A method for repairing and reinforcing cement concrete pavement

Abstract

The present invention discloses a method for repairing and reinforcing cement concrete pavements, relating to the technical field of cement concrete pavement repair. Based on the fundamental principles and laws of flow and diffusion of polymer grouting materials and the influence of temperature changes on polymer viscosity and density parameters, the present invention designs a finite element simulation model and an indoor visualization test model for cement pavement voiding. Furthermore, based on the influence of environmental factors on the flow and diffusion of single-source polymers, the multi-source diffusion law of polymers is determined, allowing for precise determination of the optimal grouting volume, thereby increasing the pavement's service life and reducing the pavement loss rate, thereby minimizing resource waste.

Description

Technical Field

[0001] The present invention relates to the technical field of cement concrete pavement repair, and in particular to a method for repairing and reinforcing cement concrete pavement. Background Art

[0002] Cement concrete, a semi-rigid material, offers high strength, high bearing capacity, and excellent water stability. Furthermore, due to the abundant reserves, low price, and extensive application experience of inorganic binders in my country, semi-rigid materials will continue to be the primary base material. However, during the use of cement pavement slabs, the repetitive effects of traffic loads will cause the cement-stabilized base beneath the slab to undergo some plastic deformation. Furthermore, due to thermal stresses, the cement pavement slab will experience some warping, resulting in partial discontinuity or delamination at the interface between the slab and the base. Under the combined effects of traffic loads, rainfall, and structural free water, cement pavement slabs inevitably experience scouring and mud pumping. As repeated loads and water erosion intensify, varying degrees of voids will develop under the cement pavement slab. If these voids are not promptly addressed, traffic loads will cause stress concentrations at the edges of the voids, gradually leading to breakage, misalignment, and joint fractures. This can severely impact traffic quality and pose a significant safety hazard. Furthermore, in recent years, frequent extreme natural disasters have impacted pavements, such as floods and debris flows, severely damaging the roadbed and causing a high incidence of hidden pavement defects. Frequent and lengthy maintenance tasks have created new challenges for pavement accessibility. Therefore, a repair and reinforcement method specifically targeting pavement void defects is needed to repair and reinforce pavements, prevent traffic accidents, and minimize the impact of natural disasters on pavement life. Summary of the Invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for repairing and reinforcing cement concrete pavements, which solves the problem of the lack of a repair and reinforcement method for cement pavement hollowing diseases.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0005] A method for repairing and reinforcing a cement concrete pavement is provided, comprising the following steps:

[0006] S1. Obtain the void range corresponding to the cement concrete pavement to be repaired;

[0007] S2. Obtaining the load conditions and temperature stress of the cement concrete pavement to be repaired;

[0008] S3. Use the void gap thickness calculation and analysis method to process the void range, load conditions and temperature stress to obtain the corresponding void volume;

[0009] S4. Based on the void volume, the finite element simulation method is used to simulate the cement concrete pavement to be repaired and the multi-source diffusion law of polymer is obtained;

[0010] S5. Based on the multi-source diffusion law of polymers, the indoor model test results and law analysis of the gap-removing polymer reinforcement of the cement concrete pavement to be repaired are carried out to obtain the safe grouting range;

[0011] S6. Based on the safe grouting range, the finite element simulation model of the dynamic response of the polymer repaired cement pavement is used to process and analyze the cement concrete pavement to obtain the optimal grouting amount;

[0012] S7. Repair the cement concrete pavement to be repaired according to the optimal grouting amount.

[0013] The beneficial effects of the present invention are as follows: based on the basic principles and laws of flow and diffusion of polymer grouting materials and the influence of temperature changes on the viscosity and density parameters of polymers, this method designs a finite element simulation model of cement pavement void disease and an indoor visualization test model, and according to the influence of environmental factors on the single-source flow and diffusion of polymers, determines the multi-source diffusion law of polymers, accurately determines the optimal grouting amount, increases the service life of the pavement, reduces the pavement loss rate, and thus reduces resource waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the flow chart of the method;

[0015] Figure 2 is the vehicle weight frequency distribution diagram;

[0016] Figure 3 is the curve diagram of the influence of vehicle speed on the maximum vertical displacement;

[0017] Figure 4 The load-deflection curve of cement concrete pavement slab with void damage is shown in Figure 2.

[0018] Figure 5 This is a schematic diagram of the morphological curve of the hollowing disease;

[0019] Figure 6 is a graph showing density changing with time;

[0020] Figure 7 is a graph showing viscosity changing with time;

[0021] Figure 8 is a schematic diagram of the geometric structure;

[0022] Figure 9 Set up schematic diagrams for boundary conditions;

[0023] Figure 10 This is the indoor visualization test model diagram;

[0024] Figure 11 Schematic diagram of the diffusion morphology of polymer in horizontal gap;

[0025] Figure 12 This is the diffusion radius comparison result diagram;

[0026] Figure 13 This is the effect curve of roughness coefficient JRC and density on shear strength;

[0027] Figure 14 This is a curve diagram showing the influence of vertical pressure on shear strength. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0029] like Figure 1 As shown, a method for repairing and reinforcing a cement concrete pavement comprises the following steps:

[0030] S1. Obtain the void range corresponding to the cement concrete pavement to be repaired;

[0031] The method for obtaining the void range can adopt a BP-based cement concrete pavement void range identification method, which includes the following steps:

[0032] A1. Obtaining the slab data of the cement concrete pavement to be identified;

[0033] A2. Perform deflection detection on the cement concrete pavement to be identified and obtain corresponding deflection data;

[0034] A3. Measure the surface temperature of the cement concrete pavement to be identified;

[0035] The cement concrete pavement was analyzed using a finite element fluid-solid coupling simulation model of void disease, which consists of the FLUNENT fluid analysis module and the TRANSIENT STRUCTURE transient structural analysis module. The corresponding void disease influencing mechanism was obtained, that is, the inherent mechanism by which traffic load and water erosion affect the development of void disease was analyzed. A full-scale test section of the pavement was conducted to analyze the impact of temperature on void disease at the top, middle, bottom and base layers of the slab. There is a direct link between deflection data and void defects. Based on temperature influences and inherent mechanisms, the relationship between deflection values ​​and indicators such as temperature gradient, pavement slab modulus, base modulus, soil subgrade modulus, pavement slab thickness, pavement slab size, void size, and base subgrade thickness was analyzed. Based on the analysis results, deflection values, as well as temperature gradient, pavement slab size, pavement slab modulus, base subgrade modulus, and foundation modulus with correlations greater than 0.85, were selected as feature values. Specifically, surface temperature data, pavement slab data, and deflection data were selected as inputs for the subsequent BP neural network, while void size (void range) was selected as the output. Selecting data with a higher correlation with deflection values ​​can capture deeper features and improve the accuracy of void range identification.

[0036] A4. Construct a road surface clearance identification model;

[0037] The pavement clearance recognition model adopts a BP neural network model, which includes an input layer, a hidden layer, and an output layer connected in series. Each layer includes multiple neuron nodes, and the neuron nodes are connected by connection weights. The activation function of the output layer adopts the Purelin function; the activation function of the hidden layer adopts the Tasnsig function; the number of neuron nodes J in the hidden layer is based on the formula:

[0038]

[0039] Determine; where a represents the neuron node of the input layer, b represents the neuron node of the output layer, and c represents a constant.

[0040] A5. The pavement panel data, deflection data, and surface temperature data are normalized and input into the pavement void identification model to obtain the corresponding void range.

[0041] A5-1. Obtain road panel training data and deflection training data;

[0042] The process of obtaining the deflection training data in step A5-1 includes the following steps:

[0043] The falling weight deflectometer (FWD) method is used to treat the pavement with known deflection range, and the deflection basin changes of different pavement structures under the action of FWD load. The actual falling weight deflectometer with a load plate of 300mm diameter is used, such as Figure 2 As shown in the figure, for the plate corners, the deflection load is applied at a position where the center of the loading plate is 25 cm away from the plate edges on both sides; for the plate edges, the deflection load is applied at the middle of the plate edge with the center of the loading plate 25 cm away from the plate edge. The corresponding deflection data, i.e., the deflection training data, is obtained.

[0044] A5-2. Conduct full-scale road tests on the pavement to obtain the corresponding temperature field distribution pattern;

[0045] Step A5-2 includes the following steps:

[0046] A5-2-1. Install four layers of temperature sensors on the road surface, on the top, between, and bottom of the slabs, and on the base of the road surface. Each layer of sensors is located at the four slab corners and in the middle of the slab. Install one temperature sensor on the road surface to monitor the atmospheric temperature.

[0047] A5-2-2. Temperature data is collected through various temperature sensors and classified according to the seasons of spring, summer, autumn, and winter to obtain classified temperature data. For example, for road surfaces, the classified temperature data includes spring, summer, autumn, and winter road surface temperature data. The slab tops, interslabs, slab bottoms, and base layers are classified in the same manner. March, April, and May are considered spring, June, July, and August are considered summer, September, October, and November are considered autumn, and December, January, and February are considered winter.

[0048] A5-2-3. Analyze the classified temperature data to obtain the corresponding temperature distribution pattern;

[0049] The temperature distribution formula in step A5-2-3 is:

[0050]

[0051] Among them, T a,i represents the temperature of the i-th species, represents the daily average temperature of the i-th species, T m,i represents the daily temperature variation of the i-th type, T max,i represents the maximum daily temperature of the i-th type, T min,i represents the minimum daily temperature of the i-th type, sin(·) represents the sine function, t i represents the phase of the i-th species, t 0,i represents the initial phase of the i-th species, ω(t i ),ω(t i -t 0,i ) represent the phase t of the i-th type respectively i , the phase difference is t i -t 0,i The corresponding angular frequency;

[0052] A5-2-4. Construct an unsteady temperature field based on temperature distribution, heat transfer mode, energy conservation principle, and Fourier's law.

[0053] The formula for the unsteady temperature field in step A5-2-4 is:

[0054]

[0055] Among them, T i represents the temperature of the i-th microunit, t represents the time, represents the partial derivative of the temperature of the i-th micro-unit, ρ represents the density of the micro-unit material, C represents the specific heat capacity of the micro-unit material, represents the partial derivative, x i 、y i 、z i They represent the heat increment of the i-th micro unit in the x, y, and z directions respectively; wherein the micro unit is a unit set at any position on the cement concrete pavement.

[0056] A5-2-5. Based on the first initial condition and the first boundary condition, the finite element method is used to solve the unsteady temperature field. The temperature field distribution of the pavement at the start of heat transfer and the heat transfer state at its boundary, i.e., the temperature field distribution law, are obtained. The first initial condition is the temperature distribution state within the pavement at time 0; the first boundary condition includes the first temperature boundary condition, the heat flux boundary condition, and the ambient heat exchange boundary condition.

[0057] S5-3. Construct a dynamic response forward analysis model; the dynamic response forward analysis model adopts a multi-layer finite element analysis model based on the Winkler foundation model theory;

[0058] A5-4. Based on the temperature field distribution law, the pavement panel training data and deflection training data are analyzed using the dynamic response forward analysis model to obtain the corresponding forward analysis sample library and its labels;

[0059] The analysis process in step A5-4 includes the following steps:

[0060] A5-4-1. Obtain the pavement's geometric parameters, material parameters, and the second temperature boundary condition;

[0061] A5-4-2. Input all the data in step S4-1 into the dynamic response forward analysis model;

[0062] A5-4-3. Unit grid division of cement concrete pavement to be identified;

[0063] A5-4-4. Calculate the temperature stress distribution of each unit grid;

[0064] A5-4-5. Calculate the stiffness matrix of each unit grid;

[0065] A5-4-6. Determine whether a unit grid is void based on the stiffness matrix of each unit grid; if so, modify the stiffness matrix of the unit grid; otherwise, retain the stiffness matrix of the unit grid; and proceed to step A4-7.

[0066] A5-4-7. Calculate the global stiffness matrix based on the data in step A4-6;

[0067] A5-4-8. Based on the overall stiffness matrix and temperature stress distribution, the dynamic response analysis of the cement concrete pavement to be identified is performed to obtain the node displacement value of each unit grid and the temperature value of the node at each time, that is, to obtain the forward analysis sample library.

[0068] A5-5. Input a set of sample data and their labels from the forward analysis sample library into the BP neural network model, and use the back propagation algorithm to adjust the weights and thresholds of the BP neural network model to obtain the BP neural network model after initial training;

[0069] A5-6. Repeat step A5-5 until each set of sample data is input into the BP neural network model to obtain a trained BP neural network model.

[0070] S2. Obtaining the load conditions and temperature stress of the cement concrete pavement to be repaired;

[0071] The load conditions include the geometric parameters, elastic modulus, Poisson's ratio, thermal conductivity, density, specific heat capacity, convection heat transfer coefficient of each structural layer of the mud concrete pavement, as well as the location, size, and moving load parameters of the void disease; temperature stress includes temperature gradient.

[0072] S3. Use the void gap thickness calculation and analysis method to process the void range, load conditions and temperature stress to obtain the corresponding void volume;

[0073] Cement concrete pavement voiding can generally be divided into two categories: absolute voiding and relative voiding. As deformation increases, the bottom of the pavement slab and the top surface of the base layer begin to contact and continue to deform together. When the load is removed, the pavement slab rebounds to its original position, and the top surface of the base layer in the voided area also rebounds to its original horizontal plane. Cement concrete pavement voiding is the result of the combined effects of long-term loads and hydraulic erosion. The extent of the void is related to the traffic load and the physical parameters of the pavement structure. When vehicles of different loads and axle numbers pass through the most unfavorable load position of the same voiding condition, the deformation of the pavement slab caused by lighter loads is insufficient to cause the bottom edge of the pavement slab to contact the top edge of the base layer. However, as the load increases, there is a threshold at which the bottom edge of the pavement slab contacts the top edge of the base layer. Therefore, selecting an appropriate traffic load is crucial to calculating the voiding condition clearance. During the application of traffic loads, in addition to the flexural deformation of the pavement slab in the voided area, the base layer in contact with the pavement slab also undergoes elastic deformation. When the load and the physical parameters of the road slab remain unchanged, the relative maximum vertical deformation of the slab remains unchanged. Greater elastic deformation of the base layer will result in a larger gap. Therefore, the influence of base layer deformation must be considered when calculating the gap thickness for gap defects. The maximum displacement value of the slab edge or corner calculated using appropriate calculation parameters is the theoretical maximum gap thickness for gap defects. Therefore, step S3 includes the following steps:

[0074] S3-1. Analyze load conditions and temperature stresses to determine the influence of traffic load weight, range, vehicle speed, and pavement temperature stress on the vertical displacement of the pavement slab.

[0075] The current vehicle weight distribution has changed from the standard mixed Weibull distribution to the trimodal distribution. The unimodal distribution can no longer fit the current vehicle weight distribution load well, and the traffic load distribution function can be regarded as a combination of different types of traffic loads, such as Figure 2 As shown, the trimodal distribution function can be seen as consisting of one extreme value type I and two normal distribution functions, wherein the extreme value type I distribution function is the light vehicle distribution function (I), and the medium vehicle (II) and heavy vehicle (III) are normal distribution functions. For cement concrete pavements of different working conditions, the distribution function of their traffic load is different. By statistically analyzing the traffic load of the cement concrete pavement to be repaired, the characteristic parameters of the distribution functions of the three types of vehicles are determined, and the vehicle weight frequency distribution diagram and distribution function equation of the relevant road section are constructed. In the present invention, the traffic load is simplified to a uniformly distributed lane load. Among them, the road traffic volume (pavement vehicle data, vehicle weight frequency of the relevant road section, load data) is obtained through the local Giti Transportation Department, or obtained through continuous field surveys.

[0076] A load shifting belt is set along the load movement direction. The width of the load shifting belt is the same as the outer wheel track, dividing the driving belt into n cells of width a. Taking the example of a traffic load occupying three cells, the movement of the traffic load is represented by eliminating the load in cell 1 and adding the load in cell 4. The driving speed is changed by changing the step time Δt. The formula for the driving speed is:

[0077] S car =a1Δt

[0078] [M]{δ″}+[C]{δ′}+[K]{δ}={F(t)}

[0079] Among them, S car represents the vehicle speed, a1 represents, [M], [C], [K] represent the mass matrix, damping matrix and stiffness matrix respectively, {δ″}, {δ′}, {δ} represent the acceleration, velocity and displacement vector respectively, and {F(t)} represents the resultant force matrix.

[0080] like Figure 3 As shown, in stage I, the maximum vertical displacement of the plate edge increases with increasing vehicle speed, with the fastest growth rate between 50 km / h and 108 km / h. When the vehicle speed reaches a critical value of 117.2 km / h, the influence of vehicle speed on the maximum vertical displacement reaches its maximum. When the vehicle speed exceeds the critical value, the maximum vertical displacement of the plate edge decreases with increasing speed, showing a downward trend. Because the calculation model takes inertia into account, when the moving load approaches, inertia hinders its movement, and when the moving load moves away, inertia hinders its recovery. However, under the moving load, the maximum vertical displacement of the plate edge is greater than the maximum vertical displacement in the static state.

[0081] When the top temperature of the slab is lower than the bottom temperature, the elongation of the upper material of the pavement slab is lower than that of the bottom material due to the linear expansion characteristics of the material. The edges and four corners of the slab are warped upward, and the slab is concave. At this time, the vertical displacement of the slab corners or edges under the dynamic load is calculated based on the warping, which increases compared to the vertical displacement when there is no temperature gradient.

[0082] When the top temperature of the slab is higher than the bottom temperature, the upper layer of the slab material elongates more than the lower layer, causing the center of the slab to arch upward and increasing stress on the edges and corners. Furthermore, as the extent of the void defect at the edge or corner increases, the contact point between the base layer and the slab shifts inward, causing the cantilevered portion of the slab above the void defect to bend downward due to thermal stress. A FORTRAN program was developed to perform calculations during the thermal stress process.

[0083] S3-2. Select the average value of the third peak of the distribution function of heavy vehicles as the calculation load;

[0084] S3-3. The maximum monthly average positive temperature gradient in a year is used to calculate the deformation caused by the temperature stress in the plate; the calculation method used is the forward modeling procedure.

[0085] S3-4. Based on the calculated load, deformation, and first temperature boundary condition, a three-dimensional model of the cement concrete pavement to be repaired is constructed using a multi-layer finite element analysis model based on the Winkler foundation model theory;

[0086] S3-5. Perform dynamic response analysis using a three-dimensional model of the cement concrete pavement to be repaired to obtain the node displacements at the slab edges and corners, i.e., the maximum thickness of the gap;

[0087] S3-6. Construct a morphological curve equation for the void disease, and solve it based on the maximum thickness of the void gap and the void range to obtain the corresponding void volume.

[0088] The cement concrete pavement to be repaired is simplified as a cantilever beam with a concentrated load P at the top. Based on the boundary constraints and the load, the deflection equation is solved to obtain the vertical displacement ν| of the beam end point under the load P. x-l,z-0 : Among them, x and z represent the transverse coordinate and the thickness coordinate respectively, l represents the void width of the cement concrete pavement to be repaired, J represents the section moment of inertia; P represents the concentrated force, and E represents the section stiffness.

[0089] The ratio of vertical displacement to load is proportional to the cube of the cantilever beam length, which means that in the load-deflection diagram drawn from the road slab void defect detection results, the greater the slope of the line connecting the detection point and the origin (the ratio of the central deflection value to the load), the larger the void area. Generally speaking, when the intercept of the linear regression line of the three deflection detection points and the vertical axis (central deflection value) is greater than 50, it is determined to be a void defect. Figure 4 As shown in the figure, the slope relationship of the three points is: k1>k2>k3; it can be seen that as the load increases, the deformation of the plate gradually increases, and the relative void area of ​​the plate gradually decreases. This is because during the deformation of the plate, some areas of the plate come into contact with the base layer and affect further deformation. As the load continues to decrease, the contact area also continues to decrease. When it decreases to the critical point, the void area at this time is the actual void area (slope k a ). When the load increases, the contact area also increases. When it increases to a certain extreme value, the gap between the gaps suddenly increases (affected by the scouring effect of water). Increasing the load will not increase the contact area. The trend line is infinitely close to the slope k b straight line.

[0090] Setting conditions:

[0091]

[0092] Since the deflection curve of the plate is a cubic function of x (the distance between the node and the edge of the void), the function is constructed:

[0093] f(x)=a2x 3 +b2x 2 +c2+cosex

[0094] Among them, a2, b2, and c2 represent coefficients;

[0095] After substituting the conditions into the function, the equation of the morphological curve of the gap removed in step S3-6 is obtained as follows:

[0096]

[0097] Where x represents the node of the cement concrete pavement to be repaired, f(x) represents the morphological curve of the void disease, d represents the void thickness of the cement concrete pavement to be repaired, l represents the void width of the cement concrete pavement to be repaired, cos represents the cosine function, and π represents pi;

[0098] like Figure 5 As shown, the morphological curves of the two examples obtained by the morphological curve equation are both "convex + concave" shapes, which are consistent with the actual situation and further verify the feasibility of the present invention.

[0099] The volume calculation of the slab edge void defect can be regarded as the product of the cross-sectional area and the side length of the slab, which is:

[0100] V b =S·k

[0101]

[0102] The solution is

[0103] The volume of the plate corner hollow disease is:

[0104]

[0105] Among them, V b represents the volume of the gap at the edge of the plate, S represents the cross-sectional area of ​​the road panel, k represents the side length of the road panel, d represents the thickness of the gap, l represents the width of the gap, π represents the circumference, cos represents the cosine function, x represents the node, ∫(·)dx represents the integral, V j It represents the void volume of the plate corners, and a3 and b3 represent the void lengths of the plate edges.

[0106] S4. Based on the void volume, the finite element simulation method is used to simulate the cement concrete pavement to be repaired and the multi-source diffusion law of polymer is obtained;

[0107] Polymer grouting material is a foaming non-water-reactive polyurethane polymer, and its molding mainly includes two processes: gel reaction and foaming reaction.

[0108] Step S4 includes the following steps:

[0109] S4-1. Analyze the influence of temperature on polymer parameters, including polymer viscosity and density.

[0110] A polymer was freely injected onto an acrylic plate using a grouting system to observe its reaction and curing process. Results show that the reaction and curing process of the polymer can be divided into two main stages: the free-flowing stage and the expansion-diffusion stage. In the free-flowing stage, gelation is dominant, resulting in low viscosity and easy flow, with a thickness typically exceeding 3 mm. In the expansion-diffusion stage, the slurry expands significantly over time due to the increase in bubbles. This indicates that the material's viscosity is increasing, and the lateral resistance in the horizontal direction is increasing. The material partially expands upward, overcoming gravity, and the temperature rises further. This indicates that the material's viscosity is increasing, the lateral resistance is increasing, and the partial upward expansion overcomes gravity, further increasing the temperature. This stage is driven by both gelation and foaming reactions. The exothermic reaction accelerates the foaming rate, leading to a rapid increase in volume and a significant decrease in density. Therefore, it is necessary to analyze the multi-source diffusion patterns of polymers based on the free-flowing and expansion-diffusion stages.

[0111] The density of polymers changes dynamically, and the density model can be considered to consist of three liquids (water, polyurethane raw material mixture, and physical foaming agent) and two gases (the foaming agent vaporized at high temperature and carbon dioxide generated by the reaction). The density changes during the polymer expansion process at different temperatures were measured. The material preheating temperature was set at 30°C, 40°C, and 50°C, and the ambient temperature was 25°C. The specific measurement steps are as follows:

[0112] ①Heat the two polymer raw materials to the preheating temperature;

[0113] ② Weigh 50g of each of the two raw materials into a graduated cylinder, record the liquid volume at this moment and stir rapidly;

[0114] ③Then record the volume every 5 seconds. When the material is liquid or there is no obvious bulge on the upper surface, the read volume is recorded as the actual volume of the material at this time. When the upper surface of the material has a clear spherical crown shape, according to the formula:

[0115]

[0116] Calculate the polymer volume V gWherein, V1 and V2 represent the volume read at the top and bottom of the foam arc, respectively.

[0117] ④When the volume no longer changes within 10 seconds, the test ends.

[0118] During the reaction expansion process, the polymer is initially a transparent brown liquid. As time progresses, dense bubbles gradually form, the volume expands rapidly, and within 1 minute it turns light yellow-white. No more volume increase marks the end of the reaction. As the preheating temperature increases, the rate of decrease in polymer density accelerates. When the temperature exceeds 40°C, the density of the solidified body no longer decreases; when preheated at 30°C, the density of the solidified body increases slightly, reaching 112kg / m 3 This indicates that the reduction of preheating temperature significantly affects the foaming reaction, resulting in a decrease in volume expansion rate. Figure 6 As shown in Figure 2, the density of polymers at different temperatures during the reaction and curing process changes with time, and the corresponding formula is:

[0119]

[0120] Among them, y m represents the polymer density, x m Indicates time.

[0121] Viscosity is used to describe the viscous resistance within a fluid and is a key parameter in fluid simulation. It reflects the interaction between fluid molecules and affects the fluid's flow properties under shear force. Its value represents the degree of fluid viscosity. The viscosity changes during the polymer reaction expansion process at different temperatures were measured using an SNB-2 viscometer. The temperature variables were set to 30°C, 40°C, and 50°C, and the speed was 60 r / min. The specific process was as follows:

[0122] ①Heat the two polymer raw materials to the preheating temperature;

[0123] ② Pour 50ml of each polymer raw material into the beaker and stir rapidly;

[0124] ③ Place the viscometer so that the rotor groove of the viscometer is level with the liquid surface;

[0125] ④ Turn on the viscometer to measure and record the data. When the viscosity value reaches 10 Pa·s, end the test.

[0126] like Figure 7As shown in the figure, the viscosity change during the reaction and curing process can be divided into two main stages: the initial stable stage and the later rapid growth stage. In the stable stage, the viscosity increases steadily and slowly, accounting for more than 80% of the entire reaction time; and as the temperature rises, the initial viscosity gradually increases, and the duration of this stage will also shorten. It is worth noting that when the reaction time threshold is reached, the viscosity change curve has an inflection point, and the viscosity rises sharply. The later rapid growth stage usually occurs within the last dozen seconds of the reaction. The fitting curve formula for the viscosity change of polymers at different temperatures during the reaction and curing process with time is:

[0127]

[0128] Among them, y n represents polymer viscosity, x n Indicates time.

[0129] In addition, polymer parameters also include rheological characteristics, which are used to construct finite element analysis models. The expansion and diffusion process of a polymer can be considered as fluid flow. Fluid motion states can be categorized as turbulent flow, transitional flow, and laminar flow. Flow states are typically determined by calculating the fluid's Reynolds number. In the present invention, the Reynolds number for the polymer during expansion and diffusion is 1727.5, so the finite element analysis model is constructed based on a laminar flow state.

[0130] S4-2. Determine the morphological characteristic parameters of the void disease on the cement concrete pavement to be repaired based on the void volume;

[0131] S4-3. Based on the influencing patterns of polymer parameters and the morphological characteristics of void defects, a finite element simulation model and an indoor visualization test model were constructed and analyzed to determine the influencing patterns of polymer single-source flow and diffusion. These influencing factors include temperature, inclination angle, water, roughness, gap thickness, and fixed boundaries.

[0132] Many factors influence the flow of slurry in degassing gaps, the main ones being gap opening (thickness), tilt angle, boundary conditions, roughness, and the presence of water. The finite element model utilizes FLUENT software to simulate the degassing gap. The visual indoor test model, constructed using acrylic panels, analyzes the flow of polymers using real-world grouting methods.

[0133] Because the expansion and diffusion process of polymer grouting is a complex physical and chemical process involving polymerization reactions, diffusion processes, and temperature fluctuations, the following key factors must be considered when developing a finite element simulation model: the reaction principle and system; density, viscosity, and temperature; diffusion mode: defining the diffusion mode of the polyurethane filling process—free or restricted; setting appropriate boundary conditions; and control conditions: setting model control conditions such as grouting rate, temperature, and reactant concentration. Selecting appropriate control conditions can enhance model accuracy and stability.

[0134] In the process of constructing the finite element simulation calculation model, the multiphase flow VOF model is used to simulate the interface movement and phase distribution in the multiphase fluid, and the finite volume method and PISO iterative algorithm are used.

[0135] The processing of the finite element simulation calculation model block is divided into model construction and meshing, UDF subroutine and model parameter setting.

[0136] In model construction and meshing, it is divided into geometric structure construction and grouting port setting, meshing, and boundary condition setting. For geometric structure construction and grouting port setting, the Space Claim module is used to construct a three-dimensional fluid finite element simulation geometric structure, and the Cartesian coordinate system is used by default. In order to weaken the influence of the free boundary on fluid diffusion, the size of the geometric structure is expanded to more than 2 to 3 times the fluid diffusion area. The basic geometric structure is a cube with parallel top and bottom surfaces. The side length of the diffusion area is 3.0m, and the gap thickness of the diffusion area is set to 8mm, 15mm, and 25mm, corresponding to slight voiding, moderate voiding, and severe voiding diseases, respectively. Figure 8 As shown. The geometric structure is dynamically adjusted according to different working conditions, such as changing the inclination or roughness of the bottom surface. A circular grouting hole with a diameter of 1.5 cm is set, which is consistent with the size of the grouting hole in actual engineering. In the simulation task, the relative position of the grouting port can be adjusted to meet the grouting requirements of different working conditions. For meshing, the simulation model is meshed according to the tetrahedron or hexahedron method, and the part near the grouting hole is encrypted. In order to ensure accuracy and convergence, the unit size is set to 8mm and the unit quality is not less than 0.85. For the boundary condition setting, the boundary condition setting is performed by naming the selected section in a standard way. The grouting hole of the geometric structure is set as the inlet, the upper and lower surfaces are set as the wall, and the surrounding surfaces are set as the outlet, as shown in the following figure. Figure 9 shown.

[0137] In the UDF subroutines, based on the results of polymer material parameter tests, the density and viscosity parameters of the polymer are set. Fluent's built-in compiler is used to read and apply these UDF subroutines to accurately assign material parameters within the model.

[0138] In the model parameter setting, the meshed geometric model was imported into FLUENT software for parameter configuration, using the "double precision" calculation mode. The VOF multiphase flow model was selected to simulate the injection process of polymer materials into air. Air was defined as the primary phase (water was the primary phase in simulations with ambient water) and the polymer as the secondary phase. The polymer fluid parameters were set using a UDF subroutine. Furthermore, to account for the influence of gravity, a vertical gravitational acceleration was applied. Based on the research results in the previous section, the viscosity model was determined to be a laminar flow model. The PISO strategy was used for the solution, and a second-order discretization method was applied.

[0139] For indoor visualization test models, such as Figure 10 As shown, the purpose of simulating different working conditions is achieved by dynamically adjusting different components. The indoor visualization test model includes rectangular steel pipes, acrylic plates, and pads; among them:

[0140] Rectangular steel tubes: Cold-drawn Q345B square steel tubes with a cross-section of 350mm x 500mm and a thickness of 2mm were used. Bolts were used to secure the acrylic sheet to prevent vertical displacement. Testing showed that the maximum deflection of the rectangular tubes was ≤1mm when the polymer was freely flowing and diffusing, indicating that the tubes could be considered fixed.

[0141] Acrylic Plate: A fully transparent acrylic plate measuring 1200mm x 2400mm x 25mm was selected. Its transparency facilitates observation of the entire polymer diffusion process. The acrylic plate consists of an upper plate and a lower plate. Multiple grouting holes are evenly spaced along the longitudinal axis of the upper plate, with each hole spaced 10cm apart. By adjusting the position of the grouting heads installed in these holes, multi-source grouting diffusion experiments can be performed.

[0142] Spacer: Use acrylic blocks with a width of 50 mm and simulate different gap thicknesses by changing the thickness (8 mm, 15 mm, 25 mm).

[0143] The main steps of the indoor model test for studying the free diffusion law of polymer slurry are as follows:

[0144] ①Install the bottom rectangular steel pipe and acrylic base plate;

[0145] ② Place a pressure film sensor just below the grouting hole and evenly lay a 1mm thick silicone pad on the pressure film sensor to prevent the polymer slurry from sticking to the pressure film sensor;

[0146] ④ Place pads of appropriate thickness according to the test conditions; install the acrylic top plate and grouting head, and install the top rectangular steel pipe in the corresponding position and fix it with bolts;

[0147] ⑤Connect the pressure film sensor and the receiver, and initialize the sensor through the computer;

[0148] ⑥ Install the grouting gun onto the grouting head, select the appropriate grouting amount and then start the grouting operation. At the beginning of grouting, record the pressure time course change of the pressure film sensor;

[0149] ⑦ Stop recording pressure data when the polymer stops diffusing. Wait 10 minutes, dismantle the model test device, and clean the polymer solidification body. After cleaning, start the next set of tests and return to step ③.

[0150] ⑧Clean up the test equipment, organize the test data, and end the test.

[0151] Taking parallel gap grouting as the basic background condition, the gap thickness is 15mm, the grouting temperature is 40℃, and the ambient temperature is 25℃. The diffusion radius and expansion pressure results of the injection of 0.50kg, 0.75kg and 1.00kg polymer slurry are compared and analyzed. Figure 11 and Figure 12 As shown, the diffusion of polymer in the horizontal degassing gap is circular, and the diffusion radius increases with the grouting volume. For grouting volumes of 0.50 kg, 0.75 kg, and 1.00 kg, the diffusion radius model test results are 0.45 m, 0.58 m, and 0.63 m, respectively, while the simulation results are 0.465 m, 0.569 m, and 0.658 m, respectively, with an average error of less than 5.0%.

[0152] Effect of Temperature on Single-Source Polymer Flow and Diffusion: The density of a polymer solid decreases with preheating and increasing ambient temperature, with a more pronounced pattern below 40°C. The viscosity and density curves of polymers can be divided into a steady phase and a rapidly changing phase. During the steady phase, viscosity increases slowly, while density increases inversely. This phase accounts for over 80% of the total reaction time. Increasing the preheat temperature causes a decrease in initial viscosity, and the duration of the steady phase also shortens. When the reaction time reaches a certain threshold, the viscosity and density of the polymer begin to increase and decrease exponentially, respectively. This rapid phase typically occurs within the last ten seconds. When the temperature is too low, the reaction rates of the gelation and foaming reactions differ significantly, resulting in polymer flow and diffusion relying on gravity and grouting pressure. The solidified body exhibits poor overall foaming, a small radius, and a color close to the dark brown of the raw material, but the overall material strength is high. When the temperature is too high, the foaming reaction is much faster than the gelation reaction, and the slurry quickly enters the expansion and diffusion phase after injection. In the later stage of the reaction, the edge material solidifies prematurely, and the foaming reaction is too fast, which leads to stress concentration at the edge of the solidified body and causes cracking of the solidified body.

[0153] Effect of gap thickness on single-source polymer flow diffusion: The expansion pressure of polymers within a free-plate gap follows a parabolic distribution along any axis, a quadratic function. Its maximum expansion pressure is inversely proportional to the square of the thickness and directly proportional to the grouting volume. The flow diffusion pattern is circular, with the average diffusion radius inversely proportional to the gap thickness and directly proportional to the grouting volume.

[0154] The effect of inclination angle on the single-source flow and diffusion of polymers: The gravitational component of the slurry's gravity on the inclined surface affects the flow and diffusion of polymers. As the inclination angle increases, the extreme point of the expansion pressure gradually shifts, and its value also increases accordingly. When the inclination angle increases to 0.5°, 1.0°, and 1.5°, the maximum expansion pressure increases by 3.8%, 10.6%, and 23.2%. The effect of inclination angles less than 1.5° on the diffusion range of polymers can be ignored. The diffusion radius calculation formula can refer to the diffusion in a free plate gap.

[0155] Effect of water on the flow and diffusion of a single-source polymer: While unpressurized water has little effect on expansion pressure, it does affect the flow and diffusion morphology of the polymer, causing wrinkles and micropores to appear at the edges of the solidified body, slightly increasing the radius by approximately 1 cm. The calculation of the diffusion radius can also be compared to diffusion in a free plate gap.

[0156] Effect of roughness on single-source flow and diffusion of polymers: There is a gap thickness threshold on the surface of any roughness. When the de-airing gap thickness exceeds the threshold, the expansion diffusion radius and expansion pressure distribution of the polymer are not affected by the roughness. The test results show that the threshold is positively correlated with the roughness. If the de-airing gap is smaller than the threshold, the maximum expansion pressure is no longer concentrated around the grouting hole, and the shape becomes an irregular nearly circular shape, but the average diffusion radius remains basically unchanged because the convexity of the rough surface has little effect on the polymer density. Effect of fixed boundary on single-source flow and diffusion of polymers: The maximum expansion pressure is positively correlated with the relative distance from the grouting hole to the fixed boundary. When When , the maximum expansion pressure remains basically unchanged, and the effect on the slurry flow and diffusion can be ignored; when When , the influence of the fixed boundary on the expansion pressure distribution is difficult to ignore, and the maximum expansion pressure increases with the decrease of the relative distance; when When , the maximum expansion pressure increases by about 30.86% and reaches the maximum value. At this time, the diffusion shape is approximately semicircular.

[0157] S4-4. Based on the influence law of single-source polymer flow diffusion and grouting method, the multi-source polymer diffusion law is analyzed, and the optimal preheating temperature and diffusion radius of multi-source polymer grouting are calculated.

[0158] The calculation formula for the optimal preheating temperature is:

[0159]

[0160] Where y represents the optimal preheating temperature, x represents the ambient temperature, and e represents a natural constant;

[0161] Multi-source grouting is divided into continuous grouting and jump grouting. The diffusion range of multi-source grouting is analyzed based on the research results of single-source grouting. In continuous grouting, the following assumptions are made for the theoretical analysis of the polymer diffusion range of the second grouting:

[0162] 1. The expansion and diffusion range of polymers is circular;

[0163] 2. Assume that point F of the diffusion circle coincides with point F of the theoretical diffusion circle;

[0164] According to the grouting spacing and grouting amount, we can know:

[0165] r1sinα=r2sinβr1cosα+r2cosβ=L

[0166] The two included angles are obtained. The overlap between the hypothetical diffusion circle B of the second grouting and the diffusion circle A of the first grouting is the increase in the actual diffusion circle C of the second grouting, and we can get:

[0167]

[0168] The distance moved to the left is R2-r2. In the uniform grouting and closed grouting methods of actual engineering, the grouting amount of each grouting hole is the same, that is, r1=r2, α=β, so the calculation formula of the diffusion radius of continuous grouting is:

[0169]

[0170] First, we still assume that the slurry spreads in a circular pattern. Second, given that the two grouting volumes are equal, theoretically, the polymer consolidation formed on both sides should have the same impact on the third grouting spread. Therefore, it is reasonable to assume that the circular pattern formed by the third grouting spread remains unchanged. Assuming the distance between the first and second grouting holes is 2L, we have:

[0171] r1 sinα=r2 sinβr1 cosα+r2 cosβ=L

[0172] The overlap between the hypothetical diffusion circle C of the third grouting and the diffusion circles A and B of the first and second grouting is the increase in the actual diffusion circle C of the third grouting, and we can get:

[0173]

[0174] When the third grouting volume is the same as the first two grouting volumes, the grouting calculation formula is jumped:

[0175]

[0176] Among them, R1 and R2 represent the diffusion radius of jump grouting and continuous grouting, α and β represent the inverse trigonometric sine function radians of the ratio of the radius of the actual diffusion circle obtained by the first grouting to the secant distance from the center of the actual diffusion circle of the first grouting to the overlapping part of the two ideal diffusion circles, and the inverse trigonometric sine function radians of the ratio of the radius of the ideal diffusion circle obtained by the second grouting to the secant distance from the center of the actual diffusion circle of the first grouting to the overlapping part of the two ideal diffusion circles, sin represents the sine function, r1 and r2 represent the radii of the actual diffusion circle obtained by the first grouting and the radii of the actual diffusion circle obtained by the second grouting, and L represents half the distance between the first grouting hole and the second grouting hole.

[0177] S5. Based on the multi-source diffusion law of polymers, the indoor model test results and law analysis of the gap-removing polymer reinforcement of the cement concrete pavement to be repaired are carried out to obtain the safe grouting range, that is, the maximum and minimum grouting volumes for the broken slab;

[0178] When treating road dewatering diseases, polymer grouting repair technology uses the expansion force it generates to quickly fill the dewatering gaps and tightly bond with the surface layer and roadbed to form a continuous whole. During the use and operation of the road, polymer materials replace part of the roadbed materials to bear traffic loads. Usually, the interface transition zone between different materials is often considered to be the weak point of the structure. By conducting bonding property tests on polymers and surrounding materials, the bonding properties of polymer materials with the surface layer and roadbed in the dewatering gaps are analyzed to verify whether the strength of the interface between the materials can withstand traffic loads. If polymers fill the dewatering gaps of cement pavement through free diffusion, they cannot effectively improve the bearing capacity of the pavement due to their low density. Therefore, appropriate grouting technology is needed to enhance the density and strength of the polymer in the dewatering gaps. By conducting reinforcement mechanism tests on polymers in dewatering gaps, a basic method for polymer grouting reinforcement of cement pavement dewatering diseases is established. Based on the finite element simulation model of polymer reinforcement of cement pavement, the maximum grouting volume and the minimum grouting volume for lifting are analyzed, so that step S5 includes the following steps:

[0179] S5-1. Obtain the bonding properties of polymer and cement concrete based on shear, splitting tension and bending tests;

[0180] Through shear and splitting tests, it can be found that the shear and splitting strength of the interface between polymer and cement concrete increases with the increase of interface roughness JRC and polymer density, showing an obvious positive correlation, such as Figure 13 As shown; In addition, Figure 14 As shown, increasing vertical pressure can enhance the shear strength of the interface, and the friction angle increases with increasing density and roughness, ranging from approximately 25° to 31°. The increase in roughness leads to an increase in the amplitude of the interface micro-serrations, prompting the interface to shift from sliding to shearing. The shear process of the specimen can be divided into the stress growth stage, stress yield stage, failure development stage, and complete failure stage, while the splitting process is divided into the linear elastic stage and the plastic yield stage. The shear failure and splitting failure characteristics of the interface are basically the same and can be divided into three types: a) failure along the boundary of the polymer material; b) failure along the boundary of the base material; and c) joint failure of the polymer and cement concrete materials along the interface. The test results show that after the polymer flows, fills, and solidifies in the gaps of the void disease, it can form good adhesion with the roadbed and pavement materials.

[0181] The bending test shows that the bending strength of the symmetrical grouting specimen is positively correlated with the density. The density exceeds 0.15g / cm 3 When the flexural strength is slightly higher than that of single source grouting, the density is lower than 0.15g / cm 3, the flexural strength weakens to a certain extent. For asymmetric grouting specimens, as the density difference gradually increases, the flexural strength of the specimen shifts from the flexural strength corresponding to the lower density to the higher density, but the strength of the low-density portion plays a decisive role. The stress-displacement curve of each specimen can be divided into two stages: the stress growth stage and the stress yield stage. The overall failure morphology of multi-source grouting specimens is similar to that of single-source grouting, showing brittle failure characteristics.

[0182] Combined with the experimental results of shear, splitting and bending tests, the influence of factors such as flexural strength, density, interface roughness and other factors on the bond between polymer and cement concrete, that is, the bonding characteristics, are determined.

[0183] S5-2. Based on the bonding characteristics and the multi-source diffusion law of polymers, the influence of polymer expansion pressure distribution is analyzed through a visual de-gap polymer reinforcement indoor model;

[0184] As a self-expanding repair material, polymers rely primarily on the expansion force released by the material itself to repair, reinforce, or elevate the damaged area. Therefore, it is necessary to study the expansion characteristics of polymers. The experimental environment temperature was set to 20°C, and the grouting preheating temperature was set to 40°C. The density range of the polymer was set to 0.15g / cm 3 to 0.50g / cm 3 By injecting a polymer into a closed mold, its rapid expansion within the mold cavity compresses a pressure sensor. A data acquisition device converts the pressure sensor's electrical signal into a digital signal and records it. To measure the expansion characteristics of polymers at different ambient temperatures, the test mold is placed in a constant temperature chamber until it reaches the preset temperature, after which grouting and pressure measurement are performed. The experimental results show that the expansion characteristics of polymers are such that the expansion pressure of polymer materials increases exponentially with increasing density. The expansion pressure of polymer materials briefly remains constant after injection, then rapidly increases, with smaller time increments resulting in larger pressure increments. When the reaction time reaches 20 to 30 seconds, the expansion pressure growth rate slows significantly and stabilizes, typically reaching its maximum value after 60 seconds. Because the inflection point is not obvious, 80% of the maximum expansion pressure is selected as a reference hypothetical inflection point. Analysis of the time points for materials of different densities shows that the time required to reach maximum pressure increases linearly with increasing density. For every 0.1 g / cm increase in density, the time required to reach maximum pressure increases linearly. 3 The inflection point will be delayed by about 3 to 5 seconds. After reaching the maximum expansion pressure, the pressure can remain stable for a long time, usually starting to drop significantly after 15 to 20 minutes.

[0185] Based on the expansion properties of polymers, the expansion reinforcement characteristics of polymer materials in desolvated voids were further analyzed. A visual desolvated void polymer reinforcement laboratory model was used to determine the expansion pressure distribution of polymers within confined desolvated voids. The experimental model was modified from a visual polymer diffusion laboratory model, differing in that baffles were added around the perimeter to ensure the cavity was closed. Experiments were conducted under both confined and unconfined conditions. The unconfined condition was divided into two cases: the first case included a 5 cm free outlet at the center of the four closed boundaries; the second case included a free outlet on the right boundary, while the other three sides remained closed. Within the confined space, the expansion pressure of the polymer material within the flat plate gap was lower than that within the cylindrical mold. The results showed that the expansion pressure of the polymer material within the flat plate gap decreased to approximately 70% to 80%. Calculated as the average expansion pressure, the average expansion pressure within the desolvated void was approximately 65%. The expansion pressure showed a horizontal distribution pattern of high in the center and low at the perimeter, increasing with increasing density. The maximum expansion pressure occurs at P40, and the minimum occurs at P0 or P80. The expansion pressure for a density of 0.15g / cm3 ranges from 31.4kPa to 81.7kPa, for a density of 0.25g / cm3, from 203.1kPa to 258.7kPa, and for a density of 0.35g / cm3, from 443.7kPa to 523.4kPa. When there are certain gaps at the boundary, the expansion force released by the polymer material during expansion causes the uncured slurry to be squeezed out of the gaps, further reducing the expansion pressure. When gaps are added to the boundary, the expansion pressure of the material is approximately 1 / 2 of that in a closed state. The material can maintain a higher expansion pressure in the middle, but the closer to the edge, the more obvious the downward trend in the expansion pressure of the polymer material, forming an overall parabolic shape. When one side is free, the material's own expansion pressure pushes the slurry out of the free boundary. As the gap further increases, the expansion pressure further decreases. The distribution of expansion pressure shows that the expansion pressure continues to decrease on the side close to the free boundary, while on the opposite side of the free boundary, the expansion pressure remains stable.

[0186] In addition, corresponding experiments were conducted to analyze the effects of void size, void shape, and inclination angle on the expansion pressure distribution. The magnitude of the expansion pressure distribution increases with increasing aspect ratio (void size). Within the range of 0 cm to 80 cm, polymer materials maintain a relatively high expansion pressure. The expansion pressure at an aspect ratio of 2.5 is generally greater than that at an aspect ratio of 1, increasing by approximately 15% to 20%. Beyond 80 cm, the expansion pressure shows a significant downward trend. Regardless of whether the void shape is an isosceles right triangle or a rectangle, the polymer effectively fills the entire void and develops a certain strength. The expansion pressure distribution exhibits lower pressure near the 0 cm position and higher pressure further away from the 0 cm position. The expansion pressure of polymer materials within approximately 1 / 5 to 1 / 4 of the horizontal area inside the void can be ignored in void reinforcement calculations for practical projects.

[0187] According to the above experimental results, the corresponding average expansion pressure of the de-spaced gap varies with density. The calculation formula is:

[0188]

[0189] Where ρ represents the polymer density and e represents the natural constant;

[0190] S5-3. Based on the influence of polymer expansion pressure distribution, the finite element simulation analysis method is used to determine the safe grouting range of the cement concrete pavement to be repaired.

[0191] Seal grouting followed by reinforcement grouting is an effective method for polymer grouting reinforcement of void defects. Seal grouting involves injecting a small amount of grouting around the pre-reinforced area of ​​the void defect to create a closed space; subsequent reinforcement grouting is performed within this closed space to ensure the desired strength and density. The paper also specifically describes the grouting areas and hole layout for void defects at slab edges and corners.

[0192] Through reasonable assumptions and mechanical analysis, the calculation formulas for the minimum grouting amount of the raised cement road slab under the conditions of slab corner and slab edge void defects were derived respectively. The corresponding formulas are:

[0193]

[0194] Where ρ1 and ρ2 represent the minimum grouting volume for lifting the cement pavement slab in the case of slab corner and edge voiding, respectively. In(·) represents a logarithmic function with base 10. K1, K2, and K3 represent the load transfer rates between slabs 1 and 2, 1 and 3, and 1 and 4, respectively. l represents the side length of the equivalent rectangle. l2 represents the distance between the side grouting hole and the slab joint. m represents the width of the effective expansion pressure application range. Slabs 1 to 4 are the cement concrete pavement slab, two side slabs, and opposite side slabs, respectively.

[0195] Finite element simulation was used to calculate the maximum broken board density under different working conditions, where the maximum broken board density range of the board edge is about 0.23g / cm 3 to 0.51g / cm 3 , and the range of plate corner voids is about 0.28g / cm 3 to 0.70g / cm 3 The results indicate that the maximum slab grouting density is positively correlated with slab thickness and the load transfer capacity of the slab joints, and negatively correlated with the size of the voids. The slab's planar dimensions have a relatively small impact on this density. Based on the simulation results, a calculation model for the maximum slab density was established, taking into account factors such as slab planar dimensions, void dimensions, slab thickness, and the load transfer coefficient of the slab joints.

[0196] A full-scale model test of polymer reinforcement and repair of void defects in cement pavement was designed and carried out. The polymer expansion pressure measured in the test was approximately 0.40 MPa, which is consistent with the results obtained from the indoor model test. The deflection and radar detection results before and after the void defect repair showed that the maximum deflection value after the polymer repair was reduced by more than 30%, and the radar wave spectrum changed from discontinuous to continuous, indicating that the polymer had a good filling effect in the void gap and the pavement bearing capacity was significantly enhanced. After the pavement panel was lifted, the diffusion of the polymer at the bottom of the panel was directly observed, and it was found that the polymer was tightly integrated with the roadbed and the pavement panel into a whole. The density of the reinforced grouting area is about 0.28g / cm 3 , and effectively achieved the preset goals.

[0197] S6. Based on the safe grouting range, the finite element simulation model of the dynamic response of the polymer repaired cement pavement is used to process and analyze the cement concrete pavement to obtain the optimal grouting amount;

[0198] Step S6 includes the following steps:

[0199] S6-1. Obtain heavy traffic loads and aircraft loads;

[0200] S6-2. Perform a triaxial compression test on the polymer to obtain the polymer mechanical parameters;

[0201] The polymer triaxial compression test uses a cylindrical specimen with a diameter of 5 cm and a height of 10 cm. Because polymer materials have fluidity and expansion during the mixing reaction and curing process, a 2 cm thick steel plate was used to independently develop a grouting mold. The grouting mold consists of a hollow steel pipe and two flanges, which are assembled into a whole by bolts and ensure a certain degree of sealing to prevent the polymer grouting material from flowing out. The density range of the specimen is controlled within 0.15g / cm 3 to 0.55g / cm 3 . The test instrument uses the British VJTech Pro temperature-controlled triaxial testing system of the Geotechnical Engineering Laboratory of the Hong Kong Polytechnic University. The test temperature is controlled at 20°C, the confining pressure is set to 0kPa, 100kPa, 200kPa, and 400kPa, and the loading rate is 1mm / min. The specific process of the test is: Test method: Install the cleaned specimen into the rubber sleeve and install it on the specimen holder in the pressure chamber. Set the confining pressure of the pressure chamber according to the test plan, and wait for water to be filled in the confining pressure chamber to the preset confining pressure and maintain stability. The triaxial compression test is started using the controlled displacement method. When the strain reaches 50% or the specimen is obviously damaged, the specimen is judged to have failed and the test is stopped; in order to prevent damage to the instrument when the specimen is damaged, when the density is greater than 0.25g / cm 3 The test is terminated when the strain reaches 30%.

[0202] The stress-strain curve of a triaxial compression test on a polymer can be divided into three stages: the elastic stage, the yield stage, and the densification stage. The elastic stage is characterized by a rapid increase in the stress-strain curve and can also be divided into the linear elastic stage and the non-linear elastic stage based on the shape of the stress-strain curve. In the linear elastic stage, the difference between the maximum and minimum principal stresses of the specimen increases linearly with increasing strain. A small strain increment can result in a large stress increment. The slope of the stress-strain curve in this stage represents the elastic modulus of the polymer under these environmental conditions. As strain continues to increase, the rate of increase in the stress-strain curve is not constant but gradually decreases, indicating this stage is the non-linear elastic stage. As clearly shown in the figure, the strain range in the elastic stage is generally between 5% and 10%. The range in the elastic stage gradually increases with increasing density and slightly increases with increasing confining pressure. The elastic modulus of polymer materials also exhibits a similar pattern. When the material density is 0.13 g / cm 3 When the confining pressure increases to 400 kPa, the elastic modulus of the material increases from 37.5 MPa to 62.7 MPa, an increase of 61.8%.

[0203] S6-3. Construct a finite element simulation model of the dynamic response of polymer-repaired cement pavement;

[0204] S6-4. Input the dimensions of the cement concrete pavement to be repaired, the void volume, the maximum grouting volume of the broken slab, heavy traffic load, aircraft load, and polymer mechanical parameters into a finite element simulation model of the dynamic response of the polymer-repaired cement pavement to simulate and determine the influence of the polymer on the fatigue performance of the cement pavement.

[0205] S6-5. Based on the influence of polymers on the fatigue performance of cement pavement, determine the optimal grouting amount for the cement concrete pavement to be repaired.

[0206] In actual engineering, we only need to pay attention to the maximum grouting volume, because a larger grouting volume will cause damage to the plate. First, through finite element simulation, the maximum broken plate grouting volume under this voiding condition is calculated. The standard for measuring it is the maximum bending tensile stress that exceeds the maximum bending strength of the road panel required by the specification. In order to facilitate the rapid determination of the maximum grouting volume in the project, this article calculates all the common working conditions and fits the equation of the maximum grouting volume for all working conditions based on the results. According to the maximum grouting volume, step S6 is entered. When the density exceeds 0.35, the cost-effectiveness of increasing the grouting volume is significantly reduced. In simple terms, when the maximum grouting volume is less than 0.35, the maximum grouting volume is the optimal grouting volume. When the maximum grouting volume is greater than 0.35, 0.35 is the optimal grouting volume.

[0207] S7. Repair the cement concrete pavement to be repaired according to the optimal grouting amount.

[0208] The repair adopts closed grouting and reinforcement grouting. For the plate corner void disease, single hole grouting is carried out at each plate corner, and the distance between the grouting hole and the plate joint is 0.25m to 0.40m, and it is dynamically adjusted according to the size of the plate; for the plate edge void disease, single hole grouting is carried out at the plate corners on both sides, and the distance between the grouting hole and the plate joint is 0.25m to 0.40m, and it is dynamically adjusted according to the size of the plate. Multi-hole grouting is carried out on the plate edge, with 4 to 5 grouting holes, and the grouting method adopts jump grouting or continuous grouting. The distance between the side grouting hole and the plate joint is 0.25m to 0.40m, the distance between the inner grouting hole and the adjacent grouting hole is 0.25m to 0.40m, and the distance l1 between the inner grouting hole and the adjacent grouting hole is according to the formula:

[0209]

[0210] Calculation is performed, where n represents the number of grouting holes on the edge of the plate, l2 represents the distance between the side grouting holes and the plate joints, and L represents the side length of the road panel.

[0211] Reinforcement grouting is to reinforce the pre-reinforced range that has formed a closed space. For the corner void disease, single-hole grouting is carried out at the corner of the plate. The grouting hole is selected at the center of the void area, or is set at 0.25m to 0.40m away from the plate joint (corresponding to the closed grouting hole), and is dynamically adjusted according to the size of the plate. For the edge void disease, multi-hole grouting is carried out on the edge of the plate. The number of grouting holes is 4 to 5, and the grouting method is jump grouting. The distance between the side grouting holes and the plate joints on both sides is 0.25m to 0.40m. The distance between the inner grouting hole and the adjacent grouting hole corresponds to the closed grouting. The distance between the grouting hole and the opposite side plate joint is half the width of the edge void.

[0212] In summary, the present invention is based on the basic principles and laws of flow and diffusion of polymer grouting materials and the influence of temperature changes on the viscosity and density parameters of polymers. A finite element simulation model and an indoor visualization test model of cement pavement void disease are designed. According to the influence of environmental factors on the single-source flow and diffusion of polymers, the multi-source diffusion law of polymers is determined, the optimal grouting amount is accurately determined, the service life of the pavement is increased, the pavement loss rate is reduced, and thus resource waste is reduced.

Claims

1. A method for repairing and reinforcing a cement concrete pavement, characterized in that: The following steps are involved: S1. Obtain the void range corresponding to the cement concrete pavement to be repaired; S2. Obtaining the load conditions and temperature stress of the cement concrete pavement to be repaired; S3. Use the void gap thickness calculation and analysis method to process the void range, load conditions and temperature stress to obtain the corresponding void volume; S4. Based on the void volume, the finite element simulation method is used to simulate the cement concrete pavement to be repaired and the multi-source diffusion law of polymer is obtained; S5. Based on the multi-source diffusion law of polymers, the indoor model test results and law analysis of the gap-removing polymer reinforcement of the cement concrete pavement to be repaired are carried out to obtain the safe grouting range; S6. Based on the safe grouting range, the finite element simulation model of the dynamic response of the polymer repaired cement pavement is used to process and analyze the cement concrete pavement to obtain the optimal grouting amount; S7. Repair the cement concrete pavement to be repaired according to the optimal grouting amount; The step S3 comprises the following steps: S3-1. Analyze the load conditions and temperature stresses to determine the influence of traffic load, range, vehicle speed, and pavement temperature stress on the vertical displacement of the slab. S3-2. Select the average value of the third peak of the distribution function of heavy vehicles as the calculation load; S3-3. Use the largest monthly average positive temperature gradient in a year to calculate the deformation caused by temperature stress in the plate; S3-4. Based on the calculated load, deformation, and first temperature boundary condition, a three-dimensional model of the cement concrete pavement to be repaired is constructed using a multi-layer finite element analysis model based on the Winkler foundation model theory; S3-5. Perform dynamic response analysis using a three-dimensional model of the cement concrete pavement to be repaired to obtain the node displacements at the slab edges and corners, i.e., the maximum thickness of the gap; S3-6. Construct a morphological curve equation for the void disease, and solve it based on the maximum thickness of the void gap and the void range to obtain the corresponding void volume.

2. The method for repairing and reinforcing a cement concrete pavement according to claim 1, characterized in that: The load conditions include the geometric parameters, elastic modulus, Poisson's ratio, thermal conductivity, density, specific heat capacity, convection heat transfer coefficient of each structural layer of the cement concrete pavement, as well as the location, size, and moving load parameters of the void disease; the temperature stress includes the temperature gradient.

3. The method for repairing and reinforcing a cement concrete pavement according to claim 1, characterized in that: The formula of the morphological curve equation of the gap removed in step S3-6 is: in, Indicates the node of the cement concrete pavement to be repaired. The morphological curve of the hollowing disease is shown. Indicates the maximum thickness of the gap in the cement concrete pavement to be repaired. Indicates the width of the void in the cement concrete pavement to be repaired. represents the cosine function, Represents pi.

4. The method for repairing and reinforcing a cement concrete pavement according to claim 1, characterized in that: The step S4 comprises the following steps: S4-1. Analyze the influence of temperature on polymer parameters, including polymer viscosity and density. S4-2. Determine the morphological characteristic parameters of the void disease on the cement concrete pavement to be repaired based on the void volume; S4-3. Based on the influencing patterns of polymer parameters and the morphological characteristics of void defects, a finite element simulation model and an indoor visualization test model were constructed to analyze the influence of influencing factors on the single-source flow and diffusion of polymers. The influencing patterns of the single-source flow and diffusion of polymers were obtained. The influencing factors included temperature, inclination angle, water, roughness, gap thickness, and fixed boundaries. S4-4. Based on the influence law of single-source polymer flow diffusion and grouting method, the multi-source polymer diffusion law is analyzed, and the optimal preheating temperature and diffusion radius of multi-source polymer grouting are calculated.

5. The method for repairing and reinforcing a cement concrete pavement according to claim 4, characterized in that: The calculation formula for the optimal preheating temperature is: in, Indicates the optimal preheating temperature, Indicates the ambient temperature, represents a natural constant; The diffusion radius includes the diffusion radius of jump grouting and continuous grouting, and the corresponding calculation formula is: in, 、 Indicates the diffusion radius of jump grouting and continuous grouting, The inverse trigonometric sine function radians representing the ratio of the radius of the actual diffusion circle obtained by the first grouting to the secant distance from the center of the actual diffusion circle of the first grouting to the overlapping part of the two ideal diffusion circles, The inverse trigonometric sine function radians representing the ratio of the radius of the ideal diffusion circle obtained by the second grouting to the secant distance from the center of the actual diffusion circle of the first grouting to the overlapping part of the two ideal diffusion circles, represents the sine function, Indicates the radius of the actual diffusion circle obtained by the first grouting.

6. The method for repairing and reinforcing a cement concrete pavement according to claim 4, characterized in that: The step S5 comprises the following steps: S5-1. Obtain the bonding properties of polymer and cement concrete based on shear, splitting tension and bending tests; S5-2. Based on the bonding characteristics and the multi-source diffusion law of polymers, the influence of polymer expansion pressure distribution is analyzed through a visual de-gap polymer reinforcement indoor model; S5-3. Based on the influence of polymer expansion pressure distribution, the finite element simulation analysis method is used to determine the safe grouting range of the cement concrete pavement to be repaired.

7. The method for repairing and reinforcing a cement concrete pavement according to claim 4, characterized in that: The step S6 comprises the following steps: S6-1. Obtain heavy traffic loads and aircraft loads; S6-2. Perform a triaxial compression test on the polymer to obtain the polymer mechanical parameters; S6-3. Construct a finite element simulation model of the dynamic response of polymer-repaired cement pavement; S6-4. Input the dimensions of the cement concrete pavement to be repaired, the void volume, the maximum grouting volume of the broken slab, heavy traffic load, aircraft load, and polymer mechanical parameters into a finite element simulation model of the dynamic response of the polymer-repaired cement pavement to simulate and determine the influence of the polymer on the fatigue performance of the cement pavement. S6-5. Based on the influence of polymers on the fatigue performance of cement pavement, determine the optimal grouting amount for the cement concrete pavement to be repaired.

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