CN106835890A - Concave herbaceous field system and construction method based on sponge city - Google Patents

Abstract

The invention discloses a concave green space system based on a sponge city, which includes an energy dissipation layer, a concave green belt, an anti-seepage layer, and a gravel blind ditch; the energy dissipation layer includes roadside curbs, pebble energy dissipation pools, fine Stone concrete and pebble energy dissipation pools are placed inside the roadside curb stones, and roadside curb stones and pebble energy dissipation pools are placed on fine stone concrete; an overflow rainwater outlet is provided at the lowest point of the sunken green belt; There is also a settling well; the anti-seepage layer includes cement mortar, asphalt, and anti-seepage composite geomembrane arranged in sequence from top to bottom; the gravel blind ditch is placed at the lowest point of the anti-seepage layer, and there is a Horizontal drainage pipes and soft permeable pipes; fill the gravel blind ditch with coarse sand cushion and gravel layer from top to bottom. The invention also provides a construction method of the sunken green space system based on the sponge city. The invention can realize the infiltration, storage, stagnation, utilization and drainage functions of the sponge city, and achieve good rainwater discharge, collection and utilization effects.

Description

Concave green space system and construction method based on sponge city

technical field

The invention belongs to the technical field of municipal engineering construction, and in particular relates to a sponge city-based sunken green space system and a construction method.

Background technique

In recent years, some cities have experienced serious waterlogging problems after heavy rainfall, which has seriously affected the normal operation of the city and caused serious losses of people's lives and property. Under the guidance of the traditional "drainage-based" stormwater management concept, most of the rainwater collected by cities and towns is quickly discharged into the receiving water body through the municipal rainwater pipe network, and the rainwater is hardly considered infiltration into the soil, resource utilization, etc. . The hardening of the ground in the city has intensified the runoff of rainwater. As the rainwater scours the surface, the pollution of rainwater runoff has also been put on the research agenda.

At present, road surface water and groundwater are excluded from the scope of the ground covered by the subgrade by setting up subgrade pavement drainage systems through accumulation, blocking, isolation, and dredging. The existing subgrade pavement drainage system usually adopts the transverse slope method and the water retaining strip. The transverse ramp method is mainly used for pavements with small water catchment capacity, low embankment height, different slopes and strong anti-scouring ability of the subgrade slope. The water blocking belt is generally suitable for occasions where the water flow has a large scouring force and can quickly discharge surface water. At present, there is another drainage method-central partition drainage. Central partition drainage is usually divided into two types: first, when the width of the central partition is less than 3m, use the cross-section mode with pavement to adopt two-way transverse slopes at both ends of the central partition to flow road water from the middle to the The pavement at both ends of the road, so that it merges into the unified drainage system. Second, when the width of the middle partition is greater than 3m, set a lateral slope for water intrusion, and after concentrating the surface water into the middle depression, the slope inertia will drain it into the lateral subgrade. The above-mentioned treatment methods are all based on "drainage", and lack of consideration for the collection, purification and reuse of rainwater.

In view of the current status and problems of drainage, many cities at home and abroad have begun to practice new stormwater management concepts, combining stormwater infiltration storage technology with urban road design, and building "sponge cities" with the goals of natural accumulation, natural infiltration, and natural purification. The "Opinions of the State Council on Strengthening Urban Infrastructure Construction" (Guofa [2013] No. 36) clearly pointed out that the construction of sunken green spaces and urban wetland parks will enhance the functions of urban green spaces to gather rainwater, flood storage and drainage, replenish groundwater, and purify ecological functions. It can be seen that the sunken green space is of great significance to improve the hydrological regulation and storage function of urban green space.

Contents of the invention

The purpose of the present invention is to provide a sponge city-based concave green space system and construction method, the system and method can realize the functions of seepage, storage, stagnation, utilization and drainage of the sponge city, and achieve good rainwater discharge, collection and utilization effects .

The technical scheme adopted in the present invention is:

A sunken green space system based on sponge city, placed between motor vehicle lanes and non-motor vehicle lanes, including energy dissipation layer, sunken green belt, anti-seepage layer, gravel blind ditch;

There are two energy-dissipating layers, which are respectively placed on the edge of the motor vehicle lane and the non-motor vehicle lane, including roadside curbs, pebble energy dissipation pools, and fine stone concrete. The pebble energy dissipation pool is placed on the fine stone concrete;

The sunken green belt is placed between two energy-dissipating layers, and an overflow rainwater outlet connected to the underground drainage system is provided at the lowest point of the sunken green belt; sand sinking wells are also arranged on the sunken green belt , the sand sinking well is close to the side of the motorway;

The anti-seepage layer is placed under the concave green belt and is in a concave shape, including cement mortar, asphalt, and anti-seepage composite geomembrane arranged sequentially from top to bottom;

The crushed stone blind ditch is placed at the lowest point of the anti-seepage layer, and the crushed stone blind ditch is provided with a horizontal drain pipe and a soft permeable pipe connected with the horizontal drain pipe; in the crushed stone blind ditch from top to bottom Filled with coarse sand cushion, gravel layer.

There are multiple water inlets on the roadside curbs, and the distance between adjacent water inlets is 40m to facilitate rainwater entering the concave green space, and also to ensure the strength of the roadside curbs and improve the service life of the road.

The sunken green belt is arc-shaped, and its lowest point is 0.1-0.3m lower than the edge of the road surface of the motorway, so that the system can achieve optimal storage and discharge functions.

The width of the pebble energy dissipation pool is 0.2-0.3m, and the minimum width is used to reduce the erosion of rainwater on the road, reduce road surface runoff, reduce flood peak flow, and alleviate the flood detention disaster caused by heavy rain on the road.

The elevation of the top of the sand settling well is 0.1m lower than the edge of the road surface of the motorway; there are multiple overflow rainwater outlets, and the distance between adjacent overflow rainwater outlets is 4m, so as to achieve good drainage of excess rainwater with the least input.

The present invention also provides the construction method of the above-mentioned concave green space system based on the sponge city, comprising the following steps:

The first step is to complete the construction of the gravel blind ditch

The crushed stone blind ditch is filled with coarse sand and gravel, and the crushed stone blind ditch is wrapped with a soft permeable pipe and a horizontal drainage pipe connected with the soft permeable pipe;

The second step, the construction of anti-seepage layer

After building the first layer of cement-stabilized gravel base, pave the anti-seepage composite geomembrane, coat a layer of asphalt on the anti-seepage composite geomembrane, and then cover it with cement mortar;

The third step is to complete the construction of the energy dissipation layer

After paving the motorway and non-motorized lanes, lay fine stone concrete, install curb stones on the fine stone concrete, and lay pebble energy dissipation pools inside the curb stones;

The fourth step is to complete the construction of the sunken green belt

The lowest point of the sunken green belt is lower than the edge of the road surface of the motorway, and an overflow rainwater outlet is set at the lowest point; sand sinking wells are set on the side of the sunken green belt near the motorway.

The invention responds to the concept of "sponge city", combines the urban road drainage system with the concave green space system, and "infiltrates", "stores" and "drains" rainwater, and is an ecological rainwater infiltration and storage facility. Its main advantages are as follows: firstly, the pebble energy dissipation pool can reduce the erosion of rainwater on the road, reduce road surface runoff, reduce flood peak flow, and alleviate the flood detention disaster caused by heavy rain on the road; Purify, reduce road dust, reduce road pollution; the third is to save green irrigation water, save precipitation and road runoff, replenish soil water resources and groundwater resources, and combine overflow rainwater outlets in green belts 1. The drainage pipeline facilities (horizontal drainage pipe, soft permeable pipe) of gravel blind ditch. When the surface runoff is large and the storage capacity of the green belt is insufficient, the rainwater can pass through the overflow rainwater that is higher than the elevation of the green belt and lower than the elevation of the road surface. The drainage pipe facilities of gravel blind ditch can also discharge excess water in the sunken green belt; the function of "storage" and "drainage" of rainwater is realized, and the prevention of waterlogging, utilization of water resources, The multiple benefits of landscaping.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is the structural representation of the sunken green space system based on the sponge city of the present invention;

Fig. 2 is a top view structure schematic diagram of a concave green space;

Among them: 1. Pebble energy dissipation pool, 2. Recessed green space, 3. Overflow rainwater outlet, 4. Sand sinking well, 5. Horizontal drainage pipe, 6, Soft permeable pipe, 7. Coarse sand cushion, 8. Gravel layer, 9. Anti-seepage layer, 10. Fine stone concrete, 11. Motor vehicle lane, 12. Non-motor vehicle lane, 13. Curb stone.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Referring to Fig. 1 and Fig. 2, a sunken green space system based on sponge city is placed between motor vehicle lane 11 and non-motor vehicle lane 12, including energy dissipation layer, sunken green belt 2, anti-seepage layer 9, crushed Stone Blind Ditch. There are two energy-dissipating layers, which are respectively placed on the edge of motor vehicle lane 11 and non-motor vehicle lane 12, including curb stone 13, a pebble energy dissipation pool 1 with a width of 0.2-0.3m, and fine stone concrete 10; There are water inlets with a distance of 40m; the pebble energy dissipation pool 1 is placed inside the roadside curb 13, and the roadside curb 13 and the pebble energy dissipation pool 1 are placed on the fine stone concrete 10. The sunken green belt 2 is placed between two energy-dissipating layers and is arc-shaped, and its lowest point is 0.1-0.3m lower than the road surface edge of the motorway 11. In a preferred embodiment, the sunken green belt 2 The lowest point is 0.2m lower than the edge of the road surface of the motorway 11; at the lowest point of the sunken green belt 2, there are multiple overflow stormwater outlets 3 connected to the underground drainage system, and the distance between adjacent overflow rainwater outlets 3 is 4m The overflow rainwater outlet 3 is higher than the lowest point of the sunken green belt 2 and lower than the road surface (motor vehicle lane and non-motor vehicle lane) elevation, so as to discharge rainwater; on the sunken green belt 2, it is close to the motor lane 11- The side is also provided with sinking wells 4, and the elevation of the tops of the sinking wells 4 is 0.1m lower than the edge of the motorway 11 for filtering and purifying rainwater. The anti-seepage layer 9 is placed below the concave green belt 2 and is in a concave shape, including cement mortar, asphalt, and anti-seepage composite geomembrane arranged sequentially from top to bottom, and the cement mortar is M5 cement mortar with a thickness of 2 cm. The gravel blind ditch is placed at the lowest point of the anti-seepage layer and directly below the overflow rainwater outlet 3; Lateral drains 5 and with Horizontal drain pipe 5 connected to Soft permeable pipe 6; the gravel blind ditch is filled with a 5cm-thick coarse sand cushion layer 7 and a 30cm-thick gravel layer 8 sequentially from top to bottom.

The construction method of the above-mentioned concave green space system based on the sponge city includes the following steps:

The first step is to complete the construction of the gravel blind ditch

The gravel blind ditch is filled with anti-seepage geomembrane full of coarse sand (5cm thick) and 30cm thick gravel, and the gravel blind ditch is also wrapped with flexible permeable pipe, the Flexible permeable pipe and Horizontal drainage pipe 5 is connected;

The second step, the construction of anti-seepage layer

After building the first layer of cement-stabilized gravel base, spread the anti-seepage composite geomembrane, coat a layer of asphalt on the anti-seepage composite geomembrane, and then cover with 2cmM5 cement mortar;

The third step is to complete the construction of the energy dissipation layer

After paving the motorway and non-motorized lanes, pave fine stone concrete, install roadside curbstones on the finestone concrete, and lay pebble energy dissipation pools inside the roadside curbstones. The energy dissipation pools are used to reduce the energy of rainwater itself. Avoid the strong erosion of the soil caused by the high flow rate of rainwater;

The fourth step is to complete the construction of the sunken green belt

The lowest point of the sunken green belt is 0.1-0.3m lower than the edge of the road surface of the motorway, and the lowest point is set in the middle of the green belt or other positions according to the needs, and the overflow rainwater outlet with a distance of 4m is set at the lowest point to collect rainwater ; Set up sand sinks on the side of the concave green belt near the motorway to purify rainwater.

In the present invention, the road surface and surrounding rainwater is discharged into the green belt, and then filtered and purified by the green belt. When the storage capacity of the green belt is insufficient, the rainwater enters the underground drainage system through the overflow rainwater outlet, and the collected rainwater can be used for maintenance of the green belt and maintenance of the green belt. Road clearing. The invention has the advantages of storing and infiltrating rainwater, reducing flood peak flow, reducing surface runoff and pollution, and the like.

Water balance analysis of sunken green space:

The sunken green space treats part of the rainwater in the catchment area through infiltration, evaporation, storage, etc., and the rainwater that exceeds the green space's infiltration and storage capacity is discharged into the nearby rainwater pipe. The following water balance relationship exists in the calculation period:

P ₀ +U ₀ ＝D+E+S+U ₁ +Q (1)

In the formula: P ₀ —total rainfall, m ³ ; U ₀ —initial water storage, m ³ ; D—runoff loss, m ³ ; E—evapotranspiration, m ³ ; S—infiltration amount, m ³ ; U ₁ —the water storage capacity of the green space at the end, m ³ ; Q—the overflow discharge, m ³ .

Calculation of concave green rainwater seepage storage capacity:

The rainwater infiltration rate of the sunken green space is the percentage of the infiltration and accumulation of rainwater in the green space to the total rainwater runoff entering the green space during the rainfall process, expressed in N. It can be calculated by formula (2), because the evaporation amount E in the time period is small, so it is not considered in the calculation; through the calculation of the rainwater runoff seepage storage rate, it can reflect the rainwater seepage storage capacity of the sunken green space;

In the formula: P _z —rainfall, mm; F ₁ —area of green space service area (i.e. catchment area), m ² ; F ₂ —concave green area, m ² ; C _n —runoff coefficient of green space service area .

Infiltration amount S calculation formula:

S＝60KJF ₂ T (3)

In the formula: K—Soil stable infiltration rate, m/s; J—Hydraulic slope, when vertical infiltration, J=1; T—Infiltration storage calculation period, min.

The formula for calculating the water storage capacity U ₁ of the sunken green space is:

U ₁ =F ₂ Δh (4)

In the formula, △h—the depth of the depression, that is, the height difference between the concave green space and the overflow port or the road surface, cm.

According to the local rainfall intensity q( _t ), the rainfall Pz per unit time can be obtained by integrating the rainfall intensity; the formula of rainfall intensity in Wuhan is:

In the formula: q(t)—design rainstorm intensity, mm/min; P—design rainstorm return period, a; t—rainfall duration, min, calculated as 60 minutes in Wuhan area.

According to the formulas (2), (3) and (4), when the greening rate reaches the maximum control volume, that is, when N=100%, the rainfall formula of the critical value can be deduced, such as (7), the required lowering of the green belt The sinking depth is as formula (8):

Example:

In order to quantitatively describe the infiltration and storage effect of the sunken green space on rainwater runoff, taking a certain closed area A as an example, the runoff coefficient C _n of the area except the green space is 0.9, assuming that the evaporation amount E and the initial water storage capacity of the sunken green space U ₀ are all zero. Taking the maximum and minimum values of the measured soil stable infiltration rate K in this area, that is, 5×10 ^-5 m/s and 3×10 ^-7 m/s as representatives, combined with the professional planning regulations of Wuhan's rainwater system, choose a Design return periods of rainstorms once in one year, three years and five years, that is, when the rainfall in 1 hour is 35.5mm, 49.6mm and 56.3mm respectively, according to formula (1) ~ formula (6), calculate the ratio of different green areas within 1 hour f(f=F ₁ /F ₂ ), the rainwater infiltration rate N of the green space under the conditions of the concave depth Δh, the calculation results are shown in the table, and the results show that when K=5×10 ^-5 m/s, f=25% , Δh ≥ 0.1m sunken green space, for the one-year, three-year and five-year design rainstorm return period, the rainfall lasting 1 hour can be infiltrated by the sunken green space; for K=3×10 ^-7 In the case of m/s, taking f=35%Δh=0.3m as an example, the once-a-year torrential rain can be infiltrated. For the three-year and five-year torrential rain, N can reach 94% and 81%.

It can be seen from the calculation example that:

With different design parameters, the rainwater seepage and storage capacity is also different. With appropriate engineering measures, it can become an important ecological measure for urban stormwater management. The function of the sunken green space is affected by many factors, among which the area ratio f of the sunken green space, the depth of the green depression △h, the stable infiltration rate of the green space soil K and the design rainstorm return period P are the factors that affect the rainwater infiltration of the sunken green space. An important factor affecting storage efficiency. It is very important to design and select appropriate parameters.

1. Vertical design

The vertical design of the sunken road green belt should consider factors such as terrain conditions, soil conditions, rainfall, green belt plot ratio, and plant selection types, and carry out reasonable design and layout. If the subsidence depth is too small, a large amount of rainwater will be discharged outside, which cannot play the role of regulating and storing rainwater. If the subsidence depth is too large, a large amount of rainwater will infiltrate and accumulate in the green belt. Therefore, in order to quantitatively describe the vertical design of the green belt, taking Wuhan as an example, under a certain rainstorm return period, assuming that N is 100%, according to formula (5) and formula (6), the different return periods of Wuhan can be calculated. When the values of T are 1, 3, 5, and 10a, the corresponding rainfall H in Wuhan is 48.47, 61.19, 67.11, and 75.13mm respectively. It can be seen that with the increase of the return period, the rainfall also increases with increased, but the increasing trend slowed down.

Choose the return period of 3 years, set the soil stable infiltration coefficient K as 1.5×10 ^-6 m/s, the pavement runoff coefficient as 0.9, the water conservancy slope J as vertical infiltration as 1, the time t as 60min, and the subsidence depth △h takes 10, 15, 20, 25, and 30 cm, and the required road greening rate f can be estimated to be 56.4%, 37.3%, 27.9%, 22.2%, and 18.5%, respectively.

It can be seen that when the sinking depth of the road green belt is 10-30cm, it can meet the demand for rainwater infiltration and storage, and the design is less than 20cm can also absorb a certain amount of rainwater, and the remaining rainwater can enter the storage device through the overflow port, or it can Drain into storm sewers. The urban terrain of Wuhan is relatively flat, and the slope of the road design is relatively small. It is more suitable for the design of the sunken road green belt. It is better to design the road at a higher terrain, which is conducive to the flow of rainwater to the lower terrain of the sunken green belt and surrounding areas. green space. In order to reduce surface runoff, ecological pavement treatment is adopted on sidewalks and non-motorized vehicle lanes, and the connection between sunken green belts, road surfaces and overflow stormwater outlets needs to be reasonably designed. First of all, the design height of the curb side stone should not be higher than the road surface, and it should be as flush with the road surface as possible. If it needs to be higher than the road surface, a gap should be designed to ensure that the rainwater flows into the sunken green space; Pebbles with a width of 30cm prevent the soil of the green belt from being scoured. The soil layer is laid from bottom to top with gravel, sand, soil, and mulch, which is more conducive to the infiltration of rainwater; finally, the elevation of the rainwater overflow should be lower than the road surface , can be designed in the middle or both sides of the green belt, and anti-clogging treatment must be done.

2. Area ratio of concave green space f

The percentage of the sunken green belt in the total area has a particularly obvious impact on the drainage rate of rainwater. According to the formula (8), the stable soil infiltration coefficient K is set to 1.5×10 ^-6 m/s, and the runoff coefficient of the pavement is 0.9. The water conservancy slope J is set to be 1 for vertical infiltration, the time t is set to be 60 minutes, and the variable green belt ratio f is set to be 10%, 20%, 30%, 40%, and 50%, respectively, to obtain road greening under different rainstorm recurrence periods The sinking depth h of the belt.

With the increase of the greening rate, the required sinking depth decreases, and the decrease in the front is larger than that in the back, and the sinking depth decreases less when f reaches more than 30%. When the road greening rate is lower than 20%, the required sinking depth exceeds the critical value of the sinking green belt design, which may not be conducive to the growth of plants. The greening rate that most meets the road greening rate standard in Wuhan and can also meet the functional requirements of the sunken green belt is about 30%. When f is 35%, the subsidence depths that meet the rainstorm return periods 1, 3, 5, and 10a are 14.7, 18.6, 20.4, and 22.9 cm, respectively, which meet the standard design of subsidence depth, and the infiltration and storage effect is obvious. In most areas of Wuhan, the road greening rate is generally higher than 20%, and in many areas it reaches 30%, but it is basically an elevated green space, which cannot infiltrate rainwater on the road surface. The design only needs to transform the existing green space into a sunken green belt 80% of the rainwater on most roads can be retained.

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present invention.

Claims (7)

1. a kind of concave herbaceous field system based on sponge city, is placed between car lane, bicycle lane, and its feature exists In：Including energy dissipating layer, up concave type greenbelt, impervious barrier, rubble french drain；

The energy dissipating layer has two, is respectively placed in car lane and bicycle lane edge, including trackside kerb, cobble energy dissipating Pond, pea gravel concreten, cobble energy dissipation tank are placed in trackside kerb inner side, and trackside kerb, cobble energy dissipation tank are placed in pea gravel concreten On；

The up concave type greenbelt is placed between two energy dissipating layers, and overflowing rain water is provided with the minimum point of up concave type greenbelt Mouthful；Sand sediment trap is additionally provided with up concave type greenbelt, the sand sediment trap is near car lane side；

The antiseepage is placed on up concave type greenbelt lower section, in concave, including cement mortar, the drip for setting gradually from top to bottom Blue or green, antiseepage composite geo-membrane；

The rubble french drain is placed in the lowest part of impervious barrier, and transverse drain and and transverse drain are provided with the rubble french drain The flexible porous tube of connection；It has been sequentially filled coarse sand bed course, metalling from top to bottom in rubble french drain.

2. the concave herbaceous field system based on sponge city according to claim 1, it is characterised in that：On trackside kerb Multiple water inlets are provided with, the spacing of adjacent water inlet is 40m.

3. the concave herbaceous field system based on sponge city according to claim 1, it is characterised in that：Up concave type greenbelt It is curved, its minimum point 0.1-0.3m lower than the pavement edge of car lane.

4. the concave herbaceous field system based on sponge city according to claim 1 or 3, it is characterised in that：The cobble The width of energy dissipation tank is 0.2-0.3m.

5. the concave herbaceous field system based on sponge city according to claim 4, it is characterised in that：Sand sediment trap top mark is high Less than the pavement edge 0.1m of car lane；Overflowing rain water mouth has multiple, and the spacing of adjacent overflowing rain water mouthful is 4m.

6. a kind of construction method of the concave herbaceous field system based on sponge city, it is characterised in that comprise the following steps：

The first step, complete rubble french drain and build

Parcel flexible porous tube and the horizontal stroke being connected with flexible porous tube in coarse sand and rubble, rubble french drain are filled with rubble french drain To drainpipe；

Second step, impervious barrier are built

After building ground floor cement stabilized macadam base, paved antiseepage composite geo-membrane, and one layer is applied on antiseepage composite geo-membrane Pitch, then cover cement mortar；

3rd step, complete energy dissipating layer build

Pea gravel concreten is laid after the pavement spread for completing car lane and bicycle lane, trackside is installed on pea gravel concreten Kerb, cobble energy dissipation tank is laid in the inner side of trackside kerb；

4th step, complete up concave type greenbelt and build

The minimum point of up concave type greenbelt is lower than the pavement edge of car lane, and sets overflowing rain water mouthful in minimum point；Under Sand sediment trap is set near car lane side in female greenbelt.

7. construction method according to claim 6, it is characterised in that：The minimum point of up concave type greenbelt is than car lane The low 0.1-0.3m of pavement edge.