Embedded three-dimensional soil pressure testing device and testing method thereof

Abstract

The invention provides an embedded three-dimensional soil pressure testing device and a testing method thereof, and belongs to the technical field of geotechnical engineering test.The embedded three-dimensional soil pressure testing device is characterized in that an open hole is formed in the center of a pressed top panel so as to facilitate drainage after testing; the pressed edge panel is in contact with a lateral test soil body to transmit stress; a power supply element and a storage element are arranged in the inner cylinder, and stable power supply exists between the inner cylinder and each thin film pressure sensor; the bottom plate and the inner cylinder are connected to form a stable device inner frame, and meanwhile a plug hole and a plug head are arranged in the center and used for connecting the device with the outside. The water-permeable flexible films are arranged among the pressure-bearing panels, and water in the soil body can freely enter the cavity through the water-permeable flexible films. The real three-dimensional stress state of the soil body can be mastered in real time by being buried in a specific position of the soil body, and the influence of pore water pressure can be counteracted when the device is applied to the saturated soil body.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing technology, specifically to an embedded three-dimensional earth pressure testing device and its testing method. Background Technology

[0002] Currently available traditional earth pressure testing devices are generally low-precision vibrating wire earth pressure cells (SPCs) or thin-film pressure sensors (FSRs) that require high soil flatness and specific testing environments. Most earth pressure testing devices can only measure earth pressure in a single direction, making it difficult to analyze the true three-dimensional stress state within the soil. Furthermore, the process of embedding these devices in the soil requires connecting numerous wires, which can affect the stress distribution within the soil, causing stress concentration or soil arching effects, thus interfering with the measurement results. In addition, measuring the true earth pressure in water-rich soils has always been an engineering challenge; additional pore water pressure sensors have poor synergy with traditional earth pressure testing devices, and different measurement point locations can also introduce errors into the test results. Designing an earth pressure testing device capable of measuring the true three-dimensional stress state within soil is of great significance for ensuring the safety of structures, exploring foundation strength theory, and revealing the stress diffusion mechanism within soil.

[0003] The shortcomings of the existing earth pressure testing devices are as follows: vibrating wire earth pressure cells (SPCs) have lower accuracy and a fixed range compared to electronic circuits, while thin-film pressure sensors (FSRs) have higher accuracy but are subject to stringent testing conditions and are prone to uneven compression and deformation when in contact with the soil, thus affecting the test results; due to the presence of connecting wires, the original stress state inside the soil is affected. The smaller the earth pressure cell and the higher the required accuracy of the measurement data, the greater the influence of the connecting wires. For highly sensitive tests such as frozen soil, the presence of connecting wires can also affect the segregation state of ice in the soil. Therefore, it is impossible to restore the actual phase transition state; most earth pressure testing devices can only measure pressure in a single direction, and cannot more accurately monitor the three-dimensional stress state of soil elements in the foundation. Some earth pressure testing devices represented by polyhedra have a large amount of measurement data, and the method of calculating earth pressure through spatial matrices is too cumbersome in subsequent data processing; traditional earth pressure testing devices are only suitable for dry testing environments, and there is still a lack of means and equipment for measuring earth pressure in water-rich soils. Furthermore, pore water pressure can also interfere with the true stress between soil particles, which is difficult to eliminate in actual measurement. Summary of the Invention

[0004] The purpose of this invention is to provide an embedded three-dimensional earth pressure testing device and its testing method, which can measure the real three-dimensional stress state of the soil in real time by embedding it at a specific location in the soil. When applied to saturated soil, it can offset the influence of pore water pressure, thereby solving at least one of the technical problems existing in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides an embedded three-dimensional earth pressure testing device, comprising: a pressure-bearing top panel, a pressure-bearing side panel, a membrane pressure sensor, an inner cylinder, a bottom plate, and a permeable flexible membrane;

[0007] The inner cylinder is detachably connected above the base plate; the top of the inner cylinder is connected to the pressure-bearing top panel via a top force transmission rod; the pressure-bearing top panel is a disc-shaped rigid component that contacts the top test soil to transmit stress; multiple stabilizing rods are provided around the top force transmission rod, connecting the pressure-bearing top panel and the inner cylinder; multiple pressure-bearing side panels are connected to the sides of the inner cylinder via multiple lateral force transmission rods; the pressure-bearing side panels are arc-shaped rigid components that contact the lateral test soil to transmit stress; multiple stabilizing rods are provided around the lateral force transmission rods, connecting the pressure-bearing side panels and the inner cylinder. The inner cylinder has stabilizing rods between its side walls; thin-film pressure sensors are installed inside both the top force transmission rod and the lateral force transmission rod; the inner cylinder contains power supply and storage elements, and is stably powered to each thin-film pressure sensor; a permeable flexible membrane is installed between adjacent pressure-bearing side panels and between the pressure-bearing side panels and the pressure-bearing top panel, forming a cavity. Water in the test soil can freely enter the cavity through this permeable flexible membrane, thereby achieving a balance between the water pressure in the cavity and the test soil; the values ​​of the thin-film pressure sensors are used to calculate the stress in each direction of the soil using corresponding differential formulas.

[0008] Furthermore, four stabilizing rods are evenly distributed around each of the thin-film pressure sensors; each stabilizing rod includes a sleeve rod with one end connected to the inner cylinder, the sleeve rod having an axial groove, and an end rod that can slide along the axial groove.

[0009] Furthermore, the diameter of the pressure-bearing top panel is smaller than the outer contour diameter formed by the multiple pressure-bearing side panels, and an opening is provided in its center. During testing, the opening is closed to form a water-permeable sealed cavity, and after the test, the opening can be used for drainage.

[0010] Furthermore, there are four pressure-bearing edge panels, and the angle corresponding to the arc surface of the pressure-bearing edge panels is less than 90° to ensure that the pressure-bearing edge panels do not affect each other.

[0011] Furthermore, the inner cylinder connected to the thin-film pressure sensor is cylindrical, and a connection port is provided on the outer side of the inner cylinder to connect with the thin-film pressure sensors on the top and side.

[0012] Furthermore, the bottom plate is provided with a threaded seat with external threads in the middle, and the bottom of the inner cylinder is provided with a threaded blind groove with internal threads; the inner cylinder and the bottom plate are detachably connected by the cooperation of the threaded seat and the threaded blind groove.

[0013] Furthermore, the bottom of the base plate is provided with a through hole to facilitate setting or reading the internal parameters of the signal collection and transmission module through the interface before and after testing. At the same time, the base plate is provided with a plug that matches the bottom hole to prevent soil and water from entering the inner cylinder and damaging the circuit components during the test.

[0014] Furthermore, the permeable flexible membrane, together with the pressure-bearing top panel and the pressure-bearing side panel, constitutes the outer contour of the soil pressure testing device. During the test, water molecules in the soil can freely pass through the permeable flexible membrane into the device cavity, causing water pressure to be generated inside the device cavity. When the water pressure inside the cavity is higher than that outside, water molecules can also permeate out of the cavity, ensuring that the inside and outside reach a balanced state, thereby offsetting the influence of water pressure in the soil on the effective stress of the soil.

[0015] Furthermore, the corrected calculation method for earth pressure converted from compressed panels includes:

[0016] The axial stress is obtained by differentiating the force on the pressure-bearing top panel measured by the pressure sensor from the area of ​​the pressure-bearing top panel. The calculation formula is as follows:

[0017] ;

[0018] In the formula, F v σ1 represents the reading of the thin-film pressure sensor on the pressure-bearing top panel; A represents the area of ​​the pressure-bearing top panel; σ1 represents the uniformly distributed stress borne by the pressure-bearing top panel.

[0019] The circumferential stress is obtained by differentiating the force on the pressure-bearing edge panel measured by the pressure sensor from the area of ​​the pressure-bearing edge panel and the corresponding angle. The calculation formula is as follows:

[0020] ;

[0021] In the formula, F s σ3 is the reading of the pressure sensor connected to the pressure-bearing edge panel; h is the height of the pressure-bearing edge panel; σ3 is the uniformly distributed stress borne by the pressure-bearing edge panel; x is the angle from a point on the pressure-bearing edge panel to the center of the arc surface.

[0022] Secondly, the present invention provides a testing method using the embedded three-dimensional earth pressure testing device as described in the first aspect. The method involves setting the test range and data recording method by connecting a specific device to the base plate interface; then embedding the testing device in a specific location in the soil according to the test plan; then performing loading and freeze-thaw cycles to achieve the preset working conditions; finally, removing the testing device after the test is completed; and finally using a specific device to connect to the base plate interface to obtain the test data. Other group tests can be reset subsequently.

[0023] The beneficial effects of this invention are: it can determine the three-dimensional stress state of the soil at the buried location, can be used to eliminate the influence of pore water pressure in saturated soil, can accurately determine the effective stress of the soil, and at the same time, the use of specific reading equipment avoids the influence of the connecting wire being buried in the soil during the test.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a top view schematic diagram of the embedded three-dimensional earth pressure testing device according to an embodiment of the present invention.

[0027] Figure 2 This is a side view of the embedded three-dimensional earth pressure testing device according to an embodiment of the present invention.

[0028] Figure 3 This is a top-view perspective view of the embedded three-dimensional earth pressure testing device according to an embodiment of the present invention.

[0029] Figure 4 This is a side perspective view of the embedded three-dimensional earth pressure testing device according to an embodiment of the present invention.

[0030] Figure 5 This is a schematic diagram of the pressure-bearing panel of the embedded three-dimensional earth pressure testing device according to an embodiment of the present invention.

[0031] Figure 6 This is a schematic diagram of the inner cylinder and bottom plate of the embedded three-dimensional earth pressure testing device according to an embodiment of the present invention.

[0032] The components are: 1. Top pressure panel; 2. Side pressure panel; 3. Thin-film pressure sensor; 4. Inner cylinder; 5. Base plate; 6. Water-permeable flexible membrane; 7. Top force transmission rod; 8. Stabilizing rod; 9. Lateral force transmission rod; 41. Sleeve rod; 42. End rod; 44. Force transmission rod connection port; 11. External thread; 12. Threaded seat; 13. Internal thread; 14. Threaded blind groove; 15. Plug; 21. Arc-shaped panel. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0034] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention is described.

[0035] It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as here.

[0036] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0037] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0038] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0039] In the description of this specification, the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this technology and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this technology.

[0040] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of these terms in this art according to the specific circumstances.

[0041] To facilitate understanding of the present invention, the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0042] Those skilled in the art should understand that the accompanying drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0043] like Figures 1 to 6 As shown in one specific embodiment, an embedded three-dimensional earth pressure testing device and its testing method are provided, and the relevant earth pressure testing principles and usage methods are introduced.

[0044] An embedded three-dimensional earth pressure testing device includes: a pressure-bearing top panel 1, pressure-bearing side panels 2, a membrane pressure sensor 3, an inner cylinder 4, a base plate 5, and a permeable flexible membrane 6. The inner cylinder 4 is detachably connected above the base plate 5. The top of the inner cylinder 4 is connected to the pressure-bearing top panel 1 via a top force transmission rod 7. The pressure-bearing top panel 1 is a disc-shaped rigid component that contacts the top test soil to transmit stress. Multiple stabilizing rods 8 are provided around the top force transmission rod 7, connecting the pressure-bearing top panel 1 and the inner cylinder 4. Multiple pressure-bearing side panels 2 are connected to the sides of the inner cylinder 4 via multiple lateral force transmission rods 9. The pressure-bearing side panels 2 are arc-shaped rigid components that contact the lateral test soil to transmit stress. Multiple stabilizing rods 8 are provided around the lateral force transmission rod 9, connecting the side walls of the pressure-bearing side panel 2 and the inner cylinder 4; thin-film pressure sensors 3 are provided inside both the top force transmission rod 7 and the lateral force transmission rod 9; the inner cylinder 4 has power supply and storage elements inside, and is stably powered to each thin-film pressure sensor 3; the permeable flexible membrane 6 is set between adjacent pressure-bearing side panels 2 and between the pressure-bearing side panel 2 and the pressure-bearing top panel 1, forming a cavity, through which water in the test soil can freely enter the cavity, thereby achieving a balance between the water pressure in the cavity and the test soil; wherein, the values ​​of the thin-film pressure sensors 3 are used to calculate the stress in each direction of the soil using corresponding differential formulas.

[0045] In one specific embodiment, four stabilizing rods 8 are evenly distributed around each of the thin-film pressure sensors 3. Each stabilizing rod 8 includes a sleeve rod 41 connected at one end to the inner cylinder 4, with an axial groove inside the sleeve rod 41 and an end rod 42 that can slide along the axial groove. The diameter of the pressure-bearing top panel 1 is smaller than the outer contour diameter formed by the multiple pressure-bearing side panels 2, and it has an opening at its center. During testing, it closes to form a water-permeable sealed cavity, and after testing, it can be opened for drainage. There are four pressure-bearing side panels 2, and the angle corresponding to the arc surface of the pressure-bearing side panels 2 is less than 90° to ensure that the pressure-bearing side panels do not affect each other. The inner cylinder connected to the thin-film pressure sensor 3 is cylindrical, and the outer side of the inner cylinder 4 has a connection port for connecting to the top and side thin-film pressure sensors 3. The bottom plate 5 is provided with a threaded seat 12 with external threads 11 in the middle, and the bottom of the inner cylinder is provided with a threaded blind groove 14 with internal threads 13; the inner cylinder 4 and the bottom plate 5 are detachably connected by the cooperation of the threaded seat 12 and the threaded blind groove 14.

[0046] In one specific embodiment, the bottom of the base plate 5 is provided with a through hole to facilitate setting or reading the internal parameters of the signal collection and transmission module through the interface before and after the test. At the same time, the base plate is provided with a plug 15 that matches the bottom hole to prevent soil and water from entering the inner cylinder and damaging the circuit components during the test.

[0047] The permeable flexible membrane 6, together with the pressure-bearing top panel and the pressure-bearing side panel, constitutes the outer contour of the soil pressure testing device. During the test, water molecules in the soil can freely enter the device cavity through the permeable flexible membrane, causing water pressure to be generated inside the device cavity. When the water pressure inside the cavity is higher than that outside, water molecules can also permeate out of the cavity, ensuring that the inside and outside reach a balanced state, thereby offsetting the influence of water pressure in the soil on the effective stress of the soil.

[0048] In this embodiment, the pressure-bearing panel includes a top pressure-bearing panel and a side pressure-bearing panel. The top pressure-bearing panel is disc-shaped, and the side pressure-bearing panel is arc-shaped. A permeable flexible membrane is disposed between the pressure-bearing panels to ensure free movement of the panels when the device is sealed. Simultaneously, when used for saturated soil testing, water in the soil can freely seep into the earth pressure chamber, eliminating the influence of pore water pressure. The pressure sensor is located between the pressure-bearing panel and the inner cylinder and generates test values ​​based on the applied pressure. The inner cylinder is non-deformable and contains power supply and storage components, maintaining a stable power supply to each pressure sensor. Before the test, the test range and recording method can be adjusted by connecting to relevant instruments. During the test, the test data can be recorded according to preset parameters. After the test, the test data can be exported by connecting to relevant instruments. The base plate is fixed to the inner cylinder to form the internal frame of the device, and an interface is provided at the center of its bottom for replenishing power and connecting to external instruments.

[0049] In one embodiment, the earth pressure testing device is a short cylinder. The top surface of the cylinder is a disc-shaped pressure-bearing top panel with a diameter slightly smaller than the diameter of the outer contour top surface of the earth pressure testing device, providing space for the pressure-bearing top panel to move under pressure. The side surface of the cylinder is a pressure-bearing side panel, which is an arc plate with an outer contour top surface diameter of the earth pressure testing device. The angle corresponding to the arc surface is less than 90°, providing space for the pressure-bearing side panel to generate micro-displacement under pressure. All pressure-bearing panels are rigid and do not deform themselves.

[0050] In one embodiment, a connecting rod (force transmission rod) is provided between the pressure-bearing panel and the inner cylinder. The connecting rod is a rigid rod so that the pressure on the outside of the pressure-bearing panel is transmitted through the connecting rod. The end of the connecting rod is connected to a thin-film pressure sensor, and the other end of the pressure sensor is inserted into the inner cylinder. The pressure sensor has an adjustable range.

[0051] In one embodiment, the permeable flexible membrane and the pressure-bearing panel together form the outer contour of the soil pressure testing device. During the soil pressure test, water molecules in the soil can freely pass through the permeable flexible membrane into the device cavity, causing water pressure to be generated inside the device cavity. When the water pressure inside the cavity is higher than that outside, water molecules can also permeate out of the cavity, thereby offsetting the effect of water pressure in the soil on the effective stress of the soil.

[0052] In one embodiment, the inner cylinder to which the pressure sensor is connected is cylindrical, and the outer side of the inner cylinder is provided with a connection port to connect with the pressure sensors on the top and sides. The bottom of the inner cylinder is provided with threads for a secure connection with the base plate of the device.

[0053] In one embodiment, a certain space is provided in the middle of the inner cylinder for placing a signal collection and transmission module, including a circuit board, a memory, and related programs.

[0054] In one embodiment, the base plate is disc-shaped with a threaded opening inside for connecting with the inner cylinder to form the internal frame of the earth pressure testing device. The bottom of the base plate has a through hole to facilitate setting or reading the internal parameters of the signal collection and transmission module through the interface before and after the test. At the same time, the base plate is equipped with a plug that matches the bottom hole to prevent soil and water from entering the inner cylinder and damaging the circuit components during the test.

[0055] In one embodiment, the earth pressure testing device has no external connection cable, and the setting of test parameters and reading of test results are achieved by using a specific device to connect to the base plate interface.

[0056] In this embodiment, a testing method for an embedded three-dimensional earth pressure testing device is also provided, the method of use including:

[0057] The axial stress is obtained by differentiating the force on the pressure-bearing top panel measured by the pressure sensor from the area of ​​the pressure-bearing top panel. The calculation formula is as follows:

[0058] ;

[0059] In the formula, F v σ1 is the reading of the pressure sensor connected to the pressure-bearing top panel; A is the area of ​​the pressure-bearing top panel; σ1 is the uniformly distributed stress borne by the pressure-bearing top panel.

[0060] The circumferential stress is obtained by differentiating the force on the pressure-bearing edge panel measured by the pressure sensor from the area of ​​the pressure-bearing edge panel and the corresponding angle. The calculation formula is as follows:

[0061] ;

[0062] In the formula, F s σ3 is the reading of the pressure sensor connected to the pressure-bearing edge panel; h is the height of the pressure-bearing edge panel; σ3 is the uniformly distributed stress borne by the pressure-bearing edge panel; x is the angle from a point on the pressure-bearing edge panel to the center of the arc surface.

[0063] In the saturated soil test, the cavity of the test device is filled with water equal to the external water pressure, and the measured soil pressure is the soil skeleton stress excluding the influence of pore water pressure.

[0064] In one embodiment, the method of using the earth pressure testing device is as follows: first, the test range and data recording method are set by connecting the base plate interface through a specific device; then, the earth pressure testing device is buried in a specific location in the soil according to the test plan; then, loading, freeze-thaw cycles, etc. are performed to achieve the preset working conditions; the earth pressure testing device is taken out until the test is completed; finally, the test data is obtained by connecting the base plate interface with a specific device; and other group tests can be reset subsequently.

[0065] The above-mentioned embedded three-dimensional earth pressure testing device and its testing method can determine the three-dimensional stress state of the soil at the buried location, can be used to eliminate the influence of pore water pressure in saturated soil, can accurately determine the effective stress of the soil, and at the same time, the use of specific reading equipment avoids the influence of the connecting wire in the soil during the test.

[0066] In one embodiment, see Figure 1 As shown, the earth pressure testing device includes a pressure-bearing top panel 1, a pressure-bearing side panel 2, a membrane pressure sensor 3, a stabilizing rod 8, a base plate 5, an inner cylinder 4, and a permeable flexible membrane 6. The pressure-bearing top panel 1 is equipped with a top force transmission rod, optionally located in the middle of the inner side of the pressure-bearing top panel 1. This allows stress to be transmitted through the pressure-bearing top panel 1 to the top force transmission rod. The top force transmission rod is rigid to ensure effective force transmission. The other end of the top force transmission rod is connected to the membrane pressure sensor 3, which measures the pressure value and transmits it via a circuit to a signal collection and transmission module in the inner cylinder 4.

[0067] The pressure-bearing side panel 2 is evenly arranged around the outer perimeter of the inner cylinder. The thin-film pressure sensor 3 is located between the top force transmission rod 12 and the side force transmission rod. Its area is the diameter of the force transmission rod, and it can test the axial force of the force transmission rod. It is also protected from the influence of forces in other directions by the surrounding stabilizing rods.

[0068] The base plate is located at the bottom of the earth pressure testing device, with a hole in the middle that can be sealed by a plug. The upper part of the base plate has a raised thread (a threaded seat with external threads), which allows the base plate and the inner cylinder to be connected and disassembled by twisting. The base plate is rigid to provide a stable foundation for the earth pressure testing device. Subsequent input of test programs and reading of test data can be achieved through the interface inside the plug.

[0069] The inner cylinder is a column located at the center of the earth pressure testing device. Its bottom end is equipped with a threaded bayonet (a blind groove with internal threads) that corresponds to the threaded seat on the base plate. The top and sides of the inner cylinder are equipped with force transmission rod connection ports 44, which combine with the pressure-bearing top panel 1 and the pressure-bearing side panel 2. The inner cylinder houses a signal collection and transmission module and a power supply system to ensure the normal operation of the diaphragm pressure sensor 3.

[0070] A permeable flexible membrane 6 is located between the pressure-bearing panels. The membrane is soft and will not cause any pulling on the pressure-bearing top panel 1 or the pressure-bearing side panel 2 due to its own deformation. The permeable flexible membrane is made of a permeable material, allowing water molecules to pass freely through it, while also isolating soil particles and other impurities from the soil. This means the permeable flexible membrane can be combined with the pressure-bearing top panel 1 and the pressure-bearing side panel 2 to form a permeable, closed system that ensures equal water pressure inside and outside the device. In another embodiment, for measuring dry soil, the permeable flexible membrane can be replaced with an impermeable flexible material, thereby increasing the durability and applicability of the soil pressure testing device.

[0071] In this embodiment, the testing method using the above-described embedded three-dimensional earth pressure testing device specifically includes:

[0072] S1: Remove the plug from the base plate, connect the earth pressure testing device to the interface using a computer with the relevant program, zero the calibration and set the measurement range and measurement interval for this measurement.

[0073] S2: After the setup is complete, insert the plug into the bottom plate and ensure it is tightly inserted. Then, bury the earth pressure testing device in the soil at the preset measuring point position.

[0074] S3: Conduct the experiment.

[0075] S4: After the test, remove the earth pressure testing device, unplug the plug on the base plate, and use a computer with the relevant program to connect to the interface of the earth pressure testing device to read the test data.

[0076] In practical applications, the earth pressure testing device needs to be zeroed and calibrated before each test to proceed with the next set of tests.

[0077] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or variations that can be made by those skilled in the art without creative effort should be included within the scope of protection of the present invention.

Claims

1. An embedded three-dimensional earth pressure testing device, characterized in that, include: The pressure-bearing top panel (1), the pressure-bearing side panel (2), the membrane pressure sensor (3), the inner cylinder (4), the bottom plate (5), and the water-permeable flexible membrane (6); The inner cylinder (4) is detachably connected above the bottom plate (5); the top of the inner cylinder (4) is connected to the pressure-bearing top panel (1) through the top force transmission rod (7); the pressure-bearing top panel (1) is a disc-shaped rigid component that contacts the top test soil to transmit stress. A plurality of stabilizing rods (8) are provided around the top force transmission rod (7) and connected between the pressure-bearing top panel (1) and the inner cylinder (4); the side of the inner cylinder (4) is connected to a plurality of pressure-bearing side panels (2) by a plurality of lateral force transmission rods (9); the pressure-bearing side panels (2) are arc-shaped rigid members that contact the lateral test soil to transmit stress; Multiple stabilizing rods (8) are provided around the lateral force transmission rod (9) and connected between the side walls of the pressure-bearing side panel (2) and the inner cylinder (4); a thin film pressure sensor (3) is provided inside the top force transmission rod (7) and the lateral force transmission rod (9); the inner cylinder (4) has a power supply element and a storage element inside, and is stably powered by each thin film pressure sensor (3); the permeable flexible membrane (6) is set between adjacent pressure-bearing side panels (2) and between the pressure-bearing side panel (2) and the pressure-bearing top panel (1) to form a cavity, and water in the test soil can freely enter the cavity through this permeable flexible membrane (6), thereby achieving a balance between the water pressure in the cavity and the test soil; wherein, the value of the thin film pressure sensor (3) is used to back-calculate the stress in each direction of the soil through the corresponding differential formula.

2. The embedded three-dimensional earth pressure testing device according to claim 1, characterized in that, Four stabilizing rods (8) are evenly distributed around each of the thin-film pressure sensors (3); each stabilizing rod (8) includes a sleeve rod (41) with one end connected to the inner cylinder (4), the sleeve rod (41) is provided with an axial groove, and an end rod (42) that can slide along the axial groove is provided in the axial groove.

3. The embedded three-dimensional earth pressure testing device according to claim 1, characterized in that, The diameter of the pressure-bearing top panel (1) is smaller than the outer contour diameter formed by the multiple pressure-bearing side panels (2). It has an opening in its center, which closes during testing to form a water-permeable sealed cavity. After the test, it can be opened for drainage.

4. The embedded three-dimensional earth pressure testing device according to claim 3, characterized in that, There are 4 pressure-bearing edge panels (2), and the angle corresponding to the arc surface of the pressure-bearing edge panels (2) is less than 90° to ensure that the pressure-bearing edge panels do not affect each other.

5. The embedded three-dimensional earth pressure testing device according to claim 1, characterized in that, The inner cylinder connected to the thin film pressure sensor (3) is cylindrical, and the outer side of the inner cylinder (4) is provided with a connection port to connect with the thin film pressure sensor (3) on the top and side.

6. The embedded three-dimensional earth pressure testing device according to claim 1, characterized in that, The bottom plate (5) is provided with a threaded seat (12) with external threads (11) in the middle, and the bottom of the inner cylinder is provided with a threaded blind groove (14) with internal threads (13); the inner cylinder (4) and the bottom plate (5) are detachably connected by the cooperation of the threaded seat (12) and the threaded blind groove (14).

7. The embedded three-dimensional earth pressure testing device according to claim 6, characterized in that, The bottom of the base plate (5) is provided with a through hole so that the internal parameters of the signal collection and transmission module can be set or read through the interface before and after the test. At the same time, the base plate is provided with a plug (15) that matches the bottom hole to prevent soil and water from entering the inner cylinder and damaging the circuit components during the test.

8. The embedded three-dimensional earth pressure testing device according to claim 7, characterized in that, The permeable flexible membrane (6), together with the pressure-bearing top panel and the pressure-bearing side panel, constitutes the outer contour of the soil pressure testing device. During the test, water molecules in the soil can freely enter the device cavity through the permeable flexible membrane, causing water pressure to be generated in the device cavity. When the water pressure inside the cavity is higher than that outside, water molecules can also permeate out of the cavity, ensuring that the inside and outside reach a balanced state, thereby offsetting the influence of water pressure in the soil on the effective stress of the soil.

9. The embedded three-dimensional earth pressure testing device according to claim 1, characterized in that, Corrected calculation methods for earth pressure conversion using compressed panels include: The axial stress is obtained by differentiating the force on the pressure-bearing top panel measured by the pressure sensor from the area of ​​the pressure-bearing top panel. The calculation formula is as follows: ； In the formula, F v σ1 represents the reading of the thin-film pressure sensor on the pressure-bearing top panel; A represents the area of ​​the pressure-bearing top panel; σ1 represents the uniformly distributed stress borne by the pressure-bearing top panel. The circumferential stress is obtained by differentiating the force on the pressure-bearing edge panel measured by the pressure sensor from the area of ​​the pressure-bearing edge panel and the corresponding angle. The calculation formula is as follows: ； In the formula, F s σ3 is the reading of the pressure sensor connected to the pressure-bearing edge panel; h is the height of the pressure-bearing edge panel; σ3 is the uniformly distributed stress borne by the pressure-bearing edge panel; x is the angle from a point on the pressure-bearing edge panel to the center of the arc surface.

10. A testing method using the embedded three-dimensional earth pressure testing device as described in any one of claims 1-9, characterized in that, The test range and data recording method are set by connecting the base plate interface with a specific device; the test device is then buried in a specific location in the soil according to the test plan; loading and freeze-thaw cycles are then performed to achieve the preset working conditions; the test device is then removed after the test is completed; finally, the test data is obtained by connecting the base plate interface with a specific device; subsequent tests of other groups can be reset.

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