A plate cavity bubble retention visualization simulation device and SCC pourability evaluation method

Abstract

The application discloses a kind of plate cavity bubble retention visualization simulation device and SCC pourability evaluation method, its simulation device includes simulation cavity and control system, the upper cover of the simulation cavity is made of transparent material, and the upper cover is connected with perfusion mechanism, one end of the simulation cavity away from perfusion mechanism is equipped with exhaust hole and slurry discharge hole, the slurry discharge hole is equipped in the both sides of simulation cavity, the bottom of the simulation cavity is equipped with recess, the simulation cavity is equipped with pressure sensor array, and the simulation cavity is equipped with visual mechanism, and the control system is connected with visual mechanism and pressure sensor array communication respectively.Compared with prior art, the application introduces the coefficient K bow of arc-shaped recess, local peak pressure P max And pressure drop ΔP as correction factor, into the calculation of final state evaluation index F1 and B1, forms the complete technical closed loop of "process observation→parameter extraction→correction model→final state determination".

Description

Technical Field

[0001] This invention relates to the field of self-compacting concrete performance testing technology, and in particular to a visualization simulation device for air bubble retention in slab cavities and a method for evaluating the pourability of self-compacting concrete (SCC). Background Technology

[0002] Self-compacting concrete (SCC) is a high-performance concrete with high fluidity, anti-segregation properties, and excellent filling performance. During pouring, it can uniformly fill and compact without vibration, relying solely on its own weight. In the CRTSⅢ type slab track structure of high-speed railways, SCC plays a crucial role as a filling layer material, and its pouring process directly determines the construction quality and efficiency.

[0003] During the actual grouting process of the slab track filling layer, after the SCC enters the narrow slab cavity through the grouting hole, it undergoes a complex rheological process, which can be divided into several stages: The SCC first spreads radially, and after filling the slab cavity in the thickness direction, it transforms into a confined shear flow constrained by the upper and lower interfaces; as the flow continues, the SCC is forced to turn tangentially along the sidewall after contacting the longer template sidewall, forming a low-velocity zone where the flow velocity drops sharply and a large number of bubbles accumulate and stagnate; due to the different degrees of flow obstruction in each direction, the SCC flow front gradually evolves from a circle to an ellipse and forms an arc-shaped front; when the SCC passes through the limiting groove on the base plate, the streamlines are separated and disturbed, and the slurry on both sides reaches the discharge port first, while the slurry in the middle dissipates kinetic energy and reduces flow velocity due to the priority filling of the limiting groove and splits to both sides. The two slurry flows form a reverse confluence at the middle of the plate end, creating a low-velocity zone at the end, which prevents bubbles from being effectively discharged. After hardening, it forms a dense cluster of bubbles or a locally loose bubble layer, which seriously affects the compactness and service performance of the filling layer.

[0004] Existing testing devices and methods for the workability of self-compacting concrete (SCC) mainly include slump spread tests, L-shaped box tests, J-ring tests, and V-shaped funnel tests. For example, patent publication number CN200979545Y discloses a multi-functional measuring instrument for the workability of self-compacting concrete, which can perform the functions of the slump test, L-shaped test, and U-shaped box test, used to measure the viscosity, flowability, filling ability, and ability to penetrate steel reinforcement gaps of SCC. Patent application publication number CN121027490A discloses a rapid identification device for the pourable state of self-compacting concrete, which observes the pouring state and air bubble distribution of SCC in the box through a transparent observation plate, and evaluates the pourability performance by the flow rate ratio and height difference ratio.

[0005] However, the aforementioned existing technologies have the following shortcomings:

[0006] (1) Existing devices such as L-shaped boxes and J-rings are for single-direction flow tests with constant cross-sections or no top plate constraints. Simulation box devices can only reproduce simple radial spreading. None of the above devices can simulate the multi-stage flow process of SCC under the joint constraint of the upper and lower interfaces in a narrow plate cavity. Therefore, they cannot fully reproduce the formation process of the low-velocity zone at the end and the bubble retention behavior during the actual injection process.

[0007] (2) The evaluation indicators of the existing devices are too simplified, relying on single parameters such as passability and height difference ratio, and lack a quantitative evaluation indicator system that directly corresponds to the physical mechanism of each stage of the injection process.

[0008] (3) The existing device lacks the function of real-time monitoring of pressure distribution in the plate cavity, and cannot obtain information on pressure gradient decay and the formation of local micro-high pressure zone during the injection process. Summary of the Invention

[0009] This invention provides a visual simulation device for plate cavity bubble retention and a method for evaluating SCC injectability, in order to solve one or more of the problems in the background art mentioned above.

[0010] This invention provides a visualization simulation device for bubble retention in a plate cavity, comprising a simulation cavity and a control system. The upper cover of the simulation cavity is made of transparent material, and an injection mechanism is connected to the upper cover. The end of the simulation cavity away from the injection mechanism is provided with an exhaust port and a slurry discharge port, which are located on both sides of the simulation cavity. A groove is provided at the bottom of the simulation cavity. A pressure sensor array is provided inside the simulation cavity, and a vision mechanism is provided above the simulation cavity. The control system is communicatively connected to the vision mechanism and the pressure sensor array, respectively.

[0011] Preferably, the infusion mechanism includes a feeding funnel and a feeding conduit, the feeding funnel is connected to the feeding conduit, the feeding conduit extends into the simulated cavity, the lower end of the feeding conduit is connected to a support ring frame, the support ring frame is placed inside the simulated cavity, and the feeding conduit is provided with a feeding control component.

[0012] Preferably, the pressure sensing array includes multiple thin-film pressure sensors, which are respectively embedded in the inner surfaces of the upper cover plate, lower bottom plate, and side plate of the simulated cavity, and the thin-film pressure sensors are communicatively connected to the control system.

[0013] Preferably, the thin-film pressure sensors on each side plate are connected in series via a first data line, and each side plate is provided with a wire hole for a second data line to pass through. The thin-film pressure sensors are connected to the control system via the first data line and the second data line. The thin-film pressure sensors on the upper cover plate and the lower bottom plate are divided into multiple groups, and each group of thin-film pressure sensors is connected in series to the first data line on its adjacent side plate.

[0014] Preferably, the vision mechanism includes a camera and a light source bar, the light source bar being disposed on one or both sides of the simulation cavity, and the camera being communicatively connected to the control system.

[0015] This invention also provides a method for evaluating the injectability of SCC, comprising the following steps:

[0016] S1: Inject SCC into the simulated cavity through the infusion mechanism;

[0017] S2: The flow process of SCC within the simulated cavity is recorded by a camera to obtain the depth D of the SCC's arc-shaped indentation. bow Then calculate the bow-shaped concavity coefficient K. bow = L short This is to simulate the width of the shorter side of the cavity;

[0018] S3: The pressure values ​​at each monitoring point are collected in real time through a pressure sensor array to obtain P. max and P steady Calculate the pressure drop ΔP = P steady - P max , where P max P is the maximum pressure collected by the pressure sensing array before the SCC flow front contacts the side plate at the end of the simulated cavity away from the infusion mechanism. steady The stable pressure value collected in the plate end region during the reverse flow phase;

[0019] S4: Calculate the cavity filling coefficient F= A actual A represents the actual coverage area of ​​the SCC. cavity The design filling area of ​​the simulated cavity;

[0020] S5: Based on the images captured by the camera, obtain the number N of trapped bubbles. bubble and average diameter D avg Calculate the end bubble retention index B = V end The end overflow velocity;

[0021] S6: Utilize K from step S2 bow And P in S3 max The filling coefficient F1 and the bubble retention index B1 are corrected by ΔP, and then the saturability of SCC is evaluated based on the values ​​of F1 and B1: when F1 ≥ 0.95 and B1 ≤ 0.5 mm -1 If the SCC mix ratio is within acceptable limits, the grouting quality is deemed qualified; otherwise, it is deemed unqualified, and the SCC mix ratio or grouting process needs to be adjusted.

[0022] Preferably, in step S6, the filling coefficient F1 is calculated using the following formula:

[0023] F1 = F × (1 - α·K) bow )

[0024] Where α is an empirical coefficient, with a value ranging from 0.5 to 0.8.

[0025] Preferably, in step S6, the bubble retention index B1 is calculated using the following formula:

[0026] B1 =

[0027] Where β and γ are empirical coefficients, P ref The reference pressure is 1000 Pa; the value of β ranges from 0.2 to 0.4, and the value of γ ranges from 0.3 to 0.6.

[0028] Preferably, the bow-shaped concavity coefficient K bow When the value exceeds the preset threshold of 0.12, it is determined that the SCC has insufficient following ability in changing flow, and there is a risk of trapped air, and a real-time warning is issued.

[0029] Preferably, when P max When the pressure exceeds 1500 Pa or ΔP is below -1000 Pa, an end bubble retention risk warning is issued, and it is recommended to adjust the injection rate or venting scheme.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The flow field evolution of the entire actual grouting process was reproduced, and in particular, the simulation capability of the reverse confluence and counter-current effect at the plate end was proposed. By simulating the geometry of the narrow plate cavity, the friction of the upper and lower interfaces, the air permeability of the sidewalls and the groove structure, this device can not only reproduce the entire process of SCC from initial radial expansion, contact with the sidewalls to change direction and deceleration, the formation of the bow-shaped leading edge and the passage through the limiting groove, but also accurately reproduce the complex coupling process that the slurry on both sides first arrives at the end and then turns back, forming a counter-current with the slurry that arrives later in the middle, which cannot be simulated by existing devices, by reasonably arranging the slurry discharge / air hole positions and controlling the slurry overflow sequence.

[0032] (2) It realizes the full-process visualization tracking of bubble behavior and the synchronous monitoring of local flow field pressure. Through the transparent cavity design, side plate light source illumination and high-speed image acquisition, the complete trajectory of the bubble from entrainment and migration, lateral aggregation, residence in the bow-shaped area and final retention at the end can be clearly observed; at the same time, through the integrated pressure sensor array, the pressure gradient decay curve and the pressure peak of the bow-shaped concave triangular micro-high pressure area during the injection process are acquired in real time, providing direct image and quantitative data dual evidence for the hydrodynamic mechanism analysis of bubble retention.

[0033] (3) A quantitative evaluation index system directly corresponding to the grouting physical mechanism was established. New evaluation indexes such as “plate cavity filling coefficient F1” and “end bubble retention index B1” were proposed to characterize the ultimate spreading ability of SCC under multi-constraint directional resistance and the severity of bubble retention in the end low-speed zone, respectively. Compared with the single collapse expansion degree or height difference ratio index in the existing technology, it has stronger working condition targeting and quality prediction accuracy.

[0034] (4) A complete technical closed loop of "process observation → parameter extraction → model correction → final state determination" has been formed, and it has a real-time early warning function. This invention uses the bow-shaped indentation coefficient K obtained in real time during the injection process. bow Local peak pressure P max The pressure drop ΔP is used as a correction factor and introduced into the calculation of the final state evaluation indexes F1 and B1 to achieve accurate prediction of groutability. At the same time, by setting the threshold of the above parameters, abnormal flow states can be identified and early warnings can be issued in real time during the grouting process, providing a dynamic control method for on-site construction. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of the present invention;

[0037] Figure 2 This is an exploded structural diagram of the present invention;

[0038] Figure 3 This is a schematic diagram of the structure of the groove in the present invention;

[0039] Figure 4 This is a schematic diagram showing the locations of the vent hole, grout discharge hole, and grout injection hole of the present invention;

[0040] Figure 5 This is a schematic diagram of the vision mechanism of the present invention;

[0041] Figure 6 This is a schematic diagram of the pressure sensing array of the present invention;

[0042] Figure 7 This is a schematic diagram of the self-compacting concrete pouring process of the present invention;

[0043] Figure label:

[0044] 1. Simulated cavity, 2. Control system, 3. Injection mechanism, 4. Pressure sensor array, 5. Vision mechanism, 6. Lifting base plate, 7. Scissor lift mechanism, 8. Exhaust valve, 9. Self-compacting concrete, 11. Top cover plate, 12. Bottom plate, 13. Side plate, 31. Feeding funnel, 32. Feeding conduit, 33. Feeding control component, 34. Support ring frame, 41. Thin-film pressure sensor, 42. First data line, 51. Camera, 52. Light source bar, 100. Exhaust hole, 200. Grout discharge hole, 300. Groove, 400. Wire hole, 500. Injection hole. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] See attached document Figure 1 This embodiment provides a visualization simulation device for bubble retention in a plate cavity, including a simulation cavity 1 and a control system 2. The simulation cavity 1 is formed by an upper cover plate 11, a lower bottom plate 12, and four side plates 13. The upper cover plate 11 of the simulation cavity 1 is made of transparent material to facilitate observation of the flow state and bubble distribution of SCC from above. An injection mechanism 3 is connected to the upper cover plate 11. The injection mechanism 3 is used to inject SCC into the simulation cavity 1 to simulate the process conditions of SCC entering the plate cavity through the injection hole 500 in actual construction. (Refer to the attached...) Figure 4 The simulation cavity 1 is provided with an exhaust port 100 and a slurry discharge port 200 at one end away from the injection mechanism 3. The slurry discharge port 200 is located on both sides of the simulation cavity 1. The bottom of the simulation cavity 1 is provided with a groove 300. The simulation cavity 1 is provided with a pressure sensor array 4. The simulation cavity 1 is provided with a vision mechanism 5. The control system 2 is communicatively connected to the vision mechanism 5 and the pressure sensor array 4 respectively.

[0047] Specifically, of the four side plates 13, two side plates 13 are longer (long side plates 13), and the other two side plates 13 are shorter (short side plates 13), in order to simulate the long side template and short side template in actual filling.

[0048] One implementation of the injection mechanism 3: Refer to the attached document. Figure 2The grouting mechanism 3 includes a feeding funnel 31 and a feeding conduit 32. The feeding funnel 31 is connected to the feeding conduit 32. The feeding conduit 32 extends into the simulation cavity 1 through a grouting hole 500. The grouting hole 500 is located on the upper cover plate 11. The feeding conduit 32 is equipped with a feeding control component 33, which is used to adjust the grouting rate. The lower end of the feeding conduit 32 is connected to a support ring frame 34. The support ring frame 34 is placed inside the simulation cavity 1 to help fix the feeding conduit 32, so that the grout outlet of the feeding conduit 32 is suspended in the air. The support ring frame 34 is arranged in a ring around the grout outlet of the feeding conduit 32, and also forms a barrier steel column located at the grout outlet to simulate the interference and flow bypass effect of the steel reinforcement obstacles in the actual plate cavity on the SCC flow path.

[0049] Specifically, the material supply control component 33 controls the injection rate by adjusting the size of the feeding funnel 31, so as to simulate the injection speed under different pumping or injection process conditions in actual construction.

[0050] As another embodiment of the present invention: refer to the appendix Figure 3 The groove 300 is provided with a lifting base plate 6, and the lower end of the lifting base plate 6 is provided with a scissor lifting mechanism 7. The scissor lifting mechanism 7 drives the lifting base plate 6 to move up and down so as to adjust the depth of the groove 300.

[0051] One implementation of the pressure sensing array 4: see attached... Figure 6 The pressure sensor array 4 includes multiple thin-film pressure sensors 41, which are embedded in the inner surfaces of the upper cover plate 11, the lower bottom plate 12 and the side plate 13 of the simulation cavity 1. The thin-film pressure sensors 41 are connected to the control system 2 in communication. The thin-film pressure sensors 41 are used to collect pressure changes at various locations during the injection of SCC in real time, and to monitor the pressure gradient decay and the formation of local micro-high pressure zones.

[0052] In another embodiment of the present invention: the thin film pressure sensors 41 on each side plate 13 are connected in series by a first data line 42, and each side plate 13 is provided with a wire hole 400 for the second data line to pass through. The thin film pressure sensors 41 are connected to the control system 2 through the first data line 42 and the second data line. The thin film pressure sensors 41 on the upper cover plate 11 and the lower bottom plate 12 are divided into multiple groups. Each group of thin film pressure sensors 41 is connected in series to the first data line 42 on its adjacent side plate 13.

[0053] Specifically, the thin-film pressure sensors 41 are arranged at certain intervals along the radial and circumferential directions to collect pressure changes at various locations during the SCC grouting process in real time. In this embodiment, the thin-film pressure sensors 41 are arranged radially from the grouting hole 500 with a pressure measuring point every 100mm to 200mm, and circumferentially with pressure measuring points at the middle of the long side, the middle of the short side, and the four corners to monitor the local micro-high pressure zone of the arch-shaped depression.

[0054] As another embodiment of the present invention: an adjustable exhaust valve 8 is provided at the exhaust port 100, and the exhaust valve 8 is used to control the outlet back pressure of the exhaust port.

[0055] In another embodiment of the present invention, the inner surface of the side plate 13 is provided with breathable geotextile, and the inner surface of the bottom plate 12 is also provided with breathable geotextile. This structural design is used to simulate the boundary conditions of templates made of different materials in actual construction. Specifically, the inner surface of the long side plate 13 is lined with breathable geotextile to simulate the breathable boundary conditions of the inner wall of the long template in actual construction, and the inner surface of the short side plate 13 is provided with coatings of different roughness to simulate the short side boundary conditions of different materials.

[0056] One implementation of the vision mechanism 5: Refer to the appendix Figure 5 The vision mechanism 5 includes a camera 51 and a light source bar 52. The light source bar 52 is located on one or both sides of the simulation cavity 1. The camera 51 is communicatively connected to the control system 2. The light source bar 52 is used to illuminate from the side to enhance the contrast between the bubbles and the slurry and improve the bubble recognition accuracy. The present invention records the flow morphology and surface bubble migration trajectory of SCC in real time during the injection process through the camera 51.

[0057] Specifically, the light source strip 52 is an LED strip light source, and the emitted beam enters the cavity of the plate cavity parallel to the side, using the difference in refractive index between the bubble and the slurry to enhance the recognizability of the bubble outline. The camera 51 is a high-speed camera with a frame rate of no less than 60fps and a resolution of no less than 1920×1080.

[0058] Specifically, the spacing between the upper cover plate 11 and the lower bottom plate 12 is adjustable to simulate cavities with different thicknesses of filling layers, allowing for systematic study of the influence of different cavity clearance heights on the evolution of the SCC flow front, pressure distribution, and bubble retention behavior on the same device.

[0059] As another embodiment of the present invention: the control system 2 further includes an image processing subsystem, which is used to perform binarization processing on the flow image acquired by the camera 51, extract the contour coordinates of the flow front, calculate the bow-shaped indentation depth of the flow front, and count the number and size distribution of trapped bubbles in the plate end region.

[0060] Specifically, the top cover 11 is made of high-transmittance acrylic glass (PMMA).

[0061] This invention also provides a method for evaluating the injectability of SCC, comprising the following steps:

[0062] S1: Inject the mixed SCC into the simulated cavity 1 through the injection mechanism 3;

[0063] S2: The flow process of SCC within the simulated cavity 1 is recorded using camera 51, yielding the depth D of the arc-shaped indentation of SCC. bow Then calculate the bow-shaped concavity coefficient K. bow = , where L short The length of the short side plate 13 of the simulated cavity 1;

[0064] Among them, refer to the appendix Figure 7 The flow process of SCC within the simulation cavity 1 includes: an initial radial expansion stage, a contact wall reversal stage, a flow front distortion stage, a groove passage stage, and a plate end reverse confluence stage. Specifically, in the initial radial expansion stage—after entering the simulation cavity 1 through the grouting hole 500, the SCC initially spreads radially under the combined action of gravity and injection pressure. Since the SCC has not yet filled the simulation cavity 1 in the thickness direction, the flow is characterized by a radial thin-layer flow with the lower interface constrained and the upper surface being a free boundary. As the SCC continues to be injected, the SCC around the grouting hole 500 first fills the local space in the thickness direction, and the flow pattern changes to a restricted shear flow constrained by both the upper and lower interfaces; in the contact wall reversal stage—when the SCC flow front first reaches the side wall of the long side plate 13, it encounters the side wall constraint, and the main flow is forced to turn and move tangentially along the side wall. Images captured by camera 51 clearly show a sharp decrease in flow velocity near the sidewall, forming a lateral low-velocity zone. Simultaneously, it can be observed that bubbles in this low-velocity zone rise to the upper surface of the filling layer and remain in the edge region. The middle of the long side plate 13 has the shortest lateral migration distance and therefore the most accumulated bubbles. During the flow front distortion stage—due to severe obstruction of the SCC flow in the width direction but relatively less obstruction in the length direction within the simulation cavity 1—the SCC flow front gradually evolves from an approximately circular shape to an elliptical shape, eventually forming an arched front with concave ends in the length direction. The control system 2 automatically extracts the flow front contour coordinates from the captured images and calculates the arched concavity depth D of the arched front. bowThe process begins with the flow of slurry through the groove stage. The slurry in the middle flows into the groove 300 area, while the slurry on both sides preferentially advances towards the shorter side plate 13 (the side plate 13 furthest from the grouting hole 500). When the bow-shaped leading edge reaches the groove 300, the SCC in the middle preferentially flows into the groove 300 area and completes filling, with a local deflection of the flow direction and the consumption of some kinetic energy. Meanwhile, the adjacent slurry on both sides, not encountering the groove 300, maintains a higher flow velocity and continues to extend towards the plate end (towards the slurry discharge hole 200), preferentially reaching the slurry discharge hole 200. In the reverse confluence stage at the plate end, the SCC portions that preferentially reach the slurry discharge hole 200 on both sides slowly overflow. The remaining unoverflowed portions change direction after encountering the constraint of the short side plate 13, moving along the inner wall towards the middle of the side plate 13. The SCC that advanced in the middle and was affected by the filling of the groove 300 flows to the short side plate 13 after completing the filling of the groove 300, and is forced to divert towards the slurry discharge holes 200 on both sides. Two opposing slurry flows meet in the middle region of the plate end (side plate 13), creating a countercurrent confluence effect, which drastically reduces the horizontal flow velocity, forming a low-velocity zone at the end. Within the region where side plate 13 is located, it can be clearly observed that after bubbles rise to the upper surface of the simulated cavity 1, they cannot continue to migrate with the slurry flow to the slurry discharge hole 200, thus accumulating and remaining in large quantities.

[0065] S3: The pressure values ​​at each monitoring point are collected in real time through the pressure sensor array 4, and the following characteristics are observed: (1) the pressure gradient decay curve along the radial direction, which is used to evaluate the flow resistance of SCC under the constraints of the upper and lower interfaces; (2) the local pressure peak in the arc-shaped depression area, which is used to determine the formation location and intensity of the triangular micro-high pressure zone; (3) the stable trend of the pressure value in the middle region of the short side plate 13 during the reverse flow stage at the plate end, which is used to determine the degree of flow stagnation. Specifically, in the flow front distortion stage, when the SCC flow front contacts the inner wall of the long side plate 13, the control system 2 automatically extracts the flow front contour coordinates and calculates the arc-shaped depression depth D in real time. bow Then calculate the bow-shaped concavity coefficient K. bow When K bow When the value exceeds a preset threshold of 0.12, the system issues a real-time warning that "the bow-shaped depression is too large, posing a risk of unfilled corners," guiding on-site adjustments to the injection speed or mix ratio. The outer contour of the bow-shaped leading edge is arc-shaped, and the depth of the bow-shaped depression is the arc-shaped groove depth.

[0066] The local peak pressure P is obtained through pressure sensor array 4. max and pressure stability value P steady Calculate the pressure drop ΔP = P steady - P max Among them, P max The maximum pressure, P, is collected by the pressure sensing array 4 before the side plate 13 at the end of the SCC flow front contact simulation cavity 1 away from the infusion mechanism 3. steadyThe pressure sensor array 4 collects the stable pressure value in the plate end region during the reverse merging phase;

[0067] S4: Based on the final SCC coverage area image acquired by camera 51, the actual coverage contour of the SCC is extracted by the control system 2, and the actual coverage area A is calculated. actual Calculate the filling coefficient F of the plate cavity. A cavity The design filling area of ​​the simulated cavity 1 is given. In this step, F reflects the ultimate spreading ability of SCC under multiple constraints and directional resistance conditions. The closer F is to 1, the stronger the filling ability of SCC.

[0068] S5: Based on high-definition images acquired from the central region of the plate end (within 200mm of the shorter side plate at point 13), the control system 2 identifies and counts the number N of trapped air bubbles. bubble Calculate the equivalent diameter of each bubble to obtain the average diameter D. avg Simultaneously, the end overflow velocity V was calculated using particle velocimetry based on the image sequence. end Calculate the end bubble retention index B = V end The end overflow velocity (the overflow velocity of the slurry discharge hole 200); in this step, B reflects the severity of air bubble retention in the middle region of the plate end. The larger the B value, the easier it is for air bubbles to accumulate and remain in this region.

[0069] S6: Utilize K from step S2 bow And P in S3 max ΔP is used to correct F and B, resulting in the corrected filling coefficient F1 and the corrected bubble retention index B1. The injectability of SCC is then evaluated based on the values ​​of F1 and B1: when F1 ≥ 0.95 and B1 ≤ 0.5 mm... -1 If the slump is within the acceptable range, the SCC mix proportion is deemed acceptable for grouting quality; otherwise, it is deemed unacceptable, and the SCC mix proportion or grouting process needs to be adjusted. Specifically, when F1 < 0.95, it indicates insufficient filling capacity of the SCC, requiring adjustment of the mix proportion (such as increasing slump spread, reducing yield stress) or increasing the grouting pressure; when B1 > 0.5mm... -1 When the SCC is in the plate end area, it indicates that there is a serious risk of air bubble retention, and it is necessary to adjust the mix ratio (such as reducing plastic viscosity and adding defoamer) or optimize the grouting process (such as adding vent hole 100 and adjusting the opening of grout discharge hole 200). In this step, the influence of process dynamic effects on the final state evaluation index is eliminated by correction, thereby improving the accuracy of the judgment.

[0070] In step S6, the filling coefficient F1 is calculated using the following formula:

[0071] F1 = F × (1 - α·K bow )

[0072] Wherein, α is an empirical coefficient, with a value ranging from 0.5 to 0.8. In this embodiment, based on a large number of experimental statistics, α is set to 0.65.

[0073] The filling coefficient correction mechanism is as follows: the deeper the bow-shaped depression (K) bow The larger the value of F, the more pronounced the triangular micro-high pressure zone on both sides of the bow-shaped leading edge. Air is difficult to expel from this area, and the resulting unfilled voids directly reduce the actual effective filling area. Therefore, F needs to be multiplied by a penalty factor (1 - α·K). bow This is to reflect the loss.

[0074] In step S6, the bubble retention index B1 is calculated using the following formula:

[0075] B1 =

[0076] Where β and γ are empirical coefficients, P ref The reference pressure is 1000 Pa; β ranges from 0.2 to 0.4, and γ ranges from 0.3 to 0.6. In this embodiment, based on extensive experimental statistics, β = 0.3, γ = 0.45, and P... ref =1000 Pa.

[0077] The correction mechanism for the bubble retention index lies in: the local peak pressure P max The higher the value, the more severe the compression of bubbles in the arched concave region, with more bubbles being driven to the low-pressure area at the plate end, leading to an increase in the number of bubbles at the end. The larger the pressure drop |ΔP|, the more drastic the velocity drop during reverse flow at the plate end, the weaker the ability of the slurry to carry bubbles towards the discharge port, and the easier it is for bubbles to float and remain. Therefore, B needs to be multiplied by two factors greater than 1 for positive correction.

[0078] As another embodiment of the present invention: after the SCC flow front contacts the inner wall of the long side plate 13, the flow front profile coordinates are extracted at fixed time intervals (e.g., every 2 seconds) to calculate the bow-shaped indentation depth D. bow When the bow-shaped concavity coefficient K bow When the flow velocity exceeds the preset threshold of 0.12, it indicates that the difference between the length and width directions of the SCC flow is too large, resulting in insufficient directional following. The triangular micro-high pressure zone in the arc-shaped concave area will hinder air discharge, and an early warning should be issued. This warning can be triggered in real time during the injection process to guide on-site adjustments to the injection speed or venting scheme.

[0079] As another embodiment of the present invention: when P maxWhen the pressure exceeds 1500 Pa or ΔP is below -1000 Pa, an end bubble retention risk warning is issued, and it is recommended to adjust the injection rate or venting scheme.

[0080] As another embodiment of the present invention: before step S1, the following steps are also included: according to the SCC mix ratio to be evaluated, adjust the thickness of the simulated cavity 1, the lining material of the side plate 13, and the depth of the groove 300 to make them consistent with the actual construction conditions; specifically, the following parameters can be set: (1) adjust the distance between the upper cover plate 11 and the lower bottom plate 12 to make it equal to the design thickness of the actual filling layer; (2) install geotextile with corresponding roughness and air permeability according to the actual template material; (3) adjust the depth of the groove 300 through the scissor lifting mechanism 7 according to the actual limit groove size; (4) set the injection pressure value of the pressure control component of the injection mechanism 3 according to the actual injection process; (5) adjust the opening of the exhaust valve 8 to simulate the overflow resistance conditions of the actual exhaust port.

[0081] As another embodiment of the present invention: after step S6, the following step is further included: the output includes F1, B1, D bow The complete test report, including pressure gradient decay curves, flow front evolution image sequences, and bubble distribution thermograms, provides a scientific basis for SCC mix optimization and injection process parameter determination.

[0082] This invention is applicable to the preliminary assessment and mix ratio optimization of SCC grouting quality in narrow slab cavity structures such as the filling layer of slab structure for high-speed railway ballastless track and the grouting connection layer of prefabricated buildings.

[0083] Beneficial effects of this invention:

[0084] Compared with the prior art, the present invention has the following beneficial effects:

[0085] (1) The flow field evolution of the entire actual grouting process was reproduced, and in particular, the simulation capability of the reverse confluence and counter-current effect at the plate end was proposed. By simulating the geometry of the narrow plate cavity, the friction of the upper and lower interfaces, the air permeability of the sidewalls and the groove structure, this device can not only reproduce the entire process of SCC from initial radial expansion, contact with the sidewalls to change direction and deceleration, the formation of the bow-shaped leading edge and the passage through the limiting groove, but also accurately reproduce the complex coupling process that the slurry on both sides first arrives at the end and then turns back, forming a counter-current with the slurry that arrives later in the middle, which cannot be simulated by existing devices, by reasonably arranging the slurry discharge / air hole positions and controlling the slurry overflow sequence.

[0086] (2) It realizes the full-process visualization tracking of bubble behavior and the synchronous monitoring of local flow field pressure. Through the transparent cavity design, side plate light source illumination and high-speed image acquisition, the complete trajectory of the bubble from entrainment and migration, lateral aggregation, residence in the bow-shaped area and final retention at the end can be clearly observed; at the same time, through the integrated pressure sensor array, the pressure gradient decay curve and the pressure peak of the bow-shaped concave triangular micro-high pressure area during the injection process are acquired in real time, providing direct image and quantitative data dual evidence for the hydrodynamic mechanism analysis of bubble retention.

[0087] (3) A quantitative evaluation index system directly corresponding to the grouting physical mechanism was established. New evaluation indexes such as “plate cavity filling coefficient F1” and “end bubble retention index B1” were proposed to characterize the ultimate spreading ability of SCC under multi-constraint directional resistance and the severity of bubble retention in the end low-speed zone, respectively. Compared with the single collapse expansion degree or height difference ratio index in the existing technology, it has stronger working condition targeting and quality prediction accuracy.

[0088] (4) A complete technical closed loop of "process observation → parameter extraction → model correction → final state determination" has been formed, and it has a real-time early warning function. This invention uses the bow-shaped indentation coefficient K obtained in real time during the injection process. bow Local peak pressure P max The pressure drop ΔP is used as a correction factor and introduced into the calculation of the final state evaluation indexes F1 and B1 to achieve accurate prediction of groutability. At the same time, by setting the threshold of the above parameters, abnormal flow states can be identified and early warnings can be issued in real time during the grouting process, providing a dynamic control method for on-site construction.

[0089] The key terms in this invention are defined as follows:

[0090] Narrow plate cavity: refers to a plate-shaped cavity similar to the filling layer in a slab track structure, whose thickness is much smaller than the dimensions in other directions in the plane. Here, the thickness range is taken as 75mm~150mm.

[0091] Lateral low-velocity region: The region where the flow velocity drops sharply after the SCC flow front contacts the sidewall of the long side plate 13 due to flow direction deflection and sidewall friction resistance, located near the inner side of the long side plate 13.

[0092] Bow-shaped front: During the expansion of SCC, the flow front exhibits a bow-shaped shape with both ends concave backward due to the difference in flow resistance in various directions.

[0093] Low-velocity zone at the end: In the middle region of the plate end, the slurry that first reaches the discharge hole 200 from both sides is turned back along the short side plate 13 and meets the slurry that arrives later in the middle, forming a reverse flow, which leads to a sharp decrease in flow velocity in this region.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A visual simulation device for bubble retention in a plate cavity, characterized in that, The device includes a simulation cavity and a control system. The upper cover of the simulation cavity is made of transparent material and is connected to an injection mechanism. The end of the simulation cavity away from the injection mechanism is provided with an exhaust port and a slurry discharge port. The slurry discharge port is located on both sides of the simulation cavity. The bottom of the simulation cavity is provided with a groove. A pressure sensor array is provided inside the simulation cavity. A vision mechanism is provided above the simulation cavity. The control system is communicatively connected to the vision mechanism and the pressure sensor array, respectively.

2. The plate cavity bubble retention visualization simulation device according to claim 1, characterized in that, The injection mechanism includes a feeding funnel and a feeding conduit. The feeding funnel is connected to the feeding conduit, which extends into the simulated cavity. The lower end of the feeding conduit is connected to a support ring frame, which is placed inside the simulated cavity. The feeding conduit is equipped with a feeding control component.

3. The plate cavity bubble retention visualization simulation device according to claim 2, characterized in that, The pressure sensing array includes multiple thin-film pressure sensors, which are embedded in the inner surfaces of the upper cover plate, lower bottom plate, and side plate of the simulated cavity, respectively. The thin-film pressure sensors are communicatively connected to the control system.

4. The plate cavity bubble retention visualization simulation device according to claim 3, characterized in that, The thin-film pressure sensors on each side plate are connected in series via a first data line. Each side plate has a wire hole for a second data line to pass through. The thin-film pressure sensors are connected to the control system via the first and second data lines. The thin-film pressure sensors on the upper cover plate and the lower bottom plate are divided into multiple groups. Each group of thin-film pressure sensors is connected in series to the first data line on its adjacent side plate.

5. The plate cavity bubble retention visualization simulation device according to claim 1, characterized in that, The vision mechanism includes a camera and a light source bar, the light source bar being located on one or both sides of the simulation cavity, and the camera being communicatively connected to the control system.

6. A method for evaluating the SCC (Self-Cavity Cavity Air Bubble Retention) perfusionability, comprising the plate cavity air bubble retention visualization simulation device according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Inject SCC into the simulated cavity through the infusion mechanism; S2: The flow process of SCC within the simulated cavity is recorded using a camera to obtain the depth D of the SCC's arch-shaped indentation. bow Then calculate the bow-shaped concavity coefficient K. bow = L short This is to simulate the width of the shorter side of the cavity; S3: The pressure values ​​at each monitoring point are collected in real time through a pressure sensor array to obtain P. max and P steady Calculate the pressure drop ΔP = P steady - P max , where P max P is the maximum pressure collected by the pressure sensing array before the SCC flow front contacts the side plate of the simulated cavity away from the infusion mechanism. steady The stable pressure value collected in the plate end region during the reverse flow phase; S4: Calculate the cavity filling coefficient F= A actual A represents the actual coverage area of ​​the SCC. cavity The design filling area of ​​the simulated cavity; S5: Based on the images captured by the camera, obtain the number N of trapped bubbles. bubble and average diameter D avg Calculate the end bubble retention index B = V end The end overflow velocity; S6: Utilize K from step S2 bow And P in S3 max ΔP is used to correct F and B, resulting in the corrected filling coefficient F1 and the corrected bubble retention index B1. Then, the injectability of SCC is evaluated based on the values ​​of F1 and B1: when F1 ≥ 0.95 and B1 ≤ 0.5 mm... -1 If the SCC mix ratio is within acceptable limits, the grouting quality is deemed qualified; otherwise, it is deemed unqualified, and the SCC mix ratio or grouting process needs to be adjusted.

7. The SCC irrigationability assessment method according to claim 6, characterized in that, In step S6, the filling coefficient F1 is calculated using the following formula: F1= F × (1 - α·K bow ) Where α is an empirical coefficient, with a value ranging from 0.5 to 0.

8.

8. The SCC irrigationability assessment method according to claim 6, characterized in that, In step S6, the bubble retention index B1 is calculated using the following formula: B1 = Where β and γ are empirical coefficients, P ref The reference pressure is 1000 Pa; the value of β ranges from 0.2 to 0.4, and the value of γ ranges from 0.3 to 0.

6.

9. The SCC irrigationability assessment method according to claim 6, characterized in that, In step S2, the bow-shaped concavity coefficient K bow When the value exceeds the preset threshold of 0.12, it is determined that the SCC has insufficient following ability in changing flow, and there is a risk of trapped air, and a real-time warning is issued.

10. The SCC irrigationability assessment method according to claim 6, characterized in that, In step S3, when P max When the pressure exceeds 1500 Pa or ΔP is below -1000 Pa, an end bubble retention risk warning is issued, and it is recommended to adjust the injection rate or venting scheme.

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