CN114965210A - Permeable asphalt pavement rainfall infiltration evaluation method based on indoor test and unsaturated hydraulic parameter inversion - Google Patents

Abstract

The invention discloses a permeable asphalt pavement rainfall infiltration evaluation method based on indoor tests and unsaturated hydraulic parameter inversion, which comprises the steps of building a permeable asphalt pavement rainfall infiltration indoor test platform; monitoring the rainfall infiltration process of the permeable asphalt mixture in real time; establishing a finite element model with the same size as an indoor experimental device through rainfall infiltration simulation software; inverting the unsaturated hydraulic parameters of the permeable asphalt mixture by combining the bottom outflow measured data; obtaining unsaturated hydraulic parameters to carry out simulation research on the rainfall infiltration process of the permeable asphalt pavement structure; and analyzing the influence of rainfall intensity on the outflow response of the permeable asphalt pavement structure. According to the method, the rainfall infiltration and stagnation effects of the permeable asphalt pavement cannot be accurately analyzed by considering the saturated seepage theory, and the unsaturated hydraulic parameters are obtained through tests and are relatively complex, so that the initial data obtained through indoor tests are subjected to the inversion of the unsaturated hydraulic parameters, and finally the rainfall infiltration analysis of the permeable asphalt pavement is realized.

Description

Rainfall infiltration evaluation method for permeable asphalt pavement based on laboratory test and inversion of unsaturated hydraulic parameters

technical field

The invention relates to a rainwater infiltration analysis technology for permeable asphalt pavement based on laboratory tests and unsaturated hydraulic parameter inversion, and belongs to the technical field of road engineering pavement permeable performance analysis.

Background technique

The domestic research on the rainfall infiltration model of permeable asphalt pavement is mainly based on the saturated seepage theory. There are few studies on the unsaturated-saturated rainfall infiltration. The saturated-unsaturated seepage of porous media is studied. The unsaturated permeability coefficient of the material is determined as key to the research question. In unsaturated soil theory, the unsaturated permeability coefficient is mainly affected by water content and is a function of water content. The test of non-saturated permeability coefficient is more difficult. Due to the difficulty of testing methods, there are few unsaturated hydraulic parameters (soil-water characteristic parameters and unsaturated permeability coefficient) of permeable asphalt mixture at home and abroad, which are mainly obtained by empirical methods such as soil conversion formula.

In the invention CN109342295B disclosed by Professor Zhang Lei of Southeast University, some hydrological parameters such as saturated permeability coefficient and saturated volumetric water content can be obtained through infiltration experiments. n cannot be obtained through experimentation.

The soil-water characteristic parameters of the material can be obtained by using the gradation curve of the material, but this calculation is too complicated, which affects the promotion of this method.

Therefore, a simple and rapid method to determine the unsaturated parameters of permeable asphalt pavement structures has become the focus of research.

SUMMARY OF THE INVENTION

Aiming at the difficulty in obtaining the unsaturated hydraulic parameters of the existing permeable asphalt pavement, and the inaccuracy of rainfall infiltration simulation with empirical values, the present invention proposes a rainfall infiltration evaluation method for permeable asphalt pavement based on laboratory tests and inversion of unsaturated hydraulic parameters. The unsaturated hydraulic parameters of permeable asphalt pavement are obtained by parameter inversion of actual rainfall monitoring data, which can effectively predict the main unsaturated hydraulic parameters of permeable asphalt pavement and accurately evaluate its rainfall infiltration.

A rainwater infiltration evaluation method for permeable asphalt pavement based on laboratory test and unsaturated hydraulic parameter inversion, comprising the following steps:

Step 10) Build an indoor permeable asphalt pavement rainfall infiltration test device, the indoor permeable asphalt pavement rainfall infiltration test device includes: a rainfall unit for simulating rainfall; a permeable asphalt pavement structure; a soil moisture data collector for collecting permeable water Soil moisture in asphalt pavement structure; outflow data acquisition instrument for collecting outflow data at the bottom of permeable asphalt pavement structure;

Step 20) Determine the porosity, moisture content and bottom outflow data of each permeable structural layer of the permeable asphalt pavement structure through experiments;

Step 30) Use finite element software to establish a model with the same structural size as the permeable asphalt pavement, and ideally consider the boundary conditions on both sides as no-flux conditions, and the bottom as seepage surface boundary conditions. outflow to form bottom outflow, and stop outflow when the bottom porous medium is in an unsaturated state;

Step 40) inverting the unsaturated hydraulic parameters of the Van Genuchten-Mualem model of the permeable asphalt pavement structure;

Step 50) in combination with the unsaturated hydraulic parameters obtained in step 40), perform rainfall infiltration analysis on the permeable asphalt pavement structure, compare the simulation results with the test results, and introduce the Nash-Sutcliffe coefficient to evaluate the results;

Step 60) Analyze the influence of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure.

In the step 30), the permeable asphalt pavement structure includes:

The sample tube is a cylindrical structure, and the sample tube is filled with multi-layer permeable structural layers from top to bottom. An axisymmetric vertical two-dimensional coordinate system is used to establish an unsaturated hydraulic model and a triangular element grid is divided.

The minimum objective function of the unsaturated hydraulic parameter inversion in the step 40) is as formula (4):

where m _q is the number of different measurement categories;

n _qj represents the number of observations in different time and space in the same measurement value category;

表示第i时刻第j个观测点在x位置的具体观测值；

Represents the specific observation value of the jth observation point at the i-th time at the x position;

q _j (x, t _i , b) represents the model calculation value of the corresponding parameters (such as θ _r , θ _s , α, n, m, K _s , etc.) of the jth observation point at the ith moment at the x position;

v _j ,wi _,j represent the weight of a certain observation value and observation point;

where m _p represents the number of different hydraulic characteristic parameters;

n _pj represents the number of observations of the same hydraulic characteristic parameters in different time spaces;

表示第i个水力特性参数第j个观测点在x位置的具体观测值；

represents the specific observation value of the jth observation point of the i-th hydraulic characteristic parameter at the x position;

p _j (x,θ _i ,b) represents the model calculated value of the i-th hydraulic characteristic parameter and the j-th observation point at the x position;

表示某一水力特性参数的观测值和观测点的权重；

Indicates the observation value of a hydraulic characteristic parameter and the weight of the observation point;

表示某一水力特性参数的迭代前数值；

Represents the pre-iteration value of a hydraulic characteristic parameter;

b _j (x) represents the iterative value of a hydraulic characteristic parameter;

表示某一水力特性参数权重。

Indicates the weight of a hydraulic characteristic parameter.

In described step 50), the Nash-Sutcliffe coefficient calculation formula adopted is such as formula (5):

In the formula, Q _obs,i represents the observed value of the outflow test at the bottom of the permeable asphalt pavement;

Q _sim,i represents the simulated value of the outflow at the bottom of the permeable asphalt pavement model;

表示底部出流观测平均值。

Indicates the mean value of bottom outflow observations.

In the step 60), the effect of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure is analyzed by using the bottom outflow response obtained from the simulation. The effect of rainfall intensity on the outflow delay time, outflow peak value, and retention rate at the bottom was used to obtain the drainage capacity and water storage capacity of the permeable asphalt pavement structure in response to different rainfall events.

Beneficial effects:

1. The present invention cannot accurately analyze the rainfall infiltration and stagnation of permeable asphalt pavement considering the saturated seepage theory, and the unsaturated hydraulic parameters are more complicated to obtain through experiments. Finally, the rainfall infiltration analysis of permeable asphalt pavement is realized, and the evaluation results are more reasonable and accurate.

2. The present invention uses finite element software to establish a model of the same size as the laboratory test, and performs the inversion of the unsaturated hydraulic parameters of the Van Genuchten-Mualem model. Compared with the saturated seepage theory, it is more in line with the actual state of rainfall infiltration of permeable asphalt pavement.

3. The present invention combines the laboratory test with the inversion of unsaturated hydraulic parameters, realizes the rainfall infiltration analysis of the permeable asphalt pavement structure, and evaluates the response of different rainfall intensities to its bottom outflow (outflow delay time, outflow peak value, retention time) rate) effect.

Description of drawings

Fig. 1 is the flow chart of the rainwater infiltration evaluation method of permeable asphalt pavement based on indoor test and unsaturated hydraulic parameter inversion according to the present invention;

Fig. 2 is the schematic diagram of the indoor permeable asphalt pavement rainfall infiltration test system of the present invention:

Among them, 1 is a water supply device, 2 is a peristaltic pump, 3 is a shower, 4 is a wire mesh, 5 is a connector, 6 is a sensor, 7 is a geotextile, and 8 is a water valve;

Figure 3 is a schematic diagram of the finite element model of the permeable asphalt pavement structure;

Figure 4 is a schematic diagram of the simulated and observed outflow values at the bottom of the permeable pavement.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

The embodiment of the present invention proposes a method for evaluating rainfall infiltration of permeable asphalt pavement based on laboratory tests and unsaturated hydraulic parameter inversion. As shown in FIG. 1 , the method includes the following steps:

Step 10) Design an indoor permeable asphalt pavement rainfall infiltration test system, which is divided into three parts: each structure of the permeable asphalt pavement, including: a sample cylinder with a cylindrical structure, and the sample cylinder is filled with multiple layers of permeable water from top to bottom. Structural layer, the sample tube is a 1000mm long diameter, 160mm plexiglass tube, and the interior is each structural layer of the permeable asphalt pavement;

Rainfall system, including water supply device, peristaltic pump, shower;

Data collection system, including soil moisture data collector and outflow data collector.

In step 10), the humidity sensor is calibrated, and the result is y=0.621x-0.425, and the relationship between the rotational speed of the peristaltic pump (x) and the rainfall intensity (y) is determined to be y=3.48x-1.69.

Step 20) Determine the porosity of each structural layer of the permeable asphalt pavement structure through experiments, design a permeable asphalt pavement structure combination, monitor the rainfall infiltration process of the structure combination in real time, and obtain the water content and outflow at different locations for subsequent use. analog input.

Step 30) Use finite element software to establish a model with the same size as the laboratory test, and ideally consider the boundary conditions on both sides to be no-flux conditions according to the actual situation, and the bottom of the device is the seepage surface boundary condition. Seepage to form bottom outflow, and stop outflow when the bottom porous medium is in an unsaturated state.

In step 30), considering that the research test device is cylindrical, an axisymmetric vertical two-dimensional coordinate system is used to establish a finite element model, and a triangular element mesh is divided.

In step 40), the unsaturated hydraulic parameters of the VanGenuchten-Mualem model of the permeable asphalt pavement structure are inverted in combination with the measured data of the bottom outflow obtained in the step 20).

In step 40), the essence of the unsaturated hydraulic parameter inversion is to iterate the equation continuously, and the selection of parameters is realized by minimizing the objective function. The minimum objective function of the unsaturated hydraulic parameter inversion is as formula (4):

表示第i时刻第j个观测点在x位置的具体观测值；q_j(x,t_i,b)表示第i时刻第j个观测点在x位置的相应参数(如θ_r、θ_s、α、n、m、K_s等)的模型计算值；v_j,w_i,j表示某一观测值和观测点的权重；其中m_p表示不同水力特性参数的数目；n_pj表示同种水力特性参数在不同时间空间的观测数目；

表示第i个水力特性参数第j个观测点在x位置的具体观测值；p_j(x,θ_i,b)表示表示第i个水力特性参数第j个观测点在x位置的模型计算值；

表示某一水力特性参数的观测值和观测点的权重；

表示某一水力特性参数的迭代前数值；b_j(x)表示某一水力特性参数的迭代后数值；

表示某一水力特性参数权重。In the above formula, m _q represents the number of different measurement categories; n _qj represents the number of observations in different time and space in the same measurement value category;

represents the specific observation value of the jth observation point at the i-th time at the x position; q _j (x,t _i ,b) represents the corresponding parameters of the j-th observation point at the i-th time at the x position (such as θ _r , θ _s , α, n, m, K _s , etc.) model calculation value; v _j , w _{i, j} represent the weight of a certain observation value and observation point; where m _p represents the number of different hydraulic characteristic parameters; n _pj represents the same hydraulic The number of observations of characteristic parameters in different time spaces;

Represents the specific observation value of the jth observation point of the i th hydraulic characteristic parameter at the x position; p _j (x, θ _i , b) represents the model calculated value of the j th observation point of the i th hydraulic characteristic parameter at the x position ;

Indicates the observation value of a hydraulic characteristic parameter and the weight of the observation point;

Represents the pre-iteration value of a hydraulic characteristic parameter; b _j (x) represents the post-iteration value of a certain hydraulic characteristic parameter;

Indicates the weight of a hydraulic characteristic parameter.

Step 50) Combine the unsaturated hydraulic parameters obtained in step 40), conduct rainfall infiltration analysis on the permeable asphalt pavement structure, compare the simulation results with the test results, and introduce the Nash-Sutcliffe coefficient (NSE) to evaluate the results.

In step 50), the adopted Nash-Sutcliffe coefficient calculation formula is as formula (5):

表示底部出流观测平均值。In the above formula, Q _obs,i represents the observed value of the outflow test at the bottom of the permeable asphalt pavement; Q _sim,i represents the simulated value of the outflow at the bottom of the permeable asphalt pavement model;

Indicates the mean value of bottom outflow observations.

Step 60) Analyze the influence of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure.

In step 60), the effect of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure is analyzed by using the bottom outflow response (outflow delay time, outflow peak value, retention rate) obtained from the simulation.

The following is a specific application of the method of the embodiment of the present invention.

Step 1: Build an indoor permeable asphalt pavement rainfall infiltration test system, as shown in Figure 2.

Step 2. Determine a permeable asphalt pavement structure, namely: permeable asphalt surface layer 10cm+large void asphalt gravel base 8cm+graded gravel 30cm+sand cushion 20cm and obtain the porosity of each structural layer through experiments, the specific pavement structure is: PAC -13 (porosity 16.5%) 4cm+PAC-20 (porosity 19.7%) 6cm+LSPM-25 (porosity 20.3%) 8cm+GM graded gravel 30cm+sand cushion 20cm.

Step 3. Use the HYDRUS software to build a model with the same size as the indoor test. Considering that the research test device is cylindrical, an axisymmetric vertical two-dimensional coordinate system is used to divide the triangular element grid. The grid size is 0.5cm and the number of grids is 6660, and the HYDRUS simulation also requires the following assumptions: ① the single-layer material is homogeneous in all directions; ② the water flow only seeps out from the inside of the material. Therefore, the boundary conditions on both sides are ideally considered as no-flux conditions, and the bottom of the device is the seepage surface boundary condition. The specific HYDRUS model is shown in Figure 3.

Step 4: Invert the unsaturated hydraulic parameters of the Van Genuchten-Mualem model of the permeable asphalt pavement structure. Considering the limitation of the software iteration rate, this test does not invert all the material VG model parameters. In the VG model of porous media, θ _s , θ _r , α, and n are the main factors affecting porous media materials. It is generally believed that when a porous medium is saturated, its saturated volumetric water content depends on the porosity, so θ _s is known. The iterative ranges and initial values of other material parameters are shown in Table 1.

Table 1 Value range and initial value of each material parameter

The parameters of the VG model of the permeable asphalt pavement structure inversion using HYDRUS combined with the experimental observation data are summarized in Table 2.

Table 2 VG model parameters of permeable asphalt pavement structural materials

Step 5: Combine the unsaturated hydraulic parameters obtained in Step 4, perform rainfall infiltration analysis on the permeable asphalt pavement structure, and calculate the NSE coefficient value of the bottom outflow simulation value and experimental observation value of the permeable pavement structure to be 0.974.

Figure 4 is a schematic diagram of the simulated and observed values, which are relatively close, indicating that the simulated results are reasonable and credible.

Step 6: Study the rainfall infiltration response of the permeable asphalt pavement structure under different rainfall intensities. The rainfall intensities are 3mm/min, 6mm/min, 9mm/min and 12mm/min respectively.

The outflow responses at the bottom of the permeable asphalt pavement structure under different rainfall intensities are listed in Table 3

Table 3 Outflow response at the bottom of permeable asphalt pavement structure under different rainfall intensities

It can be seen from the data in Table 3 that the outflow peak value at the bottom of the permeable asphalt pavement structure increases with the increase of rainfall intensity, while the outflow delay time and retention rate decrease with the increase of rainfall intensity.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above-mentioned specific embodiments, and the descriptions in the above-mentioned specific embodiments and the specification are only to further illustrate the principle of the present invention, without departing from the spirit and scope of the present invention, the present invention Various changes and modifications of the invention are also possible, all of which fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the claims and their equivalents.

Claims (5)

1. A permeable asphalt pavement rainfall infiltration evaluation method based on indoor tests and unsaturated hydraulic parameter inversion is characterized by comprising the following steps:

step 10) constructing an indoor permeable asphalt pavement rainfall infiltration test device, wherein the indoor permeable asphalt pavement rainfall infiltration test device comprises: the rainfall unit is used for simulating rainfall; a permeable asphalt pavement structure; the soil humidity data acquisition instrument is used for acquiring the soil humidity in the permeable asphalt pavement structure; the outflow data acquisition instrument is used for acquiring outflow data at the bottom of the permeable asphalt pavement structure;

step 20) determining the void ratio, the water content and the bottom outflow data of each permeable structure layer of the permeable asphalt pavement structure through tests;

step 30) establishing a model with the same structural size as the permeable asphalt pavement by using finite element software, ideally considering boundary conditions on two sides as a no-flux condition, wherein the bottom is a seepage surface boundary condition which can seep out when porous media are saturated to form bottom outflow, and stopping outflow when the porous media at the bottom are in an unsaturated state;

step 40) carrying out inversion on unsaturated hydraulic parameters of a Van Genuchten-Mualem model of the permeable asphalt pavement structure;

step 50) combining the unsaturated hydraulic parameters obtained in the step 40), carrying out rainfall infiltration analysis on the permeable asphalt pavement structure, comparing a simulation result with a test result, and introducing a Nash-Sutcliffe coefficient to evaluate the result;

and step 60) analyzing the influence of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure.

2. The method for evaluating rainfall infiltration of permeable asphalt pavement based on indoor test and inversion of unsaturated hydraulic parameters according to claim 1, wherein in the step 30), the permeable asphalt pavement structure comprises:

the device comprises a sample cylinder with a cylindrical structure, wherein multiple water permeable structure layers are filled in the sample cylinder from top to bottom, an axial-symmetry vertical two-dimensional coordinate system is adopted to establish a non-saturated hydraulic model, and a triangular unit grid is divided.

3. The method for evaluating the rainfall infiltration of the permeable asphalt pavement based on the indoor test and the unsaturated hydraulic parameter inversion according to claim 1, wherein the minimum objective function of the unsaturated hydraulic parameter inversion in the step 40) is as shown in formula (4):

in the formula, m _q Expressed as the number of different measurement categories;

n _qj representing the number of observations over different time spaces in the same measurement value category;

representing a specific observation value of a j observation point at the x position at the ith moment;

q _j (x,t _i and b) represents the corresponding parameter (e.g., θ) of the jth observation point at the ith time at the x position _r 、θ _s 、α、n、m、K _s Etc.);

v _j ,w _i,j a weight representing an observation and an observation point;

wherein m is _p Representing the number of different hydraulic characteristic parameters;

n _pj representing the observed number of the hydraulic characteristic parameters of the same type in different time spaces;

a specific observed value of a jth observed point of the ith hydraulic characteristic parameter at the x position is represented;

p _j (x,θ _i b) represents a model calculation value representing the ith hydraulic characteristic parameter at the position of the jth observation point in x;

representing an observed value of a certain hydraulic characteristic parameter and the weight of an observed point;

a pre-iteration value representing a certain hydraulic characteristic parameter;

b _j (x) Indicating a certain hydraulic powerAn iterated value of the characteristic parameter;

representing the weight of a certain hydraulic characteristic parameter.

4. The method for evaluating the rainfall infiltration of the permeable asphalt pavement based on the indoor test and the unsaturated hydraulic parameter inversion according to claim 1, wherein in the step 50), the calculation formula of the Nash-Sutcliffe coefficient is as shown in formula (5):

in the formula, Q _obs,i Representing the observation value of the outflow test at the bottom of the permeable asphalt pavement;

Q _sim,i representing a bottom outflow simulation value of the permeable asphalt pavement model;

mean bottom outflow observations are shown.

5. The method for evaluating the rainfall infiltration of the permeable asphalt pavement based on the indoor test and the inversion of the unsaturated hydraulic parameters according to claim 1, wherein in the step 60), the influence of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure is analyzed by using the bottom outflow response obtained by simulation, and the specific analysis mode is that the influence of the rainfall intensity on the bottom outflow delay time, the outflow peak value and the retention rate is analyzed according to the obtained simulated values of the bottom outflow response under different rainfall intensities, so that the drainage capacity and the water storage capacity of the permeable asphalt pavement structure for different rainfall events are obtained.

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