Underground pile foundation pile feeding and static load pile testing method and device

Abstract

The invention discloses an underground pile foundation pile feeding and static load pile testing method and device. The device comprises a telescopic pile feeding device and an automatic film laying device. The telescopic pile feeder comprises a pile head section, an automatic telescopic section and a connector section which are connected in sequence, the pile head section is used for being connected with a pile press and static load test equipment, the automatic telescopic section comprises a telescopic rod, and the connector section is used for being connected with a test pile; the automatic film paving device is matched with the telescopic pile feeding device, and the automatic film paving device is mounted on the connecting joint section of the telescopic pile feeding device. By means of the telescopic pile feeder and the automatic film laying device, the test pile is fed to the underground designed pile top elevation position under the condition that foundation pit excavation is not conducted, pile foundation detection can be directly conducted on the ground without lengthening the test pile to the ground, meanwhile, the influence of soil friction of the section from the designed pile top elevation position to the ground is eliminated as much as possible, and the pile foundation detection efficiency is improved. And the accuracy of pile foundation detection data is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of underground pile foundations, and in particular to a method and a device for delivering piles and performing static load testing of piles in underground pile foundations. Background Art

[0002] Before construction begins and the foundation pit is excavated, underground pile foundation testing can only be conducted on the ground. This means that during actual pile foundation testing, the length of the test pile must be extended to the ground, based on the designed pile top elevation. Technical specifications for building pile foundations indicate that the theoretically specified values for the ultimate vertical compressive and tensile bearing capacities of underground pile foundations require deducting the standard values for the lateral resistance between the extended test pile section and the soil, as well as the effect of the extended section's deadweight.

[0003] During the pile foundation inspection process, when the foundation pit is deep, the additional lateral resistance value generated by the extended section is large. Especially when conducting a single pile vertical pull-out static load test, there is a situation where the actual force on the test pile exceeds the bearing capacity of the pile body. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for delivering piles and performing static load testing of underground pile foundations, so as to obtain pile foundation parameters that meet actual engineering design without carrying out large-scale foundation pit excavation before construction work begins.

[0005] To achieve the above object, the technical solution provided by the present invention is:

[0006] A first aspect of the present application provides an apparatus for delivering piles and performing static load testing of piles in an underground pile foundation, comprising a retractable pile driver and an automatic membrane laying device;

[0007] The retractable pile driver comprises a pile head section, an automatic retractable section and a connecting joint section connected in sequence. The pile head section is used to connect to a pile driver and static load test equipment. The automatic retractable section comprises a retractable rod. The connecting joint section is used to connect to a test pile. The retractable pile driver is used to transport the test pile from the pile hole entrance to the designed pile top elevation below the ground.

[0008] The automatic film laying device is matched with the retractable pile driver. The automatic film laying device is installed on the connecting joint section of the retractable pile driver and is used to lay the friction-reducing film around the test piles transported to the designed pile top elevation below the ground. The laying position of the friction-reducing film is from the ground to the designed pile top elevation below the ground.

[0009] To optimize the above technical solutions, specific limitations also include:

[0010] The pile head section, the automatic telescopic section and the connecting joint section are detachably connected.

[0011] The automatic telescopic section has a built-in power supply, a power system, a controller and a signal transmission system. The power system provides kinetic energy for the telescopic rod to be extended and retracted. The controller is used to control the operation of the power supply and power system. The signal transmission system is used for remote control extension and retraction. The telescopic range of the automatic telescopic section is greater than the distance from the designed pile top elevation below the ground to the ground. The bearing capacity of the automatic telescopic section is greater than the maximum construction load during the pile driving process.

[0012] Furthermore, the connecting joint section includes a connecting plate, the middle part of the upper end of the connecting plate has an installation interface for connecting to the automatic telescopic section, several groups of support rod sleeves for installing the automatic film laying device are provided around the upper end of the connecting plate, and the lower end of the connecting plate has a fixing part for connecting to the test pile.

[0013] Furthermore, the automatic film laying machine includes a film laying machine support rod, a film laying machine roll film shaft and a film pressing roller, and the film laying machine support rod is correspondingly installed on the support rod sleeve; the film laying machine roll film shaft is supported on the film laying machine support rod, and the film laying machine roll film shaft is installed with a friction-reducing film roll; a film pressing roller is provided on the side of the film laying machine roll film shaft, and the film pressing roller is used to press the roll film onto the side wall inside the pile hole passed through when the pile is delivered.

[0014] Furthermore, the film pressing roller includes a connecting vertical rod and a film pressing cross rod, and the connecting vertical rod connects the film pressing cross rod to the film laying device film winding shaft; the end of the connecting vertical rod is hook-shaped, which is hooked on the film laying device film winding shaft, and a return spring is provided on the film laying device support rod, one end of the return spring is connected to the film laying device support rod, and the other end is connected to the connecting vertical rod; the film pressing cross rod is used for laying and pressing friction-reducing film.

[0015] Furthermore, rollers are installed in sections on the entire rod of the film pressing crossbar, and the friction-reducing film bypasses the rollers and is pressed against the side wall inside the pile hole.

[0016] The automatic film laying device is provided with four symmetrical groups, and correspondingly, the support rod sleeves connecting the joint sections are also provided with four groups.

[0017] A second aspect of the present application provides a method for delivering piles and performing static load testing of piles in an underground pile foundation, comprising the following steps:

[0018] S1: Drill pile holes at the test pile points;

[0019] S2: Connect the test pile to the connecting joint section of the retractable pile driver, and install an automatic membrane spreading device on the connecting joint section of the retractable pile driver;

[0020] S3: The retractable pile driver is connected to the pile driver, and the test pile is transported from the pile hole entrance to the designed pile top elevation below the ground through the retractable pile driver. During the transportation, the side wall of the pile hole is covered with anti-friction film by the automatic film laying device.

[0021] S4: Check the verticality of the retractable pile driver and the test pile to ensure that they meet the vertical requirements;

[0022] S5: Conduct static load pile test.

[0023] Furthermore, during operation, the pile driver starts to drive the pile by holding the pile head section of the retractable pile driver through the pile clamp. The pile is driven into the pile to a depth of h at a time, and the automatic retractable section of the pile driver is extended by the distance h at a time. This operation of first driving into the pile and then extending the pile is repeated until the top of the test pile is pressed to the designed pile top elevation.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention provides a method and device for driving piles and performing static load test piles for an underground pile foundation. The device comprises a retractable pile driver and a matching automatic film spreading device. The retractable pile driver is divided into three functional sections from top to bottom, namely: a pile head section, an automatic telescopic section and a connecting joint section. The pile driver connects to the test pile and delivers it to a specified elevation. The automatic film spreading device mainly comprises a film spreading device support rod, a film pressing roller and a film winding shaft, which are assembled and installed in the connecting joint section of the pile driver. When the test pile is pressed down, the friction-reducing film is fully spread along the pile hole to ensure that the test pile and the pile driver are not in direct contact with the soil in the section from the designed pile top elevation to the ground.

[0026] The present invention uses a retractable pile delivery device and an automatic membrane laying device to deliver the test pile to the underground designed pile top elevation without excavating the foundation pit. The pile foundation test can be carried out directly on the ground without extending the test pile to the ground. At the same time, the influence of soil friction from the designed pile top elevation to the ground is eliminated as much as possible, thereby improving the accuracy of the pile foundation test data.

[0027] Traditional static load pile testing methods require extending the test pile to the ground for testing. However, due to frictional interference between the extended pile section and the surrounding soil, the test data requires additional corrections and can result in significant errors, potentially causing the total load to exceed the pile's actual bearing capacity. This solution uses a retractable pile driver to deliver the test pile directly to the designed underground elevation, eliminating the need to extend the pile section to the ground. Simultaneously, an automatic film applicator lays a friction-reducing film around the entire length of the pile, completely eliminating the interference from soil friction in the extended section. This improvement significantly improves the accuracy of bearing capacity test data while effectively avoiding the risk of pile overload caused by additional frictional resistance during the pile test.

[0028] This method can be adapted to various conventional equipment under the existing construction level, including various types of pile drivers and pile foundation static load test equipment, and has the advantages of easy installation and reusability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 (a) is the drilling rig forming hole in the present invention, Figure 1Middle (b) is a schematic diagram of the test pile connected to the retractable pile driver and the automatic film laying device in the present invention.

[0030] Figure 2 (c) is the present invention in which the test pile is pressed into place and the membrane is laid in the pile hole. Figure 2 Middle (d) is a schematic diagram of the test pile being pressed to the designed pile top elevation in the present invention.

[0031] Figure 3 It is a structural schematic diagram of an example of a retractable pile driver in one embodiment of the present invention.

[0032] Figure 4 It is a structural schematic diagram of an example of an automatic film laying device in one embodiment of the present invention.

[0033] Figure 5 It is a structural schematic diagram of the film pressing roller and return spring of the automatic film laying device in one embodiment of the present invention.

[0034] In the figure: 1-pile hole, 2-test pile, 3-retractable pile delivery device, 4-automatic film laying device, 301-pile head section, 302-automatic telescopic section, 303-connecting joint section, 3011-embedded steel plate on top of pile head section, 3012-reinforced concrete pile section of pile head section, 3013-embedded bolts on bottom of pile head section, 3021-connecting plate on top of telescopic section, 3022-telescopic main rod of telescopic section, 3023-connecting thread at bottom of telescopic section, 3031-threaded sleeve on top of connecting joint section, 3032-support rod sleeve, 3033-connecting plate, 401-film laying device support rod, 402-film winding shaft, 403-film pressing roller, 404-film winding, 405-return spring, 4031-connecting vertical rod, 4032-film pressing cross rod, 4033-film pressing roller. DETAILED DESCRIPTION

[0035] The above contents of the present invention are further described in detail below in the form of specific implementation methods, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments. All technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0036] The orientation or position relationship is based on the relationship shown in the drawings and is only for the convenience of describing the present invention and simplifying the description. It does not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0037] The present invention provides a device for delivering piles and performing static load testing of piles in underground pile foundations. Figure 1 As shown, it includes a retractable pile driver 3 and an automatic film laying device 4.

[0038] The retractable pile driver 3 comprises a pile head section 301, an automatic retractable section 302, and a connecting joint section 303, which are connected in sequence. The pile head section 301 is used to connect to the pile driver and static load test equipment. The automatic retractable section 302 includes a retractable rod. The connecting joint section 303 is used to connect to the test pile 2. The retractable pile driver 3 is used to transport the test pile 2 from the entrance of the pile hole 1 to the designed pile top elevation below the ground.

[0039] The automatic film laying device 4 is provided in conjunction with the retractable pile driver 3. The automatic film laying device 4 is installed on the connecting joint section 303 of the retractable pile driver 3 and is used to lay the friction-reducing film around the test pile 2 transported to the designed pile top elevation below the ground. The laying position of the friction-reducing film is from the ground to the designed pile top elevation below the ground.

[0040] In some embodiments, the pile head section 301 , the automatic telescopic section 302 and the connection joint section 303 are detachably connected.

[0041] In some embodiments, the automatic telescopic section 302 has a built-in power supply, a power system, a controller, and a signal transmission system. The power system provides kinetic energy for the telescopic rod to be extended and retracted. The controller is used to control the operation of the power supply and the power system. The signal transmission system is used to perform remote telescopic extension. The telescopic range of the automatic telescopic section 302 is greater than the distance from the designed pile top elevation below the ground to the ground. Figure 2 As shown, the bearing capacity of the automatic telescopic section 302 is greater than the maximum construction load during the pile driving process.

[0042] The connecting joint section 303 includes a connecting plate 3033, the middle part of the upper end of the connecting plate 3033 has a mounting interface for connecting to the automatic telescopic section 302, and a plurality of support rod sleeves 3032 for installing the automatic film laying device 4 are arranged around the upper end of the connecting plate 3033. The lower end of the connecting plate 3033 has a fixing piece for connecting to the test pile 2, such as Figure 3 shown.

[0043] The automatic film laying device 4 includes a film laying device support rod 401, a film laying device film winding shaft 402 and a film pressing roller 403. Figure 4 As shown, the film laying device support rod 401 is correspondingly installed on the support rod sleeve 3032; the film laying device roll film shaft 402 is supported on the film laying device support rod 401, and the film laying device roll film shaft 402 is installed with a friction-reducing film roll film 404; the film laying device roll film shaft 402 is provided with a film pressing roller 403 on the side, and the film pressing roller 403 is used to press the roll film 404 onto the side wall of the pile hole 1 passed by when the pile is delivered, as shown in FIG. Figure 5 shown.

[0044] In some embodiments, the film pressing roller 403 includes a connecting vertical rod 4031 and a film pressing horizontal rod 4032, and the connecting vertical rod 4031 connects the film pressing horizontal rod 4032 to the film laying device film winding shaft 402; the end of the connecting vertical rod 4031 is hook-shaped, hooked on the film laying device film winding shaft 402, and a return spring 405 is provided on the film laying device support rod 401, one end of the return spring 405 is connected to the film laying device support rod 401, and the other end is connected to the connecting vertical rod 4031; the film pressing horizontal rod 4032 is used for laying and pressing the friction-reducing film.

[0045] In some embodiments, rollers are installed in sections on the entire film pressing crossbar 4032 , and the friction-reducing film bypasses the rollers and is pressed against the side wall inside the pile hole 1 .

[0046] In some preferred embodiments, the automatic film laying device 4 is provided with four symmetrical groups, and correspondingly, the support rod sleeves 3032 connecting the joint sections 303 are also provided with four groups.

[0047] The present invention also provides a method for delivering piles and performing static load testing of piles in an underground pile foundation, comprising the following steps:

[0048] S1: Drill pile hole 1 at the test pile point;

[0049] S2: Connect the test pile 2 to the connecting joint section 303 of the telescopic pile driver 3, and install the automatic membrane laying device 4 on the connecting joint section 303 of the telescopic pile driver 3;

[0050] S3: The retractable pile driver 3 is connected to the pile driver, and the test pile 2 is transported from the entrance of the pile hole 1 to the designed pile top elevation below the ground through the retractable pile driver 3. During the transportation, the side wall of the pile hole 1 is affixed with a friction-reducing film by the automatic film laying device 4;

[0051] S4: Check the verticality of the retractable pile driver 3 and the test pile 2 to ensure that they meet the verticality requirement;

[0052] S5: Conduct static load pile test, perform the test according to the specification and record the data.

[0053] During the pile driving operation, the pile driver grips the pile head section 301 of the retractable pile driver 3 through the pile clamp and starts driving the pile. The pile is driven into the pile to a depth h in a single time, and the automatic retractable section 302 of the pile driver is extended by the same distance h in a single time. This operation of first driving into the pile and then extending the pile is repeated until the top of the test pile 2 reaches the designed pile top elevation.

[0054] The specific operations of the static load pile test are as follows:

[0055] A single pile vertical compressive static load test or a single pile vertical tensile static load test is carried out. The test adopts the stacking method and the loading adopts the slow maintenance method. The load is added to the pile head section 301 in stages according to certain requirements. When the settlement of the pile head section 301 reaches a certain specified relative stability standard, the next level of load is applied. When the specified test termination condition is reached, the loading is stopped and the pile is unloaded in stages to zero. The data such as the pile top settlement, load and cumulative time are recorded.

[0056] During the static load pile test, the automatically retractable section of the retractable pile driver 3 is of a rigidly fixed length, and the retractable pile driver 3 is firmly connected to the test pile 2 .

[0057] The solution of the present invention first considers sending the test pile to the designed pile top elevation below the ground, secondly ensures that the pile foundation test can be carried out on the ground, and finally improves the accuracy of the pile foundation test data by minimizing the interference of the pile and soil friction in the section from the designed pile top elevation to the ground (height range H).

[0058] The technical solution of the present invention is further described in detail below with reference to specific embodiments:

[0059] At the test pile site, a hole is drilled to the designed pile top elevation using an auger or other equipment, with a hole diameter no smaller than the diameter of the test pile 2. A pile driver drives the test pile 2 into the pile hole 1. When the top of the test pile 2 is approximately 1 meter above the ground, the retractable pile driver 3 is connected to the top of the test pile 2, and an automatic membrane spreader 4 is installed. The pile driver's pile clamp grips the retractable pile driver 3's head section 301 and begins driving the pile. Each time the pile is driven to a depth h, the automatic retractable pile driver 302 is extended by the same distance h. This cycle of driving in, then extending continues until the top of the test pile 2 reaches the designed pile top elevation. At this point, the automatic membrane spreader 4 has fully applied the friction-reducing membrane from the designed pile top elevation to the ground level H in the pile hole 1. The automatic retractable pile driver 302 is then adjusted to ensure the top of the pile head section 301 is near the ground level. The entire process is calibrated using a theodolite to confirm that the verticality of the test pile 2 and the retractable pile driver 3 meets the requirements of pile foundation specifications. Finally, a static load pile test is conducted.

[0060] The pile head section 301 of the retractable pile driver 3 is not limited to being made of reinforced concrete or a steel pipe sleeve. The figure shows a reinforced concrete pile head section 3012. It can be square or circular in shape, with the same cross-section as the test pile 2 and no larger than the test pile 2, to accommodate different pile drivers and pile foundation static load testing equipment. The pile head section 301 of the retractable pile driver 3 has pre-embedded steel plates at both ends, with bolts or pre-reserved bolt holes. The upper end ensures reliable connection with the pile foundation inspection device, and the lower end ensures reliable connection with the pile driver's automatic retractable section 302. The figure shows a pre-embedded steel plate 3011 at the top of the pile head section, a connecting plate 3021 at the top of the retractable section, and pre-embedded bolts 3013 at the bottom of the pile head section.

[0061] The automatically retractable section 302 of the retractable pile driver 3 has a built-in power supply, power system, and signal transmission system, allowing for on-site remote control. The retractable range should extend from the designed pile top elevation to a ground depth H, and its bearing capacity should exceed the ultimate bearing capacity of the test pile 2. The upper connecting end plate of the automatically retractable section 302 of the retractable pile driver 3 features pre-set bolt holes to ensure reliable connection with the pile driver's pile head section 301. The lower end is threaded to ensure reliable connection with the threaded sleeve of the pile driver's connecting joint section 303.

[0062] The retractable pile driver 3 is connected to the joint section 303, and a threaded sleeve 3031 is reserved at the center of the connecting plate 3033 to ensure reliable connection with the automatic retractable section 302 of the pile driver. Four groups of support rod sleeves 3032 are symmetrically arranged in groups of two around the threaded sleeve to ensure reliable connection between the connecting plate 3033 and the test pile 2.

[0063] The connecting joint section 303, the automatic telescopic section 302 and the pile head section 301 of the telescopic pile driver 3 are all separable and can be reliably connected by bolt connection, welding or other means according to different pile types, different depths H and different mechanical equipment selection combinations used in the project.

[0064] The lower end of the film laying device's support rod 401 is threaded to ensure secure connection with the support rod sleeve 3032 of the pile driver's connecting joint section 303. An upper retaining ring secures the film laying device's film winding shaft 402, preventing relative rotation between the two. Four sets of two are installed in each set. A return spring 405 is installed between the support rod and the film pressing roller 403 of the automatic film laying device 4 to ensure that the film pressing crossbar 4032 of the film pressing roller 403 is in close contact with the wall of the pile hole 1.

[0065] When the film roll shaft 402 of the film laying device is assembled, the film roll 404 is first inserted therein so that the two can rotate relative to each other, and then the film pressing rollers 403 are installed on both sides.

[0066] The film pressing roller 403 of the automatic film laying device 4 can be made into a Π shape, and two connecting vertical rods 4031 are located on both sides of the roll film 404 and connected to the roll film shaft 402. A film pressing cross bar 4032 is installed with rollers in sections on the entire rod for laying friction-reducing film. The two ends of the film pressing cross bar 4032 can be telescopically fine-tuned. The length of the film pressing cross bar 4032 matches the side length of the pile hole 1 and can be telescopically adjusted to adapt to different pile diameters.

[0067] The rolled film 404 is a rolled anti-friction film, which can be made of a synthetic material such as polytetrafluoroethylene (PTFE, Teflon) with a static friction coefficient of 0.04 to 0.1 and a dynamic friction coefficient of 0.02 to 0.07.

[0068] When the designed depth H from the pile top elevation to the ground is close to or greater than the length of the test pile 2, the test pile 2 should be connected to the retractable pile driver 3 and the automatic membrane laying device 4 before the pile is driven.

[0069] The verticality of the test pile 2 and the retractable pile driver 3 is confirmed by the full calibration process using a theodolite. If the error range is exceeded, an immediate alarm is issued to ensure that the pile foundation specifications are met. A prompt is also issued when the test pile 2 reaches the designed pile top elevation.

[0070] The technical solution of the present invention and the test pile 2 in the attached drawing are all prefabricated square piles. Other pile types can refer to this solution in the same way.

[0071] In the technical solution of the present invention, the retractable pile driver 3 can also be replaced by an original pile type or a pile with a smaller cross-sectional size, as long as the installation distance of the automatic film laying device 4 is met.

[0072] This solution adopts a combination of a retractable pile driver and an automatic membrane spreader to solve two core problems of the traditional static load pile test method:

[0073] 1. Accurately locate the test pile: The test pile is directly delivered to the underground design elevation through a retractable pile driver, without the need to extend the pile body to the ground. This avoids the interference of friction between the extended pile body and the soil in traditional methods, ensuring that the test data truly reflects the actual bearing capacity of the pile body.

[0074] 2. Actively isolate friction: An automatic film applicator is used to lay a friction-reducing film around the test pile, covering the area from the ground to the pile top elevation. This actively blocks friction between the pile and the surrounding soil, improving data accuracy while preventing the risk of pile overload caused by the accumulation of frictional resistance during the pile test.

[0075] After using this device, the load transfer path of the test pile is clearer. There is no need to correct the data through complex calculations. The test results consistent with the actual construction pile foundation can be directly obtained, which simplifies the process while ensuring the safety of the project.

[0076] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modification, equivalent replacement and improvement made by any technician familiar with the profession to the above embodiment without departing from the scope of the technical solution of the present invention and based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A device for delivering piles and performing static load testing of underground pile foundations, characterized by: Includes retractable pile driver and automatic membrane spreader; The retractable pile driver comprises a pile head section, an automatic retractable section and a connecting joint section connected in sequence. The pile head section is used to connect to a pile driver and static load test equipment. The automatic retractable section comprises a retractable rod. The connecting joint section is used to connect to a test pile. The retractable pile driver is used to transport the test pile from the pile hole entrance to the designed pile top elevation below the ground. The automatic film laying device is matched with the retractable pile driver. The automatic film laying device is installed on the connecting joint section of the retractable pile driver and is used to lay the friction-reducing film around the test piles transported to the designed pile top elevation below the ground. The laying position of the friction-reducing film is from the ground to the designed pile top elevation below the ground.

2. The device for underground pile foundation delivery and static load testing according to claim 1, characterized in that: The pile head section, the automatic telescopic section and the connecting joint section are detachably connected.

3. The device for underground pile foundation delivery and static load testing according to claim 1, characterized in that: The automatic telescopic section has a built-in power supply, a power system, a controller and a signal transmission system. The power system provides kinetic energy for the telescopic rod to be extended and retracted. The controller is used to control the operation of the power supply and power system. The signal transmission system is used for remote control extension and retraction. The telescopic range of the automatic telescopic section is greater than the distance from the designed pile top elevation below the ground to the ground. The bearing capacity of the automatic telescopic section is greater than the maximum construction load during the pile driving process.

4. The device for underground pile foundation delivery and static load testing according to claim 1, characterized in that: The connecting joint section includes a connecting plate, the middle part of the upper end of the connecting plate has an installation interface for connecting to the automatic telescopic section, several groups of support rod sleeves for installing the automatic film laying device are provided around the upper end of the connecting plate, and the lower end of the connecting plate has a fixing for connecting to the test pile.

5. The device for underground pile foundation delivery and static load testing according to claim 4, characterized in that: The automatic film laying machine includes a film laying machine support rod, a film laying machine winding shaft and a film pressing roller. The film laying machine support rod is correspondingly installed on the support rod sleeve; the film laying machine winding shaft is supported on the film laying machine support rod, and the film laying machine winding shaft is installed with a film with a friction-reducing film; a film pressing roller is provided on the side of the film laying machine winding shaft, and the film pressing roller is used to press the film rolling onto the side wall inside the pile hole passed through when the pile is delivered.

6. The device for underground pile foundation delivery and static load testing according to claim 5, characterized in that: The film pressing roller includes a connecting vertical rod and a film pressing cross rod. The connecting vertical rod connects the film pressing cross rod to the film laying device film winding shaft. The end of the connecting vertical rod is hook-shaped and hooked on the film laying device film winding shaft. A return spring is provided on the film laying device support rod. One end of the return spring is connected to the film laying device support rod and the other end is connected to the connecting vertical rod. The film pressing cross rod is used for laying and pressing friction-reducing film.

7. The device for underground pile foundation delivery and static load testing according to claim 6, characterized in that: Rollers are installed in sections on the entire rod of the film pressing crossbar, and the friction-reducing film bypasses the rollers and is pressed against the side wall inside the pile hole.

8. The device for underground pile foundation delivery and static load testing according to claim 5, characterized in that: The automatic film laying device is provided with four symmetrical groups, and correspondingly, the support rod sleeves connecting the joint sections are also provided with four groups.

9. A method for delivering piles and performing static load testing of underground pile foundations, characterized in that: The following steps are involved: S1: Drill pile holes at the test pile points; S2: Connect the test pile to the connecting joint section of the retractable pile driver, and install an automatic membrane spreading device on the connecting joint section of the retractable pile driver; S3: The retractable pile driver is connected to the pile driver, and the test pile is transported from the pile hole entrance to the designed pile top elevation below the ground through the retractable pile driver. During the transportation, the side wall of the pile hole is covered with anti-friction film by the automatic film laying device. S4: Check the verticality of the retractable pile driver and the test pile to ensure that they meet the vertical requirements; S5: Conduct static load pile test.

10. The method for underground pile foundation delivery and static load testing according to claim 9, characterized in that: During operation, the pile driver starts to drive the pile by holding the pile head section of the retractable pile driver through the pile clamp. The pile is driven into the pile to a depth of h at a time, and the automatic retractable section of the pile driver is extended by the distance h at a time. This operation of first driving in and then extending is repeated until the top of the test pile is pressed to the designed pile top elevation.

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