Farmland underground water storage irrigation system utilizing building solid waste and muck and construction method of farmland underground water storage irrigation system

Abstract

The invention provides a farmland underground water storage irrigation system utilizing building solid waste and muck, a porous water storage layer, an isolation filter layer and a planting soil layer are sequentially arranged on the top surface of an undisturbed soil layer from bottom to top, a plurality of pipelines are laid in the porous water storage layer, the material in the porous water storage layer is building solid waste recycled aggregate, and the material in the planting soil layer is recycled aggregate. The planting soil layer is made of engineering muck and backfilled surface planting soil. The invention further provides a construction method of the farmland underground water storage irrigation system utilizing the building solid waste and the muck and application of the system in agriculture. According to the farmland underground water storage irrigation system utilizing the building solid waste and the muck and the construction method of the farmland underground water storage irrigation system, an underground'sponge body reservoir 'is constructed, rainwater or irrigation water can be efficiently collected and stored, water is continuously supplied to upper-layer crops through the capillary action, and the water supply efficiency is improved. The method has the remarkable beneficial effects of turning waste into wealth, saving water, resisting drought, improving soil and being low in construction cost.

Description

Technical Field

[0001] This invention belongs to the technical field of agricultural water conservancy technology and solid waste resource utilization, and relates to a farmland underground water storage irrigation system utilizing construction solid waste and slag, and its construction method. Background Technology

[0002] Currently, agricultural irrigation in my country faces two major challenges: low water resource utilization efficiency and environmental problems caused by traditional irrigation methods. Traditional flood irrigation and canal water conveyance methods suffer from high water evaporation and significant water loss due to seepage along the way, resulting in serious water waste. Although modern water-saving technologies such as drip irrigation and sprinkler irrigation can effectively improve water use efficiency, their equipment and pipeline systems rely on industrialized products, requiring huge initial construction investments and high maintenance costs, making large-scale promotion and application difficult for large areas of low-value-added farmland.

[0003] Meanwhile, with the acceleration of urbanization in my country, the output of construction solid waste (such as waste concrete and bricks) and engineering spoil is increasing daily, becoming a huge burden on the urban environment. Traditional landfill disposal methods not only occupy a large amount of valuable land resources, but may also cause secondary pollution to soil and groundwater due to the leaching of harmful substances.

[0004] To address the challenges of solid waste disposal, existing technologies have explored various approaches. For instance, Chinese patent CN103787751A discloses a method for preparing recycled composite garden soil using construction waste, while Chinese patent CN103304250A proposes a high-water-retention concrete made from waste red bricks. However, these technologies are mostly focused on small-scale applications such as urban landscaping or non-load-bearing pavements, lacking a systematic solution that utilizes construction solid waste as a core functional material for large-scale application in farmland irrigation infrastructure. Existing technologies treat solid waste disposal and farmland water-saving irrigation as two isolated issues, failing to develop a synergistic technological approach. Furthermore, due to potential pollution risks, relevant regulations strictly limit the direct use of untreated construction solid waste or slag in farmland, resulting in a severe lack of safe and effective utilization methods.

[0005] Therefore, there is an urgent need to develop an innovative technology that can co-process construction solid waste and engineering waste, and achieve water-saving irrigation of farmland in a low-cost, environmentally friendly and efficient manner, so as to solve the two major problems of agricultural water conservation and urban solid waste at the same time. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, and in response to the problems of waste of traditional irrigation water resources, high cost of existing water-saving technologies, difficulty in the disposal of construction solid waste and engineering waste soil and insufficient resource utilization, the purpose of this invention is to provide an environmentally friendly, low-cost, simple structure, and efficient water storage and moisture retention system for farmland underground water storage irrigation using construction solid waste and engineering waste soil, and its construction method.

[0007] To achieve the above and other related objectives, the first aspect of the present invention provides a farmland underground water storage and irrigation system utilizing construction solid waste and slag, and a method for constructing the same.

[0008] The first aspect of the present invention provides a farmland underground water storage and irrigation system utilizing construction solid waste and slag. A porous water storage layer, an isolation and filtration layer, and a planting soil layer are arranged sequentially from bottom to top on the top surface of the original soil layer. Several pipes are laid in the porous water storage layer. The material in the porous water storage layer is recycled aggregate from construction solid waste. The material in the planting soil layer is engineering slag and backfill topsoil.

[0009] A second aspect of the present invention provides a method for constructing an underground water storage and irrigation system for farmland utilizing construction solid waste and slag, comprising the following steps:

[0010] 1) Level and clear the target farmland, excavate the foundation trenches downward according to the ground elevation, compact the bottom of the foundation trenches, lay recycled aggregate from construction solid waste at the bottom of the foundation trenches to form a porous water storage layer, and lay pipelines in the porous water storage layer at the same time.

[0011] 2) Cover the top surface of the porous water storage layer with geotextile to form an isolation and filtration layer, then cover it with engineering waste soil and backfill top planting soil to form a planting soil layer, compact it, and restore it to the original ground elevation.

[0012] The third aspect of the present invention provides the use of a farmland underground water storage and irrigation system utilizing construction solid waste and slag in agriculture.

[0013] As described above, the present invention provides a farmland underground water storage and irrigation system utilizing construction solid waste and slag, and its construction method, which has the following beneficial effects:

[0014] (1) This invention provides an underground water storage and irrigation system for farmland utilizing construction solid waste and slag, and its construction method, aiming to solve the technical problems of insufficient flood control and drought resistance capacity of farmland, low water resource utilization efficiency, and the difficulty in resource utilization of large amounts of construction solid waste and engineering slag. By constructing an underground "sponge reservoir," rainwater or irrigation water can be efficiently collected and stored, and water can be continuously supplied to the upper crops through capillary action. It has significant beneficial effects such as turning waste into treasure, saving water and resisting drought, improving soil, and low construction cost.

[0015] (2) The present invention provides a farmland underground water storage irrigation system and its construction method that utilizes construction solid waste and slag soil, realizing the synergy of solid waste resource utilization and environmental benefits; it uses the huge amount of construction solid waste and engineering slag soil in the city as core functional materials, and makes resource utilization on-site and on a large scale, which not only solves the disposal problem of "garbage surrounding the city", reduces the land occupation and environmental pollution risks of landfill, but also saves valuable natural sand and gravel and other building materials resources, realizing the deep integration of circular economy and ecological agriculture.

[0016] (3) The present invention provides a farmland underground water storage irrigation system and its construction method that utilizes construction solid waste and slag. It is environmentally safe and has strong agricultural applicability. It proposes control requirements for the pH value of the water in the recycled aggregate water storage layer (6.0-8.5) and specifies that carbonization modification treatment must be adopted when the pH value exceeds the standard. This fundamentally solves the technical bottleneck of the high alkalinity of recycled concrete aggregate harming crop growth and ensures the safety of agricultural production.

[0017] (4) The present invention provides a farmland underground water storage and irrigation system utilizing construction solid waste and slag, and its construction method, which has high water-saving efficiency and strong drought resistance: the constructed underground water storage layer is like a huge "sponge reservoir" that can efficiently collect and store rainwater or irrigation water, and significantly improve water use efficiency by reducing surface evaporation and deep infiltration. The water stored underground continuously and stably supplies water to the crop roots through capillary action, which significantly enhances the drought resistance and moisture retention capacity of farmland.

[0018] (5) The present invention provides a farmland underground water storage irrigation system and its construction method that utilizes construction solid waste and slag. The system has low construction cost and wide economic applicability: the main materials of the system are derived from low-value or even negative-value waste, which significantly reduces material costs. The construction process is simple and does not require complex industrial pipelines and expensive irrigation equipment, so the initial construction investment is much lower than that of drip irrigation, sprinkler irrigation and other technologies. It is particularly suitable for the transformation of large areas of low- and medium-yield farmland and for promotion in agricultural areas with limited capital.

[0019] (6) This invention provides a farmland underground water storage and irrigation system utilizing construction solid waste and slag, and its construction method, which improves soil structure and promotes stable and increased yields: Through scientific improvement of construction slag, the resulting planting soil layer is loose, breathable, and rich in organic matter, creating an excellent growth environment for crop roots. A stable supply of underground water effectively prevents seasonal drought from stressing crop growth, providing reliable water conservancy guarantees for stable and increased agricultural yields. Attached Figure Description

[0020] Figure 1 The diagram shown is a cross-sectional view of a farmland underground water storage and irrigation system utilizing construction solid waste and slag, according to the present invention.

[0021] Figure Labels

[0022] 1. Original soil layer

[0023] 2 Recycled aggregate

[0024] 3. Porous aquifer

[0025] 31 First Porous Reservoir Section

[0026] 32 Second porous water storage section

[0027] 4. Pipes

[0028] 5. Isolation Filter Layer

[0029] 6. Planting soil layer

[0030] 7 Crops Detailed Implementation

[0031] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0032] Please see Figure 1 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0033] The first aspect of this invention provides a farmland underground water storage and irrigation system utilizing construction solid waste and slag, such as... Figure 1 As shown, a porous water storage layer, an isolation and filtration layer, and a planting soil layer are arranged sequentially from bottom to top on the top surface of the original soil layer. Several pipes are laid in the porous water storage layer. The material in the porous water storage layer is recycled aggregate from construction solid waste. The material in the planting soil layer is engineering slag and backfill topsoil.

[0034] In the above system, such as Figure 1 As shown, the thickness of the porous water storage layer is 40-120cm, preferably 40-100cm.

[0035] The porous water storage layer, laid beneath the isolation and filtration layer, is composed of large-particle recycled aggregate from construction solid waste to form a highly porosity underground water storage space. The thickness of the porous water storage layer optimizes earthwork volume and construction costs while ensuring sufficient water storage capacity. This thickness is designed based on the region's average annual rainfall, the water requirements of the target crop, and water-saving objectives to provide ample water storage capacity per unit area, meeting the supplementary irrigation needs of the crop throughout one growth cycle.

[0036] In the above system, the recycled aggregate from construction waste is recycled crushed concrete blocks and / or crushed bricks. The source of the recycled aggregate from construction waste is stable and the cost is low.

[0037] In the above system, the pH value of the recycled aggregate from construction solid waste is 6.0-8.5.

[0038] In the above system, the recycled aggregate from construction solid waste is subjected to carbonization modification treatment by introducing carbon dioxide. The carbonization modification treatment conditions are: relative humidity of 60-80%; carbon dioxide (CO2) concentration in the air of the carbonization modification treatment space is 10-20%; and forced ventilation treatment time is 24-72 hours.

[0039] The concentration of carbon dioxide (CO2) is a volume percentage concentration relative to air. This continues until the pH of the aggregate soaking water stabilizes below 8.5.

[0040] Because recycled construction waste aggregates contain calcium hydroxide, they are highly alkaline, causing the pH value of water soaked in their natural state to exceed 8.5. Therefore, these recycled construction waste aggregates must undergo pre-carbonation modification treatment. This involves introducing carbon dioxide into the aggregates, causing them to react with calcium hydroxide to form neutral calcium carbonate (Ca(OH)2 + CO2 → CaCO3 + H2O), thereby permanently and stably reducing the alkalinity of the aggregates to a safe range.

[0041] In the above system, the particle size of the recycled construction waste aggregate is 30-100mm, preferably 30-80mm. As a large-particle-size recycled aggregate, the recycled construction waste aggregate within the above particle size range can comprehensively consider the water storage capacity and structural stability of the porous water storage layer. On the one hand, it can ensure that sufficiently large interconnected pores are formed between the aggregates, thereby obtaining an effective porosity of not less than 35% and achieving efficient water storage. On the other hand, it can maintain the skeletal stability of the aggregate pile, effectively resist the pressure of the various cover soil layers above the porous water storage layer, and prevent porosity decay caused by excessive compaction.

[0042] In the above system, such as Figure 1As shown, the porous water storage layer includes a first porous water storage section and a second porous water storage section from bottom to top. The particle size of the recycled aggregate from construction solid waste in the first porous water storage section is larger than that of the recycled aggregate from construction solid waste in the second porous water storage section.

[0043] In one implementation, such as Figure 1 As shown, several pipes are laid in the second porous water storage section. The pipes are conventional agricultural transport pipes, such as porous corrugated pipes, used for water infiltration, water transport, and water collection.

[0044] In one embodiment, the particle size of the recycled aggregate from construction solid waste in the first porous water storage section is 60-100 mm, preferably 60-80 mm.

[0045] In one embodiment, the particle size of the recycled aggregate from construction solid waste in the second porous water storage section is ≥30mm and <60mm.

[0046] In one implementation, such as Figure 1 As shown, the thickness ratio of the first porous water storage section layer to the second porous water storage section layer is 2:1 to 4:1.

[0047] In the above system, the pipeline is connected to a water source.

[0048] In one embodiment, the pipeline is connected to an input water source selected from an inlet valve, a rainwater collection well, or a monitoring well.

[0049] In the above system, the horizontal spacing between adjacent pipes is 5-10m.

[0050] In the above system, such as Figure 1 As shown, the vertical distance between the top surface of the porous water storage layer and the top surface of the planting soil layer is 30-60cm. This design protects crop roots from waterlogging and allows for adaptation to conventional farming operations.

[0051] In the above system, such as Figure 1 As shown, the material in the isolation filter layer is geotextile.

[0052] In one embodiment, the geotextile is a polypropylene (PP) or polyester (PET) filament needle-punched nonwoven geotextile. It possesses excellent durability and chemical stability.

[0053] In one embodiment, the geotextile has a unit area mass of 150-250 g / m². 2 .

[0054] In one embodiment, the vertical permeability coefficient of the geotextile is not less than 5.0 × 10⁻⁶. -2 cm / s.

[0055] The geotextiles of the above specifications can provide sufficient tensile strength and puncture resistance for the isolation and filtration layer, effectively preventing them from being punctured by the underlying aggregate during construction and long-term use. They also allow water to permeate, ensuring that rainwater or irrigation water can pass through quickly and avoiding the formation of temporary water accumulation on the surface of the isolation layer, thus not affecting the efficiency of water replenishment to the water storage layer.

[0056] In the above system, such as Figure 1 As shown, the thickness of the isolation filter layer is 1-20 mm. The thickness of the isolation filter layer is the same as the thickness of the geotextile.

[0057] In the above system, such as Figure 1 As shown, the thickness of the planting soil layer is 30-50cm. This can meet the growth needs of most shallow-rooted and medium-depth-rooted crops (such as corn, wheat, vegetables, etc.), providing sufficient growth space, water and nutrients for the roots.

[0058] In the aforementioned system, the construction waste refers to conventionally used construction waste, specifically natural soil and rock excavated from the excavation of building foundation trenches, municipal tunnels, and other engineering projects, which is free from industrial pollution. Before use, it must be ensured that it does not contain harmful impurities such as construction waste and domestic waste.

[0059] In the above system, the content limit of harmful components in the engineering waste soil shall comply with the screening value of agricultural land soil pollution risk specified in the national standard GB 15618-2018 "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard".

[0060] Before use, the construction waste soil must be sampled and tested to ensure that its heavy metal and other potential pollutant content meets the requirements of the national standard GB 15618-2018 "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control".

[0061] In the above system, the backfill topsoil is the original topsoil previously stripped from the farmland.

[0062] In the above system, the volume ratio of the engineering waste soil to the backfill topsoil is 6-8:2-3.

[0063] In the above system, an organic matter amendment is also added to the planting soil layer. The organic matter amendment is selected from any one or more combinations of well-rotted farmyard manure, commercial organic fertilizer, and biochar.

[0064] In one embodiment, the volume ratio of the organic matter amendment to the engineering waste soil is 1:5-10.

[0065] The above ratio aims to increase the organic matter content of the improved soil to over 2% and form a stable aggregate structure, thereby significantly improving the soil's water and fertilizer retention capacity, aeration, and microbial activity.

[0066] In the above system, the pH value of the water in the porous water storage layer, the isolation filtration layer, and the planting soil layer is 6.0-8.5. This pH range ensures agricultural safety and is most suitable for crop growth and nutrient absorption.

[0067] In the above system, such as Figure 1 As shown, crops are planted in the planting soil layer, and the crops are shallow-rooted or medium-depth-rooted crops.

[0068] In one embodiment, the shallow-rooted or medium-deep-rooted crops include, but are not limited to, corn, wheat, or vegetables.

[0069] A second aspect of the present invention provides a method for constructing an underground water storage and irrigation system for farmland utilizing construction solid waste and slag, comprising the following steps:

[0070] 1) Level and clear the target farmland, excavate downwards to form a foundation trench, compact the bottom of the foundation trench, lay recycled aggregate from construction solid waste at the bottom of the foundation trench to form a porous water storage layer, and simultaneously lay pipelines in the porous water storage layer.

[0071] 2) Cover the top surface of the porous water storage layer with geotextile to form an isolation and filtration layer, then cover it with engineering waste soil and backfill top planting soil to form a planting soil layer, compact it, and plant crops after restoring it to the original ground level.

[0072] In step 1), the land leveling is carried out using mechanical operations.

[0073] In step 1), the land leveling must ensure that the elevation error within the target area is controlled within ±10cm.

[0074] In step 1), the land leveling process creates a drainage slope across the entire target area, with a slope of 0.2-0.5% (i.e., a decrease in elevation of 0.2 to 0.5 meters per 100-meter horizontal distance). This drainage slope meets design requirements and facilitates the removal of surface runoff during heavy rain.

[0075] In step 1), the clearing involves removing all vegetation and debris from the surface, and stripping and properly stacking the topsoil for subsequent backfilling.

[0076] In one embodiment, the thickness of the topsoil stripping is 20-30 cm.

[0077] In step 1), the depth of the base trench is 50-150cm, preferably 80-150cm.

[0078] In step 1), the compaction process involves using compaction machinery to compact the bottom of the trench.

[0079] In one embodiment, the compaction machinery is a road roller or a frog-type compactor.

[0080] In one embodiment, the compaction coefficient is not less than 0.93, ensuring the bearing capacity of the foundation.

[0081] In step 1), the recycled aggregate from construction solid waste is laid evenly. It can be laid evenly at the bottom of the trench using mechanical or manual methods, ensuring the thickness meets design requirements.

[0082] In step 1), the flatness error of the top surface of the porous water storage layer is controlled within ±5cm.

[0083] In step 1), when the recycled aggregate from construction solid waste is laid, the recycled aggregate with large particle size and the recycled aggregate with small particle size are laid sequentially from bottom to top to form the first porous water storage section layer and the second porous water storage section layer.

[0084] In one embodiment, when the second porous water storage section is laid, pipes are laid simultaneously within the second porous water storage section. The pipes can be laid according to irrigation management needs, and their ports can be connected to inlet valves, rainwater collection wells, or monitoring wells at the field entrance.

[0085] In a preferred embodiment, the horizontal spacing between adjacent pipes is 5-10m.

[0086] In step 2), when covering with geotextile, the overlap width between adjacent geotextiles is not less than 20cm, and the edge of the geotextile in contact with the sidewall of the trench is folded upwards by not less than 20cm. This forms a complete wrapping structure within the trench, effectively preventing lateral and upper soil particles from intruding.

[0087] In step 2), when covering the engineering waste soil and backfilling the topsoil, an organic matter conditioner is also mixed in.

[0088] In step 2), when covering the construction waste and backfilling the topsoil, layered backfilling is adopted, and the loose thickness of each layer is ≤30cm. The layered backfilling involves backfilling the mixed topsoil in layers, and lightly compacting each layer until the design elevation is reached.

[0089] In step 2), the compaction is carried out mechanically or manually.

[0090] In one embodiment, the machine is a small compactor.

[0091] In step 2), the dry density of the compacted soil is controlled at 1.4-1.6 g / cm³. 3 The compaction is light, which ensures that the soil layers are tightly bound together while maintaining looseness and aeration, avoiding excessive compaction that could negatively impact crop root growth.

[0092] The third aspect of the present invention provides the use of a farmland underground water storage and irrigation system utilizing construction solid waste and slag in agriculture.

[0093] The core of the above-mentioned underground water storage and irrigation system for farmland utilizing construction waste and slag, and its construction method, lies in the following: First, a porous water storage layer composed of large-particle recycled aggregates from construction waste (such as crushed concrete blocks and brick fragments) is laid to form an underground water storage space. This is then covered with an isolation and filtration layer (such as geotextile) to prevent soil particles from seeping in and causing blockages. The top layer is a planting soil layer composed of construction slag and the original topsoil stripped and preserved before cultivation, providing a medium for crop growth. Simultaneously, the pH value of the water within the water storage layer is strictly controlled. If the pH value naturally exceeds 8.5 due to the recycled aggregates, it must be carbonized to reduce alkalinity, thereby ensuring a suitable environment for crop growth.

[0094] The above-mentioned farmland underground water storage and irrigation system and its construction method utilize construction solid waste and slag soil to transform farmland into a huge "sponge". The skeleton structure formed by large pieces of construction solid waste serves as an underground "water storage layer", which is covered with improved construction slag soil as a "planting layer", thereby realizing the on-site absorption, storage and utilization of rainwater and irrigation water.

[0095] Example 1

[0096] The target farmland was leveled to ensure that the elevation error within the target area was controlled within ±10cm, and a drainage slope of 0.35% was formed on the surface of the entire target area. The land surface was cleared, the topsoil was stripped to a thickness of 25cm, and a foundation trench with a depth of 100cm was excavated. The bottom of the foundation trench was compacted.

[0097] A porous water-retaining layer was formed by manually and evenly laying recycled construction waste aggregate on the undisturbed soil layer at the bottom of the foundation trench. The flatness error of the top surface of the porous water-retaining layer was controlled within ±5cm. The recycled construction waste aggregate consisted of recycled crushed concrete blocks and brick fragments with a particle size of 30-80mm to ensure sufficiently large pores for water storage. Sampling tests showed that the pH value of the water soaked with the recycled aggregate after 24 hours was 12.1, far exceeding the safe upper limit of 8.5. Therefore, before laying, all recycled aggregate underwent carbonization modification treatment with forced ventilation at a relative humidity of 70% and a carbon dioxide concentration of 15% for 48 hours. After treatment, the pH value of the soaking water was tested again, and it remained stable at 8.2, meeting the requirements.

[0098] The porous water storage layer is 50cm thick and consists of a first porous water storage section and a second porous water storage section from bottom to top. The thickness ratio of the first porous water storage section to the second porous water storage section is 3:1. The particle size of the recycled construction waste aggregate in the first porous water storage section is 60-80mm, while the particle size of the recycled construction waste aggregate in the second porous water storage section is ≥30mm and <60mm. This configuration meets the local rainfall and crop water requirements. To facilitate rapid water injection and distribution, pipes are laid simultaneously within the second porous water storage section of the porous water storage layer. The pipes are porous corrugated pipes, with a horizontal spacing of 5m between adjacent pipes. One end of each pipe can be connected to a rainwater collection well at the edge of the field.

[0099] A geotextile is used to completely cover the top surface of the porous water storage layer to form an isolation and filtration layer. The geotextile is a polypropylene filament needle-punched nonwoven geotextile with a unit area mass of 200 g / m². 2 The vertical permeability coefficient of the geotextile is 5.0 × 10⁻⁶. -2 cm / s. The overlap width between adjacent geotextiles is 20cm, and the edge of the geotextile in contact with the sidewall of the trench is folded upwards by 20cm, forming a complete wrapping structure within the trench. This effectively prevents fine particles from the upper planting soil layer from entering the porous water storage layer, avoiding pore blockage after long-term use, while ensuring smooth water infiltration. The thickness of the isolation filter layer is 0.2cm.

[0100] Before use, the construction waste soil must be sampled and tested to ensure that its heavy metal and other pollutant content meets the national standards for agricultural land soil. The qualified clean construction waste soil, topsoil for backfilling, and organic matter conditioner (combined with well-rotted farmyard manure) should be thoroughly mixed in a 7:2:1 volume ratio. Then, the mixed construction waste soil, topsoil for backfilling, and organic matter conditioner should be placed on top of the isolation filter layer to form a planting soil layer. Backfilling should be done in layers, with each layer having a loose thickness of 30cm. Finally, compaction should be performed, and the dry density of the compacted soil should be controlled at 1.5g / cm³. 3The soil is restored to its original surface height. The improved soil in the planting layer is loose, nutrient-rich, and has strong water and fertilizer retention capacity. The planting layer is 50cm thick, thus ensuring a vertical distance of 50.2cm between the top surface of the porous water storage layer and the top surface of the planting layer. The above-described underground water storage and irrigation system for farmland utilizing construction solid waste and slag can meet the root growth needs of most crops, such as corn.

[0101] In practical applications, the irrigation system operates as follows: During the dry season, irrigation water can be piped into an underground porous aquifer via an external water source interface. Water is stored in the pores of the aggregate and, through the capillary action of the insulated filter layer and the overlying planting soil layer, continuously and stably supplies water to the crop root zone. The rainwater harvesting system effectively collects surface runoff during the rainy season. Excess rainwater quickly infiltrates, is filtered through the planting soil layer and the insulated filter layer, and then enters the underground porous aquifer for storage, thus realizing rainwater resource utilization and effectively mitigating waterlogging in farmland.

[0102] Example 2

[0103] The target farmland was leveled to ensure that the elevation error within the target area was controlled within ±10cm, and a drainage slope of 0.4% was formed on the surface of the entire target area. The land surface was cleared, the topsoil was stripped to a thickness of 30cm, and a foundation trench with a depth of 110cm was excavated. The bottom of the foundation trench was compacted.

[0104] A porous water-retaining layer was formed by mechanically and evenly laying recycled construction waste aggregate on the undisturbed soil layer at the bottom of the foundation trench. The flatness error of the top surface of the porous water-retaining layer was controlled within ±5cm. The recycled construction waste aggregate consisted of recycled crushed concrete blocks with a particle size of 40-90mm to ensure sufficiently large pores for water storage. Sampling tests showed that the pH value of the water soaked with the recycled aggregate for 24 hours was 11.8, far exceeding the safe upper limit of 8.5. Therefore, before laying, all recycled aggregate underwent carbonization modification treatment with forced ventilation at a relative humidity of 75% and a carbon dioxide concentration of 20% for 60 hours. After treatment, the pH value of the soaking water was tested again, and it remained stable at 7.9, meeting the requirements.

[0105] The porous water storage layer is 55cm thick and consists of a first porous water storage section and a second porous water storage section from bottom to top. The thickness ratio of the first porous water storage section to the second porous water storage section is 4:1. The particle size of the recycled construction waste aggregate in the first porous water storage section is 60-90mm, while the particle size of the recycled construction waste aggregate in the second porous water storage section is ≥30mm and <60mm. This configuration meets the local rainfall and crop water requirements. To facilitate rapid water injection and distribution, pipes are laid simultaneously within the second porous water storage section of the porous water storage layer. The pipes are porous corrugated pipes, with a horizontal spacing of 7m between adjacent pipes. One end of each pipe can be connected to the inlet valve at the field entrance.

[0106] A geotextile is used to completely cover the top surface of the porous water storage layer to form an isolation and filtration layer. The geotextile is a polyester filament needle-punched nonwoven geotextile with a unit area mass of 170 g / m². 2 The vertical permeability coefficient of the geotextile is 5.5 × 10⁻⁶. -2 cm / s. The overlap width between adjacent geotextiles is 25cm, and the edge of the geotextile in contact with the sidewall of the trench is folded upwards by 25cm, forming a complete wrapping structure within the trench. This effectively prevents fine particles from the upper planting soil layer from entering the porous water storage layer, avoiding pore blockage after long-term use, while ensuring smooth water infiltration. The thickness of the isolation filter layer is 0.2cm.

[0107] Before use, the construction waste soil must be sampled and tested to ensure that its heavy metal and other pollutant content meets the national standards for agricultural land soil. The qualified clean construction waste soil, backfill topsoil, and organic matter conditioner (biochar) should be thoroughly mixed in a 7:2:1 volume ratio. Then, the mixed construction waste soil, backfill topsoil, and organic matter conditioner should be placed on top of the isolation filter layer to form a planting soil layer. Backfilling should be done in layers, with each layer having a loose thickness of 30cm. Finally, compaction should be performed, and the dry density of the compacted soil should be controlled at 1.6g / cm³. 3 The soil is restored to its original surface height. The improved soil in the planting layer is loose, nutrient-rich, and has strong water and fertilizer retention capacity. The planting layer is typically 55cm thick, ensuring a vertical distance of 55.2cm between the top surface of the porous water storage layer and the top surface of the planting layer. This underground water storage and irrigation system utilizing construction waste and slag can meet the root growth needs of most crops, such as wheat.

[0108] In practical applications, the irrigation system operates as follows: During the dry season, irrigation water can be piped into an underground porous aquifer via an external water source interface. Water is stored in the pores of the aggregate and, through the capillary action of the insulated filter layer and the overlying planting soil layer, continuously and stably supplies water to the crop root zone. The rainwater harvesting system effectively collects surface runoff during the rainy season. Excess rainwater quickly infiltrates, is filtered through the planting soil layer and the insulated filter layer, and then enters the underground porous aquifer for storage, thus realizing rainwater resource utilization and effectively mitigating waterlogging in farmland.

[0109] Compare with Examples 1-2

[0110] To verify the beneficial effects of the present invention, comparative experiments were conducted between the following Control Examples 1-2 and Example 1 under the same climatic and geographical conditions. The crop planted was corn, which is relatively sensitive to soil pH.

[0111] Comparative Example 1 (without carbonization treatment): The construction method is exactly the same as in Example 1, but the recycled concrete aggregate used in its aquifer is not carbonized (i.e., the original aggregate with pH=12.1 is used directly).

[0112] Comparative Example 2 (Traditional Farmland): Original farmland that has not undergone any modification, irrigated by surface canal flooding.

[0113] The specific test results after one growth cycle are shown in Table 1 below.

[0114] As shown in Table 1, comparing Example 1 and Control Example 1, the uncarbonized aggregate (Control Example 1) continuously released alkaline substances into the upper soil layer through capillary action, causing the pH value of the planting soil layer to soar to 9.1 at the end of the growing season, severely exceeding the suitable range for maize. This directly led to stunted crop growth, yellowing and necrosis of leaves, and a sharp drop in yield to 210 kg / mu, almost resulting in a complete crop failure. In contrast, in Example 1, which underwent carbonization treatment, the soil pH value remained within a suitable range, the crop grew healthily, and the yield reached as high as 680 kg / mu. This irrefutably proves that the pH control and carbonization modification technology proposed in this invention is the core and key to ensuring the agricultural safety and production efficiency of the system.

[0115] Table 1

[0116] Comparison Projects Example 1 Compare with Example 1 Compare with Example 2 pH value of water used for soaking in aquifer 8.2 (Stable) 11.8 (remaining at a high level) not applicable pH value of planting soil at the end of the growing season 7.6 9.1 7.4 Average plant height of corn (cm) 245 160 230 The proportion of corn leaves turning yellow and dying <5％ >60％ <5％ Average yield of corn per mu (kg / mu) 680 210 590 <![CDATA[Total irrigation water consumption during the whole growth period (m 3 / mu)]]> 95 95 260

[0117] Furthermore, regarding the overall benefits of water conservation and increased yield, compared with Example 1 and Control Example 2 (conventional farmland), the system of the present invention saves approximately 63% in irrigation water consumption, demonstrating a significant water-saving effect. Simultaneously, because the underground aquifer provides a continuous and stable water supply, drought stress is avoided, resulting in a corn yield per acre that is approximately 15% higher than that of conventional farmland.

[0118] In summary, this invention, through the scientific definition of the system structure and key technical parameters, and particularly the creative introduction and verification of pH control and carbonization modification schemes, successfully and safely applies construction solid waste to farmland irrigation facilities. This not only solves the problem of solid waste disposal but also achieves significant water-saving and yield-increasing benefits, demonstrating extremely high practical value and promising prospects for wider application. This invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial utilization value.

[0119] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A farmland underground water storage and irrigation system utilizing construction solid waste and slag, characterized in that, A porous water storage layer (3), an isolation filter layer (5), and a planting soil layer (6) are arranged sequentially from bottom to top on the top surface of the original soil layer (1). Several pipes (4) are laid in the porous water storage layer (3). The material in the porous water storage layer (3) is recycled aggregate from construction solid waste. The material in the planting soil layer (6) is engineering slag and backfill topsoil.

2. The farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in claim 1, characterized in that, Includes one or more of the following conditions: A1) The thickness of the porous water storage layer (3) is 40-120cm; A2) The recycled aggregate from construction solid waste is recycled crushed concrete blocks and / or crushed brick blocks; A3) The pH value of the recycled aggregate from construction solid waste is 6.0-8.5; A4) The recycled aggregate from the building solid waste is subjected to carbonization modification treatment by introducing carbon dioxide. The carbonization modification treatment conditions are: relative humidity of 60-80%; carbon dioxide concentration in the air of the carbonization modification treatment space is 10-20%; and forced ventilation treatment time is 24-72 hours. A5) The particle size of the recycled aggregate from construction solid waste is 30-100mm; A6) The pipe (4) described above is connected to a water source; A7) The horizontal spacing between adjacent pipes (4) is 5-10m; A8) The vertical distance between the top surface of the porous water storage layer (3) and the top surface of the planting soil layer (6) is 30-60cm; A9) The material in the isolation filter layer (5) is geotextile; The thickness of the isolation filter layer (5) described in A10) is 1-20 mm; The thickness of the planting soil layer (6) described in A11) is 30-50cm; The volume ratio of the engineering waste soil to the backfill topsoil in A12) is 6-8:2-3; A13) An organic matter improver is also added to the planting soil layer (6), wherein the organic matter improver is selected from any one or more combinations of well-rotted farmyard manure, commercial organic fertilizer, and biochar. The pH value of the water in the porous water storage layer (3), isolation filter layer (5), and planting soil layer (6) described in A14) is 6.0-8.5; A15) The planting soil layer (6) is planted with crops, which are shallow-rooted or medium-depth-rooted crops.

3. The farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in claim 2, characterized in that, Includes one or more of the following conditions: A61) In item A6, the pipe (4) is connected to an input water source selected from an inlet valve, a rainwater collection well or a monitoring well; A91) In item A9, the geotextile is a polypropylene or polyester filament needle-punched nonwoven geotextile. (A92) In item A9, the unit area mass of the geotextile is 150-250 g / m². 2 ; (A93) In item A9, the vertical permeability coefficient of the geotextile is not less than 5.0 × 10⁻⁶. -2 cm / s; (A131) In item A13, the volume ratio of the organic matter amendment to the engineering waste soil is 1:5-10; (A151) In item A15, the shallow-rooted or medium-deep-rooted crops include corn, wheat, or vegetables.

4. The farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in claim 1, characterized in that, The porous water storage layer (3) includes a first porous water storage section layer (31) and a second porous water storage section layer (32) from bottom to top. The particle size of the recycled aggregate from construction solid waste in the first porous water storage section layer (31) is larger than that of the recycled aggregate from construction solid waste in the second porous water storage section layer (32).

5. The farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in claim 4, characterized in that, Includes one or more of the following conditions: B1) Several pipes (4) are laid in the second porous water storage section (32); B2) The particle size of the recycled aggregate from construction solid waste in the first porous water storage section (31) is 60-100mm; B3) The particle size of the recycled aggregate from construction solid waste in the second porous water storage section (32) is ≥30mm and <60mm; B4) The thickness ratio of the first porous water storage section layer (31) to the second porous water storage section layer (32) is 2:1 to 4:

1.

6. A method for constructing a farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in any one of claims 1-5, comprising the following steps: 1) Level and clear the target farmland, excavate downwards to form a foundation trench, compact the bottom of the foundation trench, lay recycled aggregate from construction solid waste at the bottom of the foundation trench to form a porous water storage layer, and simultaneously lay pipelines in the porous water storage layer. 2) Cover the top surface of the porous water storage layer with geotextile to form an isolation and filtration layer, then cover it with engineering waste soil and backfill top planting soil to form a planting soil layer, compact it, and plant crops after restoring it to the original ground level.

7. The method for constructing a farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in claim 6, characterized in that, Step 1) includes one or more of the following conditions: 11) The land leveling must ensure that the elevation error within the target area is controlled within ±10cm; 12) The land leveling shall create a drainage slope on the surface of the entire target area, wherein the drainage slope is 0.2-0.5%; 13) The clearing of the surface involves removing all vegetation and debris from the surface, and stripping and properly stockpiling the topsoil for subsequent backfilling. 14) The depth of the trench is 50-150cm; 15) The compaction treatment involves using compaction machinery to compact the bottom of the foundation trench; 16) The flatness error of the top surface of the porous water storage layer is controlled within ±5cm; 17) When laying the recycled aggregate from construction solid waste, the recycled aggregate with large particle size and the recycled aggregate with small particle size are laid sequentially from bottom to top to form the first porous water storage section layer and the second porous water storage section layer.

8. The method for constructing a farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in claim 7, characterized in that, Includes one or more of the following conditions: 131) In item 13), the thickness of the topsoil stripping is 20-30 cm; 151) In item 15), the compaction machinery is a road roller or a frog-type compactor; 171) In item 17), when the second porous water storage section layer is laid, the pipeline is laid simultaneously in the second porous water storage section layer; Preferably, the horizontal spacing between adjacent pipes is 5-10m.

9. The method for constructing a farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in claim 6, characterized in that, Step 2) includes one or more of the following conditions: 21) When covering with geotextile, the overlap width between adjacent geotextiles shall not be less than 20cm, and the edge of the geotextile in contact with the side wall of the foundation trench shall be folded upward for not less than 20cm. 22) When covering the engineering waste soil and backfilling the topsoil, an organic matter conditioner is also mixed in; 23) When covering the engineering waste and backfilling the topsoil, the backfilling shall be carried out in layers, and the loose thickness of each layer shall be ≤30cm. 24) The dry density of the compacted soil is controlled at 1.4-1.6 g / cm³. 3 .

10. The use of the farmland underground water storage and irrigation system utilizing construction solid waste and slag as described in any one of claims 1-5 in agriculture.

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