CN108914979B - Landfill capping layer and preparation method and application thereof - Google Patents
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Abstract
The invention discloses a top sealing layer of a refuse landfill and a preparation method and application thereof, belonging to the technical field of refuse landfill. This capping layer includes the functional layer of at least three-layer, the functional layer outside-in stacks gradually and is equipped with: the water storage layer is mainly composed of recycled fine aggregate with the particle size smaller than 5 mm; the guide and discharge layer is mainly composed of recycled coarse aggregates with the particle size of 10mm-40 mm; the low permeability layer is mainly composed of natural soil; the recycled fine aggregate and the recycled coarse aggregate are obtained by processing construction waste. The capping layer is composed of recycled building garbage aggregate and natural soil which are combined according to the particle sizes, can effectively achieve the functions of seepage prevention and air closure, and has the characteristics of 'filling garbage with garbage', recycling building garbage, releasing the occupied storage capacity of the building garbage in a landfill site, greatly reducing the consumption of soil resources compared with the traditional soil capping layer, along with simple construction, convenient material taking, low cost, good durability and the like.
Description
Technical Field
The invention relates to the technical field of refuse landfill, in particular to a refuse landfill capping layer and a preparation method and application thereof.
Background
In recent years, with the continuous and rapid development of national economy and the accelerated progress of urbanization in China, municipal solid waste is also in a rapidly increasing situation. According to the implementation condition report of the solid waste pollution environment prevention and control law of the people's republic of China, the generation amount of the urban solid waste in China is continuously increased, the solid waste pollution prevention and control situation is gradually severe, wherein about 18 hundred million tons of construction waste are generated in China every year, and large and medium cities in the nation 2/3 are in a ' refuse surrounding city ' situation.
The treatment methods of municipal solid waste are mainly classified into landfill, incineration and composting. Among them, the landfill method is the final means of garbage disposal and is also the main mode of garbage disposal in China at the present stage. Generally, at the end of a landfill site, a capping system, i.e. a covering layer (or capping layer), is provided, which functions as: "seepage control", namely prevent rainfall, surface runoff, groundwater, etc. from infiltrating and entering the rubbish body, thus reduce the output of percolate; 2. the gas is blocked, namely the diffusion of landfill gas is reduced, and the greenhouse effect is reduced.
At present, most of domestic refuse landfill covering layers are single compacted clay covering layers or geotechnical composite covering layers consisting of compacted clay layers and geomembranes. However, a single compacted clay coating can exhibit drying cracks in the dry air that affect coating performance. Geomembranes have the problems of easy sliding and instability along an interface, poor durability and the like.
In the conventional art, an alternative soil covering (also called transpiration covering system) based on the principle of water storage-release has appeared, which is mainly of two types, namely a single soil covering and a capillary-retarding covering. The former is formed by planting vegetation on only one layer of fine soil with good water storage capacity, and the latter is formed by laying one layer of coarse soil below one layer of fine soil, and the capillary blocking effect at the interface of the coarse and fine layers is utilized to increase the water storage capacity of the upper fine soil layer. The working principle of the covering layer is similar to that of a sponge, moisture is absorbed and stored in wet seasons, and moisture is released through surface evaporation and plant transpiration in dry seasons, so that water balance under dry and wet weather conditions is realized, and the leakage of rainwater to a landfill body through the covering layer is reduced. However, both forms of soil cover are only suitable for arid areas with less rainfall and the cover is thicker and not suitable for wet areas and neither has a gas lock function.
In order to overcome these two drawbacks of the conventional soil covering, chinese patent CN201310339617.1 proposes a new covering system consisting of a clay layer and a capillary retarding covering layer, wherein the clay layer is disposed under the capillary retarding covering layer, and the capillary retarding covering layer consists of a silt layer and a gravel layer under the silt layer. The covering layer can realize all-weather anti-seepage air-blocking function.
However, all of the above soil coverings have the following drawbacks:
(1) a large amount of soil resources are consumed. Along with the acceleration of urbanization, the land resources are in more and more shortage, and the soil resources are in more and more shortage. The covering layer needs to use a large amount of natural soil or artificial soil materials, which causes difficulty in obtaining materials and aggravates shortage of soil resources; in addition, large amounts of soil resources need to be transported and allocated from outside, increasing the overburden construction cost.
(2) The covering layer material is not green and environment-friendly, and the construction waste of the landfill site cannot be fully utilized. A large amount of solid garbage in the landfill is building garbage, and the building garbage is simply filled and not recycled, so that on one hand, a large amount of waste of resources is caused, and on the other hand, the building garbage occupies a large amount of storage capacity of the landfill, and the economic benefit and the social benefit of the landfill are also reduced.
(3) Occupying the storage capacity of the landfill. CN201310339617.1 relates to a covering layer with a thickness of about 0.8-1.7m, and a conventional single soil covering layer with a height of up to 2 m. Obviously, the soil covering layer greatly occupies the storage capacity of the landfill, so that the actual garbage landfill amount of the landfill is reduced, and the economic benefit and the social benefit of the landfill are reduced.
(4) Affecting the stability of the garbage body. Generally, to increase the storage capacity of the landfill site, the landfill is configured to be sloped. After the covering layer is arranged on the slope type garbage body, the slope inclination angle can be restricted by the stability of the covering layer on the slope, and further the storage capacity of a landfill site is influenced. A large amount of fine soil materials are generally needed in the traditional soil covering layer, the internal friction angle of the soil is generally small, the soil covering layer is arranged on a slope type garbage body, and the problem of slope instability can occur when the slope is large.
At present, no soil covering layer for solving the defects is available at home and abroad.
Chinese patent CN201410456697.3 also proposes a final covering system of a domestic garbage landfill, which comprises an exhaust layer, an impermeable layer, a drainage layer and a vegetation layer, wherein the natural aggregate or artificial material is replaced by garbage incinerator slag as the main component of the exhaust layer and the drainage layer, and MSW compost products and biochar are added into the vegetation layer.
However, the domestic waste incinerator slag and the gravels are adopted as materials of the air exhaust layer and the water drainage layer, and the air exhaust layer and the water drainage layer are not anti-seepage and air-tight functional layers and only play a dredging function, so the domestic waste incinerator slag in the patent is not a main functional material for constructing a covering layer, and the patent scheme still needs to use a large amount of natural soil resources in practice. On the other hand, the domestic garbage incinerator slag and the gravel are used as materials of the exhaust layer and the drainage layer, and the functional requirements only require the permeability coefficient of the domestic garbage incinerator slag and have no other special requirements; and the domestic garbage has more organic matters and extremely complex material components, the shape, the components, the physics, the mechanics, the chemistry and other characteristics of the slag generated after incineration are not good, and the constructed final covering system has poor seepage-proofing and gas-sealing effects. On the other hand, the vegetable layer is arranged in the functional layer of the covering layer and is thin (the vegetable layer is only 20-30 cm), so that the water storage capacity of the vegetable layer is low, and the patent scheme is not suitable for wet areas with much rainfall.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a top sealing layer of a refuse landfill, a preparation method and application thereof.
In order to achieve the purpose, the following technical scheme is adopted:
the utility model provides a landfill capping layer, includes the functional layer of at least three-layer, the functional layer outside-in stacks gradually and is equipped with: the water storage layer is mainly composed of recycled fine aggregate with the particle size smaller than 5 mm; the guide and discharge layer is mainly composed of recycled coarse aggregates with the particle size of 10mm-40 mm; the low permeability layer is mainly composed of natural soil; the recycled fine aggregate and the recycled coarse aggregate are obtained by processing construction waste.
In the top sealing layer of the refuse landfill, the top sealing layer can effectively realize the functions of seepage prevention and air closure by recovering the building refuse aggregate and the natural soil with the combination of the particle sizes, has the functions of refuse landfill, recycling the building refuse and releasing the storage capacity occupied by the building refuse in the landfill, greatly reduces the consumption of soil resources compared with the traditional soil covering layer, and has the characteristics of simple construction, convenient material taking, low cost, good durability and the like; in addition, the stability of the covering layer of the landfill can be obviously improved due to the higher strength of the recycled aggregate, and the gradient of the garbage body of the landfill can be larger, so that the storage capacity of the landfill is increased.
Specifically, the water storage layer mainly functions to absorb and store water under the rainfall condition, and releases the stored water to the atmosphere under the surface evaporation effect under the drought condition; according to experimental research, a large number of micro cracks and mortar surface pores exist on the surface of the recycled aggregate prepared from the construction waste, so that the specific surface area of the aggregate is greatly increased; under the combined action of the microcracks and the surface tension of water, the recycled aggregate has good hydrophilicity and higher water content than natural aggregate. Therefore, when the fine particles are sufficiently large, i.e., the recycled fine aggregate having a particle size of less than 5mm has a good water storage capacity, it can maximally absorb and store water as a water storage layer. On one hand, the drainage guide layer has good permeability and drainage guide capability, on the other hand, the regenerated fine aggregate layer formed by combining the water storage layer with the particle size and the regenerated coarse aggregate of the drainage guide layer positioned below the water storage layer can effectively form a capillary retardation layer, a larger capillary retardation effect can be formed on the interface of the two layers, and the water storage capability of the water storage layer of the regenerated fine aggregate is obviously improved.
The principle of the capping layer for realizing the anti-seepage function is as follows:
when raining, rainwater flows down along the slope on one hand, and on the other hand, the rainwater seeps into the top sealing layer and is stored in the water storage layer; when moisture continuously infiltrates to an interface between the recycled fine aggregate of the water storage layer and the recycled coarse aggregate of the drainage guide layer, the capillary retardation of the interface of the fine layer and the fine layer can retard the moisture from infiltrating into the drainage guide layer, and at the moment, the moisture can move towards the slope toe of the landfill garbage along the interface, so that the water storage capacity in the water storage layer is improved; when the water in the water storage layer exceeds the storage capacity of the water storage layer, the water breaks through the capillary retardation and enters the drainage guide layer; at the moment, because the saturated permeability coefficient of the drainage guide layer is far greater than that of the low-permeability layer, most of water can move to the slope bottom of the landfill garbage body along the drainage guide layer and less enters the low-permeability layer; the presence of the low permeability layer thus allows the moisture entering the waste mass to be greatly reduced.
Therefore, under the combined action of slope runoff, water storage of the water storage layer, lateral drainage on the drainage guide layer and blocking of the low-permeability layer, the top sealing layer can also realize a good anti-seepage function in a wet area.
The principle of realizing the gas-closing function of the capping layer is as follows:
under the action of the capillary retardation protective layer formed by the recycled aggregate of the construction waste, the natural soil of the low-permeability layer can maintain higher saturation. According to the basic principle of unsaturated soil mechanics, the permeability coefficient of soil at a higher saturation degree is very low, so that the gas escape of a landfill is effectively reduced.
In addition, under the protection of the capillary retardation layer formed by the construction waste recycled aggregate, the low-permeability layer can maintain higher water content, and further the natural soil of the low-permeability layer is effectively prevented from generating shrinkage cracks, so that the damage of the clay shrinkage cracks in the traditional single compacted clay covering layer or the geotechnical composite covering layer consisting of the compacted clay layer and the geomembrane to the seepage-proofing and air-blocking performance of the capping layer is avoided.
In actual operation, on the premise of ensuring the technical requirements, the natural soil of the low-permeability layer is preferably selected from natural soil with short distance around the landfill, wide distribution, convenient material taking and low cost.
In one embodiment, the saturation permeability coefficient of the water storage layer is 1 × 10-6m/s~1×10-4m/s, and the saturated permeability coefficient of the drainage layer is not less than 1 × 10-1m/s, the permeability coefficient of the low-permeability layer is not more than 1.0 × 10- 7m/s. The permeability coefficient of each functional layer is controlled within the range, so that a better capillary retardation effect can be achieved.
Furthermore, the recycled fine aggregate used for the water storage layer has good water storage and water retention capacity so as to absorb and store water to the maximum extent in humid climates. The regenerated coarse aggregate of the drainage guide layer and the regenerated fine aggregate of the water storage layer form a good capillary blocking effect so as to improve the water storage capacity of the water storage layer, and the requirement is that the two layers have a large air inlet value difference, for example, the air inlet value of the regenerated coarse aggregate serving as the drainage guide layer material is less than 1 kPa.
Further, the low permeability layer natural soil should maintain a high saturation (i.e., high water content) during operation of the overburden system, avoid the occurrence of shrinkage cracks, and maintain a low gas permeability coefficient. And in the preferable construction stage, the low-permeability layer is compacted under the optimal water content.
In one embodiment, the compacted relative density of the water storage layer is not lower than 0.9, the compacted relative density of the drainage guide layer is not lower than 0.9, and the compaction degree of the low-permeability layer is not lower than 90%. The functional layers are arranged according to the design, so that a good anti-seepage and air-tight function can be achieved.
In one embodiment, the thickness of the water storage layer is 0.6-1.0m, the thickness of the drainage guide layer is 0.4-0.6m, and the thickness of the low-permeability layer is 0.6-1.0 m. The functional layers are arranged according to the design, so that a good anti-seepage and air-tight function can be achieved.
Furthermore, the recycled fine aggregate used in the water storage layer has good water storage and water retention capacity so as to absorb and store water to the maximum extent in humid climates. Furthermore, in order to increase the water storage capacity of the water storage layer, the thickness of the water storage layer can be increased, and meanwhile, the recycling of the construction waste is increased.
In one embodiment, water-permeable and air-permeable insulating material layers are arranged between the functional layers. The insulating material is preferably geotextile. Because the particle size difference of the natural soil, the recycled fine aggregate and the recycled coarse aggregate in each functional layer is large, the geotextile is paved in advance to prevent the mutual mixing condition from being generated in order to prevent the material with small particles from falling into the material with large particles.
In one embodiment, the functional layer further comprises a gas exhaust layer, the gas exhaust layer is arranged in the low permeability layer and mainly consists of recycled coarse aggregate with the grain diameter of 10mm-40mm, the thickness of the gas exhaust layer is 0.2m-0.4m, and the compacted relative density is not lower than 0.7. The exhaust layer is arranged between the low-permeability layer and the garbage body, so that the landfill gas is convenient to collect.
The invention also discloses a preparation method of the top sealing layer of the refuse landfill, which comprises the following steps:
preparing materials: crushing the construction waste to a preset particle size to obtain the recycled fine aggregate and the recycled coarse aggregate, and taking natural soil of a refuse landfill;
laying: and paving the functional layers with recycled fine aggregate, recycled coarse aggregate or natural soil according to preset requirements.
The preparation method directly adopts the construction waste to crush and obtains raw materials of each functional layer on the site of a landfill, has the characteristics of convenient material obtaining and low cost, and achieves the green and environment-friendly effect of landfill waste by garbage.
Furthermore, the production and processing of the recycled fine aggregate and the recycled coarse aggregate can refer to the production specifications of recycled aggregate of construction engineering (such as the recycled coarse aggregate for GB/T25177-2010 concrete and the DB 894.1-recycled sand powder application technical rules (Shanghai) and the like) so as to facilitate large-scale industrial production and reduce the process difficulty and the production cost.
In one embodiment, after the laying step, the step of arranging the guide and drainage channels is further included, and the guide and drainage channels are arranged at intervals of 20-50m on the outer slope surface of the top sealing layer of the garbage body and/or are arranged around the slope toe of the garbage body.
In one embodiment, in the laying step, a water-permeable and air-permeable insulating material layer is laid between the functional layers, and the degree of compaction and the water content of each functional layer are controlled according to predetermined requirements. The compactness is controlled and the optimal water content is matched, so that the water storage capacity of the water storage layer is improved, and the lower air permeability coefficient is maintained.
The invention also discloses application of the landfill capping layer in construction of landfill capping.
Compared with the prior art, the invention has the beneficial effects that:
(1) under humid or arid climate, rainwater can be effectively prevented from permeating into the landfill garbage body, and gas generated by the garbage body is prevented from entering the atmosphere, so that all-weather anti-seepage and air-tight functions are realized.
(2) The garbage is filled with garbage, so that the recycling of the construction garbage is realized, the energy is saved, the emission is reduced, and the environment is protected. The invention creatively provides the method for recycling the construction waste to prepare the recycled aggregate by using the construction waste landfill, and the recycled aggregate is used for landfill sites and other civil engineering, thereby realizing the recycling of the construction waste, saving energy, reducing emission and being green and environment-friendly; the domestic garbage used in the conventional technology does not have corresponding hydrophilicity and water storage capacity.
(3) The soil resource is saved, and the shortage of the soil resource is relieved. Compared with the traditional soil covering layer, the covering layer consumes less soil resources, and can effectively relieve the shortage situation of domestic soil.
(4) A large amount of construction waste of the landfill is consumed, and the storage capacity of the construction waste is released. The invention relates to a top sealing layer and a preparation method thereof, which treat the construction waste of the landfill into recycled aggregate, use the recycled aggregate made by the construction waste in the top sealing layer, and the redundant recycled aggregate can be sold in other civil engineering, thus effectively consuming and utilizing the construction waste, releasing the storage capacity occupied by the construction waste in the landfill and improving the economic benefit and social benefit of the landfill.
(5) The construction is simple, the material is convenient to obtain, and the manufacturing cost is low. The capping layer related by the invention is mainly made of building garbage and a small amount of other natural soil materials in a landfill, so that the problems that a large amount of soil resources need to be transported from the outside and the material cost and the transportation cost are high in the traditional soil covering layer are avoided; in addition, the recycled aggregate made of the construction waste has simple construction process, is convenient to use large-scale machinery and has low construction cost when constructing a covering layer. Therefore, the capping layer has the characteristics of convenient material acquisition, low material cost, simple construction, low manufacturing cost and the like.
(6) Good durability, simple later maintenance and low cost. The capping layer materials are recycled building aggregate and natural soil, and have the advantages of good material stability and durability, stable capping layer structure, simple maintenance and low maintenance cost.
(7) And the stability of the top sealing layer of the landfill is improved. From the mechanical angle analysis, compared with silt and sandy soil, the strength of the recycled coarse aggregate and the recycled fine aggregate of the construction waste is higher, and the recycled coarse aggregate and the recycled fine aggregate have higher internal friction angles (or natural repose angles). When the capping layer made of the construction waste is laid on the landfill waste body, the strength of the capping layer can be greatly improved, so that the stability of the capping layer of the landfill is improved. In addition, under the capping layer, the gradient of the landfill garbage can be larger, so that the storage capacity of the landfill is increased.
Drawings
FIG. 1 is a schematic structural view of a top-sealing layer according to example 2;
FIG. 2 is a graph showing the grain composition of the top-sealing layer construction material according to example 2
FIG. 3 is a schematic view of the principle of permeation prevention and air impermeability of the top sheet according to example 2;
the figure is as follows: 100. a water storage layer; 200. a guide and discharge layer; 300. a low permeability layer; 400. an exhaust layer; 500. a waste body; 510. landfill gas; 600. rain water; 610. slope runoff; 630. lateral guide row; 700. an insulating material layer; 800. and a guide and discharge channel.
Detailed Description
The invention will be described in detail with reference to the drawings and specific embodiments, which are illustrative and not limiting.
Example 1
The utility model provides a landfill capping layer, includes the functional layer of at least three-layer, the functional layer from outside to inside (or from top to bottom) stacks gradually and is equipped with: the water storage layer is mainly composed of recycled fine aggregate with the particle size smaller than 5 mm; the guide and discharge layer is mainly composed of recycled coarse aggregates with the particle size of 10mm-40 mm; the low permeability layer is mainly composed of natural soil; the recycled fine aggregate and the recycled coarse aggregate are obtained by processing construction waste.
Example 2
A top sealing layer of a refuse landfill is constructed by building refuse. As shown in fig. 1, the capping layer includes four stacked functional layers, which are, from outside to inside (or from top to bottom): the water storage layer 100, the drainage guide layer 200, the low permeability layer 300, the exhaust layer 400, and an insulating material layer 700 between the functional layers.
The characteristics and requirements of the functional layers are as follows:
the water storage layer 100 is constructed by recycled fine aggregate made of crushed construction waste, the thickness is 1m, the maximum particle size of the recycled fine aggregate is less than 5mm, and the saturation permeability coefficient is 2 × 10 by measurement-5m/s ~1×10-4m/s, compacted relative density 0.9.
The guide and discharge layer 200 is made of recycled coarse aggregate made of pulverized construction waste, has a thickness of 0.6m, and has a particle size of 10-40mm, and has a saturation permeability coefficient of 1.6 × 10-1m/s, compacted relative density 0.9.
The low permeability layer 300 is constructed of natural soil, has a thickness of 1m and a saturation permeability coefficient of 1.7 × 10-8m/s is natural sandy clay, and the compactness is 95%.
The exhaust layer 400 is constructed by a layer of recycled coarse aggregate made of crushed construction waste, and the particle size of the particles is 10-40mm, and the thickness of the particles is 0.3 m.
According to the basic theory of soil mechanics, the saturation permeability coefficient of soil is determined by the particle composition. In the capping layer construction material of the embodiment, the saturation permeability coefficient of the material is a main control factor. Therefore, in order to control the saturation permeability coefficient of the covering layer construction material, it is necessary to adjust the particle grading curve thereof, in particular, the content of fine particles in the material. Specifically, fig. 2 is a typical grain grading curve of the building material selected for each functional layer in this embodiment.
However, it is understood that the grain composition shown in the grain composition curve is not exclusive, and can be adjusted according to the characteristics and requirements of different landfills in specific application scenarios.
In addition, in order to prevent the material particles of the upper layer and the lower layer from mixing (particularly, fine particles enter gaps of coarse particles), a layer of water-permeable and air-permeable geotextile is laid among the water storage layer, the drainage layer, the low-permeability layer and the air exhaust layer. It can be understood that the geotextile has the advantages of easily available materials and low cost, and different permeable and breathable other insulating material layers can be selected according to different requirements, and only the permeable and breathable material particles are required to be mixed, so that the upper layer and the lower layer are avoided.
It should be noted that, the parameter selection of each layer of materials of the capping layer and the compaction standard during construction according to the present invention need to fully consider the basic conditions of landform and landform of the landfill site, garbage storage, etc., and the climate conditions of the area where the land and the landform are located, especially the rainfall condition, and are determined strictly according to the relevant national specifications.
Moreover, the top-sealing layer related to the embodiment needs to be provided with the drainage guide channels every 20-50m along the slope, the slope foot is also provided with the drainage guide channel 800 which is convenient for collecting surface water and drainage of the top-sealing layer, and the drainage guide channels can be designed and constructed according to relevant specifications.
The top sealing layer of the refuse landfill is prepared by the following method:
firstly, preparing materials.
Building a construction waste crushing station and preparing recycled coarse aggregate and recycled fine aggregate: building garbage crushing station is set in garbage landfill, building garbage is transported to the crushing station directly, and then the building garbage is crushed, screened, impurity eliminated, ground, stoved, compounded, etc. to prepare coarse aggregate and fine aggregate.
It can be understood that the obtained recycled coarse aggregate and recycled fine aggregate can be used for constructing a landfill top sealing layer on one hand and can also be used for other civil engineering construction on the other hand, such as a landfill middle covering layer; similarly, the materials for constructing the capping layer may be obtained from other landfills or other locations where construction waste comminution sites are located.
Secondly, paving.
1. Preparation of the landfill waste 500: and after the layer of garbage is paved and compacted, flattening the surface of the garbage body.
2. Laying an exhaust layer 400: laying a layer of recycled coarse aggregate as an exhaust layer so as to facilitate the collection of landfill gas, and constructing the exhaust layer according to relevant specifications and the design.
3. Laying a low-permeability layer 300: a layer of water-permeable and air-permeable geotextile is laid on the upper exhaust layer of the garbage body in advance, and then a layer of low-permeability natural soil is laid, wherein the layer of natural soil is required to be configured to have the optimal water content (25 percent in the embodiment) in advance, and then the natural soil is compacted in layers according to the preset compaction degree.
4. Laying a guide and drainage layer 200: firstly laying a layer of water-permeable and air-permeable geotextile on the low-permeability layer, then laying the recycled coarse aggregate on the geotextile, and carrying out layered compaction to prepare the drainage layer.
5. Laying a water storage layer 100: a layer of permeable and breathable geotextile is laid on the drainage guide layer, the recycled fine aggregate is prepared in advance according to the optimal moisture content (12% in the embodiment), then the geotextile is laid on the geotextile and is compacted in layers, and the compaction degree needs to be controlled during compaction, so that the water storage layer is prepared.
6. Arranging a guide and exhaust channel 800: guide and drainage channels are required to be arranged at intervals of 20-50m along the outer slope surface of the top sealing layer of the garbage body, and a guide and drainage channel 800 is also arranged at the slope toe.
Through the steps, the novel green environment-friendly landfill capping layer constructed by the construction waste can be prepared.
As shown in figure 3, the impermeable and airtight principle of the top layer of the embodiment is as follows:
under the condition of natural rainfall, a part of rainwater 600 can form slope runoff 610 and flow down the slope to enter the drainage guide channel 800; another portion of the rain water 600 may seep down into the top-sealing layer. The rainwater entering the top sealing layer continuously seeps into the recycled fine aggregate of the water storage layer 100 under the action of gravity. When moisture continuously infiltrates to the interface between the recycled fine aggregate of the water storage layer 100 and the recycled coarse aggregate of the drainage guide layer 200, the capillary retardation of the interface between the fine layer and the fine layer can retard the moisture from infiltrating into the drainage guide layer 200, and the moisture can move towards the toe along the interface, so that the water storage capacity in the water storage layer 100 is improved. When the water in the water storage layer exceeds the storage capacity of the water storage layer, the water breaks through the capillary retardation and enters the drainage guide layer 200, because the permeability coefficient of the drainage guide layer is far greater than that of the low-permeability layer, most of the water moves towards the slope bottom along the drainage guide layer, and less water enters the low-permeability layer 300; while the presence of the low permeability layer 300 results in a substantial reduction of moisture entering the waste body. Therefore, under the combined action of the slope runoff 610, the water storage layer, the lateral drainage guide 630 of the drainage guide layer and the obstruction of the low-permeability layer, the good seepage-proofing effect can be realized in the humid area.
Also, as can be seen from fig. 3, the principle of the air-lock of the top closure layer of the present embodiment is:
under the action of the capillary retardation protective layer formed by the recycled aggregate of the construction waste, the low-permeability layer 300 can maintain high water content, and according to the basic principle of unsaturated soil mechanics, the permeability coefficient of soil at high saturation is very low, so that the gas escape of a landfill is effectively reduced.
In addition, under the protection of the capillary retardation layer formed by the construction waste recycled aggregate, the low-permeability layer can maintain higher water content, and further the natural soil of the low-permeability layer is effectively prevented from generating shrinkage cracks, so that the damage of the clay shrinkage cracks in the traditional single compacted clay covering layer or the geotechnical composite covering layer consisting of the compacted clay layer and the geomembrane to the seepage-proofing and air-blocking performance of the capping layer is avoided.
In conclusion, compared with the conventional soil capping layer, the novel landfill capping layer constructed by the construction waste can effectively realize the functions of seepage prevention and air closure, has the characteristics of 'filling waste with waste', realizing the recycling of the construction waste, releasing the storage capacity occupied by the construction waste in the landfill, greatly reducing the consumption of soil resources compared with the traditional soil covering layer, along with simple construction, convenient material taking, low cost, good durability and the like; in addition, the recycled aggregate has higher strength, so that the stability of the top sealing of the landfill can be obviously improved, and the gradient of the garbage body of the landfill can be larger, thereby increasing the storage capacity of the landfill.
The technical solutions provided by the embodiments of the present invention are described in detail above, and the principles and embodiments of the present invention are explained herein by using specific examples, and the descriptions of the embodiments are only used to help understanding the principles of the embodiments of the present invention; meanwhile, for a person skilled in the art, according to the embodiments of the present invention, there may be variations in the specific implementation manners and application ranges, and in summary, the content of the present description should not be construed as a limitation to the present invention.
Claims (6)
1. The utility model provides a landfill capping layer which characterized in that: functional layer including four layers, functional layer outside-in stacks gradually and is equipped with: the device comprises a water storage layer, a guide and exhaust layer, a low-permeability layer and an exhaust layer, wherein the water storage layer is mainly composed of recycled fine aggregate with the particle size of less than 5 mm; the guide and discharge layer is mainly composed of recycled coarse aggregates with the particle size of 10mm-40 mm; the low permeability layer is mainly composed of natural soil; the recycled fine aggregate and the recycled coarse aggregate are obtained by processing construction waste;
the saturated permeability coefficient of the water storage layer is 1 × 10- 6m/s ~1×10-4m/s, and the saturated permeability coefficient of the drainage layer is not less than 1 × 10-1m/s, the permeability coefficient of the low-permeability layer is not more than 1.0 × 10-7m/s；
The exhaust layer mainly comprises recycled coarse aggregate with the particle size of 10mm-40mm, the thickness of the exhaust layer is 0.2m-0.4m, and the compacted relative density is not lower than 0.7;
the compacted relative density of the water storage layer is not lower than 0.9, the compacted relative density of the drainage guide layer is not lower than 0.9, and the compaction degree of the low-permeability layer is not lower than 90%; the thickness of the water storage layer is 0.6-1.0m, the thickness of the drainage guide layer is 0.4-0.6m, and the thickness of the low-permeability layer is 0.6-1.0 m.
2. The landfill capping layer of claim 1, wherein: and water-permeable and air-permeable insulating material layers are arranged between the functional layers.
3. The method of making a landfill capping layer of any one of claims 1-2, comprising the steps of:
preparing materials: crushing the construction waste to a preset particle size to obtain the recycled fine aggregate and the recycled coarse aggregate, and taking natural soil of a refuse landfill;
laying: and paving the functional layers by using recycled fine aggregate, recycled coarse aggregate or natural soil according to preset requirements.
4. The method for preparing the top-sealing layer of the refuse landfill according to claim 3, wherein the step of laying further comprises the step of arranging guide and drainage channels at intervals of 20-50m on the outer slope surface of the top-sealing layer of the refuse body and/or around the toe of the refuse body.
5. The method for preparing the landfill capping layer according to claim 3, wherein in the paving step, a water-permeable and air-permeable insulating material layer is paved between the functional layers, and the degree of compaction and the water content of each functional layer are controlled according to predetermined requirements.
6. Use of the landfill capping layer of any one of claims 1 to 2 in the construction of landfill capping.
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| CN111804696B (en) * | 2020-07-15 | 2022-03-01 | 中国科学院武汉岩土力学研究所 | Landfill retardation degradation type closing coverage system, and waterproof, gas-tight and pollutant degradation rate performance test device and method thereof |
| CN114059411A (en) * | 2021-11-17 | 2022-02-18 | 中庆建设有限责任公司 | Sponge urban road |
| CN115012454B (en) * | 2022-05-11 | 2023-11-07 | 武汉轻工大学 | Solid waste base composite refuse landfill covering barrier system and preparation method thereof |
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| CN102319716B (en) * | 2011-06-02 | 2013-02-13 | 福建工程学院 | Covering layer of sanitary landfill |
| CN103572785B (en) * | 2012-08-06 | 2016-03-02 | 香港科技大学 | Garbage loading embeading soil property covering system, method for making and purposes that round-the-clock antiseepage is held one's breath |
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