 31a 31b, 31c Water shielding sheet 22 Concrete 23 Topsoil 24 Lawn 25 Fixing member 32 Non-woven fabric 33 Ventilation / waterproof layer 34, 35 Reinforcement layer H1 Water surface position at low water level H2 Water surface position at high water level HI1 Low water level Infiltration line at time HI2 Infiltration line at high water level

Claims (8)

A water shielding sheet having air permeability is laid on at least the front slope of the embankment embankment formed of a predetermined embankment material,
The gas between the embankment embankment and the water shielding sheet is configured to be vented to the outside through the water shielding sheet.
Embankment. The water barrier sheet is breathable is ^{220m 3 / m 2 / 24h~1200m 3} / m 2 / 24h,
The bank body according to claim 1. The water-impervious sheet has a water permeability coefficient of 7.7 × 10 ⁻⁹ cm / sec to 8.6 × 10 ⁻⁵ cm / sec.
The bank body according to claim 1. The impermeable sheet is further laid on the back slope of the bank embankment,
The bank body according to claim 1. A nonwoven fabric is provided on the water-impervious sheet, and by this nonwoven fabric, the liquid flowing out from the bank embankment via the water-impervious sheet is discharged.
The bank body according to claim 1. The nonwoven fabric has a water permeability coefficient of 1.0 × 10 ⁻² cm / sec to 1.0 cm / sec.
The bank body according to claim 5. Topsoil is piled on the nonwoven fabric, and plants are planted on this topsoil.
The bank body according to claim 5 or 6. The water-impervious sheet, nonwoven fabric, topsoil, and plant are configured integrally.
The bank body according to claim 7.

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