Drainage and embankment structures

Abstract

To reduce a discharge amount of rainwater permeation water containing pollutant flowing out of a banking structure using a banking material containing pollutant.SOLUTION: A drainage structure is provided in a banking structure comprising a banking body constructed by leveling and compacting a banking material containing pollutant. The drainage structure comprises: an upper face drainage layer laminated on an upper face of the banking body; and a down pipe at least upper end of which is connected with the upper face drainage layer so that water can pass. In a boundary face between the upper face drainage layer and the banking body, a capillary barrier is formed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drainage structure to be provided in an embankment structure using embankment material containing pollutants, and to the embankment structure. [Background technology]

[0002] Traditionally, embankment structures have been constructed using soil and sand generated from construction sites, which contain pollutants such as heavy metals and organic chlorine compounds, as embankment materials. Since rainwater seeps into such embankment structures and generates contaminated water, measures to prevent rainwater seepage have been taken on the top and slopes. However, it is difficult to completely prevent rainwater seepage. For this reason, various countermeasures have been taken for embankment structures, such as mixing neutralizing materials into the embankment materials or setting up separate treatment facilities to collect and neutralize the generated contaminated water.

[0003] In this context, Patent Document 1 discloses a drainage structure that includes a perforated pipe surrounded by a neutralizing material, which is installed in an embankment structure constructed using excavation waste that contains acidic water-generating substances generated during the construction of a tunnel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-242451 A Summary of the Invention [Problem to be solved by the invention]

[0005] According to Patent Document 1, when rainwater penetrates the embankment material during rainfall and generates acidic water, this acidic water is neutralized by a neutralizing agent and then led to a perforated pipe and drained outside the embankment, eliminating the need to install a separate neutralization treatment facility, etc. However, since the structure is based on the premise that rainwater will penetrate the embankment material, depending on the amount of rainfall, a large amount of acidic water may be generated, which may leak out of the embankment.

[0006] The present invention has been made in consideration of such problems, and its main objective is to reduce the amount of rainwater infiltration water containing pollutants that flows out from embankment structures that use embankment materials containing pollutants. [Means for solving the problem]

[0007] In order to achieve this object, the drainage structure of the present invention is a drainage structure provided in an embankment structure having an embankment body constructed by spreading and compacting an embankment material containing a pollutant, the drainage structure comprising an upper surface drainage layer laminated on the upper surface of the embankment body; A lower surface drainage layer is laminated on the lower surface side of the embankment body, and the upper surface drainage layer and the lower surface drainage layer are connected to each other so that water can pass through the lower surface drainage layer by penetrating the embankment body. and a vertical gutter, and a capillary barrier is formed at the interface between the upper drainage layer and the embankment body.

[0008] According to the drainage structure of the present invention, a capillary barrier is formed at the boundary between the upper drainage layer and the vertical gutter and the embankment body. Therefore, most of the rainwater that flows into the embankment structure is retained by the upper drainage layer and flows down the vertical gutter along the boundary with the embankment body, and is efficiently drained. This makes it possible to significantly reduce the amount of rainwater that permeates the embankment body, and also to reduce the amount of rainwater infiltration water containing pollutants that is generated when rainwater permeates the embankment body.

[0009] The drainage structure of the present invention is a drainage structure provided in an embankment structure having an embankment body constructed by spreading and compacting embankment material containing pollutants, Upwards A laminated upper drainage layer; A lower surface drainage layer is laminated on the lower surface side of the embankment body, and the upper surface drainage layer and the lower surface drainage layer are connected to each other so that water can pass through the lower surface drainage layer by penetrating the embankment body. The embankment is characterized in that it comprises a vertical gutter and an intermediate layer provided between the embankment body and the upper drainage layer in contact with the vertical gutter, and a capillary barrier is formed at the interface between the upper drainage layer and the intermediate layer.

[0010] According to the drainage structure of the present invention, a capillary barrier is formed at the interface between the upper drainage layer and the intermediate layer, which are stacked above the embankment body, so that it is possible to more reliably suppress the infiltration of rainwater into the embankment body and reduce the amount of rainwater infiltration water containing pollutants.

[0011] The drainage structure of the present invention is characterized in that a low permeability layer is provided between the intermediate layer and the embankment body, or a capillary barrier is formed at the interface between the intermediate layer and the embankment body.

[0012] According to the drainage structure of the present invention, when an unexpected event occurs, such as the rainfall intensity being higher than expected, and the amount of rainwater held in the upper drainage layer increases, causing the capillary barrier formed at the boundary between the upper drainage layer and the intermediate layer to disappear, it becomes possible for the rainwater that has flowed from the upper drainage layer into the intermediate layer to flow quickly down along the impermeable layer to the downspout. Alternatively, it becomes possible for the rainwater that has flowed in from the upper drainage layer to be held in the intermediate layer and to flow down along the boundary with the embankment body to the downspout.

[0013] The embankment structure of the present invention is characterized by comprising the drainage structure of the present invention and an embankment body constructed by spreading, leveling and compacting embankment material containing pollutants.

[0014] According to the embankment structure of the present invention, the drainage structure having the upper drainage layer and the vertical gutter of the present invention can be used to reduce the amount of rainwater seepage water containing pollutants caused by rainwater seeping into the embankment body. This makes it possible to prevent groundwater containing pollutants at concentrations exceeding environmental standards (standards related to groundwater pollution based on the provisions of the Basic Law for the Environment) from flowing out from the embankment structure. Effect of the Invention

[0015] According to the present invention, a capillary barrier is formed at the boundary surface between an upper drainage layer provided above the embankment body and the embankment body or the intermediate layer, and a vertical gutter through which water can flow is provided between the upper drainage layer and the intermediate layer.This simple structure makes it possible to reduce the amount of rainwater infiltration water containing pollutants that flows out from embankment structures that use embankment materials containing pollutants. [Brief description of the drawings]

[0016] [Figure 1]FIG. 1 is a diagram showing a first example of an embankment structure and a drainage structure in an embodiment of the present invention. [Diagram 2] 11A to 11C are diagrams showing the results of verification of the effect of the drainage structure in the embodiment of the present invention, and a soil moisture characteristic curve. [Diagram 3] FIG. 11 is a diagram showing a second example of a drainage structure in an embodiment of the present invention. [Figure 4] 1 is a diagram showing how the water-proofing performance imparted to the drainage structure in an embodiment of the present invention disappears. FIG. [Diagram 5] FIG. 11 is a diagram showing a third example of a drainage structure in an embodiment of the present invention. [Figure 6] FIG. 11 is a diagram showing a drainage structure according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention relates to an embankment structure and a drainage structure to be provided in the embankment structure, which are suitable for use when soil containing contaminants such as heavy metals and organic chlorine compounds is used as an embankment material. The details of the structure will be described below with reference to Figs. 1 to 6.

[0018] As shown in Fig. 1(a), an embankment structure 1 comprises an embankment body 2 constructed by repeatedly spreading embankment material in layers and compacting and rolling it. A paving work 3, for example asphalt, is provided on the top of the embankment structure 1, and a slope protection work 4 is provided on the slope together with a waterproofing measure such as a waterproof sheet.

[0019] Tunnel excavation debris that may contain pollutants such as heavy metals and organic chlorine compounds is used as the embankment material that constitutes the embankment body 2. The embankment material may be the tunnel excavation debris used as is, or may be appropriately adjusted on-site by mixing it with other materials depending on the application of the embankment structure 1.

[0020] <<Drainage structure (first embodiment)>> Inside the embankment structure 1 having the above-mentioned configuration, as shown in Figure 1(a), a drainage structure 10 is provided for draining moisture such as rainfall (hereinafter referred to as rainwater) flowing in from the paving work 3 and its vicinity.

[0021] The drainage structure 10 comprises an upper drainage layer 11 stacked on the upper side of the embankment body 2, a lower drainage layer 12 stacked on the lower side of the embankment body 2, and a vertical gutter 13 that is arranged to penetrate the embankment body 2 and connects the upper drainage layer 11 and the lower drainage layer 12 to allow water to pass through.

[0022] The upper drainage layer 11 is a fine-grained layer constructed by compacting fine-grained materials, and the fine-grained materials are preferably soil materials such as high-quality sand, sand mixed with fine particles, or sand mixed with gravel, which are generally widely used as drainage materials. However, the fine-grained materials are not limited to these, and materials used as substitutes for soil materials and granular bodies having grain sizes similar to these may also be used.

[0023] The fine-grained layer is constructed by using fine particles smaller in diameter than the soil particles in at least the vicinity of the portion of the embankment body 2 that contacts the upper drainage layer 11. The upper drainage layer 11 having such a configuration has an interface B1 with the embankment body 2 formed as an inclined surface that slopes downward from the slope protection work 4 toward the downspout 13. The gradient of the interface B1 will be described later.

[0024] The vertical gutter 13 is a columnar body whose upper end is connected to the upper drainage layer 11 so that water can flow through it, and like the upper drainage layer 11, soil materials such as high-quality sand, sand mixed with fine particles, or sand mixed with gravel, or granular materials having a particle size similar to these, can be used.

[0025] In Fig. 1(a), the vertical gutter 13 is provided in the center of the embankment structure 1, but the position is not limited thereto, and it may be disposed shifted to the left or right in the transverse direction. The number of vertical gutter may also be, for example, such that multiple gutters are provided at intervals in the transverse direction. Furthermore, as shown in Fig. 1(b), the vertical gutter 13 may be provided in multiple gutters at intervals in the longitudinal direction like a so-called sand pile, or may be formed as a wall that is continuous in the longitudinal direction of the embankment structure 1.

[0026] The lower drainage layer 12 drains rainwater flowing down the vertical gutter 13 and rainwater that has permeated the embankment body 2, and in this embodiment, a fine-grained layer made of the same material as the upper drainage layer 11 and the vertical gutter 13 is used. Note that the material used for the lower drainage layer 12 does not necessarily have to be the same as that of the upper drainage layer 11 and the vertical gutter 13, and any permeable material with high permeability can be used.

[0027] As shown in Fig. 1(a), in the drainage structure 10 having the above configuration, a water-impermeable layer called a capillary barrier is formed at the interface B1 between the upper drainage layer 11 and the embankment body 2. As a result, most of the rainwater that flows into the embankment structure 1 is retained by the upper drainage layer 11, then flows down along the interface B1 with the embankment body 2 to the downpipe 13, and is efficiently drained to the lower drainage layer 12. This makes it possible to significantly reduce the amount of rainwater that permeates into the embankment body 2, and therefore to reduce the amount of rainwater infiltration water containing pollutants that is generated when rainwater permeates into the embankment body 2.

[0028] The capillary barrier is generally known as a phenomenon that occurs when the suction of the lower layer is relatively low in an unsaturated state, and rainwater is retained in the upper layer and does not permeate into the lower layer. The embankment material that constitutes the embankment body 2 is, of course, a mixture of materials with various particle sizes. Therefore, the fine particles contained in the fine layer that constitutes the upper drainage layer 11 do not all need to be smaller in diameter than the soil particles in the vicinity of the part of the embankment body 2 that contacts the upper drainage layer 11.

[0029] In other words, it is sufficient that the embankment body 2 is constructed so that when rainwater flows into the upper drainage layer 11, the suction acting between soil particles can be maintained in a state that exceeds the suction acting between soil particles at least in the vicinity of the part of the embankment body 2 that contacts the upper drainage layer 11. Suction is the force that sucks up water, and in the pores of unsaturated soil, it acts as a negative pressure against atmospheric pressure.

[0030] The magnitude of suction can be controlled by the particle size of the soil particles and the distance between the soil particles (compaction), and the smaller the particle size of the soil particles and the smaller the distance between the soil particles (better compaction), the greater the suction that is likely to occur. Therefore, the upper drainage layer 11 may be constructed by appropriately adjusting the particle size of the fine particles used and the degree of compaction according to the condition of the area near the part of the embankment body 2 that contacts the upper drainage layer 11.

[0031] <<<Effectiveness verification of the drainage structure (first embodiment)>>> A model experiment was conducted to confirm the effectiveness of the above-mentioned drainage structure 10. In the experiment, as shown in Figure 2(a), silica sand was used for the upper drainage layer 11 and the vertical gutter 13, and the upper drainage layer 11 was compacted at a moisture content of 9.6% and the vertical gutter 13 at a moisture content of 11.2%. In addition, crushed stone with a larger diameter than the silica sand was used for the embankment body 2, and this was compacted at a moisture content of 3.2%.

[0032] The suction pressure during model creation was set to 3kPa for the silica sand and 2kPa for the crushed stone. Water was sprayed onto the top of the model thus created to simulate rainfall. The water was sprayed at a rainfall intensity not exceeding 36mm / h. Rainfall intensity refers to the amount of rainfall (mm / h) converted per unit time, for example, per hour.

[0033] As a result, as shown in Figure 2(b), up until 1.5 hours after watering, the amount of water collected from the crushed stone side, which represents the embankment body 2, was greater than the amount of water collected from the silica sand side, which represents the upper drainage layer 11 and the vertical gutter 13. However, from 2 hours after watering, the amount of water collected from the silica sand side increased, and the cumulative amount of water collected 4 hours after watering was about 109 mL from the silica sand side and about 4 mL from the crushed stone side.

[0034] This can be assumed to be because as soon as the moisture content began to rise near the top surface of the crushed stone, which represents the main embankment body 2, the suction fell below that acting on the silica sand, which represents the top drainage layer 11, and a capillary barrier was formed two hours after watering. Furthermore, looking at the soil moisture characteristic curve shown in Figure 2(d), the silica sand, which represents the top drainage layer 11, has a stable capillary region (water retention region) with a small range of potential fluctuation. On the other hand, the crushed stone, which represents the main embankment body 2, has a large range of potential fluctuation, and as the moisture content rises, its potential suddenly decreases, and it loses its water retention capacity.

[0035] As a comparative example, Fig. 2(c) shows the results of a water sprinkling experiment in which a model similar to Fig. 2(a) was created, crushed stone was used for the upper drainage layer 11 and the vertical gutter 13, silica sand was used for the embankment body 2, and a low-permeability layer was provided between the upper drainage layer 11 and the embankment body 2. The water sprinkling was performed at a rainfall intensity not exceeding 24 mm / h.

[0036] Figure 2(c) shows that the amount of water collected (cumulative) from the silica sand, which represents the embankment body 2, increases more than from the crushed stone, which represents the upper drainage layer 11 and the vertical gutter 13, with each passing day since the start of watering. Then, on the 55th day after the start of watering, the amount of water collected from the silica sand, which represents the embankment body 2, was 114,850 mL, accounting for approximately 80% of the total amount of water sprayed. In other words, when the rainfall intensity is small enough not to exceed 24 mm / h, it can be assumed that the water retained in the crushed stone, which represents the upper drainage layer 11, gradually seeps into the impermeable layer on the top surface of the embankment body 2, and then seeps into the silica sand, which represents the embankment body 2.

[0037] <<Drainage structure (second embodiment)>> In the drainage structure 10, the capillary barrier does not necessarily have to be formed at the interface B1 between the upper drainage layer 11 and the embankment body 2, so long as it is formed above the embankment body 2. For example, as shown in Fig. 3, an intermediate layer 14 may be provided between the upper drainage layer 11 and the embankment body 2, and a capillary barrier may be formed at the interface B2 between the intermediate layer 14 and the upper drainage layer 11.

[0038] The intermediate layer 14 is a coarse-grained layer constructed by compacting coarse grains, and is constructed by using coarse grains larger in diameter than the fine grains used in the upper drainage layer 11. In this embodiment, a crushed stone layer made by compacting crushed stone is used as the coarse-grained layer, but the coarse-grained layer is not limited to this. For example, soil materials such as high-quality gravel, gravel mixed with fine grains, gravel mixed with sand, and gravel are suitable. In addition, the intermediate layer 14 is not limited to this, and a material used as a substitute for soil materials and having a granular body with a particle size similar to these may be used. The boundary surface B2 between the upper drainage layer 11 and the intermediate layer 14 is also formed on an inclined surface that slopes downward from the slope protection work 4 toward the downpipe 13.

[0039] As a result, after rainwater flows into the embankment structure 1 from the paving work 3 during rainfall, most of the rainwater is retained in the upper drainage layer 11 and flows down to the downpipe 13 along the boundary surface B2 with the intermediate layer 14. Therefore, there are no restrictions between the intermediate layer 14 and the embankment body 2. For example, as shown in Figure 3, the embankment material constituting the embankment body 2 may be smaller in diameter than the crushed stone layer used as the intermediate layer 14.

[0040] <<Drainage structure (third embodiment)>> However, when the rainfall intensity is high (specifically, when it exceeds about 36 mm / h), there is a risk that the capillary barrier formed at the boundary surface B2 between the upper drainage layer 11 and the intermediate layer 14 will disappear before the downspout 13, as shown in Figure 4. This is a phenomenon caused by an increase in the flow rate of rainwater flowing down along the boundary surface B2 in the upper drainage layer 11, which increases the degree of saturation. If the capillary barrier disappears, the rainwater will flow down into the intermediate layer 14, and may eventually seep into the embankment body 2.

[0041] 5, a low-permeability layer 15 is provided between the intermediate layer 14 and the embankment body 2 to prevent rainwater from seeping into the embankment body 2. The low-permeability layer 15 may be formed of any material and by any means, but for example, it is preferable to spread a ground material containing a large amount of fine particles, such as clay soil, on the upper surface of the embankment body 2 and compact it to form a layer.

[0042] As shown in the comparative example of Fig. 2(c), since the impermeable layer 15 also has water permeability, if rainwater that has flowed down the intermediate layer 14 remains on the impermeable layer 15 for a long period of time, there is a risk that the rainwater will seep through the impermeable layer 15 into the embankment body 2. For this reason, the interface between the intermediate layer 14 and the impermeable layer 15 should be provided with a predetermined gradient so that the rainwater that has flowed down the intermediate layer 14 can efficiently flow down the downspout 13, and should be formed as an inclined surface that slopes downward from the slope protection work 4 toward the downspout 13.

[0043] As a result, even if the capillary barrier formed at the boundary surface B2 between the intermediate layer 14 and the upper drainage layer 11 disappears, rainwater flowing from the upper drainage layer 11 to the intermediate layer 14 can be efficiently caused to flow down to the vertical gutter 13 along the boundary surface with the impermeable layer 15 within the intermediate layer 14, and can be quickly drained into the lower drainage layer 12.

[0044] As described above, the drainage structure 10, which has three layers, the impermeable layer 15, the intermediate layer 14, and the upper drainage layer 11, on the upper surface of the embankment body 2, drains rainwater to the downpipe 13 using the upper drainage layer 11 and the intermediate layer 14 when the rainfall intensity is low. Also, when the rainfall intensity is high and the capillary barrier formed at the boundary surface B2 between the intermediate layer 14 and the upper drainage layer 11 disappears, the rainwater can be drained using the intermediate layer 14 and the impermeable layer 15. Therefore, it is possible to make the drainage structure 10 a structure that can handle rainfall intensities of about 5 to 70 mm / h.

[0045] The above-mentioned phenomenon of the capillary barrier formed at the boundary surface B2 between the upper drainage layer 11 and the intermediate layer 14 disappearing may also occur when the distance between the boundary surface B2 between the upper drainage layer 11 and the intermediate layer 14 is long. This is also the case when a capillary barrier is formed at the boundary surface B1 between the upper drainage layer 11 and the embankment body 2 as shown in Figure 1. In this case, it is also possible to lengthen the effective range of the capillary barrier by appropriately adjusting the gradient of the boundary surfaces B1 and B2 to be small.

[0046] <<Drainage structure (fourth embodiment)>> In Fig. 5, an example is shown in which an impermeable layer 15 is provided between the intermediate layer 14 and the embankment body 2 in case the capillary barrier formed at the boundary surface B2 between the intermediate layer 14 and the upper drainage layer 11 disappears. However, this is not limited to this, and two layers of capillary barriers may be formed in the drainage structure 10 as shown in Fig. 6.

[0047] Specifically, the coarse-grained layer constituting the intermediate layer 14 is constructed using coarse-grained material that is larger in diameter than the fine-grained material used in the upper drainage layer 11, but smaller in diameter than the soil particles in at least the vicinity of the portion of the embankment body 2 that comes into contact with the intermediate layer 14.

[0048] In this way, even if the capillary barrier formed at the interface B2 between the upper drainage layer 11 and the intermediate layer 14 disappears and rainwater flowing down the upper drainage layer 11 flows into the intermediate layer 14, the water will be retained in the intermediate layer 14 and can be drained into the vertical gutter 13 along the interface B3 between the intermediate layer 14 and the embankment main body 2, thereby making it possible to suppress the phenomenon of rainwater seeping into the embankment main body 2.

[0049] As mentioned above, the capillary barrier is formed when the suction of the lower layer is relatively low in the unsaturated state. Therefore, the intermediate layer 14 can also be constructed by appropriately adjusting the particle size of the coarse particles and the degree of compaction according to the condition of the part of the embankment body 2 adjacent to the intermediate layer 14.

[0050] According to the embankment structure 1 of the present invention, the drainage structure 10 can be used to reduce the amount of rainwater seepage water containing pollutants that occurs when rainwater seeps into the embankment body 2. This makes it possible to prevent groundwater containing pollutants at concentrations that exceed environmental standards (standards related to groundwater pollution based on the provisions of the Basic Law for the Environment) from flowing out from the embankment structure 1.

[0051] The embankment structure 1 and the drainage structure 10 of the present invention are not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0052] For example, in this embodiment, an example is given of constructing the embankment body 2 using embankment materials including tunnel excavation mud, but this is not necessarily limited to this, and the embankment materials may also include construction waste soil generated during ground excavation and other construction work.

[0053] Furthermore, the embankment structure 1 on which the drainage structure 10 is provided can be applied to earth structures constructed for any purpose, such as road embankments, railway embankments, river levees, site development, housing development, and landfill. [Explanation of symbols]

[0054] 1 Embankment structures 2. Embankment body 3. Pavement Work 4. Slope protection works 10 Drainage structure 11 Top drainage layer 12 Bottom drainage layer 13 Downspout 14 Middle Class 15 Impervious layer B1 Boundary (upper drainage layer and embankment body) B2 Boundary (upper drainage layer and middle layer) B3 Boundary (intermediate layer and embankment body)

Claims

1. A drainage structure provided in an embankment structure having an embankment body constructed by spreading and compacting embankment material containing pollutants, An upper surface drainage layer laminated on the upper surface of the embankment body; A lower drainage layer laminated on the lower surface side of the embankment body; A vertical gutter penetrating the embankment body and connecting the upper drainage layer and the lower drainage layer in a water-permeable manner, A drainage structure characterized in that a capillary barrier is formed at the interface between the upper drainage layer and the embankment body.

2. A drainage structure provided in an embankment structure having an embankment body constructed by spreading and compacting embankment material containing pollutants, An upper drainage layer laminated above the embankment body; A lower drainage layer laminated on the lower surface side of the embankment body; A vertical gutter penetrating the embankment body and connecting the upper drainage layer and the lower drainage layer in a water-permeable manner; An intermediate layer is provided between the embankment body and the upper surface drainage layer in contact with the vertical gutter, A drainage structure, characterized in that a capillary barrier is formed at the interface between the upper drainage layer and the intermediate layer.

3. The drainage structure according to claim 2, A drainage structure characterized in that a low-permeability layer is provided between the intermediate layer and the embankment body.

4. The drainage structure according to claim 2, A drainage structure characterized in that a capillary barrier is formed at the interface between the intermediate layer and the embankment body.

5. The drainage structure according to any one of claims 1 to 4, An embankment body constructed by spreading and compacting embankment material containing contaminants; An embankment structure comprising:

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