Structure deflection prediction method based on full-scale asphalt pavement life cycle test

Abstract

The present application relates to a kind of structure deflection prediction methods based on full-size asphalt pavement full life cycle test, belong to road engineering technical field.The method of the present application is based on full-size pavement full life cycle test, the present application is completely same with the structure of the road to be predicted, material, load action mode, natural environment and so on condition, can obtain the long-term evolution data of structure deflection that can complete the full life cycle of asphalt pavement, on this basis, the structure deflection prediction carried out, can greatly improve the precision and reliability of performance prediction, to ensure the accuracy and reliability of pavement design.The prediction method of the present application is used to predict the structure deflection of asphalt pavement in full life cycle, provides necessary reference and basis for asphalt pavement structure design and maintenance and repair decision.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, and in particular to a method for predicting structural deflection based on full-life-cycle tests of asphalt pavement. Background Technology

[0002] Predicting the service performance of asphalt pavements throughout their entire life cycle is crucial for pavement design and maintenance decisions. It serves as an important basis for controlling the rationality of pavement design and the timeliness of maintenance decisions, and is also a vital prerequisite for ensuring the long-term performance and durability of the pavement. The entire life cycle of asphalt pavements generally refers to the entire process from pavement construction to final failure. According to relevant provisions in my country's design specifications, for highways, the service life should be at least 15 years, or equivalent to 50 million cycles of the equivalent design axle load.

[0003] Among various indicators for evaluating the service performance of asphalt pavements, deflection is not only a key indicator characterizing the structural performance of asphalt pavements, but also a primary basis for the design and acceptance of asphalt pavements for highways of all grades in my country. Currently, in the technical condition assessment of asphalt pavements in my country, deflection accounts for 40% of the score. The magnitude of deflection directly reflects the current structural bearing capacity level of in-service asphalt pavements and directly controls whether the pavement structure requires deep maintenance and treatment, making it a key indicator for formulating structural maintenance and treatment plans. Therefore, accurately predicting the changes in deflection indicators of asphalt pavements throughout their entire service life is of significant practical importance for understanding the time-varying laws of pavement structural strength and taking timely and effective maintenance and treatment strategies. This ensures that the pavement structure receives effective maintenance and treatment, extending its service life and lifespan. Therefore, accurately predicting the structural deflection of asphalt pavements throughout their entire service life and making timely maintenance decisions is of significant practical importance for improving the current condition of pavements and extending their service life.

[0004] Currently, although researchers at home and abroad have conducted a great deal of research on the prediction of deflection index of asphalt pavement and have developed many representative prediction methods, these methods are generally based on test data from the first few years (2-7 years) after the asphalt pavement is built. They are acceptable for predicting the short-term service performance of asphalt pavement, but due to the lack of evolution data on service performance throughout the entire life cycle, the extension of the prediction methods is poor. They are unreliable for predicting the long-term performance of asphalt pavement, especially since they cannot accurately predict the entire process of service performance evolution of asphalt pavement from construction to the end of its service life.

[0005] Therefore, in order to accurately predict the structural deflection of asphalt pavement throughout its entire life cycle, it is essential to accurately obtain the structural deflection evolution behavior of the asphalt pavement throughout its entire life cycle. Moreover, only by conducting structural deflection tests covering the entire life cycle evolution of asphalt pavement on actual-sized or full-scale road structures, under the natural environment and load conditions of actual service of the asphalt pavement, and establishing corresponding structural deflection prediction methods based on these tests, can the accuracy and reliability of the structural deflection prediction results be guaranteed. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a structural deflection prediction method based on full-scale asphalt pavement life-cycle tests. This method is used to predict the structural deflection of asphalt pavements throughout their entire life-cycle, providing necessary reference and basis for asphalt pavement structural design and maintenance decisions.

[0007] The structural deflection prediction method based on full-scale asphalt pavement life-cycle tests includes the following steps:

[0008] 1) Based on the basic conditions of the road for which structural deflection prediction is to be carried out, determine the road grade, design service life, traffic load grade, cumulative number of equivalent design axle loads within the design service life that meets the requirements of the whole life cycle of asphalt pavement, as well as the asphalt pavement structure type and material type of each structural layer.

[0009] 2) Construct a full-scale pavement with the same structure and materials as the proposed road in an open natural environment. The full-scale pavement shall be at least 7.5m wide (equivalent to two lanes), at least 50m long, and all structural layers shall be of the same thickness as those of the proposed road. The pavement materials shall be constructed using normal construction techniques.

[0010] 3) Use actual vehicles as test loading devices. The vehicle type is a truck with two or more axles. Loading is carried out in a one-way, channelized traffic manner. The vehicle running speed is 60-80km / h. Formula (1) is used to convert the axle load of each axle of the loaded truck into the equivalent design axle load action number. The number of loaded trucks is not less than 4.

[0011]

[0012] Where: N i —The number of equivalent design axle loads applied to the i-th axle of the truck;

[0013] C1—Shaft group coefficient. When the distance between the front and rear shafts is greater than 3m, it is calculated as a single shaft. When the distance between the shafts is less than 3m, the coefficient is 2.1 for double shafts and 3.2 for triple shafts.

[0014] C2 – Wheelset coefficient, 1 for dual-wheelset and 4.5 for single-wheelset;

[0015] P i —The axle load of the i-th axle of the truck, in kN;

[0016] 4) Set up weather stations or temperature sensors in the open natural environment where the full-scale road surface is located to continuously observe the atmospheric temperature, with an observation frequency of once every 5-15 minutes;

[0017] 5) Conduct long-term loading tests on full-scale road surfaces using a test loading device;

[0018] 6) After approximately 10,000 to 1,200,000 equivalent design axle loads have been accumulated, the structural deflection of the full-scale pavement is measured once using a falling weight deflectometer. A deflection monitoring point is established every 10 meters along the driving direction. For each measurement, deflection is measured at each monitoring point under four falling weight loads: 50kN, 70kN, 90kN, and 110kN, and the deflection basin area is obtained.

[0019] 7) Collect all atmospheric temperature data observed by meteorological stations or temperature sensors when the cumulative number of times the design axle load of 1-1.2 million equivalents is completed in step 6), and calculate the average value of these data as the representative value of atmospheric temperature.

[0020] 8) When the cumulative number of equivalent design axle load applications that meet the requirements of the entire life cycle of asphalt pavement has been completed, loading shall be temporarily stopped;

[0021] 9) Compile and organize all structural deflection test data, cumulative number of equivalent design axle loads, and representative atmospheric temperature values ​​under four types of drop hammer loads during the full-life-cycle loading test of the full-scale pavement.

[0022] 10) Establish the correlation between the data in step 9) according to formula (2), determine the regression coefficients by fitting, and perform error analysis. The average relative error should not be greater than 10%.

[0023] y=k1·x1+k2·x2+k3·sin(k4·x3)+k5·x1·sin(k4·x3)+k6 (2)

[0024] In the formula: y—area of ​​the deflection basin, in mm 2 ;

[0025] x1 — Logarithm of the cumulative number of equivalent design axle loads, base 10;

[0026] x2 — Falling weight load, in kN;

[0027] x3 — Representative value of atmospheric temperature, in °C;

[0028] k1, k2, k3, k4, k5, k6 — regression coefficients;

[0029] 11) Use Equation (2) to predict the structural deflection of the road to be predicted. Substitute the cumulative number of equivalent design axle loads, drop weight load, and representative atmospheric temperature value that the road to be predicted will actually bear after it is built and opened to traffic into Equation (2) to obtain the structural deflection prediction result.

[0030] The prediction method further includes an accuracy evaluation step, which includes:

[0031] A1) Continue loading tests on the full-scale pavement until the cumulative number of times the new equivalent design axle load is applied reaches 2-10 million, at which point loading can be stopped. Following the methods in steps 6) and 7), obtain structural deflection data and representative atmospheric temperature values ​​for each approximately 600,000-1,200,000 equivalent design axle load cumulative applications.

[0032] A2) Use the data in step 11) to evaluate the accuracy of equation (2), calculate the average relative error between the measured value and the calculated value, and ensure that the average relative error is controlled within 10%. Otherwise, equation (2) should be corrected or reconstructed until the relative error requirement is met.

[0033] The test loading device is a four-axle, five-axle, or six-axle trailer.

[0034] The test loading device increases the axle load of the truck to 1.5-2 times the design axle load by adding counterweights inside the truck bed.

[0035] In step 6), at least three parallel tests are conducted under each load, and the average area of ​​the deflection basin is taken as the structural deflection at that point.

[0036] Every 600,000 to 1,200,000 equivalent design axle loads are applied cumulatively, and the structural deflection of the full-scale pavement is measured once using a falling weight deflectometer.

[0037] The full-scale road surface is 9m wide and is divided from left to right by markings into: a 1m wide left shoulder, a 3.75m wide overtaking lane, a 3.75m wide driving lane, and a 1m wide right shoulder. The driving lane is used as the test loading lane, and the overtaking lane is used as the test comparison lane. The full-scale road surface is 60m long.

[0038] Compared with current structural deflection prediction methods, this invention is based on the results of structural deflection tests on asphalt pavement throughout its entire life cycle, and has the following advantages and inventiveness.

[0039] (1) It can achieve service performance observation throughout the entire life cycle. The cumulative number of equivalent design axle loads during the test process can reach tens of millions of times, which is equivalent to more than ten years of service life. Compared with the existing methods based on several years of test data, it is an order of magnitude improvement.

[0040] (2) The vehicle load used in the test was the same vehicle used on the actual road surface. The vehicle model was the actual vehicle model and was not simplified. The vehicle load was used in a unidirectional, channelized manner, which was completely consistent with the actual road surface. The speed of the vehicle load was also able to reach the speed of heavy trucks on the actual road surface.

[0041] (3) The test environment is the actual natural environment, which changes constantly throughout the year. It is not the test environment under certain specific test temperatures or high-temperature seasons in the existing methods. The natural environment it is subjected to can better simulate the impact of natural environmental changes on service performance.

[0042] (4) As the load and environment act simultaneously during the actual test, the load is constantly increasing and the environment is changing alternately, which can most realistically simulate the synchronous coupling effect of the load and environment.

[0043] Therefore, it can be seen that the present invention has the same structure, materials, load application mode, natural environment and other conditions as the road to be predicted. It can obtain long-term evolution data of structural deflection that can completely cover the entire life cycle of asphalt pavement. The structural deflection prediction carried out on this basis can greatly improve the accuracy and reliability of performance prediction, thereby ensuring the accuracy and credibility of pavement design. Attached Figure Description

[0044] Figure 1 A schematic diagram of the asphalt pavement structure and materials of a certain highway.

[0045] Figure 2 Full-scale road lane marking diagram. Detailed Implementation

[0046] Taking the structural deflection prediction requirement of an asphalt pavement of a highway as an example, the content of this invention is described in detail.

[0047] 1) Based on the relevant technical documents for the design and construction of this expressway, the basic conditions of the road for which structural deflection prediction is to be conducted can be determined as follows: the road grade is expressway, the design service life is 15 years, the traffic load level is extra-heavy traffic, and the cumulative number of equivalent design axle loads within the design service life of the asphalt pavement, meeting the full life cycle requirements, is not less than 50 million cycles. The asphalt pavement structural type and material types of each structural layer are as follows: Figure 1As shown, from bottom to top, the layers are: a 20cm thick cement-stabilized soil subbase, a 20cm thick cement-stabilized crushed stone base, an 18cm thick cement-stabilized crushed stone base, an 8cm thick A70 asphalt concrete lower layer, a 6cm thick SBS modified asphalt concrete intermediate layer, and a 4cm thick SBS modified asphalt concrete upper layer, with a total pavement structure thickness of 76cm.

[0048] 2) Constructed in an open-air natural environment and Figure 1 A full-scale pavement with identical structure and materials to the asphalt pavement. The full-scale pavement is 9.5m wide. Figure 2 As shown, from left to right, the road is divided by road markings into: a 1m wide left shoulder, a 3.75m wide overtaking lane, a 3.75m wide driving lane, and a 1m wide right shoulder. The driving lane serves as the test loading lane, and the overtaking lane serves as the test control lane. The full-scale pavement is 60m long. The thickness of each structural layer of the full-scale pavement is... Figure 1 The road is planned to have identical thicknesses for each layer. During construction, asphalt mixing plants and water-stabilized mixing plants will be used to produce the road surface materials, and pavers and rollers will be used for on-site construction.

[0049] 3) A six-axle trailer was used as the test loading device. The loading mode was one-way, channelized traffic, and the average speed of the vehicle was 70 km / h. In order to improve the test loading efficiency, six loading trucks were used to load simultaneously in all weather conditions. Precast cement concrete standard counterweights were used in the truck bed of the six-axle trailer for counterweighting. Each counterweight had a dry weight of 1 ton, and the total number of counterweights was 65. According to formula (1), the cumulative number of equivalent design axle loads applied by each loading truck when passing through the full-length road surface is approximately 72.

[0050] 4) Set up a small weather station in the open natural environment where the full-length road surface is located to continuously observe the atmospheric temperature, and store the atmospheric temperature in real time every 10 minutes.

[0051] 5) Conduct long-term loading tests on full-scale road surfaces using six-axle trailers.

[0052] 6) When approximately 800,000 equivalent design axle loads have been accumulated, the structural deflection of the full-scale pavement is tested once using a falling weight deflectometer. A deflection monitoring point is set up every 10m along the driving direction. During each test, the deflection of each deflection monitoring point is tested under four falling weight loads of 50kN, 70kN, 90kN, and 110kN to obtain the deflection basin area. At least three parallel tests are carried out under each load, and the average value of the deflection basin area is taken as the structural deflection of that point.

[0053] 7) Collect all atmospheric temperature data observed by the meteorological station when approximately 800,000 equivalent design axle loads have been applied in step 6), and calculate the average value of these data as the representative value of atmospheric temperature.

[0054] 8) When the cumulative number of equivalent design axle loads that meet the full life cycle requirements of the asphalt pavement structure to be predicted is completed, the loading test will be temporarily stopped. The specific number of times is 50.37 million.

[0055] 9) Summarize and organize all structural deflection test data, cumulative number of equivalent design axle loads, and representative atmospheric temperature values ​​under four types of drop hammer loads during the full-life cycle loading test of the full-scale pavement, as shown in Table 1.

[0056] Table 1. Structural deflection test data of full-scale pavement throughout its entire life cycle.

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] Note: Serial numbers 1-98, 99-196, 197-294, and 295-392 represent the test data of 50kN, 70kN, 90kN, and 110kN drop hammer loads, respectively.

[0071] 10) According to the correlation between the data in step 9) fitted by equation (2), the values ​​of regression coefficients k1, k2, k3, k4, k5, and k6 are 8.6533, 1.2568, 12.5192, 0.9838, -1.8476, and -52.8514, respectively. Substituting these values ​​into equation (2) yields the specific expression, as shown in equation (3). Through error calculation, it can be seen that the average relative error of equation (3) is 0.83%, which meets the requirement that the average relative error should not exceed 10%. Therefore, equation (3) has small error, high accuracy, and good reliability.

[0072] y=8.6533·x1+1.2568·x2+12.5192·sin(0.9838·x3)-1.8476·x1·sin(0.9838·x3)-52.8514 (3)

[0073] In the formula: y — structural deflection, in units of 0.01 mm;

[0074] x1 — Logarithm of the cumulative number of equivalent design axle loads, base 10;

[0075] x2 — Falling weight load, in kN;

[0076] x3 — Representative value of atmospheric temperature, in °C;

[0077] 11) Continue to conduct loading tests on the full-scale pavement. Stop loading when the cumulative number of times the newly added design axle load of approximately 9 million is completed, i.e., the total number of times reaches 59.36 million. According to the methods in steps 6) and 7), obtain the structural deflection test data and representative atmospheric temperature values ​​when approximately 800,000 equivalent design axle loads are completed, as shown in Table 2.

[0078] Table 2. Deflection test data of full-scale pavement new structures.

[0079]

[0080]

[0081]

[0082] 12) The accuracy of equation (3) is evaluated using the data in step 11). The average relative error between the measured value and the calculated value is 2.85%, which is less than the relative error control value of 10%. Therefore, equation (3) does not need to be corrected or reconstructed and can be used for structural deflection prediction.

[0083] 13) Use equation (3) to predict the structural deflection of the road to be predicted. Given that the actual cumulative number of equivalent design axle loads experienced by the road after a period of operation is 25 million cycles, the representative atmospheric temperature is 22.5℃, and the drop weight load is 50kN, the predicted deflection basin area of ​​the asphalt pavement structure under these conditions is 74.0 mm. 2 .

Claims

1. A structural deflection prediction method based on full-scale asphalt pavement life-cycle tests, comprising the following steps: 1) Based on the basic conditions of the road for which structural deflection prediction is to be carried out, determine the road grade, design service life, traffic load grade, cumulative number of equivalent design axle loads within the design service life that meets the requirements of the whole life cycle of asphalt pavement, as well as the asphalt pavement structure type and material type of each structural layer. 2) Construct a full-scale pavement with the exact same structure and materials as the predicted road in an open, natural environment; among which, The full-scale pavement has a width of at least 7.5m for two lanes, a length of at least 50m, and the thickness of each structural layer of the full-scale pavement is exactly the same as the thickness of each layer of the road to be predicted. The pavement material is constructed using normal construction techniques. 3) Use actual vehicles as test loading devices. The vehicle type is a truck with two or more axles. Loading is carried out in a one-way, channelized traffic manner. The vehicle running speed is 60-80km / h. Formula (1) is used to convert the axle load of each axle of the loaded truck into the equivalent design axle load action number. The number of loaded trucks is not less than 4. Where: N i —The number of equivalent design axle loads applied to the i-th axle of the truck; C1—Shaft group coefficient. When the distance between the front and rear shafts is greater than 3m, it is calculated as a single shaft. When the distance between the shafts is less than 3m, the coefficient is 2.1 for double shafts and 3.2 for triple shafts. C2 – Wheelset coefficient, 1 for dual-wheelset and 4.5 for single-wheelset; P i —The axle load of the i-th axle of the truck, in kN; 4) Set up weather stations or temperature sensors in the open natural environment where the full-scale road surface is located to continuously observe the atmospheric temperature, with an observation frequency of once every 5-15 minutes; 5) Conduct long-term loading tests on full-scale road surfaces using a test loading device; 6) After each cumulative number of applications of the design axle load from 1 to 1,200,000 equivalents, the structural deflection of the full-scale pavement is measured once using a falling weight deflectometer. A deflection monitoring point is established every 10 meters along the driving direction. For each measurement, deflection is measured at each monitoring point under four falling weight loads: 50kN, 70kN, 90kN, and 110kN, and the deflection basin area is obtained. 7) Collect all atmospheric temperature data observed by meteorological stations or temperature sensors when the cumulative number of times the design axle load of 1-1.2 million equivalents is completed in step 6), and calculate the average value of these data as the representative value of atmospheric temperature. 8) When the cumulative number of equivalent design axle load applications that meet the requirements of the entire life cycle of asphalt pavement has been completed, loading shall be temporarily stopped; 9) Compile and organize all structural deflection test data, cumulative number of equivalent design axle loads, and representative atmospheric temperature values ​​under four types of drop hammer loads during the full-life-cycle loading test of the full-scale pavement. 10) Establish the correlation between the data in step 9) according to formula (2), determine the regression coefficients by fitting, and perform error analysis. The average relative error should not be greater than 10%. y=k1·x1+k2·x2+k3·sin(k4·x3)+k5·x1·sin(k4·x3)+k6(2) Where: y——area of ​​the deflection basin, in mm 2 ; x1 — Logarithm of the cumulative number of equivalent design axle loads, base 10; x2 — Falling weight load, in kN; x3 — Representative value of atmospheric temperature, in °C; k1, k2, k3, k4, k5, k6 — regression coefficients; 11) Use Equation (2) to predict the structural deflection of the road to be predicted. Substitute the cumulative number of equivalent design axle loads, drop weight load, and representative atmospheric temperature value that the road to be predicted will actually bear after it is built and opened to traffic into Equation (2) to obtain the structural deflection prediction result.

2. The prediction method according to claim 1 further includes an accuracy evaluation step, the accuracy evaluation step comprising: A1) Continue to conduct loading tests on the full-scale pavement. When the cumulative number of times the new equivalent design axle load is applied is completed (2-10 million), the loading can be stopped. According to the methods in steps 6) and 7), obtain the structural deflection test data and representative atmospheric temperature values ​​when the cumulative number of times the equivalent design axle load is applied is completed (600,000-1,200,000). A2) Use the data in step 11) to evaluate the accuracy of equation (2), calculate the average relative error between the measured value and the calculated value, and ensure that the average relative error is controlled within 10%. Otherwise, equation (2) should be corrected or reconstructed until the relative error requirement is met.

3. The prediction method according to claim 1, wherein the test loading device is a four-axle, five-axle, or six-axle trailer.

4. According to the prediction method of claim 1, the test loading device increases the axle load of the truck to 1.5-2 times the design axle load by adding counterweights in the truck bed.

5. According to the prediction method of claim 1, in step 6), more than 3 parallel tests are carried out under each load, and the average value of the deflection basin area is taken as the structural deflection at that point.

6. According to the prediction method of claim 1, in step 6), every time the cumulative number of times the equivalent design axle load is applied is completed, the structural deflection of the full-scale pavement is detected once using a falling weight deflectometer.

7. According to the prediction method of claim 1, the full-scale road surface is 9m wide and is divided from left to right by markings into: a 1m wide left shoulder, a 3.75m wide overtaking lane, a 3.75m wide driving lane, and a 1m wide right shoulder. The driving lane is used as the test loading lane, and the overtaking lane is used as the test comparison lane. The full-scale road surface is 60m long.

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