Tangentially frozen visible large ice-soil-structure interface shear test method

Abstract

The invention discloses a tangential freezing visible large ice-soil-structure interface shear test method, and relates to the field of geotechnical engineering, and the method comprises the following steps: preparing a soil-structure interface; using a circulating pump and a freezing cavity arranged on one side of the upper shearing box to tangentially freeze the to-be-sheared soil sample under a preset freezing condition to form an ice-soil-structure interface; applying a preset normal load, applying a shearing force at the same time, and carrying out a shearing test on the ice-soil-structure interface at a preset shearing rate; meanwhile, acquiring a side image of the soil sample to be sheared in the freezing and shearing processes based on a DIC measurement system to obtain displacement deformation characteristics and fracture development characteristics of the soil sample to be sheared; and combining the shear curve to obtain the shear characteristic of the ice-soil-structure interface. According to the method, the freezing condition of the soil-structure interface in real cold region engineering can be more accurately simulated, and the fracture development condition of interface ice on a mesoscopic level can be observed, so that the shearing characteristic of the ice-soil-structure interface can be deeply known.

Description

Technical Field

[0001] The present application relates to the field of geotechnical engineering technology, and in particular to a tangentially frozen visible large-scale ice-soil-structure interface shear test method. Background Art

[0002] With the increase of engineering construction in polar, high altitude, high latitude and other cold regions, engineering structures often face severe low temperature environment and complex soil-structure interaction, and the soil-structure interface affects load transfer, stress distribution and deformation characteristics, which is very important for the safety and stability of engineering structures. Therefore, further in-depth research is needed on the shear characteristics of the ice-soil-structure interface in cold regions to explore the shear performance of the ice-soil-structure interface and provide strong support for cold region engineering construction.

[0003] At present, shear tests related to cold-region interfaces mainly use a water bath around the interface to freeze soil samples from the bottom of the interface upward (normal freezing). However, this method is quite different from the actual low-temperature freezing effect of cold-region interfaces. In particular, the above conventional freezing method greatly weakens the ice bonding force generated by the movement of the freezing front and the influence of the arrangement of ice lenses on the interface. The cold-region soil-structure interfaces that need to be studied urgently are mostly the foundation side surfaces, where the natural freezing direction is parallel to the interface (tangential freezing), and the ice lenses are arranged in layers perpendicular to the interface. Different arrangements lead to different ice contents on the interface, and the impact on the shear performance of the interface cannot be ignored. In addition, existing shear test systems often lack visualization means, especially for the formation and evolution of interfacial ice, making it difficult to intuitively observe the deformation and destruction process of the interface.

[0004] Therefore, there is an urgent need for a visual large-scale interface shear test method for tangential freezing that can accurately simulate the actual freezing conditions of the ice-soil-structure interface. Summary of the invention

[0005] The purpose of this application is to provide a large-scale visible ice-soil-structure interface shear test method with tangential freezing, which can more accurately simulate the freezing conditions of the soil-structure interface in real cold region projects and obtain the relevant shear properties of the ice-soil-structure interface.

[0006] To achieve the above objectives, this application provides the following solutions: The present application provides a large-scale visible ice-soil-structure interface shear test method for tangential freezing, which is applied to a large-scale ice-soil-structure interface shear test instrument. The large-scale ice-soil-structure interface shear test instrument specifically includes: an upper shear box, a lower shear box, a circulation pump, a low-temperature freezing chamber and a DIC (Digital Image Correlation) measurement system; wherein the upper shear box is sleeved in the lower shear box; the circulation pump is connected to the freezing chamber through a pipeline, and the freezing chamber is located on the side of the upper shear box; The tangentially frozen visible large-scale ice-soil-structure interface shear test method specifically includes: According to the test purpose, the structural material is placed in the lower shear box, and the soil sample to be sheared is placed in the upper shear box, so that the lower surface of the soil sample to be sheared is in direct contact with the structural material in the lower shear box, forming a soil-structure interface; The circulating fluid in the pipeline is circulated and cooled by a circulating pump, and the freezing chamber on one side of the upper shear box is used to tangentially freeze the soil sample to be sheared under preset freezing conditions to form an ice-soil-structure interface; the freezing conditions include freezing temperature and freezing time; Applying a preset normal load to the soil sample to be sheared after tangential freezing, and applying a shear force at the same time, and performing a shear test on the ice-soil-structure interface at a preset shear rate; The side images of the soil sample to be sheared during the freezing and shearing processes are obtained based on the DIC measurement system, and the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared are obtained using the DIC measurement system; the shear stress and shear displacement characteristics are obtained in real time, and a shear curve is drawn with the shear stress as the ordinate and the shear displacement characteristics as the abscissa; The data analysis method is used to analyze the shear curves under different test conditions, the freezing process and the side images of the soil samples to be sheared during the shear process, and the shear characteristics of the ice-soil-structure interface under tangential freezing conditions are obtained; the shear characteristics include shear strength, displacement deformation characteristics and crack development characteristics.

[0007] According to the specific embodiments provided in this application, this application has the following technical effects: The present application provides a large-scale visible ice-soil-structure interface shear test method of tangential freezing. By using a circulating pump and a freezing chamber arranged on one side of the upper shear box to perform tangential freezing of the soil sample to be sheared under preset freezing conditions, the freezing state of the soil-structure interface in real cold region engineering can be accurately simulated, and the influence of the ice lens arranged perpendicular to the interface formed by tangential freezing on the shear characteristics of the ice-soil-structure interface can be considered, and the shear mechanical behavior of the ice-soil-structure interface can be further revealed. At the same time, by obtaining the side image of the soil sample to be sheared during freezing and shearing based on the DIC measurement system, the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared are obtained by DIC technology analysis, and the shear stress and shear displacement characteristics are obtained in real time, the shear curve is drawn, and data analysis is performed, which solves the problem that the traditional method is difficult to intuitively display the crack development of the ice-soil-structure interface and accurately analyze the shear characteristics of the ice-soil-structure interface. The present application can provide a shear test method for the ice-soil-structure interface that is more in line with the real situation in cold regions, which has important scientific value and practical significance for ensuring the stable construction and long-term safe operation of infrastructure in cold regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0009] Figure 1 A schematic flow chart of a tangentially frozen visible large-scale ice-soil-structure interface shear test method provided in one embodiment of the present application.

[0010] Figure 2 A structural front view of a large ice-soil-structure interface shear testing instrument provided in one embodiment of the present application.

[0011] Figure markings: 1-circulation pump, 2-first pipeline, 3-second pipeline, 4-freezing chamber, 5-first loading device, 6-upper shear box, 7-lower shear box, 8-plexiglass visual area, 9-temperature control layer, 10-marking point, 11-water replenishing device, 12-second loading device. DETAILED DESCRIPTION

[0012] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0013] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0014] In an exemplary embodiment, a tangentially frozen visible large-scale ice-soil-structure interface shear test method is provided, wherein the tangentially frozen visible large-scale ice-soil-structure interface shear test method is applied to a large-scale ice-soil-structure interface shear tester, wherein the size of the large-scale ice-soil-structure interface shear tester ranges from a dozen centimeters to several tens of centimeters, such as Figure 2 As shown, it specifically includes: an upper shear box 6, a lower shear box 7, a circulating pump 1, a freezing chamber 4 and a DIC measurement system; wherein, the upper shear box 6 is internally sleeved in the lower shear box 7; the circulating pump 1 is connected to the freezing chamber 4 through a pipeline, and the freezing chamber 4 is located on the side of the upper shear box 6.

[0015] As an optional embodiment, the large ice-soil-structure interface shear tester also includes a first loading device 5 and a second loading device 12. The pipeline includes a first pipeline 2 and a second pipeline 3. The first loading device 5 is located above the upper shear box 6, and is used to apply a preset normal load; the second loading device 12 is directly connected to the lower shear box 7 and is located on the side of the lower shear box 7 perpendicular to the direction of the preset normal load; the freezing chamber 4 is located on the other side of the upper shear box 6 perpendicular to the direction of the preset normal load. The first loading device 5 is located above the upper shear box 6, and contacts the soil sample to be sheared through the loading plate, and is used to apply a preset normal load above the soil sample to be sheared. The first loading device 5 is a constant normal stress loading head, which provides a constant normal load for the soil sample to be sheared.

[0016] As an optional implementation, the large-scale ice-soil-structure interface shear testing instrument also includes a temperature measuring device and a water replenishing device 11.

[0017] The temperature measuring device includes multiple temperature sensors, which can use thermocouples, optical fibers, etc. A temperature measuring hole is opened on the side wall of the upper shear box 6. The temperature sensor is inserted into the test soil sample through the temperature measuring hole to obtain the temperature change pattern of different positions of the soil sample over time during the test.

[0018] The water replenishing device 11 is located in the lower shear box 7, and partially fills the lower shear box 7 with water. The interface is replenished with water by means of a water tank, simulating an open system state with external water replenishment in real situations.

[0019] As an optional implementation, the DIC measurement system in the large ice-soil-structure interface shear tester includes a high-precision industrial camera and a marking point 10 on the test soil sample. The image of the soil sample in the visible area of ​​the upper shear box 6 is collected by the high-precision industrial camera, and the digital image correlation method is used for data processing. The plane displacement changes of the soil samples in different areas of the upper shear box 6 are calculated according to the images at different times. The DIC method can capture soil displacement information with high spatial and temporal resolution without contacting the soil sample, avoiding the interference that traditional contact measurement may cause to the soil structure, and ensuring that the experimental conditions are closer to the actual state. Among them, the temperature or water replenishment state of different areas at different times is different. In general, the temperature will be lower near the cold source, and the temperature will gradually become higher as the distance from the cold source increases. At the same time, due to the decrease in temperature, the water in the soil sample to be sheared freezes, and the water in the unfrozen area of ​​the soil sample to be sheared will migrate toward the frozen area.

[0020] The visual large-scale ice-soil-structure interface shear test method for tangential freezing, such as Figure 1 As shown, specifically including: Step 101, according to the test purpose, the structural material is placed in the lower shear box 7, and the soil sample to be sheared is placed in the upper shear box, so that the soil sample to be sheared is in direct contact with the structural material in the lower shear box 7 on the lower surface of the upper shear box 6, forming a soil-structure interface. The structural material is used to simulate different interface conditions in actual engineering.

[0021] Step 102, circulating the circulating fluid in the pipeline to cool it down by circulating pump 1, and freezing chamber 4 tangentially freezes the soil sample to be sheared under preset freezing conditions to form an ice-soil-structure interface; the freezing conditions include freezing temperature and freezing time.

[0022] Step 103, applying a preset normal load to the soil sample to be sheared after tangential freezing, and applying a shear force, and performing a shear test on the ice-soil-structure interface at a preset shear rate. The preset normal load is determined according to the in-situ burial depth of the soil sample to be sheared; the preset shear rate is determined according to relevant specifications and literature.

[0023] Step 104, based on the DIC measurement system, a side image of the soil sample to be sheared during the freezing process and the shearing process is obtained, and the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared are obtained by using the DIC measurement system; and the shear stress and shear displacement characteristics are obtained in real time, and a shear curve is drawn with the shear stress as the ordinate and the shear displacement characteristics as the abscissa. The DIC measurement system detects the freezing front development rate and the crack development dynamic field of the soil sample to be sheared during the freezing and shearing process.

[0024] Step 105, using a data analysis method to analyze the shear curves under different test conditions, the freezing process, and the side images of the soil sample to be sheared during the shear process, to obtain the shear characteristics of the ice-soil-structure interface under tangential freezing conditions; the shear characteristics include shear strength, displacement deformation characteristics, and crack development characteristics.

[0025] By implementing the above steps 101 to 105, the present application can accurately simulate the shear behavior of the ice-soil-structure interface in actual engineering, especially the complex characteristics under tangential freezing conditions. In addition, the use of a DIC measurement system for real-time image capture and analysis further enhances the visualization and quantification capabilities of the experiment, which helps to gain a deeper understanding of the shear mechanism of the ice-soil-structure interface.

[0026] In another embodiment of the present application, the upper shear box 6 adopts a rectangular parallelepiped structure, which is surrounded by double-layer organic glass and has a temperature control layer 9 inside. The temperature control layer 9 is not only used to control the temperature boundary of the soil sample to be sheared, but also provides a defrosting function for the visible area. The freezing chamber 4 is arranged on one side of the upper shear box 6, and the temperature required for the test is provided by the circulating pump 1. The transparent organic glass part of the upper shear box 6 also provides a visible area, which is convenient for observing the changes of the soil sample to be sheared during the test.

[0027] Before the test begins, the structural material (such as concrete, steel plate, etc.) is placed in the lower shear box 7, and lubricant is applied to the inner wall of the upper shear box 6 to reduce the boundary effect caused by friction. The soil sample to be sheared is placed in the upper shear box 6, and the marking points 10 are evenly arranged to facilitate the subsequent displacement deformation measurement. In this embodiment, the marking points 10 are evenly distributed colored sand. It is worth noting that for soil properties such as sand with obvious particles, no marking points are required; for soil properties such as clay with unclear particles, marking points 10 need to be arranged to facilitate the subsequent displacement measurement based on DIC technology.

[0028] During the test, the water replenishment device 11 is used to simulate the actual open system, and the circulation pump 1 is started to transport the circulating medium to the freezing chamber 4. After the circulating medium is cooled by the circulation pump 1, it flows into the freezing chamber 4 through the second pipe 3, tangentially freezes the soil sample to be sheared in the upper shear box 6, and then flows out from the first pipe 2 back to the circulation pump 1 to form a cycle. At the same time, the first loading device 5 is slowly lowered to just contact the soil sample to be sheared. After applying a predetermined normal load, the sample is sheared at a constant shear rate through the second loading device 12 to simulate the shear force process of the ice-soil-structure interface. During this period, the temperature changes at different positions inside the soil sample are monitored in real time by a temperature sensor, and the surface image of the soil sample is collected using a high-precision industrial camera.

[0029] The DIC technology is used to analyze the image sequence, and the results of the temperature measurement device, the water replenishment device 11 and the DIC measurement device are summarized and analyzed. The ice lens evolution process during the freezing shear of the ice-soil-structure interface and the freezing shear characteristics of the ice-soil-structure interface that conform to actual working conditions are analyzed together with the regional temperature, displacement, stress and other data along the tangential freezing direction of the soil-structure interface. The results obtained can provide great help for actual engineering.

[0030] This application has the following beneficial effects: (1) The test soil samples are tangentially frozen using a circulating pump and a low-temperature freezing chamber located on one side of the upper shear box, which is more consistent with the freezing conditions of the actual soil-structure interface in cold region projects.

[0031] (2) A temperature control layer is set around the upper shear box, which can well control the test temperature boundary conditions; at the same time, the water replenishing device 11 replenishes water to the interface by replenishing water through a water tank, simulating an open freezing system under real conditions.

[0032] (3) A high-precision industrial camera is used to photograph the marked points on the soil sample to be sheared through the visible area. The photos are analyzed to obtain the development of cracks in the evolution of the ice lens at the mesoscopic level. This is a non-contact measurement with fast measurement speed, high accuracy and strong anti-interference ability.

[0033] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0034] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing related hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods.

[0035] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0036] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A tangentially frozen visible large-scale ice-soil-structure interface shear test method, characterized in that: The tangentially frozen visible large-scale ice-soil-structure interface shear test method is applied to a large-scale ice-soil-structure interface shear test instrument, which specifically includes: an upper shear box, a lower shear box, a circulation pump, a freezing chamber and a DIC measurement system; wherein the upper shear box is sleeved in the lower shear box; the circulation pump is connected to the freezing chamber through a pipeline, and the freezing chamber is located on the side of the upper shear box; The tangentially frozen visible large-scale ice-soil-structure interface shear test method specifically includes: According to the test purpose, the structural material is placed in the lower shear box, and the soil sample to be sheared is placed in the upper shear box, so that the lower surface of the soil sample to be sheared is in direct contact with the structural material in the lower shear box, forming a soil-structure interface; The circulating fluid in the pipeline is circulated and cooled by a circulating pump, and the freezing chamber on one side of the upper shear box is used to tangentially freeze the soil sample to be sheared under preset freezing conditions to form an ice-soil-structure interface; the freezing conditions include freezing temperature and freezing time; Applying a preset normal load to the soil sample to be sheared after tangential freezing, and applying a shear force at the same time, and performing a shear test on the ice-soil-structure interface at a preset shear rate; The side images of the soil sample to be sheared during the freezing and shearing processes are obtained based on the DIC measurement system, and the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared are obtained using the DIC measurement system; the shear stress and shear displacement characteristics are obtained in real time, and a shear curve is drawn with the shear stress as the ordinate and the shear displacement characteristics as the abscissa; The data analysis method is used to analyze the shear curves under different test conditions, the freezing process and the side images of the soil samples to be sheared during the shear process, and the shear characteristics of the ice-soil-structure interface under tangential freezing conditions are obtained; the shear characteristics include shear strength, displacement deformation characteristics and crack development characteristics.

2. The visual large-scale ice-soil-structure interface shear test method of tangential freezing according to claim 1 is characterized in that: The upper shear box and the lower shear box of the large ice-soil-structure interface shear tester are both rectangular structures. The cross-sectional size of the lower shear box is larger than that of the upper shear box, and the height of the lower shear box is higher than the height of the structural material arranged in the lower shear box.

3. The visual large-scale ice-soil-structure interface shear test method of tangential freezing according to claim 1 is characterized in that: The side wall of the upper shear box is provided with a plurality of temperature measuring holes, through which temperature sensors are inserted into the soil sample to be sheared at certain intervals to measure the temperature of the soil sample to be sheared.

4. The visual large-scale ice-soil-structure interface shear test method of tangential freezing according to claim 1 is characterized in that: The circulating fluid includes brine or liquid nitrogen.

5. The tangentially frozen visible large-scale ice-soil-structure interface shear test method according to claim 1, characterized in that: The preset normal load is determined according to the in-situ buried depth state of the soil sample to be sheared.

6. The visual large-scale ice-soil-structure interface shear test method of tangential freezing according to claim 1 is characterized in that: The sides of the upper shear box are all visible areas made of organic glass; The visible area formed by the organic glass on the side of the upper shear box includes a temperature control layer inside, and the temperature control layer is used to provide a temperature boundary of the soil sample to be sheared and provide a defrosting function for the visible area.

7. The visible large-scale ice-soil-structure interface shear test method of tangential freezing according to claim 6 is characterized in that: The DIC measurement system includes a camera and a marking point; Arranging marking points on the surface of the soil sample to be sheared in the visible area, wherein the marking points are evenly distributed colored sand; The camera faces the side with the marking point in the visible area of ​​the upper shear box, takes continuous pictures of the visible area, and obtains the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared during the freezing process and the shearing process through DIC technical analysis. The displacement deformation characteristics include displacement amount, displacement rate and shear band morphology; the crack development characteristics include freezing front development rate and crack development dynamic field.

8. The visual large-scale ice-soil-structure interface shear test method of tangential freezing according to claim 7 is characterized in that: The crack development dynamic field is the crack expansion law exhibited on a mesoscopic scale during the evolution of the ice lens; the crack development dynamic field includes crack size, crack density and crack arrangement.

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