Boundary and saturation controllable CPTU calibration test device and method

Abstract

The invention relates to the technical field of testing, in particular to a boundary and saturation controllable CPTU calibration test device and method.The calibration test device comprises a calibration groove, a consolidation system, a penetration system, a saturation adjusting system and a control and data acquisition system, and the consolidation system comprises a consolidation plate and a consolidation oil cylinder; a bending unit sensor is arranged on the lower side of the consolidation plate, the penetration system comprises a penetration probe and a penetration oil cylinder, the saturation adjusting system comprises a permeable stone located at the lower end of the calibration groove, a water pressure controller and an air pressure controller, and the control and data acquisition system controls stretching and retracting of the consolidation oil cylinder and the penetration oil cylinder through a hydraulic server. And the conical tip resistance, the side wall friction resistance and the pore pressure of the penetration probe, the wave velocity data of the bending unit sensor, and the water pressure and air pressure data of the water pressure controller and the air pressure controller are recorded and collected through a data collector. The calibration test device and the calibration test method are simple to operate and accurate in measurement, and are integrated with a wave velocity test.

Description

Technical Field

[0001] The present invention relates to the field of testing technology, and in particular to a CPTU calibration test device and method with controllable boundaries and saturation. Background Art

[0002] As an effective in-situ testing method, the pore pressure cone penetration test (CPTU) boasts high precision and excellent stability. It can quickly and accurately determine stratum structure and state, playing a crucial role in geotechnical engineering investigations and the acquisition of geotechnical parameters. With the development of technologies such as CPTU, wave velocity testing has been incorporated into CPTU, enabling the acquisition of soil-related deformation moduli and providing effective guidance for determining the initial state of soil samples. Calibration testing is a key method for conducting detailed interpretation and analysis of soil parameters based on CPTU. Combined with geotechnical testing, it provides crucial support for the acquisition, analysis, and evaluation of soil physical, mechanical, and deformation properties.

[0003] Current CPTU calibration devices mostly use rigid walls, making it difficult to effectively simulate diverse boundary conditions. Test soil samples may be fully saturated, partially saturated, or have uncontrollable saturation. For partially saturated test soil samples, the impact of suction on the interpretation algorithm remains a technical gap. Furthermore, further research is needed on the preparation of undisturbed samples based on wave velocity test results and the CPTU interpretation algorithm based on this. Therefore, it is urgent to develop a corresponding test device to conduct CPTU calibration tests with controllable boundaries and saturation, while also allowing for simultaneous wave velocity testing, thereby improving the precision and accuracy of static penetration test interpretation and analysis. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, the present invention proposes a CPTU calibration test device and method with controllable boundaries and saturation, which is simple to operate and accurate in measurement, and incorporates wave velocity testing, thereby solving the above-mentioned technical problems existing in the existing technology.

[0005] The present invention provides a CPTU calibration test device and method with controllable boundaries and saturation, which adopts the following technical solutions: A CPTU calibration test device with controllable boundaries and saturation, comprising a calibration tank, a consolidation system, a penetration system, a saturation adjustment system, and a control and data acquisition system, wherein the calibration tank comprises an outer cylinder with an axis extending in the vertical direction and an inner cylinder coaxially arranged in the outer cylinder, wherein the inner cylinder is used to accommodate a soil sample, the consolidation system comprises a consolidation plate and a consolidation oil cylinder for driving the consolidation plate to rise and fall, the consolidation plate presses down the soil sample to consolidate the soil sample, a bending unit sensor is provided on the lower side of the consolidation plate, the penetration system comprises a penetration probe and a penetration oil cylinder for driving the penetration probe to rise and fall, a penetration hole for the penetration probe to pass through is opened in the middle of the consolidation plate, the saturation adjustment system comprises a permeable stone located at the bottom of the inner cylinder, and respectively A water pressure controller and an air pressure controller are connected to the upper and lower ends of the calibration tank. The water pressure controller is used to inject degassed water into the calibration tank to control the water pressure in the calibration tank. The air pressure controller is used to inject inert gas into the calibration tank to control the air pressure in the calibration tank. The control and data acquisition system includes a computer. The computer controls the extension and contraction of the consolidation cylinder and the penetration cylinder through a hydraulic servo, and records and collects the cone tip resistance, side wall friction resistance, pore pressure, wave velocity data of the bending unit sensor of the penetration probe, and the water pressure and air pressure data of the water pressure controller and the air pressure controller through a data collector. The calibration test device can control the boundary stress conditions and saturation of the soil sample, and obtain the deformation characteristics of the soil sample based on the wave velocity test.

[0006] Furthermore, the inner cylinder is surrounded by a plurality of arc-shaped plates, and the plurality of arc-shaped plates are respectively located on the periphery of the consolidation plate. The outer side of each arc-shaped plate is connected to a horizontally extending push-pull rod, and the push-pull rod can drive each arc-shaped plate to move back and forth along the radial direction of the inner cylinder so that the arc-shaped plate can be pressed against or loosened from the soil sample. The interior of the inner cylinder is provided with a rubber membrane for being sleeved on the periphery of the soil sample. When each arc-shaped plate is pressed against the soil sample, each arc-shaped plate forms a rigid boundary around the soil sample. When each arc-shaped plate loosens the soil sample, the rubber membrane forms a flexible boundary around the soil sample.

[0007] Furthermore, there is a peripheral cavity between the inner side of the outer cylinder and the outer side of the inner cylinder, and the side wall of the outer cylinder is provided with an injection and drainage port. When each arc plate loosens the soil sample, the injection and drainage port is used for the liquid in the peripheral cavity to enter and exit.

[0008] Furthermore, a base is provided at the lower end of the outer cylinder, and an upper cover is provided at the upper end. A plurality of threaded rods are connected between the base and the upper cover on the periphery of the outer cylinder to seal and reinforce the calibration groove.

[0009] Furthermore, upper through holes are correspondingly provided on the upper cover and the consolidation plate, an upper switch valve is provided in the upper through hole, the upper through hole is connected to the air pressure controller through an air pipe, the air pressure controller is filled with inert gas or incompletely inert gas, a first water flow channel and a second water flow channel are provided on the base, two water pressure controllers are provided, namely the first water pressure controller and the second water pressure controller, one end of the first water flow channel is located below the permeable stone, and the other end is connected to the first water pressure controller, one end of the second water flow channel is located between the outer cylinder and the inner cylinder and is connected to the outer cavity, and the other end is connected to the second water pressure controller.

[0010] Furthermore, a gantry is provided on the base at the periphery of the calibration groove, the consolidation cylinder and the penetration cylinder are respectively installed on the top of the gantry, the lower end of the penetration cylinder is connected to the penetration probe, the upper side of the consolidation plate is connected to a connecting rod extending in the up and down directions, the consolidation cylinder is connected to the upper end of the connecting rod, and a lifting cylinder is also installed on the top of the gantry, and the lower end of the lifting cylinder is connected to the upper cover to drive the upper cover to rise and fall.

[0011] Furthermore, when the consolidation plate presses the soil sample, a rod extending in the up-down direction is inserted into the penetration hole, and the lower end of the rod is flush with the lower side of the consolidation plate. The rod is used to seal the penetration hole.

[0012] Furthermore, a through-hole corresponding to the upper and lower penetration holes is opened in the middle of the upper cover. After the soil sample is pressed under the consolidation plate, the rod is removed from the consolidation plate. The first bushing and the second bushing are respectively connected to the penetration hole and the through-hole, and the penetration probe passes through the first bushing and the second bushing in sequence from top to bottom.

[0013] Furthermore, the lower side of the upper cover and the upper side of the base are respectively provided with embedding grooves that are plugged into the upper and lower ends of the outer cylinder, and sealing rings are respectively provided in the embedding grooves. The upper and lower ends of each arc plate are respectively provided with sealing gaskets that are sealed with the lower side of the upper cover and the upper side of the base.

[0014] A CPTU calibration test method with controllable boundaries and saturation uses the above-mentioned CPTU calibration test device with controllable boundaries and saturation, and includes the following steps: loading a set amount of soil sample with a certain moisture content into an inner cylinder, consolidating the soil sample by pressing down a consolidation plate with a consolidation cylinder; after consolidation, penetrating a penetration probe through the consolidation plate and into the soil sample; during the penetration process, recording the values of the penetration probe's cone tip resistance, side wall friction resistance, pore pressure, and bending unit sensor wave velocity test in real time through a data collector, and displaying them as curves on a computer; adjusting the water pressure and air pressure in the calibration tank through an air pressure controller and a water pressure controller to control the soil sample suction, and then achieving the target saturation by combining the water retention curve of the soil sample under the same conditions.

[0015] The beneficial effects of the present invention are as follows: the CPTU calibration test device and method with controllable boundaries and saturation of the present invention have a relatively simple structure and are flexible and convenient to operate. They can control and change the stress conditions and saturation of the soil sample boundaries, and simultaneously obtain the deformation characteristics of the soil based on wave velocity testing, which makes up for the shortcomings of existing test devices and methods in this research field, helps to further improve the precision and accuracy of static penetration test interpretation and analysis, and thus effectively guide engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work. Those skilled in the art should understand that these drawings are not necessarily drawn to scale.

[0017] Figure 1 This is an overall schematic diagram of an embodiment of a CPTU calibration test device with controllable boundaries and saturation according to the present invention; Figure 2 This is a schematic diagram of a calibration tank in one embodiment of a CPTU calibration test device with controllable boundaries and saturation according to the present invention.

[0018] In the figure: 0, first water pressure controller; 1, second water pressure controller; 2, air pressure controller; 3, lifting cylinder; 4, consolidation cylinder; 5, penetration cylinder; 6, gantry; 7, threaded rod; 8, push-pull rod; 9, outer cylinder; 10, inner cylinder; 11, rubber membrane; 12, penetration probe; 13, permeable stone; 14, hydraulic servo; 15, computer; 16, data acquisition device; 17, first water flow channel; 18, injection and drainage outlet; 19, outer cavity; 20, sealing ring; 21, upper through hole; 22, upper cover; 23, base; 24, consolidation plate; 25, first bushing; 26, bending unit sensor; 27, rod; 28, connecting rod; 29, second bushing; 30, second water flow channel. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] The serial numbers assigned to components herein, such as "first," "second," etc., are used solely to distinguish the objects being described and do not convey any sequential or technical meaning. References to "connection" and "coupling" herein, unless otherwise specified, include both direct and indirect connections (couplings). In the description of the present invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like, indicating positions or relationships, are based on those shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the device or element referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention.

[0021] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0022] An embodiment of a CPTU calibration test device with controllable boundaries and saturation according to the present invention is as follows: Figures 1 to 2 As shown, the CPTU calibration test apparatus with controllable boundaries and saturation includes a calibration tank, a consolidation system, a penetration system, a saturation adjustment system, and a control and data acquisition system. In this embodiment, the calibration tank is made of stainless steel and has two layers: an outer cylinder 9 with an axis extending vertically and an inner cylinder 10 coaxially disposed within the outer cylinder 9. The inner cylinder 10 is used to accommodate soil samples. In this embodiment, the entire calibration tank has an outer diameter of 1.0 m and a height of 1.2 m. The consolidation system includes a consolidation plate 24 and a consolidation cylinder 4 for driving the consolidation plate 24 upward and downward. The consolidation plate 24 presses down on the soil sample to provide consolidation stress, thereby consolidating the sample. In this embodiment, the consolidation plate 24 can provide a maximum consolidation stress of 500 kPa. During the consolidation process, the soil sample will drain outward in a unidirectional manner. A bending unit sensor 26 is installed on the underside of the consolidation plate 24 to obtain wave velocity data from the soil sample.

[0023] The penetration system includes a penetration probe 12 and a penetration cylinder 5 for driving the penetration probe 12 to rise and fall. A penetration hole is opened in the middle of the consolidation plate 24 for the penetration probe 12 to pass through. When working, the penetration probe 12 passes through the penetration hole on the consolidation plate 24 and penetrates into the soil sample below. In this embodiment, the penetration cylinder 5 can provide a maximum penetration force of 200KN. The penetration probe 12 has a cross-sectional area of 15cm 2 The standard CPTU probe can achieve simultaneous measurement of cone tip resistance, side wall friction resistance, and pore pressure. It should be noted that cone tip resistance refers to the resistance value encountered by the cone tip at the lower end of the penetration probe 12 during the downward penetration of the soil sample; side wall friction resistance refers to the friction resistance value encountered by the side wall of the penetration probe 12 during the downward penetration of the soil sample; and pore pressure refers to the soil sample pressure value experienced by the penetration probe 12 during the downward penetration of the soil sample.

[0024] In this embodiment, the saturation adjustment system includes a permeable stone 13 located at the bottom of the inner tube 10, and a water pressure controller and an air pressure controller 2 connected to the upper and lower ends of the calibration tank, respectively. In this embodiment, a bending unit sensor 26 is also provided on the upper side of the permeable stone 13, and the positions of the bending unit sensor 26 on the consolidation plate 24 and the permeable stone 13 correspond to each other. The water pressure controller and the air pressure controller 2 are both piston cylinders. The water pressure controller is filled with degassed water, and the air pressure controller 2 is filled with inert gas, specifically nitrogen. The water pressure controller is used to inject degassed water into the calibration tank to control the water pressure therein, and the air pressure controller 2 is used to inject inert gas into the calibration tank to control the air pressure therein.

[0025] The control and data acquisition system includes a computer 15, which controls the extension and contraction of the consolidation cylinder 4 and the penetration cylinder 5 through the hydraulic servo 14. At the same time, the computer 15 also records and collects the cone tip resistance, side wall friction resistance, pore pressure, and wave velocity data of the bending unit sensor 26 of the penetration probe 12, as well as the water pressure and air pressure data of the water pressure controller and the air pressure controller 2 through the data acquisition device 16.

[0026] In this embodiment, the inner cylinder 10 is surrounded by a plurality of curved plates, specifically four of which are located on the periphery of the consolidation plate 24 and the permeable stone 13. The consolidation plate 24 and the permeable stone 13 correspond to each other vertically and have the same outer diameter. A horizontally extending push-pull rod 8 is connected to the outer side of each curved plate. The push-pull rod 8 is capable of driving each curved plate to reciprocate along the radial direction of the inner cylinder 10. Specifically, the outer cylinder 9 is provided with threaded holes corresponding to the push-pull rods 8. The push-pull rods 8 are rotatably mounted in the corresponding threaded holes. When the push-pull rods 8 are rotated, they are screwed in and out along the radial direction of the outer cylinder 9, thereby driving each curved plate to move radially along the inner cylinder 10. When the push-pull rod 8 drives each arc plate to move to the innermost position inside the inner tube 10, the inner wall of each arc plate is tightly attached to the periphery of the soil sample. When the push-pull rod 8 drives each arc plate to move to the outermost position outside the inner tube 10, each arc plate releases the soil sample. When each arc plate is tightly attached to or loosens the soil sample, rigid wall test and flexible wall test can be performed on the soil sample.

[0027] In this embodiment, the inner tube 10 is provided with a rubber membrane 11 for wrapping around the soil sample. The rubber membrane 11 is cylindrical and closed. When the curved plates are pressed against the soil sample, they form a rigid boundary around the soil sample, allowing a rigid wall test to be performed on the soil sample. When the curved plates are released from the soil sample, the rubber membrane 11 forms a flexible boundary around the soil sample, allowing a flexible wall test to be performed on the soil sample. In this embodiment, a peripheral cavity 19 is defined between the inner side of the outer tube 9 and the outer side of the inner tube 10. A water inlet and outlet 18 is provided on the side wall of the outer tube 9. When the curved plates are released from the soil sample, i.e., when a flexible wall test is performed on the soil sample, the water inlet and outlet 18 is opened to allow liquid to flow in and out of the peripheral cavity 19. When a rigid wall test is performed on the soil sample, the water inlet and outlet 18 does not need to be opened.

[0028] In this embodiment, the outer tube 9 is provided with a base 23 at its lower end and an upper cover 22 at its upper end. Multiple threaded tie rods 7 are connected between the base 23 and the upper cover 22 on the periphery of the outer tube 9 to seal and reinforce the calibration groove. Upper through holes 21 are correspondingly formed on the upper cover 22 and the consolidation plate 24. An upper on-off valve is provided within the upper through hole 21. The upper through hole 21 is connected to the air pressure controller 2 via an air pipe. The air pressure controller 2 is filled with an inert gas or a partially inert gas. The base 23 is provided with a first water flow channel 17 and a second water flow channel 30. Two water pressure controllers are provided, namely, the first water pressure controller 0 and the second water pressure controller 1. One end of the first water flow channel 17 is located below the permeable stone 13, and the other end is connected to the first water pressure controller 0. One end of the second water flow channel 30 is located between the outer tube 9 and the inner tube 10 and communicates with the peripheral cavity 19, and the other end is connected to the second water pressure controller 1. During the process of the consolidation plate 24 pressing down the soil sample to consolidate the soil sample, moisture will be discharged from the soil sample. At this time, the first water flow channel 17 is disconnected from the first water pressure controller 0. The discharged moisture will be discharged outside the calibration tank through the permeable stone 13 at the bottom of the inner tube 10 and the first water flow channel 17. After the consolidation is completed, the first water flow channel 17 is connected to the first air pressure controller 2.

[0029] In this embodiment, a gantry 6 is provided on the base 23 on the periphery of the calibration groove, and the consolidation cylinder 4 and the penetration cylinder 5 are respectively installed on the top of the gantry 6, and the lower end of the penetration cylinder 5 is connected to the penetration probe 12. The upper side of the consolidation plate 24 is connected to a connecting rod 28 extending in the up-down direction, and the consolidation cylinder 4 is connected to the upper end of the connecting rod 28. A lifting cylinder 3 is also installed on the top of the gantry 6, and the lower end of the lifting cylinder 3 is connected to the upper cover 22 to drive the upper cover 22 to rise and fall. When the consolidation plate 24 presses down the soil sample, a rod 27 extending in the up-down direction is inserted into the penetration hole, and the lower end of the rod 27 is flush with the lower side of the consolidation plate 24. The rod 27 is used to seal the penetration hole. The upper cover 22 is provided with a perforation in the middle portion corresponding to the upper and lower portions of the penetration hole. After the consolidation plate 24 has finished pressing the soil sample, the rod 27 is removed from the consolidation plate 24. The penetration hole and the perforation are connected to the first bushing 25 and the second bushing 29, respectively. The penetration probe 12 passes through the first bushing 25 and the second bushing 29 in sequence from top to bottom. The inner walls of the first bushing 25 and the second bushing 29 are provided with rubber rings to achieve a seal between the first bushing 25 and the second bushing 29 and the penetration probe 12, ensuring that the degassed water used to apply the confining pressure does not overflow out of the calibration tank through the penetration hole and the perforation. In this embodiment, the penetration hole and the perforation are both threaded holes, and the lower end of the rod 27 is an externally threaded section. During the consolidation process of the soil sample, the externally threaded section at the lower end of the rod 27 passes through the perforation on the upper cover 22 and is threadedly connected to the penetration hole. When the consolidation is completed, the rod 27 is rotated to remove the rod 27 from the penetration hole. External threads are provided on the outer sides of the first bushing 25 and the second bushing 29. After the rod 27 is removed, the first bushing 25 and the second bushing 29 are screwed into the through hole and the penetration hole respectively.

[0030] In this embodiment, to enhance sealing, the underside of the upper cover 22 and the upper side of the base 23 are provided with grooves that engage with the upper and lower ends of the outer cylinder 9. These grooves are fitted with sealing rings 20, each capable of withstanding a pressure of at least 20 MPa. Furthermore, each curved plate is provided with sealing gaskets at its upper and lower ends, respectively, that engage with the underside of the upper cover 22 and the upper side of the base 23.

[0031] The present invention uses the above-mentioned test method of the CPTU calibration test device with controllable boundaries and saturation. The specific steps during the test are as follows: a. Debug and calibrate the hydraulic servo 14, the lifting cylinder 3, the consolidation cylinder 4, the penetration cylinder 5, and the two bending unit sensors 26, and then test the penetration probe 12. Fill the water pressure controller with degassed water and the air pressure controller 2 with nitrogen.

[0032] b. Assemble and fix the outer cylinder 9 of the calibration tank on the base 23. The four arc-shaped plates of the inner cylinder 10 are respectively connected to the four horizontal push-pull rods 8. Keep the upper cover 22 of the calibration tank in the open state and the consolidation plate 24 in the raised state.

[0033] c. Prepare a soil sample with a certain moisture content according to the test requirements, put the cylindrical rubber membrane 11 on the base 23, push the curved plates of the inner cylinder 10 to the innermost position and tightly fit the outer edge of the permeable stone 13. In this step, the outer cavity 19 between the outer cylinder 9 and the inner cylinder 10 can be vacuumed to achieve the side wall of the rubber membrane 11 tightly fitting on the inner wall of the inner cylinder 10.

[0034] d. Load a predetermined amount of soil sample into the rubber membrane 11. Lower the consolidation plate 24 via the consolidation cylinder 4 until it contacts the top of the soil sample, and then fit the upper end of the rubber membrane 11 over the consolidation plate 24. If a rigid boundary is desired around the soil sample, the four curved plates of the inner cylinder 10 can be brought into close contact with the soil sample during this step. If a flexible boundary is desired, the curved plates can be separated from the soil sample by rotating the horizontal push-pull rod 8.

[0035] e. Lower the calibration tank's upper cover 22 by lifting the oil cylinder 3, ensuring it fits tightly against the upper ends of the outer and inner cylinders 9 and 10. Threaded tie rods 7 securely seal the upper cover 22 and base 23 along the outer edge of the calibration tank. Insert a rod 27 with an externally threaded section at its lower end through the perforation of the upper cover 22 and screw it into the central penetration hole of the consolidation plate 24. Ensure the lower end of the rod 27 is flush with the underside of the consolidation plate 24. Rod 27 seals the penetration hole in the consolidation plate 24, maintaining a flat surface during the consolidation process.

[0036] f. The soil sample is consolidated by pressing down the consolidation plate 24 through the consolidation cylinder 4. During the consolidation process, the first water flow channel 17 at the bottom of the calibration tank is kept disconnected from the first water pressure controller 0 and in an open state. The first water flow channel 17 is connected to the drain pipe to drain water outward.

[0037] g. After consolidation is complete, connect the first water flow channel 17 to the first water pressure controller 0, and connect the upper through-hole 21 on the upper cover 22 and the consolidation plate 24 to the air pressure controller 2. Unscrew the rod 27 and screw on the threaded first bushing 25 and second bushing 29 from the inside out. Pass the penetration probe 12 through the first bushing 25 and second bushing 29 in sequence to contact the soil sample.

[0038] h. If the soil sample is unsaturated soil, the suction of the soil sample can be directly controlled by adjusting the water pressure and air pressure in the first water pressure controller 0 and the air pressure controller 2, and then the target saturation can be achieved by combining the water retention curve under the same conditions of the soil sample.

[0039] i. When conducting a flexible boundary test, degassed water can be injected into the calibration tank through the water injection and drainage port 18, and the target confining pressure in the calibration tank can be controlled by the second water pressure controller 1. If a rigid boundary test is performed, this operation is not required. It is only necessary to use the push-pull rod 8 to keep the four curved plates of the inner tube 10 in the same position and close to the soil sample.

[0040] j. Control the penetration probe 12 downward through the soil sample using the penetration cylinder 5 at a constant speed. Before penetration, perform a wave velocity test on the soil sample using the bending unit sensor 26 and compare the results with the in-situ test results. If the results are nearly identical, the soil sample is considered to be essentially consistent with the in-situ state. If the discrepancy is significant, repeat steps 5-9 until they are essentially identical. During the penetration process, the data logger 16 records the probe's 12 tip resistance, sidewall friction, pore pressure, and wave velocity test values throughout the entire process in real time, displaying them as a graph on the computer screen.

[0041] k. Multiple calibration tests can be conducted by changing the soil sample type, stress and boundary conditions, penetration rate, and saturation, and repeating steps 1 to 10. This experimental device and method can further improve the precision and accuracy of static penetration test interpretation and analysis, thereby effectively guiding engineering practice.

[0042] The calibration test device of the present invention can control the boundary stress conditions and saturation of the soil sample and obtain the deformation characteristics of the soil sample based on the wave velocity test.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A CPTU calibration test device with controllable boundaries and saturation, characterized in that: The invention comprises a calibration tank, a consolidation system, a penetration system, a saturation adjustment system and a control and data acquisition system. The calibration tank comprises an outer cylinder (9) whose axis extends in the vertical direction and an inner cylinder (10) coaxially arranged in the outer cylinder (9). The inner cylinder (10) is used to accommodate soil samples. The consolidation system comprises a consolidation plate (24) and a consolidation oil cylinder (4) for driving the consolidation plate (24) to move up and down. The consolidation plate (24) presses down the soil sample to consolidate the soil sample. A bending unit sensor (26) is provided on the lower side of the consolidation plate (24). The penetration system comprises a penetration probe (12) and a penetration oil cylinder (5) for driving the penetration probe (12) to move up and down. A penetration hole for the penetration probe (12) to pass through is provided in the middle of the consolidation plate (24). The saturation adjustment system comprises a permeable stone (13) located at the bottom of the inner cylinder (10), and a distribution system. A water pressure controller and an air pressure controller (2) are respectively connected to the upper end and the lower end of the calibration tank, the water pressure controller is used to inject degassed water into the calibration tank to control the water pressure in the calibration tank, and the air pressure controller (2) is used to inject inert gas into the calibration tank to control the air pressure in the calibration tank. The control and data acquisition system includes a computer (15), the computer (15) controls the expansion and contraction of the consolidation cylinder (4) and the penetration cylinder (5) through the hydraulic servo (14), and records and collects the cone tip resistance, side wall friction resistance, pore pressure, wave velocity data of the bending unit sensor (26) of the penetration probe (12) and the water pressure and air pressure data of the water pressure controller and the air pressure controller (2) through the data acquisition device (16). The calibration test device can control the boundary stress conditions and saturation of the soil sample and obtain the deformation characteristics of the soil sample based on the wave velocity test.

2. The CPTU calibration test device with controllable boundaries and saturation according to claim 1, characterized in that: The inner cylinder (10) is surrounded by a plurality of arc-shaped plates, and the plurality of arc-shaped plates are respectively located on the periphery of the consolidation plate (24). The outer side of each arc-shaped plate is connected to a horizontally extending push-pull rod (8), and the push-pull rod (8) can drive each arc-shaped plate to move back and forth along the radial direction of the inner cylinder (10) so that the arc-shaped plate is pressed against or loosened from the soil sample. The interior of the inner cylinder (10) is provided with a rubber membrane (11) for being sleeved on the periphery of the soil sample. When each arc-shaped plate is pressed against the soil sample, each arc-shaped plate forms a rigid boundary on the periphery of the soil sample. When each arc-shaped plate loosens from the soil sample, the rubber membrane (11) forms a flexible boundary on the periphery of the soil sample.

3. The CPTU calibration test device with controllable boundaries and saturation according to claim 2, characterized in that: A peripheral cavity (19) is provided between the inner side of the outer cylinder (9) and the outer side of the inner cylinder (10). A water injection and drainage port (18) is provided on the side wall of the outer cylinder (9). When each arc-shaped plate loosens the soil sample, the water injection and drainage port (18) is used for the inflow and outflow of liquid in the peripheral cavity (19).

4. The CPTU calibration test device with controllable boundaries and saturation according to claim 3, characterized in that: The lower end of the outer cylinder (9) is provided with a base (23), and the upper end is provided with an upper cover (22). A plurality of threaded tie rods (7) are connected between the base (23) and the upper cover (22) on the periphery of the outer cylinder (9) to seal and reinforce the calibration groove.

5. The CPTU calibration test device with controllable boundaries and saturation according to claim 4, characterized in that: The upper cover (22) and the consolidation plate (24) are provided with upper through holes (21) correspondingly. An upper switch valve is provided in the upper through hole (21). The upper through hole (21) is connected to the air pressure controller (2) through an air pipe. The air pressure controller (2) is filled with inert gas or incomplete inert gas. The base (23) is provided with a first water flow channel (17) and a second water flow channel (30). Two water pressure controllers are provided, namely a first water pressure controller (0) and a second water pressure controller (1). One end of the first water flow channel (17) is located below the permeable stone (13), and the other end is connected to the first water pressure controller (0). One end of the second water flow channel (30) is located between the outer cylinder (9) and the inner cylinder (10) and is connected to the outer cavity (19), and the other end is connected to the second water pressure controller (1).

6. The CPTU calibration test device with controllable boundaries and saturation according to claim 4, characterized in that: A gantry (6) is provided on the base (23) at the periphery of the calibration groove, the consolidation cylinder (4) and the penetration cylinder (5) are respectively installed on the top of the gantry (6), the lower end of the penetration cylinder (5) is connected to the penetration probe (12), the upper side of the consolidation plate (24) is connected to a connecting rod (28) extending in the up and down directions, the consolidation cylinder (4) is connected to the upper end of the connecting rod (28), and a lifting cylinder (3) is also installed on the top of the gantry (6), and the lower end of the lifting cylinder (3) is connected to the upper cover (22) to drive the upper cover (22) to rise and fall.

7. The CPTU calibration test device with controllable boundaries and saturation according to claim 6, characterized in that: When the consolidation plate (24) presses down the soil sample, a rod (27) extending in the up-down direction is inserted into the penetration hole, and the lower end of the rod (27) is flush with the lower side of the consolidation plate (24). The rod (27) is used to seal the penetration hole.

8. The CPTU calibration test device with controllable boundaries and saturation according to claim 7, characterized in that: The middle portion of the upper cover (22) is provided with perforations corresponding to the upper and lower portions of the penetration hole. After the consolidation plate (24) has finished pressing the soil sample, the rod (27) is removed from the consolidation plate (24). The penetration hole and the perforation are respectively connected to a first bushing (25) and a second bushing (29). The penetration probe (12) passes through the first bushing (25) and the second bushing (29) in sequence from top to bottom.

9. The CPTU calibration test device with controllable boundaries and saturation according to claim 8, characterized in that: The lower side of the upper cover (22) and the upper side of the base (23) are respectively provided with embedding grooves for plugging and matching with the upper and lower ends of the outer cylinder (9), and sealing rings (20) are respectively provided in the embedding grooves. The upper and lower ends of each arc-shaped plate are respectively provided with sealing gaskets for sealing and matching with the lower side of the upper cover (22) and the upper side of the base (23).

10. A CPTU calibration test method with controllable boundaries and saturation, characterized by: The CPTU calibration test device with controllable boundary and saturation as described in any one of claims 1 to 9 above comprises the following steps: loading a set amount of soil sample with a certain moisture content into the inner cylinder (10); consolidating the soil sample by pressing down the consolidation plate (24) through the consolidation cylinder (4); after the consolidation is completed, the penetration probe (12) passes through the consolidation plate (24) and penetrates into the soil sample; during the penetration process, the values of the cone tip resistance, side wall friction resistance, pore pressure and wave velocity test of the bending unit sensor (26) of the penetration probe (12) are recorded in real time by the data acquisition device (16) and displayed in a curve on the computer (15); the water pressure and air pressure in the calibration tank are adjusted by the air pressure controller (2) and the water pressure controller to control the suction of the soil sample, and then the target saturation is achieved by combining the water retention curve of the soil sample under the same conditions.

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