JP4664091B2 - Covering structure of waste final disposal site - Google Patents

Description

  The present invention relates to a soil covering structure for a waste final disposal site.

  At the final waste disposal site, it is necessary to properly disassemble and stabilize the landfilled waste, and the landfilled waste is on the surface to prevent the waste from being scattered and spoiled. A surface layer such as a cover is finally formed on the surface of the waste so as not to be exposed. As the final earth covering method for forming this surface layer, a common earth covering method using earth or sand or a capping method using a water shielding base material such as a water shielding sheet or asphalt is selectively used.

  Conventionally, the soil covering method has a structure that utilizes, for example, a capillary barrier effect using only a ground material. This is a two-layer structure consisting of fine-grained soil such as sand in the upper layer and coarse-grained soil such as gravel in the lower layer, the difference in water retention, that is, the difference in pF value (pF value; fine-grained soil> coarse-grained soil) and the gradient. By providing it, when the water retention capacity of the fine-grained soil in the upper layer is at the limit level, lateral drainage is promoted and the amount of penetration into the waste layer is controlled.

  However, in the capillary barrier structure using only such a ground material, the barrier effect is maintained within a certain rainfall intensity, but when the rainfall intensity exceeds a certain value, the infiltration into the lower sand layer is started, and the rainfall amount ( As the rainfall intensity increases, the penetration rate into the lower part (ratio of the penetration quantity to the lower part with respect to the rainfall intensity) increases and the correlation also varies widely. It is not easy to control.

On the other hand, in combination with the soil covering method, a technique for performing a capping method using a water shielding base material such as a water shielding sheet or asphalt is disclosed in the following patent documents.
JP 2001-17933 A

  As shown in FIG. 8, a hydrodynamic gradient is attached to the bottom of the landfill area of the buried waste 10 and the lower area of the buried waste is covered with the water shielding layer 20, and the water permeable layer 16 is provided on the outer peripheral surface thereof. The water conduit 12 along the hydraulic gradient is formed inside or outside the water permeable layer 16. The upper surface of the buried waste 10 is provided with a dynamic water gradient reaching the water conduit 12 and covered with a water shielding layer 20A, and a coarse particle layer 24 having a small water retention (pF value) is formed on the water shielding layer 20A. The fine grain layer 26 having a large water retention (pF value) is provided on the upper layer of the coarse grain layer and covered with the topsoil 28.

  According to this, it is possible to greatly reduce the amount of rainfall penetrating into the buried waste 10, and it is possible to prevent the rainwater from penetrating into the waste and generating a large amount of water contaminated with harmful substances. However, in order to stabilize the waste at an early stage, it is necessary to promote decomposition of the waste by circulation of appropriate water and air. However, in the waste burying structure of Patent Document 1, the water shielding layer 20A is used. The drainage efficiency to the side is large, and rainwater hardly penetrates into the waste layer under normal rainfall intensity (about 10 mm / h), and an appropriate amount of water cannot be supplied to the waste layer.

Here, as a technique for supplying an appropriate amount of water to the waste layer, several techniques are disclosed in the following patent documents.
Japanese Patent No. 3354920 Japanese Patent Laid-Open No. 2004-73907 Japanese Patent Laid-Open No. 2004-73908

  In the final earth covering method of the waste final disposal site disclosed in Patent Document 2, the surface layer such as the soil covering is finally formed on the surface of the waste landfilled in the landfill of the waste final disposal site. A portion having water permeability and a portion having water-impervious or hardly water-permeable properties are mixed.

  Specifically, the portions having water permeability and the portions having water impermeability or hardly water permeability are alternately formed in a strip shape, and all the portions having water impermeability or hardly water permeability are formed on the inclined surface. In addition, a drainage facility is provided along the lower edge so that rainwater that falls on water-impervious or hardly water-permeable parts is drained outside the landfill as surface water. The ratio of the part having water permeability or poor water permeability is made variable according to the amount of rainfall.

  In addition, the technique described in Patent Document 3 is a rainwater storage tank installed on a permeation control layer having a predetermined thickness and a predetermined water permeability coefficient that covers the upper surface of the landfilled waste in a waste disposal site. And a final soil covering layer that covers the storage tank, and a small hole is appropriately formed on the bottom surface of the storage tank with an opening ratio, and rainwater temporarily stored in the storage tank after passing through the soil cover layer due to rain is a small hole. And, it is made to permeate into the waste with a predetermined amount of water sequentially through the permeation control layer.

  In addition, in the technology described in Patent Document 4, in the waste disposal site, a final covering soil having a gradient that slopes from the center to the periphery of the disposal site is applied to the upper surface of the landfill that has been landfilled. And a plurality of slits or small holes are formed in the water shielding sheet at a predetermined opening ratio, and a part of the rain that falls on the water shielding sheet through the slits or small holes is infiltrated into the waste through the covering soil. .

  However, the technique described in Patent Document 2 is constructed at the same time or alternately by different methods of the soil covering method and the capping method, and the workability is not good. And since only the part which has water-imperviousness or hardly water-permeability is formed in an inclined surface, it is a thing in which workability is further not good.

  In addition, the techniques described in Patent Documents 3 and 4 can adjust the amount of rainwater infiltrated into the waste, but the technique described in Patent Document 3 requires the installation of a storage tank as a structure for that purpose. The whole thing becomes big. The technology described in Patent Document 3 only requires laying a water-impervious sheet, but the water-impervious sheet is the uppermost layer and is exposed as a soil-covering structure. I can't.

In order to solve this problem, the amount of rainwater permeation can be adjusted, the workability is good, the entire equipment is not overwhelming, and the technology that prevents the water shielding sheet from being exposed to the top layer as a soil covering structure is as follows. There are techniques described in the patent literature.
Japanese Patent Application No. 2004-018126 Japanese Patent Application No. 2004-201239

  As shown in FIG. 9, the technique described in Patent Document 5 provides a large number of concave portions 18 and convex portions 13 on the entire surface on a lower layer covering material 15 laid on the waste 11. A sheet 9 having an opening 17 for infiltration of rainwater permeation and generated gas is laid on the top of the sheet, and an upper layer covering material 19 is laid on the upper surface and rolled, and the unevenness of the sheet 9 is cut into the upper and lower covering layers. It is something to make. In the figure, 8 is a seam where the unevenness of the sheet 9 is overlapped, and 7 is a surface layer material covering the upper layer covering material 19.

  According to this, since rainwater permeates from the opening provided at the top of the convex portion, it is possible to ensure the rainwater permeation adjustment function and the generated gas discharge function, and troublesome work such as forming a covering soil surface in a bowl shape when laying the sheet The sheet can be laid easily and workability is good.

  Further, as shown in FIG. 10, the technique described in Patent Document 6 includes a coarse-grained soil layer (gravel layer) 2 formed with a gradient on the waste layer 1, and the coarse-grained soil layer 2. And a breathable waterproof sheet 3 provided with a water passage formed by a plurality of scattered small holes 5, and a fine-grained soil layer (sand layer) 4 formed on the breathable waterproof sheet 3. And consist of Further, the small hole 5 is formed with a vertical rising portion 6 at the opening edge.

  Thereby, a water flow function is given to the sheet | seat provided with the capillary barrier function, and waterproofness and air permeability which are basic functions can be ensured. Further, only the vertically osmotic water in the fine-grained soil layer 4 can enter the openings of the small holes 5 and permeate downward, and the water flowing on the surface of the breathable waterproof sheet 3 is caused by the presence of the rising portions 6. Since the downward penetration from the small hole 5 is prevented, the downward penetration amount can be reliably controlled only by the area of the opening of the small hole 5. And when laying the breathable waterproof sheet 3, the work of forming the cover soil surface in a bowl shape is not required, and the breathable waterproof sheet 3 can be easily laid and the workability is good.

  However, in the technique of Patent Document 5 or Patent Document 6, in order to arrange the sheet between the covered soil layers, after covering the waste, laying the covered soil, laying the sheet from the top, and then laying the covered soil again Therefore, it can be said that there is room for further study on the reduction of the number of processes because the covering soil laying process is divided into two times during construction.

  In addition, when classifying the locally generated soil at the time of construction, it is not possible to lay the covering soil and sheets until landfill has been completed after the landfill of the waste has been completed. It can be said that there is room for improvement.

  The object of the present invention is to eliminate the inconveniences of the conventional example, can be constructed more efficiently than before, and can ensure air permeability and waterproofness with a simple structure in which a sheet is laid with the surface layer as a covering soil layer. It is another object of the present invention to provide a soil covering structure of a waste final disposal site that can control the amount of rainwater permeating into the lower waste layer by further imparting a water passing function to the sheet and obtain a stable soil covering.

In order to achieve the above object, the present invention according to claim 1 is characterized in that a water shielding sheet is laid between the waste layer and the covering soil layer with a gradient, and water and ventilation are provided in the water shielding sheet. For the purpose, the edges are raised upwards to form a cylindrical part, and the position of the opening part is formed higher than the surface of the water-impervious sheet. A coarse-grained soil layer located immediately above and a fine-grained soil layer located immediately above the coarse-grained soil layer are provided, and the boundary between the coarse-grained soil layer and the fine-grained soil layer is given a gradient, and this coarse-grained soil layer And the fine grain soil layer are positioned above the upper end of the cylindrical portion .

  According to the first aspect of the present invention, the water shielding sheet is laid with a slope, and the water shielding sheet is interspersed with openings for water flow and ventilation, and the position of the opening is determined by the water shielding sheet. Since it was formed higher than the surface, only rainwater that flows vertically into the opening penetrates into the lower waste layer during rainfall, and other rainwater is blocked by the cylindrical part without blocking into the opening. Drain sideways according to the gradient of the water sheet. That is, the amount of rainwater that permeates the waste layer can be controlled by the area of the opening.

  In addition, since the water shielding sheet is laid between the waste layer and the covering soil layer, the process of laying the covering soil layer after landfilling the waste and laying the water shielding sheet is completed in one step. Even when using locally generated soil classified as a covering soil layer, classification can be performed while laying the water-impervious sheet after landfilling the waste, and the construction work is continued until the classification work is completed. There is no need to interrupt. Thus, the amount of rainwater that permeates the waste layer can be controlled, and the work can be performed more efficiently than in the past.

  In addition, since the water-impervious sheet is not located on the surface layer and the surface layer is a covering soil layer, the covering soil structure can be greened and used as a park or the like.

  In addition to the above action, it provides a simple and reliable method for forming the position of the opening higher than the surface of the water shielding sheet. And can be set freely without changing the surrounding height.

Moreover, in addition to the rain control function by the water shielding sheet provided with the cylindrical part, the capillary barrier effect due to the difference in water retention between the coarse-grained soil layer and the fine-grained soil layer is added to control the rainfall that permeates the waste layer. Can be made even more reliable. In other words, in the case of a capillary barrier structure composed of a coarse-grained soil layer and a fine-grained soil layer, if the rainfall intensity exceeds a certain value, infiltration into the coarse-grained soil layer below starts, and the amount of infiltration into the waste layer Although it is difficult to control the amount of rainwater, it is possible to keep the amount of rainwater infiltrated into the waste layer constant regardless of the rainfall intensity by adding the rain amount adjustment function by the water shielding sheet provided with the cylindrical part. .

  And in order to acquire such a synergistic effect, since the separate member which consists of artificial materials, such as adding another water shielding sheet, is not required, it does not have a bad influence on natural environment compared with the past. For example, gravel can be used as the coarse-grained soil, and sand can be used as the fine-grained soil.

Furthermore, since the boundary between the coarse-grained soil layer and the fine-grained soil layer is located above the upper end of the cylindrical portion, first, due to the difference in water retention between the coarse-grained soil layer and the fine-grained soil layer, during the rain Due to the capillary barrier effect, the amount of rain that flows into the coarse-grained soil layer is limited, and then only rainwater that flows into the cylindrical portion permeates the waste layer. Thus, both the capillary barrier effect due to the difference and the rain amount adjusting function by the water shielding sheet provided with the cylindrical portion can be sufficiently exhibited.

The gist of the present invention described in claim 2 is that the height of the cylindrical portion is set to 2/3 or more of the height of the first covering soil layer located immediately above the water shielding sheet. .

According to the second aspect of the present invention, the height of the cylindrical portion is set to 2/3 or more of the height of the first covering soil layer located immediately above the water-impervious sheet, so that rainwater is discarded. The penetration rate into the physical layer can be stabilized. This is because when rainwater permeates into the first covering soil layer located immediately above the water-impervious sheet, even if rainwater stays in the lower part of the layer, the upper end of the tubular portion is 2 of that layer. It is considered that it is located at the upper part of the height of / 3 or more, and it is difficult for the accumulated rainwater to flow into the cylindrical part.

The gist of the present invention described in claim 3 is that the height of the cylindrical portion is 4 cm or more.

According to the third aspect of the present invention, since the height of the cylindrical portion is set to 4 cm or more, even if there is a large amount of rain and the rainwater is retained on the water shielding sheet, the retained rainwater is sufficient. It cannot easily flow in from the upper part of the cylindrical part having a height, and the rainfall adjustment function can be maintained.

  As described above, the soil covering structure of the waste final disposal site according to the present invention can be constructed more efficiently than before, and it has a simple structure in which a sheet is laid with the surface layer as a covering soil layer, providing air permeability and waterproofness. It can be ensured, and by further providing a water flow function to this sheet, the amount of rainwater permeating into the lower waste layer can be controlled, and a stable cover can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal front view showing a first embodiment of a soil covering structure in a waste final disposal site of the present invention. As shown in FIG. 1, the covering structure in the waste final disposal site of the present embodiment is that the waste layer 1 is reclaimed with a slope, and a breathable waterproof sheet 3 as a water-impervious sheet is laid just above it. Further, a covering soil layer composed of the lower coarse soil layer 2 and the upper fine soil layer 4 is further provided with a gradient in the same manner as the waste layer 1 and the breathable waterproof sheet 3. Become. Moreover, gravel is used as coarse-grained soil, and sand is used as fine-grained soil.

  The breathable waterproof sheet 3 is arranged in a staggered manner with openings 22 for water flow and ventilation, and the positions of the openings 22 are formed higher than the water shielding sheet surface. The cylindrical part 21 is provided by raising up. The ratio of the area of the opening 22 to the total area of the breathable waterproof sheet 3 is about 5%.

  In addition, in order to form the position of the opening part 22 higher than the water-impervious sheet surface, it is conceivable to form a trapezoidal mountain shape by embossing in addition to providing the cylindrical part 21.

  In the case of the tubular portion 21, the height of the tubular portion 21 is, for example, 4 cm, and the thickness of the coarse soil layer 2 is 6 cm. That is, the boundary between the coarse-grained soil layer 2 and the fine-grained soil layer 4 is positioned above the upper end of the cylindrical portion 21.

  Thereby, rainwater is drained sideways along the gradient by the capillary barrier effect at the boundary between the fine-grained soil layer 4 and the coarse-grained soil layer 2 during rainfall, and the amount of rain flowing into the coarse-grained soil layer 2 is the surface layer. It is less than the amount of rain that falls on the fine-grained soil layer 4.

  On the other hand, when there is a lot of rainfall, if the rainfall intensity exceeds a certain value, infiltration into the coarse-grained soil layer 2 that is the lower layer is started, but only rainwater that flows vertically into the opening 22 of the cylindrical portion 21. Penetrates into the waste layer 1 below the breathable waterproof sheet 3 and other rainwater is blocked by the cylindrical portion 21 as shown in FIG. 2 so that the breathable waterproof sheet does not flow into the opening 22. Drain to the side according to the gradient of 3. That is, the amount of rainwater that permeates the waste layer 1 can be controlled by the area of the opening 22.

  FIG. 3 is a longitudinal front view showing a second embodiment of the soil covering structure in the waste final disposal site of the present invention. Similarly to the first embodiment, in this embodiment, the waste layer 1 is reclaimed with a slope, and a breathable waterproof sheet 3 as a water-impervious sheet having a cylindrical portion 21 is laid on the land layer, Further, the coarse-grained soil layer 2 is laid, but the thickness of the coarse-grained soil layer 2 is made substantially equal to the height of the cylindrical portion 21, and the wire mesh 23 is laid so as to cover the upper end of the cylindrical portion 21. . Then, the wire mesh 23 is used as a boundary with the coarse-grained soil layer 2, and a fine-grained soil layer 4 serving as a surface layer is laid thereon.

  Even in this configuration, the capillary barrier effect is exhibited by the boundary between the fine-grained soil layer 4 and the coarse-grained soil layer 2 partitioned by the wire mesh 23, and rainwater is drained sideways along the boundary gradient during normal rain. At the same time, when there is a large amount of rainfall, rainwater flowing into the coarse-grained soil layer 2 that cannot be controlled only by this capillary barrier structure is controlled by the breathable waterproof sheet 3 provided with the cylindrical portion 21.

  Next, with reference to FIG. 7, description will be given of experimental results comparing the exclusion rates for eliminating rainwater permeation into the waste layer at the time of raining between the soil covering structure of the first example and other soil covering structures. In addition, the soil covering structure which performed the comparative experiment is the following five types of soil covering structures.

  As shown in FIG. 4, in the first soil covering structure, a fine-grained soil layer 4 is laid on a waste layer 1 with a thickness of 6 cm with a wire mesh 23 interposed therebetween, and a coarse-grained soil layer 2 is laid thereon. Thereafter, a fine-grained soil layer 4 is further laid thereon. That is, the breathable waterproof sheet 3 is not used and the covering soil layer has a three-layer structure, and is indicated by a triangle (sheet no sand (6 cm)) in the graph of FIG.

  As shown in FIG. 5, in the second covering structure, a breathable waterproof sheet 3 provided with a hole 25 having a diameter of 7 cm is laid on the waste layer 1, and only the fine-grained soil layer 4 is 6 cm. It is laid to a thickness to form a covering soil layer, and is indicated by an X mark (with sheet (hole with a diameter of 7 cm) sand (6 cm)) in the graph of FIG.

  As shown in FIG. 6, the third soil covering structure is constructed by laying a breathable waterproof sheet 3 on which the edge of the opening 22 is raised and a cylindrical part 21 having a height of 2 cm is provided on the waste layer 1, On top of this, only the fine-grained soil layer 4 is laid to a thickness of 6 cm to form a coated soil layer, which is indicated by □ (sheet + cylinder (2 cm) sand (6 cm)) in the graph of FIG.

  Similarly to the third covering structure, the fourth covering structure and the fifth covering structure are constructed by laying a breathable waterproof sheet 3 provided with a cylindrical portion 21 on the waste layer 1, and then on it. Only the fine-grained soil layer 4 is laid to a thickness of 6 cm. For the fourth soil covering structure, the height of the cylindrical portion 21 is set to 4 cm, and the mark in the graph of FIG. 7 (sheet + cylinder (4 cm)) Sand (6 cm)). The fifth soil covering structure is indicated by Δ (sheet + cylinder (6 cm) sand (6 cm)) in the graph of FIG. 7 with the height of the cylindrical portion 21 being 6 cm.

  As described above, the results of examining the relationship between the precipitation amount and the drainage rate of rainwater for the five types of soil covering structures and the soil covering structure of the first example are as shown in FIG. In addition, the drainage rate of the rainwater in the soil covering structure of the first embodiment is indicated by ● (sheet + cylinder (4 cm) gravel (6 cm)).

  First, when the precipitation is 20 mm / h or less, the rejection rate is maintained at 95% or higher in any type of soil covering structure. However, after the precipitation exceeds 20 mm / h, the removal rate dropped sharply in the first, second and third cover structures, and the precipitation reached 30 mm / h. The rejection rate dropped to 85% or less. In addition, in the 4th-6th soil covering structure, even if the precipitation reached 30 mm / h, the removal rate could be maintained at 85% or more.

  In all of the fourth to sixth soil covering structures, the height of the tubular portion 2 is 2/3 or more of the height of the first covering soil layer located immediately above the breathable waterproof sheet 3. In common. The first covering soil layer located immediately above the breathable waterproof sheet 3 is a fine-grained soil layer 4 in the fourth and fifth covering structures, and a coarse-grained soil in the sixth covering structure. Layer 2. In the fourth and sixth covering structures, the height of the tubular portion 2 is 4 cm, and in the fifth covering structure, the height of the tubular portion 2 is 6 cm, both of which are 4 cm or more in height. Have

  From the above, in order to keep the rainwater rejection rate at 85% or more even when the precipitation reaches 30 mm / h or more, the breathable waterproof sheet 3 as the water-impervious sheet provided with the cylindrical portion 21 is formed on the waste layer 1. Laying on and laying a covering soil layer thereon, the height of the cylindrical portion 21 is set to 4 cm or more, or the height of the cylindrical portion 2 is positioned directly above the breathable waterproof sheet 3 It turns out that it is necessary to set it as 2/3 or more of the height of the 1st covering soil layer.

  This is because when the height of the cylindrical portion 2 is 4 cm or more, even if rainwater is accumulated on the breathable waterproof sheet 3 with a large amount of rain, the retained rainwater has a sufficient height. This is probably because it cannot easily flow in from the upper part of the tubular part 2 and can maintain the rainfall adjustment function.

  Moreover, the penetration of rainwater into the waste layer 1 is achieved by setting the height of the cylindrical portion 2 to 2/3 or more of the height of the first covering soil layer located immediately above the breathable waterproof sheet 3. The rate can be stabilized even when rainwater permeates into the lower part of the layer when the rainwater permeates into the first covering soil layer located immediately above the breathable waterproof sheet 3. Since the upper end of the shape part 2 is located in the upper part of 2/3 or more of the layer, it is thought that the rainwater which stayed becomes difficult to flow into a cylindrical part.

  Furthermore, when the amount of precipitation increases, the drainage rate of rainwater also decreases in the second and third covering structures, but in the covering structure of the first embodiment, the precipitation reaches nearly 60 mm / h. However, the drainage rate of rainwater was kept at about 3%. This is considered to be due to a synergistic effect of the capillary barrier effect at the boundary between the fine-grained soil layer 4 and the coarse-grained soil layer 2 and the rain amount adjusting function by the breathable waterproof sheet 3 provided with the tubular portion 21.

It is a vertical front view which shows 1st Embodiment of the soil covering structure in the waste final disposal site of this invention. It is a top view of the air permeable waterproof sheet which is the principal part of 1st Embodiment. It is a vertical front view which shows 2nd Embodiment of the soil covering structure in the waste final disposal site of this invention. It is a vertical front view which shows the 1st example of another type of soil covering structure. It is a vertical front view which shows the 2nd example of another type of soil covering structure. It is a vertical front view which shows the 3rd example of another type of soil covering structure. It is a graph which shows the relationship between the removal rate of the penetration of rainwater in each soil covering structure, and precipitation. It is a vertical front view which shows the 1st example of the soil covering structure in the conventional waste final disposal site. It is a vertical front view which shows the 2nd example of the soil covering structure in the conventional waste final disposal site. It is a vertical front view which shows the 3rd example of the soil covering structure in the conventional waste final disposal site.

DESCRIPTION OF SYMBOLS 1 Waste layer 2 Coarse-grained soil layer 3 Breathable waterproof sheet 4 Fine-grained soil layer 5 Small hole 6 Rising part 7 Surface layer material 8 Seam part 9 Sheet 10, 11 Waste 12 Water conduit 13 Convex part 14 Catchment pond 15 Lower layer covering soil Material 16 Water permeable layer 17 Opening 18 Recess 19 Upper soil covering material 20, 20A Water shielding layer 21 Cylindrical part 22 Opening 23 Wire mesh 24 Coarse grain layer 25 Hole 26 Fine grain layer 28 Topsoil

Claims (3)

Between the waste layer and the covering soil layer, a water barrier sheet while laid remembering gradient, opening to the water shield sheet, for the water flow and aeration, the tubular portion launch the edges upwards The opening is located higher than the surface of the water-impervious sheet, and the covering soil layer includes a coarse-grained soil layer located immediately above the water-impervious sheet, and directly above the coarse-grained soil layer. A fine-grained soil layer is provided at a boundary between the coarse-grained soil layer and the fine-grained soil layer. Covering structure of waste final disposal site, characterized by being positioned on the upper side .   The soil covering structure of the waste final disposal site according to claim 1, wherein the height of the cylindrical portion is 2/3 or more of the height of the first covering soil layer located immediately above the water shielding sheet.   The soil covering structure of the waste final disposal site according to claim 1 or 2, wherein the height of the cylindrical portion is 4 cm or more.

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