Design method of permeable pavement based on hydrological principles

Abstract

The present invention discloses a design method for a permeable pavement based on hydrological principles. Based on the basic principle of the balance between the inflow and outflow of water, a design method based on hydrological principles is formulated for permeable pavements, which can be used to determine pavement parameters that meet hydrological conditions, such as pavement thickness and material porosity, etc., so that the designed pavement can meet the safety requirements under specific rainstorm conditions while meeting the requirements of structural design. The present invention solves the problem that the design methods of permeable pavement systems generally focus on meeting the requirements of structural strength design and have a single consideration factor for permeability design.

Description

Technical Field

[0001] The invention relates to the technical field of permeable pavement, and in particular to a design method for a permeable paved road based on hydrological principles. Background Art

[0002] Permeable pavement can effectively reduce road surface water accumulation caused by rainfall, improve skid resistance, and reduce noise. At the same time, setting a water storage base in the pavement structure can not only alleviate the drainage pressure caused by sudden rainstorms, but also introduce water into reservoirs and wetlands through drainage facilities for collection and utilization, or let it slowly return to the groundwater system, which is in line with the construction concept of "sponge city".

[0003] At present, the design method of domestic permeable pavement system is generally based on satisfying the structural strength design, and the permeability design simply considers whether the permeability of the material can meet the local rainfall. Summary of the invention

[0004] In order to overcome the defects of the prior art, a design method for permeable paved road surface based on hydrological principles is provided to solve the problem that the design method of permeable paved road surface system is generally mainly based on structural strength design, and there is a single design consideration factor for permeability.

[0005] To achieve the above purpose, a design method for permeable paved road surface based on hydrological principles is provided, comprising the following steps:

[0006] a. Preliminarily determine the structure and size of the pavement structure and the drainage method of the water flow in the pavement structure, which includes direct drainage through the roadbed below the pavement structure and indirect drainage through drainage pipes matched with the pavement structure;

[0007] b. Obtaining first geometric parameters of the pavement structure and second geometric parameters of the drainage pipe, wherein the first geometric parameters include the material type, area and thickness of each layer of the pavement structure, and the second geometric parameters include the radius and slope of the drainage pipe, and the longest horizontal distance traveled by water in the pavement structure to the drainage pipe;

[0008] c. Obtaining a first hydrological parameter of the pavement structure and a second hydrological parameter of the drainage pipe, wherein the first hydrological parameter includes a water permeability coefficient and a porosity of each layer of the pavement structure, and the second hydrological parameter includes a Manning coefficient;

[0009] d. Obtaining rainfall parameters at the location of the paved road structure, wherein the rainfall parameters include continuous 24-hour rainfall;

[0010] e. Calculate the real-time inflow value of the water flow in the paved road surface structure based on the inflow formula, and the inflow formula is where Q 入 is the real-time inflow value, P is the rainfall, S is the total water storage thickness of the paved road surface structure, and I a is the initial loss of precipitation;

[0011] f. Calculate the real-time outflow value of the water flow flowing out of the paved road surface structure separately according to different discharge methods. When the discharge method is the direct discharge type, calculate the real-time outflow value based on the first outflow formula, and the first outflow formula is

[0012] where v 出 is the real-time outflow value, k 路基 is the permeability coefficient of the subgrade material, h is the depth of water in the paved road surface structure, H is the total thickness of the paved road surface structure, and a is the subgrade infiltration reduction factor. When the discharge method is the indirect discharge type, first calculate the first moving rate of the water flow towards the drainage pipe and the second moving rate of the water flow in the drainage pipe, and take the smaller of them as the real-time outflow value;

[0013] g. Calculate the real-time water storage volume in the paved road surface structure based on the hydrological design formula, the real-time inflow value, and the real-time outflow value. The hydrological design formula is

[0014] where t is any time point. When the real-time water storage volume is less than the design limit value, then determine the structure, size, and discharge method of the initially determined paved road surface structure as the final design scheme. When the real-time water storage volume is greater than the design limit value, proceed to the next step;

[0015] h. Adjust the thickness and porosity of each layer of the initially determined paved road surface structure, and repeat steps b - g until the final design scheme is determined.

[0016] Further, when calculating the real-time inflow value, when the total number of layers of the paved road surface structure is n, the total water storage thickness where H i is the thickness of the i-th layer,

[0017] V di is the porosity of the i-th layer.

[0018] Further, the calculation formula for the first moving rate:

[0019]

[0020] where v 面层 / 基层k is the flow rate of water through the surface layer / base layer to the drainage pipe, 面层 / 基层 is the water permeability coefficient of the surface or base material, h is the height of the water level above the drainage pipe, b is the longest horizontal distance that water in the pavement structure travels to a drainage pipe, and L is the paved area / b.

[0021] Furthermore, the calculation formula of the second moving speed is:

[0022]

[0023] Among them, v 排水 is the maximum flow rate of water through the drainage pipe, n is the Manning coefficient, r is the radius of the drainage pipe, and S is the slope of the drainage pipe.

[0024] The beneficial effect of the present invention is that the design method of the permeable paved road surface based on the hydrological principle of the present invention takes the inflow and outflow balance of water flow as the basic principle, and formulates a design method based on the hydrological principle for permeable pavement, which can be used to determine the pavement parameters that meet the hydrological conditions, such as pavement thickness and material porosity, so that the designed pavement can meet the safety of use under specific rainstorm conditions while meeting the structural design requirements. The present invention is applicable to various pavement structure types, materials, drainage types and drainage facilities, and the relevant parameters required for calculation are easy to obtain, and the calculation process is relatively convenient. DETAILED DESCRIPTION

[0025] The present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention.

[0026] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below in conjunction with the embodiments.

[0027] The present invention provides a design method for a permeable paved road surface based on hydrological principles, comprising the following steps:

[0028] a. Preliminarily determine the structure and size of the pavement structure and the drainage method of water in the pavement structure. The drainage methods include direct drainage through the roadbed below the pavement structure and indirect drainage through the drainage pipes matched with the pavement structure.

[0029] The design method of the permeable paved road based on the hydrological principle of the present invention is based on the principle of water inflow and outflow balance, and determines the thickness and porosity of the paved road structure that meets the hydrological requirements according to rainfall characteristics, material drainage characteristics, etc. The water inflow mainly comes from rainfall.

[0030] The paved road surface structure includes a surface layer and a base layer. According to different structural design requirements, the surface layer can also be divided into 2 to 3 layers. Since the materials used in each layer are different, separate calculations are required.

[0031] b. Obtain the first geometric parameters of the paved road surface structure and the second geometric parameters of the drainage pipe. The first geometric parameters include the material types, areas, and thicknesses of the layers of the paved road surface structure. The second geometric parameters include the radius, slope, and the longest horizontal distance of the water in the paved road surface structure traveling to the drainage pipe.

[0032] c. Obtain the first hydrological parameters of the paved road surface structure and the second hydrological parameters of the drainage pipe. The first hydrological parameters include the permeability coefficients and porosities of the layers of the paved road surface structure. The second hydrological parameters include the Manning coefficient.

[0033] d. Obtain the rainfall parameters at the location of the paved road surface structure. The rainfall parameters include the rainfall amount for 24 consecutive hours.

[0034] e. Calculate the real-time inflow value of the water flow in the paved road surface structure based on the inflow formula.

[0035] The inflow formula is

[0036] where, Q 入 is the real-time inflow value (unit: mm). P is the rainfall amount (unit: mm), that is, the rainfall amount for 24 consecutive hours. S is the total water storage thickness of the paved road surface structure (unit: mm), and I a is the initial loss of precipitation. Calculated according to I a = λS, where λ is the initial loss coefficient. When the initial loss of precipitation > the rainfall amount, the inflow = 0.

[0037] When calculating the real-time inflow value, when the total number of layers of the paved road surface structure is n, the total water storage thickness where, H i is the thickness of the i-th layer. V di is the porosity of the i-th layer.

[0038] f. Calculate the real-time outflow value of the water flow flowing out in the paved road surface structure according to different discharge methods. When the discharge method is the direct discharge type, calculate the real-time outflow value based on the first outflow formula. The first outflow formula is

[0039] where, v 出 is the real-time outflow value (unit: mm / d). k 路基is the permeability coefficient of the subgrade material (unit: mm / d). h is the depth of water in the pavement structure (unit: mm). H is the total thickness of the pavement structure (unit: mm). a is the subgrade infiltration reduction factor. Considering less than the saturation state and potential clogging, the subgrade infiltration reduction factor is generally taken as 0.5.

[0040] When the drainage method is the indirect drainage method, first calculate the first moving rate of the water flowing towards the drainage pipe and the second moving rate of the water in the drainage pipe, and take the smaller of them as the real-time outflow value.

[0041] Specifically, the calculation formula for the first moving rate:

[0042]

[0043] where, v 面层 / 基层 is the flow velocity of water through the surface layer / subgrade towards the drainage pipe (unit: m 3 / d). k 面层 / 基层 is the permeability coefficient of the surface layer or subgrade material (unit: m / d). h is the height of the water level above the drainage pipe (unit: m). b is the longest horizontal distance for the water in the pavement structure to reach a drainage pipe (unit: m). L is the paving area / b (unit: m).

[0044] The calculation formula for the second moving rate:

[0045]

[0046] where, v 排水 is the maximum flow velocity of water through the drainage pipe (unit: m 3 / d). n is the Manning coefficient, a coefficient reflecting the influence of the roughness of the pipe wall on the water flow. r is the radius of the drainage pipe. S is the slope of the drainage pipe.

[0047] g. Based on the hydrological design formula, the real-time inflow value, and the real-time outflow value, calculate the real-time water storage in the pavement structure. The hydrological design formula is:

[0048]

[0049] where, t is any time point. When the real-time water storage is less than the design limit value, then determine the structure, size, and drainage method of the initially determined pavement structure as the final design scheme. When the real-time water storage is greater than the design limit value, enter the next step.

[0050] h. Adjust the thickness and porosity of each layer of the initially determined pavement structure, and repeat steps b - g until the final design scheme is determined.

[0051] The design method of the permeable pavement based on the hydrological principle of the present invention takes the balance of water inflow and outflow as the basic principle, formulates a design method based on the hydrological principle for the permeable pavement, and can be used to determine the pavement parameters that meet the hydrological conditions, such as the pavement thickness and material porosity, etc., so that the designed pavement can meet the safety requirements under specific rainstorm conditions while meeting the structural design requirements. The present invention is applicable to various different pavement structure types, materials, drainage types and drainage facilities, and the relevant parameters required for calculation are easy to obtain, and the calculation process is relatively convenient.

[0052] In order to further illustrate the design method of the permeable pavement based on the hydrological principle of the present invention, the following specific embodiments are used for illustration.

[0053] The First Embodiment

[0054] Design a permeable pavement structure one, the surface layer of which is composed of 2 layers of permeable asphalt and permeable concrete, and the base layer is graded crushed stone. The porosity of each layer of material and the thickness determined by structural calculation are shown in Table 1 below.

[0055] The permeability coefficient k of the subgrade material 路基 = 2.4 m / d, and the initial loss coefficient λ is 0.2. Now, through the method of the present invention, it is verified whether the designed permeable pavement structure one can meet the hydrological design requirements under the heavy rainstorm condition with an initial water level of 0 mm and a total rainfall of 228 mm in 24 consecutive hours.

[0056] Table 1. Parameters of each layer of the pavement structure in the first embodiment

[0057] Layer Type Porosity Proposed Thickness (mm) Upper Layer Permeable Asphalt 0.17 50 Lower Layer Permeable Concrete 0.2 80 Base Course Graded Crushed Stone 0.26 130

[0058] It can be known from the calculation that the total thickness of this structure is 260 mm, and the total water storage thickness S is 58.3 mm. For the sake of simplifying the calculation, assuming that the rainfall rate is constant in each period, the inflow, outflow and water level conditions in the pavement per hour within 24 hours can be obtained, as shown in Table 2.

[0059] Table 2. Water flow and water level conditions of the pavement structure in the first embodiment under rainstorm conditions (24 h, 228 mm)

[0060]

[0061] Continued Table 2. Water flow and water level conditions of the pavement structure in the first embodiment under rainstorm conditions (24 h, 228 mm)

[0062]

[0063] Considering the design margin and the situation of pore blockage during the long-term use of the pavement, the design limit is set at 85% of the pavement thickness, that is, 260 mm × 0.85 = 221 mm. Through calculation, it can be seen that at the 23rd hour, the water level in the pavement has exceeded the design limit, indicating that the pavement structure does not meet the design requirements proposed by the present invention.

[0064] To meet the requirements, the thickness of the surface layer and the base layer can be appropriately increased, or the porosity of the material can be increased. For example, adjusting the base layer thickness to 150 mm, or adjusting the porosity of the base layer material to 0.29, can meet the design requirements proposed by the present invention through calculation. For the adjusted structure, it is necessary to further verify whether it meets the structural performance requirements and elevation requirements. If both are met, the design can be accepted.

[0065] Second Embodiment

[0066] Design the second permeable pavement structure with a width of 20 m. The surface layer of the structure is composed of 2 layers of different permeable asphalt. The porosity of each layer of material and the thickness determined through structural calculation are shown in Table 3 below.

[0067] The base layer of the second designed permeable pavement structure is an impermeable layer, and drainage is carried out by setting PVC pipes (drainage pipes). The pipes are located on both sides of the road, between the surface layer and the base layer. The Manning coefficient of the pipe material is 0.012, the radius is 5 mm, and the pipe slope is 1%. The permeability coefficient k of the bottom layer material 路基 = 371.52 m / d, and the initial loss coefficient λ is 0.2.

[0068] Now, through the method of the present invention, it is verified whether the second designed permeable pavement structure can meet the hydrological design requirements under the rainfall condition of an initial water level of 0 mm and a total rainfall of 80 mm in 20 consecutive hours.

[0069] Table 3. Parameters of each layer of the pavement structure in the second embodiment

[0070] Layer Type Porosity Proposed Thickness (mm) Upper Layer Permeable Asphalt I 0.22 90 Lower Layer Permeable Asphalt II 0.26 100

[0071] It can be seen from the calculation that the total thickness of the surface layer structure is 190 mm, the total water storage thickness S is 45.8 mm, and the maximum water flow velocity through the drainage pipe is 0.1119 m 3 / d. To simplify the calculation, assuming that the rainfall rate is constant in each period, the inflow, outflow and water level conditions in the pavement per hour within 20 hours can be obtained as shown in Table 4 below.

[0072] Table 4. Water flow and water level conditions of the pavement structure in the second embodiment under rain conditions (20 h, 80 mm)

[0073]

[0074] Continued Table 4. Water level situation of the paving structure in the second embodiment under rainy conditions (20h, 80mm)

[0075]

[0076] Considering the design margin and the situation of pore blockage in the long-term use of the paving, the design limit is set at 85% of the paving thickness, that is, 190mm×0.85 = 161.5mm. Through calculation, it can be seen that at the 19th hour, the water level in the paving has exceeded the design limit, indicating that this paving structure does not meet the design requirements proposed by the present invention.

[0077] To meet the requirements, the thickness of the surface layer and the base layer can be appropriately increased, or the porosity of the material can be increased. For example, adjusting the thickness of the lower surface layer to 110mm, or adjusting the porosity of the lower surface layer material to 0.28, can meet the design requirements proposed by the present invention through calculation. For the adjusted structure, it is necessary to further verify whether it meets the structural performance requirements and elevation requirements. If both are met, the design can be accepted.

[0078] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but also covers other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A design method for a permeable pavement based on hydrological principles, characterized in that The following steps are involved: a. Preliminarily determine the structure and size of the pavement structure and the drainage method of the water flow in the pavement structure, which includes direct drainage through the roadbed below the pavement structure and indirect drainage through drainage pipes matched with the pavement structure; b. Obtaining first geometric parameters of the pavement structure and second geometric parameters of the drainage pipe, wherein the first geometric parameters include the material type, area and thickness of each layer of the pavement structure, and the second geometric parameters include the radius and slope of the drainage pipe, and the longest horizontal distance traveled by water in the pavement structure to the drainage pipe; c. Obtaining a first hydrological parameter of the pavement structure and a second hydrological parameter of the drainage pipe, wherein the first hydrological parameter includes a water permeability coefficient and a porosity of each layer of the pavement structure, and the second hydrological parameter includes a Manning coefficient; d. Obtaining rainfall parameters at the location of the paved road structure, wherein the rainfall parameters include continuous 24-hour rainfall; e. Calculate the real-time inflow value of water flow in the paved road surface structure based on the inflow formula, and the inflow formula is where Q 入 is the real-time inflow value, P is the rainfall, S is the total water storage thickness of the paved road surface structure, and I a is the initial loss of precipitation; f. Calculate the real-time outflow value of the water flow flowing out in the pavement structure according to different discharge methods respectively. When the discharge method is the direct discharge method, calculate the real-time outflow value based on the first outflow formula, and the first outflow formula is Among them, v 出 is the real-time outflow value, k 路基 is the permeability coefficient of the subgrade material, h is the depth of water in the pavement structure, H is the total thickness of the pavement structure, a is the subgrade infiltration reduction factor. When the discharge method is the indirect discharge method, first calculate the first movement rate of the water flow towards the drainage pipe and the second movement rate of the water flow in the drainage pipe, and take the smaller value as the real-time outflow value; g. Calculate the real-time water storage volume in the paved road surface structure based on the hydrological design formula, the real-time inflow value, and the real-time outflow value. The hydrological design formula is the real-time water storage volume where t is any point in time. When the real-time water storage volume is less than the design limit value, the structure and dimensions of the preliminarily determined paved road surface structure and the drainage method are determined as the final design solution. When the real-time water storage volume is greater than the design limit value, proceed to the next step; h. Adjust and preliminarily determine the thickness and porosity of each layer of the pavement structure, and repeat steps b to g until the final design is determined.

2. The design method of the permeable pavement based on the hydrological principle according to claim 1, characterized in that When calculating the real-time inflow value, when the total number of layers of the paved road surface structure is n, the total water storage thickness wherein, H i is the thickness of the i-th layer, and V di is the porosity of the i-th layer.

3. The design method of the permeable pavement based on the principle of hydrology according to claim 1, characterized in that, The calculation formula of the first moving rate is: Among them, v 面层 / 基层 is the flow velocity of water from the surface layer / base layer to the drainage pipe, k 面层 / 基层 is the permeability coefficient of the surface layer or base layer material, h is the height of the water level above the drainage pipe, b is the longest horizontal distance for water in the pavement structure to reach a drainage pipe, and L is the paving area / b.

4. The design method of the permeable pavement based on the principle of hydrology according to claim 1, characterized in that, The calculation formula of the second moving rate is: Among them, v 排水 is the maximum flow velocity of water through the drainage pipe, n is the Manning coefficient, r is the radius of the drainage pipe, and S is the slope of the drainage pipe.

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