A Shear Test Method for Visual Large-Scale Ice-Soil-Structure Interface with Tangential Freezing

Abstract

The present application discloses a tangential freezing visual large-scale ice-soil-structure interface shear test method, which relates to the field of geotechnical engineering and includes: preparing a soil-structure interface; using a circulation pump and a freezing chamber arranged on one side of the upper shear box to tangentially freeze the soil sample to be sheared under preset freezing conditions to form an ice-soil-structure interface; applying a preset normal load and simultaneously applying a shear force to conduct a shear test on the ice-soil-structure interface at a preset shear rate; simultaneously obtaining the side images of the soil sample to be sheared during freezing and shearing based on the DIC measurement system to obtain the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared; and combining the shear curve to obtain the shear characteristics of the ice-soil-structure interface. The present application can more accurately simulate the freezing situation of the soil-structure interface in real cold region projects, and visually display the development of cracks in the mesoscopic level of the interface ice, so as to deeply understand the shear characteristics of the ice-soil-structure interface.

Description

Technical Field

[0001] This application relates to the technical field of geotechnical engineering, and particularly to a visual large-scale ice-soil-structure interface shear test method with tangential freezing. Background Technique

[0002] With the increase in cold region engineering construction in polar regions, high altitudes, high latitudes, etc., engineering structures often face severe low-temperature environments and complex soil-structure interactions. The soil-structure interface affects load transfer, stress distribution, and deformation characteristics, and is very important for the safety and stability of engineering structures. Therefore, it is necessary to further study the shear characteristics of ice-containing soil-structure interfaces in cold regions, clarify the shear performance of the ice-soil-structure interface, and provide strong guarantees for cold region engineering construction.

[0003] At present, for shear tests related to cold region interfaces, the freezing method of soil samples from the bottom up around the interface by water bath (normal freezing) is mainly used. However, there are significant differences between this method and the low-temperature freezing effect of actual cold region interfaces. In particular, the above conventional freezing methods greatly weaken the ice cementing force generated during the freezing front migration process and the influence of the arrangement of ice lenses on the interface. At present, most of the cold region soil-structure interfaces to be studied are on the side of the foundation, and the natural freezing direction is parallel to the interface (tangential freezing), and the ice lenses are arranged layer by layer perpendicular to the interface. Different arrangement methods result in different ice contents on the interface, and the influence on the interface shear performance cannot be ignored. In addition, existing shear test systems often lack visualization means, especially for the formation and evolution process of interface ice, making it difficult to directly observe the deformation and failure process of the interface.

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

[0005] The purpose of this application is to provide a visual large-scale 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 engineering and obtain the relevant shear characteristics of the ice-soil-structure interface.

[0006] To achieve the above purpose, this application provides the following solutions:

[0007] The present application provides a method for tangential freezing visual large-scale ice-soil-structure interface shear test. The method for tangential freezing visual large-scale ice-soil-structure interface shear test is applied to a large-scale ice-soil-structure interface shear tester, which 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 inside 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;

[0008] The method for tangential freezing visual large-scale ice-soil-structure interface shear test specifically includes:

[0009] According to the test purpose, place the structural material in the lower shear box, and place the soil sample to be sheared in the upper shear box, so that the lower surface of the soil sample to be sheared in the upper shear box is in direct contact with the structural material in the lower shear box, forming a soil-structure interface;

[0010] Circulate and cool the circulating liquid in the pipeline through the circulation pump, and tangentially freeze the soil sample to be sheared by the freezing chamber on one side of the upper shear box under preset freezing conditions to form an ice-soil-structure interface; the freezing conditions include freezing temperature and freezing time;

[0011] Apply a preset normal load to the soil sample to be sheared after tangential freezing, and at the same time apply a shear force to conduct a shear test on the ice-soil-structure interface at a preset shear rate;

[0012] Based on the DIC measurement system, obtain the side images of the soil sample to be sheared during the freezing process and the shear process, and use the DIC measurement system to obtain the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared; and obtain the shear stress and shear displacement characteristics in real time, and draw a shear curve with the shear stress as the ordinate and the shear displacement characteristics as the abscissa;

[0013] Use data analysis methods to analyze the shear curves, freezing process and side images of the soil sample to be sheared during the shear process under different test conditions, and 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.

[0014] According to the specific embodiments provided by the present application, the present application has the following technical effects:

[0015] The present application provides a tangential freezing visual large-scale ice-soil-structure interface shear test method. By using a circulation pump and a freezing chamber arranged on one side of the upper shear box to tangentially freeze the soil sample to be sheared under preset freezing conditions, the freezing state of the soil-structure interface in real cold region projects can be accurately simulated, and the influence of ice lenses arranged perpendicular to the interface formed by tangential freezing on the shear characteristics of the ice-soil-structure interface can be considered, further revealing the shear mechanical behavior of the ice-soil-structure interface. At the same time, by obtaining the side images of the soil sample to be sheared during freezing and shearing based on the DIC measurement system, using DIC technology to analyze the displacement and deformation characteristics and crack development characteristics of the soil sample to be sheared, and obtaining the shear stress and shear displacement characteristics in real time, drawing a shear curve, and conducting data analysis, the problems 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 are solved. The present application can provide a shear test method that more conforms to the real situation of the ice-soil-structure interface 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

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 It is a schematic flow chart of a tangential freezing visual large-scale ice-soil-structure interface shear test method provided by an embodiment of the present application.

[0018] Figure 2 It is a front view of the structure of a large-scale ice-soil-structure interface shear tester provided by an embodiment of the present application.

[0019] Reference numerals: 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 - organic glass visual area, 9 - temperature control layer, 10 - marking point, 11 - water replenishing device, 12 - second loading device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0021] To make the above objects, features, and advantages of the present application more apparent and understandable, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] In an exemplary embodiment, a method for a tangential freezing visual large-scale ice-soil-structure interface shear test is provided. The tangential freezing visual large-scale ice-soil-structure interface shear test method is applied to a large-scale ice-soil-structure interface shear tester. The size range of the large-scale ice-soil-structure interface shear tester is between more than ten centimeters and dozens of centimeters, as Figure 2 shown, and specifically includes: an upper shear box 6, a lower shear box 7, a circulation pump 1, a freezing chamber 4, and a DIC measurement system; wherein, the upper shear box 6 is sleeved inside the lower shear box 7; the circulation 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.

[0023] As an alternative embodiment, the large-scale ice-soil-structure interface shear tester further 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 one 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, located above the upper shear box 6, contacts the soil sample to be sheared through a 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.

[0024] As an alternative embodiment, the large-scale ice-soil-structure interface shear tester further includes a temperature measurement device and a water replenishing device 11.

[0025] The temperature measurement device includes a plurality of temperature sensors. The temperature sensors can use thermocouples, optical fibers, etc. Temperature measurement holes are opened on the side wall of the upper shear box 6, and the temperature sensors are inserted into the test soil sample through the temperature measurement holes to obtain the variation law of the temperature at different positions of the soil sample with time during the test.

[0026] The water replenishing device 11 is located inside the lower shear box 7, fills a part of the lower shear box 7 with water, and replenishes water to the interface by means of water replenishment through a water tank, simulating the open system state with external water replenishment in the real situation.

[0027] As an alternative embodiment, the DIC measurement system in the large-scale ice-soil-structure interface shear tester includes a high-precision industrial camera and the marking points 10 on the test soil sample. The high-precision industrial camera is used to collect images of the soil sample in the visible area of the upper shear box 6, and digital image correlation method is used for data processing. The planar displacement changes of the soil sample at different positions in different regions within the upper shear box 6 are calculated based on the images at different times. The DIC method can capture the soil displacement information with high spatial and temporal resolutions, without contacting the soil sample, avoiding the interference that traditional contact measurements may cause to the soil structure and ensuring that the experimental conditions are closer to the real state. Among them, the temperature or water replenishment state in different regions at different times is different. Generally, the temperature is lower in the places closer to the cold source, and it gradually becomes 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 region of the soil sample to be sheared migrates towards the frozen region.

[0028] The visible large-scale ice-soil-structure interface shear test method with tangential freezing, as Figure 1 shown, specifically includes:

[0029] Step 101, according to the test purpose, place the structural material in the lower shear box 7, and place the soil sample to be sheared 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.

[0030] Step 102, circulate and cool the circulating liquid in the pipeline through the circulating pump 1, and tangentially freeze the soil sample to be sheared by the freezing chamber 4 under preset freezing conditions; the freezing conditions include freezing temperature and freezing time.

[0031] Step 103, apply a preset normal load on the soil sample to be sheared after tangential freezing, and at the same time apply a shear force to conduct 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 state of the soil sample to be sheared; the preset shear rate is determined according to relevant specifications and literature.

[0032] Step 104, based on the DIC measurement system, obtain the side images of the soil sample to be sheared during the freezing process and the shear process, and use the DIC measurement system to obtain the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared; and obtain the shear stress and shear displacement characteristics in real time, and draw a shear curve with the shear stress as the ordinate and the shear displacement characteristics as the abscissa. The DIC measurement system detects the development rate of the freezing front and the dynamic field of crack development of the soil sample to be sheared during the freezing and shear processes.

[0033] Step 105: Analyze the shear curves, freezing process, and side images of the soil sample to be sheared during the shearing process under different test conditions using data analysis methods 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 fracture development characteristics.

[0034] 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 test, contributing to a deeper understanding of the shear mechanism of the ice-soil-structure interface.

[0035] In another embodiment of the present application, the upper shear box 6 adopts a cuboid structure, surrounded by double-layer plexiglass on all sides, and a temperature control layer 9 is provided 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 provided on one side of the upper shear box 6, and the required temperature for the test is provided by the circulation pump 1. The transparent plexiglass part of the upper shear box 6 also provides a visible area for observing the changes in the soil sample to be sheared during the test.

[0036] Before the test starts, structural materials (such as concrete, steel plates, etc.) are placed in the lower shear box 7, and a 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 marking points 10 are evenly arranged for subsequent displacement deformation measurement. In this embodiment, the marking points 10 are evenly distributed colored sand. It should be noted that for soil properties such as sandy soil with obvious particles, marking points may not be required; for soil properties such as clay with inconspicuous particles, marking points 10 need to be arranged for subsequent displacement measurement based on DIC technology.

[0037] During the test, a real open system is simulated through the water replenishing device 11. The circulation pump 1 is started to transport the circulating medium to the freezing chamber 4. After being cooled by the circulation pump 1, the circulating medium flows into the freezing chamber 4 through the second pipeline 3 to tangentially freeze the soil sample to be sheared in the upper shear box 6, and then flows out from the first pipeline 2 and returns 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 second loading device 12 shears the specimen at a constant shear rate to simulate the shear force application 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 through temperature sensors, and the surface images of the soil sample are collected using a high-precision industrial camera.

[0038] The DIC technology is used to analyze the image sequence, and the results of the temperature measurement device, the water replenishing device 11, the DIC measurement device, etc. are summarized and analyzed. Combined with the data such as the sub-region temperature, displacement, stress, etc. along the tangential freezing direction of the soil-structure interface, the evolution process of ice lenses and the freezing shear characteristics of the ice-soil-structure interface that conform to the actual working conditions during the freezing shear process are analyzed. The obtained results can provide good help for actual engineering.

[0039] The present application has the following beneficial effects:

[0040] (1) The test soil sample is tangentially frozen by using a circulation pump and a low-temperature freezing chamber located on one side of the upper shear box, which is more in line with the freezing situation of the real soil-structure interface in cold region engineering.

[0041] (2) A temperature control layer is arranged 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 in the way of replenishing water through a water tank, simulating an open freezing system under real conditions.

[0042] (3) A high-precision industrial camera is used to take pictures of the marked points on the soil sample to be sheared through the visible area, and the development of cracks in the evolution of ice lenses at the mesoscopic level is analyzed from the photos. It is a non-contact measurement, with fast measurement speed, high precision and strong anti-interference ability.

[0043] 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 for analysis, stored data, displayed data, etc.) involved in the present 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 need to comply with relevant regulations.

[0044] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant 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 methods.

[0045] The technical features of the above embodiments can be combined arbitrarily. For the sake of brief description, 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, it should be considered as the scope recorded in this specification.

[0046] In this text, specific examples are used to illustrate the principles and implementation manners of the present application. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A tangential freezing visual large-scale ice-soil-structure interface shear test method, characterized in that The tangential freezing visual large-scale ice-soil-structure interface shear test method is applied to a large-scale ice-soil-structure interface shear tester, which specifically includes: an upper shear box, a lower shear box, a circulation pump, a freezing chamber, a water replenishing device, and a DIC measurement system; among them, the upper shear box is sleeved inside the lower shear box; both the upper shear box and the lower shear box of the large-scale ice-soil-structure interface shear tester are 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 inside the lower shear box; a plurality of temperature measurement holes are provided on the side wall of the upper shear box, and the temperature sensor is inserted into the internal of the soil sample to be sheared at a certain interval through the temperature measurement holes to measure the temperature of the soil sample to be sheared; 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 water replenishing device is located inside the lower shear box, used to partially fill the lower shear box with water, and replenish water to the interface in the way of replenishing water through a water tank to simulate the open system state with external water replenishment in the real situation; the side surfaces of the upper shear box are visible areas composed of plexiglass; the visible area inside the plexiglass on the side surface of the upper shear box includes a temperature control layer, and the temperature control layer is used to provide the temperature boundary of the soil sample to be sheared and provide a defrosting function for the visible area; The tangential freezing visual large-scale ice-soil-structure interface shear test method specifically includes: According to the test purpose, place the structural material inside the lower shear box, and place the soil sample to be sheared in the upper shear box, so that the lower surface of the soil sample to be sheared in the upper shear box is in direct contact with the structural material in the lower shear box, forming a soil-structure interface; Circulate and cool the circulating liquid in the pipeline through the circulation pump, and tangentially freeze the soil sample to be sheared by the freezing chamber on one side of the upper shear box under preset freezing conditions to form an ice-soil-structure interface; the freezing conditions include freezing temperature and freezing time; Apply a preset normal load to the soil sample to be sheared after tangential freezing, and at the same time apply a shear force to conduct a shear test on the ice-soil-structure interface at a preset shear rate; Based on the DIC measurement system, obtain the side images of the soil sample to be sheared during the freezing process and the shear process, and use the DIC measurement system to obtain the displacement deformation characteristics and crack development characteristics of the soil sample to be sheared; and obtain the shear stress and shear displacement characteristics in real time, and draw a shear curve with the shear stress as the vertical coordinate and the shear displacement characteristics as the horizontal coordinate; Use data analysis methods to analyze the shear curves, the side images of the soil sample to be sheared during the freezing process and the shear process under different test conditions, and 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.

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

3. The tangential freezing visual 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 burial depth state of the soil sample to be sheared.

4. The tangential freezing visual large-scale ice-soil-structure interface shear test method according to claim 1, characterized in that The DIC measurement system includes a camera and marking points; Arrange marking points on the surface of the soil sample to be sheared within the visible area, and the marking points are uniformly distributed colored sand; The camera is facing the side with the marked points in the visible area of the upper shear box, and continuously takes pictures of the visible area. Through DIC technology analysis, the displacement and deformation characteristics and fracture development characteristics of the soil sample to be sheared during the freezing process and the shearing process are obtained. The displacement and deformation characteristics include displacement amount, displacement rate and shear band morphology; the fracture development characteristics include the development rate of the freezing front and the fracture development dynamic field.

5. The tangential freezing visual large-scale ice-soil-structure interface shear test method according to claim 4, characterized in that The fracture development dynamic field is the fracture propagation law shown at the mesoscopic scale during the evolution process of ice lenses; the fracture development dynamic field includes fracture size, fracture density and fracture arrangement.

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