Ground penetrating radar-based pavement asphalt base grouting effect evaluation method

Abstract

The invention discloses a ground penetrating radar-based pavement asphalt base grouting effect evaluation method, which relates to the technical field of road engineering, can be used for representing the repairing effect of grouting on a pavement asphalt base, and comprises the following steps: coring to test parameters such as base electromagnetic parameters and volume parameters of each phase; testing the relative dielectric constant of the used grouting material; testing the two-way travel time of electromagnetic waves in the base layer before grouting; calculating a comprehensive correction coefficient; testing the two-way travel time of electromagnetic waves in the base layer after grouting; and calculating the probability distribution interval of the filling density of the base layer after grouting. Compared with an existing manual coring observation method, the method has the advantage that the detection efficiency and coverage are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering, and particularly to a method for evaluating the grouting effect of asphalt-based roadbeds based on ground penetrating radar. Background Art

[0002] Some roads use asphalt materials such as asphalt macadam as the roadbed. Under the combined action of traffic loads and environmental loads, asphalt roadbeds are prone to diseases such as loosening and fragmentation. If not disposed of in time, it will seriously affect the bearing capacity of the road structure, causing secondary diseases such as cracks and fragmentation on the road surface. Using materials such as polymers to grout and repair the roadbed is a common repair method for asphalt roadbeds with frequent diseases of loosening and fragmentation. The polymers and other materials are filled into the excessive voids in the loosened and fragmented parts of the asphalt roadbed, thereby strengthening the roadbed. Currently, in order to test the grouting effect, that is, the filling situation of the grouting material in the voids, the core sampling method is generally used for manual observation, with low efficiency and a small coverage area. In addition, in order to ensure a certain expansion and contraction space for the asphalt mortar in the roadbed, the void ratio of the roadbed after grouting is not the smaller the better, but there is a certain ideal void ratio. Summary of the Invention

[0003] In order to solve the above technical problems, based on the travel time characteristics of electromagnetic waves in the asphalt roadbed before and after grouting, and considering the influence of the measured travel time fluctuations on the calculation results, a calculation method for the probability distribution interval of the filling density of the roadbed after grouting is proposed. The larger the median value of the interval, the closer the actual void ratio of the asphalt roadbed after grouting is to the ideal void ratio. The method in this patent significantly improves the detection efficiency and coverage area compared with the existing manual core sampling observation method.

[0004] The above object is achieved by the following technical solutions:

[0005] The present invention provides a method for evaluating the grouting effect of asphalt-based roadbeds based on ground penetrating radar, including the following steps

[0006] S1. Core sampling to test parameters such as the electromagnetic parameters and volume parameters of each phase of the roadbed;

[0007] S2. Test the relative dielectric constant of the grouting material used;

[0008] S3. Test the two-way travel time of electromagnetic waves in the roadbed before grouting;

[0009] S4. Calculate the comprehensive correction coefficient;

[0010] S5. Test the two-way travel time of electromagnetic waves in the roadbed after grouting;

[0011] S6. Calculate the probability distribution interval of the filling density of the roadbed after grouting.

[0012] The further limited technical solution of the present invention is:

[0013] Further, the step S1 includes the following steps

[0014] S1.1. Randomly drill multiple core samples of the asphalt base course, with the total number not less than 10;

[0015] S1.2. Use a dielectric constant network analyzer to measure the relative dielectric constants of the coarse aggregate phase and the asphalt mortar phase in the core samples of the asphalt base course, and take their average values, denoted as ε a and ε b respectively. The relative dielectric constant of the void phase is taken as ε v = 1;

[0016] S1.3. Measure the volume fractions of the coarse aggregate phase, the asphalt mortar phase, and the void phase in the core samples of the pavement asphalt base course, and take their average values, denoted as V a , V b and V v respectively;

[0017] S1.4. Measure the height of the core samples of the pavement asphalt base course, and take their average value as the base course thickness H.

[0018] Further, in the step S2, the relative dielectric constant of the grouting material used can be measured by various methods such as the capacitance method, the resonance method, the spectroscopy method, and the microwave method, denoted as ε z .

[0019] Further, in the step S3, a ground penetrating radar is used to measure the two-way travel time of electromagnetic waves in the base course before grouting at multiple on-site measurement points, and the number of measurement points is not less than 10. The measured two-way travel time results should pass the Shapiro-Wilk test to ensure that they follow a normal distribution. If the test fails, the number of measurement points should be increased until the test passes. Finally, the two-way travel time of electromagnetic waves in the base course before grouting satisfies the normal distribution N(T, σ 2 ), where T and σ are the average value and the standard deviation of the two-way travel time of the base course measured at different measurement points before grouting, respectively.

[0020] Further, in the step S4, the comprehensive correction coefficient K is calculated according to Equation (1), where c is the electromagnetic wave speed in vacuum.

[0021]

[0022] Further, in step S5, a ground penetrating radar is used to measure the two-way travel time of electromagnetic waves in the base course after grouting at multiple on-site measuring points. The number of measuring points shall be no less than 10. The measured two-way travel time results shall pass the Shapiro-Wilk test to ensure that they meet the normal distribution. If the test is not passed, the number of measuring points shall be increased until the test is passed. Finally, the two-way travel time of electromagnetic waves in the base course before grouting meets the normal distribution N(T′,σ′ 2 ), where T′ and σ′ are the mean and standard deviation of the two-way travel time of the base course measured at different measuring points after grouting, respectively.

[0023] Further, step S6 includes the following steps

[0024] S6.1. Calculate the median M of the base course filling density interval after grouting according to formula (2), where c is the electromagnetic wave speed in vacuum, and V 0 is the ideal void ratio that the asphalt base course after grouting is expected to achieve. If the void ratio of the asphalt base course after grouting is equal to the ideal void ratio, then M = 1. Therefore, the closer the M value is to 1, the closer the actual void ratio of the asphalt base course after grouting is to the ideal void ratio, and the better the grouting effect. If M > 1, it indicates that the actual void ratio of the asphalt base course after grouting is less than the ideal void ratio. If M < 1, it indicates that the actual void ratio of the asphalt base course after grouting is greater than the ideal void ratio.

[0025]

[0026] S6.2. Calculate the fluctuation value N of the base course filling density after grouting according to formula (3), where c is the electromagnetic wave speed in vacuum, and V 0 is the ideal void ratio that the asphalt base course after grouting is expected to achieve.

[0027]

[0028] S6.3. Determine the probability distribution interval of the base course filling density after grouting: There is a 99.7% probability within the range of [M - 3N, M + 3N], a 95.4% probability within the range of [M - 2N, M + 2N], and a 68.3% probability within the range of [M - N, M + N]. Expand the base course filling density from the interval median M to a distribution interval for evaluating the grouting effect of the base course.

[0029] The beneficial effects of the present invention are:

[0030] Filling polymers and other materials into the excessive voids in the loose and broken asphalt base course is a common reinforcement method for road bases. Currently, to test the filling effect of grouting materials in the voids, the core sampling method is generally used for manual observation, which has low efficiency and a small coverage area. In response to this, based on the travel time characteristics of electromagnetic waves in the asphalt base course before and after grouting, and considering the influence of the measured travel time fluctuations on the calculation results, this patent proposes a calculation method for the probability distribution interval of the filling density of the base course after grouting. The larger the median of the interval, the closer the actual void ratio of the asphalt base course after grouting is to the ideal void ratio. The method in this patent significantly improves the detection efficiency and coverage compared with the existing manual core sampling observation method, and introduces a probability range, expanding the filling density of the base course from a specific value to a normal distribution interval, which can make the detection and evaluation results of the grouting effect more reliable and ensure that the actual filling density of the base course is within the proposed distribution interval. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall process of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] Example 1: For the asphalt base course core samples drilled from a certain road, the average relative dielectric constants of the coarse aggregate phase and the asphalt mortar phase are measured to be ε a = 10 and ε b = 5 respectively. The average volume fractions of the coarse aggregate phase, the asphalt mortar phase, and the void phase are measured to be V a = 0.61, V b = 0.21 and V v = 0.18 respectively. The average value of the height of the base course core samples, that is, the base course thickness H = 0.3, and the relative dielectric constant ε z = 4.5 of the grouting material used is measured. The two-way travel time of electromagnetic waves in the base course before grouting measured on site satisfies the normal distribution N(T, σ 2 ), where T = 5.081 ns and σ = 0.015 ns; the two-way travel time of electromagnetic waves in the base course after grouting satisfies the normal distribution N(T′, σ′ 2 ), where T ′ = 5.312 ns and σ ′ = 0.020 ns.

[0033] The comprehensive correction coefficient K = 0.985 is calculated, the median M of the filling density interval of the base course after grouting is 0.747, and finally the probability distribution interval of the filling density of the base course after grouting is obtained: there is a 99.7% probability within the range of [0.504, 0.989], a 95.4% probability within the range of [0.585, 0.908], and a 68.3% probability within the range of [0.666, 0.828].

[0034] Example 2: For the asphalt base core samples drilled from a certain road, the average relative dielectric constants of the coarse aggregate phase and the asphalt mortar phase are measured as ε a = 8 and ε b = 4.5 respectively. The average volume fractions of the coarse aggregate phase, the asphalt mortar phase, and the void phase are measured as V a = 0.55, V b = 0.18 and V v = 0.27 respectively. The average value of the height of the base core sample, that is, the base thickness H = 0.35, and the relative dielectric constant ε z = 3.9 of the grouting material used is measured. The two-way travel time of electromagnetic waves in the base before grouting measured on site satisfies the normal distribution N(T, σ 2 ), where T = 5.315 ns and σ = 0.022 ns; the two-way travel time of electromagnetic waves in the base after grouting satisfies the normal distribution N(t′, σ′ 2 ), where T ′ = 5.625 ns and σ ′ = 0.012 ns.

[0035] The comprehensive correction coefficient K = 1.003 is calculated, the median M of the filling density interval of the base after grouting is 0.574, and finally the probability distribution interval of the filling density of the base after grouting is obtained: there is a 99.7% probability within the range of [0.435, 0.713], a 95.4% probability within the range of [0.481, 0.667], and a 68.3% probability within the range of [0.528, 0.621].

[0036] In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A method for evaluating the grouting effect of asphalt base of pavement based on ground penetrating radar, characterized in that: The following steps are included S1. Take the core sample of asphalt base, test the electromagnetic parameters of the base and the volume parameters of each phase, and test the height of the core sample of asphalt base of the pavement; S2, relative dielectric constant of the grouting material used for testing; S3, testing the two-way travel time of electromagnetic waves in the base before grouting; S4. Calculate the comprehensive correction coefficient; S5. Test the two-way travel time of electromagnetic waves in the base after grouting; S6. Calculate the probability distribution range of the base filling density after grouting.

2. The method for evaluating the grouting effect of asphalt base of pavement based on ground penetrating radar according to claim 1 is characterized in that: The step S1 comprises the following steps: S1.

1. Drill multiple asphalt base core samples randomly, with a total number of no less than 10; S1.

2. Use a dielectric constant network analyzer to test the relative dielectric constants of the coarse aggregate phase and the asphalt mortar phase in the asphalt base core sample, and take the average value, which is recorded as ε a and ε b , the relative dielectric constant of the void phase is ε v =1; S1.

3. Test the volume fractions of the coarse aggregate phase, asphalt mortar phase, and void phase in the core sample of the asphalt base of the pavement, and take their average values, which are recorded as V a , V b and V v ; S1.

4. Test the height of the core sample of the asphalt base of the road surface and take the average value as the base thickness H.

3. The method for evaluating the grouting effect of asphalt base of pavement based on ground penetrating radar according to claim 1, characterized in that: The relative dielectric constant of the grouting material used in the test in step S2 is obtained by using one of the capacitance method, resonance method, spectroscopy method, and microwave method. The relative dielectric constant of the grouting material used is denoted as ε z .

4. The method for evaluating the grouting effect of asphalt base of pavement based on ground penetrating radar according to claim 1, characterized in that: The specific method of step S3 is: using a ground penetrating radar to test the two-way travel time of electromagnetic waves in the base before grouting at multiple on-site measuring points, with the number of measuring points being no less than 10; then performing a Shapiro-Wilk test on the measured two-way travel time results to ensure that they satisfy the normal distribution. If the Shapiro-Wilk test is not passed, the number of measuring points should be increased to repeat the two-way travel time of the electromagnetic waves in the base before grouting until the measured two-way travel time results pass the Shapiro-Wilk test; and finally obtaining the two-way travel time of the electromagnetic waves in the base before grouting that satisfies the normal distribution N(T,σ 2 ), where T and σ are the mean and standard deviation of the two-way travel time of the base layer measured at different measuring points before grouting.

5. The method for evaluating the grouting effect of asphalt base of pavement based on ground penetrating radar according to claim 1, characterized in that: The comprehensive correction coefficient in step S4 is calculated according to formula (1): Where K is the comprehensive correction coefficient and c is the electromagnetic wave speed in vacuum.

6. The method for evaluating the grouting effect of asphalt base of pavement based on ground penetrating radar according to claim 1, characterized in that: In step S5, the two-way travel time of the electromagnetic wave in the base after grouting is tested by using a ground penetrating radar, and the two-way travel time of the electromagnetic wave in the base after grouting is tested at multiple on-site measuring points, and the number of measuring points is not less than 10; then the measured two-way travel time result is subjected to a Shapiro-Wilk test to ensure that it satisfies the normal distribution. If it fails the Shapiro-Wilk test, the number of measuring points should be increased to test the two-way travel time of the electromagnetic wave in the base after grouting until the measured two-way travel time result passes the Shapiro-Wilk test; finally, the two-way travel time of the electromagnetic wave in the base before grouting is obtained to satisfy the normal distribution N(T′,σ′ 2 ), where T′ and σ′ are the mean and standard deviation of the two-way travel time of the base layer measured at different measuring points after grouting, respectively.

7. The method for evaluating the grouting effect of asphalt base of pavement based on ground penetrating radar according to claim 1, characterized in that: The step S6 comprises the following steps: S6.

1. Calculate the median value M of the filling density of the base after grouting according to formula (2). Where c is the electromagnetic wave velocity in vacuum, V0 is the ideal porosity that the asphalt base layer hopes to achieve after grouting; if the porosity of the asphalt base layer after grouting is equal to the ideal porosity, then M=1, so the closer the M value is to 1, the closer the actual porosity of the asphalt base layer after grouting is to the ideal porosity, and the better the grouting effect; if M>1, it means that the actual porosity of the asphalt base layer after grouting is less than the ideal porosity, and if M<1, it means that the actual porosity of the asphalt base layer after grouting is greater than the ideal porosity; S6.

2. Calculate the base density fluctuation value N after grouting according to formula (3): S6.

3. Determine the probability distribution interval of the base filling density after grouting: there is a 99.7% probability in the range of [M-3N, M+3N], a 95.4% probability in the range of [M-2N, M+2N], and a 68.3% probability in the range of [MN, M+N]. The base filling density is expanded from the median M to a distribution interval for the evaluation of the base grouting effect to ensure that the actual base filling density is within the proposed distribution interval.

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