CN104963365B - An impermeable clay cushion at the bottom of a landfill and its application - Google Patents

Abstract

Waterproof clay liner and its application the present invention relates to a kind of refuse landfill bottom, clay liner are to form through rolling after the mixing of kaolinite clay, illite clay and water, porosity≤40%；The quality of the kaolinite clay is X, 10≤X ＜ 70% with the percentage of the kaolinite clay and the illite clay total amount；The quality of the illite clay is Y, 30 ＜ Y≤90% with the percentage of the kaolinite clay and the illite clay total amount.By the porosity and the ratio of kaolinite clay and illite clay of strict control clay liner, which produces unexpected effect：Clay liner starts initial hydraulic gradient occur（i₀）, such that it is able to the infiltration of block contaminant Leachate site.

Description

An impermeable clay cushion at the bottom of a landfill and its application

technical field

The invention belongs to the field of landfill anti-seepage, and relates to a clay cushion, in particular to an impermeable clay cushion at the bottom of a garbage landfill and an application thereof.

Background technique

my country is a country with a large population, but also a country with a large garbage output. At present, there are three commonly used waste disposal methods, incineration, landfill and composting. Among various disposal methods, sanitary landfill is widely used because of its advantages of safety and sanitation, large disposal capacity and high efficiency. More than 80% of domestic waste in my country is disposed of by landfill, and more and more waste is landfilled. field is built.

As the waste in landfill degrades over time, a large number of pollutants with high concentration and complex composition will be produced. These pollutants can pass through the cushion layer through convection and diffusion, thereby polluting the underground environment. In order to prevent pollutants from polluting the underground environment, it is necessary to form a clay cushion at the bottom of the landfill to make the permeability coefficient k≤10 ^-7 cm/s to ensure that pollutants will not pass through the clay cushion.

Contents of the invention

The purpose of the present invention is to provide an impermeable clay cushion at the bottom of a landfill and its application in order to overcome the deficiencies of the prior art.

In order to achieve the above object, the technical solution adopted in the present invention is: a kind of impermeable clay cushion at the bottom of the landfill, which is formed by rolling after kaolinite clay, illite clay and water are mixed, and its pores rate≤40%; the percentage of the quality of the kaolinite clay to the total amount of the kaolinite clay and the illite clay is X, 10≤X<70%; the quality of the illite clay and the The percentage of the total amount of kaolinite clay and illite clay is Y, 30<Y≤90%.

Optimally, the percentage of the mass of the water to the total amount of the kaolinite clay and the illite clay is 20-25%.

Optimally, the kaolinite clay contains the following mineral components in mass fraction:

Kaolinite 70~75%;

Illite 5~10%;

Montmorillonite 5~10%;

Quartz 10~20%.

Further, the illite clay contains the following mineral components in mass fraction:

Kaolinite 10~15%;

Illite 50~60%;

Montmorillonite 10~15%;

Quartz 15~20%.

Preferably, the kaolinite clay and the illite clay are clay particles with a particle size below 1 mm.

Optimally, the X is 10-30%, and the Y is 70-90%.

Optimally, the X is 30%, the Y is 70%, and the percentage of the mass of the water to the total amount of the kaolinite clay and the illite clay is 22%.

Optimally, its effective porosity is ≤8.5%.

Optimally, when the leachate water level is ≤12m, the thickness of the clay cushion is ≥20cm.

The present invention also particularly relates to the application of the above-mentioned impermeable clay cushion at the bottom of the landfill in landfill. The clay cushion with a thickness greater than or equal to 20 cm is formed at the bottom of the landfill in advance, and then filled Bury trash.

Due to the application of the above-mentioned technical solutions, the present invention has the following advantages compared with the prior art: the impermeable clay cushion at the bottom of the landfill of the present invention is formed by rolling after mixing kaolinite clay, illite clay and water , by strictly controlling the porosity of the clay cushion and the ratio of kaolinite clay to illite clay, an unexpected effect has been achieved: the clay cushion begins to have an initial hydraulic gradient (i ₀ ), which can block the leaching of pollutants liquid penetration.

Description of drawings

Accompanying drawing 1 shows the different initial hydraulic gradients and permeability coefficients possessed when the impermeable clay cushion at the bottom of the landfill of the present invention contains illite clay in different proportions.

detailed description

The impermeable clay cushion at the bottom of the landfill of the present invention is formed by rolling after kaolinite clay, illite clay and water are mixed, and its porosity≤40%; the quality of the kaolinite clay The percentage of the total amount of the kaolinite clay and the illite clay is X, 10≤X<70%; the quality of the illite clay and the total amount of the kaolinite clay and the illite clay The percentage is Y, 30<Y≤90%. By strictly controlling the porosity of the clay cushion and the ratio of kaolinite clay and illite clay, this has an unexpected effect: the clay cushion starts to have an initial hydraulic gradient (i ₀ ), which can block the leaching of pollutants The seepage of liquid; and when the hydraulic gradient i of the clay cushion in the landfill is less than its initial hydraulic gradient i ₀ , it can completely block the seepage of water pollutant leachate. Wherein, the percentage of the mass of water to the total amount of the kaolinite clay and the illite clay is 20-25%. The kaolinite clay preferably contains the following mineral components in mass fractions: 70-75% kaolinite; 5-10% illite; 5-10% montmorillonite; 10-20% quartz. The illite clay preferably contains the following mineral components in mass fractions: 10-15% kaolinite; 50-60% illite; 10-15% montmorillonite; 15-20% quartz. The clay cushion prepared by using the above-mentioned kaolinite clay and illite clay has the best effect of blocking the seepage of pollutant leachate. The kaolinite clay and the illite clay are preferably clay particles with a particle size of less than 1 mm obtained after sun-drying, crushing and screening, and such clay has a smaller permeability coefficient after rolling.

Wherein, said X is preferably 10-30%, said Y is preferably 70-90%, and the initial hydraulic gradient i0 _at this moment is greater than 45; and when X is preferably 30%, and Y is preferably 70%, the garbage The initial hydraulic gradient of the clay cushion in the landfill can reach 60, the permeability coefficient of the clay cushion in the landfill basically reaches the minimum, and the initial hydraulic gradient i ₀ basically reaches the maximum (as shown in Figure 1). When the hydraulic gradient i of the buried clay cushion is less than i ₀ , it can completely block the infiltration of water. The effective porosity of the clay cushion in the landfill is ≤8.5% (and greater than 0). Since there is a certain amount of bound water in the clay, the effective porosity is the total porosity minus the porosity corresponding to the bound water. Considering that the highest leachate water level in my country is generally ≤12m, the thickness of the clay cushion of the above-mentioned landfill site needs to be ensured to be ≥20cm, so as to completely block the infiltration of water.

The preferred embodiment of the present invention will be described in detail below in conjunction with accompanying drawing:

Example 1

This embodiment provides an impermeable clay cushion at the bottom of a landfill site, which is formed by mixing kaolinite clay and illite clay with an appropriate amount of water, stirring evenly, and compacting. Kaolinite clay is mainly kaolinite clay. The specific mineral components are: 71wt% kaolinite, 7wt% illite, 6wt% montmorillonite and 16wt% quartz. The clay is dried, crushed and screened. Particles with a particle size of less than 1 mm were obtained (the optimal moisture content of the clay was measured to be 19.70 wt%). Illite clay is mainly illite clay. The specific mineral components are: 11wt% kaolinite, 58wt% illite, 12wt% montmorillonite and 19wt% quartz. Particles with a diameter of less than 1mm (the optimal moisture content of the clay is measured to be 18.80wt%). Mix kaolinite clay and illite clay according to different mass ratios (define the mass of illite clay as a percentage of the total amount of kaolinite clay and illite clay as Y), and the specific amount of illite clay added They are 0%, 10%, 30%, 50%, 70%, and 90%, respectively.

In this example, the above-mentioned ratio of clay is mixed with water, and then ordinary compaction is used to form a clay experimental cushion with a thickness of 4 cm, and it is placed in a flexible wall permeameter to conduct a permeation test. The permeate is deionized water, and the experimental conditions are assumed It is: the garbage body above the cushion layer at the bottom of the landfill is 20m, the garbage density is 1g/cm ³ , and the confining pressure is set to 200kPa. The measured permeability coefficient and initial hydraulic gradient i ₀ are shown in Figure 1 (in Figure 1 The abscissa refers to the amount of illite clay added, that is, the quality of the illite clay accounts for the percentage of the total amount of the kaolinite clay and the illite clay; the ordinate is the permeability coefficient and initial hydraulic gradient of the clay cushion respectively) ; Wherein the quality of adding water accounts for 22% of the dry ingredient quality (the dry ingredient quality is the sum of the quality of kaolinite clay and illite clay). In Fig. 1, as the amount of illite clay increases, the permeability coefficient gradually decreases, but they all meet the k≤1.0×10 ^{- 7cm} /s;

When the addition of illite clay in the mixed clay is ≥30%, the total content of illite and montmorillonite ore in the clay minerals is ≥27%, the porosity is ≤40%, the initial hydraulic gradient i ₀ begins to appear, and the initial hydraulic gradient i ₀ increases with the addition of illite clay. When the addition of illite clay reaches 70%, the permeability coefficient basically reaches the minimum, and the initial hydraulic gradient basically reaches the maximum. At this time, the porosity is 40%, and the effective The porosity is 8.5% (because the bound water is difficult to permeate, therefore, the total porosity minus the porosity corresponding to the bound water is the effective porosity).

Since the drainage layer of real landfills in my country is prone to blockage, resulting in high leachate water level, that is, the highest leachate water level can reach 10-12m, the mixing ratio of 70wt% illite clay and The anti-seepage cushion layer composed of 30wt% kaolinite clay corresponds to 53% of the total mass of illite and montmorillonite in the clay layer to the sum of the mass of kaolinite clay and illite clay (accounting for kaolinite clay and illite clay). The sum of the mass of stone clay), when the laying thickness is 20cm, a completely impermeable anti-seepage cushion can be formed.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention. Equivalent changes or modifications made in the spirit shall fall within the protection scope of the present invention.

Claims (7)

1. an impermeable clay cushion at the bottom of a landfill, characterized in that: it is formed by rolling after kaolinite clay, illite clay and water are mixed, and its porosity≤40%; The quality of kaolinite clay and the percentage of the total amount of kaolinite clay and illite clay is X, 10%≤X<30%; the quality of the illite clay and the kaolinite clay and all The percentage of the total amount of illite clay is Y, 70%<Y≤90%; the percentage of the quality of the water and the total amount of the kaolinite clay and the illite clay is 20-25%; the high The ridge clay and the illite clay are clay particles with a particle size below 1mm. 2. the impermeable clay cushion at the bottom of the landfill according to claim 1, is characterized in that, the mineral composition that comprises following massfraction in described kaolinite clay: Kaolinite 70~75%; Illite 5~10%; Montmorillonite 5~10%; Quartz 10~20%. 3. according to the impermeable clay cushion at the bottom of the landfill according to claim 1 and 2, it is characterized in that, the mineral composition comprising the following mass fractions in the illite clay: Kaolinite 10~15%; Illite 50~60%; Montmorillonite 10~15%; Quartz 15~20%. 4. the impermeable clay cushion at the bottom of the landfill according to claim 1, characterized in that: said X is 30%, and said Y is 70%, and the quality of said water is the same as that of said kaolinite The percentage of clay and the total amount of said illite clay is 22%. 5. The impermeable clay cushion at the bottom of the landfill according to claim 1 or 4, characterized in that: the effective porosity of the clay cushion is ≤8.5%. 6. The impermeable clay cushion at the bottom of the landfill according to claim 4, characterized in that: when the leachate water level is ≤ 12m, the thickness of the clay cushion is ≥ 20cm. 7. The application of the impermeable clay cushion at the bottom of the landfill as claimed in any one of claims 1 to 6 in landfill, characterized in that: construction at the bottom of the landfill in advance Form the clay cushion with a thickness greater than or equal to 20 cm, and then landfill the garbage.