A method for evaluating the structural bearing capacity of cement concrete panels

Abstract

A method for evaluating the structural bearing capacity of cement concrete panels relates to the field of road engineering technology. The evaluation method comprises the following steps: calculating the modulus ratio of a typical cement slab in a cement concrete road section to be tested, where the modulus ratio is the ratio of the current elastic modulus of the cement concrete surface layer to the initial elastic modulus; calculating the deflection basin area ratio of each cement slab in the cement concrete road section to be tested, where the deflection basin area ratio is the ratio of the current deflection basin area of ​​the cement concrete surface layer to the initial deflection basin area; establishing a correspondence between the deflection basin area ratio and the modulus ratio of the cement concrete surface layer of a typical cement slab; obtaining an estimated modulus ratio of other cement slabs in the road section through the corresponding relationship; and evaluating the structural bearing capacity of the cement concrete panel using the estimated modulus ratio as an evaluation indicator. The present invention can achieve rapid and comprehensive evaluation based on accurate judgment of the structural bearing capacity of the cement concrete panel, thereby improving the efficiency of evaluating the structural bearing capacity of the panels in the cement concrete road section.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering, and in particular to a method for evaluating the structural bearing capacity of a cement concrete panel. Background Art

[0002] Although my country's highway construction is developing rapidly, the cement concrete pavements built in the early days have suffered varying degrees of damage due to the low original pavement design standards and the rapid growth of heavy traffic volume. It is necessary to conduct structural performance testing and evaluation on them in order to provide a theoretical basis for the transformation of cement pavements into asphalt pavements. The evaluation of the pavement structure bearing capacity is one of the important contents of the pavement structure performance evaluation.

[0003] The structural bearing capacity of cement concrete pavements can be evaluated through both nondestructive and destructive testing. Destructive testing involves removing specimens from the site and conducting a series of tests in an indoor laboratory to determine various parameters to evaluate the structural bearing capacity. However, since destructive testing damages the original pavement, the evaluation results may differ significantly from the actual pavement condition. Nondestructive testing, on the other hand, can detect the structural bearing capacity of the pavement without damaging it and provide a corresponding evaluation.

[0004] Currently, nondestructive testing of the bearing capacity of cement concrete pavement structures primarily involves evaluating deflection values. For example, Chinese invention patent CN114169190A provides a method for evaluating the bearing capacity of subgrade and pavement structures based on the high-speed deflection basin indicator. Using finite element simulation, different subgrade and pavement structural parameters are set to simulate three deflection morphological indicators for various structural parameter combinations, thereby constructing a surface deflection indicator database. Based on this database, a neural network is trained using the three deflection morphological indicators for various structural parameter combinations as inputs and various subgrade and pavement structural parameters as outputs. Based on the measured deflection data at each point, the three deflection morphological indicators are calculated and input into the neural network to obtain various subgrade and pavement structural parameters, which are then used to evaluate the bearing capacity of the subgrade and pavement structure. However, deflection, as a comprehensive indicator, often reflects the bearing capacity of the entire pavement structure and may not accurately evaluate the structural bearing capacity of the cement concrete surface layer.

[0005] Surface wave spectrum analysis, a novel nondestructive testing method, collects the time-domain surface wave signals generated by striking the road surface under test. Using spectrum analysis, it inverts the elastic modulus of each pavement layer, thereby evaluating the bearing capacity of cement concrete panels. While laboratory tests and comparisons with other testing methods have shown good accuracy, this method suffers from low detection and post-processing efficiency, making it unsuitable for direct application in large-scale highway testing.

[0006] Therefore, there is an urgent need for a method that can quickly and accurately determine the structural bearing capacity of the cement concrete surface layer so that it can be widely used in highway cement concrete pavement inspection. Summary of the Invention

[0007] In order to reliably detect the structural bearing capacity of large-scale highway cement concrete panels, the present invention provides a method for evaluating the structural bearing capacity of cement concrete panels.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] Step S1: Detecting surface wave time domain signals at typical cement slab rutting locations and road shoulders of the cement concrete road section to be inspected using surface wave spectrum analysis;

[0010] Step S2: using a drop weight deflectometer to measure the deflection value of each cement slab at the rut and shoulder of the cement concrete road section to be tested;

[0011] Step S3: inverting the current elastic modulus E of the typical cement slab rutting location and the initial elastic modulus E0 of the shoulder, and calculating the modulus ratio E / E0 of the cement concrete surface layer;

[0012] Step S4: using the deflection basin area formula to calculate the current deflection basin area A at the typical cement slab rut and the initial deflection basin area A0 at the shoulder, and calculating the deflection basin area ratio A / A0;

[0013] Step S5: establishing a corresponding relationship between the structural bearing capacity evaluation indices of the two cement concrete panels based on the cement concrete surface modulus ratio E / E0 obtained in step S3 and the deflection basin area ratio A / A0 obtained in step S4, and constructing a cement concrete panel structural bearing capacity evaluation model;

[0014] Step S6: Evaluate the structural bearing capacity of other cement slabs in the road section using the structural bearing capacity assessment model, that is, obtain the estimated modulus ratio of other cement slabs in the tested road section based on the deflection basin area ratio A / A0 of other cement slabs in the tested road section and the corresponding relationship established in step S5;

[0015] Step S7: performing graded assessment on the structural bearing capacity of the cement concrete panel.

[0016] Typical cement boards are identified by the degree of structural damage on the surface of the cement board.

[0017] Among the typical degrees of structural damage on the surface of cement boards: minor can be considered as no structural damage on the surface of the cement board, that is, there is only functional damage such as exposed bones, surface peeling, etc., or the cement board is intact and can also be classified as minor surface structural damage.

[0018] Typical structural damage level of cement board surface is medium: Medium can be considered as at least one through crack on the cement board surface.

[0019] Typical structural damage levels on cement board surfaces: Severe damage can be considered as at least two through-going cracks on the cement board surface.

[0020] Among the typical structural damage levels on the surface of cement boards, obvious cracks are cracks that can be directly observed by the naked eye.

[0021] Typical cement slabs are selected based on the overall surface structural damage of the cement concrete road section, with at least one slab of each type being mild, moderate, or severe. If a slab of a particular structural damage level is unavailable, one slab of the other damage level will be added for each slab type missing.

[0022] Determine the specific location for surface wave testing on a typical cement slab, i.e., the center of the line connecting the two displacement sensors in the surface wave testing equipment. This location is determined both along the roadway and perpendicular to it. The location along the roadway follows the following principles: If the cement slab is intact, the surface wave testing location is at the center of the slab along the roadway. If the slab has surface structural defects such as a break or crack, the surface wave testing location is at the center of the largest break along the roadway.

[0023] The position perpendicular to the direction of the driving lane is determined according to the following principles: in the rutting direction of a typical cement slab and at the center of the shoulder perpendicular to the direction of the driving lane.

[0024] Surface wave detection is performed at each position of a typical cement slab in both the direction along the lane and perpendicular to the lane. Surface wave detection is only performed along the lane at the shoulder. That is, surface wave detection is required at two locations for each typical cement slab.

[0025] If there are no ruts on the cement slab, the surface wave spectrum analysis test is performed at the driving track.

[0026] If there is no shoulder on the cement slab, the spectrum analysis of the surface wave should be carried out at a location not on the driving track.

[0027] The deflection value of each cement slab of the cement concrete road section to be tested is detected by a drop weight deflectometer, and the drop weight deflectometer can detect the deflection values ​​of 9 measuring points.

[0028] The drop weight deflectometer can detect the deflection values ​​of 9 measuring points, which are 0mm, 100mm, 200mm, 300mm, 600mm, 900mm, 1200mm, 1500mm and 1800mm respectively.

[0029] The specific position of the drop weight deflectometer load disk of each cement slab is consistent with the surface wave detection position.

[0030] If there are no ruts on the cement slab, the deflection test using a drop weight deflectometer should be carried out at the driving track.

[0031] If there is no shoulder on the cement slab, the deflection test using a drop weight deflectometer should be carried out at a location not on the driving track.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The technical solution provided by the present invention uses two non-destructive testing methods, a drop weight deflectometer and surface wave spectrum analysis, to collaboratively obtain an estimated modulus ratio of the cement slab of the evaluation section to evaluate the structural bearing capacity of the cement concrete panel of the section. This solves the problem that the existing deflection evaluation method cannot quickly determine the structural bearing capacity of the cement concrete panel, reduces the investigation cost required for the structural bearing capacity evaluation, and the evaluation method is highly feasible and simple to operate, which can improve detection efficiency and evaluation reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Those skilled in the art will have a clear understanding of this by reading the detailed description of the preferred embodiment below. The accompanying drawings are only used to illustrate the preferred embodiment and are not intended to limit the present invention.

[0035] Figure 1 A schematic flow chart of a method for evaluating the bearing capacity of a cement concrete panel structure according to an embodiment of the present invention.

[0036] Figure 2 Graph showing the logarithmic relationship between MR and AR according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be further described below through specific implementation methods in conjunction with the accompanying drawings.

[0038] Preferred embodiment one:

[0039] This preferred embodiment provides a method for evaluating the bearing capacity of a cement concrete panel structure. Figure 1 As shown, the evaluation method specifically includes the following steps:

[0040] The surface wave spectrum analysis is used to non-destructively detect the surface wave time domain signals at the typical cement slab rutting and shoulder locations of the cement concrete road section to be inspected.

[0041] The specific steps are as follows: First, select typical cement slabs, that is, select at least one cement slab of each of the three different levels of structural damage, namely, mild, moderate, and severe, based on the overall surface structural damage of the cement concrete section. If a cement slab of a certain level of structural damage is not available, then for each type of damage level missing, one cement slab of the other damage level will be added;

[0042] This step is specifically as follows: Then determine the specific position of the typical cement slab for surface wave detection, that is, the center of the line connecting the two displacement sensors in the surface wave detection equipment. The position is determined in two directions: along the driving lane and perpendicular to the driving lane. Among them, the determination of the position along the driving lane direction complies with the following principles: if the cement slab is intact, the surface wave detection position is at the center of the cement slab along the driving lane direction; if the cement slab has surface structural defects such as broken slabs or cracks, the surface wave detection position is at the center of the broken slab with the largest area along the driving lane direction. The determination of the position perpendicular to the driving lane direction complies with the following principles: in the rutting direction of the typical cement slab and at the center of the shoulder perpendicular to the driving lane direction, that is, each typical cement slab needs to be tested for surface waves at two locations.

[0043] The specific steps are as follows: Finally, surface wave detection is performed on the ruts of a typical cement slab in both the lane direction and the direction perpendicular to the lane, and surface wave detection is performed only along the lane direction on the shoulder.

[0044] Use the drop weight deflectometer to non-destructively test the deflection value of each cement slab at the rut and shoulder of the cement concrete road section to be tested;

[0045] The specific steps are as follows: Deflection testing is required for each concrete slab along the road section to be tested; there is no need to select representative concrete slabs individually. First, the specific position of the drop weight deflectometer load disk for each concrete slab is determined, coinciding with the position of the surface wave test. Deflection testing is performed at two locations on each concrete slab.

[0046] The specific step is as follows: Then, the deflection detection is performed only along the lane direction at each position of each cement slab in the road section to be detected.

[0047] Inversely calculate the current elastic modulus E of a typical cement slab rutting site and the initial elastic modulus E0 of the shoulder, and calculate the modulus ratio E / E0 of the cement concrete surface layer;

[0048] The specific steps are as follows: first, inverse the current elastic modulus E at the typical cement slab rutting location and the initial elastic modulus E0 at the shoulder;

[0049] The specific steps are as follows: Then, calculate the modulus ratio E / E0 of the cement concrete surface layer. The specific expression is as follows:

[0050]

[0051] Wherein, MR is the modulus ratio, which characterizes the residual structural bearing capacity of cement concrete pavement; E is the elastic modulus value of the investigated cement slab at the driving position; E0 is the elastic modulus value of the investigated cement slab at the non-driving position or shoulder (same material and structure).

[0052] Use the deflection basin area formula to calculate the current deflection basin area A at a typical cement slab rut and the initial deflection basin area A0 at the shoulder, and calculate the deflection basin area ratio A / A0;

[0053] The steps are as follows: first, the current deflection basin area A at the typical cement slab rut and the initial deflection basin area A0 at the shoulder are calculated using the deflection basin area formula;

[0054] The formula for the deflection basin area is as follows:

[0055]

[0056] Where D0 is the deflection measurement value at a radius of 0 mm from the load plate or load center; D1 is the deflection measurement value at a radius of 300 mm from the load plate or load center; D2 is the deflection measurement value at a radius of 600 mm from the load plate or load center; and D3 is the deflection measurement value at a radius of 900 mm from the load plate or load center.

[0057] The specific steps are as follows: Then, the deflection basin area ratio A / A0 is calculated, and the specific expression is as follows;

[0058]

[0059] Where AR is the deflection basin area ratio, which represents the residual structural bearing capacity of the cement concrete panel; A is the deflection basin area value of the investigated cement slab at the driving position; and A0 is the deflection basin area value of the investigated cement slab at the non-driving position or road shoulder (with the same material and structure).

[0060] like Figure 2 As shown in the exponential model in , the corresponding relationship between the two structural bearing capacity evaluation indicators of cement concrete panels is established by obtaining the typical cement concrete surface modulus ratio E / E0 and the deflection basin area ratio A / A0, and a cement concrete panel structural bearing capacity condition assessment model is constructed.

[0061] The structural bearing capacity assessment model is used to evaluate the structural bearing capacity of other cement slabs in the road section. That is, the estimated modulus ratio of other cement concrete panels in the test section is obtained by calculating the area ratio A / A0 of other cement slabs in the test section and the established correspondence between the modulus ratio and the deflection basin area ratio.

[0062] The estimated modulus ratio was used as an evaluation indicator to grade the structural bearing capacity of the panels. Based on a large amount of field data and a comparative analysis with the pavement structure strength index, an evaluation indicator of the structural bearing capacity of cement concrete panels based on drop weight deflectometer test data in the "Highway Technical Condition Assessment Standard JTG 5210-2018", the grading standard for the estimated modulus ratio was determined, as shown in Table 1.

[0063] Table 1 Evaluation and classification standards for the bearing capacity of cement concrete panel structures

[0064]

[0065] In order to better explain this embodiment, the following examples are given:

[0066] Four road sections in Jiaxing, Zhejiang and Fengxian, Shanghai were selected, and the pavement structure types are shown in Table 2.

[0067] Table 2 Pavement structure (Jiaxing, Zhejiang and Fengxian, Shanghai)

[0068]

[0069] According to the typical cement slab selection principles, the typical cement slab type and number of slabs for each road section were determined, as shown in Table 3. Surface wave spectrum analysis was used to non-destructively detect surface wave time domain signals at the rutting and shoulder locations of typical cement slabs on four sections of cement concrete pavement in Jiaxing, Zhejiang and Fengxian, Shanghai.

[0070] Table 3 Typical number of cement slabs in each road section (Jiaxing, Zhejiang and Fengxian, Shanghai)

[0071]

[0072]

[0073] The deflection values ​​of each cement slab at the rutting and shoulder locations of four sections of cement concrete pavement in Jiaxing, Zhejiang and Fengxian, Shanghai were measured non-destructively using a drop weight deflectometer.

[0074] The current elastic modulus E at the rutting position of typical cement slabs and the initial elastic modulus E0 at the shoulder of four sections of cement concrete pavement in Jiaxing, Zhejiang and Fengxian, Shanghai were inverted, and the modulus ratio E / E0 of the cement concrete surface layer was calculated. The results are summarized in Table 4.

[0075] Table 4 Summary of AR and MR

[0076]

[0077] The deflection basin area formula was used to calculate the current deflection basin area A at the rutting position of a typical cement slab and the initial deflection basin area A0 at the shoulder of four sections of cement concrete pavement in Jiaxing, Zhejiang and Fengxian, Shanghai. The deflection basin area ratio A / A0 was also calculated. The results are summarized in Table 4.

[0078] See also Figure 2 , based on the cement concrete surface modulus ratio E / E0 and the obtained area ratio A / A0 of the typical cement concrete slabs of the four sections of cement concrete pavement in Jiaxing, Zhejiang and Fengxian, Shanghai, the corresponding relationship between the two evaluation indicators for the structural bearing capacity of cement concrete panels is established, such as Figure 2 As shown, it can be seen that there is a good logarithmic relationship between MR and AR.

[0079] The estimated modulus ratio of the corresponding cement slab was obtained by the corresponding relationship between the deflection basin area ratio A / A0 of other cement slabs in the four sections of cement concrete pavement in Jiaxing, Zhejiang and Fengxian, Shanghai and the established MR and AR.

[0080] Preferred embodiment 2:

[0081] This preferred embodiment provides a method and process for evaluating the structural bearing capacity of cement concrete panels. This evaluation method and process is basically the same as the method of preferred embodiment 1, specifically: calculating the modulus ratio of a typical cement slab on the cement concrete pavement to be tested, where the modulus ratio is the ratio of the current elastic modulus of the cement concrete surface layer to the initial elastic modulus; calculating the deflection basin area ratio of each cement slab on the cement concrete pavement to be tested, where the deflection basin area ratio is the ratio of the current deflection basin area of ​​the cement concrete surface layer to the initial deflection basin area; establishing a correspondence between the deflection basin area ratio and the modulus ratio of the cement concrete surface layer of a typical cement slab, and constructing a cement concrete panel structural bearing capacity evaluation model; evaluating the structural bearing capacity of other cement slabs on the road section through the structural bearing capacity evaluation model, that is, obtaining the estimated modulus ratios of other cement slabs on the road section through the correspondence; and performing a graded assessment of the structural bearing capacity of cement concrete panels.

[0082] The difference is that in the first preferred embodiment, the modulus ratio and deflection basin area ratio of the tested cement concrete surface layer are calculated using the rutting and shoulder locations of the cement slab. If the cement concrete pavement is rutting-free, surface wave spectrum analysis and deflection testing are performed at the vehicle track. If the cement concrete pavement is of a lower grade and lacks a shoulder, or the shoulder surface structure differs from the roadway, surface wave spectrum analysis and deflection testing are performed at locations outside the vehicle track if the cement slab lacks a shoulder.

[0083] Finally, it should be noted that the above embodiments, described in conjunction with the accompanying drawings, are merely preferred solutions for implementing the present invention and are not intended to limit the present invention. Any modifications to the specific embodiments of the present invention or equivalent replacements of some of the technical features, without departing from the spirit of the present invention, are intended to be encompassed within the scope of the technical solution claimed for protection. The scope of protection of the present invention also encompasses any alternative technical solutions that can be conceived by those skilled in the art without inventive effort.

Claims

1. A method for evaluating the structural bearing capacity of a cement concrete panel, characterized in that: The evaluation method is as follows: calculate the modulus ratio of typical cement slabs in the cement concrete section to be detected. The modulus ratio is the ratio of the current elastic modulus of the cement concrete surface layer to the initial elastic modulus. Calculate the ratio of the deflection basin area of each cement slab in the cement concrete section to be detected. The ratio of the deflection basin area is the ratio of the current deflection basin area of the cement concrete slab to the initial deflection basin area. Establish the corresponding relationship between the ratio of the deflection basin area of the cement concrete slab of the typical cement slab and the modulus ratio, and construct an evaluation model for the structural bearing capacity status of the cement concrete slab. Evaluate the structural bearing capacity status of other cement slabs in this section through this structural bearing capacity status evaluation model. Conduct a grading assessment on the structural bearing capacity status of the slab. The specific steps of the evaluation method are as follows: Step S1: Use the non-destructive method of spectral analysis of surface waves to detect the surface wave time-domain signals at the rutting and shoulder positions of the typical cement slabs in the cement concrete section to be detected. This step is specifically as follows: First, select typical cement slabs, that is, select at least one cement slab of each of the three different degrees of slight, moderate, and severe according to the overall surface structural damage status of the cement concrete section. If there is no cement slab of a certain degree of structural damage, for each type of damaged cement slab that is missing, one more cement slab of other damaged degrees will be added. Finally, surface wave detection is carried out in two directions along the lane direction and perpendicular to the lane at the rutting of the typical cement slab, and surface wave detection is only carried out along the lane direction at the shoulder. Step S2: Use the falling weight deflectometer non-destructive method to detect the deflection values at the rutting and shoulder positions of each cement slab in the cement concrete section to be detected. Step S3: Invert the current elastic modulus E at the rutting of the typical cement slab and the initial elastic modulus E0 at the shoulder in Step S1, and calculate the modulus ratio E / E0 of the cement concrete surface layer. Step S4: Use the deflection basin area formula to calculate the current deflection basin area A at the rutting of the typical cement slab and the initial deflection basin area A0 at the shoulder, and calculate the area ratio A / A0. Step S5: Establish the corresponding relationship between the modulus ratio E / E0 of the cement concrete surface layer obtained in Step S2 and the area ratio A / A0 obtained in Step S4 to construct two evaluation indexes for the structural bearing capacity of the cement concrete slab, and construct an evaluation model for the structural bearing capacity status of the cement concrete slab. Step S6: Evaluate the structural bearing capacity status of other cement slabs in this section through this structural bearing capacity status evaluation model, that is, obtain the estimated modulus ratio x of other cement slabs in this detection section by calculating the area ratio A / A0 of other cement slabs to be detected and the corresponding relationship established in Step S5. Step S7: Conduct a grading assessment on the structural bearing capacity status of the slab. Classify the structural bearing capacity according to the estimated modulus ratio x: excellent (x≥1), medium (0.8<x<1), poor (x≤0.8). When there is no rut on the cement concrete pavement, then select to conduct spectral analysis detection and deflection detection of surface waves at the driving track. If there is no shoulder on the cement slab, then select to conduct spectral analysis detection and deflection detection of surface waves at a non-driving track.

2. The method for evaluating the structural bearing capacity of a cement concrete panel according to claim 1, wherein: In step S2, the deflection value of each cement slab in the cement concrete road section to be tested is detected by a drop weight deflectometer, and the drop weight deflectometer can detect the deflection values ​​of 9 measuring points; the positions of the deflection values ​​of the 9 measuring points that the drop weight deflectometer can detect are 0mm, 100mm, 200mm, 300mm, 600mm, 900mm, 1200mm, 1500mm and 1800mm respectively; the specific position of the drop weight deflectometer load disk of each cement slab is consistent with the surface wave detection position, and each cement slab needs to be tested for deflection at two locations; the deflection test is only performed along the lane direction at each position of each cement slab in the road section to be tested.

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