Double-cavity coupling type counterforce generating device and application method thereof in pile foundation detection

Abstract

The application provides a double-cavity coupled counterforce generating device and an application method thereof in pile foundation detection. The device comprises: a base surface, wherein a test pile is arranged on the base surface; a rigid outer cylinder, wherein the bottom of the rigid outer cylinder is connected with the base surface; a rigid inner cylinder, wherein the rigid inner cylinder is coaxially arranged in the rigid outer cylinder, the rigid inner cylinder covers the test pile outside the base surface, a jack is coaxially arranged in the rigid inner cylinder, the bottom of the jack is mounted on the test pile, and the top of the rigid inner cylinder is in abutment with the top end of the piston rod of the jack. Under the same projection area, the coupling superposition of the vacuum cavity and the pressure cavity can obtain the maximum counterforce far exceeding the pure vacuum scheme. Since the positive pressure value in the annular sealing cavity can be increased to several megapascals or even higher, for example, more than 5 MPa, even if the size of the rigid inner cylinder is limited, the total thrust far exceeding the pure vacuum scheme can be generated, the large-tonnage loading demand is met, and the loading capacity is doubled.

Description

Technical Field

[0001] This invention relates to the field of engineering mechanics testing and reaction force loading technology, specifically to a dual-cavity coupled reaction force generator and its application method in pile foundation testing. Background Technology

[0002] In engineering practices such as static load tests on pile foundations and structural loading tests, it is usually necessary to apply large static loads to test the bearing capacity of the structure. The traditional methods are mainly the surcharge method and the anchor pile method.

[0003] The stacking method requires stacking a large amount of counterweights, such as sandbags, concrete blocks, and steel ingots, on top of the object being tested. The load is applied by lifting the counterweights with jacks. This method has the following drawbacks: (1) It requires a lot of space and cannot be applied to narrow spaces such as under bridges, basements, and tunnels; (2) The cost of transporting and stacking the counterweights is high and the construction period is long; (3) There is a risk of overturning when the counterweights are stacked too high.

[0004] The anchor pile method requires the construction of anchor piles around the test pile, using the pull-out resistance of the anchor piles to provide reaction force. This method has a long construction period, high cost, and high requirements for site conditions.

[0005] In recent years, the vacuum negative pressure static pile testing method has been proposed. This method involves setting up a rigid platform above the test pile and drawing a vacuum, using external atmospheric pressure as the reaction force. Chinese patent CN1385586A discloses a vacuum negative pressure static pile testing method and apparatus, in which a rigid platform is installed around the pile to be tested, and a vacuum pump is used to evacuate the pile. After reaching a certain vacuum level, the rigid platform can provide sufficient reaction force to pressurize the test pile. However, this scheme has limitations in principle: its maximum achievable pressure difference is limited to one standard atmosphere, approximately 0.1 MPa, because even if the sealed container is evacuated to a theoretical absolute vacuum, the pressure difference between the inside and outside is only 0.1 MPa. In practical engineering, due to limitations in vacuum pump efficiency and sealing conditions, the actual vacuum level that can usually be obtained is only -80 kPa to -95 kPa, corresponding to a pressure difference of only 80 to 95 kPa. Therefore, the reaction force that the pure vacuum solution can provide is strictly limited by the projected area of ​​the rigid platform. In a small space with severely limited space, the platform area is limited, and the maximum reaction force that this solution can provide has a theoretical upper limit, which often makes it difficult to meet the needs of large-tonnage testing.

[0006] Furthermore, when positive pressure assisted loading is used, the high-pressure medium will generate a huge buoyancy force on the rigid outer cylinder. If a reliable anti-buoyancy fixing structure is not set up, the rigid outer cylinder is at risk of being lifted or thrown away, posing a serious safety hazard. At the same time, how to achieve a reliable bottom seal on a natural soil foundation to prevent high-pressure gas from leaking downwards along the outer wall of the rigid inner cylinder into the soil is also a technical problem that urgently needs to be solved in this field.

[0007] Therefore, how to obtain a large-tonnage reaction force exceeding atmospheric pressure in a confined space while ensuring structural safety and sealing reliability under high-pressure conditions is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] This invention provides a dual-cavity coupled reaction force generating device capable of generating large-tonnage reaction forces far exceeding atmospheric pressure limits in a confined space, while possessing high-pressure safety protection capabilities and a reliable sealing structure, and its application method in pile foundation testing. It is mainly used to generate controllable large-tonnage reaction forces in a limited space through the coupling effect of a vacuum chamber and a pressure chamber. It is applied to engineering scenarios such as pile foundation static load tests to overcome the shortcomings of existing vacuum negative pressure schemes where the reaction force is limited by the projected area and the upper limit of atmospheric pressure. It solves the safety problem of the outer cylinder's anti-buoyancy under high-pressure conditions and addresses the technical challenges of sealing the bottom of the annular cavity and guiding the rigid inner cylinder on natural soil foundations.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A dual-cavity coupled reaction force generating device includes:

[0011] The foundation surface, on which test piles are set;

[0012] A rigid outer cylinder, the bottom of which is connected to the foundation surface;

[0013] A rigid inner cylinder is coaxially disposed inside the rigid outer cylinder. The rigid inner cylinder covers the outside of the test pile on the foundation surface. A jack is coaxially disposed inside the rigid inner cylinder. The bottom of the jack is installed on the test pile. The top of the rigid inner cylinder abuts against the top of the piston rod of the jack.

[0014] An annular sealed cavity is formed between the rigid outer cylinder and the rigid inner cylinder, and the annular sealed cavity is connected to a pressurized fluid source;

[0015] The rigid inner cylinder has a vacuum chamber inside, and the vacuum chamber is connected to a vacuum pumping device.

[0016] The base surface is located at the bottom of the rigid outer cylinder and the rigid inner cylinder, and a sealing layer is laid there.

[0017] A preferred technical solution of this application is: an annular groove is formed on the base surface, and the position of the annular groove corresponds to the position of the cylinder wall of the rigid inner cylinder;

[0018] The sealing layer is laid inward from the foundation surface of the outer perimeter of the rigid outer cylinder, passing sequentially below the bottom of the rigid outer cylinder, the annular groove, below the bottom of the rigid inner cylinder, and extending to the test pile;

[0019] The sealing layer is a single-layer sealing film or a multi-layer composite sealing film structure and is made of flexible airtight material. The thickness of the single-layer sealing film is 0.12~0.16mm, and the total thickness of the multi-layer composite sealing film is 0.5~2.0mm.

[0020] A preferred technical solution of this application is that when the sealing layer is a single-layer sealing membrane structure, the flexible airtight material used includes polyethylene film or rubber sheet.

[0021] When the sealing layer is a multi-layer composite sealing membrane structure, the flexible airtight material used includes two layers of polyethylene membrane and a bentonite waterproof layer sandwiched between the two membranes.

[0022] The sealing layer covers the bottom and two sides of the annular groove to form a U-shaped sealing lining. The depth of the annular groove is 0.5 to 1.5 meters, and the width of the annular groove is 4 to 8 centimeters greater than the thickness of the rigid inner cylinder wall.

[0023] The bottom wall of the rigid inner cylinder is pressed into the annular groove, and the sealing layer wraps around the bottom outer wall and bottom surface of the rigid inner cylinder;

[0024] The bottom of the rigid outer cylinder is pressed tightly against the sealing layer.

[0025] A preferred technical solution of this application is that the bottom edge of the rigid inner cylinder wall is provided with a rounded corner structure to protect the sealing layer from being punctured when it is pressed into the annular groove;

[0026] The bottom edge of the rigid outer cylinder is provided with an outward flange, and an anchoring structure is provided on the foundation surface accordingly;

[0027] The outward-facing flange is detachably locked to the anchoring structure, and is used to provide a downward mechanical constraint force to the rigid outer cylinder when high pressure is applied in the annular sealing cavity, so as to balance the upward buoyancy generated by the high pressure.

[0028] A preferred technical solution of this application is that the anchoring structure is a spiral anchor pile, a ground anchor, or an anchor rod;

[0029] When the anchoring structure is a helical anchor pile, the helical anchor pile is screwed into the foundation soil by a torsion device, and then connected to the outward flange by a connector.

[0030] When the anchoring structure is a ground anchor or an anchor rod, it is driven into the foundation soil by the ground anchor or anchor rod and then connected to the outward flange by a tie rod.

[0031] A preferred technical solution of this application is that the wall thickness of the rigid inner cylinder meets the external pressure stability requirements, and its critical pressure for external pressure instability is... Greater than 1.5 times the maximum working pressure of the annular sealing cavity, that is:

[0032] ;

[0033] in, The elastic modulus of the rigid inner cylinder material. Poisson's ratio, For rigid inner cylinder wall thickness, The outer diameter of the rigid inner cylinder This is the maximum working pressure of the annular sealed cavity.

[0034] A preferred technical solution of this application: the pressurized fluid source is connected to the annular sealed cavity through an air pipe, the air pipe passes through the side wall of the rigid outer cylinder, and a sealing joint is provided at the penetration point;

[0035] The pressurized fluid source is an air compressor, a high-pressure gas cylinder, or a hydraulic pump station, used to inject compressed gas or hydraulic oil into the annular sealed cavity;

[0036] The vacuum pumping device is connected to the vacuum chamber through a vacuum pipeline. The vacuum pipeline is led out from the side wall of the rigid inner cylinder and passes through the side wall of the rigid outer cylinder, with a vacuum sealing joint at the penetration point.

[0037] A preferred technical solution of this application includes a pressure monitor, a vacuum gauge and a data acquisition instrument installed outside the rigid outer cylinder, as well as a safety pressure relief device installed at the top of the rigid outer cylinder;

[0038] The air pressure monitor is connected to the annular sealed cavity for real-time monitoring of the pressure inside the annular sealed cavity;

[0039] The vacuum gauge is connected to the vacuum chamber and is used to monitor the vacuum level inside the vacuum chamber;

[0040] The data acquisition instrument is used to record data collected by the barometer and vacuum gauge;

[0041] The safety pressure relief device is connected to the annular sealing cavity. The safety pressure relief device is a safety valve or a rupture disc, and its opening pressure setting value is higher than the maximum working pressure of the annular sealing cavity.

[0042] This application also provides a method for applying a dual-cavity coupled reaction force generator in pile foundation testing, including the following steps:

[0043] S1. Open an annular groove on the base surface, remove sharp foreign objects from the groove, and make the bottom of the groove basically flat.

[0044] S2. Lay the sealing layer, starting from the foundation surface of the outer rigid cylinder, passing through the bottom of the outer cylinder, the annular groove, the bottom of the rigid inner cylinder, and extending to the test pile. Wrap the part of the sealing layer (2) extending to the test pile around the outer wall of the test pile and fix it with clamps or binding to ensure that the sealing layer (2) is tightly attached to the pile body. The sealing layer covers the bottom of the groove and the two sides of the groove to form a U-shaped lining.

[0045] S3. Press the bottom wall of the rigid inner cylinder into the annular groove so that the sealing layer covers the bottom outer wall and bottom surface of the rigid inner cylinder;

[0046] S4. Hoist the rigid outer cylinder into place and fit it over the rigid inner cylinder, so that the bottom of the outer cylinder is pressed against the sealing layer, and at the same time the bottom outward flange is locked to the anchoring structure.

[0047] S5. Start the vacuum pumping device to evacuate the vacuum chamber inside the rigid inner cylinder. The external atmospheric pressure will press the rigid inner cylinder against the sealing layer, so that the bottom of the rigid inner cylinder and the sealing layer at the bottom of the annular groove form a bottom seal. At the same time, the rigid outer cylinder will be pressed against the sealing layer to form a bottom seal of the outer cylinder.

[0048] S6. The compressed medium is injected into the annular sealed cavity through the pressurized fluid source and the air pipe until the target pressure is reached. The sealing layer wraps the outer side of the rigid inner cylinder wall to form a lateral seal. At the same time, the annular cavity and the vacuum chamber are isolated by the rigid inner cylinder solid wall.

[0049] S7. Start the jack to conduct a loading test;

[0050] S8. After the test, first open the safety relief device to release the compressed medium in the annular sealed cavity. After the pressure in the cavity drops to atmospheric pressure, then break the vacuum in the vacuum chamber.

[0051] S9. Disconnect the outward flange from the anchoring structure, lift off the rigid outer cylinder, pull out the rigid inner cylinder, and recover the sealing layer.

[0052] A preferred technical solution of this application: In step S5, the pressure established by the vacuum pumping device, the self-weight of the rigid inner cylinder, and the upward buoyancy force generated by the high pressure in the annular sealed cavity on the rigid inner cylinder in step S6 satisfy the following relationship:

[0053] The combined force of the pressure created by vacuuming and the weight of the rigid inner cylinder is greater than the upward buoyancy, ensuring that the rigid inner cylinder remains tightly pressed against the sealing layer throughout the entire loading process.

[0054] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0055] 1. Under the same projected area, the present invention can obtain a maximum reaction force far exceeding that of the pure vacuum solution through the coupling and superposition of the vacuum chamber and the pressure chamber. Since the positive pressure value in the annular sealed cavity can be increased to several megapascals or even higher, such as 5 MPa or above, through the pressurized fluid source, even if the rigid inner cylinder has a limited size, it can generate a total thrust far exceeding that of the pure vacuum solution, meet the requirements of large tonnage loading, and double the loading capacity.

[0056] 2. This invention achieves bottom sealing, lateral sealing, bottom sealing of the outer cylinder, and sealing at the test pile in one step by using a continuous sealing diaphragm extending from the outer cylinder periphery through an annular groove to the test pile, combined with an annular groove, a flexible sealing layer, and a rigid inner cylinder pressed in. It does not require additional dynamic sealing components or mechanical guiding mechanisms, and has a simple structure and high reliability. Moreover, by excavating an annular groove and laying a continuous sealing layer, the natural soil foundation is transformed into a sealable and reliable foundation without the need for concrete pouring. The annular groove wall provides natural guidance for the pressing of the rigid inner cylinder and provides horizontal constraints to prevent the rigid inner cylinder from deviating. No additional guiding mechanism is required, making construction convenient and cost-effective. The sealing layer extends from the outer cylinder periphery to the test pile body, forming a complete airtight barrier that completely isolates the bottom of the entire device from the natural foundation, with no leakage channels.

[0057] 3. This invention adopts a coaxial double-cylinder double-cavity structure. By controlling the vacuum degree and the pressure of the annular cavity separately, the reaction force can be precisely and steplessly adjusted. The overall size is compact, making it particularly suitable for loading operations in confined spaces such as under bridges, basements, tunnels, and docks. The air pipes and vacuum pipes pass through the side wall of the cylinder to avoid damaging the continuity of the bottom sealing layer. A special sealing joint is set at the penetration point to ensure the sealing reliability under high pressure and vacuum conditions. By conceptualizing and diversifying the anchoring structure, spiral anchor piles or ground anchors are used as anchoring schemes on natural soil foundations. There is no need to pre-embed concrete foundations, making construction convenient and reusable.

[0058] 4. This invention adopts a triple anti-flying structure of mechanical locking constraint, vacuum negative pressure adsorption, and safety valve pressure relief, which realizes inherent safety under high pressure conditions. By using a specific operation sequence of first evacuating the vacuum and then pressurizing, and first releasing the high pressure and then breaking the vacuum, it ensures reliable sealing during operation and safety of the outer cylinder during pressure relief. Furthermore, by quantitatively designing the external pressure stability, it ensures that the rigid inner cylinder will not experience external pressure instability under the maximum working pressure, thus guaranteeing the structural integrity of the device under high pressure conditions. Attached Figure Description

[0059] Figure 1 This is a cross-sectional view of the overall structure of the dual-cavity coupled reaction force generator; Figure 2 This is a top view schematic diagram of the connection relationship between the outward-facing flange and the anchoring structure in this invention.

[0060] In the diagram: 1. Rigid outer cylinder; 2. Sealing layer; 3. Foundation surface; 4. Rigid inner cylinder; 5. Jack; 6. Annular sealing cavity; 7. Pressurized fluid source; 8. Gas pipe; 9. Vacuum chamber; 10. Vacuum pipeline; 11. Vacuum pumping device; 12. Pressure monitor; 13. Vacuum gauge; 14. Data acquisition instrument; 15. Outward flange; 16. Anchoring structure; 17. Safety pressure relief device. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention will be further described below with reference to the embodiments.

[0062] Example 1

[0063] Please see Figures 1-2 This embodiment provides a dual-cavity coupled reaction force generating device, including:

[0064] Foundation surface 3, on which test piles are set;

[0065] A rigid outer cylinder 1, the bottom of which is connected to the foundation surface 3;

[0066] A rigid inner cylinder 4 is coaxially arranged inside the rigid outer cylinder 1. The rigid inner cylinder 4 covers the outside of the test pile on the foundation surface 3. A jack 5 is coaxially arranged inside the rigid inner cylinder 4. The bottom of the jack 5 is installed on the test pile. The top of the rigid inner cylinder 4 abuts against the top of the piston rod of the jack 5.

[0067] Among them, both the rigid outer cylinder 1 and the rigid inner cylinder 4 are made of high-strength steel. An annular groove is provided on the base surface 3, and the position of the annular groove corresponds to the position of the cylinder wall of the rigid inner cylinder 4.

[0068] An annular sealed cavity 6 is formed between the rigid outer cylinder 1 and the rigid inner cylinder 4, and the annular sealed cavity 6 is connected to a pressurized fluid source 7;

[0069] The rigid inner cylinder 4 has a vacuum chamber 9 inside, and the vacuum chamber 9 is connected to a vacuum pumping device 11.

[0070] The annular sealed cavity 6 and the vacuum chamber 9 are completely isolated by the solid wall of the rigid inner cylinder 4, and there is no direct gas passage between the two.

[0071] In practice, the pressurized fluid source 7 is connected to the annular sealed cavity 6 through the air pipe 8;

[0072] The pressurized fluid source 7 is an air compressor, high-pressure gas cylinder or hydraulic pump station, used to inject compressed gas or hydraulic oil into the annular sealed cavity 6;

[0073] Vacuum pumping device 11 is connected to vacuum chamber 9 through vacuum pipeline 10;

[0074] The base surface 3 is located at the bottom of the rigid outer cylinder 1 and the rigid inner cylinder 4 and is covered with a sealing layer 2.

[0075] The device also includes a pressure monitor 12, a vacuum gauge 13 and a data acquisition instrument 14 installed outside the rigid outer cylinder 1, as well as a safety pressure relief device 17 installed on the top of the rigid outer cylinder 1.

[0076] The air pressure monitor 12 is connected to the annular sealed cavity 6 to monitor the pressure inside the annular sealed cavity 6 in real time;

[0077] Vacuum gauge 13 is connected to vacuum chamber 9 to monitor the vacuum level inside vacuum chamber 9;

[0078] Data acquisition unit 14 is used to record data collected by barometer 12 and vacuum gauge 13;

[0079] The safety pressure relief device 17 is connected to the annular sealing cavity 6. The safety pressure relief device 17 is a safety valve or a rupture disc, and its opening pressure setting value is higher than the maximum working pressure of the annular sealing cavity 6.

[0080] Example 2

[0081] This embodiment provides a method for applying a dual-cavity coupled reaction force generator in pile foundation testing, characterized by the following steps:

[0082] S1. Open an annular groove on the base surface 3, remove sharp foreign objects from the groove, and make the bottom of the groove basically flat.

[0083] S2. Lay the sealing layer 2, starting from the foundation surface 3 around the rigid outer cylinder 1, passing through the bottom of the outer cylinder, the annular groove, the bottom of the rigid inner cylinder, and extending to the test pile. The part of the sealing layer 2 extending to the test pile is wrapped around the outer wall of the test pile and fixed with clamps or binding to ensure that the sealing layer 2 is tightly attached to the pile body. The sealing layer 2 covers the bottom of the groove and the two side walls of the groove to form a U-shaped lining.

[0084] S3. Press the bottom wall of the rigid inner cylinder 4 into the annular groove so that the sealing layer 2 wraps the bottom outer wall and bottom surface of the rigid inner cylinder 4.

[0085] S4. Hoist the rigid outer cylinder 1 into place and fit it over the rigid inner cylinder 4, so that the bottom of the outer cylinder presses against the sealing layer 2, and at the same time lock the bottom outward flange 15 to the anchoring structure 16.

[0086] S5. Start the vacuum pumping device 11 to evacuate the vacuum chamber 9 inside the rigid inner cylinder 4. Specifically, the pressure established by the vacuum pumping is a negative pressure of 80~95kPa. The external atmospheric pressure presses the rigid inner cylinder 4 against the sealing layer 2, so that the bottom of the rigid inner cylinder and the sealing layer 2 at the bottom of the annular groove form a bottom seal. At the same time, it presses the rigid outer cylinder 1 against the sealing layer to form a bottom seal of the outer cylinder.

[0087] In step S5, the pressure established by the vacuum pumping device 11, the weight of the rigid inner cylinder 4, and the upward buoyancy force generated by the high pressure in the annular sealed cavity 6 on the rigid inner cylinder 4 in step S6 satisfy the following relationship:

[0088] The combined force of the pressure created by vacuuming and the weight of the rigid inner cylinder 4 is greater than the upward buoyancy, ensuring that the rigid inner cylinder 4 remains tightly pressed against the sealing layer 2 throughout the entire loading process.

[0089] S6. Compressed medium is injected into the annular sealed cavity 6 through the pressurized fluid source 7 and the air pipe 8 until the target pressure is reached. The sealing layer 2 wraps around the outer side of the rigid inner cylinder wall to form a lateral seal. At the same time, the annular cavity and the vacuum chamber are isolated by the rigid inner cylinder solid wall.

[0090] The target pressure is determined based on the bearing capacity design requirements of the test pile, to generate the required loading force at the top of jack 5. Specifically, the required total loading force is determined according to the "Technical Specification for Testing of Building Foundation Piles" JGJ106, and then calculated using the formula... The target pressure inside the annular sealed cavity 6 is calculated.

[0091] S7. Start jack 5 to conduct a loading test.

[0092] S8. After the test, first stop the jack loading, open the safety pressure relief device 17 to release the compressed medium in the annular sealed cavity 6, and after the pressure in the cavity drops to atmospheric pressure, break the vacuum in the vacuum chamber 9.

[0093] In step S8, the operation sequence of releasing high pressure first and then breaking the vacuum ensures the safety of the dual-cavity coupled reaction force generating device. If the vacuum is broken first and then the high pressure is released, the rigid inner cylinder 4 loses its vacuum suction, the clamping force of the bottom sealing surface weakens, and the high-pressure medium in the annular sealing cavity 6 may leak into the vacuum chamber 9 along the sealing surface, pushing the rigid inner cylinder 4 upward and causing the device to become unstable. Therefore, the specific sequence of releasing high pressure first and then breaking the vacuum is a necessary technical feature to achieve the safety of this invention.

[0094] The principle behind ensuring the safety of the dual-cavity coupled reaction force generator by first releasing the high pressure and then breaking the vacuum is as follows:

[0095] Step 1: Stop loading jack 5. The jack reaction force returns to zero. At this point, the downward clamping force on the bottom sealing surface of the inner cylinder is... ,in It is a vacuum suction force. For the weight of the inner cylinder, The positive pressure of the annular cavity exerts a downward thrust on the top end face of the inner cylinder. The combined effect of these three factors results in the sealing surface being in a state of maximum compression.

[0096] Step 2: Release the high-pressure medium in the annular sealing cavity 6; the pressure of the high-pressure medium... The downward thrust of the positive pressure in the annular cavity on the inner cylinder gradually decreases. The buoyancy of the high-pressure medium on the inner wall of the outer cylinder decreases synchronously. The vacuum suction force gradually decreases until it disappears, during which time the sealing surface still retains its suction force. and the weight of the inner cylinder With continuous compression, the sealing reliability is always maintained.

[0097] Step 3: De-vacuuming chamber 9. At this point, the pressure inside the annular sealed cavity 6 has dropped to atmospheric pressure, and the outer cylinder has no upward buoyancy. The pressure inside and outside the inner cylinder is balanced, and there is no upward thrust, even with vacuum suction. It disappears without causing any impact or displacement in any direction.

[0098] In summary, by stopping the jack, releasing the high pressure, and breaking the vacuum in sequence, the pressure release is initiated when the sealing surface is under the greatest pressure, and the vacuum is released after the high pressure difference is eliminated, ensuring that the device is in a stable state of force balance at each step.

[0099] S9. Disconnect the outward flange 15 from the anchoring structure 16, lift off the rigid outer cylinder 1, pull out the rigid inner cylinder 4, and recover the sealing layer 2.

[0100] Example 3

[0101] This embodiment provides the construction of the annular sealing groove and the laying of the sealing layer for a dual-cavity coupled reaction force generating device, as detailed below:

[0102] When conducting pile foundation testing on natural soil foundation, first excavate an annular groove on foundation surface 3. The depth of the annular groove is 0.5 to 1.5 meters, depending on the soil conditions and the required lateral constraint force. The width of the annular groove is 4 to 8 centimeters greater than the wall thickness of the rigid inner cylinder 4, in order to reserve the thickness of the sealing layer and the installation gap.

[0103] The bottom of the trench should be as flat as possible, and sharp stones and other foreign objects that may puncture the sealing layer should be removed. For soft soil foundations, the trench walls can be temporarily supported by steel sheet piles or cement-soil mixing piles to prevent collapse.

[0104] Then, the sealing layer 2 is laid. The sealing layer 2 is laid from the foundation surface 3 around the rigid outer cylinder 1 inward, passing in sequence below the bottom of the rigid outer cylinder 1, the annular groove, below the bottom of the rigid inner cylinder 4, and extending to the test pile. The sealing layer 2 surrounds the pile body at the test pile position and fits tightly with the pile body to form a continuous flexible sealing membrane that completely covers the bottom area of ​​the device from the outside to the inside. The sealing layer 2 completely separates the bottom of the entire device from the natural foundation, forming a complete airtight barrier. The part of the sealing layer 2 that extends to the test pile is pressed by the test pile body to block the path of groundwater or gas seeping upward along the pile body.

[0105] The sealing layer 2 is a single-layer sealing membrane or a multi-layer composite sealing membrane structure and uses flexible airtight material. The thickness of the single-layer sealing membrane is 0.12~0.16mm, and the total thickness of the multi-layer composite sealing membrane is 0.5~2.0mm, which is determined according to the design pressure and foundation surface conditions.

[0106] In specific implementation, when the sealing layer 2 is a single-layer sealing membrane structure, the flexible airtight material used includes polyethylene film or rubber sheet; when the sealing layer 2 is a multi-layer composite sealing membrane structure, the flexible airtight material used includes two layers of polyethylene film and a bentonite waterproof layer sandwiched between the two films. The bentonite expands when it comes into contact with water, which can automatically seal tiny puncture holes and improve sealing reliability. The flexible airtight material used is a high-density polyethylene film, which has excellent seepage prevention performance, strong chemical stability and excellent durability, and a significant sealing effect.

[0107] The sealing layer 2 covers the bottom and two sides of the annular groove, forming a U-shaped sealing lining. The bottom wall of the rigid inner cylinder 4 is pressed into the annular groove. The sealing layer 2 wraps the bottom outer wall and bottom surface of the rigid inner cylinder 4, forming a three-dimensional seal. The bottom seal is achieved by the sealing layer between the bottom of the rigid inner cylinder 4 and the bottom of the groove, and the lateral seal is achieved by the sealing layer 2 wrapping the bottom outer wall of the rigid inner cylinder 4. This blocks the path of external water and soil to seep downward along the outer side of the cylinder wall, and at the same time blocks the path of high-pressure gas in the annular sealing cavity 6 to leak downward along the outer side of the cylinder wall into the soil.

[0108] The bottom of the rigid outer cylinder 1 is pressed tightly against the sealing layer 2. After vacuuming, the external atmospheric pressure presses the rigid outer cylinder 1 against the sealing layer 2, forming a bottom seal of the rigid outer cylinder 1.

[0109] Example 4

[0110] This embodiment provides a pipe through-wall sealing structure for a dual-cavity coupled reaction force generator, as detailed below:

[0111] The gas pipe 8 passes through the side wall of the rigid outer cylinder 1, and its penetration position is located in the upper middle part of the side wall of the rigid outer cylinder 1. The high pressure medium inlet is higher than the liquid level in the annular cavity or in the gas phase space. A sealing joint is provided at the penetration point. The sealing joint adopts a conical sealing structure or a compression fitting sealing structure and can withstand the maximum working pressure of the annular sealing cavity 6.

[0112] The vacuum pipeline 10 extends from the side wall of the rigid inner cylinder 4 and passes through the side wall of the rigid outer cylinder 1. A vacuum sealing joint is provided at the penetration point. The vacuum sealing joint adopts the same sealing principle as the high-pressure sealing joint, but selects appropriate sealing materials and structural forms according to the vacuum operating conditions to ensure that no external gas leaks into the vacuum chamber 9 under negative pressure. All sealing joints of the through-wall pipelines adopt a detachable structure to facilitate the assembly, disassembly and maintenance of the device.

[0113] Example 5

[0114] This embodiment provides the process of pressing in the rigid inner cylinder 4 and installing the rigid outer cylinder 1 of the dual-cavity coupled reaction force generating device, as detailed below:

[0115] After the sealing layer is laid, the rigid inner cylinder 4 is hoisted into place so that its cylinder wall is aligned with the annular groove. The bottom edge of the rigid inner cylinder 4 is provided with a rounded corner structure to protect the sealing layer 2 from being punctured when it is pressed into the annular groove.

[0116] The rigid inner cylinder 4 is pressed into the annular groove by its own weight. The sealing layer 2 deforms accordingly, wrapping the bottom outer wall and bottom surface of the rigid inner cylinder 4. If necessary, hydraulic pressing or vibration pressing can be used as an auxiliary method.

[0117] After the rigid inner cylinder 4 is pressed into place, the sealing layer 2 forms a bottom sealing pad at the bottom of the trench and a lateral sealing wrapping layer on both sides of the trench wall. The outer wall of the rigid inner cylinder 4 is tightly fitted with the sealing layer 2, blocking the path of external water and soil to seep downward along the outer side of the cylinder wall, and at the same time blocking the path of high-pressure gas in the annular sealing cavity 6 to leak downward along the outer side of the cylinder wall to the soil.

[0118] The groove wall of the annular groove provides natural guidance and horizontal constraint for the pressing of the rigid inner cylinder 4, ensuring the vertical alignment of the rigid inner cylinder 4 and preventing skewing.

[0119] After the rigid inner cylinder 4 is pressed into place, the rigid outer cylinder 1 is hoisted and fitted onto the outside of the rigid inner cylinder 4. The sealing layer 2 is pressed tightly at the bottom of the outer cylinder. Finally, the outward flange 15 at the bottom of the outer cylinder is locked and connected to the anchoring structure 16 on the foundation surface 3.

[0120] The wall of the annular groove provides natural guidance and horizontal constraint for the pressing of the rigid inner cylinder 4, ensuring the vertical alignment of the rigid inner cylinder. The core force mechanism and the calculation method of the loading force are as follows:

[0121] The total thrust of this device acting on the jack is composed of two independent and superimposed force sources.

[0122] Part 1: Atmospheric pressure generated in the vacuum chamber. A vacuum chamber 9 is formed inside the rigid inner cylinder 4 by a vacuum pump 11. Due to the pressure difference between the inside and outside of the chamber, the external atmospheric pressure acts on the force transmission structure of the rigid inner cylinder, generating a downward thrust. The magnitude of this downward force is equal to the product of the difference between the external atmospheric pressure and the residual pressure inside the vacuum chamber and the effective pressure-bearing area inside the rigid inner cylinder. The residual pressure inside the vacuum chamber is the actual vacuum level achieved.

[0123] Part Two: Positive Pressure Thrust Generated by the Annular Sealed Cavity. Within the annular sealed cavity 6 between the rigid outer cylinder 1 and the rigid inner cylinder 4, compressed gas or hydraulic oil is injected through a pressurized fluid source 7, creating a positive pressure environment 1 higher than atmospheric pressure. This positive pressure medium acts directly downwards on the upper surface 1 of the solid end face at the top of the rigid inner cylinder. This end face is a complete pressure-bearing surface, and its effective pressure-bearing area is the cross-sectional area of ​​the outer diameter of the rigid inner cylinder. ,in, The outer diameter of the rigid inner cylinder is such that the downward auxiliary thrust generated by this positive pressure is equal to the product of the positive pressure value inside the annular cavity and the cross-sectional area of ​​the outer diameter of the rigid inner cylinder.

[0124] Two-cavity coupling mechanism and total thrust superposition: The two thrusts mentioned above are superimposed coaxially and in the same direction through the solid structure of the rigid inner cylinder, and finally converge and are transmitted to the top of the piston rod of the jack, together forming the total loading force applied to the test pile.

[0125] The mechanical expression for its total thrust F is:

[0126] ;

[0127] in, Atmospheric pressure. This is the absolute pressure within the vacuum chamber. The effective pressure-bearing area inside the rigid inner cylinder. The outer diameter cross-sectional area of ​​the rigid inner cylinder. This is the positive pressure value inside the annular sealed cavity.

[0128] Rigid inner cylinder external pressure stability design:

[0129] In operation, the rigid inner cylinder 4 is subjected to the high-pressure medium inside the annular sealed cavity 6 on its outer side and the negative pressure of the vacuum chamber 9 on its inner side. The pressure difference between the inside and outside is equal to... Under this pressure difference, the rigid inner cylinder wall bears the external pressure load.

[0130] For a thin-walled cylindrical structure, the critical pressure for external pressure instability is determined by the following formula:

[0131] ;

[0132] in, The elastic modulus of the material. Poisson's ratio, For wall thickness, The outer diameter is the inner cylinder.

[0133] To ensure that the rigid inner cylinder does not experience external pressure instability under maximum working pressure, its wall thickness should meet the following requirements. The safety factor of 1.5 takes into account factors such as material inhomogeneity, manufacturing tolerances, and corrosion thinning during long-term use.

[0134] Sealing reliability conditions:

[0135] After vacuuming, the external atmospheric pressure presses the rigid inner cylinder 4 tightly against the sealing layer 2. The positive pressure inside the annular sealing cavity 6 acts on the top end face of the rigid inner cylinder 4, generating an additional downward thrust. The combined downward force is always greater than the upward reaction force generated when the jack 5 is working, ensuring that the rigid inner cylinder 4 is pressed tightly against the sealing layer 2 throughout the entire loading process, and that the bottom seal remains reliable.

[0136] The sealing reliability condition is expressed by the following formula:

[0137] ;

[0138] in, It is a vacuum suction force. For the weight of the inner cylinder, The downward thrust exerted by the positive pressure of the annular cavity on the top end face of the inner cylinder. The upward reaction force generated when the jack is working

[0139] Anti-buoyancy safety principle:

[0140] When high pressure is applied inside the annular sealed cavity 6, the high-pressure medium acts on the inner wall of the top of the rigid outer cylinder 1, generating an upward buoyancy force. In the formula, This represents the positive pressure value within the annular sealed cavity. This is the projected area of ​​the inner wall at the top of the rigid outer cylinder. This buoyancy is balanced by the following two mechanisms:

[0141] First layer: The detachable locking connection between the outward-facing flange 15 and the anchoring structure 16 provides mechanical restraint. This transfers the buoyancy force deep into the foundation.

[0142] The second layer: The safety pressure relief device 17 automatically opens to relieve pressure when the pressure exceeds the set value, preventing the buoyancy force from increasing indefinitely.

[0143] In addition, the downward pressure generated by the external atmospheric pressure acting on the top outer wall of the rigid outer cylinder 1 can also provide auxiliary balance, but its magnitude is much smaller than the buoyancy force. The anti-buoyancy core of the present invention relies on the combination of the above-mentioned anchoring force and the safety pressure relief device.

[0144] Example 6

[0145] This embodiment provides a rigid outer cylinder 1 mounting structure for a dual-cavity coupled reaction force generator, as detailed below:

[0146] The bottom edge of the rigid outer cylinder 1 is provided with an outward flange 15, and an anchoring structure 16 is provided on the foundation surface 3 accordingly.

[0147] The outward flange 15 is detachably locked to the anchoring structure 16, which provides a downward mechanical constraint force to the rigid outer cylinder 1 when high pressure is applied in the annular sealing cavity 6, so as to balance the upward buoyancy generated by the high pressure.

[0148] Among them, the anchoring structure 16 is a spiral anchor pile, ground anchor or anchor rod;

[0149] When the anchoring structure is a spiral anchor pile, the spiral anchor pile is screwed into the foundation soil by a torsion device, and then connected to the outward flange 15 by a connector.

[0150] When the anchoring structure is a ground anchor or anchor rod, the ground anchor or anchor rod is driven into the foundation soil and then connected to the outward flange 15 by a tie rod.

[0151] In the first specific implementation method, when the foundation surface 3 is a natural soil foundation, the anchoring structure 16 adopts a spiral anchor pile.

[0152] Spiral anchor piles are steel anchor piles with spiral blades. They are driven into the foundation soil to the design depth, which is generally 2 to 5 meters, depending on the soil conditions and the required pull-out resistance. The spiral anchor piles are evenly distributed along the circumference of the outward flange 15, and the number is determined according to the magnitude of the buoyancy, generally 4 to 12. Each spiral anchor pile has a connecting flange at its upper end, which is fixedly connected to the outward flange 15 by high-strength bolts.

[0153] During operation, the buoyancy force generated by the high pressure in the annular sealed cavity 6 is transmitted to each helical anchor pile through the outward flange 15. The interaction force between the helical blades of the helical anchor pile and the surrounding soil balances the buoyancy force. The insertion depth of the helical anchor pile and the blade diameter are determined by the pull-out bearing capacity calculation based on the magnitude of the buoyancy force.

[0154] The advantages of this scheme are: no need to pre-pour concrete foundation, fast construction speed; minimal disturbance to the natural foundation; after the test, the spiral anchor piles can be reversed and recycled for reuse, resulting in good economic efficiency; and it is suitable for various natural foundation conditions such as clay, silt, and sand.

[0155] like Figure 1 As shown, the annular sealing cavity 6 is also connected to a safety pressure relief device 17. This safety pressure relief device is a safety valve or a rupture disc. Its opening pressure setting value is higher than the maximum working pressure of the annular sealing cavity 6. When the pressure in the cavity exceeds the setting value due to abnormal conditions, the safety pressure relief device 17 will automatically open to relieve pressure, preventing the pressure from rising indefinitely and causing the outer cylinder to fly off or the cylinder to burst.

[0156] In the second specific implementation method, when the surface layer of the natural foundation is a weak soil layer, the bearing capacity of the spiral anchor pile is insufficient, or the required pull-out force is extremely large, the anchoring structure 16 adopts a ground anchor or anchor rod.

[0157] Specifically, a drilling rig is used to drill holes in the foundation around the rigid outer cylinder 1, and anchor rods are inserted. Pressure grouting is used to solidify the anchor rods with the surrounding soil. The upper end of the anchor rod is connected to the outward flange 15 through a high-strength tie rod. A tension nut is installed on the tie rod, and pre-tightening force can be applied by tensioning to ensure that each anchor rod is subjected to uniform force. The high-strength tie rod can be made of precision-rolled threaded steel bars.

[0158] The anchoring depth of the ground anchor is determined based on the magnitude of the buoyancy and the conditions of the foundation soil. For soft soil foundations, expanded anchor rods or secondary grouting processes can be used to improve the pull-out bearing capacity.

[0159] This solution has high load-bearing capacity and is suitable for large-tonnage testing conditions, but it is inferior to the spiral anchor pile solution in terms of construction speed and recyclability.

[0160] Example 7

[0161] This embodiment provides a dual-cavity coupled loading mode for a dual-cavity coupled reaction force generator, as detailed below:

[0162] After the anchoring structure 16 is locked in place, the vacuum pumping device 11 is activated to evacuate the vacuum chamber 9 inside the rigid inner cylinder 4 through the vacuum pipeline 10. After evacuation, the external atmospheric pressure presses the rigid inner cylinder 4 tightly against the sealing layer 2 at the bottom of the annular groove, forming a reliable bottom seal between the bottom of the rigid inner cylinder and the sealing layer. At the same time, the external atmospheric pressure presses the rigid outer cylinder 1 against the sealing layer, forming a bottom seal on the outer cylinder. At this time, the rigid inner cylinder 4 is subjected to downward vacuum suction and its own weight.

[0163] Subsequently, the pressurized fluid source 7 is activated, and compressed medium is injected into the annular sealed cavity 6 through the air pipe 8, forming a positive pressure higher than atmospheric pressure in the cavity. This positive pressure acts directly downward on the upper surface of the solid end face at the top of the rigid inner cylinder 4, generating a downward auxiliary thrust. At the same time, the positive pressure in the annular cavity generates an upward buoyancy force on the rigid inner cylinder 4.

[0164] Because the combined force of the downward pressure created by the vacuum and the weight of the rigid inner cylinder 4 is greater than the upward buoyancy of the rigid inner cylinder 4 caused by the positive pressure of the annular cavity, the rigid inner cylinder 4 is always pressed tightly against the sealing layer 2 throughout the entire pressurization process, and the bottom seal remains reliable.

[0165] The two thrusts are coupled and superimposed coaxially and in the same direction through the solid structure of the rigid inner cylinder 4, forming a composite loading force at the top of the piston rod of the jack 5.

[0166] The pressure of the annular sealed cavity 6 is monitored in real time by the air pressure monitor 12, the vacuum degree of the vacuum chamber 9 is monitored by the vacuum gauge 13, and the data acquisition instrument 14 records various parameters.

[0167] Example 8

[0168] This embodiment provides a rigid inner cylinder with a 4-wall thickness for the external pressure stability design of the dual-cavity coupled reaction force generating device, as detailed below:

[0169] When the rigid inner cylinder 4 is in operation, its outer side is subjected to the high pressure medium in the annular sealed cavity 6, such as 3MPa, 5MPa or higher, and its inner side is subjected to the negative pressure of the vacuum chamber 9. The pressure difference between the inside and outside can reach several megapascals. Under the action of pressure difference, the rigid inner cylinder wall is at risk of external pressure instability and collapse. Therefore, the wall thickness of the rigid inner cylinder must be determined by external pressure stability verification.

[0170] According to the theory of external pressure instability of thin-walled cylinders, the wall thickness of the rigid inner cylinder 4 meets the requirements for external pressure stability, and its critical pressure for external pressure instability is... Greater than 1.5 times the maximum working pressure of the annular sealing cavity 6, that is:

[0171] ;

[0172] in, The elastic modulus of the rigid inner cylinder material. Poisson's ratio, For rigid inner cylinder wall thickness, The outer diameter of the rigid inner cylinder This is the maximum working pressure of the annular sealed cavity.

[0173] Taking the rigid inner cylinder material Q345B as an example, , When the maximum working pressure of the annular sealing cavity is 6MPa, a safety factor of 1.5 is taken, and the requirements are as follows: Based on this, the minimum required wall thickness can be calculated.

[0174] In actual design, a detailed finite element analysis should be conducted based on the specific diameter, material grade, and manufacturing process of the rigid inner cylinder to ensure that the cylinder wall stress meets the strength requirements and the overall structure meets the stability requirements under the maximum working pressure. After manufacturing, a pressure test should be conducted for verification.

[0175] Example 9

[0176] This embodiment provides an application scenario example of a dual-cavity coupled reaction force generator, as detailed below:

[0177] Taking the static load test of pile foundations in the narrow space under the bridge as an example, the traditional surcharge method cannot be implemented due to the height limitation of the space under the bridge.

[0178] The testing site is natural soil with no concrete surface. First, an annular trench is excavated on the foundation surface 3. The trench is 0.8 meters deep and 5 centimeters wider than the wall thickness of the rigid inner cylinder 4. A composite sealing membrane is laid in the trench as the sealing layer 2. The composite sealing membrane consists of two layers of high-density polyethylene film sandwiched with a bentonite waterproof layer. The sealing layer extends from the outer perimeter of the outer cylinder through the annular trench to the test pile body.

[0179] The rigid inner cylinder 4 is made of Q345B steel with an outer diameter of 1.2 meters. The wall thickness is determined by external pressure stability calculation to meet the working pressure requirement of 6MPa. The rigid inner cylinder 4 is pressed into the annular groove. The sealing layer 2 wraps the bottom outer wall and bottom surface of the rigid inner cylinder. Then, the rigid outer cylinder 1 is hoisted and sleeved on the outside of the rigid inner cylinder 4. The sealing layer is pressed tightly at the bottom of the outer cylinder. The part of the sealing layer extending to the test pile is wrapped around the outer wall of the pile body and fixed with clamps. Finally, the outward flange 15 at the bottom of the outer cylinder is locked and connected to the spiral anchor pile 16.

[0180] The air pipe 8 passes through the side wall of the rigid outer cylinder 1, and a high-pressure sealing joint is provided at the penetration point, connecting the pressurized fluid source 7 and the annular sealing cavity 6. The vacuum pipe 10 is led out from the side wall of the rigid inner cylinder 4 and passes through the side wall of the outer cylinder 1, and a vacuum sealing joint is provided at the penetration point, connecting the vacuum pump 11 and the vacuum chamber 9.

[0181] Spiral anchor piles are used as the anchoring structure. Six spiral anchor piles are evenly arranged around the rigid outer cylinder and driven into the soil to a depth of about 2.5 meters using a hydraulic torsion device. The upper end of the spiral anchor pile is fixedly connected to the outward flange through a connector.

[0182] The rigid outer cylinder has a diameter of approximately 1.5 meters and an overall height of approximately 1.2 meters, which is perfectly suited to the space under the bridge. The rigid inner cylinder is evacuated to -0.095 MPa, and the pressure of the annular sealed cavity is set to 3 MPa, approximately 30 atmospheres. The calculated total thrust is approximately 330 tons, which meets the testing requirements of medium-sized pile foundations.

[0183] After the test, the high pressure in the annular cavity was first released, then the vacuum was broken, the connection between the outward flange and the spiral anchor pile was disconnected, the outer cylinder was lifted off, the rigid inner cylinder was pulled out, the sealing layer was recovered, and the site was restored to its original state. The entire device only requires a vacuum pump and an air compressor to operate, eliminating the need to transport a large amount of counterweight, and the construction period was greatly shortened.

[0184] Example 10

[0185] This embodiment provides experimental verification data for a dual-cavity coupled reaction force generator, as detailed below:

[0186] For the same rigid inner cylinder dimensions, with an inner diameter of 1.0 meter and an outer diameter of 1.1 meters, the thrust obtained by the top of the jack was tested in both pure vacuum mode and dual-cavity coupling mode:

[0187] 1. Pure vacuum mode, only the rigid inner cylinder is evacuated, vacuum degree 0.095MPa: , Approximately 7.6 tons;

[0188] 2. Dual-cavity coupling mode: rigid inner cylinder vacuuming and annular cavity pressurization to 3MPa. , Approximately 290 tons, total thrust Approximately 298 tons;

[0189] Experimental data show that, under the same rigid inner cylinder size, the thrust of the dual-cavity coupling mode is about 39 times that of the pure vacuum mode, which fully demonstrates the innovation and practicality of the present invention in obtaining the reaction force multiplication effect through the dual-cavity coupling and superposition of the vacuum cavity and the pressure cavity.

[0190] Example 11

[0191] This embodiment provides the materials and manufacturing process of the dual-cavity coupled reaction force generating device, as detailed below:

[0192] As a preferred option, both the rigid outer cylinder 1 and the rigid inner cylinder 4 are made of high-strength steel, such as Q345B or higher grade. The wall thickness of the rigid inner cylinder is determined by external pressure stability verification: when the maximum working pressure of the annular sealing cavity 6 is 6MPa, the wall thickness of the rigid inner cylinder must meet the requirement that the critical pressure for external pressure instability is greater than 1.5 times the maximum working pressure, and the opening pressure of the safety pressure relief device 17 is set to 6.5MPa.

[0193] The bottom edge of the rigid inner cylinder 4 is rounded with a radius of not less than 5mm to prevent the sealing layer 2 from being punctured or scratched when pressed into the annular groove.

[0194] The outward-facing flange 15 is made of forged steel, and the working surface is hardened to ensure wear resistance and load-bearing capacity under repeated use.

[0195] The spiral anchor piles are made of high-strength steel pipes, with spiral blades no less than 10mm thick and the surface treated with anti-corrosion coating to adapt to different soil conditions.

[0196] The sealing layer 2 is made of high-density polyethylene film or composite sealing film, and the thickness is determined according to the design pressure and foundation surface conditions.

[0197] Both the gas pipe 8 and the vacuum line 10 are made of high-pressure seamless steel pipes. The through-wall sealing joints with the side wall of the cylinder adopt a conical sealing structure. The sealing elements of the sealing joints are made of high-pressure resistant and corrosion-resistant polytetrafluoroethylene or metal gaskets to ensure long-term reliable sealing under high pressure and vacuum conditions.

[0198] In summary, the present invention has a compact structure, clear force distribution, flexible operation, and high safety. It can generate a large-tonnage reaction force in a confined space through dual-cavity coupling without relying on large counterweights and anchor piles.

[0199] The core of this invention lies in a three-dimensional sealing structure consisting of a continuous sealing diaphragm, an annular sealing groove, a flexible sealing layer, and a rigid inner cylinder pressed in. The sealing layer extends from the outer periphery of the outer cylinder through the annular groove to the test pile, forming a complete continuous diaphragm. This directly achieves sealing at the bottom of the outer cylinder, the bottom of the annular groove, the lateral sealing of the rigid inner cylinder, and the sealing at the test pile on a natural soil foundation. It requires no concrete foundation, no additional dynamic sealing components, and no guiding mechanism, making the structure simple and reliable.

[0200] The pipe penetration sealing design is reasonable. Both gas pipes and vacuum pipes pass through the side wall of the cylinder without damaging the continuity of the bottom sealing layer. A special sealing joint is set at the wall penetration point to ensure the sealing reliability under high pressure and vacuum conditions.

[0201] Meanwhile, by diversifying the anchoring structure, using helical anchor piles or ground anchors as anchoring solutions on natural soil foundations, there is no need to pre-embed concrete foundations, making construction convenient and reusable.

[0202] This invention has broad site adaptability and significant industrial practical value, and is particularly suitable for pile foundation testing in confined spaces such as urban bridges, underground engineering, and tunnels.

[0203] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

[0204] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only independent technical solutions. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A dual-cavity coupled reaction force generating device, characterized in that, include: Foundation surface (3), on which test piles are provided; A rigid outer cylinder (1) is connected at its bottom to the foundation surface (3); A rigid inner cylinder (4) is coaxially arranged inside the rigid outer cylinder (1). The rigid inner cylinder (4) covers the outside of the test pile on the foundation surface (3). A jack (5) is coaxially arranged inside the rigid inner cylinder (4). The bottom of the jack (5) is installed on the test pile. The top of the rigid inner cylinder (4) abuts against the top of the piston rod of the jack (5). An annular sealed cavity (6) is formed between the rigid outer cylinder (1) and the rigid inner cylinder (4), and the annular sealed cavity (6) is connected to a pressurized fluid source (7). The rigid inner cylinder (4) has a vacuum chamber (9) inside, and the vacuum chamber (9) is connected to a vacuum pumping device (11). The base surface (3) is located at the bottom of the rigid outer cylinder (1) and the rigid inner cylinder (4) and is covered with a sealing layer (2).

2. The dual-cavity coupled reaction force generating device according to claim 1, characterized in that, An annular groove is provided on the base surface (3), and the position of the annular groove corresponds to the position of the cylinder wall of the rigid inner cylinder (4); The sealing layer (2) is laid inward from the base surface (3) of the outer periphery of the rigid outer cylinder (1), passing in sequence below the bottom of the rigid outer cylinder (1), the annular groove, below the bottom of the rigid inner cylinder (4), and extending to the test pile; The sealing layer (2) is a single-layer sealing film or a multi-layer composite sealing film structure and uses a flexible airtight material. The thickness of the single-layer sealing film is 0.12~0.16mm, and the total thickness of the multi-layer composite sealing film is 0.5~2.0mm.

3. The dual-cavity coupled reaction force generating device according to claim 2, characterized in that, When the sealing layer (2) is a single-layer sealing membrane structure, the flexible airtight material used includes polyethylene film or rubber sheet; When the sealing layer (2) is a multi-layer composite sealing membrane structure, the flexible airtight material used includes two layers of polyethylene membrane and a bentonite waterproof layer sandwiched between the two membranes. The sealing layer (2) covers the bottom and two sides of the annular groove to form a U-shaped sealing lining. The depth of the annular groove is 0.5 to 1.5 meters, and the width of the annular groove is 4 to 8 centimeters greater than the wall thickness of the rigid inner cylinder (4). The bottom wall of the rigid inner cylinder (4) is pressed into the annular groove, and the sealing layer (2) wraps the bottom outer wall and bottom surface of the rigid inner cylinder (4); The bottom of the rigid outer cylinder (1) is pressed tightly against the sealing layer (2).

4. The dual-cavity coupled reaction force generating device according to claim 3, characterized in that, The bottom edge of the rigid inner cylinder (4) is provided with a rounded corner structure to protect the sealing layer (2) from being punctured when it is pressed into the annular groove; The bottom edge of the rigid outer cylinder (1) is provided with an outward flange (15), and the foundation surface (3) is provided with an anchoring structure (16). The outward flange (15) is detachably locked to the anchoring structure (16) to provide a downward mechanical constraint force to the rigid outer cylinder (1) when high pressure is applied in the annular sealing cavity (6) to balance the upward buoyancy generated by the high pressure.

5. The dual-cavity coupled reaction force generating device according to claim 4, characterized in that, The anchoring structure (16) is a spiral anchor pile, a ground anchor, or an anchor rod; When the anchoring structure is a spiral anchor pile, the spiral anchor pile is screwed into the foundation soil by a torsion device, and then connected to the outward flange (15) by a connector; When the anchoring structure is a ground anchor or an anchor rod, the ground anchor or anchor rod is driven into the foundation soil and then connected to the outward flange (15) by a tie rod.

6. The dual-cavity coupled reaction force generating device according to claim 4, characterized in that, The wall thickness of the rigid inner cylinder (4) meets the external pressure stability requirements, and its external pressure instability critical pressure The pressure is greater than 1.5 times the maximum working pressure of the annular sealing cavity (6), that is: ； in, The elastic modulus of the rigid inner cylinder material. Poisson's ratio, For rigid inner cylinder wall thickness, The outer diameter of the rigid inner cylinder This is the maximum working pressure of the annular sealed cavity.

7. The dual-cavity coupled reaction force generating device according to claim 1, characterized in that, The pressurized fluid source (7) is connected to the annular sealed cavity (6) through the air pipe (8). The air pipe (8) passes through the side wall of the rigid outer cylinder (1) and a sealing joint is provided at the penetration point. The pressurized fluid source (7) is an air compressor, a high-pressure gas cylinder or a hydraulic pump station, used to inject compressed gas or hydraulic oil into the annular sealed cavity (6); The vacuum pumping device (11) is connected to the vacuum chamber (9) through the vacuum pipeline (10). The vacuum pipeline (10) is led out from the side wall of the rigid inner cylinder (4) and passes through the side wall of the rigid outer cylinder (1). A vacuum sealing joint is provided at the penetration point.

8. The dual-cavity coupled reaction force generating device according to claim 1, characterized in that, It also includes a pressure monitor (12), a vacuum gauge (13) and a data acquisition device (14) installed outside the rigid outer cylinder (1), as well as a safety pressure relief device (17) installed on the top of the rigid outer cylinder (1). The air pressure monitor (12) is connected to the annular sealed cavity (6) for real-time monitoring of the pressure inside the annular sealed cavity (6); The vacuum gauge (13) is connected to the vacuum chamber (9) and is used to monitor the vacuum level inside the vacuum chamber (9); The data acquisition instrument 14 is used to record the data collected by the barometer (12) and the vacuum gauge (13); The safety pressure relief device (17) is connected to the annular sealing cavity (6). The safety pressure relief device (17) is a safety valve or a rupture disc, and its opening pressure setting value is higher than the maximum working pressure of the annular sealing cavity (6).

9. The application method of the dual-cavity coupled reaction force generating device according to any one of claims 1-8 in pile foundation testing, characterized in that, Includes the following steps: S1. Open an annular groove on the base surface (3), remove sharp foreign objects from the groove, and make the bottom of the groove basically flat. S2. Lay the sealing layer (2), starting from the foundation surface (3) of the outer perimeter of the rigid outer cylinder (1), passing through the bottom of the outer cylinder, the annular groove, the bottom of the rigid inner cylinder, and extending to the test pile. Wrap the part of the sealing layer (2) extending to the test pile around the outer wall of the test pile and fix it with clamps or binding to ensure that the sealing layer (2) is tightly attached to the pile body. The sealing layer (2) covers the bottom of the groove and the two sides of the groove to form a U-shaped lining. S3. Press the bottom wall of the rigid inner cylinder (4) into the annular groove so that the sealing layer (2) wraps the bottom outer wall and bottom surface of the rigid inner cylinder (4); S4. Hoist the rigid outer cylinder (1) into place and fit it on the outside of the rigid inner cylinder (4) so ​​that the bottom of the outer cylinder is pressed against the sealing layer (2), and at the same time the bottom outward flange (15) is locked to the anchoring structure (16). S5. Start the vacuum pumping device (11) to evacuate the vacuum chamber (9) inside the rigid inner cylinder (4). The external atmospheric pressure will press the rigid inner cylinder (4) against the sealing layer (2), so that the bottom of the rigid inner cylinder and the sealing layer (2) at the bottom of the annular groove form a bottom seal, and at the same time press the rigid outer cylinder (1) against the sealing layer to form a bottom seal of the outer cylinder. S6. The compressed medium is injected into the annular sealed cavity (6) through the pressurized fluid source (7) and the air pipe (8) until the target pressure is reached. The sealing layer (2) wraps the outer side of the rigid inner cylinder wall to form a lateral seal. At the same time, the annular cavity and the vacuum chamber are isolated by the rigid inner cylinder solid wall. S7. Start the jack (5) to conduct a loading test; S8. After the test, first open the safety relief device (17) to release the compressed medium in the annular sealed cavity (6). After the pressure in the cavity drops to atmospheric pressure, then break the vacuum in the vacuum chamber (9). S9. Disconnect the outer flange (15) from the anchoring structure (16), lift off the rigid outer cylinder (1), pull out the rigid inner cylinder (4), and recover the sealing layer (2).

10. The application method of the dual-cavity coupled reaction force generating device according to claim 9 in pile foundation testing, characterized in that, In step S5, the pressure established by the vacuum pumping device (11) during vacuuming, the weight of the rigid inner cylinder (4), and the upward buoyancy force generated by the high pressure in the annular sealed cavity (6) on the rigid inner cylinder (4) in step S6 satisfy the following relationship: The combined force of the pressure created by vacuuming and the weight of the rigid inner cylinder (4) is greater than the upward buoyancy, ensuring that the rigid inner cylinder (4) remains pressed tightly against the sealing layer (2) throughout the entire loading process.

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