A standard penetration test apparatus for the bottom of a hole

Abstract

This invention discloses a novel standard penetration test (SPT) device for the bottom of a borehole. A standard-sized penetrator is pre-driven 15cm into the borehole from the bottom elevation. A worm gear lifting module drives a claw connected to the worm gear downwards. When the claw contacts the upper part of the mandrel, it opens to grasp the mandrel. The ground controller receives a signal through a pressure sensor and issues a command to instruct the worm gear lifting mechanism to drive the worm to rise. When the worm rises 76cm, the upper part of the claw contacts the upper part of the outer shell, and the claw opens to release the mandrel. This process is repeated to lift the 63.5kg standard mandrel and strike the hammer pad, continuing to drive 30cm. The ground controller records the corresponding number of blows to determine the soil properties. This invention enables standardized and automated hammering at the bottom of the borehole, avoiding the problem of energy loss in SPT.

Description

Technical Field

[0001] This invention belongs to the field of engineering drilling testing technology, and specifically relates to a novel standard penetration test device for the bottom of a hole. Background Technology

[0002] The Standard Penetration Test (SPT) involves dropping a 63.5 kg center hammer freely along the drill rod at a drop height of 76 cm. A standard-sized penetrator is driven 15 cm into the borehole from the bottom elevation, and then driven another 30 cm, with the blow count recorded. This data is used to determine the soil properties and is a common in-situ testing method in geotechnical engineering investigations. Current SPT methods rely on manual operation, with the hammer being manually pulled from the ground and the blow count and penetration depth being manually recorded.

[0003] Currently, in the field of engineering geological exploration, the burial depth of the strata for standard penetration tests (SPTs) is generally less than 20m, and the maximum depth for SPT rod length correction specified in relevant domestic standards is 21m. Furthermore, the SPT uses a drill rod lowered into the hole to transfer the impact energy of the SPT hammer above ground to the SPT at the bottom of the hole. The longer the drill rod, the greater the impact energy loss, and the resulting test data cannot represent the true characteristics of deep strata, rendering it unusable.

[0004] Standard penetration testing (SPT) at the bottom of the borehole can fundamentally solve the problem of energy transfer loss in SPT. Controlling the drop height of the hammer at 76 cm is one of the key technologies for implementing SPT. As the testing device is driven deeper, the absolute position of the hammer release varies each time. Manual distance control is not applicable to borehole bottom testing. To achieve deep SPT, it is urgent to develop a standard penetration testing device suitable for the bottom of the borehole. The most critical issue is how to achieve standardized and automated hammering at the bottom of the borehole. Summary of the Invention

[0005] This invention provides a novel standard hole bottom penetration test apparatus to solve the problems existing in the prior art.

[0006] To solve the above problems, the technical solution provided by the present invention is as follows:

[0007] This invention provides a novel standard hole-bottom penetration test device, including a penetration head (1), a penetrator (2), a connector (3), a hammer pad (4), a through hammer (5), a shell (6), a claw seat (7), a cable (8), a ground controller (9), a worm gear lifting mechanism (10), a worm (11), a claw (12), a spring support rod (13), a spring (14), and a central hollow rod (15);

[0008] The upper and lower ends of the penetrator (2) are respectively connected to the penetrator head (1) and the connector head (3) by threads. The upper end of the connector head (3) is connected to the lower end of the hammer pad (4) by threads. The upper end of the hammer pad (4) is connected to the outer shell (6) by threads. The upper end of the hammer pad (4) is connected to the central hollow rod (15) by threads. A distance measuring sensor is provided inside the hammer pad (4). The distance measuring sensor is connected to the worm gear lifting mechanism (10) by a wire passing through the hollow cavity inside the central hollow rod (15).

[0009] The upper end of the central hollow rod (15) passes through the hollow cavity inside the worm gear (11) to provide a channel for the circuit; the hammer (5) and the central hollow rod (15) are configured with a clearance fit; the upper part of the claw seat (7) is connected to the worm gear (11) by a thread, and the central hollow rod (15) enters the central cavity inside the worm gear (11) through the radial cavity in the center of the claw seat (7); two claws (12) are symmetrically arranged on the claw seat (7), and the spring support rod (13) is connected between the two claws (12). A spring (14) is wound on the spring support rod (13). The two claws (12) are closed to grab the hammer (5), and the two claws (12) are open to release the hammer (5); the upper end of the cable (8) is connected to the ground controller (9), and the lower end of the cable (8) is connected to the worm gear lifting mechanism (10) to provide lifting force for the entire experimental device.

[0010] In a preferred embodiment of the present invention, the weight of the mandrel (5) is 63.5 kg.

[0011] In a preferred embodiment of the present invention, the worm gear lifting mechanism (10) is externally connected to the outer shell (6) via threads.

[0012] In a preferred embodiment of the present invention, the penetrator (2) is driven 15cm into the borehole from the pre-drilled bottom elevation.

[0013] In a preferred embodiment of the present invention, the worm gear lifting mechanism (10) is used to drive the claw (12) connected to the worm gear to move downward; when the claw (12) contacts the upper part of the hammer (5), the claw (12) opens to grab the hammer (5), and the ground controller (9) obtains a signal through the pressure sensor and issues a command to direct the worm gear lifting mechanism (10) to drive the worm (11) to rise; when the worm (11) rises 76cm, when the upper part of the claw (12) contacts the upper part of the outer shell (6), the claw (12) opens to release the hammer (5), and so on, lifting the 63.5kg hammer (5) to strike the hammer pad (4) and continue to strike 30cm. The ground controller (9) records the corresponding number of blows and judges the properties of the soil accordingly.

[0014] Compared with the prior art, the present invention provides a novel standard penetration test device for the bottom of the hole, which has the following beneficial effects: (1) The present invention transfers the loading method of the standard penetration test from the ground to the bottom of the hole, avoiding the attenuation and verification of the load when it is transmitted to the bottom of the hole through the drill rod, and can obtain high-precision test parameters. (2) The present invention can realize standardized and automated hammering at the bottom of the hole, avoiding the problem of loss of standard penetration capability transmission. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments or prior art, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a novel standard hole penetration test apparatus provided in an embodiment of this application.

[0017] Figure 2 This is a partial schematic diagram of the claw mechanism of a novel hole bottom standard penetration test device provided in an embodiment of this application.

[0018] Explanation of reference numerals in the attached drawings: 1. Penetrator head; 2. Penetrator; 3. Connecting rod; 4. Hammer pad; 5. Through hammer; 6. Housing; 7. Claw seat; 8. Cable; 9. Controller; 10. Worm gear lifting mechanism; 11. Worm; 12. Claw; 13. Spring support rod; 14. Spring; 15. Central hollow rod. Detailed Implementation

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0020] like Figure 1 and Figure 2 As shown, this embodiment of the invention provides a novel standard hole-bottom penetration test device, including a penetration head 1, a penetration device 2, a connector 3, a hammer pad 4, a through hammer 5, a housing 6, a claw seat 7, a cable 8, a ground controller 9, a worm gear lifting mechanism 10, a worm 11, a claw 12, a spring support rod 13, a spring 14, and a central hollow rod 15.

[0021] The penetrator 2 is a symmetrical device with its upper and lower ends connected to the penetrator head 1 and the connector head 3 respectively via threads. The upper end of the connector head 3 is connected to the lower end of the hammer pad 4 via threads. The upper external end of the hammer pad 4 is connected to the outer shell 6 via threads, and the upper internal end of the hammer pad 4 is connected to the central hollow rod 15 via threads. A distance measuring sensor is installed inside the hammer pad 4, and the distance measuring sensor is connected to the worm gear lifting mechanism 10 through an electric wire passing through the hollow cavity inside the central hollow rod 15.

[0022] The central hollow rod 15 has a hollow internal structure, providing a channel for the circuit. The upper end of the central hollow rod 15 passes through the hollow cavity inside the worm gear 11. The hammer 5 and the central hollow rod 15 are fitted with a clearance fit, which does not affect the free fall of the hammer 5. The upper part of the claw seat 7 is threadedly connected to the worm gear 11. The central hollow rod 15 enters the central cavity inside the worm gear 11 through the radial cavity in the center of the claw seat 7. Two claws 12 are symmetrically arranged on the claw seat 7, and a spring support rod 13 connects the two claws 12. A spring 14 is wound on the spring support rod 13. The two claws 12 close to grasp the hammer 5, and open to release the hammer 5. The upper end of the cable 8 is connected to the ground controller 9, providing power to the ground controller 9. The ground controller 9 is connected to the entire experimental device below via the cable 8. The lower end of the cable 8 is connected to the worm gear lifting mechanism 10, providing lifting force for the entire experimental device.

[0023] The weight of the hammer 5 in this embodiment is 63.5 kg. The worm gear lifting mechanism 10 is externally connected to the outer casing 6 via threads. The drill bit 2 is pre-driven 15 cm into the bottom of the self-drilled hole. The worm gear lifting mechanism 10 is used to drive the claw 12 connected to the worm gear to move downward. The working principle of a novel standard hole bottom penetration test device: The standard specification drill bit 2 is pre-driven 15 cm into the bottom of the self-drilled hole, and the worm gear lifting mechanism 10 drives the claw connected to the worm gear to move downward. When the claw 12 contacts the upper part of the hammer 5, the claw 12 opens to grasp the hammer 5. After the ground controller 9 receives the signal through the pressure sensor, it issues a command to direct the worm gear lifting mechanism 10 to drive the worm 11 to rise. When the worm 11 rises 76cm, the upper part of the claw 12 contacts the upper part of the outer shell 6, and the claw 12 opens to release the hammer 5. This process is repeated to lift the 63.5kg hammer 5 to strike the hammer pad 4 and continue to drive it in 30cm. The ground controller 9 records the corresponding number of blows to determine the properties of the soil.

[0024] The specific working steps of a novel standard penetration test apparatus for hole bottom are as follows:

[0025] Drill to the predetermined standard penetration test depth;

[0026] Before the test begins, the standard penetration test device is lowered to the bottom of the hole via cable 8.

[0027] After power is applied, the distance sensor installed at the center of the lower end of the hammer pad 4 measures the initial distance between the standard penetration test device and the test stratum, and sends this information back to the ground controller 9. The ground controller 9 sends a working command to the worm gear lifting mechanism 10, which starts working and drives the worm 11 to rotate and fall. The retrieval claw seat 7, which is fixedly connected to the worm 11, and its upper retrieval claw 12 fall simultaneously. When the retrieval claw 12 contacts the through hammer 5, the spring 14 in the retrieval claw seat 7 is compressed, the retrieval claw 12 opens, and grabs the through hammer 5. The pressure sensor installed in the worm gear lifting mechanism 10 transmits a signal to the ground controller 9, which then sends a command. The worm gear lifting mechanism 10 drives the worm 11, which in turn drives the retrieval claw seat 7 and its associated parts to move upward as a whole. When the worm 11 rises 76cm, the upper part of the retrieval claw 12 contacts the upper part of the outer casing 6, the retrieval claw 12 opens, the spring 14 extends, and the through hammer 5 falls freely to strike the hammer pad 4. When the distance sensor detects that the experimental device has penetrated 15cm into the ground, the device stops the pre-experiment work and records the number of hammer blows in the ground controller 9.

[0028] When the experiment officially begins, the ground controller 9 sends a command to the worm gear lifting mechanism 10. The worm gear lifting mechanism 10 starts working, driving the worm 11 to rotate and fall. The claw seat 7, which is fixedly connected to the worm 11, and its upper claw 12 fall simultaneously. When the claw 12 contacts the hammer 5, the spring 14 in the claw seat 7 is compressed, the claw 12 opens, and grabs the hammer 5. The pressure sensor installed in the worm gear lifting mechanism 10 transmits a signal to the ground controller 9. The ground controller 9 sends a command, and the worm gear lifting mechanism 10 drives the worm 11. The worm 11 drives the claw seat 7 and its associated parts to move upward as a whole. When the worm 11 rises 76cm, the upper part of the claw 12 contacts the upper part of the outer shell 6, the claw 12 opens, the spring 14 extends, and the hammer 5 falls freely to strike the hammer pad 4.

[0029] Repeating the above steps, when the distance sensor detects that the experimental device has penetrated 30cm into the test stratum, the controller 9 terminates the operation of the worm gear lifting mechanism 10, the device stops the experiment, and the number of hammer blows N is recorded in the ground controller 9. Simultaneously, when the number of hammer blows exceeds 50 but the penetration depth has not reached 30cm, the controller also issues a command to terminate the test, and the controller records the actual penetration depth. This depth is then converted into the corresponding number of hammer blows N for a standard penetration test with a penetration depth of 30cm using the formula.

[0030]

[0031] In the formula: N is the standard penetration hammer blow count, and Δs is the penetration depth at 50 blows.

[0032] Although the present invention has been disclosed above with reference to preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Those skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. A standard penetration test apparatus for the bottom of a hole, characterized in that, It includes a penetrator (1), a penetrator (2), a connector (3), a hammer pad (4), a through hammer (5), a housing (6), a claw seat (7), a cable (8), a ground controller (9), a worm gear lifting mechanism (10), a worm (11), a claw (12), a spring support rod (13), a spring (14), and a central hollow rod (15); The upper and lower ends of the penetrator (2) are respectively connected to the penetrator head (1) and the connector head (3) by threads. The upper end of the connector head (3) is connected to the lower end of the hammer pad (4) by threads. The upper end of the hammer pad (4) is connected to the outer shell (6) by threads. The upper end of the hammer pad (4) is connected to the central hollow rod (15) by threads. A distance measuring sensor is provided inside the hammer pad (4). The distance measuring sensor is connected to the worm gear lifting mechanism (10) by a wire passing through the hollow cavity inside the central hollow rod (15). The upper end of the central hollow rod (15) passes through the hollow cavity inside the worm gear (11) to provide a channel for the circuit; the hammer (5) and the central hollow rod (15) are configured with a clearance fit; the upper part of the claw seat (7) is connected to the worm gear (11) by a thread, and the central hollow rod (15) enters the central cavity inside the worm gear (11) through the radial cavity in the center of the claw seat (7); two claws (12) are symmetrically arranged on the claw seat (7), and the spring support rod (13) is connected between the two claws (12). A spring (14) is wound on the spring support rod (13). The two claws (12) are closed to grab the hammer (5), and the two claws (12) are open to release the hammer (5); the upper end of the cable (8) is connected to the ground controller (9), and the lower end of the cable (8) is connected to the worm gear lifting mechanism (10) to provide lifting force for the entire experimental device.

2. The standard penetration test apparatus for hole bottom according to claim 1, characterized in that, The weight of the hammer (5) is 63.5 kg.

3. The standard penetration test apparatus for hole bottom according to claim 2, characterized in that, The worm gear lifting mechanism (10) is externally connected to the outer casing (6) via threads.

4. The standard penetration test apparatus for hole bottom according to claim 3, characterized in that, The penetration tool (2) is driven 15cm into the borehole from the bottom elevation of the hole.

5. The standard penetration test apparatus for hole bottom according to claim 4, characterized in that, The worm gear lifting mechanism (10) is used to drive the claw (12) connected to the worm to move downward. When the claw (12) contacts the upper part of the hammer (5), the claw (12) opens to grab the hammer (5). After the ground controller (9) obtains the signal through the pressure sensor, it issues a command to direct the worm gear lifting mechanism (10) to drive the worm (11) to rise. When the worm (11) rises 76cm, when the upper part of the claw (12) contacts the upper part of the outer shell (6), the claw (12) opens to release the hammer (5). The 63.5kg hammer (5) is lifted and hammered on the hammer pad (4) in this way, and continues to be driven in 30cm. The ground controller (9) records the corresponding number of blows and judges the properties of the soil accordingly.

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