Transverse isotropic soil sample making device and method

Abstract

The application provides a transversely isotropic soil sample manufacturing device and a manufacturing method thereof, and belongs to the technical field of geotechnical engineering. The application solves the problem that there is no related design of the transversely isotropic soil sample manufacturing device in the prior art. The device comprises an outer frame, a sample binding mechanism for restricting the compression range of the soil sample is installed on the outer frame, and a compression mechanism for compacting the soil sample in the sample binding mechanism is installed on the outer frame and located above the sample binding mechanism. By setting the outer frame and the sample binding mechanism and the compression mechanism on the outer frame, the transversely isotropic soil sample with different thicknesses, different inclination angles and different density combinations can be manufactured. The manufactured soil sample can be used for satisfying the soil triaxial test and the permeability test under different working conditions.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, specifically to a transversely isotropic soil sample preparation device and its preparation method. Background Technology

[0002] Under the influence of depositional conditions such as gravity, water flow, and aeolian deposition, soil particles will exhibit directional alignment in a certain plane, forming layered or banded structures. This structural characteristic results in the soil having the same mechanical properties in that plane, but significantly different mechanical properties in the vertical plane, exhibiting transverse isotropy. Ignoring the transverse isotropy of soil can lead to experimental results deviating from reality, consequently causing engineering designs to be overly risky or conservative. For example, in pile foundation engineering, the difference in resistance between the vertical and horizontal directions of the soil along the pile affects the pile foundation's bearing capacity; in underground engineering, during tunnel excavation, the anisotropy of the surrounding rock can lead to asymmetric deformation and failure; and in slope stability, potential sliding surfaces in sedimentary strata often develop along anisotropic weak surfaces.

[0003] Currently, in-situ tests that can effectively reflect the natural transverse anisotropy of soil (such as pressuremeter tests and vane shear tests) are limited by site conditions, cost, and testing direction, making it difficult to systematically quantify anisotropic parameters. To gain a more comprehensive understanding of the characteristics of soil transverse anisotropy, laboratory experiments are necessary. Modern soil and rock constitutive models require calibration of experimental data. Preparing transversely isotropic soil samples provides controllable experimental conditions, which is crucial for verifying the predictive ability of constitutive theories for direction-dependent responses and determining anisotropic parameters. Without such soil samples, model validation will be limited to the isotropic assumption, reducing its applicability in complex geological formations. Currently, there is no design for a transversely isotropic soil sample preparation device. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a transversely isotropic soil sample preparation device and method. By setting an outer frame and a sample binding mechanism and a compression mechanism on the outer frame, transversely isotropic soil samples with different thicknesses, inclination angles, and density combinations can be prepared. The prepared soil samples can be used to meet the requirements of triaxial and permeability tests of soil under different working conditions.

[0005] The technical solution adopted in this invention is as follows: A transversely isotropic soil sample preparation device includes an outer frame, on which a sample-binding mechanism for constraining the compression range of the soil sample is installed, and on which a compression mechanism located above the sample-binding mechanism is installed for compacting the soil sample in the sample-binding mechanism is installed.

[0006] Preferably, the outer frame includes several vertically arranged support rods, on which a bottom plate and a top plate are mounted.

[0007] Preferably, the support rod is threaded with several first limiting nuts, which abut against the upper and lower surfaces of the bottom plate and the top plate.

[0008] Preferably, the sample-binding mechanism includes two side plates that are vertically fixed to the base plate and are arranged in parallel and spaced apart. A horizontal moving plate and a vertical moving plate are movably arranged between the two side plates. A reaction seat is fixedly arranged on the base plate. A first hydraulic rod for pushing the horizontal moving plate to move between the two side plates is installed on the reaction seat. A through groove for the vertical moving plate to move is opened on the base plate.

[0009] Preferably, several connecting rods are movably connected between the two side plates, and the two ends of the connecting rods are threaded with a second limiting nut that abuts against the outside of the side plate.

[0010] Preferably, a baffle that slides in contact with the vertical moving plate is fixedly connected to the inner side of the side plate.

[0011] Preferably, the through groove is provided with an anti-slip pad.

[0012] Preferably, the compression mechanism includes a second hydraulic rod, the lower end of which is connected to a pressure plate, and the upper end of which is connected to a vertically arranged guide rod. A strip-shaped hole that cooperates with the guide rod is provided on the top plate along the extension and retraction direction of the first hydraulic rod.

[0013] Preferably, the guide rod is threaded with a third limiting nut that abuts against the upper surface of the top plate.

[0014] A method for preparing transversely isotropic soil samples, using the aforementioned transversely isotropic soil sample preparation device, the method comprising: S1. Prepare a single-layer transversely isotropic soil sample. Determine the soil sample density ρ and the thickness h of the single-layer soil sample based on relevant data. Weigh the required soil sample mass m. The formula for calculating the soil sample mass m is: m=ρhab Where a is the distance between the inner walls of the two side plates; b is the distance between the inner walls of the horizontally moving plate and the vertically moving plate at the initial position; Spread the soil sample evenly in the sample bundle mechanism, install the pressure plate and the second hydraulic rod, and slowly apply pressure. After pressing the soil sample to a thickness of h, stop applying pressure and stabilize the pressure for 30 minutes to allow the soil sample to set. Record the pressure reading p. S2. Prepare soil samples of different densities and thicknesses according to step S1 to meet the experimental requirements. S3. According to the required tilt angle α, control the first hydraulic rod to adjust the position of the horizontal moving plate so that the distance between the inner wall of the horizontal moving plate and the inner wall of the vertical moving plate after the adjustment is b'=cos(α)∙b, add soil sample and compact to the target density; S4. After retracting the pressure plate, move the vertical moving plate to move it down in the vertical direction by h', where h'==sin(α)∙b'. Use a tool to cut a slope with an angle of α. S5. Move the vertical moving plate to the initial height before the test, and put the prepared soil samples in the order required by the test. S6. After the last layer of soil sample is placed, fill the upper slope with loose soil sample, then compact the sample with the minimum compaction pressure in steps S1 and S2, and hold the pressure for at least 30 minutes.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: By setting an outer frame and installing a sample-binding mechanism and a compression mechanism on the outer frame, it is possible to produce transversely isotropic soil samples with different thicknesses, inclination angles, and density combinations. The produced soil samples can be used to meet the requirements of triaxial and permeability tests of soil under different working conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a front-view stereoscopic structural diagram provided for an embodiment of the present invention; Figure 2 This is a rear-view stereoscopic structural diagram provided for an embodiment of the present invention; Figure 3 This is a three-dimensional structural diagram from another rear-view perspective provided in an embodiment of the present invention; Figure 4 This is a side view cross-sectional structural schematic diagram provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the sample preparation process provided in an embodiment of the present invention.

[0018] Reference numerals: 1-Base plate; 2-First limiting nut; 3-Connecting rod; 4-Side plate; 5-Support rod; 6-Second limiting nut; 7-Top plate; 8-Scale; 9-Guide rod; 10-Third limiting nut; 11-Strip hole; 12-Second hydraulic rod; 13-Pressure plate; 14-Vertical moving plate; 15-Baffle; 16-Reaction seat; 17-First hydraulic rod; 18-Horizontal moving plate; 19-Through groove; 20-Anti-slip pad. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] In the description of this invention, it should be noted that if terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, they are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0022] The following is combined Figures 1-5 The present invention will be described in detail below.

[0023] Example: A transversely isotropic soil sample preparation device includes an outer frame, a sample binding mechanism for constraining the compression range of the soil sample is installed on the outer frame, and a compression mechanism located above the sample binding mechanism for compacting the soil sample in the sample binding mechanism is installed on the outer frame.

[0024] By setting an outer frame and installing a sample-binding mechanism and a compression mechanism on the outer frame, it is possible to produce transversely isotropic soil samples with different thicknesses, inclination angles, and density combinations. The produced soil samples can be used to meet the requirements of triaxial and permeability tests of soil under different working conditions.

[0025] The outer frame includes several vertically arranged support rods 5, on which a base plate 1 and a top plate 7 are mounted. The base plate 1 and the top plate 7 are installed at intervals on the support rods 5 to facilitate the installation of the beam-binding mechanism and the compression mechanism.

[0026] Several first limiting nuts 2 are threaded onto the support rod 5. The first limiting nuts 2 abut against the upper and lower surfaces of the bottom plate 1 and the top plate 7. The first limiting nuts 2 limit the bottom plate 1 and the top plate 7. When it is necessary to disassemble or assemble the bottom plate 1 and the top plate 7 or adjust their positions, simply tighten the first limiting nuts 2. The operation is simple.

[0027] The sample-binding mechanism includes two side plates 4 that are vertically fixed on the base plate 1 and are arranged in parallel and spaced apart. A horizontal moving plate 18 and a vertical moving plate 14 are movably arranged between the two side plates 4. A reaction seat 16 is fixedly arranged on the base plate 1. A first hydraulic rod 17 for pushing the horizontal moving plate 18 to move between the two side plates 4 is installed on the reaction seat 16. A through groove 19 for the vertical moving plate 14 to move is opened on the base plate 1.

[0028] The first hydraulic rod 17 is set at the center of the horizontal moving plate 18 through the reaction seat 16 to ensure that a balanced thrust is applied. The first hydraulic rod 17 can drive the horizontal moving plate 18 to move and adjust its position as needed. After the position is adjusted, the first hydraulic rod 17 can also limit the position of the horizontal moving plate 18 to prevent horizontal expansion and back-pushing of the horizontal moving plate 18 after the soil sample is compressed.

[0029] Several connecting rods 3 are movably connected between the two side plates 4. The two ends of the connecting rods 3 are threaded with second limiting nuts 6 that abut against the outside of the side plates 4. The connecting rods 3 connect the two side plates 4 into one unit through the second limiting nuts 6 and limit the two side plates 4 to prevent the side plates 4 from tilting due to horizontal expansion after the soil sample is compressed.

[0030] A baffle 15 is fixedly connected to the inner side of the side plate 4, which slides in contact with the vertical moving plate 14. The baffle 15 can restrict the horizontal movement of the vertical moving plate 14, preventing the vertical moving plate 14 from shifting due to the lateral expansion of the soil sample. In addition, the baffle 15 also serves as a reference for creating the inclined surface of the bottom soil sample. Both the baffle 15 and the side plate 4 are vertically equipped with a scale 8, so that the compaction thickness of the soil sample can be viewed through the scale 8.

[0031] An anti-slip pad 20 is provided in the through groove 19. After the vertical moving plate 14 passes through the through groove 19, it will come into contact with the anti-slip pad 20, thereby preventing the sample particles from leaking out. At the same time, it can also increase the friction force of the vertical moving plate 14 as it moves downward, preventing the vertical moving plate 14 from automatically moving downward due to gravity.

[0032] The compression mechanism includes a second hydraulic rod 12, with a pressure plate 13 connected to its lower end and a vertically arranged guide rod 9 connected to its upper end. A strip-shaped hole 11, cooperating with the guide rod 9, is provided on the top plate 7 along the extension / retraction direction of the first hydraulic rod 17. The second hydraulic rod 12 compresses the soil sample in the sample bundle mechanism by pushing the pressure plate 13 downwards. The strip-shaped hole 11 allows the second hydraulic rod 12 to move and adjust its position along the extension / retraction direction of the first hydraulic rod 17, ensuring that the pressing center of the second hydraulic rod 12 is aligned with the center of the soil sample to be compressed.

[0033] The guide rod 9 is threaded with a third limiting nut 10 that abuts against the upper surface of the top plate 7. After the third limiting nut 10 is tightened and abuts against the upper surface of the top plate 7, the position of the second hydraulic rod 12 can be locked to prevent the second hydraulic rod 12 from easily slipping.

[0034] A method for preparing transversely isotropic soil samples, using a transversely isotropic soil sample preparation device, the method comprising: S1, such as Figure 5 As shown in (a), a single-layer transversely isotropic soil sample is prepared. Based on relevant data, the soil sample density ρ and the thickness h of the single-layer soil sample are determined. The required soil sample mass m is then weighed. The formula for calculating the soil sample mass m is: m=ρhab Where a is the distance between the inner walls of the two side plates 4; b is the distance between the inner walls of the horizontal moving plate 18 and the vertical moving plate 14 at the initial position; Spread the soil sample evenly in the sample bundle mechanism, install the pressure plate 13 and the second hydraulic rod 12, and slowly apply pressure. After pressing the soil sample to a thickness h, stop applying pressure and stabilize the pressure for 30 minutes to allow the soil sample to set. Record the pressure reading p. S2. Prepare soil samples of different densities and thicknesses according to step S1 to meet the experimental requirements. S3. According to the required tilt angle α, control the first hydraulic rod 17 to adjust the position of the horizontal moving plate 18 so that the distance between the inner wall of the horizontal moving plate 18 and the inner wall of the vertical moving plate 14 after the adjustment is b'=cos(α)∙b, and add soil sample to compact to the target density. S4. After retracting the pressure plate 13, move the vertical moving plate 14 so that the vertical moving plate 14 moves down h' in the vertical direction, where h'==sin(α)∙b'. Use a tool to cut a slope with an angle of α. The tool is a soil cutting knife. Use a stiff brush to pull out small grooves on the slope to ensure the bonding force between the two soil samples.

[0035] S5. Move the vertical moving plate 14 to the initial height before the test, and put the prepared soil samples in the order required by the test. When putting in each soil sample, it is also necessary to pull out the soil sample at the bottom of the sample into a small trench and fill the gap at both ends with soil sample. S6. After the last layer of soil sample is placed, fill the upper slope with loose soil sample to a certain height, then compact the sample with the minimum compaction pressure from steps S1 and S2, and hold the pressure for at least 30 minutes. The soil sample mentioned above includes, but is not limited to, cohesive soil, sandy soil, and silty soil.

[0036] This application can improve the consistency between geotechnical testing and engineering practice, and more scientifically reveal the mechanical nature of soil, providing a safer, more economical, and reliable theoretical and parameter basis for geotechnical engineering design. The device has a simple structure, is easy to industrialize, and is convenient to operate, enabling scientific and production research under various working conditions.

[0037] Example 1: Prepare two soil samples with different densities (ρ1>ρ2) and a contact angle of 30°, where the compaction pressure of soil sample ρ1 is greater than that of soil sample ρ2. Figure 5 As shown in (b), the soil to be prepared to a density of ρ1 is evenly dispersed into the sample bundle mechanism (first prepare the part with high compaction pressure), and compacted to the target density. The second hydraulic rod 12 and pressure plate 13 are retracted, and the vertical moving plate 14 is moved downwards in the vertical direction by m = sin(30°)∙b. A slope with a 30° gradient is cut using a soil cutter, and small grooves are drawn on the slope using a stiff brush. The vertical moving plate 14 is moved upwards to the initial height before the test, and m2 of ρ2 density soil is evenly dispersed into the sample bundle mechanism for compaction. After compaction, the height of the upper soil sample is c = After reaching the predetermined compaction height and maintaining the pressure for at least 30 minutes, remove the sample and cut it into the required shape.

[0038] Example 2: Prepare three soil samples with different densities and a contact angle of 60°. The design densities of the three soil samples y1, y2, and y3 are ρ1, ρ2, and ρ3, respectively, and the design thicknesses are h1, h2, and h3 (or a thickness ratio of h1:h2:h3). The compaction pressures to the design densities at the design moisture content are p1, p2, and p3. The soil samples are stacked in the dip direction y1, y2, y3. First, weigh the required soil sample mass m. n =ρ n h n ab (n=1, 2, 3, a is the distance between the inner walls of the two side plates 4, b is the distance between the inner walls of the vertical moving plate 14 and the horizontal moving plate 18). Spread the y1 soil sample evenly in the sample-bundling mechanism, install the pressure plate 13 and the second hydraulic rod 12, and slowly apply pressure. Press the soil sample to thickness h1 according to the scale on the side plate 4, then stop applying pressure and hold the pressure steady for 30 minutes to allow the soil sample to solidify. Record the pressure reading p1. Prepare y2 and y3 soil samples according to this method. Since it is difficult to compact the soil samples after stacking when the soil layer inclination angle is large, when the inclination angle α>45°, first prepare the sample with an inclination angle α'=90°-α, and after the soil sample is solidified, rotate the soil sample 90° clockwise (or counterclockwise). In this embodiment, adjust the position of the horizontal moving plate 18 so that b'=cos(α')∙b. Add the y1 soil sample and compact it to the target density ρ1. Figure 5As shown in (c), retract the pressure plate 13 and the second hydraulic rod 12. Move the vertical moving plate 14 so that it moves downward in the vertical direction by h'=sin(α')∙b', cut a slope with an angle of α' using a soil cutter, and use a stiff brush to draw small grooves on the slope. Figure 5 As shown in (d), the vertical moving plate 14 is moved up to the initial height before the test. The previously compacted y1 soil sample is placed on the slope, and small grooves are drawn on the slope with a stiff brush to fill the surrounding gaps with loose y1 soil. The compacted y2 and y3 soil samples are placed on top in sequence following the above operation. Loose y3 soil is evenly spread to fill the slope and then raised 30mm higher. The soil sample is compacted with pressure p=min(p1, p2, p3) and the pressure is maintained for at least 30 minutes. After the soil sample is shaped, the sample is removed and rotated to an inclination angle of 60° to obtain the required multi-layered steeply inclined transversely isotropic soil sample.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A transversely isotropic soil sample preparation device, characterized in that, It includes an outer frame on which a soil sample compression mechanism for constraining the soil sample compression range is installed, and a compression mechanism located above the soil sample compression mechanism for compacting the soil sample in the soil sample compression mechanism is installed on the outer frame.

2. The transversely isotropic soil sample preparation device according to claim 1, characterized in that, The outer frame includes several vertically arranged support rods (5), and a bottom plate (1) and a top plate (7) are installed on the support rods (5).

3. The transversely isotropic soil sample preparation device according to claim 2, characterized in that, The support rod (5) is threaded with several first limiting nuts (2), which abut against the upper and lower surfaces of the bottom plate (1) and the top plate (7).

4. The transversely isotropic soil sample preparation device according to claim 2, characterized in that, The sample-binding mechanism includes two side plates (4) that are vertically fixed on the base plate (1) and are arranged in parallel and spaced apart. A horizontal moving plate (18) and a vertical moving plate (14) are movably arranged between the two side plates (4). A reaction seat (16) is fixedly arranged on the base plate (1). A first hydraulic rod (17) for pushing the horizontal moving plate (18) to move between the two side plates (4) is installed on the reaction seat (16). A through groove (19) for the vertical moving plate (14) to move is opened on the base plate (1).

5. The transversely isotropic soil sample preparation device according to claim 4, characterized in that, Several connecting rods (3) are movably connected between the two side plates (4), and the two ends of the connecting rods (3) are threadedly connected to a second limiting nut (6) that abuts against the outside of the side plate (4).

6. The transversely isotropic soil sample preparation device according to claim 4, characterized in that, The inner side of the side plate (4) is fixedly connected to a baffle (15) that slides in contact with the vertical moving plate (14).

7. The transversely isotropic soil sample preparation device according to claim 4, characterized in that, An anti-slip pad (20) is provided in the through groove (19).

8. The transversely isotropic soil sample preparation device according to claim 4, characterized in that, The compression mechanism includes a second hydraulic rod (12), the lower end of which is connected to a pressure plate (13), and the upper end of which is connected to a vertically arranged guide rod (9). A strip hole (11) that cooperates with the guide rod (9) is provided on the top plate (7) along the extension and retraction direction of the first hydraulic rod (17).

9. The transversely isotropic soil sample preparation device according to claim 8, characterized in that, The guide rod (9) is threaded with a third limiting nut (10) that abuts against the upper surface of the top plate (7).

10. A method for preparing transversely isotropic soil samples, characterized in that, Using the transversely isotropic soil sample preparation apparatus according to any one of claims 1-9, the method for preparing transversely isotropic soil samples includes: S1. Prepare a single-layer transversely isotropic soil sample. Determine the soil sample density ρ and the thickness h of the single-layer soil sample based on relevant data. Weigh the required soil sample mass m. The formula for calculating the soil sample mass m is: m=ρhab Where a is the distance between the inner walls of the two side plates (4); b is the distance between the inner walls of the horizontal moving plate (18) and the vertical moving plate (14) at the initial position; The soil sample is evenly spread in the sample bundle mechanism. After installing the pressure plate (13) and the second hydraulic rod (12), the pressure is slowly increased. After the soil sample is pressed to a thickness h, the pressure is stopped and the pressure is stabilized for 30 minutes to allow the soil sample to solidify. The pressure reading p is recorded. S2. Prepare soil samples of different densities and thicknesses according to step S1 to meet the experimental requirements. S3. According to the required tilt angle α, control the first hydraulic rod (17) to adjust the position of the horizontal moving plate (18) so that the distance between the inner wall of the horizontal moving plate (18) and the inner wall of the vertical moving plate (14) after the adjustment is b'=cos(α)∙b, and add soil sample to compact to the target density. S4. After retracting the pressure plate (13), move the vertical moving plate (14) so ​​that the vertical moving plate (14) moves down h' in the vertical direction, where h'=sin(α)∙b'. Use a tool to cut a slope with an angle of α. S5. Move the vertical moving plate (14) up to the initial height before the test, and put the prepared soil samples in the order required by the test. S6. After the last layer of soil sample is placed, fill the upper slope with loose soil sample, then compact the sample with the minimum compaction pressure in steps S1 and S2, and hold the pressure for at least 30 minutes.

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