A functional rainwater garden suitable for sponge city

Abstract

The application discloses a functional rainwater garden suitable for a sponge city, which comprises multiple-stage baffling areas which are connected in sequence and have gradually decreasing heights, wherein the multiple-stage baffling areas comprise a first-stage baffling area, a plurality of intermediate-stage baffling areas and a last-stage baffling area; the first-stage baffling area and the intermediate-stage baffling areas are sequentially provided with a first water storage layer and a first cover layer from top to bottom; the last-stage baffling area is sequentially provided with a second water storage layer, a second cover layer, a planting soil layer, a medium sand filtering layer, a geotextile, a storage and infiltration layer, a gravel drainage layer and a water permeation pipe from top to bottom; the first cover layer and the second cover layer comprise gravel and construction waste particles; and the storage and infiltration layer is made of construction waste. The construction waste is used in the construction of the cover layer and the storage and infiltration layer, so that the construction waste piling problem can be solved, the disposal cost can be saved, the environmental pollution can be reduced, the rainwater can be infiltrated in place by using the green land, the rainstorm runoff peak value and rainwater discharge can be reduced, and the groundwater recharge can be increased.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of highway engineering construction, and particularly relates to a functional rainwater garden suitable for a sponge city. BACKGROUND

[0002] Since the Second World War, the urbanization of countries around the world has developed rapidly and is expanding rapidly, and two major urban problems have emerged, one is that a large amount of construction waste is generated every year, and the other is that urban rainwater problems are becoming increasingly serious. With the in-depth development of garbage classification, special garbage treatment will enter the era of targeted treatment. At present, the amount of urban construction waste in China accounts for 30%-40% of the total amount of urban waste. With the acceleration of urbanization, a large amount of construction waste will continuously increase, and how to discharge and treat urban construction waste has become an important issue faced by construction enterprises and environmental protection departments. Construction waste has the property of resource utilization, and more than 95% of it can become raw materials for construction projects after resource utilization. In many developed countries such as Japan and Germany, the resource utilization rate of construction waste has reached more than 90%, and recycling, reusing, and crushing are commonly used. In this way, not only can the hazards caused by the piling up of construction waste be fundamentally solved, but also the construction waste can be turned into "green" building materials for engineering construction, making urban construction sustainable.

[0003] At present, the application and reasonable use of construction waste by practitioners in the landscape industry are still in a relatively fuzzy stage. Scientifically using the regenerated building materials produced by construction solid waste for landscape ecological construction and perfecting the building material system of landscape construction have become urgent problems to be solved.

[0004] In October 2014, the concept of "sponge city" construction in China was proposed, aiming to solve the problems of urban waterlogging, initial rainwater pollution, and river blackening in a more natural and ecological way. As a kind of biological retention facility, the rainwater garden not only meets the requirements of storage and infiltration but also filters and purifies rainwater, effectively reducing the content of pollutants in water. At present, domestic and foreign researches mainly focus on the utilization of urban solid waste in topography, landscape construction, roads and bridges, and small works, but there are few studies on soil composition, especially the relevant products in the market are rarely seen. SUMMARY

[0005] The purpose of the present application is to provide a functional rainwater garden suitable for a sponge city, to realize the reuse of local construction waste in the construction of a "sponge city", and to solve the two existing problems of the disposal of construction waste and the source of good ecological landscape materials.

[0006] To solve the above problems, the technical scheme of the present application is as follows:

[0007] A functional rainwater garden suitable for a sponge city, comprising a plurality of cascade zones connected in series and gradually decreasing in height, wherein the plurality of cascade zones comprise a first cascade zone, a plurality of intermediate cascade zones and a last cascade zone, overflow partition walls are arranged between the first cascade zone and the intermediate cascade zones, between the intermediate cascade zones and between the intermediate cascade zones and the last cascade zone, and overflow openings are formed in the overflow partition walls;

[0008] The first cascade zone and the intermediate cascade zones are sequentially arranged with a first water storage layer and a first cover layer from top to bottom on the upper surface of a plain soil foundation layer, the first cover layer comprises gravel and construction waste particles, and the first cover layer is used for rainwater filtration.

[0009] The last cascade zone is sequentially arranged with a second water storage layer, a second cover layer, a planting soil layer, a medium sand filtration layer, a geotextile, a storage and infiltration layer, a gravel drainage layer and a water permeation pipe from top to bottom on the upper surface of a plain soil foundation layer, the second cover layer comprises gravel and construction waste particles, the storage and infiltration layer is made of construction waste, and the second cover layer, the medium sand filtration layer and the storage and infiltration layer are all used for rainwater filtration.

[0010] Preferably, the storage and infiltration layer sequentially comprises a coarse material layer, a medium coarse material layer and a fine material layer from top to bottom, the thickness of the coarse material layer is 250-350 mm, the thickness of the medium coarse material layer is 100-200 mm, and the thickness of the fine material layer is 20-70 mm.

[0011] Preferably, the porosity of the storage and infiltration layer is 30%-45%, and the density is 1.4-1.8 t / m 3 .

[0012] Preferably, the volume percentage of gravel in the first cover layer and the second cover layer is 30%-50%, and the volume percentage of construction waste particles is 50%-70%.

[0013] Preferably, the thickness of the first water storage layer and the second water storage layer is greater than 150 mm.

[0014] Preferably, the thickness of the medium sand filtration layer is 20-70 mm, and the particle size of the medium sand in the medium sand filtration layer is 5-15 mm.

[0015] Preferably, the thickness of the gravel drainage layer is 250-350 mm, and the particle size of the gravel in the gravel drainage layer is 30-50 mm.

[0016] Preferably, the water permeation pipe is a PVC water permeation pipe, and the diameter of the water permeation pipe is 15-25 mm.

[0017] The above technical scheme is adopted, and the present application has the following advantages and positive effects compared with the prior art:

[0018] 1) The application provides a functional rainwater garden suitable for a sponge city, which comprises multiple-stage baffling areas which are sequentially connected and have gradually decreasing heights, the multiple-stage baffling areas comprise a first-stage baffling area, a plurality of intermediate-stage baffling areas and a last-stage baffling area, wherein the first-stage baffling area and the intermediate-stage baffling areas are sequentially arranged from top to bottom on the upper surface of a plain soil foundation layer with a first water storage layer and a first cover layer, and the last-stage baffling area is sequentially arranged from top to bottom on the upper surface of the plain soil foundation layer with a second water storage layer, a second cover layer, a planting soil layer, a medium sand filter layer, a geotextile, a storage and infiltration layer, a gravel drainage layer and a water permeation pipe, the first cover layer and the second cover layer comprise gravel and construction waste particles, and the storage and infiltration layer is made of construction waste; the first cover layer, the second cover layer, the medium sand filter layer and the storage and infiltration layer are used for rainwater filtration; waste treatment and rainwater resource utilization are two problems that must be faced in urban construction, the functional rainwater garden suitable for the sponge city provided by the application uses construction waste to construct the cover layer and the storage and infiltration layer, which can not only solve the problem of construction waste storage, save disposal cost, reduce environmental pollution, but also use green land to store and infiltrate rainwater, reduce rainstorm runoff peak value and rainwater discharge, and increase groundwater recharge; the storage and infiltration layer is technically feasible, economically reasonable, environmentally friendly, and has flexible application sites and wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A plan view of a multiple-stage baffling area of a functional rainwater garden suitable for a sponge city provided by the embodiment of the application;

[0020] Figure 2 A Figure 1 A main structure diagram of the first-stage baffling area and the intermediate-stage baffling area;

[0021] Figure 3 A Figure 1 A main structure diagram of the last-stage baffling area;

[0022] Figure 4 A rainwater flow direction diagram of a multiple-stage baffling area of a functional rainwater garden suitable for a sponge city provided by the embodiment of the application;

[0023] Figure 5 A plan view of a demonstration point of a functional rainwater garden suitable for a sponge city provided by the embodiment of the application;

[0024] Figure 6 A vertical difference diagram of a demonstration point of a functional rainwater garden suitable for a sponge city provided by the embodiment of the application;

[0025] Figure 7 A current situation photo of a demonstration point of a functional rainwater garden suitable for a sponge city provided by the embodiment of the application.

[0026] Reference signs:

[0027] 1: multi-stage baffle zone; 11: first-stage baffle zone; 111: first water storage layer; 112: first cover layer; 12: intermediate-stage baffle zone; 13: last-stage baffle zone; 131: second water storage layer; 132: second cover layer; 133: planting soil layer; 134: medium sand filter layer; 135: geotextile; 136: storage and infiltration layer; 137: gravel drainage layer; 138: water infiltration pipe; 2: overflow partition wall; 21: overflow port; 3: No. 1 pool; 4: No. 2 pool; A: first-stage baffle zone; B: intermediate-stage baffle zone; C: intermediate-stage baffle zone; D: last-stage baffle zone. DETAILED DESCRIPTION

[0028] The siphon type rapid drainage well cover provided by the present application is further described in detail below in combination with the drawings and specific embodiments. The advantages and features of the present application will be more apparent according to the following description and claims.

[0029] Referring to Figures 1 to 3 shown, the present application provides a functional rainwater garden suitable for a sponge city, referring to Figure 1 shown, the entire functional rainwater garden plane is mainly divided into two large areas, the first large area is a multi-stage baffle zone 1 which is sequentially connected and has a height gradually decreasing in stages, and the second large area is an overflow partition wall 2 arranged between the multi-stage baffle zone 1; the multi-stage baffle zone 1 includes a first-stage baffle zone 11 and a plurality of intermediate-stage baffle zones 12 and a last-stage baffle zone 13, and the overflow partition wall 2 is arranged between the first-stage baffle zone 11 and the intermediate-stage baffle zone 12, between the intermediate-stage baffle zones 12, and between the intermediate-stage baffle zone 12 and the last-stage baffle zone 13, and the overflow port 21 is formed on the overflow partition wall 2, and the first-stage baffle zone 11, the intermediate-stage baffle zone 12 and the last-stage baffle zone 13 have the same function as a traditional filter tank, so that the first-stage baffle zone 11, the intermediate-stage baffle zone 12 and the last-stage baffle zone 13 form a multi-stage purification zone;

[0030] Referring to Figure 2 shown, the first-stage baffle zone 11 and the intermediate-stage baffle zone 12 are sequentially provided with a first water storage layer 111 and a first cover layer 112 on the upper surface of the plain soil foundation layer from top to bottom, and the thickness of the first water storage layer 111 is greater than 150 mm; the thickness of the first cover layer 112 is 20-70 mm, and the first cover layer 112 includes gravel and construction waste particles, wherein the volume percentage of the gravel is 30%-50%, and the volume percentage of the construction waste particles is 50%-70%, the first cover layer 112 is used for rainwater filtration, and the first-stage baffle zone 11 and the intermediate-stage baffle zone 12 mainly play a primary filtration role;

[0031] Referring to Figure 3As shown, the last-stage baffling area 13 is arranged on the upper surface of the soil foundation layer from top to bottom in sequence of the second water storage layer 131, the second cover layer 132, the planting soil layer 133, the medium sand filtering layer 134, the geotextile 135, the storage and infiltration layer 136, the gravel drainage layer 137 and the water infiltration pipe 138. The thickness of the second water storage layer 131 is greater than 150 mm; the thickness of the second cover layer 132 is 20-70 mm, and the second cover layer 132 comprises gravel and construction waste particles, wherein the volume percentage of the gravel is 30%-50%, and the volume percentage of the construction waste particles is 50%-70%; the second cover layer 132 is below the planting soil layer 133; the planting soil layer 133 is below the medium sand filtering layer 134, and the thickness of the medium sand filtering layer 134 is 20-70 mm, and the medium sand filtering layer 134 has a medium sand particle size of 5-15 mm; the bottom of the medium sand filtering layer 134 is provided with a layer of geotextile 135; the geotextile 135 is below the storage and infiltration layer 136, and the storage and infiltration layer 136 is made of construction waste, and the storage and infiltration layer 136 comprises in sequence from top to bottom a coarse material layer, a medium coarse material layer and a fine material layer, wherein the thickness of the coarse material layer is 250-350 mm, the thickness of the medium coarse material layer is 100-200 mm, and the thickness of the fine material layer is 20-70 mm, the porosity of the storage and infiltration layer 136 is 30%-45%, and the density of the storage and infiltration layer 136 is 1.4-1.8 t / m 3 ; the gravel drainage layer 137 is below the storage and infiltration layer 136, and the thickness of the gravel drainage layer 137 is 250-350 mm, and the gravel drainage layer 137 has a gravel particle size of 30-50 mm; the lower part of the gravel drainage layer 137 is arranged with a PVC water infiltration pipe with a diameter of 15-25 mm, and the outside of the last-stage baffling area 13 is tamped with soil; the second cover layer 132, the medium sand filtering layer 134 and the storage and infiltration layer 136 in the last-stage baffling area 13 are all used for rainwater filtration, and the last-stage baffling area 13 is a terminal area for rainwater inflow, and the last-stage baffling area 13 is provided with a multi-layer filter tank (i.e. a functional rainwater garden core) with construction waste as the built-in material, which is specifically manifested in that the second cover layer 132 is composed of construction waste particles, and the storage and infiltration layer 136 with a large void is constructed by using construction waste (the storage and infiltration layer 136 is a space for quickly receiving and retaining rainwater to store rainwater that cannot be infiltrated in time), and the performance of the developed plant root system of the green land surface soil layer and the relatively loose soil with a high rainwater infiltration rate is utilized to make the surface rainwater quickly infiltrate and temporarily store in the storage and infiltration layer 136, and then slowly infiltrate into the underground after rain, which is equivalent to increasing the rainwater infiltration time, so as to achieve the purposes of reducing surface runoff and collecting and utilizing water.

[0032] Example One

[0033] Reference Figure 4As shown, the embodiment provides a functional rainwater garden suitable for sponge city, the entire functional rainwater garden system covers an area of about 100-400 square meters, the entire functional rainwater garden plane is mainly divided into two large areas, the first large area is a plurality of multi-stage baffling areas 1 which are sequentially connected and the height gradually decreases, and the second large area is overflow partition walls 2 arranged between the plurality of multi-stage baffling areas 1; the plurality of multi-stage baffling areas 1 include a first-stage baffling area 11 (A area on the drawing), two intermediate-stage baffling areas 12 (B and C areas on the drawing) and a last-stage baffling area 13 (D area on the drawing), overflow partition walls 2 are arranged between the first-stage baffling area 11 and the intermediate-stage baffling areas 12, between the intermediate-stage baffling areas 12 and between the intermediate-stage baffling areas 12 and the last-stage baffling area 13, overflow openings 21 are formed on the overflow partition walls 2, the first-stage baffling area 11, the intermediate-stage baffling areas 12 and the last-stage baffling area 13 have the same function as the traditional filter tank, so that the first-stage baffling area 11, the intermediate-stage baffling areas 12 and the last-stage baffling area 13 form a plurality of purification areas, and the rainwater flow direction is A→B→C→D;

[0034] Referring to Figure 2 As shown, the first-stage baffling area 11 and the intermediate-stage baffling areas 12 are sequentially provided with a first water storage layer 111 and a first cover layer 112 on the upper surface of the plain ground base from top to bottom, the thickness of the first water storage layer 111 is 150 mm; the thickness of the first cover layer 112 is 50 mm, the first cover layer 112 includes gravel and construction waste particles, the volume percentage of the gravel is 40%, and the volume percentage of the construction waste particles is 60%, and the first cover layer 112 is below a planting soil layer; the overflow openings 21 of the overflow partition walls 2 between the first-stage baffling area 11 and the intermediate-stage baffling areas 12 and between the intermediate-stage baffling areas 12 are vertically arranged in the first water storage layer 111, and the overflow openings 21 of the overflow partition walls 2 are higher than the first water storage layer 111, and the overflow openings 21 are used for the rainwater flow between the baffling areas. The first cover layer 112 is used for rainwater filtration, and the first-stage baffling area 11 and the intermediate-stage baffling areas 12 mainly play a primary filtration role;

[0035] Referring to Figure 3As shown, the terminal area of rainwater inflow is the last-stage baffle area 13, which is arranged on the upper surface of the plain soil foundation layer from top to bottom in sequence with a second water storage layer 131, a second cover layer 132, a planting soil layer 133, a medium sand filtering layer 134, a geotextile 135, a storage and infiltration layer 136, a gravel drainage layer 137 and a water infiltration pipe 138. The thickness of the second water storage layer 131 is 150 mm; the thickness of the second cover layer 132 is 50 mm, and the second cover layer 132 comprises gravel and construction waste particles, wherein the volume percentage of the gravel is 40%, and the volume percentage of the construction waste particles is 60%; the second cover layer 132 is below the planting soil layer 133, which adopts 200 mm thick improved planting soil, and the composition of the planting soil is referred to the relevant mainstream research results in the local area; the planting soil layer 133 is below the medium sand filtering layer 134, which has a thickness of 50 mm and a medium sand particle size of 5-15 mm; the bottom of the medium sand filtering layer 134 is provided with a layer of geotextile 135, which should be as thin as possible to avoid excessive slowing down of the rainwater infiltration speed; the geotextile 135 is below the storage and infiltration layer 136, which adopts construction waste and comprises from top to bottom in sequence a 300 mm thick coarse material layer, a 150 mm thick medium coarse material layer and a 50 mm thick fine material layer. According to experimental measurement, the porosity of the storage and infiltration layer 136 is 30%-45%, and the density is 1.4-1.8 t / m 3 ; the storage and infiltration layer 136 is below the gravel drainage layer 137, which has a thickness of 300 mm and a gravel particle size of 30-50 mm; the lower part of the gravel drainage layer 137 is arranged with a PVC water infiltration pipe with a diameter of 20 mm; the outside of the last-stage baffle area 13 is rammed with plain soil; the second cover layer 132, the medium sand filtering layer 134 and the storage and infiltration layer 136 in the last-stage baffle area 13 are all used for rainwater filtration; the last-stage baffle area 13 is the terminal area of rainwater inflow, and it is provided with a multi-layer filter tank (i.e. a functional rainwater garden core) with construction waste as the built-in material. Specifically, the second cover layer 132 is composed of construction waste particles, and the storage and infiltration layer 136 with large voids is constructed with construction waste (the storage and infiltration layer 136 is a space for quickly receiving and retaining rainwater to store rainwater that cannot be infiltrated in time), and the performance of the developed plant root system of the green land surface soil layer and the relatively loose soil with high rainwater infiltration rate is utilized to make the surface rainwater quickly infiltrate and temporarily store in the storage and infiltration layer 136, and then slowly infiltrate into the ground after rain, which is equivalent to increasing the rainwater infiltration time, achieving the purpose of reducing surface runoff and water collection and utilization.

[0036] Since the rainwater is infiltrated in situ, the pollution of groundwater is avoided, the pollutants are mainly from the construction waste and the rainwater itself, the pollutants of the construction waste can be controlled through the management and sorting of the generation process, and the pollutants in the rainwater are purified through the absorption of plants and the penetration of soil layers. The functional rainwater garden is provided, the main structure of the last-stage baffle area adopts a multi-stage infiltration system to filter, deposit, penetrate, adsorb and absorb the rainfall runoff, so that the heavy metals, organic matters, nitrogen and phosphorus and other pollutants in the runoff are reduced, the absorption and purification of the runoff are realized, the water consumption of the green land is reduced, the urban waterlogging and municipal drainage pressure are reduced, the increasingly depleted groundwater is supplemented to repair the ecology, the construction waste is recycled to reduce the environmental pollution, the heat island effect is alleviated, and the ecological city is constructed.

[0037] Embodiment two

[0038] Referring to Figures 5 to 7 As shown in the figure, the east side of the S18 land block in the Jinqiao park is selected as a demonstration point, a functional rainwater garden suitable for a sponge city is provided, the area is about 400 square meters, the site is originally a small green land mainly with lawns, a large amount of construction waste is mixed in the soil matrix, the water permeability of the site is poor, the surface runoff is basically discharged into the water body on the west side after passing through the west side road, and a large amount of pollutants in the surrounding area are washed into the water body, so that the pollution load of the water body is increased. The concept of rain flood control is given, the form of the site is deeply transformed, and the area is transformed into a demonstration area of the rainwater garden, so that the comprehensive effect of the site can be improved, and the surrounding sites (including the east side parking lot) can be accommodated. Referring to Figure 5 As shown in the figure, the functional rainwater garden demonstration area provided in the embodiment has a regular form, including two rainwater collection and treatment pools, i.e. No. 1 pool 3 and No. 2 pool 4, referring to Figure 6 As shown in the figure Figure 6 Compared with Figure 5The first-stage baffle zone 11 and the second-stage baffle zone 12, and the two second-stage baffle zones 12 are provided with overflow partition walls, overflow openings are formed in the overflow partition walls, and rainwater flows into the second-stage baffle zone 12 from the first-stage baffle zone 11; an overflow partition wall is also arranged between the second-stage baffle zone 12 and the No. 4 pool 4, overflow openings are formed in the overflow partition wall, and after the rainwater is preliminarily purified and stored in the No. 1 pool 3, the excess rainwater flows into the No. 4 pool 4, the No. 4 pool 4 is the last-stage baffle zone 13, the area of the No. 4 pool 4 is about 120 square meters, and the No. 4 pool 4 is the core part of the functional rainwater garden. The No. 4 pool 4 is dug to a depth of 1.2 meters, all the bricks, stones and other garbage in the soil are removed, and then a filler layer and the like are filled again from top to bottom in the following order: a water storage layer with a thickness of not less than 150 mm, a cover layer with a thickness of 50 mm (the main component of the cover layer is construction waste particles), a 200 mm thick improved planting soil (the composition of the planting soil is referred to the mainstream research results in the local area), a 50 mm thick medium sand filter layer, a geotextile layer arranged at the bottom of the medium sand filter layer, a 500 mm thick storage and infiltration layer (the storage and infiltration layer is sequentially composed of a 300 mm thick coarse material layer, a 150 mm thick medium coarse material layer and a 50 mm thick fine material layer), a 300 mm thick gravel drainage layer, and finally a PVC water permeation pipe with a diameter of 20 mm is arranged in the lower part of the gravel drainage layer. The soil outside the main structure is rammed, rainwater entering the No. 4 pool can be further purified, and the treated rainwater can be discharged into the pool on the west side through the overflow pipe. The internal garden road is mainly regular, the paving is performed by using water permeable bricks (pebble filled gaps), a drainage pipe connecting both sides is left in the lower part of the garden road, and a local area is designed in the form of a stepping pool to maintain the water flow and biological flow on both sides. The planting of green plants in the site is configured in a near-natural way, mainly various plants resistant to water and deep-rooted, and through natural configuration, a plant community capable of natural regeneration is formed.

[0039] After the rainwater collection and utilization system of the demonstration point green land of the rainwater garden is built, the following systems are mainly formed: a new type of infiltration channel system including a vegetation grass ditch and a vegetation step, a new type of rainwater biological retention system such as a rainwater garden, a rainwater collection system and a rainwater utilization system.

[0040] At present, nearly one year has passed since the construction of the demonstration case is completed, and good ecological effects are generally achieved, for example, most of the plants in the base grow vigorously, the runoff during heavy rain is obviously reduced, and the water quality is purified, and the current photos of the site are as followsFigure 7 The data show that the total water storage capacity of the rainwater garden demonstration site is 15m 3 , and zero discharge is achieved, which can be said to achieve the expected effect.

[0041] The embodiments of the present application are described in detail above with reference to the drawings, but the present application is not limited to the above-described embodiments. Even if various changes are made to the present application, if the changes fall within the scope of the claims of the present application and equivalent technologies thereof, they still fall within the scope of protection of the present application.

Claims

1. A functional rain garden suitable for sponge cities, characterized in that, It includes a multi-stage baffle zone connected in series with progressively decreasing height. The multi-stage baffle zone includes a first-stage baffle zone, several intermediate-stage baffle zones, and a final-stage baffle zone. Overflow partitions are provided between the first-stage baffle zone and the intermediate-stage baffle zones, between the intermediate-stage baffle zones, and between the intermediate-stage baffle zones and the final-stage baffle zone. Overflow outlets are provided on the overflow partitions. The first-stage baffle zone and the intermediate-stage baffle zone serve as preliminary filters, while the final-stage baffle zone is a multi-layer filter pool with construction waste as the internal material. The first-stage deflection zone and the intermediate-stage deflection zone are provided with a first water storage layer and a first cover layer from top to bottom on the surface of the subgrade soil. The first cover layer includes gravel and construction waste particles and is used for rainwater filtration. The final deflection zone consists of a second water storage layer, a second cover layer, a planting soil layer, a medium sand filter layer, a geotextile, an infiltration layer, a gravel drainage layer, and infiltration pipes arranged sequentially from top to bottom on the surface of the subgrade. The second cover layer contains gravel and construction waste particles, and the infiltration layer uses construction waste. The second cover layer, the medium sand filter layer, and the infiltration layer are all used for rainwater filtration. The infiltration layer consists of a coarse material layer, a medium-coarse material layer, and a fine material layer arranged sequentially from top to bottom. The gravel content in the first and second covering layers is 30% to 50% by volume, and the construction waste particle content is 50% to 70% by volume.

2. The functional rain garden suitable for sponge cities according to claim 1, characterized in that, The thickness of the coarse material layer is 250-350 mm, the thickness of the medium-coarse material layer is 100-200 mm, and the thickness of the fine material layer is 20-70 mm.

3. The functional rain garden suitable for sponge cities according to claim 2, characterized in that, The porosity of the reservoir is 30%–45%, and the density is 1.4–1.8 t / m³.

4. The functional rain garden suitable for sponge cities according to claim 1, characterized in that, The thickness of the first water storage layer and the second water storage layer is greater than 150 mm.

5. The functional rain garden suitable for sponge cities according to claim 1, characterized in that, The thickness of the medium sand filter layer is 20-70 mm, and the particle size of the medium sand in the medium sand filter layer is 5-15 mm.

6. The functional rain garden suitable for sponge cities according to claim 1, characterized in that, The thickness of the gravel drainage layer is 250-350 mm, and the gravel particle size of the gravel drainage layer is 30-50 mm.

7. The functional rain garden suitable for sponge cities according to claim 1, characterized in that, The drainage pipe is made of PVC and has a diameter of 15-25 mm.

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