A rapid detection method for subgrade compaction degree based on dynamic penetration penetration

Abstract

The application discloses a kind of based on power sounding penetration degree subgrade compactness rapid detection method, this method uses a kind of light power sounding device, the light power sounding device structure is: including probe rod device and orifice stool. Before field test, indoor test is carried out using the light power sounding device, and the compactness D F Corresponding drop distance H under every hammer N times penetration P L , this is used as field detection standard;Then according to the determined field detection standard, using the light power sounding device carries out engineering field detection, to single detection point, using the light power sounding device carries out detection, obtains drop distance H under every hammer N times penetration, and is recorded as P F ;When P F It is not greater than P L , determine that the detection point compactness is qualified, otherwise unqualified.The method of the application is simple in operation, fast in detection, little damage to the compacted subgrade, and no indoor test is needed after the start of field test, and the subgrade compactness can be obtained on site.

Description

Technical Field

[0001] This invention belongs to the field of rapid detection technology of roadbed compaction, and in particular relates to a rapid detection method for roadbed compaction based on dynamic penetration test. Background Technology

[0002] Compaction degree is a crucial indicator for controlling the quality of subgrade construction. In practical engineering, common methods for testing compaction degree include the sand cone method, water cone method, and ring cutter method. These methods are recommended by standards and can accurately obtain compaction degree indicators, with results serving as acceptance criteria. However, these methods also have drawbacks: First, they are destructive testing methods that cause significant damage to the subgrade. For example, the sand cone and water cone methods require excavating test pits on the compacted subgrade. Second, these methods are slow. Taking the sand cone method as an example, testing a single point requires both on-site excavation, sand filling, and weighing, as well as laboratory moisture content testing, resulting in very low efficiency and sometimes impacting project progress. In reality, for certain situations, such as the contractor's self-inspection of compaction degree, it is unnecessary to use such cumbersome testing methods. Therefore, it is necessary to develop a faster compaction degree testing method.

[0003] Dynamic cone penetration testing (DCPT) is a field testing method that reflects indicators such as the bearing capacity or strength of a roadbed. Bearing capacity and strength are often closely related to compaction degree; therefore, using DCPT to test roadbed compaction degree is technically feasible. DCPT can be divided into three types: ultra-heavy, heavy, and light. Light DCPT is the most convenient, requiring no large machinery and can be performed manually. Conventional light DCPT uses a 10kg drop hammer, with the number of blows required to penetrate 30cm as the test value. There have been attempts to use light DCPT for roadbed compaction degree testing, but these attempts still have some shortcomings, mainly in terms of testing accuracy and applicability. For roadbeds, the compaction process is layered, and compaction degree testing is also performed layer by layer. The thickness of each compacted layer is mostly less than the 30cm penetration target value of the light DCPT. When the penetration depth is less than 30cm, a recalculation must be performed, which introduces corresponding errors. Secondly, the impact energy of a 10kg drop hammer is relatively large, resulting in a significant penetration depth with each drop. This makes it difficult to precisely achieve the predetermined total penetration depth, which also introduces errors, as the error increases with distance from the predetermined value. Thirdly, conventional dynamic cone penetration tests (DPPTs) target penetration depth, often counting blows as a 30cm penetration. However, the actual number of blows required for 30cm penetration is unlikely to be an exact integer, as the probe's penetration depth is rarely precisely 30cm. Furthermore, penetration depth is generally measured using the borehole opening as a reference. During penetration, the opening can deform or collapse due to compression and vibration, further complicating penetration depth measurement. Some attempts have tried fitting the cumulative number of blows and cumulative penetration depth from multiple 30cm penetration depths to obtain indicators similar to or closely related to compaction degree, such as relative density or maximum dry density. However, this method is unsuitable for the needs of layered compaction testing of subgrades, where each layer typically does not exceed 30cm. Therefore, it is necessary to improve lightweight dynamic cone penetration testing devices and methods to better adapt them to compaction degree testing. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a rapid method for detecting the compaction degree of roadbed based on dynamic penetration test.

[0005] This invention is achieved through the following technical solution:

[0006] A rapid detection method for subgrade compaction based on dynamic penetration test (DPPT) is proposed. The method employs a lightweight dynamic penetration test device, which consists of a probe rod and a borehole holder.

[0007] The probe device includes a drop hammer, a probe rod, a probe, and an adjustable positioning ring. The probe is mounted at the bottom end of the probe rod, and an enlarged diameter section is fixedly installed in the middle of the probe rod. The drop hammer is slidably fitted onto the probe rod section above the enlarged diameter section. Two scales are provided on the probe rod: the first scale, located on the probe rod section below the enlarged diameter section, indicates the depth of penetration; the second scale, located on the probe rod section above the enlarged diameter section, indicates the drop distance of the drop hammer. An adjustable positioning ring is installed on the probe rod section above the enlarged diameter section, fitted onto the probe rod, and a tightening screw is provided on the adjustable positioning ring. By adjusting this tightening screw, the positioning position of the adjustable positioning ring on the probe rod can be adjusted, thereby determining the drop distance of the drop hammer during the test in conjunction with the second scale.

[0008] The orifice stool is used in conjunction with the probe device. The orifice stool includes a stool surface and stool legs supporting the stool surface. A through hole is provided in the center of the stool surface for the probe to pass through. A reading probe is provided on the stool surface to assist in reading the reading of the first section of the scale on the probe. Multiple elastic support wheel units are provided on the stool surface, evenly distributed in a circle around the through hole, for elastic rolling support of the probe. A plumb bob is connected to the bottom surface of the orifice stool surface to serve as a reference for the verticality of the probe.

[0009] The following is a rapid method for detecting the compaction degree of roadbed:

[0010] Step 1: Before on-site testing, conduct indoor tests using the aforementioned lightweight dynamic cone penetrometer to obtain the compaction degree D required for the roadbed. F The penetration depth P per N hammer blows at a corresponding drop distance H L This will serve as the standard for on-site engineering testing; the process includes the following steps:

[0011] Step 1.1: Take soil samples identical to those from the roadbed construction site and prepare specimens with a compaction degree of D in the test pit. The compaction degree D is the same as the required compaction degree D at the construction site. F Approximately equal to;

[0012] Step 1.2: The soil sample in the test pit is tested using the aforementioned lightweight dynamic penetrometer to obtain the penetration depth P per N hammer blows at a set drop distance H;

[0013] Step 1.3: Repeat steps 1.1 to 1.2 above, and conduct no less than three sets of tests. In each set of tests, the compaction degree D is greater than or less than the required compaction degree D on site. F Each sample shall be no less than one;

[0014] Step 1.4: Plot the compaction degree D-penetration degree P curves in groups, and deduce the relationship between D and compaction degree in this group of tests. F Corresponding penetration

[0015] Step 1.5, take multiple experimental groups P Li The arithmetic mean is P L P L This refers to the required compaction degree D at the engineering site. F The penetration depth per N hammer blows at a corresponding drop height H is used as the standard for on-site engineering testing.

[0016] Step 2: Based on the on-site testing standards determined in Step 1, conduct on-site testing using the aforementioned lightweight dynamic penetrometer. The steps are as follows:

[0017] Step 2.1: Determine and mark the locations of the testing points at the construction site according to the requirements;

[0018] Step 2.2: For a single detection point, the lightweight dynamic penetrometer is used for detection to obtain the penetration depth per N hammer blows at a drop distance H, denoted as P. F ;

[0019] Step 2.3, when P F Not greater than P L If the compaction at a given point is deemed satisfactory, it is deemed unsatisfactory.

[0020] Step 2.4: Repeat steps 2.2 to 2.3 to complete the detection of all detection points.

[0021] In the above technical solution, the process of using the lightweight dynamic penetrometer to detect and obtain the penetration depth per N hammer blows at a drop distance H is as follows:

[0022] (1) Place the orifice stool firmly at the target position, insert the probe of the probe device through the through hole in the center of the stool surface and stand it on the target to be measured. The elastic support wheel unit of the orifice stool provides elastic rolling support for the probe, so that the probe is in the center of the through hole. Then, with reference to the plumb bob, manually adjust the probe position and then adjust the probe to a vertical state.

[0023] (2) Pre-strike: Raise the drop hammer and strike the enlarged section of the probe rod 1-3 times as a pre-strike to allow the probe to be initially placed into the target soil and stabilized therein.

[0024] (3) After the pre-strike is completed, adjust the position of the adjustable positioning ring and set the required drop distance H of the hammer. The reading of the second scale corresponding to the bottom of the adjustable positioning ring is the required drop distance H of the hammer. Then, align the top of the reading probe with the position of the first scale of the probe rod and use it as the reading of the first scale, which is recorded as p1.

[0025] (4) Start the formal power penetration test: Raise the drop hammer to the bottom of the adjustable positioning ring, so that the drop hammer hits the enlarged section on the probe rod N times at the required drop distance H, then stop hitting, and read the reading of the first section of the scale on the probe rod at this time, and record it as p2;

[0026] (5) According to the formula P = p2 - p1, the penetration depth P of each N hammer blows under the set drop distance H in this test is obtained.

[0027] In the above technical solution, the diameter of the probe rod is 20-30mm.

[0028] In the above technical solution, the probe is conical with a cone angle of 50-70 degrees.

[0029] In the above technical solution, the diameter of the expanded section is 55-60mm.

[0030] In the above technical solution, the mass of the falling hammer is 6-8 kg.

[0031] In the above technical solution, the second scale is marked upwards from 0mm on the top surface of the expanded diameter section, with a maximum marking size of 600mm.

[0032] In the above technical solution, the diameter of the through hole is 45-50mm.

[0033] In the above technical solution, the reading probe uses an inclined elastic metal plate, the bottom of which is fixed to the bench surface by bolts, and the top of which is used to point to the first scale on the probe rod. The position it points to is used as the reading of the first scale, so as to accurately read the penetration depth of the probe rod device during the test.

[0034] In the above technical solution, the number of elastic support wheel units is 3-4.

[0035] In the above technical solution, the elastic support wheel unit includes a mounting groove, a support rod, a slider, a roller, and a spring. The mounting groove is fixedly disposed on the stool surface and is arranged radially along the through hole on the stool surface. The slider is slidably mounted in the mounting groove and can slide radially along the through hole. The tail end of the support rod is fixedly connected to the slider, and the front end of the support rod is mounted with a roller. The spring is installed at the tail end of the slider to provide elastic force to the slider in the direction of the center of the through hole, so that the roller can elastically contact the probe. In this way, the rollers of the multiple elastic support wheel units evenly distributed in a circle can provide elastic rolling support for the probe penetrating the through hole.

[0036] The advantages and beneficial effects of this invention are as follows:

[0037] (1) Compared with conventional sand-filling method, water-filling method and ring cutter method, the method of the present invention is simple to operate, fast to detect, and causes little damage to the compacted subgrade. After the field test begins, no indoor test is required, and the subgrade compaction degree can be obtained on site.

[0038] (2) The lightweight dynamic penetration test device used in this invention is engraved with two millimeter-level scales (i.e., the first scale and the second scale), and a hole stool with a reading elastic metal sheet is used instead of the easily deformable roadbed hole as the measurement reference point, which makes the penetration measurement more accurate, and therefore the compaction test result is more accurate.

[0039] (3) The lightweight power penetrometer of the present invention can conveniently and accurately adjust the drop distance required for the hammer during the test by means of an adjustable positioning ring combined with a second scale. During the test, the hammer can be manually raised to the bottom of the adjustable positioning ring (i.e., accurately positioned) and then allowed to fall naturally to strike the expanded diameter section of the probe rod, thereby generating a downward impact force on the entire probe rod. This method can ensure that the drop distance of the hammer is the same each time and is very convenient to operate.

[0040] (4) The lightweight power penetration test device of this invention has multiple elastic support wheel units on the orifice stool, which are evenly distributed around the through hole in a circle to provide elastic rolling support for the probe rod. During the test, the probe and the probe rod need to penetrate the through hole of the stool surface from top to bottom so that the probe can be inserted into the target to be tested. During the process of penetrating the through hole, since the maximum diameter of the probe is larger than the diameter of the probe rod, the multiple elastic support wheel units can be spread open so that the probe can penetrate the through hole. In addition, during the test, the multiple elastic support wheel units can provide good elastic rolling support for the probe rod, so that the probe rod is in the center position of the through hole. At the same time, since the front end of the elastic support wheel unit uses a roller to make rolling contact with the probe rod, the friction force on the probe rod is very small and will not affect the hammering effect. In addition, a plumb bob is installed on the bottom of the orifice stool as a reference for the verticality of the probe rod. Under the combined action of the plumb bob and the aforementioned elastic support wheel unit, the verticality of the probe rod can be adjusted (since the diameter of the through hole is larger than the diameter of the probe rod, and multiple elastic support wheel units provide elastic rolling support for the probe rod, the verticality of the probe rod is adjustable; and since the support part of the probe rod by multiple elastic support wheel units is stably located at the center of the through hole, it is only necessary to adjust the position of the probe at the bottom end of the probe rod to adjust the verticality of the probe rod with reference to the plumb bob, so that the probe rod is kept at the required verticality).

[0041] (5) The lightweight power penetration device used in this invention is lighter and reduces the labor intensity of the testing personnel. The weight of the hammer is about 7.5kg, and the penetration depth produced by each hammer blow is small, which also reduces the probability that the probe penetrates the base layer of the test road and enters the base layer of the non-test road.

[0042] (6) Compared with other methods of using dynamic penetration testing as a detection means, the general method records the number of blows N required for each specific penetration depth, such as 30cm. However, when the actual number of blows is N, the penetration depth is often greater than 30cm, which will cause measurement error due to over-penetration. The method of the present invention uses the penetration depth corresponding to a specific drop distance and a specific number of hammer blows (generally 10 to 15) as the measurement index, thus avoiding the error caused by over-penetration. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the probe device in this invention.

[0044] Figure 2 This is a top view of the perforated stool in this invention.

[0045] Figure 3 This is a side view of the perforated stool in this invention.

[0046] Figure 4 This is a partially enlarged structural diagram of the orifice stool in this invention.

[0047] Figure 5 The diagram shown is a schematic representation of the detection status of the lightweight dynamic penetrometer in this invention.

[0048] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0049] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments.

[0050] A lightweight powered penetrometer includes a probe assembly and an orifice holder.

[0051] The probe device includes a drop hammer 1, a probe rod 2, a probe 4, and an adjustable positioning ring 5. See appendix below. Figure 1 Its structure will be described in detail.

[0052] A probe 4 is installed at the bottom of the probe rod 2. The probe rod 2 has a diameter of 25mm, and the probe 4 is conical with a maximum diameter of 40mm and a cone angle of 60 degrees. An expansion section 21 with a diameter of 55mm is fixedly installed in the middle of the probe rod 2. The drop hammer 1 is slidably mounted on the probe rod 2 above the expansion section 21. The mass of the drop hammer 1 is preferably 7.5kg. When the drop hammer 1 is lifted, it falls freely along the probe rod 2 and strikes the expansion section 21, thereby generating a downward impact force on the entire probe rod 2.

[0053] Two scales are set on the probe rod 2. The first scale 31 is set on the section of probe rod 2 below the enlarged diameter section 21. During the test, it is used to indicate the depth of the probe rod 2 penetrating into the roadbed (it needs to be used in conjunction with the reading probe 7 on the orifice stool 6, which will be described in detail later). The second scale 32 is set on the section of probe rod 2 above the enlarged diameter section 21. The second scale 32 starts from 0mm on the top surface of the enlarged diameter section 21 and marks upwards along the rod section, with a maximum marking size of 500mm. The function of the second scale 32 is to indicate the drop distance of the drop hammer 1 (i.e., to indicate the height from which the drop hammer 1 falls) during the test.

[0054] An adjustable positioning ring 5 is installed on the probe rod 2 above the expanded diameter section 21. The adjustable positioning ring 5 is fitted onto the probe rod 2, and a tightening screw 51 is installed on the adjustable positioning ring 5. By adjusting the tightening screw 51, the positioning position of the adjustable positioning ring 5 on the probe rod 2 can be adjusted. Then, in conjunction with the second scale 32, the drop distance of the hammer 1 during the test can be determined. That is, during the test, the adjustable positioning ring 5 is first adjusted to the drop distance position required for the hammer 1 to fall, referring to the second scale 32 (the reading of the second scale 32 corresponding to the bottom surface of the adjustable positioning ring 5 is the drop distance position required for the hammer 1 to fall). Then, during the test, the hammer 1 is manually raised to the bottom surface of the adjustable positioning ring 5 and then falls naturally, striking the expanded diameter section 21, thereby generating a downward impact force on the entire probe rod 2.

[0055] The orifice holder 6 is used in conjunction with the probe device; see appendix below. Figure 2 - Appendix Figure 4 The structure and function of the 6-hole stool are described in detail.

[0056] The perforated stool 6 includes a stool surface 61 and several stool legs 62 supporting the stool surface 61, and is made of lightweight, high-strength aluminum alloy. A through hole 63 is provided in the center of the stool surface, and the diameter of the through hole 63 is 45-50mm.

[0057] A reading probe 7 is installed on the seat surface 61 of the orifice stool 6. The reading probe 7 is an inclined elastic metal sheet, the bottom of which is fixedly installed on the seat surface 61 by bolts 8, and the top of which is used to point to the first section of the scale 31 on the probe rod 2. The position it points to is used as the reading of the first section of the scale 31, so as to accurately read the penetration depth of the probe device during the test.

[0058] The seat surface 61 of the orifice stool 6 is provided with multiple elastic support wheel units 9. Preferably, there are 3-4 elastic support wheel units 9, evenly distributed circumferentially around the through hole 63. During testing, they are used to provide elastic rolling support for the probe 2. For details, please refer to the appendix. Figure 4The elastic support wheel unit 9 includes a mounting groove 91, a support rod 92, a slider 93, a roller 94, and a spring 95. The mounting groove 91 is fixedly disposed on the stool surface 61 and is arranged radially along the through hole 63 on the stool surface 61. The slider 93 is slidably mounted in the mounting groove 91 and can slide radially along the through hole 63. The tail end of the support rod 92 is fixedly connected to the slider 93, and the front end of the support rod 92 is mounted with the roller 94. The spring 95 is installed at the tail of the slider 93 and is used to provide elastic force to the slider 93 in the direction of the center of the through hole 63, so that the roller 94 can elastically contact the probe 2. In this way, the rollers 94 of the multiple elastic support wheel units 9, which are evenly distributed in a circle, can provide elastic rolling support for the probe 2 that penetrates the through hole 63. During the test, probe 4 and probe rod 2 need to penetrate the through hole 63 of the bench surface from top to bottom so that probe 4 can be inserted into the roadbed to be tested. During the penetration of the through hole 63, since the maximum diameter of probe 4 is larger than the diameter of probe rod 2, multiple elastic support wheel units 9 can be spread out, allowing probe 4 to penetrate the through hole. Furthermore, during the test, the multiple elastic support wheel units 9 can provide good elastic rolling support for probe rod 2, keeping probe rod 2 at the center of the through hole 63 (see Appendix). Figure 5 ).

[0059] A plumb bob 10 is connected to the bottom surface of the seat surface 61 of the orifice bench 6. During the test, it is used as a reference for the verticality of the probe rod 2. During the test, after the probe 4 and the probe rod 2 pass through the through hole 63 of the seat surface, the position of the probe 4 on the roadbed is manually adjusted with reference to the plumb bob 10, thereby adjusting the verticality of the probe rod 2. (Since the diameter of the through hole 63 is larger than the diameter of the probe rod 2, and multiple elastic support wheel units 9 provide elastic rolling support for the probe rod 2, the verticality of the probe rod 2 is adjustable; and since the support part of the multiple elastic support wheel units 9 for the probe rod 2 is stably located at the center of the through hole, it is only necessary to adjust the position of the probe 4 at the bottom of the probe rod 2 to adjust the verticality of the probe rod 2 with reference to the plumb bob 10, and keep the probe rod 2 at the required verticality.)

[0060] I. The basic process of testing using the above-mentioned lightweight powered penetrometer is as follows:

[0061] (1) Place the orifice stool 6 firmly in the target position, and place the probe 4 and probe 2 of the probe device through the through hole 63 in the center of the stool surface on the target to be measured. The elastic support wheel unit 9 on the orifice stool 6 provides good elastic rolling support for the probe 2, so that the probe 2 is in the center of the through hole 63. Then, with reference to the plumb bob 10, manually adjust the position of the probe 4, and then adjust the probe 2 to a vertical state.

[0062] (2) Pre-strike: Raise the drop hammer 1 and hammer the enlarged diameter section 21 of the probe rod 1-3 times as a pre-strike of the probe rod, so that the probe 4 is initially placed in the target soil and stabilized therein.

[0063] (3) After the pre-strike is completed, adjust the position of the adjustable positioning ring 5 and set the required drop distance H of the hammer 1. The reading of the bottom surface of the adjustable positioning ring 5 corresponding to the second scale 32 is the required drop distance H of the hammer 1. Then, align the top of the reading probe 7 with the position of the first scale 31 of the probe rod 2 and use it as the reading of the first scale 31, which is recorded as p1.

[0064] (4) Start the formal power penetration test: Raise the drop hammer 1 to the bottom of the adjustable positioning ring 5, so that the drop hammer 1 hits the enlarged section on the probe rod 2 N times at the required drop distance H, then stop hitting, and read the reading of the first section of the scale 31 on the probe rod 2 again, and record it as p2.

[0065] (5) According to the formula P = p2 - p1, the penetration depth P of each N hammer blows under the set drop distance H in this test is obtained.

[0066] II. The process of using the aforementioned lightweight dynamic cone penetration test device to conduct indoor tests to determine the on-site inspection standards is as follows (the purpose is to conduct indoor lightweight dynamic cone penetration tests before on-site inspections to obtain the compaction degree D required for the roadbed at the engineering site). F The corresponding penetration depth P per N hammer blows at a set drop distance H. L (as a standard for on-site engineering testing):

[0067] (1) Take soil samples identical to those from the roadbed construction site and prepare specimens with a compaction degree of D in test pits with a diameter of not less than 300 mm and a depth of not less than 400 mm. The compaction degree D required at the construction site is the same as that required at the construction site. F Approximately equal to;

[0068] (2) The soil sample in the test pit was tested according to the basic process of the light dynamic penetrometer described above, and the penetration depth P was obtained for each N hammer blows at the set drop distance H.

[0069] (3) Repeat steps (1) to (2) and conduct no less than three sets of tests. In each set of tests, the compaction degree D is greater than or less than the compaction degree D required on site. F Each sample shall be no less than one;

[0070] (4) Plot the compaction degree D-penetration degree P curves in groups, and deduce the relationship between D and the compaction degree P in this group of tests. F The corresponding penetration degree P Li ;

[0071] (5) Take multiple groups of experiments P Li The arithmetic mean is P L P L This refers to the required compaction degree D at the engineering site. FThe penetration depth per N hammer blows at a corresponding drop height H is used as the standard for on-site engineering testing.

[0072] III. Based on the above-determined on-site testing standards (i.e., the required compaction degree D at the engineering site) F The penetration depth P per N hammer blows at a corresponding drop distance H L The above-mentioned lightweight dynamic penetration test device was used for on-site testing. The testing process is as follows:

[0073] (1) Determine the location of each testing point at the project site and mark it according to the requirements;

[0074] (2) For a single test point, the test is carried out according to the basic process of the above-mentioned light dynamic penetrometer to obtain the penetration depth per N hammer blows at a drop distance H, denoted as P. F ;

[0075] (3) When P F Not greater than P L If the compaction at a given point is deemed satisfactory, it is deemed unsatisfactory.

[0076] (4) Repeat steps (2) to (3) to complete the detection of all detection points.

[0077] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A rapid method for detecting the compaction degree of roadbed based on dynamic cone penetration test, characterized in that: The method employs a lightweight powered penetrometer, which consists of a probe rod and a borehole holder. The probe device includes a drop hammer, a probe rod, a probe, and an adjustable positioning ring. The probe is mounted at the bottom end of the probe rod, and an enlarged diameter section is fixedly installed in the middle of the probe rod. The drop hammer is slidably fitted onto the probe rod section above the enlarged diameter section. Two scales are provided on the probe rod: the first scale, located on the probe rod section below the enlarged diameter section, indicates the depth of penetration; the second scale, located on the probe rod section above the enlarged diameter section, indicates the drop distance of the drop hammer. An adjustable positioning ring is installed on the probe rod section above the enlarged diameter section, fitted onto the probe rod, and a tightening screw is provided on the adjustable positioning ring. By adjusting this tightening screw, the positioning position of the adjustable positioning ring on the probe rod can be adjusted, thereby determining the drop distance of the drop hammer during the test in conjunction with the second scale. The orifice stool is used in conjunction with the probe device. The orifice stool includes a stool surface and stool legs supporting the stool surface. A through hole is provided in the center of the stool surface for the probe to pass through. A reading probe is provided on the stool surface to assist in reading the reading of the first section of the scale on the probe. Multiple elastic support wheel units are provided on the stool surface, evenly distributed in a circle around the through hole, for elastic rolling support of the probe. A plumb bob is connected to the bottom surface of the orifice stool surface to serve as a reference for the verticality of the probe. The following is a rapid method for detecting the compaction degree of roadbed: Step 1: Before on-site testing, conduct indoor tests using the aforementioned lightweight dynamic cone penetrometer to obtain the compaction degree D required for the roadbed. F The penetration depth P per N hammer blows at a corresponding drop distance H L This will serve as the standard for on-site engineering testing; the process includes the following steps: Step 1.1: Take soil samples identical to those from the roadbed construction site and prepare specimens with a compaction degree of D in the test pit. The compaction degree D is the same as the required compaction degree D at the construction site. F Approximately equal to; Step 1.2: The soil sample in the test pit is tested using the aforementioned lightweight dynamic penetrometer to obtain the penetration depth P per N hammer blows at a set drop distance H; Step 1.3: Repeat steps 1.1 to 1.2 above, and conduct no less than three sets of tests. In each set of tests, the compaction degree D is greater than or less than the required compaction degree D on site. F Each sample shall be no less than one; Step 1.4: Plot the compaction degree D-penetration degree P curves in groups, and deduce the relationship between D and compaction degree in this group of tests. F Corresponding penetration Step 1.5, take multiple sets of tests The arithmetic mean is P L P L This refers to the required compaction degree D at the engineering site. F The penetration depth per N hammer blows at a corresponding drop height H is used as the standard for on-site engineering testing. Step 2: Based on the on-site testing standards determined in Step 1, conduct on-site testing using the aforementioned lightweight dynamic penetrometer. The steps are as follows: Step 2.1: Determine and mark the locations of the testing points at the construction site according to the requirements; Step 2.2: For a single detection point, the lightweight dynamic penetrometer is used for detection to obtain the penetration depth per N hammer blows at a drop distance H, denoted as P. F ; Step 2.3, when P F Not greater than P L If the compaction at a given point is deemed satisfactory, it is deemed unsatisfactory. Step 2.4: Repeat steps 2.2 to 2.3 to complete the detection of all detection points.

2. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The process of obtaining the penetration depth per N hammer blows at a drop distance H using the aforementioned lightweight dynamic penetrometer is as follows: (1) Place the orifice stool firmly at the target position, insert the probe of the probe device through the through hole in the center of the stool surface and stand it on the target to be measured. The elastic support wheel unit of the orifice stool provides elastic rolling support for the probe, so that the probe is in the center of the through hole. Then, with reference to the plumb bob, manually adjust the probe position and then adjust the probe to a vertical state. (2) Pre-strike: Raise the drop hammer and strike the enlarged section of the probe rod 1-3 times as a pre-strike to allow the probe to be initially placed into the target soil and stabilized therein. (3) After the pre-strike is completed, adjust the position of the adjustable positioning ring and set the required drop distance H of the hammer. The reading of the second scale corresponding to the bottom of the adjustable positioning ring is the required drop distance H of the hammer. Then, align the top of the reading probe with the position of the first scale of the probe rod and use it as the reading of the first scale, which is recorded as p1. (4) Start the formal power penetration test: Raise the drop hammer to the bottom of the adjustable positioning ring, so that the drop hammer hits the enlarged section on the probe rod N times at the required drop distance H, then stop hitting, and read the reading of the first section of the scale on the probe rod at this time, and record it as p2; (5) According to the formula P = p2 - p1, the penetration depth P of each N hammer blows under the set drop distance H in this test is obtained.

3. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The probe diameter is 20-30mm.

4. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The probe is conical with a cone angle of 50-70 degrees.

5. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The diameter of the expanded section is 55-60mm.

6. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The mass of the falling hammer is 6-10 kg.

7. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The second scale is marked upwards from 0mm on the top surface of the expanded diameter section along the pole segment.

8. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The reading probe uses an inclined elastic metal plate, the bottom of which is fixed to the bench surface by bolts, and the top of which is used to point to the first scale on the probe rod. The position it points to is the reading of the first scale.

9. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The number of elastic support wheel units is 3-4.

10. The rapid detection method for subgrade compaction based on dynamic penetration test as described in claim 1, characterized in that: The elastic support wheel unit includes a mounting groove, a support rod, a slider, a roller, and a spring. The mounting groove is fixedly disposed on the bench surface and is arranged radially along the through hole on the bench surface. The slider is slidably mounted in the mounting groove and can slide radially along the through hole. The tail end of the support rod is fixedly connected to the slider, and the front end of the support rod is mounted with a roller. The spring is installed at the tail end of the slider to provide elastic force to the slider in the direction of the center of the through hole, so that the roller can elastically contact the probe. In this way, the rollers of the multiple elastic support wheel units evenly distributed in a circle can provide elastic rolling support for the probe penetrating the through hole.

Images