Repairing and reinforcing method for cement concrete pavement

Abstract

The invention discloses a repairing and reinforcing method for a cement concrete pavement, and relates to the technical field of cement concrete pavement repairing. According to the method, a cement pavement void disease finite element simulation model and an indoor visual test model are designed on the basis of the basic principle and rule of flow diffusion of a high polymer grouting material and the influence rule of temperature change on viscosity and density parameters of a high polymer, and according to the influence of environmental factors on single-source flow diffusion of the high polymer, the void disease of the cement pavement is determined. The method determines the multisource diffusion law of the high polymer, accurately determines the optimal grouting amount, prolongs the service life of the pavement, reduces the loss rate of the pavement, and reduces the waste of resources.

Description

Technical Field

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

[0002] Cement concrete, a semi-rigid material, has high strength, large bearing capacity, and good water stability. In addition, inorganic binders have large reserves in my country, low prices, and rich application experience. Semi-rigid materials will still be the main base material. However, during the use of cement road panels, under the repeated action of traffic loads, the cement stabilized base under the board will produce a certain plastic deformation. At the same time, under the influence of temperature stress, the cement road panel will produce a certain warping, resulting in partial discontinuity or peeling at the interface between the road panel and the base. Under the combined action of traffic loads, rainfall, and structural free water, cement road panels will inevitably have problems such as scouring and mud pumping. With the deepening of repeated loads and water scouring and erosion, the bottom of the cement road panel will have different degrees of hollowing problems. If the hollowing disease is not handled in time, when the traffic load acts on the road panel, stress concentration will occur at the edge of the hollowing area, which will gradually cause broken panels, misalignment, joint fractures and other diseases. It will seriously affect the quality of traffic and bring great safety hazards. In addition, extreme natural disasters have occurred frequently in recent years. The road surface has been affected by floods, mudslides, etc., the roadbed has been severely damaged, and hidden diseases of cement pavements have occurred frequently. Frequent and long-term maintenance tasks have brought new difficulties to the passage of cement pavements. Therefore, a repair and reinforcement method for cement pavement hollowing diseases is needed to repair and reinforce cement pavements, prevent traffic accidents, and reduce the impact of natural disasters on the service life of the pavement. 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 a cement concrete pavement, which solves the problem of lack of a method for repairing and reinforcing a cement pavement hollowing disease.

[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. Obtaining 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 calculation and analysis method of the gap thickness of the void defect 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: the method 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, 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 It 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 road slab with void damage;

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

[0019] Figure 6 It is a curve of density changing with time;

[0020] Figure 7 It is a curve of viscosity changing with time;

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

[0022] Fig. 9 Set up schematics for boundary conditions;

[0023] Fig.10 This is a model diagram of the indoor visualization test;

[0024] Fig.11 Schematic diagram of the diffusion morphology of polymers in horizontal gaps;

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

[0026] Fig.13 This is the influence curve of roughness coefficient JRC and density on shear strength;

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

[0028] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept 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. Obtaining the void range corresponding to the cement concrete pavement to be repaired;

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

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

[0035] The cement concrete pavement was analyzed using the finite element fluid-solid coupling simulation model of void disease composed of the FLUNENT fluid analysis module and the TRANSIENT STRUCTURE transient structure analysis module, and the corresponding void disease influencing mechanism was obtained, that is, the inherent mechanism of the traffic load and water flow erosion affecting the development of void disease was analyzed. A full-scale test section of the pavement was carried out to analyze the influence of temperature on the void disease of the top, middle, bottom and base layers of the slab. There is a direct connection between deflection data and void damage. Based on the temperature influence and internal mechanism, the relationship between the temperature gradient, pavement panel modulus, base modulus, soil base modulus, pavement panel thickness, pavement panel size, void size, base thickness and other index data and deflection values ​​is analyzed. Based on the analysis results, the deflection value and the temperature gradient, pavement panel size, pavement panel modulus, base modulus, and foundation modulus with a correlation greater than 0.85 with the deflection data are selected as characteristic values, that is, the surface temperature data, pavement panel data, and deflection data are selected as the input of the subsequent BP neural network, and the void size (void range) is selected as the output of the BP neural network. Among them, selecting data with a higher correlation with the deflection value can capture deep-level features, which is conducive to improving the accuracy of identifying the void range.

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

[0037] The pavement clearance recognition model adopts the 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 through 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 a known deflection range, and the deflection basin changes of different pavement structures under the FWD load. The actual falling weight deflectometer with a load plate of 300mm diameter is used, such as Figure 2 As shown, for the plate corner, 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 edge, the deflection load is applied at the middle of the plate edge and the center of the loading plate is 25 cm away from the plate edge, and 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 law;

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

[0046] A5-2-1. Four layers of temperature sensors are installed on the top, between, bottom and base of the road surface and pavement. Each layer of sensors is installed at four corners and in the middle of the board. One temperature sensor is installed in the road surface to monitor the atmospheric temperature.

[0047] A5-2-2. Temperature data is collected through various temperature sensors, and the temperature data is classified according to the time of spring, summer, autumn and winter to obtain the classified temperature data; for example, for the road surface, the classified temperature data includes spring road surface temperature data, summer road surface temperature data, autumn road surface temperature data and winter road surface temperature data, and the top of the board, between the boards, the bottom of the board and the base are classified in the same way. Among them, March, April and May are set as spring, June, July and August are set as summer, September, October and November are set as autumn, and December, January and February are set as winter.

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

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

[0050]

[0051] Among them, T a,i represents the temperature of the ith species, represents the daily average temperature of the ith type, T m,i represents the daily temperature variation of the ith type, T max,i represents the maximum daily temperature of the ith type, T min,i represents the minimum daily temperature of the ith type, sin(·) represents the sine function, t i represents the phase of the ith type, t 0,i represents the initial phase of the ith 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 a non-steady-state temperature field based on the temperature distribution law, 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 micro-unit, 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 respectively represent the heat increment of the i-th micro-unit in the x, y, and z directions; wherein the micro-unit is a unit set at any position of 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 non-steady-state temperature field, and the temperature field distribution of the road surface at the beginning of heat transfer and the heat transfer state at its boundary, that is, the temperature field distribution law, are obtained. The first initial condition is the temperature distribution state in the road plate at time 0; the first boundary condition includes the first temperature boundary condition, the heat flux boundary condition and the surrounding environment 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 through 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, based on the stiffness matrix of each unit grid, determine whether the unit grid is empty; if so, modify the stiffness matrix of the unit grid; otherwise, retain the stiffness matrix of the unit grid; proceed to step A4-7;

[0066] A5-4-7. Calculate the overall 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 carried out 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 of 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 calculation and analysis method of the gap thickness of the void defect to process the void range, load conditions and temperature stress to obtain the corresponding void volume;

[0073] Generally, the hollowing disease of cement concrete pavement can be divided into two categories: absolute hollowing and relative hollowing. As the deformation increases, the bottom of the pavement slab begins to contact the top surface of the base layer and continues to deform together. When the load is removed, the pavement slab will rebound to its original position, and the top surface of the base layer in the hollowing area will also rebound to the original horizontal plane. The hollowing disease of cement concrete pavement slab is the result of the combined action of long-term load and hydraulic scouring, and the size of the hollowing is related to the traffic load and the physical parameters of the pavement structure layer. When vehicles with different loads and axles pass through the most unfavorable load position of the same hollowing disease, the deformation of the pavement slab caused by the lighter load is not enough to make the lower edge of the slab contact the upper edge of the base layer, but as the load increases, there will always be a threshold when the lower edge of the pavement slab contacts the upper edge of the base layer. Therefore, selecting a suitable traffic moving load is the key to calculating the gap problem of hollowing disease. During the action of traffic load, in addition to the flexural deformation of the hollowing disease area of ​​the pavement slab, there is also elastic deformation of the base layer in contact with the pavement slab. When the load and the physical parameters of the road slab remain unchanged, the relative maximum vertical deformation of the slab remains unchanged, and a larger elastic deformation of the base layer will lead to a larger gap formation. Therefore, the deformation effect of the base layer needs to be considered when calculating the gap problem of the gap. The maximum displacement value of the slab edge or slab corner calculated by selecting appropriate calculation parameters is the maximum gap thickness of the theoretical gap disease. Therefore, step S3 includes the following steps:

[0074] S3-1. Analyze the load conditions and temperature stresses to obtain the influence mechanism of traffic load, range, vehicle speed and pavement temperature stress on the vertical displacement of pavement panels;

[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 regarded 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 the 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 the 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 moving belt is set along the load moving direction. The width of the load moving belt is the same as the outer wheel track. The driving belt is divided into n cells with a width of a. Taking the traffic load occupying 3 cells as an example, the movement of the traffic load is represented by eliminating the load of cell No. 1 and increasing the load of cell No. 4. The driving speed is changed by changing the step time Δt. Among them, the formula for 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 the figure, in stage I, the maximum vertical displacement of the plate edge increases with the increase of vehicle speed, and the growth rate is fastest in the stage of 50km / h to 108km / h; when the vehicle speed reaches the critical value of 117.2km / h, the influence of vehicle speed on the maximum vertical displacement reaches the maximum value; when the vehicle speed exceeds the critical value, the maximum vertical displacement of the plate edge decreases with the increase of vehicle speed, showing a downward trend. Because the calculation model takes into account the inertia force, when the moving load approaches, the inertia force hinders its movement, and when the moving load moves away, the inertia force 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, affected by the linear expansion characteristics of the material, the elongation of the upper material of the pavement slab is lower than that of the bottom 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 corner or edge under the dynamic load calculated is based on the warping, and the vertical displacement increases compared to when there is no temperature gradient.

[0082] When the top temperature of the slab is greater than the bottom temperature, the elongation of the upper material of the pavement slab is greater than that of the bottom material, causing the center of the slab to arch upward and the stress on the edges and corners of the slab to increase. In addition, as the range of the hollowing defect at the edge or corner of the slab increases, the contact point between the base and the pavement slab moves inward, and the cantilever part of the pavement slab located above the hollowing defect will bend downward under the influence of temperature stress. During the temperature stress process, the corresponding program is written in FORTRAN language for calculation.

[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 largest 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 the 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 the three-dimensional model of the cement concrete pavement to be repaired to obtain the node displacements of the slab edges and slab corners, i.e., the maximum thickness of the gap;

[0087] S3-6. Construct a morphological curve equation of 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 to a cantilever beam with a concentrated load P at the top of the cantilever beam. According to the boundary constraints and loads, 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 deflection 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 deflection 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 deflection defect. Figure 4 As shown in the figure, the slopes of the three points are related as follows: 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 real 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 air gaps suddenly increases (affected by the scouring effect of water). Further increase in 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, c2 represent coefficients;

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

[0096]

[0097] Wherein, 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 gap 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 the pi;

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

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

[0100] V b =S·k

[0101]

[0102] Solved

[0103] The volume of the board corner hollowing disease is:

[0104]

[0105] Among them, V b represents the void volume of the plate edge, S represents the cross-sectional area of ​​the road panel, k represents the side length of the road panel, d represents the void thickness, l represents the void width, π represents pi, 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 side 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; polymer parameters include polymer viscosity and density;

[0110] The polymer was freely injected into the acrylic plate through the grouting system to observe its reaction curing process. The results show that the reaction curing process of the polymer is mainly divided into two stages: the free flow stage and the expansion and diffusion stage. In the free flow stage, the gel reaction is dominant, the liquid viscosity is low, it is easy to flow, and the liquid thickness is usually more than 3mm. In the expansion and diffusion stage, with the passage of time, the number of bubbles increases, resulting in obvious expansion of the slurry. It can be observed that the slurry has obvious expansion flow, the slurry radius increases rapidly, and the thickness also increases to a certain extent. This shows that the viscosity of the material is increasing, the lateral resistance in the horizontal direction is increasing, the material overcomes gravity and partially expands upward, and the temperature rises further. This shows that the viscosity of the material increases, the lateral resistance increases, the partial upward expansion overcomes gravity, and the temperature continues to rise. This stage is jointly promoted by the gel and foaming reactions. The exothermic reaction accelerates the foaming rate, resulting in a rapid increase in volume and a significant decrease in density. Therefore, it is necessary to analyze the multi-source diffusion law of polymers according to the free flow stage and the expansion and diffusion stage.

[0111] The density change process of polymer is dynamic, and the density model can be regarded as three liquids (water, polyurethane raw material mixture, physical foaming agent) and two gases (foaming agent gasified at high temperature and carbon dioxide generated by the reaction). The density change of polymer reaction expansion process at different temperatures was measured, and the material preheating temperature variable was set to 30℃, 40℃ and 50℃, and the ambient temperature was 25℃; the specific steps of the measurement are:

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

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

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

[0115]

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

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

[0118] During the reaction expansion process, the polymer is initially a transparent brown liquid. As time goes by, dense bubbles gradually form, the volume expands rapidly, and turns light yellow-white within 1 minute. The end of the reaction is marked by the end of the volume no longer increasing. As the preheating temperature increases, the rate of decrease of the polymer density accelerates. When the temperature exceeds 40°C, the density of the solid body no longer decreases; and under 30°C preheating, the density of the solid body increases slightly to 112kg / m 3 This indicates that the reduction in preheating temperature significantly affects the foaming reaction, resulting in a reduction in volume expansion rate. Figure 6 As shown in the figure, the fitting curve of the density change of polymers at different temperatures during the reaction and curing process is as follows:

[0119]

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

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

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

[0123] ② Pour 50 ml of each polymer raw material into a 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 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, the viscosity rises sharply, and the later rapid growth stage usually occurs in the last ten seconds of the reaction. The fitting curve formula for the viscosity change of polymers at different temperatures during the reaction curing process over 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 a finite element analysis model. The expansion and diffusion process of the polymer is regarded as the flow of a fluid. The motion state of a fluid can be divided into: turbulent flow, transitional flow and laminar flow. The flow state is usually determined by calculating the Reynolds number of the fluid. In the present invention, the Reynolds number of the polymer during the expansion and diffusion process is 1727.5, so the finite element analysis model is constructed according to the laminar flow state.

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

[0131] S4-3. Based on the influencing rules of polymer parameters and the morphological characteristic parameters of voiding diseases, a finite element simulation calculation model and an indoor visualization test model are constructed and analyzed to analyze the influencing factors, and the influencing rules of polymer single-source flow diffusion are obtained; among them, the influencing factors include temperature, inclination, water, roughness, gap thickness and fixed boundary;

[0132] There are many factors that affect the flow of slurry in the degassing gap, among which the main influencing factors are: gap opening (thickness), tilt angle, boundary conditions, roughness, water environment, etc. The finite element calculation model uses FLUENT software to construct a degassing gap for actual simulation calculation. The visual indoor test model is made by building a model made of acrylic board, and the flow of polymer is analyzed by real grouting method.

[0133] Since the expansion and diffusion process of polymer grouting is a complex physical and chemical process involving polymerization reaction, diffusion process and temperature change, the following key factors need to be considered when establishing a finite element simulation model: reaction principle and system; density, viscosity and temperature; diffusion mode: clarify the diffusion mode of the polyurethane filling process - free or restricted. Set appropriate boundary conditions; control conditions: set model control conditions such as grouting speed, temperature and reactant concentration. Selecting appropriate control conditions can enhance the accuracy and stability of the model.

[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 subroutines and model parameter settings.

[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, moderate, and severe voiding damages, 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 figure. Fig. 9 shown.

[0137] In the UDF subroutine, according to the results of polymer material parameter test, the density and viscosity parameters of the polymer are set by writing UDF subroutines based on C language. FLUENT's built-in compiler is used to read and apply these UDF subroutines to achieve accurate assignment of material parameters in the model.

[0138] In the model parameter setting, the gridded geometric model is imported into the FLUENT software for parameter configuration, and the "double precision" calculation mode is adopted. The VOF multiphase flow model is selected to simulate the injection process of polymer materials into the air, and air is defined as the main phase (in the simulation with ambient water, water is the main phase), the polymer is the secondary phase, and the fluid parameters of the polymer are set through the UDF subroutine. At the same time, considering the influence of gravity, the vertical gravity acceleration is applied. Based on the research results in the previous section, the viscosity model is determined to be a laminar model. The PISO strategy is adopted for the solution, and the second-order discretization method is applied.

[0139] For indoor visualization test models, such as Fig.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 pipe: Use cold-drawn square steel pipe with specification Q345B, cross section of 350mm×500mm and thickness of 2mm. The upper and lower layers of steel pipe are fixed by bolts to fix the acrylic plate to prevent vertical displacement. After testing, when the polymer flows freely, the maximum deflection of the rectangular steel pipe is ≤1mm, which can be regarded as a fixed boundary.

[0141] Acrylic plate: A fully transparent acrylic thick plate with a size of 1200mm×2400mm×25mm was selected. Its perspective makes it easy to observe the entire diffusion process of the polymer. The acrylic plate is divided into an upper top plate and a lower bottom plate. Multiple grouting holes are evenly set along the long axis of the upper top plate, and each hole is 10cm apart. By adjusting the position of the grouting head installed on these holes, a multi-source grouting diffusion experiment can be carried out.

[0142] Pad: 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 at the corresponding position and fix it with bolts;

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

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

[0149] ⑦ When the polymer stops diffusing, stop recording the pressure data. After waiting for 10 minutes, dismantle the model test device and clean the polymer solid 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 injecting 0.50kg, 0.75kg and 1.00kg polymer slurry are compared and analyzed. Fig.11 and Fig.12 As shown in the figure, the diffusion of polymer in the horizontal degassing gap is in the shape of a round cake, and the diffusion radius expands with the increase of grouting amount. For the three working conditions of grouting amount of 0.50kg, 0.75kg and 1.00kg, the diffusion radius model test results are 0.45m, 0.58m and 0.63m respectively, and the simulation results are 0.465m, 0.569m and 0.658m respectively, with an average error of less than 5.0%.

[0152] Effect of temperature on single-source flow and diffusion of polymer: The density of polymer solidification body will decrease with the increase of preheating and ambient temperature, and the law is more obvious within 40℃. The viscosity and density change curves of polymer can be divided into a stable stage and a rapid change stage. In the stable stage, the viscosity keeps increasing slowly, while the density is the opposite. This stage accounts for more than 80% of the total reaction time. The increase of preheating temperature will cause the initial viscosity to decrease, and the duration of the stable stage will also be shortened. When the reaction time reaches a certain threshold, the viscosity and density of the polymer will increase and decrease exponentially respectively. This rapid change stage usually occurs in the last ten seconds. When the temperature is too low, the reaction speed of the gel reaction and the foaming reaction is too different, then the flow and diffusion of the polymer depends on gravity and grouting pressure, the overall foaming of the solidification body is poor, and the radius is small. The color is close to the dark brown of the raw material, but the overall material strength is high. When the temperature is too high, the reaction speed of the foaming reaction is much greater than that of the gel reaction, and the slurry quickly enters the expansion and diffusion stage after injection. In the later stage of the reaction, the edge material solidifies prematurely, and the foaming reaction is too fast, which causes stress concentration at the edge of the solidified body and causes cracking of the solidified body.

[0153] Effect of gap thickness on single-source flow diffusion of polymer: The expansion pressure of polymer in the gap of free plates is distributed as a parabola of quadratic function along any axis, and its maximum expansion pressure is inversely proportional to the square of thickness and directly proportional to the grouting amount. The flow diffusion shape is circular, and the average diffusion radius is inversely proportional to the gap thickness and directly proportional to the grouting amount.

[0154] The influence of inclination angle on the single-source flow and diffusion of polymers: The gravity component of the slurry gravity on the inclined surface will affect 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. 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 influence of the inclination angle less than 1.5° on the diffusion range of polymers can be ignored, and the formula for calculating the diffusion radius can refer to the diffusion of the free plate gap;

[0155] Effect of water on single-source flow and diffusion of polymers: Unpressurized water has little effect on the expansion pressure, but it will affect the flow and diffusion morphology of polymers. Wrinkles and tiny bubbles will appear on the edge of the solid body, which will slightly increase the radius by about 1 cm. The calculation of its diffusion radius can also refer to the diffusion in the gap of a free plate.

[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 protrusions of the rough surface have little effect on the polymer density. Effect of fixed boundaries 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 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 a semicircle.

[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] Among them, y represents the optimal preheating temperature, x represents the ambient temperature, and e represents the 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 proposed for the theoretical analysis of the polymer diffusion range for calculating 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:

[0165] r1sinα=r2sinβr1cosα+r2cosβ=L

[0166] The part where the assumed diffusion circle B of the second grouting overlaps with 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, and 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, it is still assumed that the diffusion of the slurry is circular. Secondly, given that the two grouting volumes are equal, theoretically the polymer consolidation formed on both sides should have the same effect on the third grouting diffusion. Therefore, it is reasonable to assume that the circle formed by the third diffusion remains unchanged. Assuming that the distance between the first grouting hole and the second grouting hole is 2L, then:

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

[0172] The overlapped part of the assumed diffusion circle C of the third grouting with the diffusion circles A and B of the first and second grouting is the increased part of 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] Wherein, R1 and R2 represent the diffusion radius of jump grouting and the diffusion radius of 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 spacing 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 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 amounts of the broken slabs;

[0178] When dealing with road degassing diseases, polymer grouting repair technology uses the expansion force it generates to quickly fill the degassing 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 degassing gaps are analyzed to verify whether the strength of the interface between the materials can withstand traffic loads. If polymers fill the degassing gaps of cement pavement through free diffusion, due to their low density, they cannot effectively improve the bearing capacity of the pavement, so appropriate grouting technology is needed to enhance the density and strength of the polymers in the degassing gaps. By conducting reinforcement mechanism tests on polymers in degassing gaps, a basic method for polymer grouting reinforcement of cement pavement degassing diseases is established. Based on the finite element simulation model of polymer reinforcement of cement pavement, the maximum grouting amount and the minimum grouting amount for lifting of polymer reinforcement 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 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 Fig.13 As shown; In addition, Fig.14 As shown in the figure, increasing the vertical pressure can enhance the shear strength of the interface, and the friction angle increases with the increase of density and roughness, which is about 25° to 31°. The increase in roughness leads to an increase in the amplitude of the interface micro-serrations, which prompts the interface to turn from sliding to shearing. The shear process of the specimen can be divided into the stress growth stage, stress yield stage, damage development stage, and complete damage 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; 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 gap of the void disease, it can form a good bond 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 Its flexural strength is slightly higher than that of single-source grouting; its density is lower than 0.15g / cm 3, the flexural strength is weakened to a certain extent. For asymmetric grouting specimens, as the density difference gradually increases, the flexural strength of the specimen will tilt from the flexural strength corresponding to the lower density to the higher density, but the strength of the low-density part plays a decisive role. The stress-displacement curves of the specimens can be divided into two stages: the stress growth stage and the stress yield stage. The overall failure morphology of the multi-source grouting specimens is similar to that of the 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 the visualization of the indoor model of degassed polymer reinforcement;

[0184] As a self-expanding repair material, polymer mainly relies on the expansion force released by the material itself to complete the repair, reinforcement or lifting of the damaged location, so it is necessary to study the expansion characteristics of polymer. The experimental environment temperature is set to 20℃, and the grouting preheating temperature is set to 40℃. The research density range of polymer is set to 0.15g / cm 3 Up to 0.50g / cm 3 . By injecting polymer into the closed mold, the polymer is rapidly expanded in the mold cavity and squeezes the pressure sensor. The electrical signal of the pressure sensor is converted into a digital signal and recorded by the data acquisition instrument. In order to measure the expansion characteristics of polymers at different ambient temperatures, the test mold needs to be placed in a constant temperature box until the preset temperature is reached, and then the grouting operation and pressure measurement are carried out. According to the experimental results, the expansion characteristics of polymers are: the expansion pressure of polymer materials increases exponentially with the increase of density. The expansion pressure of polymer materials stays for a short time after injection, and then rises rapidly. Small time increments will cause large pressure increments. When the reaction time reaches 20s to 30s, the growth rate of expansion pressure slows down significantly and tends to be stable. Its maximum value usually appears after 60 seconds. Since the inflection point is not obvious, 80% of the maximum expansion pressure is selected as the reference assumed inflection point. Analysis of the time nodes of materials with different densities shows that the time required to reach the maximum pressure increases linearly with the increase of density. For every 0.1g / cm increase in density 3 , the time of inflection point will be delayed by about 3s to 5s. After reaching the maximum expansion pressure, the pressure can remain stable for a long time, usually starting to drop significantly after 15min to 20min.

[0185] Based on the expansion characteristics of polymers, the expansion reinforcement characteristics of polymer materials in de-aired gaps are further analyzed. The expansion pressure distribution law of polymers in de-aired gaps in limited space is determined by using the indoor model test of visualized de-aired gap polymer reinforcement. The experimental model is modified based on the indoor model of visualized polymer diffusion. The difference is that baffles are added around to ensure the closure of the cavity. Experiments are carried out under closed conditions and non-closed conditions. The non-closed conditions are divided into two cases. The first case is to set a 5cm free outlet in the central position of the closed boundary around the four sides. The second case is to set the right boundary as a free outlet and keep the other three sides closed. In the closed space, the expansion pressure of polymer materials in the gap between the flat plates is lower than that in the cylindrical mold. The results show that the expansion pressure of polymer materials in the gap between the flat plates drops to about 70% to 80%; if calculated by the average expansion pressure, the average expansion pressure of the de-aired gap is about 65%. The expansion pressure has a distribution characteristic of high in the middle and low around the four sides on the horizontal plane, and increases with the increase of density. The maximum expansion pressure appears at P40, and the minimum appears at P0 or P80. The expansion pressure of a density of 0.15g / cm3 is in the range of 31.4kPa to 81.7kPa, the expansion pressure of a density of 0.25g / cm3 is in the range of 203.1kPa to 258.7kPa, and the expansion pressure of a density of 0.35g / cm3 is in the range of 443.7kPa to 523.4kPa. When there is a certain gap at the boundary, the expansion force released by the polymer material during the expansion process will cause the uncured slurry to be squeezed out of the gap, thereby further reducing the expansion pressure. In the case of adding gaps to the boundary, the expansion pressure of the material is about 1 / 2 of that in the closed case. The material can maintain a higher expansion pressure in the middle part, and the closer to the edge part, the more obvious the trend of the polymer material's expansion pressure decreases, and it is parabolic as a whole. When one side is free, the material's own expansion pressure will push the slurry out from the free boundary. As the gap further increases, the expansion pressure further decreases. From the distribution of expansion pressure, the expansion pressure continues to decrease on the side close to the free boundary; on the opposite side of the free boundary, the expansion pressure remains stable.

[0186] In addition, corresponding experiments are set up to analyze the influence of void size, void shape, and inclination angle on the expansion pressure distribution. The change range of the expansion pressure distribution increases with the increase of the aspect ratio (void size). In the position of 0cm to 80cm, the polymer material can maintain a relatively high expansion pressure. The expansion pressure under the condition of aspect ratio of 2.5 is generally greater than the expansion pressure under the condition of aspect ratio of 1, which increases by about 15% to 20%. When the position is greater than 80cm, the expansion pressure shows a significant downward trend; regardless of whether the void shape is an isosceles right triangle or a rectangle, the polymer can fill the entire void gap well and form a certain strength; the distribution of the expansion pressure is shown as lower expansion pressure near the position 0cm and higher expansion pressure away from the position 0cm. The expansion pressure of the polymer material within the horizontal area of ​​about 1 / 5 to 1 / 4 of the inner side of the void can be ignored in the calculation process of void reinforcement in actual engineering.

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

[0188]

[0189] Where, ρ represents polymer density, and e represents a 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] Sealing grouting followed by reinforcement grouting is an effective means of polymer grouting reinforcement for void defects. Sealing grouting is to perform a small amount of grouting around the pre-reinforcement range of the void defect to form a closed space; the subsequent reinforcement grouting is performed in this closed space to ensure that the established strength and density are achieved. The grouting area and hole layout plan for void defects at the edge and corner of the plate are specifically explained.

[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 damage were derived respectively. The corresponding formulas are:

[0193]

[0194] Among them, ρ1 and ρ2 represent the minimum grouting amount of the cement road slab under the condition of plate corner and plate edge voiding, In(·) represents the logarithmic function with base 10, K1, K2, K3 represent the plate joint load transfer rate between plate No. 1 and plate No. 2, plate No. 1 and plate No. 3, plate No. 1 and plate No. 4, l represents the side length of the equivalent rectangle, l2 represents the distance between the side grouting hole and the plate joint, and m represents the width of the application range of the effective expansion pressure. Among them, plate No. 1 to plate No. 4 are cement concrete road slabs, two side plates, and opposite side plates, 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 for the board edge being empty was about 0.23g / cm 3 Up to 0.51g / cm 3 , and the range of the plate corner void is about 0.28g / cm 3 Up to 0.70g / cm 3 The results show that the maximum grouting density of the broken plate is positively correlated with the plate thickness and the load transfer capacity of the plate joint, and negatively correlated with the void size, while the plane size of the road plate has a relatively small effect on it. According to the simulation results, a calculation model for the maximum broken plate density considering factors such as the plane size of the road plate, void size, plate thickness and plate joint load transfer coefficient was established.

[0196] A full-scale model test of polymer reinforcement and repair of cement pavement voids was designed and carried out. The measured expansion pressure of the polymer in the test was about 0.40MPa, which was consistent with the results of the indoor model test. The deflection and radar detection results before and after the void 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 voids 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, performing 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. Since polymer materials have fluidity and expansion during the mixing reaction and curing process, a 2 cm thick steel plate is used to independently develop a grouting mold. The grouting mold consists of a hollow steel pipe and two flanges. The various parts are combined into a whole by bolts, and a certain degree of sealing is guaranteed to prevent the polymer grouting material from flowing out. The density range of the specimen is controlled at 0.15g / cm 3 Up to 0.55g / cm 3 . The test instrument uses the British VJTech Pro temperature-controlled triaxial test 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 rack in the pressure chamber. Set the confining pressure of the pressure chamber according to the test plan, and wait for the confining pressure chamber to be filled with water to the preset confining pressure and remain stable. 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 termination condition is when the strain reaches 30%.

[0202] The stress-strain curve of the triaxial compression test of polymer materials can be divided into three stages: elastic stage, yield stage and densification stage. The elastic stage is characterized by the rapid growth of the stress-strain curve, which can also be divided into the linear elastic stage and the non-linear elastic stage according to the curve form of the stress-strain. In the linear elastic stage, the difference between the maximum principal stress and the minimum principal stress of the specimen increases linearly with the increase of strain. A small strain increment can cause a large stress increment. The slope of the stress-strain curve in this stage is the elastic modulus of the polymer under the environmental conditions. With the continuous increase of strain, the growth rate of the stress-strain curve is not constant, and a gradual decrease occurs. This stage is the non-linear elastic stage. It can be clearly seen from the figure that the strain range of the elastic stage is usually in the range of 5% to 10%. The elastic stage range gradually increases with the increase of density and slightly increases with the increase of confining pressure. The elastic modulus of polymer materials also shows the same law. When the material density is 0.13g / 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 size of the cement concrete pavement slab to be repaired, the void volume, the maximum grouting volume of the broken slab, the heavy traffic load, the aircraft load and the polymer mechanical parameters into the finite element simulation model of the dynamic response of the polymer-repaired cement pavement to simulate and obtain the influence of the polymer on the fatigue performance of the cement pavement;

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

[0206] In actual engineering, we only need to pay attention to the maximum grouting amount, because a larger grouting amount will cause damage to the board. First, through finite element simulation, the maximum grouting amount of the broken board under this de-airing condition is calculated. The standard for measuring it is the maximum bending strength of the road panel whose maximum bending tensile stress exceeds the requirements of the specification. In order to facilitate the rapid determination of the maximum grouting amount in the project, all common working conditions are calculated in this article, and the equation of the maximum grouting amount of all working conditions is fitted according to the results. According to the maximum grouting amount, step S6 is entered. When the density exceeds 0.35, the cost-effectiveness of increasing the grouting amount is significantly reduced. In short, when the maximum grouting amount is less than 0.35, the maximum grouting amount is the optimal grouting amount. When the maximum grouting amount is greater than 0.35, 0.35 is the optimal grouting amount.

[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 hollowing disease of the plate corner, 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 hollowing disease of the plate edge, 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, the number of grouting holes is 4 to 5, 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-reinforcement range of the closed space. For the hollowing disease of the plate corner, single-hole grouting is carried out at the plate corner. The grouting hole is selected as the center of the hollowing area, or set at 0.25m to 0.40m away from the plate joint (corresponding to the closed grouting hole), and dynamically adjusted according to the size of the plate. For the hollowing disease of the plate edge, multi-hole grouting is carried out on the plate edge. The number of grouting holes is 4 to 5, and the grouting method is jump grouting. The spacing between the side grouting holes and the plate joints on both sides is 0.25m to 0.40m. The spacing between the inner grouting hole and the adjacent grouting hole corresponds to the closed grouting, and the spacing between the grouting hole and the opposite side plate joint is half of the hollowing width of the plate edge.

[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, designs a finite element simulation model of cement pavement debonding 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.

Claims

1. A method for repairing and reinforcing a cement concrete pavement, characterized in that: The following steps are involved: S1. Obtaining 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 calculation and analysis method of the gap thickness of the void defect 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.

2. The method for repairing and reinforcing 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 mud concrete pavement, and 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 cement concrete pavement according to claim 1, characterized in that: The step S3 comprises the following steps: S3-1. Analyze the load conditions and temperature stress to obtain the influence mechanism of traffic load, range, vehicle speed and pavement temperature stress on the vertical displacement of the plate; 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 the 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 the three-dimensional model of the cement concrete pavement to be repaired to obtain the node displacements of the slab edges and slab corners, i.e., the maximum thickness of the gap; S3-6. Construct a morphological curve equation of 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.

4. The method for repairing and reinforcing cement concrete pavement according to claim 3 is characterized in that: The formula of the morphological curve equation of the free gap in step S3-6 is: Among them, 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.

5. The method for repairing and reinforcing 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; polymer parameters include polymer viscosity and density; S4-2. Determine the morphological characteristic parameters of the void disease of the cement concrete pavement to be repaired based on the void volume; S4-3. Based on the influencing rules of polymer parameters and the morphological characteristic parameters of voiding diseases, a finite element simulation calculation model and an indoor visualization test model are constructed to analyze the influence of influencing factors on the single-source flow diffusion of polymers, and the influencing rules of the single-source flow diffusion of polymers are obtained; among them, the influencing factors include temperature, inclination, water, roughness, gap thickness and fixed boundary; 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.

6. The method for repairing and reinforcing cement concrete pavement according to claim 5, characterized in that: The calculation formula of the optimal preheating temperature is: Among them, y represents the optimal preheating temperature, x1 represents the ambient temperature, and e represents the natural constant; The diffusion radius includes the diffusion radius of jump grouting and continuous grouting, and the corresponding calculation formula is: Wherein, R1 and R2 represent the diffusion radius of jump grouting and the diffusion radius of continuous grouting, α represents the inverse trigonometric sine function radian 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, β represents the inverse trigonometric sine function radian 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, and r1 represents the radius of the actual diffusion circle obtained by the first grouting.

7. The method for repairing and reinforcing cement concrete pavement according to claim 5, 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 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 the visualization of the indoor model of degassed polymer reinforcement; 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.

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

Images