JPH01111902A - Method for planning storage type water pervious pavement - Google Patents

Abstract

PURPOSE: To determine the thickness of a water-permeable pavement which provides storage performance by calculating the thickness of the pavement from the amount of daily rainfall and the percentage of effective percentage of voids in a water-permeable pavement material for the pavement. CONSTITUTION: The thickness of a storage water-permeable pavement is designed in view of the amount of daily rainfall in an pavement area and the property of voids in a pavement material. The characteristic of voids is the percentage of voids which is measured by setting a Marshall specimen inserted in a mold. For the amount of daily rainfall on the other hand, an average value of the amount of daily rainfall in 80 areas across the country is found and a non-excessive probability is found from the amount of daily rainfall and a standard deviation value. The thickness of the pavement can thus be determined which exhibits efficient water permeable performance.

Description

[Detailed description of the invention] The present invention relates to a method for designing a storage type permeable pavement.

Conventionally, the design of permeable pavement has been carried out by considering two factors: traffic conditions and permeability function conditions. Permeability function conditions must be designed taking into account many conditions such as rainfall intensity, rainfall amount, permeability of the subgrade, and gaps in the pavement.

From this point of view, conventional designs have the following (1) and (2)
The formula is used.

tV= (0,1i -3600q)100t/8
0... Old... (1) i=b/(t+a)
... Song ... (2) Rainfall intensity formula Talpot formula where H: Pavement thickness (Kui), V: Average porosity of pavement (%)
), i; rainfall intensity (mu/h), q: average penetration rate of subgrade (am/5ec), t: rainfall duration (man
), b and a are constants that vary depending on the target area.

Conventionally known design methods derive the rainfall amount (r) from the rainfall intensity (i) and rainfall duration (1), and calculate the drainage amount from the average permeation rate of the subgrade (hereinafter referred to as drainage rate) determined on site. Calculate the pavement g (H) from the water storage capacity of the pavement body (■・V) given as the difference between rainfall amount and drainage amount.
has been decided.

However, rainfall intensity (i) must be converted from constants a and b set at values considered appropriate for the target area and rainfall duration (1), but data on rainfall duration is not available nationwide. There is no unified standard (because there is so little data, it is practically impossible to collect it, and the rainfall intensity formula (2) indicates that the rainfall duration (1) is 12
If it exceeds 0 minutes, the applicability of the formula is poor and there is a limit to its applicability. or,? glrgI is the drainage rate (q
) and the amount of water stored (■・■).
According to this, the greater the rainfall intensity (i), the greater the water storage capacity (H・
V) becomes smaller, which is contrary to common sense. This is because the rainfall intensity (i) cannot be an appropriate parameter for determining the amount of water stored (U-V).

Furthermore, since the rainfall intensity (i) changes over time even during a single rainfall, it is not appropriate to use this as a representative data of rainfall characteristics when designing. Furthermore, although the drainage speed varies depending on the properties of the subgrade soil, the permeability coefficient after leveling and compaction of the subgrade surface is at most 10-' (
em/5ee), which is not within the range where the drainage speed affects the amount of water stored, and because conventional permeable pavement is a storage type, there is no need to consider the drainage speed, and the design It does not have a big impact on the above. As described above, conventional design methods are detailed but extremely complicated, requiring labor and time, and moreover, it can be said that data collection is impractically difficult.

The present invention aims to improve these points and provide a design method for permeable pavement that is simple and allows data necessary for design to be easily collected nationwide.

That is, the present invention is characterized in that, in designing a water-permeable retention pavement, the pavement thickness is determined based on the porosity characteristics, preferably the effective porosity, of the eyestrain and pavement constituent materials.

It will be explained that the sewage inventive method is a simple and rational design method, and specific embodiments of the inventive method will be explained.

There are many purposes for permeable pavement, such as providing drainage facilities as a supplement to sewer systems, replenishing groundwater, ensuring safe and comfortable driving for vehicles, and comfortable walking for pedestrians. From a functional standpoint, it can be said that emphasis should be placed on improving the safety and comfort of driving and walking. This objective cannot be achieved unless all rainfall is treated. The accident rate in rainy weather is higher when the driver does not feel the danger and the driving speed is high, or when it starts to rain or when it rains normally, rather than when the driver feels dangerous and there is heavy rain or very heavy rainfall. It is said that In addition, it can be similarly inferred that pedestrian discomfort arises not from heavy rain, but from the difficulty of walking due to water splashes from running vehicles and puddles in normal rain. In other words, the above objective can be fully achieved if it can handle even normal rain. Here, the term "normal rain" refers to cases in which the amount of rainfall is exceptionally large as described above (t), and according to the inventor's study, this corresponds to approximately 70% of all rainfall.

The method of the present invention is aimed at this normal rain.

FIG. 2 shows a typical example of the design method of the present invention in the form of a flowchart, and the following explanation will be given along this flowchart.

Regarding the setting of the characteristics of rainfall that should be targeted, rainfall has three characteristics: rainfall intensity, rainfall amount, and rainfall duration, and considering the generality of the data and the ease of collecting it nationwide, rainfall quantity is most appropriate. Rainfall data includes 10-minute rainfall, 60-minute rain, eyesore rainfall, annual rainfall, etc., but when setting the rainfall amount of normal rain that should be targeted,
Since there is no problem even if the rain continues for about 24 hours at most, the eyesore rain amount is appropriate.

Furthermore, since the amount of obstructive rainfall is the most basic rainfall characteristic, it can be easily obtained when collecting it. The amount of normal rain can be estimated by statistically processing this eyesore rainfall. It is known that the frequency distribution curve of data such as eyesore rainfall is an exponential curve, and the ratio of rainfall up to a certain eyesore rainfall to the total rainfall can be calculated by calculating the non-exceeding probability for exponentially distributed data. Seek. This probability of non-exceeding is calculated by the mean value (mw) and standard deviation (δ
8) can be easily calculated using equation (3).

As an example, Figure 3 shows the relationship between eyesight rainfall and its non-exceeding probability based on equation (3), obtained by calculating the average value of blinding rainfall at 80 locations nationwide in the Science Chronology.

logs 10 F(”) =”e”P (2, go2as, (X
m, X I,)) ”””fl) Here F (X)
: non-exceedance probability, ξ: standard deviation of the data, m: mean value of the data.

In determining how much normal rain causes an eyesore, the inventor has determined that even if normal rain accounts for 70% of the total rainfall, there is no problem with the Wii design, and that 70% of the total rainfall is If it is possible to process this percentage, the objective will be achieved. Therefore, in the example of FIG. 3, the amount of obstructive rainfall up to 181 II m is determined to be normal rain, and the design rainfall amount is 18 m.

It is desirable to use the effective porosity as the porosity characteristic of the material, which is another factor in determining the pavement thickness in the method of the present invention.

Voids in materials have traditionally been considered to be an important factor that influences water storage capacity and hydraulic conductivity, but there are two types of pores: effective pores with continuity that are effective for water storage capacity and hydraulic conductivity, and independent pores. exist. This can be easily understood from the fact that even in dense-grained ascon, which is said to be impermeable to water, there are about 3 to 6% voids. However, in conventional designs, the total porosity including independent voids is exclusively used, and there are no known examples of using effective voids.

The present inventor discovered an effective and appropriate calculation method for effective porosity,
As a result, we succeeded in making a design based on the aforementioned eyesore rainfall and effective porosity.

FIG. 4 shows an example of an apparatus effective for measuring and calculating effective porosity used in the method of the present invention.

In Figure 4, Marshall specimen 2 created in mold 1
Collar members capable of engaging with the upper and lower ends of the mold 3.
．． 4 is set.

(&) shows the set state, and (b) shows its exploded sectional view.

The lower collar member 4 has a bottom, and the upper collar member 3 is open and has a base line 5 at an appropriate position.

The collar member is preferably made of transparent resin such as acrylic resin. The mold 1 and the collar members 3 and 4 are closely engaged by an O-ring 6 and a spring 7. After setting as shown in FIG. 4(a), water is poured from the top and allowed to naturally permeate the specimen, allowing the water to reach the base @S of the upper collar member. In this state, all the effective voids inside the material are filled with water. The volume of the effective void is obtained by subtracting the volume of the collar portion measured in advance from the total volume of the water required for this and the water in the collar portion. The effective porosity is determined by dividing the volume of effective voids by the volume of the specimen. When this is expressed as a calculation formula, it becomes formula (4).

Vi-(Vw-Ve)/((WL-W2)/r, +(V
w-Me)) --(4) where vi: effective porosity c%), Vws total volume of permeated water and water in the collar part (c, r), Ve+ volume of the collar part (all)
, Wi: weight of the specimen in air (g), W2: weight of the specimen in water (g), r, , density of water (g/cd).

With this method, the effective voids can be easily calculated, and the amount of water stored in the permeable pavement can be determined simply and accurately.

In particular, the above method can be said to be the closest measurement method to the actual site since it is carried out in low water conditions and by natural infiltration of water only from the upper surface. Therefore, there is no need to consider errors caused by infiltration from the sides, water pressure, etc., and the amount of voids that can actually be filled can be determined accurately and quickly.

Note that the pavement thickness is expressed by equation (5) and does not take into account the drainage rate of the permeable pavement, but since the permeable pavement targeted by the present invention is a storage type, it is not necessary in practice and can be ignored. However, this does not cause any design problems. Therefore, the pavement thickness can be easily determined from the design rainfall jt (r) and the effective porosity (Vi).

H(m) = I Q Or (+em)/V i(
%) ・-・・-(5) In addition, the selection of paving materials and the setting of the composition can be carried out as appropriate according to conventional methods.

The present invention provides a design method for determining a pavement thickness that allows the essential functions of permeable pavement to be fully utilized in practical use, regardless of conditions such as the type of material used. There is no complexity or difficulty in obtaining data as with conventional design methods, and it is possible to easily design symmetrical areas.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between drainage speed and required water storage volume;
The figure is a flowchart showing a typical example of the method of the present invention, FIG. 3 is a diagram showing the relationship between the amount of obstructive rainfall and the non-exceeding probability, and FIG. 4 shows an effective porosity measuring device. Figure 1 Drainage 1111 Ccjn/5ec) Figure 3 Day rainfall (mm 7 days) 4th CQ) (b)

Claims (4)

[Claims] (1) A method for designing a water retention type permeable pavement, characterized in that, in designing the water retention type permeable pavement, pavement thickness is determined based on daily rainfall and pore characteristics of pavement constituent materials. (2) Claim 1 in which the porosity characteristic is effective porosity
The method described in section. (3) The method according to claim 1, wherein the pavement thickness is determined based on the following formula. H=100r/Vi where H is the pavement thickness (mm), r is the design rainfall amount (mm) calculated from the daily rainfall amount, and Vi is the effective porosity (%). (4) An effective porosity measurement device for the design of water-retentive pavement, which consists of collar members arranged above and below a specimen.