Rapid nondestructive in-situ detection equipment and method for global multi-layer compaction degree of roadbed

Abstract

The invention relates to the technical field of lime soil roadbed compactness detection, in particular to rapid nondestructive in-situ detection equipment and method for the global multilayer compactness of a roadbed. Through simple on-site calibration based on a gold standard point, an accurate impedance compactness model can be quickly established, the compactness value is obtained by directly measuring the impedance of a point to be detected, and the detection result can be quickly obtained by comparing the compactness value with a qualified control interval, so that the detection efficiency and the detection cost are both considered, and only one destructive calibration point is needed on site; the calibration of the whole impedance compaction degree model can be completed by using the method, time, manpower and cost are greatly saved, the defect that a large number of laboratories are needed for calibration in a traditional method is overcome, damage to the site is greatly reduced, the compaction degree estimated value is given, a qualification control interval calculation method based on current construction condition volatility is further provided, and the method is suitable for popularization and application. And the detection result has guiding significance and better meets the actual demand of engineering quality control.

Description

Technical Field

[0001] This invention relates to the field of compaction degree testing technology for lime-soil subgrade, and in particular to a rapid, non-destructive, in-situ testing device and method for full-area, multi-layer compaction degree testing of subgrade. Background Technology

[0002] When controlling the construction quality of lime-soil subgrade, compaction degree is a key indicator for evaluating its density and bearing capacity. Currently, common compaction degree testing methods mainly include sand cone method, ring cutter method, nuclear density meter method, and core drilling method. Although these methods are widely used in practice, they each still have certain limitations.

[0003] The sand cone method, as a traditional compaction testing method, requires on-site excavation, sand filling, weighing, and calculation, which is time-consuming and difficult to achieve rapid, large-scale testing. The ring cutter method is relatively simple to operate and is mainly used for compaction testing of fine-grained soils, but its sample volume is small and its representativeness is limited, making it unsuitable for frequent and large-scale testing scenarios. The nuclear density meter method has the advantages of being fast and non-destructive, and can obtain compaction data in a short time, but the cost of equipment purchase and maintenance is high. The core drilling method involves drilling core samples for laboratory testing, but it causes significant damage to the roadbed, and the repair work after sampling is cumbersome. In addition, the testing cycle is long and the efficiency is low, which cannot meet the needs of large-area real-time testing during construction.

[0004] Therefore, existing methods for testing the compaction degree of lime-soil subgrade often fail to balance the requirements of testing efficiency and cost, and are unable to meet the needs of large-area and frequent testing. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a rapid, non-destructive, in-situ testing device and method for the full-area, multi-layer compaction degree of roadbeds. This solves the technical problem that existing methods for testing the compaction degree of lime-soil roadbeds often struggle to balance testing efficiency and cost, and are unable to meet the needs of large-area, frequent testing.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a rapid, non-destructive, in-situ detection method for the full-area, multi-layer compaction degree of roadbed, the method comprising the following steps: Construct an initial function model to reflect the relationship between soil resistance and compaction degree; The gold standard point was selected as the representative point from the gray soil roadbed; The average impedance was calculated by measuring the impedance at the gold standard point multiple times. The compaction degree at the gold standard point is measured, and the unknown parameters in the initial function model are calculated based on the compaction degree and average impedance to obtain the impedance compaction degree model, and the qualified control range of compaction degree is set. The impedance of the test point is measured and substituted into the impedance compaction model to obtain the compaction degree of the test point. The result is then compared with the qualified control range to output the test result.

[0007] Preferably, the compaction degree is tested by the sand cone method.

[0008] Preferably, the specific steps for setting the acceptable control range of compaction degree are as follows: Calculate the standard deviation of impedance based on several impedance measurements taken at the gold standard point. A control coefficient is set, which, in combination with the impedance standard deviation, affects the degree of deviation of the upper and lower limits of the qualified control range from the compaction degree at the golden standard point.

[0009] Preferably, the specific steps for obtaining the impedance compaction model are as follows: Different sampling depths were set at the gold standard point; The impedance of the lime-soil subgrade was measured multiple times at different sampling depths to calculate the average impedance at different sampling depths; The unknown parameters in the initial function model are calculated based on the compaction degree and the average impedance at different sampling depths to obtain the impedance compaction degree model at different sampling depths.

[0010] The present invention also provides a rapid, non-destructive, in-situ testing device for the full-area, multi-layer compaction degree of roadbed, comprising: a shell serving as a mounting carrier, a display module for calculating and displaying test results and control buttons for controlling signal input on the shell, a base at the bottom of the shell, and a probe sensor array on the base for contacting the soil and interacting with the display module.

[0011] Preferably, the probe sensor array contains four metal probes arranged in a rectangular pattern, and the base is provided with a slide rail for changing the spacing between the metal probes.

[0012] Preferably, the spacing between the metal probes is in several groups, and they are used to measure the compaction degree of soil at different depths.

[0013] By employing the above technical solution, the present invention provides a rapid, non-destructive, in-situ testing device and method for the full-area, multi-layer compaction degree of roadbeds, which has at least the following beneficial effects: 1. This invention can quickly establish an accurate impedance compaction model through simple on-site calibration based on the gold standard point, and can achieve layered detection at different depths by changing the probe spacing. After obtaining the compaction of the test point, the test result can be obtained by comparing it with the qualified control range. It can intuitively and quickly guide on-site construction quality control and judgment, and effectively solve the problem that traditional methods are difficult to balance detection efficiency and cost.

[0014] 2. This invention requires only one destructive calibration point on site, namely the gold standard point, to complete the calibration of the entire impedance compaction model, which greatly saves time, manpower and cost, overcomes the drawback of traditional methods that require a large number of laboratory calibrations, and greatly reduces the damage to the site.

[0015] 3. This invention not only provides an estimated compaction degree, but also offers a method for calculating the qualified control range based on the fluctuations of current construction conditions, making the test results more instructive and more in line with the actual needs of engineering quality control. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart of the method for rapid, non-destructive, in-situ detection of the full-area multi-layer compaction degree of roadbed according to the present invention; Figure 2 This is a schematic diagram of the detection device of the present invention; Figure 3 This is a schematic diagram of the slide rail of the present invention.

[0017] In the diagram: 1. Outer casing; 2. Display module; 3. Control buttons; 4. Base; 5. Probe sensor array; 6. Metal probe; 7. Slide rail. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This will allow for a full understanding of how the present application uses technical means to solve technical problems and achieve technical effects, and to facilitate its implementation.

[0019] To address the technical problem that existing methods for detecting the compaction degree of lime-soil subgrade often fail to balance efficiency and cost, and thus cannot meet the needs of frequent, large-area testing, this invention provides a rapid, non-destructive, in-situ method for detecting the compaction degree of subgrade across multiple layers. This method enables real-time compaction degree detection over large areas at a relatively low cost. The specific implementation process of this method is described below: First, an initial function model reflecting the relationship between soil impedance and compaction degree needs to be constructed. After extensive experimentation, a linear model was established, and its expression can be represented as: ,in, Indicates the degree of compaction. Indicates impedance, Indicates the slope. This represents the intercept.

[0020] Subsequently, a gold standard point was selected from the lime-soil subgrade as a representative point. Using lime-stabilized soil used in the base course of a certain highway section as the experimental subject, the maximum dry density obtained from the indoor standard compaction test was 1.85 g / cm³. Then, a representative point was selected from a freshly compacted and uniformly leveled area on site as the gold standard point.

[0021] Subsequently, the impedance at the gold standard point can be measured multiple times using methods such as the four-electrode method or equipment such as a soil resistivity meter to calculate the average impedance. During the experiment, the measurements were repeated five times, and the obtained impedance values ​​were recorded as follows: 175... 178 172 177 and 173 The average impedance value was calculated. .

[0022] Subsequently, the compaction degree at the gold standard point can be measured using methods such as the sand cone method. During the experiment, a sample was dug out from the gold standard point, dried, and measured. Its wet density was 2.15 g / cm³, and its moisture content was 16.2%, resulting in a calculated dry density of 1.85 g / cm³. The maximum dry density of this road section is the aforementioned 1.85 g / cm³. Therefore, the true compaction degree at this point is equal to its dry density divided by the maximum dry density, which is the compaction degree at the gold standard point. .

[0023] After obtaining the compaction degree at the gold standard point, the one-to-one correspondence between compaction degree and average impedance can be substituted into the initial function model to calculate the unknown parameters in the initial function model. Since the initial function model we are currently using is a linear model, its slope can be obtained by fitting a large amount of experimental data, or a general slope can be used. Here, we take the general slope of 0.0045 as an example. Therefore, the formula for calculating the intercept is as follows: Thus, the impedance compaction model is obtained: This allows for the calibration of the impedance compaction model using the gold standard points on-site.

[0024] Furthermore, since the impedance of lime-soil subgrades at different depths can also be measured using methods such as the four-electrode method, impedance compaction models at different sampling depths can be further calculated. The specific steps are as follows: First, different sampling depths are set at the gold standard point. Then, the impedance of the lime-soil subgrade is measured multiple times at different sampling depths to calculate the average impedance at different sampling depths. Finally, the unknown parameters in the initial function model can be calculated based on the compaction degree and the average impedance at different sampling depths to obtain the impedance compaction degree model at different sampling depths. The calculation process of the impedance compaction degree model at different sampling depths is basically the same as that of obtaining the impedance compaction degree model above. The only difference is that the impedance of the lime-soil subgrade at the corresponding depth is measured during the impedance measurement process.

[0025] Next, it is necessary to set the acceptable control range of compaction to facilitate the output of subsequent test results. The acceptable control range of compaction can be directly set according to certain rules based on the compaction at the gold standard point. For example, the upper limit value is 1.01 times the compaction and the lower limit value is 0.99 times the compaction.

[0026] However, soil compaction is positively correlated with impedance, and factors such as the construction process of the lime-soil roadbed cause its impedance value to fluctuate within a certain range. Therefore, the range of its qualified control interval should be proportional to the fluctuation range of the impedance value; that is, the more stable the impedance value, the smaller the range of the qualified control interval should be. To make the range of the qualified control interval more reasonable and accurate, a method for dynamically setting the qualified control interval by combining the standard deviation of impedance values ​​measured multiple times is provided here. The specific steps are as follows: First, calculate the impedance standard deviation based on the impedance measured several times at the golden standard point. Based on the impedance values ​​measured multiple times, the impedance standard deviation can be calculated. Then, a control coefficient is preset. This control coefficient, combined with the impedance standard deviation, affects the deviation of the upper and lower limits of the qualified control range from the compaction degree at the golden standard point. For example, if the control coefficient n=2 is set, the upper and lower limits of the qualified control range can then be calculated using the following formula: In the above formula, This indicates the upper limit of the acceptable control range. This indicates the lower limit of the acceptable control range.

[0027] Based on the parameters calculated above, the upper and lower limits of the qualified control interval can be calculated as follows: Therefore, the acceptable control range is .

[0028] Subsequently, the impedance of other test points can be directly measured using methods such as the four-electrode method or equipment such as a soil resistivity tester. For example, if the impedance values ​​of three test points A, B, and C are measured, the compaction degree can be calculated based on the impedance compaction degree model and compared with the qualified control range to output the test results. For example: Measurement point A: Measure impedance Substitute the values ​​into the model to calculate the compaction degree: (i.e., 102.3%) Compared with the acceptable control range, the result can be output and displayed as "acceptable".

[0029] Measurement point B: Measure impedance Substitute the values ​​into the model to calculate the compaction degree: (i.e., 95.5%) Compared with the acceptable control range, the result can be output and displayed as "too low".

[0030] Measurement point C: Measure impedance Substitute the values ​​into the model to calculate the compaction degree: (i.e., 104.5%) Compared with the acceptable control range, the result can be output and displayed as "too high".

[0031] This invention also provides a rapid, non-destructive, in-situ testing device for the full-area, multi-layer compaction degree of a roadbed, comprising: a housing 1 serving as an installation carrier; a display module 2 for calculating and displaying test results and control buttons 3 for inputting control signals on the housing 1; the display module 2 can carry a preset initial function model, thereby calculating the impedance compaction model after measuring the compaction degree and average impedance; a base 4 at the bottom of the housing 1; and a probe sensor array 5 on the base 4 for contacting the soil and interacting with the display module 2. The probe sensor array 5, in conjunction with the display module 2, can perform impedance testing of the soil-cement roadbed based on methods such as the four-electrode method. If the impedance testing is performed using the four-electrode method, the probe sensor array 5 can be configured as four rectangularly distributed metal probes 6, and the base 4 is equipped with a slide rail 7 for changing the spacing between the metal probes 6. Based on the four-electrode method measurement principle, the penetration depth of the current is proportional to the probe spacing; therefore, the spacing between the metal probes 6 can be changed by the slide rail 7 to achieve the desired impedance of the soil-cement roadbed. Impedance measurements at different sampling depths of the subgrade were performed to obtain impedance compaction models at different sampling depths. To facilitate adjustment of the spacing between the metal probes 6, the spacing between the metal probes 6 could be further divided into several groups, which are used to measure the compaction of the soil at different depths. That is, several positioning structures, such as snap-fit ​​and bolt-fixing structures, are set on components such as the slide rail 7 or the base 4 to position each metal probe 6 at several specified spacings. This makes adjustment more convenient when it is necessary to measure the impedance of the lime-soil subgrade at a specified depth. For example, three settings can be set: a, b, and c. In setting a, the spacing between each metal probe 6 is 10cm, corresponding to a detection depth of approximately 10-15cm; in setting c, the spacing between each metal probe 6 is 30cm, corresponding to a detection depth of approximately 30-45cm; and in setting b, the spacing between each metal probe 6 is 20cm, corresponding to a detection depth of approximately 20-30cm. The impedance compaction model calculated in the section on rapid non-destructive testing methods for compaction above is based on the b-set spacing.

[0032] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0033] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Since the above embodiments are substantially similar to the method embodiments, their descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0034] The above embodiments provide a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A rapid non-destructive testing method for the full-area multi-layer compaction degree of roadbed, characterized in that, The method includes the following steps: Construct an initial function model to reflect the relationship between soil resistance and compaction degree; The gold standard point was selected as the representative point from the gray soil roadbed; The average impedance was calculated by measuring the impedance at the gold standard point multiple times. The compaction degree at the gold standard point is measured, and the unknown parameters in the initial function model are calculated based on the compaction degree and average impedance to obtain the impedance compaction degree model, and the qualified control range of compaction degree is set. The impedance of the test point is measured and substituted into the impedance compaction model to obtain the compaction degree of the test point. The result is then compared with the qualified control range to output the test result.

2. The rapid non-destructive testing method for compaction degree according to claim 1, characterized in that, The compaction degree was tested using the sand filling method.

3. The rapid non-destructive testing method for compaction degree according to claim 1, characterized in that, The specific steps for setting the acceptable control range for compaction degree are as follows: Calculate the standard deviation of impedance based on several impedance measurements taken at the gold standard point. A control coefficient is set, which, in combination with the impedance standard deviation, affects the degree of deviation of the upper and lower limits of the qualified control range from the compaction degree at the golden standard point.

4. The rapid non-destructive testing method for compaction degree according to claim 1, characterized in that, The specific steps for obtaining the impedance compaction model are as follows: Different sampling depths were set at the gold standard point; The impedance of the lime-soil subgrade was measured multiple times at different sampling depths to calculate the average impedance at different sampling depths; The unknown parameters in the initial function model are calculated based on the compaction degree and the average impedance at different sampling depths to obtain the impedance compaction degree model at different sampling depths.

5. A rapid, non-destructive, in-situ compaction testing device, used to implement the rapid, non-destructive compaction testing method according to any one of claims 1-4, characterized in that, include: The housing (1) serves as the mounting carrier. The housing (1) is equipped with a display module (2) for calculating and displaying the detection results and a control button (3) for controlling signal input. The bottom of the housing (1) is equipped with a base (4). The base (4) is equipped with a probe sensor array (5) for contacting the soil and interacting with the display module (2).

6. The detection device according to claim 5, characterized in that, The probe sensor array (5) contains four metal probes (6) arranged in a rectangular shape, and the base (4) is provided with a slide rail (7) for changing the spacing between the metal probes (6).

7. The detection device according to claim 6, characterized in that, The spacing between the metal probes (6) is in several groups, and they are used to measure the compaction degree of soil at different depths.

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