A highway subgrade compactness detection device and detection method

Abstract

The application belongs to the technical field of highway engineering detection, and specifically discloses a highway subgrade compactness detection device and a detection method, which comprises a sampling cylinder and a positioning sleeve, a spiral sampling rod for drilling samples is rotationally arranged in the sampling cylinder, the sampling cylinder is movably inserted into the positioning sleeve, an annular insertion plate capable of being inserted into the subgrade is extended downward from the bottom of the positioning sleeve, and the lower surface edge of the positioning sleeve is provided with uniformly distributed insertion rods for fixing the positioning sleeve. Based on the penetration principle of fluid in porous media, the higher the compactness is, the denser the structure is, the narrower and more tortuous the penetration path is, the slower the water penetration speed is, and the longer the time for the sensor to detect the resistance change is. The physical principle is clear and definite, the technical threshold of the operator and the subjectivity of the result interpretation are reduced by recording a simple time parameter and comparing it with a pre-calibration curve, and whether the compactness meets the standard can be directly judged.

Description

Technical Field

[0001] The present invention relates to the technical field of highway engineering detection, and specifically to a device and method for detecting the compaction degree of a highway subgrade. Background Art

[0002] With the rapid development of China's social economy, the highway network has been increasingly improved, and the transportation industry is gradually shifting from large-scale construction to the stage mainly focusing on scientific maintenance. This transformation has put forward higher requirements for the rapid and non-destructive detection technologies and equipment of highway subgrades and pavements. The continuous growth of highway traffic volume has exacerbated the wear and tear of subgrades and pavements, and traditional detection methods are difficult to meet the needs of modern maintenance projects in terms of efficiency, accuracy, and safety. Therefore, the development of new auxiliary detection technologies is of great significance for improving the quality and efficiency of highway maintenance and ensuring operation safety.

[0003] Highway subgrade detection is a key link in the operation and maintenance of highway transportation infrastructure, which directly relates to the safety and service life of roads. In recent years, the improvement of industry standardization level has effectively promoted the standardization of product quality control, laying a solid foundation for the healthy development of the industry.

[0004] However, despite the significant progress made in the industry of highway subgrade auxiliary detection technologies, there are still many challenges at present. The core problem is that obvious shortcoming exist in the existing mainstream detection methods, which restricts their wide application in the field:

[0005] 1. Core cutter method and sand replacement method (destructive detection)

[0006] Although the results of such methods are reliable, the operation processes are cumbersome. It needs to go through multiple steps such as digging pits, sampling, weighing, drying, and calculation. The detection efficiency is extremely low and cannot provide immediate feedback for construction. At the same time, the sampling process seriously damages the subgrade structure, and the representativeness of the sampling points is limited, making it difficult to comprehensively evaluate the compaction uniformity. Human errors are also easily introduced during the sample transfer process. For example, patent application No. CN202510238397.6 discloses a method for detecting the compaction degree of a highway subgrade, which sets up a soil sampling component. While digging pits and taking soil samples, it ensures the regularity of the deep pits, thereby improving the detection accuracy and facilitating the automatic collection and weighing of the excavated soil by the staff.

[0007] 2. Nuclear density gauge method

[0008] Although this method can achieve rapid detection, the radioactive source contained therein brings non-negligible radioactive safety risks. Strict supervision is required during transportation, storage, operation, and scrapping. The cost of the equipment itself and its subsequent maintenance is also very high. In addition, its measurement results are easily affected by soil quality, and the calibration work is complex.

[0009] 3. Intelligent compaction control technology (indirect detection)

[0010] This technology indirectly assesses compaction degree through the dynamic response of the road roller, which is an indirect inference. Its accuracy is affected by various factors such as equipment model, rolling speed and subgrade stiffness. It still needs to rely on traditional methods for calibration and cannot obtain physical samples for further geotechnical testing.

[0011] 4. Other emerging nondestructive testing technologies

[0012] Methods such as ground-penetrating radar and Rayleigh wave method are mostly still in the research stage and generally have problems such as complex equipment, difficulty in data interpretation, and limited ability to distinguish different compaction depths, making it difficult to be widely used on construction sites. For example, application number CN202411835746.4 discloses a method and system for monitoring roadbed compaction based on airborne lidar to achieve intelligent detection of roadbed.

[0013] In summary, there is an urgent need in this field for an innovative technical solution that combines the advantages of high efficiency, safety, and accuracy, and ideally integrates sampling and testing functions. However, in the existing technology, there is no device or method that effectively integrates roadbed sampling with in-situ compaction testing based on the permeability principle. Summary of the Invention

[0014] The technical problem to be solved by this invention is to overcome the existing defects and provide a device and method for detecting the compaction degree of highway subgrade. Based on the principle of fluid permeation in porous media, the higher the compaction degree, the denser the structure, the narrower and more tortuous the permeation path, the slower the water permeation rate, and the longer it takes for the sensor to detect the change in resistance. This physical principle is clear and explicit. By recording simple time parameters and comparing them with a pre-calibrated curve, it is possible to intuitively determine whether the compaction degree meets the standard. This reduces the technical threshold for operators and the subjectivity of result interpretation, and can effectively solve the problems in the background technology.

[0015] To achieve the above objectives, the present invention provides the following technical solution: a highway subgrade compaction testing device and testing method, comprising a sampling cylinder and a positioning sleeve, wherein a spiral sampling rod for drilling samples is rotatably arranged inside the sampling cylinder, the sampling cylinder is movably inserted into the positioning sleeve, the bottom of the positioning sleeve extends downward to form an annular insert plate that can be inserted into the subgrade, and the lower surface edge of the positioning sleeve is provided with evenly distributed insert rods for fixing the positioning sleeve;

[0016] The positioning sleeve has a frustum structure and a liquid storage chamber is provided inside the positioning sleeve. A pressurized feed pipe is provided on the upper side of the positioning sleeve for injecting liquid and pressurized gas into the liquid storage chamber. A safety valve is provided on the lower inner side of the positioning sleeve for discharging the liquid inside the liquid storage chamber into the cavity between the positioning sleeve and the sampling tube.

[0017] A resistivity sensor 1 is installed in the groove at the lower end of the outer periphery of the sampling tube, and a resistivity sensor 2 is installed in the groove at the lower end of the side of the insertion rod corresponding to the sampling tube. The resistivity sensor 1 detects the seepage rate of liquid along the gap between the sampling tube and the roadbed, and the resistivity sensor 2 detects the lateral spread rate of water, thereby determining the compaction degree of the roadbed.

[0018] As a preferred embodiment of the present invention, the inner side of the positioning sleeve is provided with a limiting plate for limiting the sampling cylinder, and the middle side of the sampling cylinder is provided with a clamping plate that slides up and down with the limiting plate.

[0019] As a preferred embodiment of the present invention, the upper surface of the positioning sleeve is provided with an annular groove, and the upper side of the sampling cylinder is provided with a sealing pressure plate adapted to the annular groove, which is used to seal the cavity between the sampling cylinder and the positioning sleeve.

[0020] As a preferred embodiment of the present invention, the pressurized feed pipe is equipped with a valve.

[0021] As a preferred embodiment of the present invention, the bottom of the outer periphery of the sampling tube is chamfered, and the bottom of the inner side of the annular insert is chamfered.

[0022] A method for detecting the compaction degree of a highway subgrade using a testing device includes the following steps:

[0023] S1. Device installation and fixing:

[0024] Place the positioning sleeve at the test point on the highway subgrade, and insert the rod at its bottom into the subgrade to stabilize and fix the positioning sleeve; ensure that the insertion depth of the rod is greater than the insertion depth of the annular plate of the positioning sleeve to provide reliable anchoring;

[0025] S2. Sampling operation:

[0026] Insert the sampling cylinder into the positioning sleeve, so that the clamping plate and the limiting plate are slidably connected. Drive the spiral sampling rod to rotate through the motor, and press down the sampling cylinder through the pressure plate to drill the roadbed sample; when the sealing pressure plate is pressed into the annular groove, the sampling is completed.

[0027] S3. Water injection and pressurization:

[0028] Turn on resistivity sensor one and resistivity sensor two to make them work, open the valve, and inject liquid into the storage chamber of the positioning sleeve through the pressurized feed pipe. After filling, close the valve. Then, connect the external pressurization device to the pressurized feed pipe, open the valve again, and inject pressurized gas into the storage chamber to raise the pressure to the preset value and keep it stable.

[0029] S4. Liquid release and permeation detection:

[0030] Maintain pressurization. When the pressure in the storage chamber causes the safety valve to open, the liquid is discharged into the cavity between the positioning sleeve and the sampling tube. At the same time, timing begins, and the humidity change signals of resistivity sensor one and resistivity sensor two are monitored in real time.

[0031] The time it takes for liquid to seep vertically down the gap between the sampling tube and the roadbed is detected by a resistivity sensor, and the time T1 from the release of liquid to the detection of the humidity change by the resistivity sensor is recorded.

[0032] The time it takes for the liquid to spread laterally along the roadbed is detected by resistivity sensor 2, and the time T2 from the release of the liquid to the detection of the humidity change by resistivity sensor 2 is recorded.

[0033] S5. Compaction Degree Judgment:

[0034] Based on times T1 and T2, and referring to the pre-calibrated compaction degree-permeability time relationship curve, the compaction degree of the roadbed is determined. The pre-calibration curve is produced through laboratory tests, and the correspondence between compaction degree and T1 and T2 is established for different soil types.

[0035] If T1 and T2 are relatively long, it indicates that the liquid infiltration rate is slow and the roadbed compaction is high;

[0036] If T1 and T2 are shorter, it indicates that the liquid infiltration rate is fast and the roadbed compaction degree is low;

[0037] By comparing the actual measured T1 and T2 with the standard values, it can be determined whether the compaction degree meets the standard.

[0038] As a preferred embodiment of the present invention, in S4, after the liquid in the storage chamber is emptied, the continuously supplied high-pressure gas enters the cavity through the safety valve, continuously applying pressure to the liquid in the cavity and accelerating the liquid's penetration rate into the roadbed.

[0039] As a preferred embodiment of the present invention, the preset pressure value in S3 is 0.1-0.5 MPa.

[0040] Compared with the prior art, the beneficial effects of the present invention are:

[0041] 1. The highway subgrade compaction testing device and method of the present invention, through the unique combination of sampling cylinder and spiral sampling rod, prepares a natural channel for subsequent testing while drilling samples; during subsequent compaction testing, the sealed cavity formed by the positioning sleeve can be used to immediately conduct permeation testing, shortening the "sampling-testing-analysis" process that takes several hours in traditional methods to be completed within a few minutes on site, which greatly meets the need for immediate and rapid evaluation of compaction quality during construction.

[0042] 2. The highway subgrade compaction testing device and method of the present invention, by conducting a penetration test in the gap formed by sampling, allows resistivity sensor one and resistivity sensor two to directly sense the actual state of the subgrade material, avoiding structural disturbances caused by sample transfer and handling in traditional methods, and resulting in more accurate results.

[0043] 3. The highway subgrade compaction testing device and method of the present invention realizes dual and three-dimensional verification of the uniformity of subgrade compaction by monitoring the infiltration time of water in both vertical downward infiltration and lateral diffusion, effectively eliminating the interference of local defects, and making the evaluation results more comprehensive and reliable.

[0044] 4. The highway subgrade compaction testing device and method of the present invention use water and compressed air as the medium for the entire testing process and measure through a resistivity sensor, which completely eliminates the radioactive hazards and high regulatory costs of nuclear density meters, and makes the equipment free from special restrictions in the procurement, use and disposal stages.

[0045] 5. The highway subgrade compaction detection device and method of the present invention are based on the principle of fluid permeation in porous media. The higher the compaction, the denser the structure, the narrower and more tortuous the permeation path, the slower the water permeation rate, and the longer it takes for the sensor to detect the change in resistance. This physical principle is clear and explicit. By recording simple time parameters and comparing them with the pre-calibrated curve, it is possible to intuitively determine whether the compaction meets the standard, thereby reducing the technical threshold for operators and the subjectivity of result interpretation. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the structure of the present invention;

[0047] Figure 2 This is a cross-sectional structural diagram of the present invention;

[0048] Figure 3 This is a schematic diagram of the cross-sectional structure of the sampling cylinder and positioning sleeve of the present invention;

[0049] Figure 4 This is a schematic diagram of water seepage after the sampling tube is inserted into the roadbed.

[0050] In the diagram: 1 Sampling cylinder, 2 Spiral sampling rod, 21 Motor, 3 Resistivity sensor one, 4 Positioning sleeve, 41 Limiting plate, 42 Safety valve, 43 Annular groove, 5 Insert rod, 51 Resistivity sensor two, 6 Pressure feed pipe, 61 Valve, 7 Sealing plate, 8 Pressure plate, 9 Clamping plate. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Please see Figure 1-4 This invention provides a technical solution: a highway subgrade compaction testing device and method, comprising a sampling cylinder 1 and a positioning sleeve 4. The sampling cylinder 1 is rotatably equipped with a spiral sampling rod 2 for drilling samples. The sampling cylinder 1 moves up and down and is inserted into the positioning sleeve 4. The bottom of the positioning sleeve 4 extends downward to form an annular insert plate that can be inserted into the subgrade. The lower surface edge of the positioning sleeve 4 is provided with evenly distributed insert rods 5 for fixing the positioning sleeve 4. The design of the frustoconical positioning sleeve 4, the bottom annular insert plate, and the insert rods 5 ensures the overall stability of the device during the testing process and provides a reliable sealing basis for pressure penetration.

[0053] The positioning sleeve 4 has a frustum-shaped structure and a liquid storage chamber inside. The upper side of the positioning sleeve 4 is equipped with a pressurized feed pipe 6 for injecting liquid and pressurized gas into the liquid storage chamber. The lower inner side of the positioning sleeve 4 is equipped with a safety valve 42 for discharging the liquid inside the liquid storage chamber into the cavity between the positioning sleeve 4 and the sampling cylinder 1. The cooperation between the sealing plate 7 and the annular groove 43, as well as the pressurization and liquid release path constructed by the pressurized feed pipe 6 and the safety valve 42, ensure the controllability and repeatability of the detection process.

[0054] The unique combination of sampling tube 1 and spiral sampling rod 2 provides a natural channel for subsequent testing while drilling samples. During subsequent compaction testing, the sealed cavity formed by positioning sleeve 4 allows for immediate penetration testing. This shortens the "sampling-testing-analysis" process, which used to take several hours in traditional methods, to just a few minutes on-site, greatly satisfying the need for immediate and rapid assessment of compaction quality during construction.

[0055] A resistivity sensor 3 is installed in the groove at the lower end of the outer periphery of the sampling tube 1, and a resistivity sensor 51 is installed in the groove at the lower end of the side of the insertion rod 5 corresponding to the sampling tube 1. By embedding the sensors in the grooves, direct scraping with the subgrade material during drilling and insertion is effectively prevented, greatly improving the service life and measurement stability of the sensors. The resistivity sensor 3 detects the seepage rate of liquid along the gap between the sampling tube 1 and the subgrade, and the resistivity sensor 51 detects the lateral spread rate of water, thereby determining the subgrade compaction degree. By conducting a permeation test in the gap formed by sampling, the resistivity sensors 3 and 51 directly sense the actual state of the subgrade material, avoiding structural disturbances caused by sample transfer and handling in traditional methods, resulting in more accurate results.

[0056] Furthermore, by monitoring the infiltration time of water in both vertical and lateral directions, a dual and three-dimensional verification of the uniformity of roadbed compaction was achieved, effectively eliminating the interference of local defects and making the evaluation results more comprehensive and reliable.

[0057] like Figure 4 As shown in the shaded area near sampling cylinder 1, during the detection process, the liquid enters the annular gap between sampling cylinder 1 and the roadbed from the upper cavity and permeates from top to bottom. Placing the sensor at the bottom end of the gap allows for the most direct and accurate capture of the critical moment when the liquid front just completely fills the gap and begins to permeate into the lower roadbed matrix. The recorded time T1 is the vertical permeation time of the liquid through the entire sampling gap. If placed in other positions, the complete permeation time of the gap cannot be measured.

[0058] like Figure 4 The shaded area shown indicates that the insertion rod 5 is located outside the positioning sleeve 4. After it is inserted into the roadbed, there is a certain radial distance between it and the sampling area. When the liquid spreads laterally from the sampling gap to the surrounding roadbed, the sensor 51 located at this position can effectively detect the moment when the water spreads laterally to this radial distance. The recorded time T2 reflects the speed of the liquid spreading laterally. This position is chosen to define a fixed and repeatable lateral detection radius.

[0059] In summary, the sensor position is set based on the explicit requirement of detecting the endpoint of a fixed liquid path, and is a key design feature of this solution to achieve quantitative detection, enabling accurate monitoring of the triggering moments of infiltration and lateral spread.

[0060] The resistivity sensor 3 and resistivity sensor 51 used in this application are moisture-sensitive resistive sensors based on porous ceramic or polymer sensitive materials, often referred to as soil moisture resistive sensors. A soil moisture resistive sensor of model SEN0193 can be used. Their working principle is as follows: When the sensitive element of the sensor is exposed to the environment, and the humidity (water content) of the surrounding medium changes, the sensitive material adsorbs or releases water molecules. These water molecules alter the ion conduction channels or polarization characteristics within the material, resulting in a significant and continuous change in the resistance (or conductivity) measured at both ends of the sensitive material. Specifically, as humidity increases, the resistance decreases (conductivity increases); as humidity decreases, the resistance increases (conductivity decreases).

[0061] In this application, the initially dry roadbed medium has a high resistance value; when the moisture penetration front reaches the location of the sensor, the humidity of the medium around the sensor increases sharply, causing a sudden change (sudden drop) in its resistance value; the monitoring circuit can accurately determine the time when the moisture arrives by identifying the point of change in resistance value; therefore, "detecting humidity changes" is essentially achieved by measuring the sudden change in the resistance value of the sensor itself.

[0062] Furthermore, the inner side of the positioning sleeve 4 is provided with a limiting plate 41 to limit the sampling cylinder 1, and the middle of the side of the sampling cylinder 1 is provided with a clamping plate 9 that is slidably connected to the limiting plate 41 to keep the sampling cylinder 1 moving up and down without rotating. Figure 3 As shown, the clamping plate 9 is installed on the outer wall of the sampling cylinder 1, and the limiting plate 41 is installed on the inner wall of the positioning sleeve 4.

[0063] There is a gap between the positioning sleeve 4 and the sampling cylinder 1, allowing the clamping plate 9 to pass through the gap and enter the interior of the positioning sleeve 4.

[0064] Furthermore, an annular groove 43 is provided on the upper surface of the positioning sleeve 4, and a sealing pressure plate 7 adapted to the annular groove 43 is provided on the upper side of the sampling cylinder 1 to seal the cavity between the sampling cylinder 1 and the positioning sleeve 4.

[0065] Furthermore, a valve 61 is provided on the pressurized feed pipe 6.

[0066] Furthermore, a chamfer is provided at the bottom of the outer periphery of the sampling tube 1 to facilitate its insertion into the roadbed, and a chamfer is provided at the bottom of the inner side of the annular insert plate.

[0067] A method for detecting the compaction degree of a highway subgrade using a testing device includes the following steps:

[0068] S1. Device installation and fixing:

[0069] The positioning sleeve 4 is placed at the test point of the highway subgrade, and the insertion rod 5 at its bottom is inserted into the subgrade to make the positioning sleeve 4 stable and fixed; ensure that the insertion depth of the insertion rod 5 is greater than the insertion depth of the annular insertion plate of the positioning sleeve 4 to provide reliable anchoring.

[0070] S2. Sampling operation:

[0071] The sampling cylinder 1 is inserted into the positioning sleeve 4, so that the clamping plate 9 is slidably connected to the limiting plate 41. The spiral sampling rod 2 is driven to rotate by the motor 21, and the sampling cylinder 1 is pressed down by the pressure plate 8, thereby drilling the roadbed sample. When the sealing pressure plate 7 is pressed into the annular groove 43, the sampling is completed.

[0072] S3. Water injection and pressurization:

[0073] Turn on resistivity sensor 3 and resistivity sensor 51 to make them work, open valve 61, inject liquid into the storage chamber of positioning sleeve 4 through pressurized feed pipe 6, and close valve 61 after filling; then connect external pressurization equipment to pressurized feed pipe 6, open valve 61 again, and inject pressurized gas into the storage chamber to raise the pressure to the preset value and keep it stable.

[0074] S4. Liquid release and permeation detection:

[0075] Maintain pressurization. When the pressure in the storage chamber causes the safety valve 42 to open, the liquid is discharged into the cavity between the positioning sleeve 4 and the sampling cylinder 1. At the same time, timing begins, and the humidity change signals of resistivity sensor 3 and resistivity sensor 51 are monitored in real time.

[0076] The time it takes for liquid to seep vertically down through the gap between the sampling tube 1 and the roadbed is detected by resistivity sensor 3, and the time T1 from the release of liquid to the detection of the humidity change by resistivity sensor 3 is recorded.

[0077] The time it takes for the liquid to spread laterally along the roadbed is detected by resistivity sensor 251, and the time T2 from the release of the liquid to the detection of the humidity change by resistivity sensor 251 is recorded.

[0078] S5. Compaction Degree Judgment:

[0079] Based on times T1 and T2, and referring to the pre-calibrated compaction degree-permeability time relationship curve, the compaction degree of the roadbed is determined. The pre-calibration curve is produced through laboratory tests, and the correspondence between compaction degree and T1 and T2 is established for different soil types.

[0080] If T1 and T2 are relatively long, it indicates that the liquid infiltration rate is slow and the roadbed compaction is high;

[0081] If T1 and T2 are shorter, it indicates that the liquid infiltration rate is fast and the roadbed compaction degree is low;

[0082] By comparing the actual measured T1 and T2 with the standard values, it can be determined whether the compaction degree meets the standard.

[0083] Furthermore, in S4, after the liquid in the storage chamber is emptied, the continuously supplied high-pressure gas enters the cavity through the safety valve 42, continuously applying pressure to the liquid in the cavity and accelerating the liquid's penetration rate into the roadbed.

[0084] Furthermore, the preset pressure value in S3 is 0.1-0.5 MPa.

[0085] During multi-point sampling and testing, after sampling one sample, the motor 21 is controlled to rotate in the opposite direction to discharge the sample from the sampling cylinder 1.

[0086] This invention uses water and compressed air as media and measures resistivity using a resistivity sensor. Based on the principle of fluid permeation in porous media, the higher the compaction degree, the denser the structure, the narrower and more tortuous the permeation path, the slower the water permeation rate, and the longer it takes for the sensor to detect the change in resistance. This physical principle is clear and explicit. By recording simple time parameters and comparing them with a pre-calibrated curve, it is possible to intuitively determine whether the compaction degree meets the standard, thus reducing the technical threshold for operators and the subjectivity of result interpretation.

[0087] All parts not disclosed in this invention are prior art, and their specific structures, materials, and working principles will not be described in detail. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A highway subgrade compaction detection device, comprising a sampling cylinder (1) and a positioning sleeve (4), characterized in that: The inside of the sampling cylinder (1) is rotationally provided with a spiral sampling rod (2) for drilling samples, the sampling cylinder (1) is movably inserted into the inside of the positioning sleeve (4), the bottom of the positioning sleeve (4) extends downward to form an annular insertion plate which can be inserted into the roadbed, the lower edge of the lower surface of the positioning sleeve (4) is provided with uniformly distributed insertion rods (5) for fixing the positioning sleeve (4), the inner side of the positioning sleeve (4) is provided with a limiting plate (41) for limiting the sampling cylinder (1), and the middle of the side surface of the sampling cylinder (1) is provided with a clamping plate (9) which is slidably connected with the limiting plate (41), the upper surface of the positioning sleeve (4) is provided with an annular groove (43), and the upper end of the side surface of the sampling cylinder (1) is provided with a sealing press plate (7) which is matched with the annular groove (43) and used for sealing the cavity between the sampling cylinder (1) and the positioning sleeve (4); The positioning sleeve (4) is a conical frustum structure, and a liquid storage cavity is formed in the inside of the positioning sleeve (4), the upper end of the side surface of the positioning sleeve (4) is provided with a pressurized feeding pipe (6) which is used for injecting liquid and pressurized gas into the liquid storage cavity, a valve (61) is arranged on the pressurized feeding pipe (6), and the lower end of the inner side of the positioning sleeve (4) is provided with a safety valve (42) which is used for discharging the liquid in the liquid storage cavity into the cavity between the positioning sleeve (4) and the sampling cylinder (1); The resistivity sensor one (3) is arranged in the groove at the lower end of the outer circumferential side of the sampling cylinder (1), and the resistivity sensor two (51) is arranged in the groove at the lower end of the side surface of the side of the insertion rod (5) corresponding to the sampling cylinder (1), the liquid infiltration speed along the gap between the sampling cylinder (1) and the roadbed is detected by the resistivity sensor one (3), and the water lateral spreading speed is detected by the resistivity sensor two (51), so as to judge the roadbed compactness.

2. The highway subgrade compactness detection device according to claim 1, characterized in that: The bottom of the outer circumferential side of the sampling cylinder (1) is chamfered, and the inner side of the bottom of the annular insertion plate is chamfered.

3. A detection method based on the highway subgrade compaction degree detection device of claim 2, characterized in that: The method comprises the following steps: S1, device installation and fixation: The positioning sleeve (4) is placed at the detection point of the highway roadbed, the insertion rod (5) at the bottom of the positioning sleeve (4) is inserted into the roadbed, so that the positioning sleeve (4) is stably fixed; the insertion depth of the insertion rod (5) is greater than the insertion depth of the annular insertion plate of the positioning sleeve (4), so as to provide reliable anchoring; S2, sampling operation: The sampling cylinder (1) is inserted into the inside of the positioning sleeve (4), the clamping plate (9) is slidably connected with the limiting plate (41), the spiral sampling rod (2) is driven to rotate by the motor (21), and the sampling cylinder (1) is pressed down by the press plate (8), so as to drill the roadbed sample; when the sealing press plate (7) is pressed into the annular groove (43), the sampling is completed; S3, water injection and pressurization: The resistivity sensor one (3) and the resistivity sensor two (51) are turned on to make them work, the valve (61) is opened, liquid is injected into the liquid storage cavity of the positioning sleeve (4) through the pressurized feeding pipe (6), the valve (61) is closed after the liquid is filled; then the pressurized feeding pipe (6) is connected with the external pressurizing equipment, the valve (61) is opened again, and pressurized gas is injected into the liquid storage cavity, so that the pressure is increased to the preset value and kept stable; S4, liquid release and penetration detection: Maintain the pressure, when the liquid chamber pressure makes the safety valve (42) open, the liquid is discharged into the cavity between the positioning sleeve (4) and the sampling cylinder (1); At the same time, start timing, and real-time monitor the humidity change signal of resistivity sensor one (3) and resistivity sensor two (51); Through resistivity sensor one (3) to detect the vertical downward infiltration time of liquid along the gap between the sampling cylinder (1) and the roadbed, record the time T1 from the release of liquid to the detection of humidity mutation by resistivity sensor one (3); Through resistivity sensor two (51) to detect the lateral spread time of liquid along the roadbed, record the time T2 from the release of liquid to the detection of humidity mutation by resistivity sensor two (51); S5, degree of compaction judgment: According to the time T1 and T2, refer to the pre-marked compaction-penetration time curve to judge the roadbed compaction degree; The pre-marked curve is made by laboratory test, and the corresponding relationship between compaction degree and T1, T2 is established for different soil types; If T1 and T2 are long, it means that the liquid penetration speed is slow, and the roadbed compaction degree is high; If T1 and T2 are short, it means that the liquid penetration speed is fast, and the roadbed compaction degree is low; By comparing the actual measured T1 and T2 with the standard value, determine whether the compaction degree meets the standard.

4. The method of claim 3, wherein the highway subgrade compaction detection device is characterized in that: In S4, after the liquid in the liquid chamber is discharged, the continuously input high pressure gas enters the cavity through the safety valve (42), continuously applies pressure to the liquid in the cavity, and accelerates the penetration speed of the liquid into the roadbed.

5. The method of claim 3, wherein the highway subgrade compaction detection device is characterized in that: The pre-set pressure value in S3 is 0.1-0.5MPa.

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