KR100558388B1 - Cut off layer of landfill final cover system having self-repairable and high-durability - Google Patents

Abstract

The present invention relates to a highly durable landfill barrier layer having a self-recovery function that can effectively prevent flow and runoff into the ground by uneven settlement and cracks that may be caused by landfills or compressible landfills. An underlayer consisting of soil and an underlayer additive and having a permeability coefficient of 1 × 10 ⁻⁶ cm / sec or less; An upper layer laminated on the lower layer and composed of ground soil and an upper layer additive and having a permeability coefficient of 1 × 10 ⁻⁶ cm / sec or less; And an impermeable sedimentation layer formed by the reaction of the lower layer additive and the upper layer additive at a portion where the lower layer and the upper layer contact each other.

The present invention exhibits high strength and can satisfy low permeability of 1 × 10 ^-6 cm / sec or less, and can be added between additives even when defects occur in the barrier layer due to cracking and breakage due to physical action such as freezing and melting. As a composition technology for highly durable landfill barrier layer that has the ability to continuously generate new minerals by reaction, it is possible to minimize maintenance costs, so that gas or landfill wastes are scattered and water is introduced into the landfill. Can be effectively prevented. In addition, the use of fly ash, waste lime, etc., which was difficult to recycle in the past, can achieve the effect of resource recycling and cost reduction.

Landfill, final cover layer, barrier layer, permeability coefficient, uniaxial compressive strength, freeze thawing

Description

CUT OFF LAYER OF LANDFILL FINAL COVER SYSTEM HAVING SELF-REPAIRABLE AND HIGH-DURABILITY}             

Figure 1a and 1b shows a conceptual diagram for the installation criteria of the landfill legal order facility,

Figure 2 is a schematic diagram showing the formation of the reaction material and crack healing process between the additives,

Figure 3 is a photograph showing the results of the Jar Test (Jar- Test) to confirm the formation of insoluble precipitate of the present invention,

Figure 3a is a test result in the absence of a reaction catalyst,

3b is a test result when light soda ash is added as a reaction catalyst,

3c is a test result when dense soda ash is added as a reaction catalyst.

Figures 4a and 4b is a view showing a water-impermeable sediment (sealing) formation photograph generated at the upper and lower layer interface of the present invention

5a and 5b are X-ray diffraction graphs for the impermeable sealing of the present invention,

Figure 6 is a graph showing the permeability coefficient test results for each formulation in the present invention,

Figure 7 is a photograph showing the uniaxial compressive strength test by combination in the present invention,

Figure 7a shows the appearance of the specimen,

Figure 7b shows the uniaxial compressive strength test equipment,

Figure 7c shows the destruction of the specimen during the strength test,

8 is a graph showing the results of uniaxial compressive strength test for each compound in the present invention,

Figure 9a is a graph showing the results of a short-term permeability test for the freeze / thaw repeat for each formulation,

9b, 9c, and 9d are graphs showing the results of a long-term permeability test for freezing / thawing repetition (1, 3, 5 cycles) for each compound,

10 is a graph showing the results of uniaxial compressive strength test for freezing / thawing repeat for each compound in the present invention.

The present invention relates to a barrier layer in the final cover layer that can be used in a new landfill or unsanitary landfill maintenance project. Specifically, the present invention relates to a barrier layer capable of minimizing damage such as flowing water and rainwater through a breakage site (CRACK) that may occur in the barrier layer due to settlement that may occur due to garbage decomposition.

In Korea, most of the wastes are treated by landfill, incineration, ocean dumping and recycling, but the waste recycling and ocean dumping rate is very low.Incineration alone does not allow for complete disposal of wastes. There is a drawback of generating secondary pollutants in the air, so the proportion of disposal by landfill is still high.

In addition, immediately after the completion of the landfill, a barrier layer is installed to satisfy the permeability coefficient (1 × 10 ^-6 cm / sec) of the Waste Management Act treatment facility installation standard, to prevent gas and waste from scattering and to be isolated from the surrounding environment. . (See FIG. 1A, FIG. 1B)

The existing barrier layer composition technology is being replaced by the technology used in the bottom layer located at the bottom of the landfill, but in the case of such technology, most of the technique uses the ordering mechanism by solidification or expansion of the mixture mixed in the soil. Clay process, mixed earth process, reaction order layer process and the like. However, the existing methods have the disadvantages of securing suitable materials, difficulty in controlling water content and compaction management, and difficulty in repairing and reinforcing in case of large inequality.

In the conventional case, the method of forming the barrier layer is a method of solidifying by adding a mixture of solidified materials such as cement and calcium carbonate to the solidified soil by using soil soil (Korean Patent Publication No. 99-74738), waste casting sand on soil soil. A method of solidifying in a multi-layer by adding a mixture of solidifying materials such as, fly ash, waste lime or waste gypsum (Korean Patent Publication No. 98-2465), a method of forming a landfill complex order layer using a pozzolanic reaction (Korean Patent Publication No. 2000) -18629).

However, it is pointed out that the solidification method causes cracks on the surface and deterioration of the surface when exposed to the atmosphere. In addition, the mixed earth process is difficult to control the construction function ratio and cracks may occur after construction, and the self-forming and self-healing method requires a separate support layer when constructing in soft ground and lacks countermeasures in the event of large-scale uneven settlement and most of the order functions The disadvantage is that it depends on the resulting seal layer. In addition, the prior art described above intends to use a solidified soil layer having a certain level of compressive strength and impermeable characteristics as an ordered layer, and in view of its effect, the solidified soil layer should be formed thick. Therefore, the construction cost is not only high, but there are disadvantages in construction, and in particular, it is difficult to secure compressive strength and permeability coefficient, and in view of the compaction effect of compaction construction equipment which is commonly used in reality, the process of mixing, laying, and compacting solidified soil There were many technical improvement factors to obtain permeability coefficient of facility management standard through.

In addition, the seal formation mechanism introduced in Korea uses the pozzolanic reaction, and when using this reaction to form insoluble minerals at the interface between two layers, 1 × 10 ^-6 cm / sec or less in the entire barrier layer (30 cm). Not only do not meet the requirements of the domestic waste management law, which must satisfy the low water permeability of the plant, but if the seal is not effectively formed by other conditions, rainwater and runoff may continuously penetrate and cause excessive leachate generation. have.

Accordingly, the present inventors minimize the above problems and prevent the functional damage of the barrier layer to minimize the inflow of rainwater, and as a result of trying to find a barrier layer composition method for minimizing the contamination of groundwater and soil by suppressing the leachate generation, 1 It is composed of a low-permeability two-layer structure of × 10 ^-6 cm / sec or less, and a new mineral material is formed at the interface between the upper layer and the lower layer to sufficiently fill the gap of the granules, ensuring the ordering function and defects due to cracking. Even when it occurs, the upper and lower layer additives react with each other and restore cracks (see Fig. 2) to prevent the inflow of water into the landfill, creating a sanitary and safe waste landfill environment, and flexible design according to the soil conditions used. The present invention was completed by revealing that it is possible to present a model suitable for landfill site conditions. .

An object of the present invention is to prevent the scattering of gas and landfill waste and to prevent the inflow of water into the landfill when the barrier layer located in the landfill final cover layer for the maintenance of the landfill where the landfill is completed or unsanitary landfill To provide a more sanitary and environmentally stable landfill environment.

In order to achieve the above object, the present invention provides a buried land barrier layer consisting of an upper layer, a lower layer and an impermeable sedimentation layer in a portion where the upper layer and the lower layer contact.

Hereinafter, the present invention will be described in detail.

The present invention is composed of a base soil and a lower layer additive and a lower layer having a permeability coefficient of 1 × 10 ⁻⁶ cm / sec or less; An upper layer laminated on the lower layer and composed of ground soil and an upper layer additive and having a permeability coefficient of 1 × 10 ⁻⁶ cm / sec or less; And an impermeable sedimentation layer formed by a reaction of the lower layer additive and the upper layer additive at a portion where the lower layer and the upper layer contact each other.

First, the upper layer and the lower layer of the landfill barrier layer of the present invention includes soil and additives having different functions and performances.

As the soil used for the barrier layer, the ground soil can be used to install a landfill site, and after passing the ground soil through a 19 mm sieve, the soil with 200 passes of at least 10% is used, which may degrade the quality. It should not contain foreign substances. In addition, the soil to be used for the construction should be subjected to the indoor compaction test (KS F 2312) at least 30 days before construction to determine the maximum dry density and the optimum function ratio (OMC), and the water content within ㅁ 2% of the optimal function ratio during construction. It should be managed to maintain it. In addition, the soil should be stored so as not to be exposed to rainfall during rainy weather, and appropriate blocking facilities should be provided in summer and winter when there is a fear of sudden changes in outside temperature. Soil to be used for construction must be secured at least two days in advance and placed in a flat place. At this time, the effect of weather, such as water penetration or direct sunlight, should be minimized. In addition, after adjusting the particle size, it should be stored and the water content should be inspected at least twice per day to prevent the loss of moisture below the OMC. In principle, it should not be installed in summer or winter when the daily average temperature change is severe. In order to prevent sudden drying or temperature rise during summer construction, it should be equipped with shading facilities to avoid direct sunlight.

The lower layer additive is composed of slaked lime, waste lime, gypsum, Ca-based minerals and mixtures thereof that can react with the upper layer additive and clay minerals in the soil, and increase the strength by self-hardening. Manufactured according to the supplier's quality control standards. Among them, waste lime can be used in cement plants, quicklime plants, fertilizer plants, and chemical processes. These waste limes are silt clay mixed with silt and have a specific gravity of 2.05 to 2.14, which is lower than general clays. Especially, the waste lime is distributed at a lower position than kaolin, which is a representative clay, and is more stable clay. Economical benefits can be obtained by accepting the function of the barrier material in place of insufficient barrier clay and expensive geomembrane. Constituents of such a lower layer additive are specifically SiO ₂ 2-20%, Al ₂ O ₃ 0.1-10%, MgO 2-20%, CaO 30-80%, K ₂ O 0.1-10%, Na ₂ O 0.1- 10% and other additives 0.1-15%.

In addition, the top layer additives, together with the strength enhancement by self-hardening, can also react with the bottom layer additives and clay minerals in the soil to produce insoluble minerals in the granular gap, diatomaceous earth, fly ash, silica, Na-based minerals and mixtures thereof. Use that consisting of Among them, fly ash refers to the combustion ash generated when the pulverized coal is burned at a high temperature in a coal-fired power plant, and has the characteristic that oxides of silicon, aluminum and iron occupy 80 to 90% or more of the total. Such fly ash is an industrial waste, but if it is simply landfilled, there is a concern that the decomposition process continues to occur after disposal, thereby polluting the environment, but by using it as a barrier layer, it is possible to fix the harmful heavy metal in the fly ash. In addition, harmful substances such as harmful heavy metals in the fly ash can be eluted below the standards of the Waste Management Act as a result of the dissolution test, and can be safely used, and can have great economic advantages. The components of the upper layer additive are specifically SiO ₂ 30-80%, Al ₂ O ₃ 5-25%, MgO 0.1-20%, CaO 0.1-20%, K ₂ O 0.1-10%, Na ₂ O 0.1- 10% and other additives 0.1-15%.

Additives included in the lower layer and the upper layer should be stored in a moisture-proof or closed place, can be used in a bulk or packaged state and stored in accordance with general cement storage standards. Each additive should not be used if the packaging is damaged or hardened during transport or storage, or if it has been exposed to external weather conditions for a long time.

The proper dosage of the additive to be used in the present invention should be determined through an indoor compounding test according to the type and condition of the soil for each site, and the standard formulation ratio standard shown in Table 1 is applied.

Standard Mixing Ratio of Additives  Additive classification Top layer additive Bottom layer additive Standard compounding ratio 5-20% of the maximum dry density of raw soil 5 to 25% of the maximum dry density of raw soil

If the input amount is less than the above range, the effect of the addition of the additive is not obtained, if it exceeds the above range, the over-administration of the additive causes a problem that the physical properties of the barrier layer is lowered and the economy is lost.

Each of these layers satisfies the permeability coefficient (1 × 10 ⁻⁶ cm / sec or less) of the barrier layer specified in the Waste Management Act. In particular, the use of waste lime waste and fly ash can satisfy the permeability coefficient of the barrier layer. In addition, the lower layer has a uniaxial compressive strength of 10.0 ㎏ / ㎠ or more based on 28 days of aging, and the upper layer of 5.0 ㎏ / ㎠ or more, which ensures sufficient running performance for construction equipment during site construction and has freeze-thawing resistance. The uniaxial compressive strength decrease rate is less than 10%, and the permeability coefficient increase rate is less than 10%.

The upper layer and the lower layer of the present invention includes respective additives, and when applied to the barrier layer, an impermeable precipitation layer is formed by the reaction between the respective additives at the contact portion of the upper layer and the lower layer. The impermeable sedimentation layer has a function of continuously regenerating insoluble minerals in the gaps and cracks of the granules, and the sedimentation layer is quartz [α-qurtz, SiO ₂ ], feldspar [Albite, Na (AlSi ₃ O). ₈ )] and mucovite, KAl ₂ (AlSi ₃ O ₁₀ ) (OH) ₂ ], and these minerals are used as the main crystal phase to form an impermeable seal layer at the interface between the upper and lower layers.

The biggest function of the impermeable sedimentation layer is a self-restoring function that can restore the damaged part during breakage and cracking. Specifically, when a crack and a damaged part are generated, an impermeable precipitate layer is re-formed at the cracked part to maintain a permeability coefficient of 1 × 10 ⁻⁶ cm / sec or less. Immediately after the barrier layer was formed by the calcium-based inorganic materials added to each layer, basic conditions of pH 10-12 were formed, and the calcium-based inorganic materials combined with the CO ₂ and CO ₃ ^- components present in the soil, causing a carbonation reaction. By forming CaCO ₃ , an insoluble precipitate, an impermeable precipitate layer is formed. In addition, this process can occur in combination with other carbonate minerals to form CaCO ₃ , BaCO ₃ and SrCO ₃ mineral groups of aragonite groups in addition to calcite.

The buried barrier layer of the present invention is formed by laminating an upper layer after forming a lower layer. At this time, the additives required for each layer are mixed and used appropriately. After stacking two layers in this way, an impermeable precipitation layer is formed between the two layers by mutual reaction between additives of each layer.

In addition, the specimen can be prepared in confirming the effect of the barrier layer of the present invention. In order to prepare the specimen, first, the additives of each layer were mixed with the soil for treatment according to the standard mixing ratio, the water content of the mixed soil was measured, and the amount of water to maintain the compaction state of the optimum water content ratio (OMC) + 2% was determined. Increase or decrease the water content. The mixing ratio of each additive in the preparation of the specimen is based on mixing at a constant ratio with respect to the maximum dry density (Y _dmax ) of the soil obtained through the compaction test, and at this time, 2% of the wet side of the optimum water content ratio (OMC) obtained from the compaction test of the specimen. Unit quantity should be determined within and outside. When the sample is filled into the mold, the compaction is performed by adding the impact energy (5.625 kg / cm ³ ) converted into the standard A compaction energy. In the production of specimens for uniaxial compressive strength, the additives are mixed at three or more ratios to prepare strength expression curves, and based on this, the most suitable addition amount is calculated. Test specimens for uniaxial compression test were manufactured with diameter (D) 5 ㎝ and height (H) 10 ㎝, or diameter (D) 10 ㎝ and height (H) 20 ㎝ and the number of specimens should be 3 or more. Curing temperature is 20 ± 3 ℃ and wet curing. The specimens to be used for permeability test of variable position should be 10 ㎝ in diameter and 10 ㎝ in height and manufactured according to the specimen manufacturing method and curing method for uniaxial compressive strength. In addition, the mixing amount of each additive in the field is determined so that the average value of uniaxial compressive strength satisfies the design reference strength and permeability coefficient of the barrier layer. The site mix should take into account the loss rate during the operation (3 to 5%).

Hereinafter, the present invention will be described in detail by examples.

However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited to the following examples.

Experimental Example 1 Measurement of Basic Physical Properties of Test Subject Soil

The performance of the barrier layer composition method of the present invention may be different depending on the characteristics of each layer to be formed, but to ensure a permeability coefficient of less than 1 × 10 ^-6 cm / sec, which is the legal standard of the landfill barrier layer in all barrier layers It aims to satisfy the range, and it is characterized by the resistance to freezing and thawing, the degree of ordering, and the degree of ordering through the creation of new non-soluble minerals in the barrier layer of the particulate layer. In order to do this, a number of tests were performed on each layer or all layers, and various tests such as sieve analysis, hydrometer test, compaction test, and permeation test were performed for soil, which is a basic material. As the soil used for the test, granite weathered soil belonging to SW (Well-graded sand) series was used under the uniform classification method, and the test piece was manufactured and tested by applying 95% of the indoor compaction density value during the permeation test. Measured at 10 × ⁴ cm / sec. Test results for the soil used as the test subjects are shown in Table 2 below.

Basic Physical Properties of Experimental Soil Item Granite soil Test Methods Specific gravity (Gs) 2.58 KS F 2308 Gravel Fraction (%) 2.1 KS F 2302 Sand Fraction (%) 93.2 " Silt / Clay Fraction (%) 4.7 " Curvature factor (Cc) 1.4 " Uniformity Factor (Cu) 8.4 " Liquid Limit (LL) N.P KS F 2303 Firing limit (PL) N.P KS F 2304 Dry density (γ _dmax, t / m ³ ) 1.97 KS F 2312 Optimal function ratio (O.M.C) 11.5 KS F 2312 Permeability coefficient (cm / sec) 7.8 × 10 ^-4 KS F 2312

Experimental Example 2 Jar-Test for Confirming Insoluble Sediment Formation

As a test to confirm the formation process of impermeable sediment, the upper and lower layer materials are mixed with water at a predetermined amount, and then stirred slowly for 12 to 24 hours, and then the same amount of supernatant is taken through the elution process, followed by stirring and mixing. Observed by.

Fly ash containing diatomaceous earth and SiO ₂ components passed through # 200 sieve was used as the upper layer material, and oyster shells and waste lime containing a lot of slaked lime and CaO components passed through # 325 and # 200 sieve were used. In order to examine the effects of the reaction catalyst (soda ash), case 1 was not added with reaction catalyst, soda ash in case 2, and soda ash in case 3 was tested. The amount of soda ash used 10% of the top layer additive material.

After 72 hours, the result shows that precipitation occurs when the reaction catalyst is added (case 2 and case 3), and the diatomaceous earth / lime lime combination (2, 5) and fly ash / lime mixture (3, 6) This relatively precipitation could be seen much better. (See FIGS. 3A, 3B, and 3C)

 Material test number by Jar-Test ingredient Diatomaceous earth Fly ash Reaction Catalyst (Soda Ash) # 325 slaked lime 2 3 case 1 (do not put): NONE # 200 slaked lime 5 6 case 2 (light soda ash): L Waste lime 8 9 case 3 (small and medium times): D Oyster shell 11 12

Experimental Example 3 Compositional Analysis Test for Impervious Sediments (XRD, XRF)

One of the main features of this barrier layer composition method is that new non-insoluble minerals are generated in the ordered layer intergranular gap by enhancing the ordering performance and by ion dissociation and bonding between the clay minerals and additive materials. This is carried out through the formation of a barrier layer at the same time as the moisture contained in the soil, and occurs between the microcracks generated at the interface of the calcium-based inorganic layer or before and after construction when the infiltration or the water penetrates finely. X-ray diffraction (XRD) analysis and XRF analysis were performed on the mineral layer formed from the sample taken from the specimens that had been tested.

For X-ray diffraction analysis, the sample dried by the pretreatment was pulverized to 80 mesh or less using alumina mortar, and the XRF specimen was burned at 950 ° C. with dilithium tetraborate (Li _2). B ₄ O ₇ ) was mixed at a ratio of 1: 5, and a thin glass bead prepared by melting at 1,200 ° C. was used. First, the precipitate-forming part of the sample was taken and crushed to 200 or less (74 nm) or less, and the adsorbed water was evaporated by heating at 110 ° C. for 1 hour before X-ray diffraction analysis. Was carried out.

As a result of the long-term (8 months) reaction between the upper and lower additives, as shown in FIG. 4a, a dark colored reactant was observed at the interface between the two layers. After some sampling, XRD and XRF analysis were requested to the Institute of Ceramics for chemical composition analysis. As a result of XRF analysis, Si, Al, Fe, Ca, K, etc. were found to be the main elements, and the XRD analysis showed that the main mineral layer which is considered to increase the order of sample was quartz [α-quartz, SiO ₂ ], [albite, Na (AlSi ₃ O ₈ )], dolomite [muscovite, KAl ₂ (AlSi ₃ O ₁₀ ) (OH) ₂ ] were read as the main crystalline phase (see FIGS. 5A and 5B). As can be seen from the above results, the main mineral layer to increase the degree of ordering includes not only quartz but also feldspar and dolomite, which has the advantage of being able to exhibit not only the degree of order but also the high durability.

Experimental Example 4 Permeability Test

Permeability test, which is the most important design factor in designing barrier layer, is an experiment to measure the degree of water permeability of the facility. In this test, the permeability coefficient of specimen was determined using the variable two permeability test method.

The permeability coefficients for each formulation were measured and summarized in Table 4 and FIG. 6, and as shown here, unless the oyster shell was added, the upper and lower layers were 1.0, which is the design criterion of the barrier permeability coefficient. All the permeability coefficients of × 10 ^-6 cm / sec or less were satisfied. In particular, when the smallest permeability coefficient was measured in the sample 4 which was integrally formed with the upper and lower layers, the upper and lower layers were respectively manufactured. Unlike the sample, in the case of integrally manufactured, an additional order mechanism is formed to play a role of further reducing the permeability coefficient, which is considered to be the insoluble precipitate generated at the interface between the two layers.

 Permeability coefficient measurement result Sample Number Type of compound Permeability coefficient (cm / sec) Sample 1 Upper part (diatomaceous earth 8%) + lower part (breakthrough angle 10%) 3.69 × 10 ^-6 Sample 2 Upper part (diatomaceous earth 8%) + lower part (waste lime 10%) 2.34 × 10 ^-7 Sample 3 Upper part (fly ash 10%) + lower part (lime lime 10%) 3.53 × 10 ^-7 Sample 4 Upper part (diatomaceous earth 8%) + lower part (lime lime 12%) 0.95 × 10 ^-7 Sample 5 Lower part (breakthrough angle 10%) 4.04 × 10 ^-6 Sample 6 Lower part (waste lime 10%) 8.60 × 10 ^-7 Sample 7 Lower part (lime lime 12%) 1.63 × 10 ^-7 Sample 8 Upper part (8% of diatomaceous earth) 2.66 × 10 ^-7

Experimental Example 5 Strength Test

The uniaxial compressive strength test is a method to determine the strength of a sample by making a sample as a cylindrical specimen and applying congratulations in the absence of lateral pressure. It is an important design element that does not generate them. On the basis of the blending ratio and the optimum function ratio determined in the compaction test, three layers were compacted for each layer, and three layers were compacted for each layer.

In order to make the gap ratio and compaction energy constant, the number of hits, the water content, and the volume of the specimen were constant. The specimen was manufactured through the same process as in FIG. 7A, and the strength was measured using the test apparatus shown in FIG. 7B.

Initial strength and age 7 days, 14 days, 28 days of strength was tested and the results are shown in Table 5 and FIG. 8 and the state of specimen destruction is shown in Figure 7c.

In general landfill design, the strength after 28 days of reference age is all higher than 10 kg / cm ² , so it is judged that there will be no problem in strength development in the field application.

Uniaxial compressive strength test results by curing days Sample Number Additive compounding ratio Uniaxial compressive strength (㎏ / cm2) 3 days 7 days 14 days 28 days model 1 Diatomaceous Earth 8% 10.3 13.1 19.6 18.2 model 2 Slaked lime 12% 5.7 7.0 7.7 17.9 model 3 Upper layer (8% diatomaceous earth) + lower layer (12% limestone) 6.3 8.9 10.6 13.1 model 4 Fly Ash (10%) 2.3 7.4 13.2 12.3 model 5 Top layer (fly ash 10%) + bottom layer (slaked lime 12%) 2.7 8.8 13.7 10.5

Experimental Example 6 Dissolution Test

In terms of environmental factors and economics, the recycling of waste materials is being considered, but their use is suspended due to concerns about secondary pollution of the waste resources themselves. Therefore, dissolution test was conducted to examine the environmental properties of the materials to be used in the final barrier layer.

Among the waste process tests, the dissolution test method is as follows. Accurately weigh 100 g of the sample prepared according to the physical composition, add hydrochloric acid to purified water, and add a solvent (ml) having a pH of 5.8 to 6.3 in a 2,000 ml Erlenmeyer flask with a ratio of Sample: Solvent = 1: 10 (W: V). . At room temperature and atmospheric pressure, the number of shakes was about 200 times per minute and the shaker was shaken continuously for 6 hours using a shaker having a amplitude of 4 to 5 cm, followed by filtration with 1.0 μm glass fiber filter (GF / B). Take appropriate amount and prepare sample as dissolution test sample solution.

After preparing the dissolution test sample, ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometer, Inductively Coupled Plasma Emission Spectrometer, Shimadzu ICPQ 1000) analysis was performed at the College of Engineering, Seoul National University. In order to derive the ICP-MS analysis method, the harmful heavy metal content of the materials to be added were also investigated. The test results are shown in Tables 6 and 7.

Dissolution test result (ICP-AES method) (Unit: ppm) division Cr Cu Zn As CD Pb Hg Ground ND 0.0002 ND 0.0499 0.0455 0.0229 ND Diatomaceous earth ND 0.0343 0.2228 0.0278 0.0465 0.0122 ND Fly ash 0.0494 0.0004 ND 0.1098 0.0457 0.0225 ND Oyster shell ND 0.0003 ND 0.0317 0.0477 0.0091 ND Acceptance standard by Waste Management Act 1.5 3 - 1.5 0.3 3 0.005

   (N.D: Not Detectable)

Dissolution test result (ICP-MS method) (unit: ppm) division Cr52 Cu63 Zn66 Cd111 CS133 Pb208 Ground ND ND 0.0948 ND ND ND Diatomaceous earth ND 0.0510 0.3386 ND ND ND Fly ash 0.0610 ND ND ND ND ND Oyster shell ND 0.0343 ND ND ND ND Slaked lime 0.0427 ND ND ND ND ND Waste lime 0.0450 ND ND ND ND ND Acceptance standard by Waste Management Act 1.5 3 - 0.3 - 3

  (N.D: Not Detectable)

Based on these results, it is judged that secondary pollution does not occur around the landfill even if fly ash or waste lime, which is a waste material, is mixed in the barrier layer.

Experimental Example 7 Freeze-thawing Test

For the possibility of cracking in the barrier layer due to freezing / thawing due to the Samhansaon temperature, which is a characteristic of winter in Korea, the stability of the barrier layer and the change in the degree of performance of the barrier layer are checked and applied to design and construction. This study was conducted to obtain data. This test was conducted according to KS F test regulations issued by the Korean Standards Association. In the freeze-thawing test rule (KS F 2332) for the compacted soil-cement mixture, a total of 24 hours of freezing 24 hours (-23 ° C) and 24 hours of melting (21 ° C) is 1 cycle. The samples performed in the test are summarized in Table 8, and the water content of all specimens was uniformly fixed at 13%.

According to the existing literature, the permeability coefficient of natural or compacted clay is generally about 10 ⁻⁷ to 10 ⁻¹⁰ cm / sec and about 10 ⁻⁶ when frozen / thawed. In addition, the freeze / thaw cycles are most frequently received by the first freeze / thaw action, and change slightly from 3 to 10 times, and it is sufficient to repeat the freeze / thaw cycles 3 to 5 times. It is known. Therefore, in this test, the crack healing ability through cracking was confirmed through the change of permeability coefficient and strength by age when 1, 3, 5 cycles were repeated.

Additive compounding ratio of samples performed in freeze / thaw test Sample Number Additive compounding ratio model 1 Upper part (diatomaceous earth 8%) + lower part (lime lime 12%) model 2 Upper part (diatomaceous earth + bentonite 2%) + lower part (lime lime + bentonite 5%) model 3 Upper part (diatomaceous earth 8%) + lower part (lime lime 10%)

Referring to FIG. 9A, the permeability coefficient tends to decrease as time passes. This shows that the cracks due to the action of freezing and thawing are gradually restored to the original permeability coefficient level. In particular, in the case of model 3 of 1 cycle, it is close to 1.0 × 10 ^-7 cm / sec after 8 hours. Indicated.

9B, 9C, and 9D show long-term permeability coefficients for 1, 3, and 5 cycles, respectively, and after repeated freezing / thawing for all kinds of models, the long-term permeability coefficient is 1.0 × 10 ⁻⁶ cm / You can see that it does not exceed sec and remains constant. Therefore, through the permeation test, it could be confirmed that the crack healing effect by the self-recovering material in the case of micro cracking caused by freezing / thawing.

The change in uniaxial compressive strength for 1, 3 and 5 cycles through repeated freeze / thaw tests is shown in Figure 10. Based on the 28-day intensity, model 2 tends to increase by 22% and 35% in 3 and 5 cycles, compared to 1 cycle in intensity (14.0kg / cm ² ). Shows a similar aspect. In addition, the 28-day aging intensity tended to increase from 20.1% (5 cycle-model 3) to 88.3% (1 cycle-model 3) compared to the initial strength of each model. Therefore, the intensity of uniaxial compressive strength test results for repeated freezing / thawing samples tends to increase as the number of freezing / thawing cycles increases and as the age period increases. In addition, since the strength in all cases is expressed more than 5kg / cm ^{2 It} is determined that there is no effect on the strength of the final barrier layer due to freezing / thawing in winter.

As described above, the buried barrier layer of the present invention exhibits high strength and satisfies low permeability of 1 × 10 ^-6 cm / sec or less, which is suitable for use as a barrier layer of the final covering layer, and is also cracked. In addition, even when defects in the barrier layer due to breakage or the like occur, new minerals generated by the reaction between the additives are continuously generated in the damaged part, thereby effectively preventing the splashing of gas or landfill waste and inflow of water into the landfill. In addition, the use of industrial waste, fly ash, waste lime, etc. can achieve the effect of resource recycling and cost reduction.

Claims (9)

An underlayer consisting of raw soil and an underlayer additive and having a permeability coefficient of 1 × 10 ⁻⁶ cm / sec or less; An upper layer laminated on the lower layer and composed of ground soil and an upper layer additive and having a permeability coefficient of 1 × 10 ⁻⁶ cm / sec or less; And A landfill barrier layer comprising an impermeable sedimentation layer formed by a reaction of the lower layer additive and the upper layer additive at a portion where the lower layer and the upper layer contact each other. According to claim 1, wherein the lower layer additive is composed of hydrated lime, waste lime, gypsum, Ca-based inorganic material and mixtures thereof, The buried barrier layer is characterized in that the upper layer additive is composed of diatomaceous earth, fly ash, silica, Na-based inorganic materials and mixtures thereof. The constituent of the lower layer additive is SiO ₂ 2-20%, Al ₂ O ₃ 0.1-10%, MgO 2-20%, CaO 30-80%, K ₂ O 0.1-10. A landfill barrier layer, characterized in that 0.1% to 10% Na ₂ O and 0.1 to 15% other additives. According to claim 1 or 2, wherein the constituent components of the upper layer additive is SiO _{2 30} to 80%, Al ₂ O _{3 5 to} 25%, MgO 0.1 to 20%, CaO 0.1 to 20%, K ₂ O 0.1 to 10 A landfill barrier layer, characterized in that 0.1% to 10% Na ₂ O and 0.1 to 15% other additives. The landfill barrier layer according to claim 1, wherein the input amount of the lower layer additive is 5 to 20% of the maximum dry density of the ground soil. The landfill barrier layer according to claim 1, wherein the input amount of the upper layer additive is 5 to 25% of the maximum dry density of the ground soil. The method of claim 1, wherein the impermeable precipitate layer is quartz [α-quartz, SiO ₂ ], feldspar [albite, Na (AlSi ₃ O ₈₎ ] and mucovite, KAl ₂ (AlSi ₃ O ₁₀ ) (OH) ₂ )] a buried barrier layer comprising the mineral components. The landfill block according to claim 1, wherein the lower layer has a uniaxial compressive strength of 10.0 kg / cm 2 or more based on 28 days of age, and the upper layer has a uniaxial compressive strength of 5.0 kg / cm 2 or more based on 28 days of age. layer. The method of claim 1, wherein the landfill barrier layer is characterized in that the impermeable sedimentation layer is re-formed at the crack generation site when the cracking and breakage site occurs to maintain and preserve a permeability coefficient of less than 1 × 10 ^-6 cm / sec. layer.

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