JP2010242452A - Construction method for muck bank, and banking structure of muck bank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an execution method for a muck bank easy to be executed and exhibiting a high neutralization effect. <P>SOLUTION: Excavation mucks are layeredly tightened fixedly to form a tightly fastened layer 9, when executing the muck bank 1, using, as a banking material, the excavation mucks containing a pyrite generating acidic water by hydration, and a neutralization layer 10 for neutralizing the acidic water is formed on an upper face of the tightly fastened layer 9. The neutralization layer 10 is formed by scattering uniformly a sand-like limestone. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for constructing a shear embankment containing an acid water generating substance, and a embankment structure.

In some cases, an excavation pile such as a tunnel contains an acid water generating substance such as pyrite (FeS ₂ ). If this excavation is used for embankment material, it will generate acid water if it is wet by rain or the like, which may adversely affect the surrounding environment. In order to prevent this adverse effect, the top surface and slope of the embankment are covered with soil or the like to prevent infiltration of rainwater, or the collected acidic water is discharged after being neutralized. Moreover, mixing the alkaline substance as a neutralizing material with soil is also performed (for example, refer patent document 1).

Japanese Patent Application Laid-Open No. 2000-282034

  However, it is difficult to completely prevent rainwater permeation even when soil covering or the like is performed. In particular, it is impossible to prevent rainwater permeation during construction. For this reason, in order to neutralize the collected acidic water, a treatment facility must be provided. Furthermore, when mixing the neutralizing material with the soil, it takes a lot of labor to mix uniformly with the whole soil, and in order to expect a certain effect, it is necessary to secure the minimum addition amount. It is uneconomical.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a method for constructing a shear bank that is easy to construct and has a high neutralization effect, and a bank structure for the shear bank. It is.

The present invention, in the construction method of the shear embankment using the excavation shear including a substance that generates acid water by water content as a embankment material,
Forming the compacted layer by compacting the excavated ladle in layers;
Forming a neutralization layer for neutralizing the acidic water on the upper surface of the compaction layer;
It is characterized by performing.

Further, the present invention is a banking structure of a shear embankment in which an excavation shear including a substance that generates acidic water by water content is used as a banking material,
A neutralization layer for neutralizing the acidic water is provided between the laminated compaction layers.

  According to the present invention, even if rainwater permeates into the embankment and acid water is generated, the acid water can be neutralized by the neutralization layer. Since this neutralization layer is formed on the upper surface of the compaction layer, construction is easy.

  In the present invention, if the neutralization layer is formed by grinding sandy limestone or dolomite, the neutralization layer can be easily formed.

  Further, in the present invention, if the neutralization layer is inclined downward toward the vertical gutter for discharging the water in the shear embankment, the water in the embankment is brought to the vertical gutter side by the neutralization layer after passing water. Can lead.

  Furthermore, in this invention, if the neutralizing material which neutralizes the said acidic water is provided in the circumference | surroundings of the said vertical gutter, after neutralizing acidic water with a neutralizing material, it can be guide | induced to a vertical gutter. For this reason, mechanical equipment is unnecessary, and there is almost no trouble of maintenance.

  ADVANTAGE OF THE INVENTION According to this invention, the construction method and the embankment structure of the shear embankment which construction is easy are realizable.

It is a top view of shear embankment. It is an AA arrow line view of FIG. It is a figure explaining the neutralizing material with which a vertical gutter periphery is filled, (a) is a partial enlarged view around a vertical gutter, (b) is a partial enlarged view near a recessed part, (c) is a BB arrow line view. It is. It is a figure explaining the flow of water in embankment. It is a result of the neutralization test (batch test) of the acidic water by limestone. It is a result of the neutralization test (column test) of the acidic water by limestone. It is a figure explaining the state which provided the impermeable layer etc. in the ground, (a) is a top view, (b) is CC arrow directional view. It is a figure explaining the state which provided the lowermost compaction layer, (a) is a top view, (b) is a DD arrow line view. (A)-(c) is a figure explaining a mode that the embankment block of a construction unit is added and a compaction layer is constructed. It is a figure explaining the state which filled the limestone etc. in the recessed part of a vertical gutter periphery, (a) is a top view, (b) is an EE arrow directional view. It is a figure explaining the state which formed the intermediate | middle impermeable layer, (a) is a top view, (b) is a FF arrow line view. It is a figure explaining the completed embankment, (a) is a top view, (b) is a GG arrow line view. It is a figure explaining a modification and is a figure explaining the state which pinched the upper and lower sides of the neutralization layer with the water-permeable sheet.

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

  As shown in FIGS. 1 and 2, the shear fill 1 (hereinafter referred to as the fill 1) is provided in a truncated pyramid shape having a substantially square bottom surface. The ground G in a range where the embankment 1 is provided is inclined downward toward the center, and is provided with a downward gradient of about 3%, for example. A water shielding layer 2 is provided on the ground G. The water shielding layer 2 is constituted by a resinous water shielding sheet. The water shielding layer 2 may be formed by soil water shielding using bentonite or the like.

  A lower dam 3 is provided on the outer periphery of the impermeable layer 2 to prevent sediment from flowing out of the embankment. The lower dam 3 is formed by depositing healthy soil so as to surround a range where the embankment 1 is provided. The lower dam 3 has a substantially triangular shape. Therefore, the lower dam 3 forms a slope that slopes down to the inside of the embankment and to the outside of the embankment.

  In the center of the ground G, a through-passage 6 for connecting the vertical gutter 5 to the buried underground drain pipe 4 is provided. The vertical gutter 5 guides rainwater that has penetrated into the embankment 1 to the underground drain pipe 4 and is erected in a state where the lower end portion is inserted into the through passage 6. This vertical gutter 5 is a tubular member (a perforated pipe) having a large number of water passage holes 7 on its side surface, and is constituted by a cylindrical member having a diameter of about 1 to 2 m. Since the vertical gutter 5 is provided in a state of penetrating the embankment 1 in the vertical direction, its length is determined according to the height of the embankment 1. That is, the length at which the upper end opening of the vertical gutter 5 is arranged at the center of the embankment upper surface is determined to be, for example, about 5-10 m. The vertical hook 5 is not limited to a cylindrical member. It may be a bellows tube or a rectangular tube.

  A neutralizer 8 is provided around the vertical gutter 5 so as to surround the vertical gutter 5. The neutralizing material 8 neutralizes acidic water generated in the embankment 1. The neutralizing material 8 will be described later. Around the neutralizing material 8, a plurality of compaction layers 9 are provided in a stacked state in the height direction. The compaction layer 9 is formed by stacking excavation shears to a predetermined thickness (for example, 1 to 2 m) and compacting. As described above, since the ground G is inclined downward toward the center, the surface of the compaction layer 9 is also inclined downward toward the center. A neutralization layer 10 is formed on the surface of each compaction layer 9. This neutralization layer 10 is provided between the compaction layers 9 formed by lamination, and neutralizes acidic water generated in the embankment 1. The neutralization layer 10 will be described later. An intermediate impermeable layer 11 is provided midway in the height direction of the embankment 1. The intermediate water-impervious layer 11 is constituted by a water-impervious sheet or soil water-impervious, and is formed each time a predetermined number of compaction layers 9 are formed. A roll-shaped material is used for the water-impervious sheet, but a simple sheet in which small water-impervious sheets are stacked may be used. The intermediate water-impervious layer 11 is also provided in a state of being inclined downward toward the central portion (vertical shaft 5). For this reason, rainwater that has flowed down in the embankment 1 and has reached the intermediate impermeable layer 11 moves along the intermediate impermeable layer 11 to the vertical fence 5 side. Such an intermediate impermeable layer 11 functions as a water collection layer that collects water in the embankment 1 toward the vertical shaft 5.

  On the outer surface of each compaction layer 9, that is, on the slope of the embankment 1, a covering soil layer 12 is formed. The covering earth and sand layer 12 prevents the outflow of earth and sand to the outside of the embankment site, and is formed by depositing healthy soil to a predetermined thickness. And the upper end of the covering earth-and-sand layer 12 is provided a little higher than the uppermost compaction layer 9, and comprises the preceding temporary dam 13. The waterproof sheet 14 is spread from the part where the upper surface of the embankment 1 is completed in a state of covering the preceding temporary dam 13, and construction is performed so as to drain permeated water due to rainfall as much as possible.

  Next, the neutralization layer 10 provided on the upper surface of the compaction layer 9 and the neutralization material 8 around the vertical gutter 5 will be described.

  The neutralization layer 10 is made of limestone that is about the size of sand (particle size is 1 mm or less). In this embodiment, limestone is uniformly ground on the upper surface of the compacted layer 9 so that the layer thickness is about 1 mm.

  As the neutralizing material 8, limestone having a particle size of about gravel (particle size of about 5 to 20 mm) is used. In this embodiment, as shown in FIGS. 3A to 3C, a mixture obtained by mixing the neutralizing material 8 with stones or rocks (hereinafter referred to as stones 15) is filled in the recesses 16 around the vertical gutter 5. . This recessed part 16 is comprised by the inner slope of the embankment block BK (refer FIG. 9 (a)-(c)) in the construction unit which comprises each compaction layer 9. As shown in FIG. In this way, when the neutralizing material 8 is mixed with the stone 15 and the like, even if the neutralizing material 8 (limestone) is reduced by the neutralization reaction with the acidic water, the peripheral portion of the vertical gutter 5 is obtained by the stone 15. Can prevent the problem of sinking. Moreover, it is preferable to use a stone or the like 15 larger than the water passage hole 7 of the vertical gutter 5. It is because it can suppress that the neutralizing material 8 and earth and sand enter the vertical shaft 5 through the water flow hole 7.

As the neutralizing layer 10 and the neutralizing material 8, dolomite (a mixture of CaCO ₃ and MgCO ₃ ), cement, and lime can be used in addition to limestone. Here, when limestone or dolomite is used, water in contact with limestone or the like shows neutrality. Therefore, generation | occurrence | production of the water (alkali water) which shows alkalinity can be prevented. Even if digging ladle contains harmful heavy metal, the heavy metal is adsorbed and fixed by limestone or the like. That is, environmental pollution can be prevented by using limestone or the like for the neutralizing layer 10 or the neutralizing material 8.

  Next, the flow of water in the embankment 1 will be described.

Water penetrates into the embankment 1 due to rainfall during construction or after construction. This water naturally flows down in the embankment 1 by a route as shown by an arrow in FIG. Here, when excavation shear containing pyrite is used as the embankment material, water (acidic water) that becomes sulfuric acid acid is generated by the reaction of pyrite and water. When this acidic water passes through the neutralization layer 10, the acidic water reacts with limestone and is neutralized. The reaction formula in this case is shown below.
CaCO ₃ + H ₂ SO ₄ → CaSO ₄ + H ₂ CO ₃

  The water (acidic water, neutralized water) that has reached the intermediate impermeable layer 11 and the impermeable layer 2 flows along the inclination of the intermediate impermeable layer 11 and the impermeable layer 2. In addition, since gypsum is generated by a chemical reaction in the neutralization layer 10, some water also flows along the inclination of the neutralization layer 10. As described above, the neutralizing material 8 is disposed at the inclined lower end of the intermediate water shielding layer 11 and the water shielding layer 2. For this reason, even if the water which flowed down exhibits acidity, it is neutralized by the contact with the neutralizing material 8. Then, neutralized water flows into the vertical shaft 5 and is discharged out of the embankment through the underground drain pipe 4. As a result, it is possible to reliably prevent the problem that acidic water is discharged outside the embankment 1. In particular, since the neutralized water is allowed to flow into the vertical gutter 5, even if leakage occurs in the underground drain pipe 4, the neutralized water only permeates, and environmental pollution can be effectively prevented. In addition, since the permeated water naturally flows down in the embankment 1, mechanical equipment for flowing water is not necessary, and the equipment can be simplified.

  Moreover, in this embodiment, the particle size of the limestone used for the neutralization layer 10 is made smaller than the particle size of the limestone used for the neutralizing material 8. For this reason, it is possible to efficiently neutralize acidic water by increasing the contact area on the neutralizing layer 10 side, and neutralize acidic water while ensuring water permeability on the neutralizing material 8 side.

  Next, the neutralizing power of limestone will be described.

First, the pH change of the dilute sulfuric acid solution when limestone was added was confirmed. When acidic water having pH 3 is generated, the amount of sulfuric acid contained is 0.5 × 10 ⁻³ mol / L, and the amount of limestone necessary for neutralization is 0.05 g / L. Then, the test which confirms the neutralization effect of limestone was done about the following three patterns.
(1) Limestone 0.05 g / dilute sulfuric acid solution 1 L: (neutralization equivalent = theoretical required amount)
(2) Limestone 0.3 g / dilute sulfuric acid solution 1 L: (6 times the neutralization equivalent)
(3) Limestone 0.6 g / dilute sulfuric acid solution 1 L: (12 times the neutralization equivalent)

  In this test, the above amount of powdered limestone was added to a dilute sulfuric acid solution having a pH of 3, and the change in pH was measured while stirring with a stirrer. The results are shown in FIG.

Limestone reacts with sulfuric acid in a short time. When 0.6 g of limestone was added, pH 6 was reached after 1 second, and pH 7 was reached after 3 seconds. Even when 0.05 g of limestone was added, the pH became 6 or more after about 180 seconds. Assuming that the hydraulic conductivity of the embankment 1 is 10 ⁻² cm / sec, it takes 10 seconds to pass through a thickness of 1 mm. Since the thickness of the neutralization layer 10 is 1 mm, it turns out that acidic water of pH 3 can be neutralized to pH 6 or more by efficiently contacting limestone about 6 times the neutralization equivalent.

  Next, the pH change of the dilute sulfuric acid solution when passing through a column filled with limestone was measured. In this test, powdered limestone was packed into a cylindrical column having a diameter of 5 cm so as to have a thickness of 1 mm. Further, in order to prevent the limestone from moving with the water flow, silica sand was filled on the downstream side and a fine wire mesh was arranged on the upstream side. Then, acidic water having a pH of 3 was passed from the bottom of the column, and the leachate was collected every 1 minute to measure the pH. The water flow rate was 11.8 ml / sec in consideration of the permeability coefficient of the embankment 1 and the column diameter. The results are shown in FIG. The pH of the leachate was 7 or more immediately after water flow, and was about 6.3 even when 600 ml was passed. From this result, it can be seen that if the thickness of the neutralization layer 10 is about 1 mm, the acidic water can be sufficiently neutralized.

  Next, the construction method of the embankment 1 is demonstrated. For convenience, the embankment 1 in the description of the construction method is different from the embankment 1 in FIG. 1 in the number of compacted layers 9 and the size of the embankment 1.

  First, as shown to Fig.7 (a), (b), the gradient which goes down to a center part is provided with respect to the ground G of the range in which the embankment 1 is provided, and the water-impervious layer 2 is provided. Moreover, the lower dam 3 is provided in an outer peripheral part, the penetration path 6 is provided in the center part, and the vertical gutter 5 is set up. Next, as shown in FIGS. 8A and 8B, the lowermost compaction layer 9 is provided (consolidation layer forming step). As shown in FIGS. 9A to 9C, the compaction layer 9 is constructed in such a manner that the embankment blocks BK of construction units are stacked in order from the outer peripheral side to the inner side. For this reason, the recessed part 16 enclosed by the slope inside the embankment block BK is formed in the periphery of the vertical fence 5. If the lowermost compaction layer 9 is formed, the neutralization layer 10 is formed on the upper surface of the compaction layer 9 (neutralization layer forming step). The neutralization layer 10 is formed by, for example, moistening limestone that has been moistened with a mesh sand spreader. By using moistened limestone, scattering of the limestone into the air can be prevented. And the neutralization layer 10 of fixed layer thickness can be easily formed by using a mesh sand spreader. Moreover, as shown to Fig.10 (a), (b), the recessed part 16 is filled with the mixture of the limestone, the stone, etc. 15 as the neutralization material 8 (neutralization material filling process).

  Thereafter, the steps of forming the compaction layer 9, forming the neutralization layer 10, and filling the neutralizing material 8 are repeated. Thereby, the compaction layer 9 is stacked and the neutralizing material 8 is raised. Moreover, the covering earth and sand layer 12 is formed in the slope of the part which hits the outermost periphery part of the embankment 1. When a predetermined number of compaction layers 9 are formed, an intermediate water shielding layer 11 is formed as shown in FIGS. 11A and 11B, and the compaction layer 9 is overlaid on the intermediate water shielding layer 11. Form. Then, as shown in FIGS. 12A and 12B, the embankment 1 is completed by forming the uppermost compaction layer 9.

  According to this construction method, the neutralization layer 10 is formed every time the compaction layer 9 is formed. The sum layer 10 can neutralize. For this reason, the outflow of the generated acidic water outside the embankment can be effectively suppressed.

Moreover, since the neutralization layer 10 is formed by soaking limestone, the labor can be remarkably reduced as compared with the method of uniformly mixing the neutralization material with the embankment material, and the use amount of the neutralization material can be reduced. Less. In general, when a neutralization effect is expected by stirring and mixing, a minimum of about 25 kg / m ³ is added regardless of the required amount of acidic substance equivalents in consideration of ensuring contact between the neutralizing material and the target soil. Although the amount is ensured, according to the method of the present invention, a sufficient effect can be expected with a use amount of about 1 kg / m ³ .

  By the way, this invention is not limited to the above-mentioned embodiment, A various deformation | transformation is possible. For example, as shown in FIG. 13, water permeable sheets 17 may be disposed above and below the neutralization layer 10. If it does in this way, since it will be in the state where the neutralization layer 10 was pinched | interposed with the water-permeable sheet 17, the outflow of the limestone grain which comprises the neutralization layer 10 can be prevented.

  Although the embankment 1 provided with the neutralization layer 10 and the neutralizing material 8 has been described in the above-described embodiment, a sufficient neutralization effect can be obtained with the neutralization layer 10 alone. Further, neutralization can be performed more reliably by the combined use with the neutralizing material 8.

  Although the embankment material in the above-mentioned embodiment was excavation shear containing pyrite, it is not restricted to this. The drilling can be performed in the same manner as long as it is an excavation drill containing an acid water generating substance that generates acid water by water content.

  Further, when the water shielding layer 2 on the ground G is soil water shielding, a neutralization layer may be formed on the surface of the water shielding layer 2.

  Furthermore, when the water permeability of the embankment material is not so good, the drainage water is more permeable than the embankment material and actively flows water instead of or together with the water shielding layers 2 and 11. It is also conceivable to provide a layer.

DESCRIPTION OF SYMBOLS 1 Embankment 2 Water-impervious layer 3 Lower dam 4 Underground drainage pipe 5 Vertical shaft 6 Passage 7 Passage hole 8 Neutralizing material 9 Compaction layer 10 Neutralization layer 11 Intermediate water-impervious layer 12 Covered sediment layer 13 Preliminary temporary dam 14 Sheet 15 Stone etc. 16 Concave part 17 Water-permeable sheet BK Embankment block

Claims (5)

In the construction method of shear embankment using excavation shear including a material that generates acid water by water content as the embankment material,
Forming the compacted layer by compacting the excavated ladle in layers;
Forming a neutralization layer for neutralizing the acidic water on the upper surface of the compaction layer;
A construction method of shear embankment characterized by   The said neutralization layer is formed by crushing sandy limestone or dolomite, and the construction method of the shear embankment of Claim 1 characterized by the above-mentioned.   The construction method of the shear bank according to claim 2, wherein the neutralization layer is inclined downward toward a vertical shaft for discharging water in the shear bank.   The construction method of the shear embankment according to claim 3, wherein a neutralizing material for neutralizing the acidic water is provided around the vertical fence. In the embankment structure of shear embankment using excavation shear including a substance that generates acid water by water content as embankment material,
An embankment structure for shear embankment, wherein a neutralization layer for neutralizing the acidic water is provided between the compacted layers.

Images