A method for detecting the state of an asphalt pavement layer

Abstract

This application provides a method for detecting the interlayer condition of asphalt pavement. The method characterizes the interlayer condition through in-situ torsional shear strength. First, it constructs fitting curves for in-situ torsional shear strength versus field compaction work and in-situ torsional shear strength versus field impact work. Then, based on the two curves, it obtains field compaction work and field impact work data for the same in-situ torsional shear strength value, constructing a conversion curve between field compaction work and field impact work. Before the formal paving of the surface layer, standard specimens are placed on the tack coat / chip seal layer, and the converted field compaction work is applied to the standard specimens using a compaction instrument. Immediately afterwards, an in-situ torsional shear test is conducted. The measured in-situ torsional shear strength is the predicted value of the interlayer in-situ torsional shear strength that can be achieved after the actual paving and compaction of the upper layer. This method effectively avoids the waste of materials and time caused by the need for reconstructing the upper layer due to unqualified strength, significantly improving construction efficiency and reliability.

Description

Technical Field

[0001] This application relates to the field of road inspection technology, and in particular to a method for detecting the interlayer condition of asphalt pavement. Background Technology

[0002] Asphalt pavements are multi-layered structures, typically including a base course, surface layer, intermediate layer, and bottom layer. In the construction of multi-layered asphalt pavements, the interlayer bond strength is crucial to the pavement's integrity and durability. If the interlayer bond strength is insufficient, relative slippage and shear deformation will occur between layers under traffic loads, leading to a series of defects such as localized heave, surface cracking, and interlayer delamination. Therefore, it is necessary to effectively monitor the interlayer bond strength during the construction process.

[0003] Currently, the common practice is to conduct strength tests through in-situ torsion-shear, pull-out, or core drilling sampling only after the tack coat, chip seal, and upper structure (such as asphalt pavement) have been completed and compacted. However, this method has inherent drawbacks: it is a post-construction test, and the entire interlayer structure has already solidified by the time of testing. If the strength does not meet the standards, the completed upper structure must be milled and reconstructed, resulting in significant losses of materials, time, and costs. Furthermore, conventional laboratory simulations cannot accurately reproduce the complex compaction work and material interactions on-site, leading to significant discrepancies between laboratory test results and actual on-site conditions, making it impossible to objectively evaluate the interlayer condition on-site.

[0004] Therefore, it is necessary to propose a method that can detect the final interlayer state in real time before the upper structure is laid and during the construction process. Summary of the Invention

[0005] The purpose of this application is to provide a method for detecting the interlayer condition of asphalt pavement. Before the actual paving of the upper layer, the method can accurately predict the in-situ interlayer torsional shear strength between any two road structures by simulating construction conditions within the range where the interlayer torsional shear strength effectively increases with compaction work. This enables pre-construction quality control during the construction process, avoids rework and waste, and improves construction efficiency and reliability.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] It is important to note that the interlayer torsional shear strength exhibits a saturation effect with increasing compaction work. Once the compaction work continues to increase beyond a certain critical value (saturation point), the strength no longer increases significantly. The establishment and application of the method of this invention are strictly limited to the effective growth range before reaching this saturation point. Therefore, this method has clear engineering applicability.

[0008] This application provides a method for detecting the interlayer condition of asphalt pavement, including the following steps:

[0009] Step 1: Determine the construction parameters and on-site compaction work for the target road section;

[0010] On-site total impact formula Where W is the total compaction work on site, in J; m is the mass of the hammer, in kg; g is the gravitational acceleration, 9.8 N / kg; h is the height of the hammer above the compaction surface, in m; and N is the number of hammer blows.

[0011] On-site compaction work formula: ( For on-site compaction work, the unit is J; The actual mass of the compaction wheel is expressed in kg; g is the acceleration due to gravity, 9.8 N / kg. The settlement before and after compaction is expressed in meters (m).

[0012] Step 2: Establish the in-situ torsional shear strength - field compaction work benchmark curve: Select a representative road section on-site (on the underlayer structure), and select several small test sections within it. Apply the tack coat and chip seal coat according to the construction parameters of Step 1, pave the actual upper layer material, and measure the initial height of the upper layer using a ruler; use a standard road roller (with a defined actual compaction wheel mass m)... b The entire test section was compacted, starting from an initial number of compaction passes. Each small test section underwent a different number of passes (simulating different on-site compaction efforts). After compaction and cooling to temperature T, the compacted height of the mixture was measured using a ruler. Simultaneously, in-situ torsional shear tests were immediately conducted on each small test section to obtain the in-situ torsional shear strength value at that compaction pass. This process continued until the increase in strength value with increasing compaction pass rate significantly decreased (i.e., approached saturation). A set of in-situ torsional shear strength data, h, was obtained. b The settlement before and after compaction is given by the in-situ compaction work formula. An in-situ torsional shear strength-in-situ compaction work fitting curve for this specific material system is established by fitting, denoted as curve A.

[0013] Step 3: Establish the fitting curve of in-situ torsional shear strength - on-site compaction work:

[0014] On the same site and the same substructure (such as each small test section), the tack coat and the crushed stone seal layer are constructed according to the above construction parameters. Standard specimens with the same material as the upper structure are placed on the crushed stone seal layer. In step two, at the same temperature, the standard specimens are subjected to different numbers of hammer blows using a compactor to simulate the on-site compaction work. After the hammering is completed, an in-situ torsional shear test is conducted to obtain the in-situ torsional shear strength. The in-situ torsional shear strength-on-site compaction work fitting curve is obtained and denoted as curve B.

[0015] Step 4: Compare curves A and B. For the same target in-situ torsional shear strength value, a corresponding in-situ compaction work and an in-situ impact compaction work can be found from the two curves respectively. Collect multiple pairs of corresponding data points under the same in-situ strength level and fit them to obtain the conversion curve between in-situ compaction work and in-situ impact compaction work, i.e., the in-situ compaction work-in-situ impact compaction work fitting curve, denoted as curve C. This curve C is the core conversion model of this invention.

[0016] Step 5: Target Section Strength Prediction: For new construction locations requiring interlayer strength prediction, only the on-site construction parameters and planned on-site compaction work need to be determined. Using the established curve C, the planned on-site compaction work is converted into the required on-site compaction work. On the lower structure at this location, a tack coat and a chip seal coat are applied according to the parameters, and then standard specimens are placed. The converted on-site compaction work (converted into the number of hammer blows) is applied to the standard specimens using a compaction instrument, and then an in-situ torsional shear test is immediately conducted. The measured in-situ torsional shear strength is the predicted value of the interlayer torsional shear strength that can be achieved after the upper structure is actually paved and compacted.

[0017] Furthermore, in step one, the construction parameters include, but are not limited to, the type and amount of tack coat / prime coat oil, the type and amount of crushed stone for the crushed stone seal, the planned compaction machinery and number of compaction cycles (i.e., on-site compaction work), and the compaction temperature.

[0018] Furthermore, in step two, after compaction, the upper structure is allowed to cool to temperature T before the height of the upper structure after compaction is measured; in step three, after hammering, the standard specimen is allowed to cool to temperature T before an in-situ torsion-shear test is performed; temperature T is 25℃.

[0019] Furthermore, in step two, in each small test section, the number of compaction cycles of the standard roller is increased sequentially from 1 to less than 1 kPa for the increase in in-situ torsional shear strength with the increase in the number of compaction cycles.

[0020] Furthermore, in step three, the number of hammer blows of the compactor starts from 50 and increases sequentially with a difference of 10-50 blows, until the increase in in-situ torsional shear strength with the increase in the number of hammer blows is less than 1 kPa.

[0021] Furthermore, in step two, a test road section of 60m-100m in length is selected on site and divided into 6-10 smaller test road sections, each of which is 8-10m long.

[0022] Furthermore, in step three, a 1m×1m area is selected in each small test section, and multiple standard Marshall specimens are placed on the tack coat / crushed stone seal layer. They are hammered a different number of times, and in-situ torsional shear is performed on each specimen to obtain its corresponding in-situ torsional shear strength.

[0023] Furthermore, the fitting in steps two, three, and four is all quadratic polynomial fitting.

[0024] In one example, for the construction of a tack coat on the AC-20 lower layer and an SMA-13 ​​upper layer, with a standard roller front wheel mass of 22,500 kg and 5 compaction cycles;

[0025] The fitting curve of in-situ torsional shear strength - on-site compaction work is as follows:

[0026] ;

[0027] The fitting curve of in-situ torsional shear strength - on-site compaction work is as follows:

[0028] ;

[0029] The conversion curve between on-site compaction work and on-site impact compaction work (fitted curve of on-site compaction work - on-site impact compaction work) is as follows:

[0030] ;

[0031] In the above formula, The in-situ torsional shear strength measured in step two is expressed in kPa. For on-site compaction work, the unit is J; The in-situ torsional shear strength measured in step three is expressed in kPa. To ensure the effectiveness of the on-site demonstration, unit J.

[0032] The technical solution of this application has the following beneficial effects:

[0033] This application establishes a quantitative conversion relationship (curve C) between on-site compaction work (actual rolling effect) and on-site impact work (simulated hammering effect) within the effective growth range of interlayer torsional shear strength. Using this relationship, the interlayer torsional shear strength can be predicted before the upper layer is laid. Before the actual paving of the upper structure (such as the top layer), the in-situ interlayer torsional shear strength between any two road structures can be accurately predicted by simulating construction conditions, thus achieving pre-construction control of construction quality. This effectively avoids the waste of materials and time caused by the need for reconstruction due to unqualified strength after the upper structure is paved, and significantly improves construction efficiency and reliability. Attached Figure Description

[0034] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein:

[0035] Figure 1 This is a schematic diagram of the fitting curves of in-situ torsional shear strength-on-site compaction work and in-situ torsional shear strength-on-site compaction work in an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the fitting curve of on-site compaction work - on-site impact work in an embodiment of the present invention. Detailed Implementation

[0037] The present application will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] It should be noted that the interlayer torsional shear strength exhibits a saturation effect with increasing compaction work. Once the compaction work continues to increase beyond a certain critical value (saturation point), the strength no longer increases significantly. The establishment and application of the method of this invention are strictly limited to the effective growth range before reaching this saturation point.

[0039] This application provides a method for detecting the interlayer condition of asphalt pavement, including the following steps:

[0040] Step 1: Determine the construction parameters and on-site compaction work for the target road section. Construction parameters include, but are not limited to, the type and amount of tack coat / prime coat oil, the type and amount of crushed stone for the chip seal layer, the planned compaction machinery and number of compaction cycles (i.e., on-site compaction work), and the compaction temperature.

[0041] On-site total impact formula Where W is the total compaction work on site, in J; m is the mass of the hammer, in kg; g is the gravitational acceleration, 9.8 N / kg; h is the height of the hammer above the compaction surface, in m; and N is the number of hammer blows.

[0042] On-site compaction work formula: ( For on-site compaction work, the unit is J; The actual mass of the compaction wheel is expressed in kg; g is the acceleration due to gravity, 9.8 N / kg. The settlement before and after compaction is expressed in meters (m).

[0043] Step 2: Establish the in-situ torsional shear strength - field compaction work benchmark curve: Select a representative road section on-site (on the underlayer structure), and select several small test sections within it. Apply the tack coat and chip seal coat according to the construction parameters from Step 1, pave the actual upper layer material, and measure the initial height of the upper layer using a ruler; use a standard roller (with a defined actual compaction wheel mass) The entire test section was compacted, starting from an initial number of compaction passes. Each small test section underwent a different number of passes (simulating varying on-site compaction work). After compaction and cooling to temperature T, the compacted height of the mixture was measured using a ruler. Simultaneously, in-situ torsional shear tests were immediately conducted on each small test section to obtain the in-situ torsional shear strength value at that compaction pass. This process continued until the increase in strength value with increasing compaction pass significantly decreased (i.e., approached saturation). A set of in-situ torsional shear strength data was obtained. The settlement of the superstructure before and after compaction is given by the in-situ compaction work formula. An in-situ torsional shear strength-in-situ compaction work fitting curve for this specific material system is established by fitting, denoted as curve A.

[0044] Step 3: Establish the fitting curve of in-situ torsional shear strength - on-site compaction work:

[0045] On the same site and the same substructure (such as each small test section), the tack coat and the crushed stone seal layer are constructed according to the above construction parameters. Standard specimens with the same material as the upper structure are placed on the crushed stone seal layer. At the same temperature as the rolling in step two, the standard specimens are subjected to different numbers of hammer blows using a compactor to simulate the on-site compaction work. After the hammering is completed, the standard specimens are allowed to cool to temperature T, and an in-situ torsional shear test is conducted to obtain the in-situ torsional shear strength. The fitting curve of in-situ torsional shear strength - on-site compaction work is obtained and denoted as curve B.

[0046] Step 4: Compare curves A and B. For the same target in-situ torsional shear strength value, a corresponding in-situ compaction work and an in-situ impact compaction work can be found from the two curves respectively. Collect multiple pairs of corresponding data points under the same in-situ strength level and fit them to obtain the conversion curve between in-situ compaction work and in-situ impact compaction work (in-situ compaction work - in-situ impact compaction work fitting curve), denoted as curve C. This curve C is the core conversion model of this invention.

[0047] Step 5: Target Section Strength Prediction: For new construction locations requiring interlayer strength prediction, only the on-site construction parameters and planned on-site compaction work need to be determined. Using the established curve C, the planned on-site compaction work is converted into the required on-site compaction work. On the lower structure at this location, a tack coat and a chip seal coat are applied according to the parameters, and then standard specimens are placed. The converted on-site compaction work (converted into the number of hammer blows) is applied to the standard specimens using a compaction instrument, and then an in-situ torsional shear test is immediately conducted. The measured in-situ torsional shear strength is the predicted value of the interlayer torsional shear strength that can be achieved after the upper structure is actually paved and compacted.

[0048] Furthermore, in step two, in each small test section, the number of compaction cycles of the standard roller is increased sequentially from 1 to less than 1 kPa for the increase in in-situ torsional shear strength with the increase in the number of compaction cycles.

[0049] Furthermore, in step three, the number of hammer blows of the compactor starts from 50 and increases sequentially with a difference of 10-50 blows, until the increase in in-situ torsional shear strength with the increase in the number of hammer blows is less than 1 kPa.

[0050] Furthermore, in step two, a test road section of 60m-100m in length is selected on site and divided into 6-10 smaller test road sections, each of which is 8-10m long.

[0051] Furthermore, in step three, a 1m×1m area is selected in each small test section, and multiple standard Marshall specimens are placed on the tack coat / crushed stone seal layer. They are hammered a different number of times, and in-situ torsional shear is performed on each specimen to obtain its corresponding in-situ torsional shear strength.

[0052] The prediction method of this application converts the in-situ compaction work obtained under different interlayer conditions, thereby achieving pre-construction prediction of interlayer conditions. It is adaptable to situations that alter the in-situ torsional shear strength of interlayers, such as different upper and lower layers, bonding materials, or the addition of a crushed stone seal layer. A specific embodiment is given below:

[0053] A method for detecting the interlayer condition of asphalt pavement includes the following steps:

[0054] Step 1: Determine the construction parameters and on-site compaction work for the target road section;

[0055] This embodiment plans to construct a tack coat and an SMA-13 ​​top coat on the AC-20 lower layer; the aggregate gradation in the AC-20 lower layer mixture is shown in Table 1, with an asphalt-aggregate ratio of 4.3%; the tack coat uses SBS modified emulsified asphalt at a dosage of 1.0 kg / m³. 2 In this embodiment, the tack coat does not use a crushed stone seal; the aggregate gradation in the SMA-13 ​​surface layer mixture is shown in Table 2, with an asphalt-aggregate ratio of 6.2%; the planned site compaction method is to use an XCMG XS335 roller with a front wheel mass of 22,500 kg, compacting 5 times, with a paving temperature of 135℃, an initial compaction temperature of not less than 130℃, and secondary and final compaction temperatures of not less than 80℃; the planned site compaction work is 3980 J.

[0056] Table 1 Aggregate gradation in the lower layer mixture of AC-20

[0057]

[0058] Table 2 Aggregate gradation in SMA-13 ​​upper layer mixture

[0059]

[0060] Step 2: Establish the in-situ torsional shear strength-field compaction work fitting curve: Select a 60m long test section on site and divide it into 6 smaller sections, each 10m long. For each smaller test section, pave the provided SBS modified emulsified asphalt tack coat and SMA-13 ​​surface layer. Record the initial height of the surface layer as 0.05m using a ruler (the surface layer height refers to the thickness of the tack coat and surface layer after paving). Compact each smaller test section 1, 2, ... until the in-situ torsional shear strength (data obtained after compaction and cooling to 25℃) increases by less than 1kPa with increasing compaction frequency (i.e., approaches saturation); record the height after compaction using a ruler. The first small test section was compacted once, and the compacted height was 0.043m. The on-site compaction energy was calculated as 22500kg × 9.8 × (0.05 - 0.043) = 1543.5J. After cooling to 25℃, an in-situ torsional shear test was conducted on the first small test section (referring to the interlayer bond strength test method (T 0985-2019) in "JTG 3450-2019 Highway Subgrade and Pavement Field Test Specification"). The in-situ torsional shear strength was obtained as 520kPa, and the data was recorded. Similarly, the operation was repeated to obtain multiple sets of data, as detailed in Table 3. In this embodiment, after the sixth compaction, the on-site compaction energy reached 4410J, and the in-situ torsional shear strength reached 576kPa, with a difference of less than 1kPa compared to the fifth compaction. Based on the data in Table 1, a quadratic polynomial fitting was used to plot the in-situ torsional shear strength - on-site compaction energy fitting curve (curve A), as shown below. Figure 1 As shown, curve A is obtained. R 2 =0.99, This refers to the in-situ torsional shear strength. This is to ensure the material is compacted on-site.

[0061] Table 3 Height, on-site compaction work, and in-situ torsional shear strength of the small test section after multiple compactions

[0062]

[0063] Step 3: Establish the fitting curve of in-situ torsional shear strength - on-site compaction work:

[0064] On the same site and under the same substructure, a 1m×1m area was selected. An SBS modified emulsified asphalt tack coat was applied according to the aforementioned construction parameters. Multiple standard Marshall specimens (using the same raw material as the surface layer, SMA-13) were placed on the tack coat. During the rolling process in step two, at the same initial compaction temperature of 130℃, each specimen was hammered 50, 100, 150, 200, 220, 240, 250, 260, and 270 times respectively from a height of 0.457m using a standard 4.536kg hammer. After cooling to 25℃, each specimen underwent in-situ torsional shear tests to obtain its corresponding in-situ torsional shear strength, until the difference in in-situ torsional shear strength increase was less than 1kPa. The in-situ torsional shear strength of the specimens under different hammer blow counts is shown in Table 4. In this embodiment, the in-situ torsional shear strength reached approximately 576kPa after 260 hammer blows. Then, the number of hammer blows is converted into on-site compaction work using the formula for total on-site compaction work. The resulting data is plotted as a fitting curve of in-situ torsional shear strength versus on-site compaction work (curve B). Figure 1 Curve B is R 2 =0.97, where This refers to the in-situ torsional shear strength. To ensure the effectiveness of the on-site investigation.

[0065] Table 4 In-situ torsional shear strength of specimens under different hammer blows

[0066]

[0067] Step 4: Compare curves A and B to obtain the corresponding in-situ compaction work and in-situ impact compaction work under the same in-situ torsional shear strength. Table 5 schematically lists multiple sets of in-situ compaction work and in-situ impact compaction work data under the same in-situ torsional shear strength. Take multiple sets of data and fit them to obtain the conversion curve between in-situ compaction work and in-situ impact compaction work (in-situ compaction work - in-situ impact compaction work fitting curve, curve C), as shown below. Figure 2 As shown, the formula obtained by fitting in this embodiment is: R 2 =0.99; where, To ensure on-site compaction, To ensure the effectiveness of the on-site investigation.

[0068] Table 5 Examples of some in-situ torsional shear strengths and their corresponding in-situ compaction and impact work data

[0069]

[0070] Step 5, Target Section Strength Prediction: Using the established curve C, the planned on-site compaction energy of 3980J is converted into the required on-site compaction energy of 4680J. On the substructure at this location, a tack coat is applied according to the parameters, and then an SMA-13 ​​Marshall standard specimen is placed. The converted on-site compaction energy of 4680J is applied to the standard specimen using a compaction instrument (converted to the number of hammer blows N=4680 / 20.33=230.375, approximately 231 blows). Subsequently, an in-situ torsional shear test is immediately conducted at the same temperature as rolling (130℃). After cooling to 25℃, the measured in-situ torsional shear strength is 576kPa.

[0071] In this embodiment, after the surface layer was constructed as planned on the test section, the measured in-situ torsional shear strength F was 551.2 kPa. Through error calculation, the absolute error between the predicted and actual values ​​using this method was 24.8 kPa, and the relative error = (absolute error / actual value) × 100% = 24.8 / 551.2 ≈ 4.5%, which meets the allowable range of 5% for on-site engineering errors. This proves that the detection method of this application can be used for actual prediction of the in-situ torsional shear strength of the surface layer.

[0072] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method of detecting the state of an asphalt pavement layer interface, characterized by, Includes the following steps: Step 1: Determine the construction parameters and on-site compaction work for the target road section; Step 2: Select several small test sections on site, apply the tack coat and crushed stone seal coat according to the construction parameters in Step 1, lay the upper structural material and measure the initial height of the upper structure; use a standard roller to compact each test section in different passes, measure the height of the upper structure after compaction, and simultaneously conduct in-situ torsional shear tests to obtain the corresponding in-situ torsional shear strength values ​​and calculate the on-site compaction work, and fit the in-situ torsional shear strength-on-site compaction work fitting curve, denoted as curve A; Step 3: Apply the tack coat and crushed stone seal layer to each small test section according to the above construction parameters, and place standard specimens with the same material as the upper structure on the crushed stone seal layer; at the same temperature as in Step 2, apply different numbers of hammer blows to the standard specimens using a compactor to simulate the on-site compaction work; after the hammering is completed, conduct an in-situ torsional shear test to obtain the in-situ torsional shear strength; fit the in-situ torsional shear strength-on-site compaction work fitting curve, denoted as curve B; Step 4: Compare curve A and curve B, take several sets of in-situ compaction work and in-situ impact work under the same in-situ torsional shear strength value, and fit the conversion curve between in-situ compaction work and in-situ impact work, which is denoted as curve C. Step 5: Target Section Strength Prediction: For the planned construction location, determine its on-site construction parameters and target on-site compaction work, and obtain the target on-site compaction work based on the curve C. Then, apply the tack coat and chip seal coat according to the on-site construction parameters and place standard specimens on them. Apply the converted on-site compaction work to the standard specimens using a compaction instrument, and then immediately conduct an in-situ torsional shear test. The measured in-situ torsional shear strength is the predicted value of the interlayer in-situ torsional shear strength that can be achieved after the upper structure is actually paved and compacted. For the construction of the tack coat on the AC-20 lower layer and the SMA-13 ​​upper layer, with a standard roller front wheel mass of 22,500 kg and 5 compaction cycles; The in-situ torsional shear strength - field compaction work baseline curve is as follows: ； The in-situ torsional shear strength-in-situ compaction work relationship curve is as follows: ； The conversion curve between on-site compaction work and on-site tamping work is as follows: ； In the above formula, is the in-situ torsional shear strength measured at step two, in kPa; is the field compaction work, in J; is the in-situ torsional shear strength measured at step three, in kPa; is the field compaction work, in J.

2. The method for detecting the interlayer condition of asphalt pavement according to claim 1, characterized in that: In step one, the construction parameters include the type and amount of tack coat, the type and amount of crushed stone for the crushed stone seal, and the planned compaction machinery and number of compaction cycles. The on-site compaction work must be within the effective growth range of the interlayer in-situ torsional shear strength and not exceed the critical compaction work corresponding to the saturation of the in-situ torsional shear strength.

3. The method for detecting the interlayer condition of asphalt pavement according to claim 1, characterized in that: Step 2: After compaction, wait for the upper structure to cool to temperature T, and then measure the height of the upper structure after compaction; in Step 3: after hammering, wait for the standard specimen to cool to temperature T, and then conduct an in-situ torsion shear test; temperature T is 25℃.

4. The method for detecting the interlayer condition of asphalt pavement according to claim 1, characterized in that: In step two, in each small test section, the number of compaction cycles of the standard roller is increased sequentially from 1 to less than 1 kPa for the increase in in-situ torsional shear strength with the increase in the number of compaction cycles.

5. The method for detecting the interlayer condition of asphalt pavement according to claim 1, characterized in that: In step three, the number of hammer blows of the compactor starts from 50 and increases sequentially with a difference of 10-50 blows, until the increase in in-situ torsional shear strength with the increase in the number of hammer blows is less than 1 kPa.

6. The method for detecting the interlayer condition of asphalt pavement according to claim 1, characterized in that: In step two, a test road section of 60m-100m in length is selected on site and divided into 6-10 smaller test road sections, each of which is 8-10m long.

7. The method for detecting the interlayer condition of asphalt pavement according to claim 1, characterized in that: In step three, a 1m×1m area is selected in each small test section, and multiple standard Marshall specimens are placed on the tack coat and the gravel seal coat. They are hammered a different number of times, and in-situ torsional shear is performed on each specimen to obtain its corresponding in-situ torsional shear strength.

8. The method for detecting the interlayer condition of asphalt pavement according to claim 1, characterized in that: The fitting in steps two, three, and four is all quadratic polynomial fitting.

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