A non-destructive pavement compaction measurement device and compaction measurement method

Abstract

The present invention relates to a non-destructive pavement compaction measurement device and compaction measurement method, comprising a device bracket, a central compaction hammer, and an annular compaction hammer located on the periphery of the central compaction hammer. The central compaction hammer and the annular compaction hammer are independently provided. The bottom of the central compaction hammer has a central contact portion that contacts and cooperates with the pavement, and the bottom of the annular compaction hammer has an annular contact portion that contacts and cooperates with the pavement located on the periphery of the central contact portion. The device bracket is provided with a central impact hammer and peripheral impact hammers that can be raised in height under the drive of a lifting mechanism. The bottom of the central impact hammer has a first impact portion for impacting the upper end of the central compaction hammer, and the bottom of the peripheral impact hammer has a second impact portion for synchronously impacting the annular compaction hammer when the first impact portion impacts the central compaction hammer. The present invention solves the technical problem in the prior art that compaction measurement requires high labor intensity due to the need to dig a pit, fill sand, and collect sand on the pavement.

Description

Technical Field

[0001] The present invention relates to the field of road surface compaction measurement, and in particular to a road surface non-destructive compaction measurement device and a compaction measurement method. Background Art

[0002] Compaction degree refers to the ratio of the density of the compacted roadbed material to the standard density, expressed as a percentage, represented by the letter k.

[0003] Compaction of roadbed materials is typically achieved using on-site rollers. Standard density refers to the maximum density of a roadbed material under standard laboratory conditions for a specified optimal mix. For on-site soil roadbed materials that are sensitive to moisture content, standard density refers to the maximum dry density.

[0004] It is usually necessary to obtain the standard density in the laboratory. The specific method is as follows: the roadbed material with the same proportion as on site is placed in a compaction drum, and then the roadbed material is compacted in circles by an impact hammer with a diameter much smaller than the compaction drum, so as to obtain the volume of the compacted roadbed material, and then the standard density of the roadbed material is obtained according to the mass of the roadbed material.

[0005] The on-site density of the roadbed made of roadbed materials is obtained as follows: at the construction site, a cylindrical road pit with a certain cross-sectional area is dug on the road surface, and then sand is filled into the cylindrical road pit. After the sand is flattened, the sand is taken out and used to measure the volume of the cylindrical road pit. The roadbed material dug out from the cylindrical road pit is weighed to obtain the weight, thereby calculating the actual density of the on-site roadbed material. The actual density is compared with the standard density to obtain the compaction degree of the roadbed material. The closer the actual density is to the standard density, the better the compaction effect of the roadbed.

[0006] It can be seen that in order to obtain the compaction degree of the roadbed on site, it is necessary to dig holes on site, fill sand, and then collect the sand. The work intensity is high and the measurement efficiency is low. In addition, it is necessary to dig holes on the road surface, which is a destructive test of the road surface and is not conducive to the structural stability of the roadbed. Summary of the Invention

[0007] The purpose of the present invention is to provide a non-destructive pavement compaction measuring device to solve the technical problem in the prior art that compaction measurement requires high labor intensity due to the need to dig pits, fill sand and collect sand on the pavement; the purpose of the present invention is also to provide a compaction measurement method that is suitable for the non-destructive pavement compaction measuring device.

[0008] To solve the above technical problems, the technical solution of a non-destructive pavement compaction measurement device in the present invention is as follows:

[0009] A device for measuring the non-destructive compaction degree of a road surface comprises a device bracket, a central compacting hammer and an annular compacting hammer located at the periphery of the central compacting hammer. The central compacting hammer and the annular compacting hammer are independently arranged. The bottom of the central compacting hammer has a central contact portion that contacts and cooperates with the road surface. The bottom of the annular compacting hammer has an annular contact portion that contacts and cooperates with the road surface and is located at the periphery of the central contact portion. The device bracket is provided with a central impact hammer and peripheral impact hammers that can be raised in height under the drive of a lifting mechanism. The bottom of the central impact hammer has a first impact portion for impacting the upper end of the central compacting hammer. The bottom of the peripheral impact hammer has a second impact portion for synchronously impacting the annular compacting hammer when the first impact portion impacts the central compacting hammer.

[0010] Furthermore, the road surface non-destructive compaction measuring device also includes an annular pad arranged on the periphery of the annular contact portion. The annular pad and the annular compacting hammer are arranged independently of each other, and the bottom surface of the annular pad is used to contact and cooperate with the road surface.

[0011] Furthermore, the central impact hammer and the annular impact hammer are independently arranged, and the weight of the central compacting hammer is the same as the weight of the central impact hammer.

[0012] Furthermore, the first impact portion is a ball head structure for contacting and cooperating with the upper end point of the central striking hammer.

[0013] Furthermore, the second impact portion is an annular protrusion for linear contact with the upper end of the annular hammer.

[0014] Furthermore, the radial distance between the central contact portion and the annular contact portion is 0.1 cm to 3 cm.

[0015] Furthermore, a central hammer guide rod that cooperates with the central hammer guide movement and a peripheral hammer guide rod that cooperates with the peripheral hammer guide movement are provided on the device bracket. The lifting mechanism includes a lifting drum driven by a power mechanism, and a first pull rope and a second pull rope are wound around the lifting drum. The first pull rope is connected to the central hammer, and the second pull rope is connected to the peripheral hammer.

[0016] The technical solution of the compaction degree measurement method in the present invention is:

[0017] The method comprises the following steps: first, a lifting mechanism raises the height of a central impact hammer and a peripheral impact hammer; second, the central impact hammer and the peripheral impact hammer fall, the first impact part of the central impact hammer hits the upper end of the central compacting hammer, and at the same time, the second impact part of the peripheral impact hammer hits the upper end of the annular compacting hammer; third, the first and second steps are repeated multiple times, and the road surface directly below the central compacting hammer produces a deformation of a height x, then the compaction degree of the inspected road surface k=100(Xx) / X, where X represents the road surface thickness before the road surface is impacted by the central compacting hammer.

[0018] Furthermore, n is obtained in the following way: when the center hammer impacts the road surface for the nth time, the settlement displacement of the road surface is 0.1X.

[0019] Furthermore, n is obtained in the following way: the roadbed material identical to the road surface being inspected is placed in a compacting cylinder, and the roadbed material in the compacting cylinder is compacted by an impact hammer. When the impact hammer impacts the roadbed material for the mth time, the roadbed material can no longer be compressed. When the impact hammer impacts the road surface for the m-1th time, the compression displacement of the roadbed material is recorded as L. When the center compacting hammer impacts the road surface for the nth time, the compression displacement of the road surface is L.

[0020] The beneficial effects of the present invention are as follows: when the non-destructive compaction measuring device of the present invention is used, the road surface does not need to be excavated, but the non-destructive compaction measuring device of the road surface is directly placed on the road surface, and after the central impact hammer and the peripheral impact hammer are lifted to a certain height, the central impact hammer and the peripheral impact hammer are dropped to hit the central compacting hammer and the annular compacting hammer, and the road surface is compacted by the central compacting hammer and the annular compacting hammer. Since the central compacting hammer and the annular compacting hammer are always in contact with the road surface, the problem of surface cracking of the road surface during impact can be avoided, and at the same time, due to the existence of the annular compacting hammer, the central compacting hammer can be made When the compacting hammer impacts the road surface, a certain lateral limit is formed on the periphery of the roadbed material layer on the lower side of the center compacting hammer to prevent the roadbed material layer on the lower side of the center compacting hammer from expanding during impact (expansion will cause the weight of the corresponding roadbed material layer to change). This ensures that the roadbed material layer on the lower side of the center compacting hammer is only deformed vertically as much as possible, thereby ensuring the measurement results. By measuring the height change of the roadbed material layer on the lower side of the center compacting hammer, the compaction degree of the inspected road surface can be measured. There is no need to dig pits, fill sand, or excavate sand. The measurement process is simple and is a non-destructive operation on the road surface, which will not affect the structural performance of the road surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown in an illustrative and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0022] Figure 1 It is a structural schematic diagram of an embodiment of a non-destructive pavement compaction measurement device of the present invention;

[0023] Figure 2 yes Figure 1 Schematic diagram of the central impact hammer and the peripheral impact hammer after being lifted;

[0024] Figure 3 It is the stress distribution diagram when a single center compacting hammer compacts the pavement;

[0025] Figure 4This is the stress distribution diagram when a single ring compacting hammer compacts the road surface;

[0026] Figure 5 This is the stress distribution diagram when the central compacting hammer and the ring compacting hammer compact the road surface together;

[0027] Figure 6 It is a schematic diagram of the cooperation between the impact hammer and the compacting cylinder in the present invention;

[0028] Explanation of the accompanying drawings: 1. Device bracket; 2. Lifting drum; 3. First pull rope; 4. Second pull rope; 5. Center impact hammer guide rod; 6. Peripheral impact hammer guide rod; 7. Center impact hammer; 8. Peripheral impact hammer; 9. Annular compacting hammer; 10. Center compacting hammer; 11. Annular pad; 12. Annular flange; 13. Road surface; 14. Roadbed material layer; 15. First impact part; 16. Second impact part; 17. First stress area; 18. Second stress area; 19. Third stress area; 20. Impact hammer; 21. Roadbed material; 22. Compacting drum. DETAILED DESCRIPTION

[0029] To facilitate understanding of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0030] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0031] An embodiment of a non-destructive pavement compaction measurement device of the present invention is as follows: Figures 1 to 6 The apparatus comprises a support 1, a central hammer 10, and an annular hammer 9 located peripherally thereto. The central hammer 10 has a central contact portion at its bottom for contacting the road surface. The annular hammer 9 has an annular contact portion located peripherally thereto for contacting the road surface. The radial clearance between the central and annular contact portions is 0.8 cm.

[0032] The device bracket is provided with a central impact hammer 7 and a peripheral impact hammer 8 which can be raised in height under the drive of the lifting mechanism. The bottom of the central impact hammer 7 has a first impact part 15 for impacting the upper end of the central impact hammer. The bottom of the peripheral impact hammer 8 has a second impact part 16 for synchronously impacting the annular impact hammer when the first impact part impacts the central impact hammer. Both the peripheral impact hammer and the second impact part are annular structures.

[0033] The central hammer and the annular hammer are independently mounted, and the central hammer weighs the same as the central hammer. The annular hammer has an inward-turned annular flange 12 at its bottom. The central hammer includes a large-diameter section and a small-diameter section disposed vertically. The upper end of the large-diameter section is struck by the bottom of the central hammer, while the lower end of the small-diameter section passes through the inner hole of the annular flange and contacts the ground.

[0034] The road surface non-destructive compaction measurement device also includes an annular pad 11 arranged on the periphery of the annular contact portion. The annular pad 11 and the annular compacting hammer 9 are independently arranged, and the bottom surface of the annular pad 11 is used to contact and cooperate with the road surface. In this embodiment, the device bracket includes a vertical frame and a horizontal frame. The lower end of the vertical frame is connected to the annular pad. The horizontal frame is fixed to the upper end of the vertical frame. The lower end of the horizontal frame is fixed with a central hammer guide rod 5 that cooperates with the central hammer guide movement and a peripheral hammer guide rod 6 that cooperates with the peripheral hammer guide movement. The central hammer guide rod and the peripheral hammer guide rod are vertically arranged. There are two central hammer guide rods, which are spaced apart on the left and right. There are two peripheral hammer guide rods, which are spaced apart on the left and right.

[0035] The central impact hammer is matched with the central impact hammer guide rod for guiding movement, and the peripheral impact hammer is matched with the peripheral impact hammer guide rod for guiding movement.

[0036] The first striking portion 15 is a ball-shaped structure designed to contact the upper endpoint of the central hammer, while the second striking portion 16 is a ball-shaped structure designed to contact the upper linear end of the annular hammer. The central hammer guide rod avoids the contact point between the first striking portion and the central hammer, while the peripheral hammer guide rod avoids the contact line between the second striking portion and the annular hammer. The contact point ensures stable force on the central hammer when struck by the central hammer; similarly, the contact line ensures stable force on the annular hammer when struck by the peripheral hammers.

[0037] The lifting mechanism includes a lifting drum 2 driven by a power mechanism, the power mechanism includes a reduction motor, the power output end of the reduction motor is transmission-connected to the lifting drum 2, a first pull rope 3 and a second pull rope 4 are wound around the lifting drum, the first pull rope 3 is connected to the central impact hammer 7, and the second pull rope 4 is connected to the outer impact hammer 8.

[0038] Item 14 in the figure represents the roadbed material layer, and item 13 represents the road surface. When in use, the central compacting hammer, the ring compacting hammer and the ring pad are placed on the road surface. The height of the central impact hammer and the outer impact hammer are raised through the lifting mechanism, and then the central impact hammer and the outer impact hammer are released. The central impact hammer and the outer impact hammer move in free fall. At the same time that the central impact hammer hits the central compacting hammer, the outer impact hammer hits the ring compacting hammer.

[0039] The center hammer will make a central pit on the road surface, and the peripheral hammer will make an annular pit on the road surface. The depth of the central pit will be smaller than the depth of the annular pit. This is because, Figures 3-5 As shown, when the central compacting hammer is used to impact the road surface, a pear-shaped first stress area 17 will be generated in the roadbed material layer on the lower side of the central compacting hammer, that is, the roadbed material layer on the lower side of the central compacting hammer will extend outward. When impacted by the central compacting hammer, the roadbed material layer on the lower side of the central compacting hammer will not only be compressed axially, but also diffuse radially outward. At this time, the roadbed material layer directly below the central compacting hammer will not only change in volume, but also in weight. When only the annular compacting hammer impacts the road surface, an annular second stress area 18 will be generated on the lower side of the annular compacting hammer. In the present invention, the central compacting hammer and the annular compacting hammer strike the road surface simultaneously. The annular compacting hammer generates a second stress region on the roadbed material layer. This second stress region forms a certain extrusion pressure on the central roadbed material layer. This extrusion pressure can limit the outward extension of the roadbed material layer directly below the central compacting hammer. This extrusion pressure is like the container wall that obtains standard density in the laboratory. It limits the outward extension of the roadbed material layer directly below the central compacting hammer when it is squeezed, ensuring that the roadbed material layer directly below the central compacting hammer undergoes only volume changes as much as possible, while the mass does not change, providing an accurate basis for density calculation. As for the peripheral compacting hammers, when the peripheral compacting hammers strike the road surface, the roadbed material layer directly below the peripheral compacting hammers will expand, so the depth of the central pit will be basically smaller than the depth of the annular pit.

[0040] Therefore, when the central compacting hammer and the outer compacting hammer impact the road surface at the same time, due to the lateral limit of the outer compacting hammer, the stress area of ​​the roadbed material layer below the central compacting hammer is the third stress area 19. The third stress area is approximately cylindrical, and the roadbed material layer directly below the central compacting hammer does not extend when impacted.

[0041] The bottom of the central compacting hammer and the ring compacting hammer are always in contact with the road surface, which can avoid the problem of surface cracking when the road surface is impacted. If there is no central compacting hammer and the ring compacting hammer, the central impact hammer and the outer impact hammer are directly dropped from a high place to impact the road surface. Due to the problem of unstable force, the road surface will be cracked. This will not only damage the road surface, but also cause the weight of the roadbed material layer directly below the corresponding central impact hammer to change, affecting the calculation results.

[0042] The contact area between the center compacting hammer and the road surface is S, the weight of the roadbed material layer directly below the center compacting hammer is m, and the thickness of the roadbed material layer before being impacted by the center compacting hammer is X.

[0043] In order to obtain the maximum in-situ density, that is, the standard density, the settlement displacement of the road surface caused by the impact of the central compacting hammer is x. Due to the presence of the annular compacting hammer in the present invention, the mass of the roadbed material layer directly below the central compacting hammer is the same before and after the impact of the central compacting hammer.

[0044] The measured density of the inspected road surface is also called the in-situ measured density: ρ = m / (S*X)

[0045] Standard density is also called in-situ standard density: ρc=m / [S*(Xx)]

[0046] Compaction degree is also called in-situ compaction degree: k = (ρ / ρc) * 100 = 100 (Xx) / X (Formula 1)

[0047] In the above formula, X is the known value and x is the measured value. Therefore, when to start measuring x is critical. Assuming that there is such an operation, after only one impact process, it reaches the final compaction of the standard density, resulting in the minimum final compaction settlement displacement ∆x, and the contributed compaction degree is ∆k.

[0048] Normally, the compaction accuracy is 0.1mm, which means that we hope the compaction can produce a subdivision of 0.1mm.

[0049] Assuming the unimpacted roadbed material layer has a thickness of X = 200 mm, a single compaction is all that's needed to reach the standard density. The compaction degree scale is 0.1, and the final compaction produces only one compaction degree change. The corresponding settlement displacement from the final compaction is called the minimum single compaction settlement displacement ∆x.

[0050] From formula 1, we can get:

[0051] ∆k=100∆x / X

[0052] Where: X=200mm, ∆k=0.1.

[0053] Then: ∆x=∆kX / 100=0.2mm

[0054] That is to say: when the final compaction settlement displacement is less than 0.2mm, it is considered to have reached the in-situ standard density, which is a sign to stop compaction.

[0055] Specifically in this embodiment, the central compacting hammer impacts the road surface n times, where n is a positive integer. When the settlement value of the road surface below the central compacting hammer is 0.1X at the nth impact, the impact is stopped, and the standard density will be obtained. From the beginning of the impact to the end of the impact, the settlement displacement of the road surface below the central compacting hammer is x.

[0056] When the central hammer impacts the road surface, the settlement value of the road surface each time can be measured in the following way: 1. After each impact on the road surface, remove the central hammer and the ring hammer, and measure the depth of the central pit; 2. Lift the central hammer to the same height each time, detect the falling height of the central hammer each time, and calculate it through the height difference.

[0057] The above n can also be obtained in the following way: put the roadbed material 21 that is the same as the road surface to be inspected into the compaction cylinder 22, such as Figure 6 As shown, the roadbed material is a mixture of sand, gravel, and concrete that has not been compacted by a roller. The diameter of the impact hammer 20 matches the diameter of the compaction cylinder, the weight of the impact hammer is the same as the weight of the center impact hammer, and the impact height of each impact of the impact hammer is the same as the impact height of each impact of the center impact hammer. The impact hammer is used to compact the roadbed material in the compaction cylinder. When the roadbed material can no longer be compressed, it means that the roadbed material has reached the standard density. The compression displacement of the roadbed material is recorded as L when the impact hammer hits the road surface for the m-1th time. When the compression displacement of the road surface is L when the center impact hammer hits the road surface for the nth time, it means that the compression of the road surface has also reached the maximum and can no longer be compressed. At this time, the road surface below the center impact hammer has reached the standard density.

[0058] In other embodiments of the present invention, the radial spacing between the central contact portion and the annular contact portion can also be 0.1 cm, 1 cm, 2 cm or 3 cm, or other values ​​between 0.1 cm and 3 cm, or values ​​other than 0.1 cm and 0.3 cm; the lifting mechanism can also be in other forms, such as using a drive cylinder or an electric push rod to lift the height of the central impact hammer and the peripheral impact hammer. After lifting to a certain height, release the connection between the drive cylinder or electric push rod and the corresponding impact hammer to allow the impact hammer to fall freely.

[0059] An example of a method for measuring compaction is: Figures 1 to 5 As shown: the annular pad, central compacting hammer and annular compacting hammer of the pavement non-destructive compaction measuring device are placed on the pavement. The specific structure of the pavement non-destructive compaction measuring device is the same as the above-mentioned pavement non-destructive compaction measuring device embodiments, and will not be described in detail here.

[0060] The method comprises the following steps: first, a lifting mechanism raises the height of a central impact hammer and a peripheral impact hammer; second, the central impact hammer and the peripheral impact hammer fall, the first impact part of the central impact hammer hits the upper end of the central compacting hammer, and at the same time, the second impact part of the peripheral impact hammer hits the upper end of the annular compacting hammer; third, the first and second steps are repeated n times, where n is a positive integer, and the road surface directly below the central compacting hammer produces a deformation of a height of x, then the compaction degree of the road surface under inspection is k=100(Xx) / X, where X represents the road surface thickness before the road surface is impacted by the central compacting hammer.

[0061] n is obtained in the following way: when the center hammer hits the road surface for the nth time, the settlement displacement of the road surface is 0.1X.

[0062] The above n can also be obtained in the following manner: Place the same roadbed material as the road surface being inspected in a compaction drum. This roadbed material is a mixture of sand, gravel, and concrete and has not been compacted by a roller. The diameter of the impact hammer matches the diameter of the compaction drum, the weight of the impact hammer is the same as the weight of the center impact hammer, and the height of each impact of the impact hammer is the same as the height of each impact of the center impact hammer. Use the impact hammer to compact the roadbed material in the compaction drum. When the roadbed material can no longer be compressed, it indicates that the roadbed material has reached the standard density. Record the compression displacement of the roadbed material as L during the m-1th impact of the impact hammer. When the compression displacement of the road surface reaches L during the nth impact of the center impact hammer, it indicates that the road surface has also reached its maximum compression and can no longer be compressed. At this point, the road surface below the center impact hammer has reached the standard density.

[0063] In the foregoing description of this specification, unless otherwise expressly specified or limited, terms such as "fixed," "mounted," "connected," or "connected" should be understood broadly. For example, the term "connected" can refer to a fixed connection, a removable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediary; or the internal connection between two components or the interaction between two components. Therefore, unless otherwise expressly defined in this specification, those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0064] According to the above description of this specification, those skilled in the art may also understand that the terms used below, such as "up", "down", "front", "back", "left", "right", "length", "width", "thickness", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", "center", "longitudinal", "transverse", "clockwise" or "counterclockwise", etc., which indicate orientation or positional relationships, are based on the orientation or positional relationships shown in the drawings of this specification, and are only for the purpose of facilitating the explanation of the scheme of the present invention and simplifying the description, rather than explicitly or implicitly indicating that the device or element involved must have the specific orientation, be constructed and operate in a specific orientation. Therefore, the above-mentioned orientation or positional relationship terms cannot be understood or interpreted as limitations on the scheme of the present invention.

[0065] In addition, the terms "first" or "second" used in this specification to refer to numbers or ordinal numbers are used for descriptive purposes only and should not be understood as explicitly or implicitly indicating relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this specification, "plurality" means at least two, such as two, three or more, etc., unless otherwise clearly specified.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A non-destructive pavement compaction measurement device, characterized in that: It includes a device bracket, a central hammer and an annular hammer located outside the central hammer. The central hammer and the annular hammer are independently arranged. The bottom of the central hammer has a central contact portion that contacts and cooperates with the road surface. The bottom of the annular hammer has an annular contact portion that contacts and cooperates with the road surface and is located outside the central contact portion. The device bracket is provided with a central impact hammer and peripheral impact hammers that can be raised in height under the drive of a lifting mechanism. The bottom of the central impact hammer has a first impact portion for impacting the upper end of the central hammer. The bottom of the peripheral impact hammer has a second impact portion for synchronously impacting the annular hammer when the first impact portion impacts the central hammer. The bottom of the annular hammer has an inward-turned annular flange. The central hammer includes a large-diameter section and a small-diameter section arranged upper and lower. The upper end of the large-diameter section is used to be impacted by the bottom of the central hammer, and the lower end of the small-diameter section passes through the inner hole of the annular flange and contacts the ground.

2. The non-destructive pavement compaction measuring device according to claim 1, characterized in that: The road surface non-destructive compaction measuring device also includes an annular pad arranged on the periphery of the annular contact portion. The annular pad and the annular compacting hammer are arranged independently of each other, and the bottom surface of the annular pad is used for contacting and cooperating with the road surface.

3. The non-destructive pavement compaction measuring device according to claim 1, characterized in that: The central impact hammer and the annular impact hammer are independently arranged, and the weight of the central compacting hammer is the same as that of the central impact hammer.

4. The non-destructive pavement compaction measuring device according to claim 3, characterized in that: The first impact part is a ball head structure for contacting and cooperating with the upper end point of the central striking hammer.

5. The non-destructive pavement compaction measuring device according to claim 3, characterized in that: The second impact portion is an annular protrusion for linear contact with the upper end of the annular hammer.

6. The non-destructive pavement compaction measuring device according to claim 1, characterized in that: The radial distance between the central contact portion and the annular contact portion is 0.1 cm to 3 cm.

7. The non-destructive pavement compaction measuring device according to any one of claims 1 to 6, characterized in that: A central hammer guide rod that cooperates with the central hammer guide movement and a peripheral hammer guide rod that cooperates with the peripheral hammer guide movement are provided on the device bracket. The lifting mechanism includes a lifting drum driven by a power mechanism, and a first pull rope and a second pull rope are wound around the lifting drum. The first pull rope is connected to the central hammer, and the second pull rope is connected to the peripheral hammer.

8. A method for measuring the compaction of a pavement using a non-destructive compaction measuring device as claimed in any one of claims 1 to 7, the method comprising the following steps: a first step, a lifting mechanism lifting the height of the central impact hammer and the peripheral impact hammer; a second step, the central impact hammer and the peripheral impact hammer falling, the first impact part of the central impact hammer hitting the upper end of the central compacting hammer, and at the same time, the second impact part of the peripheral impact hammer hitting the upper end of the annular compacting hammer; a third step, repeating the first and second steps n times, where n is a positive integer, and the pavement directly below the central compacting hammer produces a deformation of x height, then the compaction degree of the tested pavement k=100(Xx) / X, where X represents the pavement thickness before the pavement is impacted by the central compacting hammer.

9. The compaction degree measurement method according to claim 8, characterized in that: n is obtained in the following way: when the center hammer hits the road surface for the nth time, the settlement displacement of the road surface is 0.1X.

10. The compaction degree measurement method according to claim 8, characterized in that: n is obtained in the following way: the roadbed material identical to the road surface being inspected is placed in a compacting cylinder, and the roadbed material in the compacting cylinder is compacted by an impact hammer. When the impact hammer impacts the roadbed material for the mth time, the roadbed material can no longer be compressed. The compression displacement of the roadbed material when the impact hammer impacts the road surface for the m-1th time is recorded as L. When the center compacting hammer impacts the road surface for the nth time, the compression displacement of the road surface is L.

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