System and method for observing microstructure evolution of loess based on in-situ micro-ct test

Abstract

The present application belongs to the technical field of microstructure imaging and loess test, and relates to a loess microstructure evolution observation system and method based on in-situ micro-CT test. Through hierarchical loading and synchronous CT scanning, the whole process of loess from initial structure adjustment to collapse occurrence and then to residual deformation under high pressure is captured completely, and the limitation of traditional test "step observation before and after collapse" is solved. The present application combines load-displacement curve and three-dimensional model, can quantize the cross influence of pressure and water saturation on microstructure and macroscopic deformation, realizes the observation of the evolution of the same soil sample structure in the collapse process, realizes the successive analysis of the microstructure before and after consolidation and collapse by combining CT and other observation means for multiple observations at the same position of the same sample, and through particle grade parameter statistics and three-dimensional model reconstruction, is conducive to establishing the "structure-mechanics" quantitative relationship model of loess collapse.

Description

Technical Field

[0001] This invention belongs to the field of microstructure imaging and loess testing technology, and relates to a loess microstructure evolution observation system and method based on in-situ micro-CT testing. Background Technology

[0002] The most typical characteristic of loess is its collapsibility, meaning that under external loads and water saturation, the strength of loess will significantly decrease and it will collapse, leading to various deformations of the soil and causing a series of geological disasters. The unique microstructure of loess is the main factor affecting its collapsibility and macroscopic mechanical behavior.

[0003] The microstructure of loess refers to the morphology, contact relationships, arrangement, cementation state, and pore size and distribution of its particles. Loess collapse is closely related to its microstructural characteristics; a certain amount of compressible space within the loess structure provides conditions for collapse. Under external loads and water saturation, the clay cement in the loess hydrates and expands, acting as a lubricant that causes particle slippage and subsequent collapse. A series of indoor experiments have shown that the hydration and expansion of clay cement under water saturation is a major contributing factor to reduced bond strength and loess collapse. High-precision observation techniques are an effective means of establishing a connection between microstructural parameters and macroscopic mechanical behavior.

[0004] For most existing studies, firstly, CT (Computed Tomography) and scanning electron microscopy techniques damage soil samples, making them unusable. Therefore, different soil samples must be used to observe the microstructure before and after collapsing, making it impossible to observe the evolution of the same soil sample's structure during collapsing. Secondly, considering that loess is a heterogeneous material and the small size of microscopic experiments, the microstructure of different parts of the same sample may vary significantly, and the structural differences between different samples are even greater. However, current experimental setups cannot simultaneously perform multiple observations at the same location on the same sample, combined with CT and other observation methods, to sequentially analyze the microstructure before and after consolidation and collapsing, hindering the continuous presentation of loess microstructural changes. Summary of the Invention

[0005] The purpose of this invention is to provide a loess microstructure evolution observation system and method based on in-situ micro-CT test, so as to solve the technical problems of not being able to observe the evolution of the same soil sample structure during consolidation and collapse, and not being able to conduct multiple observations at the same location of the same sample while combining CT and other observation methods to analyze the microstructure before and after consolidation and collapse.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides a loess microstructure evolution observation system based on in-situ micro-CT experiments, comprising:

[0008] The consolidation box has a barrel-shaped structure.

[0009] The sample bottom fixing part is placed inside the barrel-shaped consolidation box;

[0010] The sample top fixing part is placed at the opening of the barrel-shaped consolidation box;

[0011] The ring cutter has its two ends respectively embedded in the bottom fixing part and the top fixing part of the sample;

[0012] A columnar first permeable stone is movably embedded in the top fixing part of the sample. The outer diameter of the first permeable stone is the same as the inner diameter of the ring cutter and it can slide into the inside of the ring cutter.

[0013] A second permeable stone is located between the bottom fixing part of the sample and the ring cutter, and the outer diameter of the second permeable stone is equal to the outer diameter of the ring cutter.

[0014] The load pressurization unit is used to apply axial pressure to the loess sample inside the ring cutter through the barrel-shaped consolidation box and the first permeable stone.

[0015] The CT scanning unit is located on the outside of the barrel-shaped consolidation box.

[0016] Secondly, the present invention provides a method for observing the evolution of loess microstructure based on in-situ micro-CT experiments, comprising the following steps:

[0017] Loess samples were obtained by taking loess samples using the aforementioned ring cutter.

[0018] The loess sample is installed between the bottom fixing part and the top fixing part of the sample along with the ring cutter;

[0019] Loess consolidation-collapse test was conducted by applying graded loading to the loess sample using a load pressurization unit, and CT scan was performed using a CT scanning unit to obtain CT slices.

[0020] The CT slices were reconstructed to obtain a three-dimensional model of the same area of ​​the loess soil sample. Based on the three-dimensional model, the particle-level parameters were quantitatively statistically analyzed to quantify the changes in particles and parameters.

[0021] The loading force and displacement of the load-pressurizing unit are recorded in real time, and the load-displacement curve of the loess soil sample during the consolidation and collapse process is obtained based on the loading force and displacement.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention uses a barrel-shaped consolidation box to hold pure water, simulating the water-saturated conditions of loess. Both the consolidation box and the ring cutter are made of materials with high X-ray transmittance to reduce signal attenuation and ensure clear imaging of the internal microstructure. A load-pressurizing unit pushes the barrel-shaped consolidation box upwards, applying axial pressure to the loess sample within the ring cutter via a pressure head through the first permeable stone. This simulates pressure conditions under different engineering scenarios, facilitating the quantification of the relationship between collapsible deformation and pressure. Lateral deformation of the loess sample is limited by the sample bottom and top fixing parts nested at both ends of the ring cutter, preventing the sample from shifting or tilting during loading and ensuring uniform transmission of axial pressure. The outer diameter of the first permeable stone is the same as the inner diameter of the ring cutter, ensuring that the first permeable stone can be partially embedded within the ring cutter during loading, pressurizing the loess sample while preventing water seepage from the side walls. The outer diameter of the second permeable stone is equal to the outer diameter of the ring cutter, supporting the ring cutter and the loess sample while also preventing water seepage from the side walls. During the experiment, the first permeable stone at the top and the second permeable stone at the bottom of the loess sample formed a saturated channel, ensuring that water permeated evenly into the loess sample. A CT scanning unit was positioned outside the barrel-shaped consolidation box to perform tomographic scanning of the loess sample during the collapse process, generating a high-resolution three-dimensional model to facilitate the quantification of changes in parameters such as porosity and crack density. This invention, through the coordinated design of the consolidation box and the loading unit, simulates the saturated and compressive conditions of loess in actual engineering projects. Simultaneously, an X-ray detection unit captures the microstructural changes during the collapse process in real time, overcoming the limitations of traditional experiments that require "step-by-step observation before and after collapse." This invention enables continuous observation of the same sample, eliminating interference from differences between samples and making the correlation between microstructural parameters and macroscopic mechanical behavior more reliable. This invention can quantify the collapse rate and deformation mode of loess under different pressures and saturation levels, providing accurate parameters for foundation treatment and slope stability analysis, and reducing the risk of geological disasters.

[0024] This invention utilizes graded loading and simultaneous CT scanning to comprehensively capture the entire process of loess from initial structural adjustment to collapse and residual deformation under high pressure, overcoming the limitations of traditional experiments that involve step-by-step observation before and after collapse. By combining load-displacement curves and a three-dimensional model, this invention can quantify the combined effects of pressure and water saturation on microstructure and macroscopic deformation. It enables observation of the evolution of the same soil sample's structure during collapse, and allows for multiple observations at the same location on the same sample, combined with CT and other observational methods to progressively analyze the microstructure before and after consolidation and collapse. Through particle-level parameter statistics and three-dimensional model reconstruction, it facilitates the establishment of a quantitative "structure-mechanics" relationship model for loess collapse. Attached Figure Description

[0025] Figure 1 This is a perspective view of the overall structure of an embodiment of the present invention;

[0026] Figure 2This is a three-dimensional structural diagram of the consolidation box according to an embodiment of the present invention;

[0027] Figure 3 This is a front view of the consolidation box according to an embodiment of the present invention;

[0028] Figure 4 This is a top view of the consolidation box according to an embodiment of the present invention;

[0029] Figure 5 This is a three-dimensional structural diagram of the sample bottom fixing part according to an embodiment of the present invention;

[0030] Figure 6 This is a front view of the sample bottom fixing part according to an embodiment of the present invention;

[0031] Figure 7 This is a three-dimensional structural diagram of the sample top fixing part according to an embodiment of the present invention;

[0032] Figure 8 This is a front view of the sample top fixing part according to an embodiment of the present invention;

[0033] Figure 9 This is a three-dimensional structural diagram of the sample fixing and pressurizing part according to an embodiment of the present invention;

[0034] Figure 10 This is a front view of the fixed pressure section according to an embodiment of the present invention;

[0035] Figure 11 This is a process diagram of the sample bottom fixing part being installed into the consolidation box according to an embodiment of the present invention;

[0036] Figure 12 This is a process diagram of the sample top fixing part being embedded into the port of the consolidation box according to an embodiment of the present invention;

[0037] Figure 13 This is a diagram showing the state of a soil sample after it has been placed into the consolidation box, according to an embodiment of the present invention.

[0038] Figure 14 This is a load-displacement curve of a soil sample obtained based on CT scanning, according to an embodiment of the present invention.

[0039] Figure 15 This is a schematic diagram of XY two-dimensional slice data of particles in the same region obtained based on CT scan according to an embodiment of the present invention;

[0040] Figure 16 This is a schematic diagram of the distribution statistics of particle tilt angle evolution tracking in an embodiment of the present invention;

[0041] Figure 17 This is a schematic diagram of the distribution statistics of particle displacement evolution tracking according to an embodiment of the present invention;

[0042] Figure 18This is a flowchart of the in-situ test method for consolidation and collapsibility of small-sized loess samples according to an embodiment of the present invention.

[0043] Figure 19 This is a flowchart illustrating the microstructure tracking and evolution method of real loess particles under hydraulic action, as described in an embodiment of the present invention.

[0044] Figure 20 This is a flowchart of the loess microstructure evolution tracking method according to an embodiment of the present invention;

[0045] Figure 21 This is a flowchart of a method according to an embodiment of the present invention.

[0046] The components are as follows: 1. Consolidation box; 2. Sample bottom fixing part; 201. Sample bottom fixing seat; 202. Claw; 203. Groove; 204. Second permeable stone fixing groove; 3. Sample top fixing part; 301. First permeable stone sliding hole; 302. Ring cutter limiting ring; 303. Annular protrusion; 304. Second water filling hole; 4. Ring cutter; 5. Second permeable stone; 6. First permeable stone; 7. Load pressurization unit; 701. Stage; 702. Connecting rod; 703. Sample fixing pressurization part; 704. Pressurization head; 705. Dynamic loading unit; 706. Disc; 707. First water filling hole; 8. CT scanning unit; 801. X-ray source; 802. X-ray detector; 9. Supplemental light; 10. Signal line; 11. Chassis support. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0048] It should be noted that the terms "first," "second," etc., in the specification and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0049] The present invention will now be described in further detail with reference to the accompanying drawings:

[0050] Example 1:

[0051] See Figure 1 This invention discloses a loess microstructure evolution observation system based on in-situ micro-CT test, including a barrel-shaped consolidation box 1, a sample bottom fixing part 2, a sample top fixing part 3, a ring cutter 4, a second permeable stone 5, a first permeable stone 6, a load pressurization unit 7, and a CT scanning unit 8.

[0052] See Figure 2 , Figure 3 and Figure 4 This is a schematic diagram of the consolidation box 1. The barrel-shaped consolidation box 1 is used to hold pure water to simulate the water-saturated conditions of loess. It also serves as an intermediate component for transmitting the loading force to the load-pressurizing unit 7.

[0053] In this embodiment of the invention, both the barrel-shaped consolidation box 1 and the ring cutter 4 are made of PEEK plastic or carbon fiber composite material with an X-ray transmittance greater than 90%. PEEK plastic and carbon fiber composite material have high X-ray transmittance and good mechanical properties, with high tensile strength and elastic modulus, which helps to reduce signal attenuation and ensure clear imaging of the internal microstructure of loess soil samples.

[0054] In this embodiment of the invention, the diameter of the ring cutter 4 is 10mm, the height of the ring cutter 4 is 10mm, and the wall thickness of the ring cutter 4 is 1mm.

[0055] See Figure 1 The sample bottom fixing part 2 is placed inside the barrel-shaped consolidation box 1, see [reference]. Figure 5 and Figure 6 See the schematic diagram of the bottom fixing part 2 of the sample. Figure 11 This is a diagram showing the state when the sample bottom fixing part 2 is placed inside the consolidation box 1. (See also...) Figure 1 The top fixing part 3 of the sample is placed at the opening of the barrel-shaped consolidation box 1, see [reference]. Figure 7 and Figure 8 This is a schematic diagram of the sample top fixing part 3. See also 12, which shows the state when the sample top fixing part 3 is placed into the opening of the consolidation box 1. Figure 1 The two ends of the ring cutter 4 are respectively embedded in the bottom fixing part 2 and the top fixing part 3 of the sample. By nesting the two ends of the ring cutter in the bottom fixing part 2 and the top fixing part 3 of the sample, the axial position of the loess sample is fixed, preventing the loess sample from shifting or tilting during the loading process, and ensuring that the axial pressure is transmitted evenly.

[0056] See Figure 1 and Figure 13The columnar first permeable stone 6 is movably embedded in the top fixing part 3 of the sample. The outer diameter of the first permeable stone 6 is the same as the inner diameter of the ring cutter 4 and can slide into the ring cutter (4) to ensure that the first permeable stone 6 can be partially embedded in the ring cutter 4 during the loading of the load pressurizing unit 7, pressurize the loess soil sample, and prevent water from seeping from the side wall.

[0057] See Figure 7 and Figure 8 In this embodiment of the invention, a first permeable stone sliding hole 301 is provided on the sample top fixing part 3, and the first permeable stone 6 is embedded in the first permeable stone sliding hole 301. A ring cutter limiting ring 302 is provided on the sample top fixing part 3, and the end of the ring cutter 4 is embedded in the inner hole of the ring cutter limiting ring 302. The ring cutter limiting ring 302 is coaxially arranged with the first permeable stone sliding hole 301, and the inner diameter of the first permeable stone sliding hole 301 is smaller than the hole diameter of the ring cutter limiting ring 302.

[0058] See Figure 7 and Figure 8 In this embodiment of the invention, the sample top fixing part 3 is provided with an annular protrusion 303, the sample top fixing part 3 is embedded in the opening of the consolidation box 1, the annular protrusion 303 is placed on the opening, and the outer diameter of the annular protrusion 303 is greater than or equal to the outer diameter of the consolidation box 1.

[0059] See Figure 1 The second permeable stone 5 is located between the bottom fixing part 2 of the sample and the ring cutter 4. The outer diameter of the second permeable stone 5 is equal to the outer diameter of the ring cutter 4 to support the ring cutter 4 and the loess sample, while preventing water from seeping from the side wall. During the test, the first permeable stone 6 at the top of the loess sample and the second permeable stone 5 at the bottom form a water-saturated channel to ensure that water permeates evenly into the interior of the loess sample.

[0060] See Figure 5 and Figure 6 In this embodiment of the invention, the sample bottom fixing part 2 includes a sample bottom fixing seat 201 and a plurality of claws 202 arranged in the same circle. The claws 202 are fixedly connected to the sample bottom fixing seat 201. A groove 203 is formed between two adjacent claws 202. When water is added, the groove 203 allows water to contact the second permeable stone 5, enabling water to quickly pass through the permeable stone and contact the soil sample, maintaining sufficient saturation, increasing the contact area between the water and the second permeable stone, and promoting the sample saturation process. The end of the ring cutter 4 and the second permeable stone 5 are engaged between the plurality of claws 202. The claws 202 have an arc surface, which fits against the ring cutter 4 and the second permeable stone 5 to ensure contact stability. The second permeable stone 5 is located between the sample bottom fixing seat 201 and the ring cutter 4.

[0061] See Figure 5 In this embodiment of the invention, a second permeable stone fixing groove 204 is provided on the sample bottom fixing seat 201, and the end of the second permeable stone 5 is embedded in the second permeable stone fixing groove 204 to ensure the stability of the connection between the second permeable stone 5 and the sample bottom fixing seat 201.

[0062] See Figure 1 The load-pressurizing unit 7 is used to apply axial pressure to the loess sample inside the ring cutter 4 through the barrel-shaped consolidation box 1 and the first permeable stone 6, simulating pressure conditions under different engineering scenarios, and facilitating the quantification of the relationship between collapse deformation and pressure. The load-pressurizing unit 7 can achieve constant rate loading or stepped loading, and combined with the CT scanning unit 8, it can observe the dynamic changes of the pore structure in real time during the collapse process.

[0063] See Figure 1 In this embodiment of the invention, the load pressurizing unit 7 includes a platform 701, on which a power loading unit 705 is provided. The power loading unit 705 is located between the solidification box 1 and the platform 701. A disc 706 is provided between the power loading unit 705 and the solidification box 1. The outer diameter of the disc 706 is equal to the outer diameter of the bottom of the solidification box 1 to prevent damage to the solidification box 1 during the pressurization process of the power loading unit 705. The platform 701 is connected to a sample fixing and pressurizing part 703 by several connecting rods 702. The connecting rods 702 are hollow and made of carbon fiber composite material or PEEK plastic. The sample fixing and pressurizing part 703 is provided with a pressurizing head 704. The pressurizing head 704 contacts the first permeable stone 6 and is located on the side of the first permeable stone 6 away from the ring cutter 4. During the pressure test, the output end of the power loading unit 705 applies pressure to the ring cutter 4 through the disc 706, the consolidation box 1, the sample bottom fixing seat 201, and the second permeable stone 5, and applies pressure to the loess sample in conjunction with the top pressure head 704.

[0064] See Figure 9 and Figure 10 In this embodiment of the invention, the sample fixing and pressurizing part 703 is provided with a plurality of first water filling holes 707, and the sample top fixing part 3 is provided with a plurality of second water filling holes 304. The first water filling holes 707 and the second water filling holes 304 correspond one-to-one in the axial direction of the consolidation box 1, which facilitates the insertion of a water supply pipe into the consolidation box 1 from the outside.

[0065] See Figure 1 The CT scanning unit 8 is arranged on the outside of the barrel-shaped consolidation box 1 to perform tomographic scanning on the loess soil sample during the collapse process, generating a high-resolution three-dimensional model, which facilitates the quantification of changes in parameters such as porosity and crack density.

[0066] See Figure 1 In this embodiment of the invention, the CT scanning unit 8 includes an X-ray source 801 and an X-ray detector 802, which are located on opposite sides of the consolidation box 1. The X-ray source 801 is used to emit X-rays, and the X-ray detector 802 is used to receive X-rays.

[0067] See Figure 1 In this embodiment of the invention, a supplementary light 9 and a chassis support 11 are also included. The supplementary light 9 is located on top of the load pressurization unit 7. The load pressurization unit 7 and the CT scanning unit 8 are both arranged on the chassis support 11. The supplementary light 9 is used to provide illumination when assembling samples.

[0068] This invention simulates the water-saturated and compressive conditions of loess in actual engineering projects through the coordinated design of a consolidation box and a loading unit. Simultaneously, it utilizes an X-ray detection unit to capture microstructural changes during the collapse process in real time, overcoming the limitations of traditional experiments that require separate observations before and after collapse. This invention enables continuous observation of the same sample, eliminating interference from differences between samples and making the correlation between microstructural parameters and macroscopic mechanical behavior more reliable. Furthermore, this invention can quantify the collapse rate and deformation patterns of loess under different pressures and water saturation levels, providing precise parameters for foundation treatment and slope stability analysis, and reducing the risk of geological disasters.

[0069] See Figure 21 Based on the above system, this invention also discloses a method for observing the evolution of loess microstructure based on in-situ micro-CT experiments, comprising the following steps:

[0070] S1, loess samples are obtained by sampling loess using the ring cutter 4, including:

[0071] The ring cutter 4 is used to take samples from the original loess sample. During the soil sample preparation process, the cutting edge of the ring cutter 4 is pressed into the soil evenly with the cutting edge facing down until the cylinder of the ring cutter 4 is filled with soil sample.

[0072] Use a soil-cutting knife to cut open the soil sample around the ring cutter 4 and wipe the outer wall of the ring cutter 4 clean.

[0073] S2, the loess sample is installed between the bottom fixing part 2 and the top fixing part 3 of the sample along with the ring cutter 4.

[0074] S3, a loess consolidation-collapse test is conducted by applying graded loading to the loess sample through the load pressurization unit 7, and CT scan is performed using the CT scanning unit 8 to obtain CT slices, as shown below:

[0075] S31, apply 200 kPa axial pressure to the loess sample through the load pressurization unit 7 and perform an initial scan. 200 kPa is close to the pressure conditions of a typical shallow foundation or slope surface. The initial scan results can reflect the structure of loess in its natural state, provide a basis for analyzing the collapse threshold, and record the original microstructure of the loess sample when it is not collapsed, as a benchmark for subsequent collapse process comparison.

[0076] S32, an axial pressure of 800 kPa is applied to the loess sample through the load pressurization unit 7, and a second scan is performed. The 800 kPa pressure is close to the load conditions in the middle of a medium-depth foundation or slope. At this time, the particles inside the loess begin to rearrange and the pores are compressed.

[0077] S33, apply 800 kPa axial pressure to the loess sample through the load pressurization unit 7 and perform saturation treatment. Let it stand for at least 24 hours to allow water to fully penetrate, triggering the hydration and expansion of the clay cement, resulting in particle slippage and structural collapse, and then perform a third scan.

[0078] S34, 1600 kPa axial pressure is applied to the loess sample through the load pressurization unit 7 and a fourth scan is performed. 1600 kPa is close to the load conditions of deep foundation or the bottom of high slope.

[0079] The scanning parameters for the initial scan, the second scan, the third scan, and the fourth scan are set to voltage / power ≥ 80kV / 7W, 1000×1000×1000 voxels, and the scanning area is locked to the central area of ​​φ1mm×H1mm, representing that the scanning area is a cylinder, where φ is the diameter of the cylinder and H represents the height of the cylinder.

[0080] S4. Reconstruct the model from the CT slices to obtain a 3D model of the same area as the loess soil sample, as shown below:

[0081] The CT slices obtained from the initial, second, third, and fourth scans were reconstructed to obtain a three-dimensional model of the same area of ​​the loess soil sample. Based on the three-dimensional model, the microstructural changes corresponding to key points in the load-displacement curve were analyzed to establish a quantitative relationship between macroscopic deformation and microscopic failure.

[0082] Based on the aforementioned three-dimensional model, quantitative statistics of particle-level parameters are performed to quantify and statistically analyze particle and parameter changes, facilitating quantitative analysis of the evolution of structural parameters during the collapse process.

[0083] S5 records the loading force and displacement of the load-pressurizing unit 7 in real time, and obtains the load-displacement curve of the loess soil sample during the consolidation and collapse process based on the loading force and displacement. The load-displacement curve directly reflects the macroscopic mechanical behavior of the loess soil sample during the consolidation and collapse process, providing a design basis for engineering applications.

[0084] This invention, through graded loading and simultaneous CT scanning, comprehensively captures the entire process of loess from initial structural adjustment to collapse and residual deformation under high pressure, overcoming the limitations of traditional experiments that involve step-by-step observation before and after collapse. Combining load-displacement curves and a three-dimensional model, this invention can quantify the combined effects of pressure and water saturation on microstructure and macroscopic deformation. This invention enables the observation of the evolution of the same soil sample's structure during collapse, allowing for multiple observations at the same location on the same sample while simultaneously analyzing the microstructure before and after consolidation and collapse using CT and other observational methods. Through particle-level parameter statistics and three-dimensional model reconstruction, it facilitates the establishment of a quantitative "structure-mechanics" relationship model for loess collapse.

[0085] Example 2:

[0086] See Figure 18 This embodiment discloses a method for observing the evolution of loess microstructure based on in-situ micro-CT experiments, including the following steps:

[0087] First, based on comparative analysis of basic experimental data, a specimen diameter of 10.0 mm was selected as optimal for the loess confinement test. A carbon fiber composite ring cutter 4 with a diameter of 10 mm and a height of 10 mm was designed, and corresponding undisturbed loess samples were prepared. During sample preparation, to reduce the lateral confinement effect of the ring cutter 4, samples were taken directly from the undisturbed loess sample. In this experiment, to minimize the lateral confinement effect of the ring cutter 4, samples were taken directly from a well-preserved cubic undisturbed loess sample with a side length of approximately 50 cm. During sample preparation, the ring cutter 4 was pressed evenly into the soil with its cutting edge facing downwards until the cylinder of the ring cutter 4 was filled with soil sample. The soil sample around the ring cutter 4 was cut with a soil-cutting knife, and the outer wall of the ring cutter 4 was carefully wiped. After sampling, the second permeable stone 5, the loess sample, and the first permeable stone 6 were sequentially placed into the consolidation box 1. In this process, in order to reduce the disturbance of the soil sample, it is necessary to ensure that the outer wall of the ring cutter 4 and the first permeable stone 6 is tightly sealed with the top fixing part 3 of the sample, the outer wall of the ring cutter 4 and the second permeable stone 5 is tightly sealed with the bottom fixing part 2 of the sample, and the top fixing part 3 and the bottom fixing part 2 of the sample are tightly sealed with the consolidation box 1.

[0088] Based on the dimensions of the carbon fiber composite ring cutter 4, this invention proposes a matching in-situ consolidation collapse testing device. The device comprises a consolidation box 1, a sample bottom fixing part 2 to stabilize the sample bottom, a sample top fixing part 3 to stabilize the sample top, and a load-applying unit 7. The consolidation box 1 is made of the same material as the ring cutter 4, has good X-ray transmittance, and is designed as a cylindrical groove, which can match the stage 701 of the X-ray computed tomography (CT) scanner and can also store pure water to saturate the loess sample. The ring cutter limiting ring 302 of the sample top fixing part 3 and the claw 202 of the sample bottom fixing part 2 are both frustum-shaped structures, providing sufficient transmission space for the X-ray source and ensuring scanning accuracy. The sample top fixing part 3 is connected to the load-applying unit 7, allowing precise control of the loading force.

[0089] X-ray computed tomography (CT) technology was integrated with the designed consolidation collapse testing device to form an integrated in-situ testing system. The accuracy and loading method of the load-pressurizing unit 7 were determined: a stress-controlled loading mode was adopted, with a constant minimum loading rate. The accuracy and stability of the loading process were ensured by real-time monitoring of the changes in loading force and displacement of the load-pressurizing unit 7.

[0090] Multiple scans of undisturbed loess samples were performed using CT scanning unit 8. The same scan area was marked with a crosshair on the loess sample display interface to ensure accuracy and repeatability. The microstructure of the soil sample was continuously scanned at 150 kPa, before and after 700 kPa water saturation, and at 1500 kPa water retention. The specific steps are as follows:

[0091] An initial scan was performed under an axial pressure of 150 kPa, followed by a second scan at 7000 kPa. A saturation treatment was then performed under 7000 kPa axial pressure, followed by a third scan after 24 hours of rest. Finally, a fourth scan was performed at 1500 kPa. The parameters for each scan were uniformly set as follows: voltage / power ≥ 80 kV / 7 W, resolution 1~1.5 μm / pixel, 1000×1000×1000 voxels, and the scanning area was locked to the central region of φ1~φ1.5 mm × H1 mm.

[0092] By recording the changes in loading force and loading platform displacement in real time, the load-displacement curves of loess soil samples during the consolidation and collapsibility process were continuously observed. During loading, high-precision load and displacement sensors were used to acquire data in real time. The load and displacement data were synchronously transmitted to a computer through a data acquisition system to generate load-displacement curves. These curves reflect the mechanical response of the soil sample at different loading stages, providing important macroscopic data support for analyzing the consolidation and collapsibility characteristics of loess.

[0093] Example 3:

[0094] See Figure 19 This embodiment also discloses a method for observing the evolution of loess microstructure based on in-situ micro-CT experiments, including the following steps:

[0095] Based on the selected undisturbed loess, soil samples containing ring cutters with a diameter of 10 mm and a height of 10 mm were prepared. This size was chosen based on extensive preliminary experiments and data analysis, aiming to balance the operability of the experiment with the representativeness of the soil samples. The soil samples were taken from a typical loess layer at a depth of 5 meters to ensure the representativeness of the undisturbed structure and composition of the soil samples.

[0096] Furthermore, the prepared ring-shaped soil sample is assembled with a specially designed consolidation box 1 and integrated into the CT scanning unit 8 and the load pressurization unit 7. This process requires extremely high precision and meticulous operation to ensure that the position and state of the soil sample remain unchanged during the test. The consolidation box 1 is made of high-strength, lightweight carbon fiber reinforced polyetheretherketone (CF / PEEK) composite material, which not only provides sufficient mechanical strength to withstand the high pressure during the test, but also ensures high X-ray transmittance, thereby ensuring the clarity and accuracy of the CT scan images.

[0097] Using a high-precision CT scanning unit 8, undisturbed loess samples were scanned multiple times to obtain the microstructure of the same area before and after different hydraulic treatments. The scanned samples were subjected to four conditions: 200 kPa axial stress, 800 kPa axial stress, 800 kPa water saturation followed by settling, and 1600 kPa axial stress. Each scan was precisely positioned in the same area, ensuring data comparability and continuity. These scans allowed for detailed observation of the microstructural changes in the loess samples under different stress and saturation conditions, including particle arrangement, pore size, and shape.

[0098] Furthermore, using a 3D image visualization system, CT slices obtained from multiple scans were reconstructed to obtain 3D models of the same region in the loess soil sample. This step involves a large amount of image processing and data analysis, including image preprocessing, threshold segmentation, feature extraction, and 3D reconstruction. Through these 3D models, we can intuitively observe the 3D morphology of the internal structure of the loess soil sample, providing a foundation for further microstructural analysis.

[0099] Finally, the dynamic changes of microscopic parameters such as particle tilt angle and particle displacement were statistically analyzed to track the evolution of loess microstructure. This analysis included not only static parameters of particles, such as size, shape, and distribution, but also dynamic parameters, such as particle displacement and rotation under different stress and saturation conditions. Through the statistical analysis of these parameters, a deeper understanding of the microstructural change mechanism of loess during collapsing can be achieved, providing a scientific basis for the assessment of loess engineering properties and disaster prevention.

[0100] Example 4:

[0101] See Figure 20 This embodiment discloses a method for observing the evolution of loess microstructure based on in-situ micro-CT experiments, mainly including... Figure 20 The steps are as follows: First, undisturbed loess samples were prepared using a small-sized carbon fiber composite ring cutter (φ10mm×H10mm), and integrated with a loading-water-saturated consolidation box 1 within a CT scanning chamber. Then, in-situ CT scans were performed sequentially under four conditions: 200kPa axial stress, 800kPa axial stress, 800kPa axial stress after water saturation and settling, and 1600kPa axial stress. Finally, a submicron-level model reconstruction was performed on the CT sequence slices using a three-dimensional image visualization system, and quantitative statistics were conducted based on particle-level parameters to quantify changes in particle parameters, enabling dynamic tracking of the microstructure evolution during loess collapse. This method, through the synergistic control of multi-condition CT scanning and mechanical loading, reveals the dynamic response mechanism of loess microstructure under load-water saturation.

[0102] Step 1: First, a carbon fiber composite ring cutter 4 of suitable size is designed. When the diameter of the loess consolidation test soil sample is large, subsequent reconstruction of CT images of a local area (1mm edge length of the imaging area) of the loess consolidation specimen can only be performed at micron resolution. The microscopic CT images of consolidated loess are affected by the surrounding soil outside the imaging area, exhibiting significant noise, making it impossible to reconstruct accurate three-dimensional particle and pore models to analyze the microstructural evolution of loess. When the diameter of the loess sample in the consolidation test is small, the mechanical properties of the sample may be significantly affected by the loading head and the sidewall of the ring cutter, resulting in excessive errors compared to standard indoor test results. Therefore, after comparing and analyzing basic experimental data, a specimen diameter of 10.0mm is selected as optimal for the loess consolidation test, i.e., a small-sized carbon fiber ring cutter φ10mm×H10mm. The material of the ring cutter 4 is selected as carbon fiber composite material because carbon fiber composite material has the characteristics of being lightweight, high strength, high modulus, fatigue resistant, easily permeable to X-rays and having low absorption rate. It has wide applications in modern medical equipment such as X-ray diagnostic instruments, CT scanners, and radiotherapy machines.

[0103] Furthermore, a ring-shaped soil sample with a diameter of 10 mm and a height of 10 mm was prepared. The sampling depth of this invention was 5 meters, and the original block size was 50 cm × 50 cm × 50 cm. The small ring-shaped sampler used for secondary sampling had an inner diameter of 10 mm and a height of 10 mm, resulting in a cylindrical loess sample with a diameter of 10 mm and a height of 10 mm. Due to the relatively small sample size, secondary sampling was performed directly within the original block, which facilitated the sampling operation and avoided the lateral confinement effect of small ring-shaped samplers.

[0104] Step 2: Based on the designed experimental setup, an in-situ consolidation and collapsibility test device matching the ring cutter 4 was designed. The in-situ consolidation and collapsibility test device mainly consists of a consolidation box 1, a sample bottom fixing part 2 to stabilize the bottom of the ring cutter soil sample, and a sample top fixing part 3 to stabilize the top of the ring cutter soil sample. The consolidation box 1 is made of the same material as the ring cutter 4, possessing good X-ray transmittance. The consolidation box 1 is designed as a cylindrical groove, partly to match the loading stage of the X-ray computed tomography (CT) scanner, and partly to store sufficient pure water to saturate the loess sample. The claws 202 of the sample bottom fixing part 2 have a frustum structure, ensuring structural strength and stability while minimizing obstruction of the fan-shaped X-ray transmission path, providing sufficient transmission space for the X-ray source and ensuring the required scanning accuracy. The claws 202 are used to stabilize the bottom of the ring cutter soil sample, and there are slots 203 between adjacent claws 202. The function of the slots 203 is to allow water to quickly pass through the permeable stone to contact the soil sample and maintain sufficient wetting when water is added. The ring cutter limiting ring 302 of the sample top fixing part 3 provides sufficient space at the top when the X-ray source passes through the sample. Simultaneously, the sample top fixing part 3 has a first permeable stone sliding hole 301 and a ring cutter limiting ring 302. Thus, when the sample top fixing part 3 comes into contact with the ring cutter 4 and the loess sample, the ring cutter 4 can be completely embedded in the sample top fixing part 3, maintaining the stability of the loess sample and the uniformity of the loading process. The second water inlet hole 304 is a channel for water saturation, facilitating water addition and ensuring complete saturation of the soil sample. The sample fixing and pressurizing part 703 has a first water inlet 707 that matches the second water inlet 304, ensuring direct access of the water inlet pipe. The sample fixing and pressurizing part 703 has a screw hole on its periphery for fixing the connecting rod 702. The sample fixing and pressurizing part 703 is fixedly connected to the stage 701 through the connecting rod 702. The sample fixing and pressurizing part 703 has a protruding pressurizing head 704 in the middle. The pressurizing head 704 matches the sliding hole 301 of the first permeable stone. The pressurizing head 704 is in direct contact with the lower first permeable stone 6, ensuring stable loading of the sample during the loading process and facilitating displacement recording.

[0105] Preferred, see Figures 11 to 13This is a schematic diagram of the in-situ testing device and loess sample assembly steps according to an embodiment of the present invention. The installation sequence is as follows: First, the consolidation box 1 and the sample bottom fixing part 2, which stabilizes the bottom of the sample, are assembled. Then, the second permeable stone 5 is placed in the second permeable stone fixing groove 204, followed by the filter paper, the ring cutter 4 containing the loess sample, and the first permeable stone 6. Based on this, the sample top fixing part 3, which stabilizes the top of the sample, is slowly placed into the consolidation box 1. The assembled schematic diagram is shown below. Figure 13 As shown. After the loess sample is placed and assembled, the height of the visible area between the bottom fixing part 2 and the top fixing part 3 of the sample ring cutter 4 is 4mm, which preserves sufficient observation space. At the same time, the placement of the upper and lower permeable stones forms a water infiltration channel, providing conditions for saturated loading.

[0106] Step 3: Assemble the assembled ring cutter soil sample, consolidation box 1, CT scanning unit 8, and load pressurization unit 7. The overall structure diagram is shown below. Figure 1 As shown. The assembled ring cutter soil sample and consolidation box 1 are placed directly on the disc 706. The bottom of the consolidation box 1 is basically the same size as the disc 706, which facilitates precise positioning of the central area. The sample fixing and pressurizing part 703 is installed. The sample fixing and pressurizing part 703 is fixed to the lower stage 701 by the four surrounding connecting rods 702. The connecting rods 702 are connected to the sample fixing and pressurizing part 703 by bolts to ensure the stability of the overall structure. The power loading unit 705 of the X-ray computed tomography scanning device is attached to the bottom of the disc 706. It is connected to the external loading control device through the signal line 10. At the same time, the power loading unit 705 is connected to the computer that monitors and records the load displacement curve in real time to realize stable, continuous and uninterrupted data monitoring during the loading process. The working principle of X-ray microscopy is that the X-ray microscope forms an image based on the X-rays that pass through the sample. If more X-rays are absorbed by the sample, the image is darker; if more X-rays pass through the sample, the image is brighter. The absorption of X-rays increases with the increase of density and thickness. The magnification of an X-ray microscope is typically achieved by utilizing projection geometry formed by point source illumination (such as the geometry in the Xradia Versa), or by using optical elements similar to those in a conventional visible light microscope (such as the optical elements in the Xradia Ultra). The X-ray detector 802 collects X-ray images of the loess sample. All objectives except the 0.4× objective are visually similar and are mounted on a motorized turntable (similar to how optical microscopes have different objectives).

[0107] Step 4: With the initial state prepared, the load-applying unit 7 applies load force. This experiment preset four loading modes: applying a load of 200 kPa, applying a load of 800 kPa, subsidence under a load of 800 kPa, and subsidence under a load of 1600 kPa. These are four typical working condition selection points, corresponding to... Figure 14 The four working points marked in the figure are 200kPa, 800kPa, W800kPa and W1600kPa. The original data is the experimental data measured by the in-situ CT loading device, the fitted data is the fitting of the original data, and the load-displacement curve is the experimental data measured by the conventional soil consolidation instrument.

[0108] Furthermore, when the load reached the 200 kPa working point, the loess soil sample was scanned for the first time with an axial pressure of 200 kPa based on CT scanning unit 8. The highest resolution (volume pixels) adopted by the observation was 1.5005 μm, and each scan image consisted of 1000 × 1000 pixels, resulting in 1000 slices. Therefore, the actual scanned area was a cylindrical region with a diameter and height of 1 mm.

[0109] Step 5: Using the load pressurization unit 7, the loading force is controlled to reach 800 kPa for the second scan. After the soil sample completes the first scan under 200 kPa axial pressure, the sample position and scanning coordinate system remain fixed. The load pressurization unit 7 continues to apply axial load at the minimum constant rate controlled by the control device until the target stress reaches 800 kPa. During the loading process, real-time closed-loop feedback is provided through the load sensor and displacement sensor. After reaching 800 kPa, this stress level is maintained in a continuously saturated state to eliminate microstructural disturbances caused by instantaneous stress relaxation during loading. Subsequently, based on the scanning coordinate reference established in Step 4, a second CT scan is performed on the sample. To further improve the spatial matching accuracy of multiple scans, the scanning area is precisely located to facilitate adjustment of the height range of the slice data as the displacement changes.

[0110] Step 6: Under continuous load, saturate the soil sample with water, and perform three scans after settling. During this process, maintain the load condition and inject pure water through the first water inlet 707 and the second water inlet 304. The first water addition is performed slowly, monitored by observing the rise in water level within the consolidation chamber 1 and the pre-measured volume of injected water to prevent excessive water overflow. After the first water addition, allow the sample to stand and observe the uniform permeation through the two permeable stones over a certain period. Once the water level drops, slowly add water in small amounts multiple times until the sample is fully saturated. After the sample is fully saturated, allow it to stand for 24 hours before performing the third scan. Similarly, to ensure the accuracy of multiple scans, precisely locate the specific scan area selected in the previous two scans. Adjust the observation height range according to the displacement and find the same particles before performing the third scan of the soil sample.

[0111] Step 7: Continue applying the load, controlling the loading force to 1600 kPa for the fourth scan. After the wetting and settling process in Step 6, continue applying the axial load at a slower rate using the load pressurization device until the stress reaches 1600 kPa. When the stress stabilizes within 1600 kPa ± 5 kPa, maintain this position for a certain period to allow the rearranged particle skeleton after wetting to reach a new equilibrium state. Subsequently, call back the previously set scanning coordinate system and perform the fourth CT scan. Before scanning, dynamically adjust the starting height of the scan by comparing the historical height coordinates with the current top surface position of the sample to ensure that the observation area always covers the same particle population. The parameters for the four scans are completely consistent: resolution 1.5005 μm, 1000 × 1000 pixels × 1000 slices, and scanning area φ1 mm × H1 mm.

[0112] Preferably, continuous load-displacement curves are obtained for four working conditions: 200 kPa, 800 kPa, W800 kPa, and W1600 kPa, as shown below. Figure 14 As shown. Figure 14 This figure shows the load-displacement curves obtained from four consecutive working conditions during a loess microstructure test. The horizontal axis represents the load (force) from 0 to 180 N, corresponding to the magnitude of the applied force under different conditions. The vertical axis represents the displacement, with the initial displacement value at 14.978 mm (the starting point of displacement monitoring). As consolidation and collapse occur, the displacement monitoring point shows a continuous decreasing trend. Due to the cyclical alternation of pressurization and stabilization of the power unit under loading conditions, the original data monitoring points exhibit fluctuations. During data analysis, a basic slope for the load-displacement curve was fitted. Based on this, the points where the initial loading force was reached in each instance were connected to obtain the actual load-displacement curve.

[0113] Step 8: Using a 3D image visualization and analysis system, reconstruct the model from the scanned CT slices. Further construct the 3D microstructure of the soil sample; the complete process encompasses two major stages: 2D slice data preprocessing and 3D microstructure reconstruction. First, batches of continuous grayscale images acquired from CT scans are imported into the 3D image visualization and analysis system. Then, through fine operations such as threshold segmentation and particle porosity division, a model is generated, as shown below. Figure 15 The image shown is a two-dimensional slice. After the two-dimensional slice processing is completed, the preprocessed two-dimensional slice image sequence is overlaid in three dimensions to reconstruct a three-dimensional model, and then outputs visualization results such as particle rendering model and pore network model. Figure 15 The results visually present a continuous comparison of the cross sections of the same soil sample area before and after loading and before and after collapsing. From the grayscale and morphological changes of the two-dimensional cross section, the longitudinal rotation of particles, the small displacement of local particles, and the micro-evolutionary characteristics of the overall particle arrangement tending to be more compact can be clearly observed.

[0114] Step 9: Quantitatively analyze changes in parameters such as particle tilt angle and displacement to track the evolution of loess microstructure. Particle tilt angle (Phi, the angle between the long axis of the particle and the horizontal plane) is a key parameter in the evolution of loess microstructure, with a value between 0 and 90°. In this embodiment, the larger the Phi, the more the long axis of the particles tends to be distributed horizontally, and the more stable the particles are.

[0115] further, Figure 16 By comparing and analyzing the distribution statistics of particle tilt angle evolution under loading and collapsibility conditions, it can be concluded that: during the change of working conditions from 200 kPa to 800 kPa, the number of particles with tilt angles of 0-50° decreased significantly, but the proportion of particles with tilt angles of around 80° increased; during the change of working conditions from 800 kPa to 800 kPa, the number of particles with tilt angles of 0-50° decreased, while the number of particles with tilt angles of 80-90° increased significantly. This indicates that the particles underwent displacement and tilting during loading, and the overall particle structure was not completely stable. During the water saturation process, the particles exhibited significant rotation, and data quantification analysis revealed a clear trend of change from vertical to horizontal rotation.

[0116] Furthermore, Figure 17 The relationship between particle vertical displacement and coordinates under 800 kPa pressure in both un-watered and water-watered states is presented. It can be seen that the data points in the un-watered state can be well fitted by a straight line, and the slope of this fitted line approximately represents the vertical strain at the loess sample scale. For the water-watered state, the particle vertical displacement data exhibits irregular bands, reflecting that while the particles undergo overall compressive deformation at the loess sample scale, significant local deformation also occurs at the particle scale. Therefore, when the overall deformation at the loess sample scale is small, local deformation can be ignored; however, as the overall deformation increases, local deformation becomes more pronounced, and the influence of microstructure on local deformation becomes more significant.

[0117] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A loess microstructure evolution observation system based on in-situ micro-CT experiments, characterized in that, include: The consolidation box (1) has a barrel-shaped structure; The sample bottom fixing part (2) is placed inside the barrel-shaped consolidation box (1); The sample top fixing part (3) is placed at the opening of the barrel-shaped consolidation box (1); The ring cutter (4) is embedded at both ends in the sample bottom fixing part (2) and the sample top fixing part (3), respectively; A columnar first permeable stone (6) is movably embedded in the top fixing part (3) of the sample. The outer diameter of the first permeable stone (6) is the same as the inner diameter of the ring cutter (4) and can slide into the inside of the ring cutter (4). The second permeable stone (5) is located between the sample bottom fixing part (2) and the ring cutter (4), and the outer diameter of the second permeable stone (5) is equal to the outer diameter of the ring cutter (4); The load pressurization unit (7) is used to apply axial pressure to the loess sample in the ring cutter (4) through the barrel-shaped consolidation box (1) and the first permeable stone (6); A CT scanning unit (8) is arranged outside the barrel-shaped consolidation box (1); The sample bottom fixing part (2) includes a sample bottom fixing seat (201) and a plurality of claws (202) arranged in the same circle. The claws (202) are fixedly connected to the sample bottom fixing seat (201). A groove (203) is formed between two adjacent claws (202). The end of the ring cutter (4) and the second permeable stone (5) are locked between the plurality of claws (202). The claws (202) are provided with an arc surface. The arc surface fits against the ring cutter (4) and the second permeable stone (5). The second permeable stone (5) is located between the sample bottom fixing seat (201) and the ring cutter (4). The sample bottom fixing seat (201) is provided with a second permeable stone fixing groove (204), and the end of the second permeable stone (5) is embedded in the second permeable stone fixing groove (204); The sample top fixing part (3) is provided with a first permeable stone sliding hole (301), the first permeable stone (6) is embedded in the first permeable stone sliding hole (301), the sample top fixing part (3) is provided with a ring cutter limiting ring (302), the end of the ring cutter (4) is embedded in the inner hole of the ring cutter limiting ring (302), the ring cutter limiting ring (302) is coaxially arranged with the first permeable stone sliding hole (301), and the inner diameter of the first permeable stone sliding hole (301) is smaller than the hole diameter of the ring cutter limiting ring (302).

2. The loess microstructure evolution observation system based on in-situ micro-CT experiments according to claim 1, characterized in that, The barrel-shaped consolidation box (1) and the ring cutter (4) are both made of PEEK plastic or carbon fiber composite material with an X-ray transmittance greater than 90%. The inner diameter of the ring cutter (4) is 10 mm, the height of the ring cutter (4) is 10 mm, and the wall thickness of the ring cutter (4) is 1 mm.

3. The loess microstructure evolution observation system based on in-situ micro-CT experiments according to claim 1, characterized in that, The sample top fixing part (3) is provided with an annular protrusion (303), the sample top fixing part (3) is embedded in the opening of the consolidation box (1), the annular protrusion (303) is placed on the opening, and the outer diameter of the annular protrusion (303) is greater than or equal to the outer diameter of the consolidation box (1).

4. The loess microstructure evolution observation system based on in-situ micro-CT experiments according to claim 1, characterized in that, The load pressurization unit (7) includes a stage (701), on which a power loading unit (705) is provided. The power loading unit (705) is located between the consolidation box (1) and the stage (701). A disc (706) is provided between the power loading unit (705) and the consolidation box (1). The outer diameter of the disc (706) is equal to the outer diameter of the bottom of the consolidation box (1). The stage (701) is connected to a sample fixing pressurization part (703) by several connecting rods (702). A pressurization head (704) is provided on the sample fixing pressurization part (703). The pressurization head (704) is in contact with the first permeable stone (6). The pressurization head (704) is located on the side of the first permeable stone (6) away from the ring cutter (4). The sample fixing and pressurizing part (703) is provided with a plurality of first water filling holes (707), and the sample top fixing part (3) is provided with a plurality of second water filling holes (304). The first water filling holes (707) and the second water filling holes (304) correspond one-to-one in the axial direction of the consolidation box (1).

5. The loess microstructure evolution observation system based on in-situ micro-CT test according to claim 1, characterized in that, The CT scanning unit (8) includes an X-ray source (801) and an X-ray detector (802), which are located on both sides of the consolidation box (1).

6. The loess microstructure evolution observation system based on in-situ micro-CT test according to claim 1, characterized in that, It also includes a supplementary light (9) and a chassis support (11). The supplementary light (9) is located on top of the load pressurization unit (7). The load pressurization unit (7) and the CT scanning unit (8) are both arranged on the chassis support (11).

7. A method for observing the evolution of loess microstructure based on in-situ micro-CT experiments, based on the loess microstructure evolution observation system based on in-situ micro-CT experiments as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Loess samples were obtained by sampling loess using the ring cutter (4); The loess sample is installed between the bottom fixing part (2) and the top fixing part (3) of the sample along with the ring cutter (4); The loess soil sample was subjected to graded loading by the load pressurization unit (7) to carry out the loess consolidation-collapse test, and the CT scanning unit (8) was used to scan and obtain CT slices. The CT slices were reconstructed to obtain a three-dimensional model of the same area of ​​the loess soil sample. Based on the three-dimensional model, the particle-level parameters were quantitatively statistically analyzed to quantify the changes in particles and parameters. The loading force and loading displacement of the load-pressurizing unit (7) are recorded in real time, and the load-displacement curve of the loess soil sample during the consolidation and collapse process is obtained based on the loading force and loading displacement.

8. The method for observing the evolution of loess microstructure based on in-situ micro-CT experiments according to claim 7, characterized in that, The loess sampling via the ring cutter (4) includes: The ring cutter (4) is used to take samples from the original loess sample. During the soil sample preparation process, the cutting edge of the ring cutter (4) is pressed into the soil evenly with the cutting edge facing down until the cylinder of the ring cutter (4) is filled with soil sample. Use a soil cutting knife to cut open the soil sample around the ring cutter (4) and wipe the outer wall of the ring cutter (4) clean; The scanning is performed using a CT scanning unit (8). The scanning parameters are set as follows: voltage / power ≥80kV / 7W, resolution 1~1.5μm / pixel, 1000×1000×1000 voxels, and the scanning area is locked as the central area of ​​φ1~φ1.5mm×H1mm, where φ is the diameter of the cylinder and H represents the height of the cylinder.

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