Evaluation method of rainfall infiltration of permeable asphalt pavement based on indoor test and inversion of unsaturated hydraulic parameters

Abstract

The present invention discloses a method for evaluating rainfall infiltration of permeable asphalt pavement based on indoor tests and inversion of unsaturated hydraulic parameters, including building an indoor test platform for rainfall infiltration of permeable asphalt pavement; real-time monitoring of the rainfall infiltration process of permeable asphalt mixture; establishing a finite element model with the same size as the indoor experimental device through rainfall infiltration simulation software; inverting the unsaturated hydraulic parameters of the permeable asphalt mixture in combination with the measured data of bottom outflow; simulating the rainfall infiltration process of the permeable asphalt pavement structure using the obtained unsaturated hydraulic parameters; and analyzing the influence of rainfall intensity on the outflow response of the permeable asphalt pavement structure. The present invention considers that the saturated seepage theory cannot accurately analyze the rainfall infiltration and stagnation effect of the permeable asphalt pavement, and the unsaturated hydraulic parameters are relatively complex to obtain through experiments. Therefore, the unsaturated hydraulic parameters are inverted through the initial data obtained through indoor tests, and finally the rainfall infiltration analysis of the permeable asphalt pavement is realized.

Description

Technical Field

[0001] The invention relates to a rainfall infiltration analysis technology for a permeable asphalt pavement based on indoor tests and inversion of unsaturated hydraulic parameters, belonging to the technical field of permeability analysis of road engineering pavements. Background Art

[0002] Domestic research on rainfall infiltration models for permeable asphalt pavements is mainly based on saturated seepage theory, and there are few studies on unsaturated-saturated rainfall infiltration. The key to studying the saturated-unsaturated seepage of porous media is to determine the unsaturated permeability coefficient of the material. In the theory of unsaturated soil, the unsaturated permeability coefficient is mainly affected by the water content and is a function of the water content. The test of the unsaturated permeability coefficient is more difficult. Due to the difficulty of the test method, there are currently few unsaturated hydraulic parameters (soil-water characteristic parameters and unsaturated permeability coefficient) of permeable asphalt mixtures at home and abroad, and they are mainly obtained by empirical methods such as soil conversion formulas.

[0003] In the invention CN109342295B disclosed by Professor Zhang Lei of Southeast University, some hydrological parameters such as saturated permeability coefficient and saturated volume water content can be obtained through permeation experiments, but the parameter α related to the void intake pressure and the pore size distribution fitting parameter n in the Van Genuchten-Mualem model cannot be obtained through experiments.

[0004] The soil-water characteristic parameters of the material can be obtained using the material grading curve, but the calculation is too complicated, which affects the promotion of this method.

[0005] Therefore, a simple and fast method to determine the unsaturated parameters of permeable asphalt pavement structure has become the focus of research. Summary of the invention

[0006] In view of the difficulty in obtaining the unsaturated hydraulic parameters of existing permeable asphalt pavements and the inaccuracy of rainfall infiltration simulation using empirical values, the present invention proposes a rainfall infiltration evaluation method for permeable asphalt pavement based on indoor tests and unsaturated hydraulic parameter inversion. The unsaturated hydraulic parameters of the permeable asphalt pavement are obtained by parameter inversion using actual rainfall monitoring data. The method can effectively predict the main unsaturated hydraulic parameters of the permeable asphalt pavement and accurately evaluate its rainfall infiltration.

[0007] A method for evaluating rainfall infiltration of permeable asphalt pavement based on indoor tests and inversion of unsaturated hydraulic parameters includes the following steps:

[0008] Step 10) constructing an indoor permeable asphalt pavement rainfall infiltration test device, the indoor permeable asphalt pavement rainfall infiltration test device comprising: a rainfall unit for simulating rainfall; a permeable asphalt pavement structure; a soil moisture data collector for collecting soil moisture in the permeable asphalt pavement structure; an outflow data collector for collecting outflow data at the bottom of the permeable asphalt pavement structure;

[0009] Step 20) determining the porosity, moisture content and bottom outflow data of each permeable structural layer of the permeable asphalt pavement structure through experiments;

[0010] Step 30) using finite element software to establish a model with the same size as the permeable asphalt pavement structure, and the boundary conditions on both sides are ideally considered to be no-flux conditions, and the bottom is a seepage surface boundary condition, which allows rainwater to seep out when the porous medium is saturated to form a bottom outflow, and stops outflow when the bottom porous medium is in an unsaturated state;

[0011] Step 40) inverting the unsaturated hydraulic parameters of the Van Genuchten-Mualem model of the permeable asphalt pavement structure;

[0012] Step 50) combining the unsaturated hydraulic parameters obtained in step 40) to perform rainfall infiltration analysis on the permeable asphalt pavement structure, and comparing the simulation results with the test results, and introducing the Nash-Sutcliffe coefficient to evaluate the results;

[0013] Step 60) Analyze the effect of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure.

[0014] In the step 30), the permeable asphalt pavement structure comprises:

[0015] The sample tube is a cylindrical structure, and multiple layers of permeable structure are filled in the sample tube from top to bottom. An unsaturated hydraulic model is established using an axisymmetric vertical two-dimensional coordinate system, and a triangular unit grid is divided.

[0016] The minimum objective function of the unsaturated hydraulic parameter inversion in step 40) is as follows:

[0017]

[0018] In the formula, m q It is expressed as the number of different measurement categories;

[0019] n qj Indicates the number of observations in different time and space in the same measurement value category;

[0020] Represents the specific observation value of the jth observation point at the x position at the i-th time;

[0021] q j (x,t i , b) represents the corresponding parameters of the jth observation point at the x position at the i-th time (such as θ r ,θ s ,α,n,m,K s Model calculation values ​​of (etc.);

[0022] v j ,w i,j Represents the weight of a certain observation value and observation point;

[0023] Where m p Indicates the number of different hydraulic characteristic parameters;

[0024] n pj It represents the number of observations of the same hydraulic characteristic parameters in different time and space;

[0025] It represents the specific observation value of the jth observation point of the i-th hydraulic characteristic parameter at the x position;

[0026] p j (x,θ i , b) represents the model calculated value of the i-th hydraulic characteristic parameter at the j-th observation point at the x position;

[0027] Represents the observed value of a certain hydraulic characteristic parameter and the weight of the observation point;

[0028] Indicates the value of a hydraulic characteristic parameter before iteration;

[0029] b j (x) represents the iterated value of a hydraulic characteristic parameter;

[0030] Represents the weight of a hydraulic characteristic parameter.

[0031] In step 50), the Nash-Sutcliffe coefficient calculation formula used is as follows:

[0032]

[0033] In the formula, Q obs,i It represents the observed value of the bottom outflow test of permeable asphalt pavement;

[0034] Q sim,i It represents the simulated value of the bottom outflow of the permeable asphalt pavement model;

[0035] represents the observed average of bottom outflow.

[0036] In the step 60), the simulated bottom outflow response is used to analyze the effect of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure. The specific analysis method is to analyze the effect of rainfall intensity on the bottom outflow delay time, outflow peak value, and retention rate based on the bottom outflow response simulation values ​​obtained under different rainfall intensities, so as to obtain the drainage capacity and water storage capacity of the permeable asphalt pavement structure in response to different rainfall events.

[0037] Beneficial effects:

[0038] 1. The present invention considers that the saturated seepage theory cannot accurately analyze the rainfall infiltration and storage effect of permeable asphalt pavement, and it is relatively complicated to obtain unsaturated hydraulic parameters through experiments. The initial data obtained through indoor experiments are used to invert the unsaturated hydraulic parameters, and finally the rainfall infiltration analysis of permeable asphalt pavement is realized, and the evaluation results are more reasonable and accurate.

[0039] 2. The present invention uses finite element software to establish a model of the same size as the indoor test and performs 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 on permeable asphalt pavement.

[0040] 3. The present invention combines indoor tests with the inversion of unsaturated hydraulic parameters to realize rainfall infiltration analysis of permeable asphalt pavement structures and evaluate the effects of different rainfall intensities on their bottom outflow response (outflow delay time, outflow peak, and retention rate). BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of the rainfall infiltration evaluation method of permeable asphalt pavement based on indoor test and inversion of unsaturated hydraulic parameters of the present invention;

[0042] Figure 2 This is a schematic diagram of the indoor permeable asphalt pavement rainfall infiltration test system of the present invention:

[0043] Among them, 1 is a water supply device, 2 is a peristaltic pump, 3 is a shower head, 4 is a wire mesh, 5 is a connector, 6 is a sensor, 7 is a geotextile, and 8 is a water valve;

[0044] Figure 3 It is a schematic diagram of the finite element model of the permeable asphalt pavement structure;

[0045] Figure 4 Schematic diagram of simulated and observed outflow values ​​at the bottom of permeable pavement. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0047] The embodiment of the present invention proposes a method for evaluating rainfall infiltration of permeable asphalt pavement based on indoor tests and inversion of unsaturated hydraulic parameters. Figure 1 As shown, the method comprises the following steps:

[0048] Step 10) Design an indoor permeable asphalt pavement rainfall infiltration test system, which is divided into three parts: various structures of the permeable asphalt pavement, including: a cylindrical sample tube, in which multiple layers of permeable structural layers are filled from top to bottom, and the sample tube is a 1000mm long, 160mm diameter, organic glass tube, and the interior is various structural layers of the permeable asphalt pavement;

[0049] Rainfall system, including water supply device, peristaltic pump, shower head;

[0050] The data collection system includes a soil moisture data collector and an outflow data collector.

[0051] In step 10), the humidity sensor was calibrated, and the result was y=0.621x-0.425, and the relationship between the peristaltic pump speed (x) and the rainfall intensity (y) was determined to be y=3.48x-1.69.

[0052] Step 20) The porosity of each structural layer of the permeable asphalt pavement structure is determined through experiments, and a permeable asphalt pavement structure combination is designed. The rainfall infiltration process of the structure combination is monitored in real time to obtain the moisture content and outflow at different locations for subsequent simulation input.

[0053] Step 30) Use finite element software to establish a model with the same size as the indoor test, and ideally consider the boundary conditions on both sides as no-flux conditions based on actual conditions. The bottom of the device is a seepage surface boundary condition. Under this boundary condition, rainwater can seep out of the porous medium when it is saturated, forming a bottom outflow. When the bottom porous medium is in an unsaturated state, the outflow stops.

[0054] 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 divide the triangular unit grid.

[0055] Step 40) combines the bottom outflow measured data obtained in step 20) to invert the unsaturated hydraulic parameters of the VanGenuchten-Mualem model of the permeable asphalt pavement structure.

[0056] In step 40), the essence of the inversion of unsaturated hydraulic parameters is to continuously iterate the equations and select the parameters by minimizing the objective function. The minimum objective function of the inversion of unsaturated hydraulic parameters is as follows:

[0057]

[0058] In the above formula, mq Expressed as the number of different measurement categories; n qj Indicates 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 x position at the i-th time; q j (x,t i , b) represents the corresponding parameters of the jth observation point at the x position at the i-th time (such as θ r ,θ s ,α,n,m,K s etc.) model calculation value; v j ,w i,j Represents the weight of a certain observation value and observation point; where m p Indicates the number of different hydraulic characteristic parameters; n pj It represents the number of observations of the same hydraulic characteristic parameters in different time and space; represents the specific observation value of the i-th hydraulic characteristic parameter at the j-th observation point at position x; p j (x,θ i , b) represents the model calculated value of the i-th hydraulic characteristic parameter at the j-th observation point at the x position; Represents the observed value of a certain hydraulic characteristic parameter and the weight of the observation point; represents the value of a hydraulic characteristic parameter before iteration; b j (x) represents the iterated value of a hydraulic characteristic parameter; Represents the weight of a hydraulic characteristic parameter.

[0059] Step 50) combines the unsaturated hydraulic parameters obtained in step 40) to perform rainfall infiltration analysis on the permeable asphalt pavement structure, and compares the simulation results with the test results, introducing the Nash-Sutcliffe coefficient (NSE) to evaluate the results.

[0060] In step 50), the Nash-Sutcliffe coefficient calculation formula used is as follows:

[0061]

[0062] In the above formula, Q obs,i represents the observed value of the bottom outflow test of permeable asphalt pavement; Q sim,i It represents the simulated value of the bottom outflow of the permeable asphalt pavement model; represents the observed average of bottom outflow.

[0063] Step 60) Analyze the effect of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure.

[0064] In step 60), the influence of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure is analyzed using the bottom outflow response (outflow delay time, outflow peak value, retention rate) obtained by simulation.

[0065] The following is a specific application of the method of the embodiment of the present invention.

[0066] Step 1: Construct an indoor permeable asphalt pavement rainfall infiltration test system. Figure 2 shown.

[0067] Step 2: Determine a permeable asphalt pavement structure, namely: permeable asphalt surface layer 10cm + large-void asphalt gravel base layer 8cm + graded gravel 30cm + sand cushion layer 20cm and obtain the void ratio of each structural layer through experiments. The specific pavement structure is: PAC-13 (void ratio 16.5%) 4cm + PAC-20 (void ratio 19.7%) 6cm + LSPM-25 (void ratio 20.3%) 8cm + GM graded gravel 30cm + sand cushion layer 20cm.

[0068] Step 3: Use 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 unit grid. The grid size is 0.5 cm and the number of grids is 6660. The following assumptions are required for HYDRUS simulation: ① The single-layer material is homogeneous in all directions; ② Water only seeps out from the inside of the material. Therefore, the boundary conditions on both sides are ideally considered to be no-flux conditions, and the bottom of the device is the seepage surface boundary condition. The specific HYDRUS model is as follows: Figure 3 .

[0069] 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 experiment does not invert the VG model parameters of all materials. 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 the porous media is saturated, its saturated volume water content depends on the porosity, so θ s The iteration ranges and initial values ​​of other material parameters are shown in Table 1.

[0070] Table 1 Range and initial value of each material parameter

[0071]

[0072] The VG model parameters of permeable asphalt pavement structure inverted by HYDRUS combined with test observation data are summarized in Table 2.

[0073] Table 2 VG model parameters of permeable asphalt pavement structural materials

[0074]

[0075] Step 5: Combined with the unsaturated hydraulic parameters obtained in step 4, the rainfall infiltration analysis of the permeable asphalt pavement structure is carried out, and the NSE coefficient value of the bottom outflow simulation value and the experimental observation value of the permeable pavement structure is calculated to be 0.974.

[0076] Figure 4 This is a schematic diagram of simulated values ​​and observed values. The two are relatively close, indicating that the simulation results are reasonable and reliable.

[0077] 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.

[0078] The bottom outflow response of the permeable asphalt pavement structure under different rainfall intensities is summarized in Table 3.

[0079] Table 3 Outflow response of the bottom of the permeable asphalt pavement structure under different rainfall intensities

[0080]

[0081] 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.

[0082] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above specific embodiments. The above specific embodiments and the description in the specification are only for further illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the claims and their equivalents.

Claims

1. A rainfall infiltration evaluation method for permeable asphalt pavement based on indoor tests and inversion of unsaturated hydraulic parameters. It is characterized in that The following steps are involved: Step 10) constructing an indoor permeable asphalt pavement rainfall infiltration test device, the indoor permeable asphalt pavement rainfall infiltration test device comprising: a rainfall unit for simulating rainfall; a permeable asphalt pavement structure; a soil moisture data collector for collecting soil moisture in the permeable asphalt pavement structure; an outflow data collector for collecting outflow data at the bottom of the permeable asphalt pavement structure; Step 20) determining the porosity, moisture content and bottom outflow data of each permeable structural layer of the permeable asphalt pavement structure through experiments; Step 30) using finite element software to establish a model with the same size as the permeable asphalt pavement structure, and the boundary conditions on both sides are ideally considered to be no-flux conditions, and the bottom is a seepage surface boundary condition, which allows rainwater to seep out when the porous medium is saturated to form a bottom outflow, and stops 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) combining the unsaturated hydraulic parameters obtained in step 40) to perform rainfall infiltration analysis on the permeable asphalt pavement structure, and comparing the simulation results with the test results, and introducing the Nash-Sutcliffe coefficient to evaluate the results; Step 60) Analyze the effect 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, It is characterized in that In the step 30), the permeable asphalt pavement structure comprises: The sample tube is a cylindrical structure, and multiple layers of permeable structure are filled in the sample tube from top to bottom. An unsaturated hydraulic model is established using an axisymmetric vertical two-dimensional coordinate system, and a triangular unit grid is divided.

3. The method for evaluating rainfall infiltration of permeable asphalt pavement based on indoor test and inversion of unsaturated hydraulic parameters according to claim 1, It is characterized in that The minimum objective function of the unsaturated hydraulic parameter inversion in step 40) is as follows: In the formula, m q It is expressed as the number of different measurement categories; n qj Indicates 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 x position at the i-th time; q j (x,t i , b) represents the corresponding parameters of the jth observation point at the x position at the i-th time (such as θ r ,θ s ,α,n,m,K s Model calculation values ​​of (etc.); v j ,w i,j Represents the weight of a certain observation value and observation point; Where m p Indicates the number of different hydraulic characteristic parameters; n pj It represents the number of observations of the same hydraulic characteristic parameters in different time and space; It represents the specific observation value of the i-th hydraulic characteristic parameter at the j-th observation point at the x position; p j (x,θ i , b) represents the model calculated value of the i-th hydraulic characteristic parameter at the j-th observation point at the x position; Represents the observed value of a certain hydraulic characteristic parameter and the weight of the observation point; Indicates the value of a hydraulic characteristic parameter before iteration; b j (x) represents the iterated value of a hydraulic characteristic parameter; Represents the weight of a hydraulic characteristic parameter.

4. The method for evaluating rainfall infiltration of permeable asphalt pavement based on indoor test and inversion of unsaturated hydraulic parameters according to claim 1, It is characterized in that In step 50), the Nash-Sutcliffe coefficient calculation formula used is as follows: In the formula, Q obs,i It represents the observed value of the bottom outflow test of permeable asphalt pavement; Q sim,i It represents the simulated value of the bottom outflow of the permeable asphalt pavement model; represents the observed average of bottom outflow.

5. The method for evaluating rainfall infiltration of permeable asphalt pavement based on indoor test and inversion of unsaturated hydraulic parameters according to claim 1, It is characterized in that In the step 60), the simulated bottom outflow response is used to analyze the effect of rainfall intensity on the rainfall infiltration process of the permeable asphalt pavement structure. The specific analysis method is to analyze the effect of rainfall intensity on the bottom outflow delay time, outflow peak value, and retention rate based on the bottom outflow response simulation values ​​obtained under different rainfall intensities, so as to obtain the drainage capacity and water storage capacity of the permeable asphalt pavement structure in response to different rainfall events.

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