A ring-shaped concrete test piece deterioration simulation test device and test method

Abstract

The application discloses a kind of annular concrete specimen deterioration simulation test device, belong to tunnel support deterioration technical field.The device includes the deterioration cylinder bottom shell and the deterioration cylinder sealing cover assembly formed deterioration cylinder, annular concrete specimen is coaxially arranged in the deterioration cylinder.The outer periphery of annular concrete specimen and the inner wall of deterioration cylinder bottom shell are sequentially provided with composite confining pressure layer and radial confining pressure system formed by equalizing plate and radial pressure piston, while the deterioration cylinder sealing cover is provided with liquid inlet for injecting deterioration solution into the deterioration cylinder to apply radial water pressure.The application also discloses corresponding test method.The application can simultaneously apply and accurately maintain specified radial confining pressure and water pressure to the specimen, effectively simulate the mechanical-chemical coupling deterioration environment of tunnel support structure;At the same time, combined with axially aligned ultrasonic emission and receiving head, the evolution process of internal damage of concrete can be monitored in situ and non-destructively in real time.

Description

Technical Field

[0001] This invention belongs to the field of tunnel support deterioration technology, specifically relating to a test device and test method for simulating the deterioration of annular concrete specimens under specified confining pressure and water pressure. Background Technology

[0002] With the vigorous development of transportation, water conservancy, and energy infrastructure construction in my country, the scale and depth of tunnels and underground engineering projects are increasing daily. Tunnel support structures, especially concrete linings, are subjected to complex geological environments for extended periods, bearing the combined effects of high ground stress (confining pressure) and high water pressure, while simultaneously being exposed to corrosive ions from groundwater (such as SO4²⁻). - Cl - Mg² + Chemical corrosion (such as chemical corrosion). The coupling effect of this mechanical load and chemical erosion will significantly accelerate the deterioration of concrete materials, such as reduced strength, increased permeability, and crack propagation, seriously threatening the safety and durability of the structure.

[0003] To study the deterioration characteristics of concrete under simulated service conditions, experimental devices are typically used for simulation. However, existing simulation experimental devices have the following limitations: Most existing testing devices focus on the study of single factors: for example, a simple mechanical testing device can apply axial pressure and confining pressure to a standard cylindrical or cubic specimen, but it is difficult to apply controllable, flowing water pressure and chemical environment simultaneously; or a simple permeability testing device can achieve permeability under a certain water pressure, but it is difficult to simultaneously simulate the radial mechanical constraints borne by tunnel support.

[0004] The morphology of the test specimens differs from that of the actual structure: most studies use solid cylindrical or cuboid specimens. However, the actual tunnel support is a ring-shaped thin-walled structure. Its stress state (pressure difference between the inner and outer walls), seepage path (mainly radial), and deterioration process are fundamentally different from those of solid specimens. Using solid specimens makes it difficult to truly reflect the service conditions of the lining structure under the combined action of confining pressure and water pressure.

[0005] Traditional methods for monitoring the degradation process of concrete are outdated and destructive: These methods primarily rely on staged destructive testing, such as removing specimens after different testing cycles for compressive strength testing, microstructural observation (e.g., SEM), or ion content analysis. This approach cannot provide in-situ, continuous, and non-destructive real-time monitoring of the degradation process of the same specimen, resulting in large data dispersion. It is difficult to accurately capture the dynamic evolution of damage development and to establish a real-time correlation between damage variables and environmental parameters.

[0006] Therefore, existing technologies lack a testing device that can simultaneously apply and precisely maintain a specified radial confining pressure and water pressure on annular concrete specimens, simulate the actual seepage path, and achieve in-situ non-destructive real-time monitoring. Summary of the Invention

[0007] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a test device and test method for simulating the deterioration of annular concrete specimens, which applies and precisely maintains a specified radial confining pressure and water pressure on the annular concrete specimens, simulates the real seepage path, and realizes in-situ non-destructive real-time monitoring.

[0008] To achieve the above objectives, according to one aspect of the present invention, a device for simulating the deterioration of annular concrete specimens is provided, characterized in that it comprises a deterioration cylinder formed by assembling a bottom shell of a deterioration cylinder and a sealing cap of a deterioration cylinder; The inner cavity of the deterioration cylinder is coaxially provided with an annular concrete specimen. Between the outer periphery of the annular concrete specimen and the inner sidewall of the bottom shell of the deterioration cylinder, a composite confining layer and a radial confining system are sequentially provided. The radial confining system includes several confining units arranged circumferentially. Each confining unit includes a radial pressure piston and a pressure equalizing plate. The composite confining layer includes a flow guide net covering the outer wall of the annular concrete specimen and crushed stone filling surrounding rock filling the space between the flow guide net and the pressure equalizing plate. One end of the radial pressure piston is connected to the pressure equalization plate, and the other end passes through the side wall of the bottom shell of the deterioration cylinder and is connected to an external drive device for applying radial confining pressure. The piston end of the radial pressure piston is equipped with a pressure sensor for real-time monitoring of the radial confining pressure. The sealing cover of the deterioration cylinder is equipped with a liquid inlet for injecting deterioration solution into the deterioration cylinder to apply radial water pressure. The inner wall of the bottom shell of the deterioration cylinder is equipped with a water pressure sensor for real-time monitoring of the water pressure inside the deterioration cylinder. The top and bottom surfaces of the deterioration cylinder are equipped with ultrasonic transmitters and receivers aligned with the annular concrete specimens to monitor their deterioration process.

[0009] As a further improvement of the present invention, the top of the deterioration cylinder sealing cover is symmetrically provided with several liquid inlets, which are respectively connected to an external high-pressure plunger pump through pipelines. The pressure equalizing plate and the inner wall of the deteriorated cylinder bottom shell are spaced apart to form an annular cavity, and each liquid inlet is provided corresponding to the annular cavity.

[0010] As a further improvement of the present invention, the annular concrete specimen is also provided with several saturation sensors.

[0011] As a further improvement of the present invention, the annular concrete specimen includes a specimen body, and a flexible pad is attached to the upper and lower annular end faces of the specimen body for sealing the contact surfaces between the annular concrete specimen and the deterioration cylinder sealing cap and the deterioration cylinder bottom shell.

[0012] As a further improvement of the present invention, the deterioration cylinder sealing cover is provided with a deterioration cylinder sealing cover opening in the middle, and the bottom center of the deterioration cylinder bottom shell is provided with a deterioration cylinder bottom shell opening. The deterioration cylinder sealing cover opening, the deterioration cylinder bottom shell opening, and the through hole in the middle of the annular concrete specimen are coaxially arranged. The diameter of the opening in the sealing cap of the deterioration cylinder is less than or equal to the diameter of the through hole in the middle of the annular concrete specimen; the diameter of the opening in the bottom shell of the deterioration cylinder is less than or equal to the diameter of the through hole in the middle of the annular concrete specimen.

[0013] As a further improvement of the present invention, the inner side of the equalizing plate contacts the outer surface of the crushed stone-filled surrounding rock, and its area is slightly smaller than the corresponding surface of the crushed stone-filled surrounding rock to prevent jamming.

[0014] As a further improvement of the present invention, the deterioration cylinder sealing cover is detachably fastened to the top of the deterioration cylinder bottom shell, and the lower edge of the cover body of the deterioration cylinder sealing cover is provided with a first sealing groove, and the upper edge of the deterioration cylinder bottom shell is provided with a second sealing groove. The first sealing groove and the second sealing groove are aligned and fitted, and a sealing ring is embedded therein.

[0015] According to another aspect of the present invention, a method for simulating the deterioration of annular concrete specimens is provided, using the aforementioned device for simulating the deterioration of annular concrete specimens, comprising the following steps: S1: Set target water pressure radial confining pressure of the target ; S2: Fill the inner cavity of the device with a pre-prepared deteriorated solution through the inlet and purge the air. S3: Activate the independent water pressure closed-loop control system and radial confining pressure closed-loop control system; The water pressure closed-loop control system monitors the water pressure inside the device in real time through a water pressure sensor. The first PID controller determines the relationship with... error Output control signal to adjust the liquid output of the high-pressure plunger pump to maintain ; The radial confining pressure closed-loop control system monitors the radial confining pressure applied to the annular concrete specimen in real time using pressure sensors. The second PID controller determines the relationship with... error Output control signal to drive radial pressure piston to maintain ; S4: The experiment was conducted under a stable water pressure and confining pressure coupling environment. The saturation data inside the annular concrete specimen was collected by a saturation sensor, and ultrasonic detection was performed periodically by an ultrasonic transmitter and receiver. The evolution of internal damage in the concrete was evaluated based on the changes in the ultrasonic signal.

[0016] As a further improvement of the present invention, in S2, the method for purging the air is as follows: Open one of the liquid inlets to activate the venting port, and inject the deteriorated solution into the inner cavity of the device through the other liquid inlets. Once the venting port continues to flow out of the solution and there are no more bubbles, it can be confirmed that the air has been completely expelled. Then connect the liquid inlet to the high-pressure plunger pump.

[0017] As a further improvement of the present invention, in S3, the first PID controller generates a control signal according to the PID algorithm in equation (1). : (1) In the formula, , , These are the proportional, integral, and derivative gain coefficients of the first PID controller, respectively. The second PID controller generates control signals according to the PID algorithm in equation (2). : (2) In the formula, , , These are the proportional, integral, and derivative gain coefficients of the second PID controller, respectively.

[0018] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art: (1) The annular concrete specimen deterioration simulation test device of the present invention can simultaneously apply specified radial confining pressure and aqueous solution pressure to the annular concrete specimen through the synergistic effect of the radial confining pressure system and the high-pressure water circulation system, effectively simulating the mechanical and chemical coupling deterioration environment of the real underground structure.

[0019] (2) The annular concrete specimen deterioration simulation test device of the present invention utilizes an axially aligned ultrasonic transmitter and receiver head to monitor the internal damage evolution process of concrete under multiple factors in real time without interrupting the experiment or damaging the specimen, thereby achieving in-situ, non-destructive monitoring of the deterioration process and significantly improving the continuity and accuracy of test data.

[0020] (3) The annular concrete specimen deterioration simulation test device of the present invention pumps a deterioration solution with specific chemical composition into the system through a high-pressure plunger pump, which can flexibly carry out concrete durability tests under different chemical corrosion environments and realize the controllable simulation of chemical corrosion factors. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the overall structure of the test device according to an embodiment of the present invention; Figure 2 This is an exploded view of the internal structure of the test apparatus according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the deteriorated cylinder sealing cap structure involved in the test apparatus of this invention embodiment; Figure 4 This is a schematic diagram of the annular concrete specimen structure involved in the test apparatus of this invention. Figure 5 This is a schematic diagram of the internal saturation sensor of the annular concrete specimen involved in the experimental apparatus of this invention. Figure 6 This is a schematic diagram of the composite confining pressure layer structure involved in the test apparatus of this invention. Figure 7 This is a schematic diagram of the radial confining pressure system involved in the test apparatus of this invention. Figure 8 This is a schematic diagram of the deterioration cylinder sealing cap and the deterioration cylinder bottom shell structure involved in the test apparatus of this invention.

[0022] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1-Deterioration cylinder sealing cap; 2-Annular concrete specimen; 3-Composite confining layer; 4-Radial confining system; 5-Deterioration cylinder bottom shell; 11. Liquid inlet; 12. Ultrasonic transmitter; 13. Cover; 14. Deterioration cylinder sealing cover opening; 21. Specimen body; 22. Flexible pad; 23. Saturation sensor; 31. Flow guide net; 32. Crushed rock filling surrounding rock; 41. Radial pressure piston; 42. Pressure equalizing plate; 51. Bottom shell body; 52. Water pressure sensor; 53. Ultrasonic receiver; 54. Radial pressure piston reserved hole; 55. Deterioration cylinder bottom shell opening. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0026] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0028] like Figures 1 to 8 As shown, this embodiment provides a ring-shaped concrete specimen deterioration simulation test device for simulating the chemical-mechanical coupling deterioration process of tunnel support structures under complex water pressure and confining pressure. The test device includes a deterioration cylinder formed by assembling a deterioration cylinder bottom shell 5 and a deterioration cylinder sealing cover 1, and a ring-shaped concrete specimen 2 coaxially arranged in the inner cavity of the deterioration cylinder.

[0029] A composite confining layer 3 and a radial confining system 4 are sequentially arranged between the outer periphery of the annular concrete specimen 2 and the inner wall of the deteriorated bottom shell 5. The radial confining system 4 includes several confining units arranged circumferentially, each confining unit including a radial pressure piston 41 and a pressure equalizing plate 42; the composite confining layer 3 includes a flow guiding net 31 covering the outer wall of the annular concrete specimen 2 and crushed stone filling surrounding rock 32 filling the space between the flow guiding net 31 and the pressure equalizing plate 42, which is used to simulate the real rock mass environment around the tunnel.

[0030] One end of the radial pressure piston 41 is connected to the pressure equalization plate 42, and the other end passes through the side wall of the deterioration cylinder bottom shell 5 and is connected to an external drive device to apply radial mechanical loads (radial confining pressure). Furthermore, a pressure sensor (not shown in the figure) is provided at the piston end of the radial pressure piston 41. By dividing the real-time data by the area of ​​the pressure equalization plate, the radial confining pressure can be dynamically estimated, enabling real-time monitoring of the radial confining pressure and simulating the specified confining pressure deterioration of the tunnel support structure.

[0031] Meanwhile, the deterioration cylinder sealing cover 1 is provided with a liquid inlet 11 for injecting deterioration solution into the deterioration cylinder, applying radial water pressure to the annular concrete specimen, and a water pressure sensor 52 is also installed on the inner wall of the bottom shell 5 of the deterioration cylinder for real-time monitoring of the water pressure inside the deterioration cylinder, so as to realize the specified water pressure deterioration simulation of the tunnel support structure.

[0032] In a preferred embodiment, the deterioration cylinder sealing cover 1 includes a cover body 13. The top of the cover body 13 is symmetrically provided with several liquid inlets 11, which are connected to an external high-pressure plunger pump via pipelines for pumping, maintaining, or replacing the deterioration solution into the deterioration cylinder. An annular cavity is formed between the equalizing plate 42 and the inner wall of the deterioration cylinder bottom shell 5, with each liquid inlet 11 corresponding to this annular cavity. Specifically, the liquid inlets 11 are radially arranged outside the equalizing plate 42 of the radial confining pressure system 4 and inside the deterioration cylinder bottom shell 5.

[0033] More preferably, the top of the cover 13 is also provided with an ultrasonic transmitter 12, the emitting surface of which faces the inside of the deterioration cylinder, and an ultrasonic receiver 53 is correspondingly provided at the bottom of the bottom shell 5 of the deterioration cylinder. The ultrasonic transmitter 12 and the ultrasonic receiver 53 are arranged corresponding to the annular concrete specimen 2 and are vertically aligned to ensure that the ultrasonic beam emitted by the ultrasonic transmitter 12 can penetrate the annular concrete specimen 2 vertically and be effectively received by the ultrasonic receiver 53. The changes in characteristic parameters such as wave velocity and amplitude attenuation after the ultrasonic waves penetrate the specimen reflect the internal damage process of the concrete (such as the generation, propagation and connection of microcracks).

[0034] Of course, the arrangement of the ultrasonic receiver 53 located at the top of the cover 13 and the ultrasonic transmitter 12 located at the bottom of the deteriorated cylinder shell 5 can also achieve the above-mentioned technical effect and is also within the protection scope of this application, as long as they are aligned along the annular concrete specimen 2.

[0035] More preferably, the bottom shell body 51 of the deterioration cylinder bottom shell 5 is a cylindrical structure with an open top, and the deterioration cylinder sealing cover 1 is detachably sealed to the top of the deterioration cylinder bottom shell 5. More preferably, the deterioration cylinder sealing cover 1 is fastened to the top opening of the deterioration cylinder bottom shell 5 by bolts. More preferably, the lower edge of the cover body 13 of the deterioration cylinder sealing cover 1 is provided with a first sealing groove, and the upper edge of the deterioration cylinder bottom shell 5 is provided with a second sealing groove. The first sealing groove and the second sealing groove are aligned and fitted, and a sealing ring is embedded therein to form a completely sealed high-pressure cavity.

[0036] More preferably, the cover 13 has a deterioration cylinder sealing cover opening 14 in the middle, and the bottom shell body 51 of the deterioration cylinder bottom shell 5 has a deterioration cylinder bottom shell opening 55 at its bottom center. The deterioration cylinder sealing cover opening 14, the deterioration cylinder bottom shell opening 55, and the central through hole of the annular concrete specimen 2 are coaxially arranged, that is, their centers are aligned along the same line, so that the test device as a whole forms a central through hole structure. More preferably, the diameter of the deterioration cylinder sealing cover opening 14 is less than or equal to the diameter of the central through hole of the annular concrete specimen 2; the diameter of the deterioration cylinder bottom shell opening 55 is less than or equal to the diameter of the central through hole of the annular concrete specimen 2. More preferably, the joint surfaces of the flexible pads 22 on both sides of the annular concrete specimen 2 with the cover 13 and the deterioration cylinder bottom shell 5 are uniformly coated with adhesive.

[0037] More preferably, the side wall of the bottom shell body 51 of the deterioration cylinder bottom shell 5 is uniformly provided with a plurality of radial pressure piston reserved holes 54 along the circumference. The number, setting position, and size of the radial pressure piston reserved holes 54 correspond to those of the radial pressure pistons 41. One end of the radial pressure piston 41 is fixedly connected to the pressure equalizing plate 42, and the other end passes through the radial pressure piston reserved holes 54 opened on the side wall of the deterioration cylinder bottom shell 5, extending to the outside of the cylinder and connecting with external driving devices such as servo mechanisms. A sealing structure (such as a sealing ring) is provided between the radial pressure piston 41 and the radial pressure piston reserved holes 54 to achieve dynamic sealing and ensure that the inside of the cylinder is sealed.

[0038] In a preferred embodiment, the annular concrete specimen 2 includes a specimen body 21, and a flexible pad 22 is attached to the upper and lower annular end faces of the specimen body 21. The flexible pad 22 is made of a waterproof material and is used to seal the contact surfaces between the annular concrete specimen 2 and the deterioration cylinder sealing cap 1 and the deterioration cylinder bottom shell 5, so as to ensure that the deterioration solution injected subsequently can only seep through the radial direction of the annular concrete specimen 2.

[0039] More preferably, the annular concrete specimen 2 is further equipped with several saturation sensors 23. During the pouring of the annular concrete specimen 2, the saturation sensors 23 are pre-embedded in predetermined positions inside the annular concrete specimen 2. Under the combined action of confining pressure and chemical erosion, microcracks will be generated inside the concrete. The generation of microcracks will significantly change the permeability of the concrete. By monitoring the rate of increase in saturation, the development of internal damage can be indirectly inferred. For example, a sudden acceleration in the increase in saturation may reflect the penetration of the main crack. In addition, water itself affects the ultrasonic wave velocity, and water in microcracks will also change the scattering mode of the acoustic signal. Without saturation data, it is difficult to distinguish whether the change in ultrasonic signal is due to increased water content or crack damage. Combining the two can more accurately decouple the "water content effect" and the "damage effect".

[0040] In a preferred embodiment, the flow guiding net 31 is a metal or high-strength plastic net, which is wrapped around the outer wall of the annular concrete specimen 2. The function of the flow guiding net 31 is to make the fluid pressure passing through the crushed stone filling surrounding rock 32 evenly distributed on the outer wall of the annular concrete specimen 2.

[0041] More preferably, the inner side of the equalizing plate 42 contacts the outer surface of the crushed stone filling surrounding rock 32, and its area is slightly smaller than the corresponding surface of the crushed stone filling surrounding rock 32 to prevent jamming.

[0042] The installation process of the experimental apparatus of this invention is as follows: First, the annular concrete specimen 2 with the flexible padding layer 22 attached is placed coaxially in the middle of the inner cavity of the bottom shell 5 of the deterioration cylinder. Then, a flow guide net 31 is wrapped tightly around the outer wall of the annular concrete specimen 2. A radial confining pressure system 4 is installed around the flow guide net 31, and the radial pressure piston 41 is fixed to the pressure equalizing plate 42 through the side wall of the bottom shell 5 (welded or threaded). Next, crushed stone is filled between the flow guide net 31 and the pressure equalizing plate 42 to form a crushed stone-filled surrounding rock. Finally, the deterioration cylinder sealing cover 1 is fastened to the top opening of the bottom shell 5 of the deterioration cylinder with bolts to form a completely sealed high-pressure cavity.

[0043] Furthermore, this embodiment of the invention also provides a method for testing the deterioration of annular concrete specimens, comprising the following steps: S1: Set target water pressure radial confining pressure of the target ; S2: Fill the inner cavity of the device with a pre-prepared deteriorated solution through the inlet 11 and purge the air. Open one of the liquid inlets to activate the vent, and inject the deteriorated solution into the inner cavity of the device through the other liquid inlets. Once the vent continues to flow out of the solution and there are no more bubbles, it can be confirmed that the air has been completely expelled. Then close the liquid inlet and connect the liquid inlet to the high-pressure plunger pump.

[0044] S3: Activate the independent water pressure closed-loop control system and radial confining pressure closed-loop control system; The water pressure closed-loop control system monitors the water pressure inside the device in real time through water pressure sensor 52. The first PID controller determines the relationship with... error Output control signal to adjust the liquid output of the high-pressure plunger pump to maintain ; The radial confining pressure closed-loop control system monitors the radial confining pressure applied to the annular concrete specimen 2 in real time using a pressure sensor. The second PID controller determines the relationship with... error Output control signal to drive radial pressure piston 41 to maintain ; S4: The experiment was conducted under a stable water pressure and confining pressure coupling environment. The saturation data inside the annular concrete specimen 2 was collected by the saturation sensor 23, and ultrasonic detection was performed periodically by the ultrasonic transmitter 12 and the ultrasonic receiver 53. The evolution of internal damage in the concrete was evaluated based on the changes in the ultrasonic signal.

[0045] Furthermore, the following specific embodiments are provided to illustrate in detail the specific steps of conducting a degradation test using the above-described testing apparatus: (1) Experimental preparation Arrange the ultrasonic transmitter and receiver heads (staggered from the saturation sensor to avoid interference), connect the outlet of the high-pressure plunger pump to the inlet on the sealing cap, connect the radial pressure piston to the servo mechanism, and connect the ultrasonic transmitter / receiver head, water pressure sensor, saturation sensor, and the drive device of the radial pressure piston to the central data acquisition and control system. Determine the water pressure value to be simulated based on the research objectives. With radial confining pressure value .

[0046] (2) Liquid injection and air venting Start the high-pressure plunger pump and inject the pre-prepared deterioration solution (such as sulfate solution, chloride solution, etc.) into the sealed deterioration cylinder through the inlet until it is completely filled. Use the vent valve to purge all the air and then close the vent valve.

[0047] Specifically, the test apparatus has four liquid inlets, one of which is designated as the vent. First, a degraded solution is injected into the apparatus's internal cavity through a combination of the remaining inlets, while the vent remains open. Once a continuous flow of solution without bubbles is observed at the vent, it is confirmed that all air has been expelled, and the vent is then closed. Subsequently, all four inlets are connected to a high-pressure plunger pump, which pumps in a solution with the same composition as the internal components. This pump provides and maintains a stable liquid pressure for the system, while ensuring the stability of the solution composition. The entire venting and pressurization process is completed under sealed conditions, without affecting the overall sealing performance of the test apparatus.

[0048] (3) Dual closed-loop pressure servo control is achieved through an independent water pressure closed-loop control system and a radial confining pressure closed-loop control system. The water pressure closed-loop control system continuously collects the current water pressure inside the deterioration cylinder through water pressure sensor 52. The data is transmitted to the first PID controller. The first PID controller calculates the measured value at time t. With set value error The control signal is generated according to the PID algorithm in equation (1). : (1) In the formula, , , These are the proportional, integral, and derivative gain coefficients of the first PID controller, used to adjust the controller's response speed to errors, eliminate steady-state errors, and suppress overshoot.

[0049] This control signal By controlling the operation of the high-pressure plunger pump and fine-tuning the volume of liquid pumped in or out, the system dynamically compensates for water pressure changes caused by seepage, leakage, or chemical reactions, thereby... Precisely stabilized at the set value .

[0050] The radial confining pressure closed-loop control system continuously monitors the radial confining pressure applied to the specimen via a pressure sensor (not shown in the figure). The data is transmitted to the second PID controller. The second PID controller calculates the measured value of t. With set value error The control signal is generated according to the PID algorithm in equation (2). : (2) In the formula, , , These are the proportional, integral, and derivative gain coefficients of the second PID controller, used to adjust the controller's response speed to errors, eliminate steady-state errors, and suppress overshoot.

[0051] This control signal The drive servo mechanism pushes or retracts the radial pressure piston, thereby directly and independently adjusting the radial mechanical pressure acting on the crushed stone-filled surrounding rock and the specimen. Stabilizes at the set value .

[0052] (5) Deterioration simulation and non-destructive monitoring In the precisely controlled mechanical-chemical coupling environment of step (4), the long-term degradation test begins. Throughout the test: The water pressure closed-loop control system and the radial confining pressure closed-loop control system work continuously to automatically maintain the set water pressure and confining pressure.

[0053] Furthermore, the data acquisition system synchronously and in real time records the data transmitted back from the water pressure, radial confining pressure, and internal saturation sensor of the specimen.

[0054] Simultaneously, at set intervals (e.g., every 24 hours), the control system automatically triggers ultrasonic testing. The ultrasonic transmitter emits a pulse signal, which penetrates the annular concrete specimen and is received by the ultrasonic receiver at the bottom. The control system analyzes the changes in characteristic parameters such as wave velocity and amplitude attenuation after the ultrasonic waves penetrate the specimen, and assesses the development of internal damage in the concrete in situ. The decrease in wave velocity and the increased amplitude attenuation are direct reflections of the generation, propagation, and connection of microcracks inside the concrete, i.e., damage accumulation.

[0055] By performing time-domain correlation analysis on mechanical loading data, chemical water pressure environment data, internal saturation data, and ultrasonic non-destructive testing data, the entire damage evolution process of concrete under the combined action of specified confining pressure and water pressure can be revealed in situ, in real time, and non-destructively.

[0056] This invention, through innovative structural design and an independent dual-closed-loop control strategy, successfully achieves high-precision and repeatable simulation of complex underground environments (high water pressure, high ground stress) and chemical erosion factors. Combined with ultrasonic technology, it enables real-time visual monitoring of the deterioration process, providing a powerful experimental means for the durability study and life prediction of tunnel concrete support structures.

[0057] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for simulating the deterioration of annular concrete specimens, characterized in that, The deterioration cylinder is formed by assembling the bottom shell of the deterioration cylinder and the sealing cap of the deterioration cylinder; The inner cavity of the deterioration cylinder is coaxially provided with an annular concrete specimen. Between the outer periphery of the annular concrete specimen and the inner sidewall of the bottom shell of the deterioration cylinder, a composite confining layer and a radial confining system are sequentially provided. The radial confining system includes several confining units arranged circumferentially. Each confining unit includes a radial pressure piston and a pressure equalizing plate. The composite confining layer includes a flow guide net covering the outer wall of the annular concrete specimen and crushed stone filling surrounding rock filling the space between the flow guide net and the pressure equalizing plate. One end of the radial pressure piston is connected to the pressure equalization plate, and the other end passes through the side wall of the bottom shell of the deterioration cylinder and is connected to an external drive device for applying radial confining pressure. The piston end of the radial pressure piston is equipped with a pressure sensor for real-time monitoring of the radial confining pressure. The sealing cover of the deterioration cylinder is equipped with a liquid inlet for injecting deterioration solution into the deterioration cylinder to apply radial water pressure. The inner wall of the bottom shell of the deterioration cylinder is equipped with a water pressure sensor for real-time monitoring of the water pressure inside the deterioration cylinder. The top and bottom surfaces of the deterioration cylinder are equipped with ultrasonic transmitters and receivers aligned with the annular concrete specimens to monitor their deterioration process.

2. The annular concrete specimen deterioration simulation test device according to claim 1, characterized in that, The top of the deterioration cylinder sealing cover is symmetrically provided with several liquid inlets, which are respectively connected to an external high-pressure plunger pump through pipelines; The pressure equalizing plate and the inner wall of the deteriorated cylinder bottom shell are spaced apart to form an annular cavity, and each liquid inlet is provided corresponding to the annular cavity.

3. The annular concrete specimen deterioration simulation test device according to claim 1, characterized in that, The annular concrete specimen is also equipped with several saturation sensors.

4. The annular concrete specimen deterioration simulation test device according to claim 1, characterized in that, The annular concrete specimen includes a specimen body, and flexible pads are attached to the upper and lower annular end faces of the specimen body to seal the contact surfaces between the annular concrete specimen and the sealing cap and bottom shell of the deterioration cylinder.

5. The annular concrete specimen deterioration simulation test apparatus according to any one of claims 1-4, characterized in that, The deterioration cylinder sealing cover has a sealing cover opening in the middle, and the bottom center of the deterioration cylinder bottom shell has a bottom shell opening. The sealing cover opening, the bottom shell opening, and the through hole in the middle of the annular concrete specimen are coaxially arranged. The diameter of the opening in the sealing cap of the deterioration cylinder is less than or equal to the diameter of the through hole in the middle of the annular concrete specimen; the diameter of the opening in the bottom shell of the deterioration cylinder is less than or equal to the diameter of the through hole in the middle of the annular concrete specimen.

6. The annular concrete specimen deterioration simulation test apparatus according to any one of claims 1-4, characterized in that, The inner side of the equalizing plate is in contact with the outer surface of the crushed stone-filled surrounding rock, and its area is slightly smaller than the corresponding surface of the crushed stone-filled surrounding rock to prevent jamming.

7. The annular concrete specimen deterioration simulation test apparatus according to any one of claims 1-4, characterized in that, The deterioration cylinder sealing cover is detachably fastened to the top of the deterioration cylinder bottom shell, and the lower edge of the sealing cover body is provided with a first sealing groove, and the upper edge of the deterioration cylinder bottom shell is provided with a second sealing groove. The first sealing groove and the second sealing groove are aligned and fitted, and a sealing ring is embedded therein.

8. A method for simulating the deterioration of annular concrete specimens, using the annular concrete specimen deterioration simulation test apparatus according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Set target water pressure radial confining pressure of the target ; S2: Fill the inner cavity of the device with a pre-prepared deteriorated solution through the inlet and purge the air. S3: Activate the independent water pressure closed-loop control system and radial confining pressure closed-loop control system; The water pressure closed-loop control system monitors the water pressure inside the device in real time through a water pressure sensor. The first PID controller determines the relationship with... error Output control signal to adjust the liquid output of the high-pressure plunger pump to maintain ; The radial confining pressure closed-loop control system monitors the radial confining pressure applied to the annular concrete specimen in real time using pressure sensors. The second PID controller determines the relationship with... error Output control signal to drive radial pressure piston to maintain ; S4: The experiment was conducted under a stable water pressure and confining pressure coupling environment. The saturation data inside the annular concrete specimen was collected by a saturation sensor, and ultrasonic detection was performed periodically by an ultrasonic transmitter and receiver. The evolution of internal damage in the concrete was evaluated based on the changes in the ultrasonic signal.

9. The method for simulating the deterioration of annular concrete specimens according to claim 8, characterized in that, In S2, the method for purging the air is as follows: Open one of the liquid inlets to activate the venting port, and inject the deteriorated solution into the inner cavity of the device through the other liquid inlets. Once the venting port continues to flow out of the solution and there are no more bubbles, it can be confirmed that the air has been completely expelled. Then connect the liquid inlet to the high-pressure plunger pump.

10. The method for simulating the deterioration of annular concrete specimens according to claim 8 or 9, characterized in that, In S3, the first PID controller generates a control signal according to the PID algorithm in equation (1). : （1） In the formula, , , These are the proportional, integral, and derivative gain coefficients of the first PID controller, respectively. The second PID controller generates control signals according to the PID algorithm in equation (2). : （2） In the formula, , , These are the proportional, integral, and derivative gain coefficients of the second PID controller, respectively.

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