A method and device for equivalent simplified triaxial creep shear test based on 3D printing

Abstract

The present invention relates to a method and device for a simplified triaxial creep shear test based on 3D printing, the method comprising the following steps: preparing an unconfined structure by 3D printing according to the size of a soil sample; calculating the corresponding shear stress of the soil sample and the corresponding counterweight weight; assembling the soil sample with the unconfined structure; placing the counterweight above the bearing top cover of the unconfined structure, and sequentially performing primary consolidation and secondary consolidation on the soil sample, wherein graded loading is adopted in the secondary consolidation; determining the deformation of the soil sample by the reading of a micrometer, and judging whether creep stability is achieved; recording the creep deformation of the soil sample according to the reading of the micrometer, and calculating the strain of the soil sample; removing the soil sample that has completed creep, and analyzing the creep microscopic mechanism of the soil sample. Compared with the prior art, the present invention has the advantages of being able to print and design according to the actual soil size, the unconfined structure being simple in structure and low in cost, and convenient replacement and disassembly of creep soil.

Description

Technical Field

[0001] The present invention relates to the research field of triaxial creep shear test, and in particular to a method and device for a triaxial creep shear test based on 3D printing equivalent simplified testing. Background Art

[0002] With the continuous development of urban underground space, coupled with the typical weak stratum characteristics of coastal areas, higher requirements are placed on construction methods. Under the action of long-term static loads, the creep phenomenon of soil has a great impact on the disturbance and settlement of surrounding buildings. For example, with regard to the cement reinforcement freezing method commonly used in coastal engineering construction, after the implementation of this method, the creep of soil under the coupling of cement reinforcement and freeze-thaw action is worthy of attention. The study of macroscopic strain and microscopic mechanism of soil creep requires the application of equivalent creep load in the early stage. Therefore, selecting a convenient and efficient method to equivalent the creep process of soil is of great significance to promote the exploration of soil macroscopic creep characteristics and microscopic mechanism.

[0003] In the field of soil mechanics, the GDS fully automatic triaxial testing instrument is an advanced instrument widely used in a large number of researches. It has accurate deformation control and high test accuracy. It can collect axial force and pore pressure data in real time during the test through built-in pore pressure sensors and load sensors. It has a good effect on studying the stress-strain law of soil samples under static loads.

[0004] However, in addition to the study of the macroscopic deformation of the soil, in order to clarify the microstructure and mechanism corresponding to the macroscopic characteristics under specific working conditions, it is often necessary to use microscopic research methods, such as SEM scanning electron microscopy, NMR nuclear magnetic resonance, etc. In this case, the use of triaxial testing instruments for full-stage and refined control will bring additional costs and inconveniences, especially for creep conditions with long duration.

[0005] Therefore, it is necessary to propose a method that can replace traditional advanced instruments with materials that are relatively easy to implement and restore, and to perform an equivalent test method for the triaxial creep shear stress state, so as to more efficiently and conveniently complete the working condition simulation work before exploring the creep characteristics and microscopic mechanisms of soil. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art that the use of triaxial testing instruments for full-stage and refined control will bring additional costs and inconveniences, and to provide a method and device for performing equivalent testing on triaxial creep shear stress states by replacing traditional advanced instruments with materials that are relatively easy to implement and restore.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] This scheme provides a method for equivalent simplified triaxial creep shear test based on 3D printing, including the following steps:

[0009] According to the size of the soil sample, the size of the test base, bearing top cover and shear stack ring in the unconfined structure is determined and prepared by 3D printing;

[0010] According to the actual overburden load of the soil, calculate the corresponding shear stress and the corresponding counterweight weight;

[0011] Install the soil sample on the test base, then install the load-bearing top cover and shear stack ring to complete the assembly of the unconfined shear device;

[0012] The counterweight is placed above the bearing cap to perform primary consolidation on the soil sample. After the primary consolidation of the soil sample is completed, the soil sample is loaded in stages according to the calculated counterweight, and secondary consolidation is performed on the soil sample until the counterweight is fully loaded;

[0013] Fix the micrometer on the top of the model box and place the probe of the micrometer on the top of the counterweight. Determine the deformation of the soil sample according to the reading of the micrometer and judge whether creep stability is reached;

[0014] The creep deformation of the soil sample is recorded according to the reading of the micrometer, and the strain of the soil sample is calculated; the soil sample that has completed creep is removed, and the creep microscopic mechanism of the soil sample is analyzed.

[0015] Furthermore, the specific assembly process of the unconfined structure and the soil sample includes the following steps:

[0016] Install the soil sample on the test base;

[0017] Put the latex film on the split mold downward to cover the test base to fix the soil sample on the test base;

[0018] Then install the bearing top cover on the upper end of the soil sample, and cover the bearing top cover upward with a latex film to complete the fixation of the bearing top cover and the soil sample, and remove the split mold;

[0019] Finally, the shear stack rings are put on the soil sample in sequence to complete the equipment assembly.

[0020] Furthermore, the counterweight includes a lightweight basin and a counterweight object with adjustable gravity. The lightweight basin is placed on the load-bearing top cover, and the counterweight object is placed in the lightweight basin to consolidate and drain the soil sample until the main consolidation of the soil sample is completed.

[0021] Furthermore, the specific process of the secondary consolidation of the soil sample includes:

[0022] After the main consolidation of the soil sample is completed, the counterweight object is taken out and the weight of the counterweight is graded according to the load corresponding to the calculated shear force;

[0023] Place a counterweight object of the first level weight in the lightweight basin, and observe the reading of the dial gauge. When the reading is stable, the creep of the soil sample is stable, and record the reading of the dial gauge.

[0024] Each time the soil sample creeps to a stable state, record the reading of the micrometer and add a counterweight object to the lightweight basin to increase the load of the soil sample to the next level;

[0025] Until the last level of counterweight objects is added, the secondary consolidation of the soil sample is completed.

[0026] Furthermore, the shear stack ring includes an upper circular ring, a middle circular ring and a lower circular ring, the upper circular ring surrounds the connection between the bearing top cover and the soil sample, the lower circular ring surrounds the connection between the soil sample and the test base, and the middle circular ring surrounds the outside of the soil sample.

[0027] Furthermore, after the soil sample completes the secondary consolidation, it is taken out from the unconfined structure, and the microscopic mechanism of creep of the soil sample is qualitatively and quantitatively analyzed through a scanning electron microscope test or a low-field nuclear magnetic resonance test.

[0028] The present invention also provides a device for a simplified triaxial creep shear test based on 3D printing, which is used to implement a method for a simplified triaxial creep shear test based on 3D printing. The device includes an unconfined structure, a counterweight, a displacement monitoring structure, and a data analysis system. The unconfined structure includes a test base, a load-bearing top cover, and a shear stack ring.

[0029] The test base is used for placing and assisting in fixing the soil sample, the bearing top cover is arranged at the top of the soil sample, the shear stack is arranged on the outside of the soil sample, and is used to limit the radial deformation of the soil sample, the counterweight is arranged at the upper end of the bearing top cover, and the weight is adjustable, and is used to provide the main consolidation pressure and the secondary consolidation pressure for the soil sample, the bearing top cover is used to transfer the load, the displacement monitoring structure is used to measure the deformation of the soil sample, and the data analysis system is used to analyze the strain of the soil sample during the creep process and the microstructural changes after the creep according to the detection results of the displacement monitoring structure.

[0030] Furthermore, the unconfined structure is prepared by 3D printing, the test base is a cylindrical combination structure, the bearing top cover is a cylindrical structure, the shear stack ring is composed of multiple stacked rings, the ends of the test base and the bearing top cover that are in contact with the soil sample are matched with the diameter of the soil sample, and the inner diameter ratio of the shear stack ring is greater than the diameter of the soil sample.

[0031] Furthermore, the shear stack ring includes an upper circular ring, a middle circular ring and a lower circular ring, the upper circular ring surrounds the connection between the bearing top cover and the soil sample, the lower circular ring surrounds the connection between the soil sample and the test base, and the middle circular ring surrounds the outside of the soil sample.

[0032] Furthermore, the counterweight includes a lightweight storage basin and a counterweight object with adjustable gravity. The lightweight storage basin is fixed to the upper end of the load-bearing top cover. There are multiple counterweight objects, each of which has the same mass and is used to adjust the weight of the counterweight.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) This scheme can consider the influence of factors such as overburden at different depths and specimens of different sizes on triaxial creep shear tests, and provide certain technical support for studying the macroscopic strain and microscopic mechanism of soil under various working conditions under long-term creep. It can also assist in determining the improvement effect of a specific construction method on the creep characteristics of soil, and provide certain reference value for the improvement of construction methods and creep prevention and control in underground engineering construction in coastal cities.

[0035] (2) The device provided by the present invention has a simple overall structure, low cost, good repeatability and is easy to replace the test site. By using the device, the test can be completed quickly and conveniently. In addition, the unconfined shear device in the device can be flexibly designed and adjusted according to the size of the sample, effectively avoiding the problem of high cost and difficulty of replacing parts in traditional advanced instruments.

[0036] (3) The shear stacking rings set in this scheme can be flexibly printed according to the volume of the soil sample. The overlapping structure of the multi-layer rings is easy to install before the experiment begins. During the creep process of the soil sample, there will be no radial limitation on the soil sample, that is, there will be no interference with the creep of the soil sample, thus ensuring the accuracy of the creep results of the soil sample and having practical significance. On the other hand, after the creep is over, the shear stacking rings can be removed to obtain a complete soil sample after creep, which is convenient for the subsequent observation of the microscopic mechanism of the creep soil sample. The structure is reliable and practical.

[0037] (4) In the existing field of soil mechanics, the study of the microscopic characteristics of soil after deformation usually adopts traditional test methods, such as direct shear test or triaxial shear test, which require more variable control and preparation. However, for the study of microscopic mechanism, few people consider using simplified methods to complete the initial working condition simulation. The test device and method provided by this scheme can help shift the focus of work to microscopic mechanism analysis and subsequent prevention and control, effectively revealing the creep microscopic mechanism of soil under different working conditions and further research. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1A front cross-sectional view of a soil sample before creep in the unconfined shear structure provided by the present invention;

[0039] Figure 2 A front cross-sectional view of a soil sample after creep in the unconfined shear structure provided by the present invention;

[0040] Figure 3 A schematic diagram of the structure of the test base provided by the present invention;

[0041] Figure 4 A schematic diagram of the structure of the load-bearing top cover provided by the present invention;

[0042] Figure 5 A schematic diagram of the structure of the shear stack ring provided by the present invention;

[0043] Figure 6 A schematic diagram of the structure of the unconfined shear structure provided by the present invention;

[0044] In the figure: 1. test base, 2. load-bearing top cover, 3. shear stack ring, 4. latex membrane, 5. soil sample. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0046] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0048] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0049] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0050] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0051] Example 1

[0052] This embodiment provides a method for a simplified triaxial creep shear test based on 3D printing, comprising the following steps:

[0053] According to the size of the soil sample, the size of the test base, bearing top cover and shear stack ring in the unconfined structure is determined and prepared by 3D printing;

[0054] According to the actual overburden load of the soil, calculate the corresponding shear stress and the corresponding counterweight weight;

[0055] Install the soil sample on the test base, then install the load-bearing top cover and shear stack ring to complete the assembly of the unconfined shear device;

[0056] The counterweight is placed above the bearing cap to perform primary consolidation on the soil sample. After the primary consolidation of the soil sample is completed, the soil sample is loaded in stages according to the calculated counterweight, and secondary consolidation is performed on the soil sample until the counterweight is fully loaded;

[0057] Fix the micrometer on the top of the model box and place the probe of the micrometer on the top of the counterweight. Determine the deformation of the soil sample according to the reading of the micrometer and judge whether creep stability is reached;

[0058] The creep deformation of the soil sample is recorded according to the reading of the micrometer, and the strain of the soil sample is calculated; the soil sample that has completed creep is removed, and the creep microscopic mechanism of the soil sample is analyzed.

[0059] By considering the influence of factors such as overlying soil at different depths and specimens of different sizes on the triaxial creep shear test, it provides certain technical support for studying the macroscopic strain and microscopic mechanism of soil under long-term creep under various working conditions. It can also assist in judging the improvement effect of specific construction methods on soil creep characteristics, and provides certain reference value for the improvement of construction methods and creep prevention and control in underground engineering construction in coastal cities.

[0060] The specific assembly process of the unconfined structure and soil specimens includes the following steps:

[0061] Install the soil sample on the test base;

[0062] Put the latex film on the split mold downward to cover the test base to fix the soil sample on the test base;

[0063] Then install the bearing top cover on the upper end of the soil sample, and cover the bearing top cover upward with a latex film to complete the fixation of the bearing top cover and the soil sample, and remove the split mold;

[0064] Finally, the shear stack rings are put on the soil sample in sequence to complete the equipment assembly.

[0065] In a preferred embodiment, the counterweight includes a lightweight basin and a counterweight object with adjustable gravity. The lightweight basin is placed on the load-bearing top cover, and the counterweight object is then placed in the lightweight basin to consolidate and drain the soil sample until the main consolidation of the soil sample is completed.

[0066] Specifically, the specific process of secondary consolidation of soil samples includes:

[0067] After the main consolidation of the soil sample is completed, the counterweight object is taken out and the weight of the counterweight is graded according to the load corresponding to the calculated shear force;

[0068] Place a counterweight object of the first level weight in the lightweight basin, and observe the reading of the dial gauge. When the reading is stable, the creep of the soil sample is stable, and record the reading of the dial gauge.

[0069] Each time the soil sample creeps to a stable state, record the reading of the micrometer and add a counterweight object to the lightweight basin to increase the load of the soil sample to the next level;

[0070] Until the last level of counterweight objects is added, the secondary consolidation of the soil sample is completed.

[0071] Considering that the bearing capacity of the soil sample has not been confirmed, if all the weights are added to the soil sample at once, the soil sample may not be able to bear the weight and be destroyed. Therefore, the soil sample is graded and weighted in stages using a graded loading method to ensure the smooth progress of the experiment and the acquisition of the final complete creep soil sample, which is convenient for the subsequent microscopic mechanism analysis of the creep soil sample.

[0072] The shear stack ring includes an upper circular ring, a middle circular ring and a lower circular ring. The upper circular ring surrounds the connection between the bearing top cover and the soil sample, the lower circular ring surrounds the connection between the soil sample and the test base, and the middle circular ring surrounds the outside of the soil sample.

[0073] Furthermore, after the soil sample completes the secondary consolidation, it is taken out from the unconfined structure and the microscopic mechanism of creep of the soil sample is qualitatively and quantitatively analyzed through scanning electron microscopy test or low-field nuclear magnetic resonance test.

[0074] In combination with the above preferred implementations, this embodiment provides a test method for simulating the creep deformation of freeze-thaw cement reinforced soil under long-term load, comprising the following steps:

[0075] S1. Design the test base according to the sample size;

[0076] S2. Design the load-bearing top cover according to the sample size;

[0077] S3. Design the shear stack according to the sample size;

[0078] S4. According to the actual engineering background, the cover layer is determined to be soft clay in the Shanghai area. The overburden load is calculated according to the soil weight and construction depth, and the corresponding shear stress and the corresponding counterweight weight are calculated. In order to prevent the one-time loading sample from being unable to withstand damage, a graded loading method is used to design graded counterweights;

[0079] S5. Debug the unconfined shear equipment. First, install the freeze-thaw cement soil sample on the test base, then cover the test base with the latex film on the split mold to fix the sample, then install the load-bearing top cover on the soil sample and fix it with the latex film, and remove the split mold. Then carefully cover the shear stack rings on the freeze-thaw cement soil sample in turn;

[0080] S6. Debug the loading equipment. First, place the counterweight device stably on the top cover to consolidate and drain the soil sample. After the main consolidation of the soil sample is completed, perform secondary consolidation and load in sequence according to the calculated graded counterweights. After each level of creep is stable, apply the next level of load until all are completed.

[0081] S7. Debug the displacement monitoring equipment, fix the dial gauge on the top of the model box, place the dial gauge probe on the top of the counterweight device, determine the deformation amount according to the dial gauge reading, and judge whether creep stability is achieved;

[0082] S8. Post-data processing and analysis: record the creep deformation of the sample by reading the thousandths, and then calculate the strain. After the creep is completed, carefully remove the device and conduct further microscopic testing and analysis on the sample.

[0083] In the existing field of soil mechanics, the study of the microscopic characteristics of soil after deformation usually adopts traditional test methods, such as direct shear test and triaxial shear test, which requires more variable control and preparation. However, for the study of microscopic mechanism, few people consider using simplified methods to complete the simulation of preliminary working conditions. The test device and method provided by this scheme can help shift the focus of work to microscopic mechanism analysis and subsequent prevention and control, effectively revealing the creep microscopic mechanism of soil under different working conditions and further research.

[0084] like Figure 1 and Figure 2 As shown, this embodiment also provides a device for a simplified triaxial creep shear test based on 3D printing, which is used to implement the above-mentioned method for a simplified triaxial creep shear test based on 3D printing. The device includes an unconfined structure, a counterweight, a displacement monitoring structure and a data analysis system. The unconfined structure includes a test base 1, a load-bearing top cover 2 and a shear stack ring 3;

[0085] The test base 1 is used to place and assist in fixing the soil sample 5, the bearing cover 2 is placed on the top of the soil sample 5, the shear stack ring 3 is sleeved on the outside of the soil sample 5, and is used to limit the radial deformation of the soil sample 5. The counterweight is placed on the upper end of the bearing cover 2, and the weight is adjustable, and is used to provide the main consolidation pressure and the secondary consolidation pressure for the soil sample 5. The bearing cover 2 is used to transfer the load, the displacement monitoring structure is used to measure the deformation of the soil sample 5, and the data analysis system is used to analyze the strain of the soil sample 5 during the creep process and the microstructural changes after creep according to the detection results of the displacement monitoring structure.

[0086] Specifically, Figures 3 to 6 As shown, the unconfined structure is prepared by 3D printing, the test base 1 is a cylindrical combination structure, the bearing top cover 2 is a cylindrical structure, the shear stack ring 3 is composed of multiple stacked rings, and the ends of the test base 1 and the bearing top cover 2 that are in contact with the soil sample 5 are matched with the diameter of the soil sample 5, and the inner diameter ratio of the shear stack ring 3 is greater than the diameter of the soil sample 5.

[0087] In a preferred embodiment, the shear stack ring 3 includes an upper circular ring, a middle circular ring and a lower circular ring, the upper circular ring surrounds the connection between the bearing top cover 2 and the soil sample 5, the lower circular ring surrounds the connection between the soil sample 5 and the test base 1, and the middle circular ring surrounds the outside of the soil sample 5.

[0088] The shear stack ring 3 is designed according to the actual soil sample size through three-dimensional drawing software and is composed of dense circular rings. The upper and lower circular rings are wider and can wrap the connection between the soil sample 5 and the test base 1 and the bearing top cover 2 to prevent the sample from lateral displacement. The middle circular ring is designed to be denser to limit the radial expansion of the sample and avoid lateral limitation.

[0089] Among them, the counterweight includes a lightweight storage basin and a counterweight object with adjustable gravity. The lightweight storage basin is fixed to the upper end of the load-bearing top cover 2. There are multiple counterweight objects, and the mass of each counterweight object is the same, which is used to adjust the weight of the counterweight.

[0090] In combination with the above preferred implementation, this embodiment provides a test device, based on the above simplified design method of the equivalent triaxial creep shear test based on 3D printing technology, such as Figures 1 to 6 As shown, including:

[0091] like Figure 3 As shown, the test base is made by 3D printing. The strength of the 3D printing material used is sufficient to bear the weight. The cylinder in the upper part of the base is consistent with the diameter of the cylindrical specimen and is used to place and assist in fixing the test soil.

[0092] like Figure 4 As shown, the bearing top cover 2 is the same size as the cylindrical body of the upper half of the test base, and the latex membrane 4 is put on it to assist in fixing the test soil and to play a role in transmitting force;

[0093] like Figure 5 and Figure 6 As shown, the shear stack ring 3 is designed by 3D printing according to the actual soil sample size and is composed of dense circular rings. The bottom and top circular rings are wider to prevent the sample from lateral displacement; the middle circular ring is designed to be denser to limit the radial expansion of the sample, but does not produce lateral limitation;

[0094] The loading device is used to simulate the actual soil overburden weight at a certain depth, including the primary consolidation pressure and the secondary consolidation pressure. A lightweight plastic basin is selected to hold a stable weight to be used for equivalent soil overburden pressure. After completing the first level of loading, a second level of weight is placed in the plastic basin to complete all loading in sequence.

[0095] The displacement detection equipment is used to monitor whether each level of creep deformation is stable. The micrometer is fixed on the adjacent iron structure. After ensuring stability, the probe is adjusted downward to touch the top of the loading device to measure the deformation of the lower structure.

[0096] The data analysis system includes data processing and image processing software, etc. It calculates the strain during the creep process through the micrometer readings, and further removes the freeze-thaw cement soil samples that have completed creep to conduct scanning electron microscopy tests, low-field nuclear magnetic resonance tests, etc., to qualitatively and quantitatively analyze the microscopic mechanism of freeze-thaw cement soil creep.

[0097] The device has a simple overall structure, low cost, good repeatability and is easy to replace the test site. By using this device, the test can be completed quickly and conveniently. In addition, the unconfined shear device in this device can be flexibly designed and adjusted according to the size of the sample, effectively avoiding the high cost and difficulty of replacing parts in traditional advanced instruments.

[0098] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for equivalent simplified triaxial creep shear test based on 3D printing, characterized in that: The following steps are involved: According to the size of the soil sample, the size of the test base, bearing top cover and shear stack ring in the unconfined structure is determined and prepared by 3D printing; According to the actual overburden load of the soil, calculate the corresponding shear stress and the corresponding counterweight weight; Install the soil sample on the test base, then install the load-bearing top cover and shear stack ring to complete the assembly of the unconfined shear device; The counterweight is placed above the bearing cap to perform primary consolidation on the soil sample. After the primary consolidation of the soil sample is completed, the soil sample is loaded in stages according to the calculated counterweight, and secondary consolidation is performed on the soil sample until the counterweight is fully loaded; Fix the micrometer on the top of the model box and place the probe of the micrometer on the top of the counterweight. Determine the deformation of the soil sample according to the reading of the micrometer and judge whether creep stability is reached; The creep deformation of the soil sample is recorded according to the reading of the micrometer, and the strain of the soil sample is calculated; the soil sample that has completed creep is removed, and the creep microscopic mechanism of the soil sample is analyzed; The shear stack ring is composed of a plurality of stacked circular rings; The counterweight includes a lightweight basin and a counterweight object with adjustable gravity. The lightweight basin is placed on the load-bearing top cover, and the counterweight object is placed in the lightweight basin to consolidate and drain the soil sample until the main consolidation of the soil sample is completed; The specific process of the secondary consolidation of the soil sample includes: After the main consolidation of the soil sample is completed, the counterweight object is taken out and the weight of the counterweight is graded according to the load corresponding to the calculated shear force; Place a counterweight object of the first level weight in the lightweight basin, and observe the reading of the dial gauge. When the reading is stable, the creep of the soil sample is stable, and record the reading of the dial gauge. Each time the soil sample creeps to a stable state, record the reading of the micrometer and add a counterweight object to the lightweight basin to increase the load of the soil sample to the next level; Until the last level of counterweight objects is added, the secondary consolidation of the soil sample is completed.

2. The method of claim 1, wherein: The specific assembly process of the unconfined structure and the soil sample includes the following steps: Install the soil sample on the test base; Put the latex film on the split mold downward to cover the test base to fix the soil sample on the test base; Then install the bearing top cover on the upper end of the soil sample, and cover the bearing top cover upward with a latex film to complete the fixation of the bearing top cover and the soil sample, and remove the split mold; Finally, the shear stack rings are put on the soil sample in sequence to complete the equipment assembly.

3. The method of claim 1, wherein: The shear stack ring includes an upper circular ring, a middle circular ring and a lower circular ring. The upper circular ring surrounds the connection between the bearing top cover and the soil sample, the lower circular ring surrounds the connection between the soil sample and the test base, and the middle circular ring surrounds the outside of the soil sample.

4. The method of claim 1, wherein: After the soil sample completes the secondary consolidation, it is taken out from the unconfined structure, and the microscopic mechanism of creep of the soil sample is qualitatively and quantitatively analyzed through a scanning electron microscope test or a low-field nuclear magnetic resonance test.

5. A device for performing a simplified triaxial creep shear test based on 3D printing, used to implement a method for performing a simplified triaxial creep shear test based on 3D printing according to any one of claims 1 to 4, characterized in that: The device comprises an unconfined structure, a counterweight, a displacement monitoring structure and a data analysis system, wherein the unconfined structure comprises a test base, a load-bearing top cover and a shear stack ring; The test base is used for placing and assisting in fixing the soil sample, the bearing top cover is arranged at the top of the soil sample, the shear stack is arranged on the outside of the soil sample, and is used to limit the radial deformation of the soil sample, the counterweight is arranged at the upper end of the bearing top cover, and the weight is adjustable, and is used to provide the main consolidation pressure and the secondary consolidation pressure for the soil sample, the bearing top cover is used to transfer the load, the displacement monitoring structure is used to measure the deformation of the soil sample, and the data analysis system is used to analyze the strain of the soil sample during the creep process and the microstructure changes after the creep according to the detection results of the displacement monitoring structure.

6. The device according to claim 5, characterized in that The unconfined structure is prepared by 3D printing, the test base is a cylindrical combination structure, the bearing top cover is a cylindrical structure, the ends of the test base and the bearing top cover that contact the soil sample are matched with the diameter of the soil sample, and the inner diameter ratio of the shear stack is greater than the diameter of the soil sample.

7. The device according to claim 5, characterized in that The shear stack ring includes an upper circular ring, a middle circular ring and a lower circular ring. The upper circular ring surrounds the connection between the bearing top cover and the soil sample, the lower circular ring surrounds the connection between the soil sample and the test base, and the middle circular ring surrounds the outside of the soil sample.

8. The device according to claim 5, characterized in that The counterweight includes a lightweight storage basin and a counterweight object with adjustable gravity. The lightweight storage basin is fixed to the upper end of the load-bearing top cover. There are multiple counterweight objects, each of which has the same mass and is used to adjust the weight of the counterweight.

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