Railway roadbed moisture content detection method based on ground penetrating radar

Abstract

The invention belongs to the technical field of road structure layer moisture content detection, and aims to solve the problems of incomplete detection range and low detection efficiency due to the fact that most of drilling sampling is random detection. The railroad bed moisture content detection method based on the ground penetrating radar comprises the following steps that a railroad bed to be detected is selected, a detection point is selected every A meters, N detection points are selected in total, and the moisture content of a semi-rigid base layer is detected; carrying out core drilling and sampling to obtain the dielectric constant of the railway bed to be detected, carrying out continuous detection on the railway bed to be detected based on the ground penetrating radar, and carrying out inversion calculation on the dielectric constant of the semi-rigid base layer of the railway bed to obtain the dielectric constant of the semi-rigid base layer of a certain area in the N measuring points; and on the basis of the dielectric constant of the semi-rigid base layer and in combination with a function relation between the dielectric constant of the semi-rigid base layer and the moisture content of the semi-rigid base layer, obtaining a calculated value of the moisture content of the semi-rigid base layer. The moisture content can be rapidly and continuously detected, and the detection range is complete.

Description

Technical Field

[0001] The invention belongs to the technical field of moisture content detection of road structure layers, and in particular relates to a method for detecting moisture content of railway roadbed based on ground penetrating radar. Background Art

[0002] Moisture content is one of the important indicators of road quality control. Its size is closely related to the compaction effect of the road. Too high or too low a moisture content will affect the compaction effect of the road, leading to a series of quality problems and causing related road diseases.

[0003] The filler must be compacted at a moisture content close to the optimum to obtain the maximum dry density, achieve a good compaction effect and ensure the quality of road construction. How to determine the moisture content of the road structure layer has become one of the important tasks of current road quality inspection. Traditional drilling sampling is mostly random testing, with an incomplete detection range and low detection efficiency. Summary of the invention

[0004] In order to solve at least one of the above technical problems existing in the prior art, the present invention provides a method for detecting moisture content of railway subgrade based on ground penetrating radar.

[0005] The present invention is implemented by the following technical solution: a method for detecting moisture content of railway subgrade based on ground penetrating radar, comprising the following steps:

[0006] S1: Select the railway subgrade to be tested, select a measuring point every A meters, select N measuring points in total, and test the moisture content of the semi-rigid base;

[0007] S2: Drill core sampling to obtain the dielectric constant of the railway subgrade to be inspected, conduct continuous inspection of the railway to be inspected based on ground penetrating radar, perform inversion calculation on the dielectric constant of the semi-rigid base of the railway subgrade, and obtain the dielectric constant of the semi-rigid base of a certain area among N measuring points;

[0008] S3: Based on the dielectric constant of the semi-rigid base layer and in combination with the functional relationship between the dielectric constant and the moisture content of the semi-rigid base layer, the calculated value of the moisture content of the semi-rigid base layer in the area is obtained;

[0009] S4: Based on the optimal moisture content given in the design, the moisture content of the semi-rigid base is quickly and continuously detected by ground penetrating radar, providing a basis for the rapid compaction and pressure replenishment of the semi-rigid base.

[0010] Preferably, the functional relationship between the dielectric constant of the semi-rigid base layer and the moisture content of the semi-rigid base layer is as follows:

[0011] α=-0.008642X 3 +0.1968X 2 +0.08254X+6.923

[0012] Where α is the dielectric constant of the semi-rigid base layer, and X is the moisture content of the semi-rigid base layer.

[0013] Preferably, the steps of obtaining the functional relationship between the dielectric constant of the semi-rigid base layer and the moisture content of the semi-rigid base layer are as follows:

[0014] The dielectric constant and moisture content data of different semi-rigid base materials obtained from the test; the dielectric constant is obtained based on ground penetrating radar detection and inversion calculation, and the moisture content is the measured value obtained by on-site sampling;

[0015] Different function forms are used to fit through MATLAB, and the fitting function form with the smallest residual is obtained through comparison. Finally, the cubic polynomial function is selected as the functional relationship to characterize the relationship between the two.

[0016] Based on the functional relationship that characterizes the relationship between the two and the dielectric constant of the semi-rigid base material obtained through ground penetrating radar detection and inversion calculation, the corresponding calculated value of the moisture content of the semi-rigid base is obtained, and compared with the measured value of the moisture content of the semi-rigid base obtained by on-site sampling to ensure that the positive and negative deviations are within the design requirements.

[0017] Preferably, the design requirement for the positive and negative deviations of the measured and calculated values ​​of the moisture content of the semi-rigid base layer is within ±2%.

[0018] Preferably, based on the dielectric constant of the semi-rigid base layer and in combination with the functional relationship between the dielectric constant and the moisture content of the semi-rigid base layer, the premise for obtaining the calculated value of the corresponding moisture content of the semi-rigid base layer is that the moisture content of the semi-rigid base layer is within a stable range.

[0019] Preferably, the value A ranges from 1 to 20 m, the value N ranges from 2 to 100, and the detection frequency of the ground penetrating radar is 900 MHz.

[0020] Preferably, the calculation formula of the dielectric constant of the semi-rigid base layer is:

[0021]

[0022] Where α is the dielectric constant of the semi-rigid base layer, C is the propagation speed of electromagnetic waves in the air; t is the propagation time of the electromagnetic wave of the ground penetrating radar in the semi-rigid base layer, and H is the dielectric thickness of the semi-rigid base layer of the railway subgrade.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention can detect the moisture content quickly and continuously based on the dielectric constant of the semi-rigid base layer calculated by inversion of the ground penetrating radar and the functional relationship between the dielectric constant of the semi-rigid base layer and the moisture content of the semi-rigid base layer, and the detection range is complete; on the premise of clarifying the optimal moisture content, it can provide a basis for the rapid compaction and pressure replenishment of the semi-rigid base layer, thereby alleviating the problem of low road detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0027] In conjunction with the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention. It should be noted that in this specification, relational terms such as first and second are only used to distinguish one entity from several other entities, and do not necessarily require or imply any actual relationship or order between these entities.

[0029] The present invention provides an embodiment:

[0030] like Figure 1 As shown, a method for detecting moisture content of railway subgrade based on ground penetrating radar comprises the following steps:

[0031] S1: Select the railway subgrade to be tested, select a measuring point every A meters, select N measuring points in total, and test the moisture content of the semi-rigid base;

[0032] S2: Drill core sampling to obtain the dielectric constant of the railway subgrade to be inspected, conduct continuous inspection of the railway to be inspected based on ground penetrating radar, perform inversion calculation on the dielectric constant of the semi-rigid base of the railway subgrade, and obtain the dielectric constant of the semi-rigid base of a certain area among N measuring points;

[0033] S3: Based on the dielectric constant of the semi-rigid base layer and in combination with the functional relationship between the dielectric constant and the moisture content of the semi-rigid base layer, the calculated value of the moisture content of the semi-rigid base layer in the area is obtained;

[0034] S4: Based on the optimal moisture content given in the design, the moisture content of the semi-rigid base is quickly and continuously detected by ground penetrating radar, providing a basis for the rapid compaction and pressure replenishment of the semi-rigid base.

[0035] In this embodiment, the value range of value A is 1-20m, and the value range of value N is 2-100. For example, a measuring point is selected every 10m, and a total of 100 measuring points are selected to detect the moisture content. The detection frequency of the ground penetrating radar is 900MHz. In another design of the present invention: the detection of the railway subgrade includes the roadbed, the subgrade surface layer and the subgrade bottom layer. The thickness of each layer is the same as that of the detection section, and the soil type of the subgrade surface layer is the same as that of the detection section.

[0036] The calculation formula for the dielectric constant of the semi-rigid base layer is:

[0037]

[0038] Where α is the dielectric constant of the semi-rigid base layer, C is the propagation speed of electromagnetic waves in the air; t is the propagation time of the electromagnetic wave of the ground penetrating radar in the semi-rigid base layer, and H is the dielectric thickness of the semi-rigid base layer of the railway subgrade.

[0039] The functional relationship between the dielectric constant of the semi-rigid base and the moisture content of the semi-rigid base is as follows:

[0040] α=-0.008642X 3 +0.1968X 2 +0.08254X+6.923

[0041] Where α is the dielectric constant of the semi-rigid base layer, and X is the moisture content of the semi-rigid base layer.

[0042] The above formula is explained as follows:

[0043] The dielectric constant and moisture content data of different semi-rigid base materials are obtained based on the test; the dielectric constant is obtained based on ground penetrating radar detection and inversion calculation, and the moisture content is the measured value obtained by on-site sampling; a trend graph of the relationship between moisture content and dielectric constant is drawn.

[0044] The data were fitted using power functions, trigonometric functions, polynomial functions and other function forms through MATLAB, and the sum variance and correlation coefficient were used as reference standards for comparison to obtain a better fitting function form. Finally, the cubic polynomial function form was selected. With a 95% confidence interval, the sum variance was 0.03657, the correlation coefficient was 0.9997, the sum variance was small, the fitting coefficient was close to 1, and the fitting effect was good.

[0045] Based on the cubic polynomial function relationship that characterizes the relationship between the two and the dielectric constant of the semi-rigid base material obtained by ground penetrating radar detection and inversion calculation, the corresponding calculated value of the moisture content of the semi-rigid base is obtained and compared with the measured value of the moisture content of the semi-rigid base obtained by on-site sampling to ensure that the positive and negative deviations are within the design requirements.

[0046] In this embodiment, the design requirement for the positive and negative deviations of the measured value and the calculated value of the moisture content of the semi-rigid base layer is within ±2%.

[0047] Based on the dielectric constant of the semi-rigid base and the functional relationship between it and the moisture content of the semi-rigid base, the premise for obtaining the corresponding calculated value of the moisture content of the semi-rigid base is that the moisture content of the semi-rigid base is within a stable range, otherwise it is easy to cause a large deviation between the calculated value of the moisture content of the semi-rigid base and the measured value. The stable range of the moisture content of the semi-rigid base is generally 12%-24%.

[0048] The present invention can rapidly and continuously detect moisture content with a complete detection range; on the premise of clarifying the optimal moisture content, it can provide a basis for rapid compaction and pressure supplementation of a semi-rigid base layer, thereby alleviating the problem of low road detection efficiency.

[0049] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for detecting moisture content of railway subgrade based on ground penetrating radar, characterized in that: The following steps are involved: S1: Select the railway subgrade to be tested, select a measuring point every A meters, select N measuring points in total, and test the moisture content of the semi-rigid base; S2: Drill core sampling to obtain the dielectric constant of the railway subgrade to be inspected, conduct continuous inspection of the railway to be inspected based on ground penetrating radar, perform inversion calculation on the dielectric constant of the semi-rigid base of the railway subgrade, and obtain the dielectric constant of the semi-rigid base of a certain area among N measuring points; S3: Based on the dielectric constant of the semi-rigid base layer and in combination with the functional relationship between the dielectric constant and the moisture content of the semi-rigid base layer, the calculated value of the moisture content of the semi-rigid base layer in the area is obtained; S4: Based on the optimal moisture content given in the design, the moisture content of the semi-rigid base is quickly and continuously detected by ground penetrating radar, providing a basis for the rapid compaction and pressure replenishment of the semi-rigid base.

2. The method for detecting moisture content of railway subgrade based on ground penetrating radar according to claim 1, characterized in that: The functional relationship between the dielectric constant of the semi-rigid base and the moisture content of the semi-rigid base is as follows: α=-0.008642X 3 +0.1968X 2 +0.08254X+6.923 Where α is the dielectric constant of the semi-rigid base layer, and X is the moisture content of the semi-rigid base layer.

3. The method for detecting moisture content of railway subgrade based on ground penetrating radar according to claim 2, characterized in that: The steps to obtain the functional relationship between the dielectric constant of the semi-rigid base and the moisture content of the semi-rigid base are as follows: The dielectric constant and moisture content data of different semi-rigid base materials obtained from the test; the dielectric constant is obtained based on ground penetrating radar detection and inversion calculation, and the moisture content is the measured value obtained by on-site sampling; Through MATLAB, different function forms are used for fitting, and the fitting function form with the smallest residual is obtained by comparison. Finally, the cubic polynomial function is selected as the functional relationship to characterize the relationship between the two. Based on the functional relationship that characterizes the relationship between the two and the dielectric constant of the semi-rigid base material obtained through ground penetrating radar detection and inversion calculation, the corresponding calculated value of the moisture content of the semi-rigid base is obtained, and compared with the measured value of the moisture content of the semi-rigid base obtained by on-site sampling, so that the positive and negative deviations of the measured and calculated values ​​of the moisture content of the semi-rigid base meet the design requirements.

4. The method for detecting moisture content of railway subgrade based on ground penetrating radar according to claim 3, characterized in that: The design requirement for the positive and negative deviations between the measured and calculated values ​​of the moisture content of the semi-rigid base layer is within ±2%.

5. The method for detecting moisture content of railway subgrade based on ground penetrating radar according to claim 1, characterized in that: Based on the dielectric constant of the semi-rigid base layer and in combination with the functional relationship between the dielectric constant and the moisture content of the semi-rigid base layer, the premise for obtaining the calculated value of the corresponding moisture content of the semi-rigid base layer is that the moisture content of the semi-rigid base layer is within a stable range.

6. The method for detecting moisture content of railway subgrade based on ground penetrating radar according to claim 1, characterized in that: The value range of A is 1-20m, the value range of N is 2-100, and the detection frequency of the ground penetrating radar is 900MHz.

7. The method for detecting moisture content of railway subgrade based on ground penetrating radar according to claim 1, characterized in that: The calculation formula for the dielectric constant of the semi-rigid base layer is: Where α is the dielectric constant of the semi-rigid base layer, C is the propagation speed of electromagnetic waves in the air; t is the propagation time of the electromagnetic wave of the ground penetrating radar in the semi-rigid base layer, and H is the dielectric thickness of the semi-rigid base layer of the railway subgrade.

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