# Research on Mechanical Response of Polymer Grouting Repair for Longitudinal Cracks in Reconstructed and Expanded Expressway Pavement

Authors: Songtao Li; Yongding Niu; Baolin Wang; Yanlong Gao; Yongchao Zhu
Journal: Mathematical Problems in Engineering
 (2022)

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## Abstract

Polymer grouting materials have been widely used in road repair projects. In order to study the application of polymer grouting materials in repairing the joint cracks and voids of new and old subgrades in the reconstruction and expansion projects of expressways. According to the phenomenon investigation data, ABAQUS finite element software was used to establish a three-dimensional road mechanical response analysis model, and the mechanical response characteristics of the road before and after polymer grouting were systematically analyzed. The research results of the road which was repaired by polymer grouting show that the shear force between the polymer grouting material and the materials on both sides of the old and new subgrades can repair the cracks at the joint and the diseases in the void area of the new subgrade, so as to reduce the displacement and settlement of the road surface. The maximum dynamic stress peak value of the old and new subgrade road surfaces is located at the load action position, and with the increase of the distance from the load action position, the dynamic stress peak value gradually decreases, showing an M-shaped distribution as a whole. The original stress transfer law of the road structure was changed, so that the dynamic stress of the new subgrade is significantly smaller than that of the old subgrade. The critical surface formed between polymer grouting material and subgrade material has a certain shear strength, which reduces the tensile stress and strain between structural layers. It will improve the bearing capacity of the subgrade and at the same time provide a practical reference for the treatment of longitudinal cracks in the reconstruction and expansion of expressway.


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## Body

## 1. Introduction

In the early stage of China’s expressway development, the previously built expressways could no longer meet the needs of the current increasing traffic volume due to low design standards. Therefore, my country has carried out a lot of reconstruction and expansion of the old expressways to meet the needs of the development of the transportation industry. However, in the operation stage of the reconstruction and expansion of the expressway, with the cyclic action of the vehicle load, the junction of the old and new road surfaces has different degrees of voiding disease, which leads to the cracking of the road surface, which seriously affects the structural safety of the expressway and threatening people’s safe travel.At present, relevant scholars at home and abroad have carried out relevant research on the structure of the reconstruction and expansion of the expressway. Taking the reconstruction and expansion project of Guiliu Expressway as an example, Liang et al. [1] determined the optimal reconstruction and expansion scheme by comparing and analyzing the pros and cons of the three schemes, which minimized the impact on traffic volume. Chen [2] analyzed the application of bubble mixed light soil in expressway reconstruction and expansion through case study and believed that using bubble mixed light soil as backfill material can avoid large-scale excavation of the original roadbed, thereby reducing disturbance. To ensure construction quality, Yao et al. [3] focused on analyzing the stability of the old and new subgrade splicing structures by measuring the moisture content of the subgrade slope on the spot and put forward an effective method to deal with the old subgrade water seepage. Jia et al. [4] analyzed the influence of concrete guardrail foundation form on expressway reconstruction and expansion projects through numerical simulation. Wang et al. [5] took the reconstruction and expansion of the highway slope as the research object and used the method of numerical simulation to analyze the stability of the slope. By comparing and analyzing the two support schemes, the optimal method of slope support was determined. Zhang et al. [6, 7] proposed an evaluation system suitable for the reconstruction and expansion of highways, so as to meet the needs of comprehensive evaluation of the service performance of the reconstruction and expansion expressways.In addition, grouting technology has also been widely used in engineering practice. Fattah et al. [8, 9] grouted gypsum soil with acrylate, which reduced the compressibility of gypsum soil by more than 60–70%. Fattah et al. [10] stabilized the dunes and reduced erosion by about 70% by grouting the soil with a lime-silica fume material slurry. In this paper, polymer grouting technology was used in expressway reconstruction and expansion maintenance.It can be seen from the above research that the expressway reconstruction and expansion project inevitably faces the problem of splicing new and old subgrades. Under the long-term vehicle load cycle, due to the nonuniformity of the old and new subgrade structures, the bearing capacity of the two subgrades is different, the wheel load shows stress redistribution at the splicing of the new and old subgrades, and the new subgrade settles significantly. Eventually, the reconstruction and expansion of the expressway produced cracks at the junction of the old and new subgrades. The structural stability of reconstructed and expanded expressways has become a key research issue in the current transportation industry. This paper will take the reconstruction and expansion of the expressway as the research object, use the numerical simulation software to establish the corresponding three-dimensional numerical model of the reconstructed and expanded expressway, and analyze the mechanical response performance of the reconstructed and expanded expressway before and after polymer grouting repair. In addition, through the application of long-term vehicle load, the bearing capacity of the subgrade after polymer grouting repair was analyzed, which provides a practical reference for the treatment of longitudinal joints at the junction of new and old roadbeds in the reconstruction and expansion of expressways.


## 2. Principle of Polymer Grouting Repair

### 2.1. Polymer Grouting Material

The polymer grouting material used in this paper was mainly composed of polyether polyol, polyisocyanate, foaming agent, catalyst, foam stabilizer, and various other auxiliary agents. The chemical polymerization reactions that take place mainly include foaming reactions and gelling reactions [11–13]. The foaming reaction refers to the chemical reaction between polyisocyanate groups and hydroxyl groups, mainly generating carbon dioxide and urea, and generating a large amount of heat. This reaction is a key factor in the formation of polymer foams and directly affects the mechanical strength of the formed polymer foams. The reaction equation is shown in formula (1) [14, 15]. The gel reaction mostly refers to the chemical reaction between the –NCO group of the isocyanate and the –OH group of the polyol to generate a carbamate group and generate a certain amount of heat. The reaction equation is shown in formula (2) [16, 17].(1)2R−NCO+H2O⟶R−NH−CO−NH−R+CO2+thermal energy,(2)R−NCO+R′−OH⟶R−NH−CO−O−R′+thermal energy,


### 2.2. Principle of Polymer Grouting Filling

When repairing the longitudinal joints of the old and new subgrades of the renovated and expanded expressway, the polymer grouting material was injected into the void area by the high-pressure grouting gun through the grouting hole [18–22]. In the void area, the polymer grouting material undergoes a rapid curing reaction and diffuses in the crack to form a foam with a certain strength. Since the degree of curing reaction was relatively severe, the foam body has a large expansion force during the formation process, and the generated foam body does not react with water. The repair principle is shown in Figure 1.Figure 1
Principle of polymer grouting repair.When the hollow area of the roadbed is filled with the polymer grouting material, the liquid water will also be squeezed out through the unused grouting pipe next to it, and the weak and loose soil under the polymer grouting material will also be squeezed and compacted, so as to finally achieve the purpose of repair. This process can be fully reflected by the on-site construction situation, as shown in Figure2.Figure 2
Polymer grouting repair construction.What’s more, in order to verify the feasibility of the polymer grouting repair method, core sampling was carried out on the repaired road in the actual working conditions. The core drilling sampling effect is shown in Figure3. It can be seen that the area of road disease has been completely filled with polymer materials, and the repair effect was perfect.Figure 3
Verification of coring after polymer grouting.


## 2.1. Polymer Grouting Material

The polymer grouting material used in this paper was mainly composed of polyether polyol, polyisocyanate, foaming agent, catalyst, foam stabilizer, and various other auxiliary agents. The chemical polymerization reactions that take place mainly include foaming reactions and gelling reactions [11–13]. The foaming reaction refers to the chemical reaction between polyisocyanate groups and hydroxyl groups, mainly generating carbon dioxide and urea, and generating a large amount of heat. This reaction is a key factor in the formation of polymer foams and directly affects the mechanical strength of the formed polymer foams. The reaction equation is shown in formula (1) [14, 15]. The gel reaction mostly refers to the chemical reaction between the –NCO group of the isocyanate and the –OH group of the polyol to generate a carbamate group and generate a certain amount of heat. The reaction equation is shown in formula (2) [16, 17].(1)2R−NCO+H2O⟶R−NH−CO−NH−R+CO2+thermal energy,(2)R−NCO+R′−OH⟶R−NH−CO−O−R′+thermal energy,


## 2.2. Principle of Polymer Grouting Filling

When repairing the longitudinal joints of the old and new subgrades of the renovated and expanded expressway, the polymer grouting material was injected into the void area by the high-pressure grouting gun through the grouting hole [18–22]. In the void area, the polymer grouting material undergoes a rapid curing reaction and diffuses in the crack to form a foam with a certain strength. Since the degree of curing reaction was relatively severe, the foam body has a large expansion force during the formation process, and the generated foam body does not react with water. The repair principle is shown in Figure 1.Figure 1
Principle of polymer grouting repair.When the hollow area of the roadbed is filled with the polymer grouting material, the liquid water will also be squeezed out through the unused grouting pipe next to it, and the weak and loose soil under the polymer grouting material will also be squeezed and compacted, so as to finally achieve the purpose of repair. This process can be fully reflected by the on-site construction situation, as shown in Figure2.Figure 2
Polymer grouting repair construction.What’s more, in order to verify the feasibility of the polymer grouting repair method, core sampling was carried out on the repaired road in the actual working conditions. The core drilling sampling effect is shown in Figure3. It can be seen that the area of road disease has been completely filled with polymer materials, and the repair effect was perfect.Figure 3
Verification of coring after polymer grouting.


## 3. Mechanical Correspondence Model

### 3.1. Pavement Structure and Calculation Parameters

The crack shape of the road surface at the junction of the old and new subgrades in the reconstruction and expansion of the expressway is shown in Figure4. As can be seen from Figure 4, the width and length of the cracks were relatively prominent, which has seriously affected the safety of road traffic. According to the field investigation and construction data, the typical subgrade structural parameters of the reconstruction and expansion expressway selected in this paper are shown in Tables 1 and 2. In addition, according to relevant laboratory tests, the elastic modulus of the 0.3 g/cm3 polymer foam is 25000 MPa, and the Poisson’s ratio is 0.12.Figure 4
Fracture morphology of joint.Table 1
Old road structure and parameters.
Old road structureElastic modulus (MPa)Poisson’s ratioAC-13 overlay (4 cm)12000.23Medium grain asphalt concrete (4 cm)10000.25Coarse grained asphalt concrete (5 cm)9000.25Coarse grained asphalt concrete (7 cm)9000.25Cement stabilized macadam (32 cm)13000.32Cement-lime stabilized soil (18 cm)6000.35Soil foundation500.40Table 2
New road structure and parameters.
New road structureElastic modulus (MPa)Poisson’s ratioAC-13 (4 cm)12000.23AC-20 (6 cm)11000.25ATB-25 (12 cm)10000.25Cement stabilized macadam (32 cm)13000.32Cement-lime stabilized soil (16 cm)6000.32Soil foundation400.40


### 3.2. Three-Dimensional Road Model

Vehicle load is an important factor affecting road stability [23–27]. In order to carry out the research on the mechanical response of polymer grouting before and after repairing the longitudinal cracks of the expressway, a three-dimensional road mechanics calculation model as shown in Figure 5 was established in this paper. The width of the subgrade of the entire road model was 20 m, the filling height of the roadside slopes on both sides was 3 m, the slope ratio was 1 : 1.5, the left and right edges of the model were 10 m away from the slope foot, and the total height of the model was 13 m. In the model, the width of longitudinal cracks was set to 10 cm, and a void area of 1 m × 0.1 m was set between the new subgrade filling soil foundation and the cement-lime stabilized soil sub-base. The boundary conditions of the model: the left and right boundaries of the model were set with position constraints in the X and Z directions, the bottom of the model was set with displacement constraints in the three directions of X, Y, and Z, and the traffic load acts on the junction of the old and new subgrades.Figure 5
Mechanical response model.


## 3.1. Pavement Structure and Calculation Parameters

The crack shape of the road surface at the junction of the old and new subgrades in the reconstruction and expansion of the expressway is shown in Figure4. As can be seen from Figure 4, the width and length of the cracks were relatively prominent, which has seriously affected the safety of road traffic. According to the field investigation and construction data, the typical subgrade structural parameters of the reconstruction and expansion expressway selected in this paper are shown in Tables 1 and 2. In addition, according to relevant laboratory tests, the elastic modulus of the 0.3 g/cm3 polymer foam is 25000 MPa, and the Poisson’s ratio is 0.12.Figure 4
Fracture morphology of joint.Table 1
Old road structure and parameters.
Old road structureElastic modulus (MPa)Poisson’s ratioAC-13 overlay (4 cm)12000.23Medium grain asphalt concrete (4 cm)10000.25Coarse grained asphalt concrete (5 cm)9000.25Coarse grained asphalt concrete (7 cm)9000.25Cement stabilized macadam (32 cm)13000.32Cement-lime stabilized soil (18 cm)6000.35Soil foundation500.40Table 2
New road structure and parameters.
New road structureElastic modulus (MPa)Poisson’s ratioAC-13 (4 cm)12000.23AC-20 (6 cm)11000.25ATB-25 (12 cm)10000.25Cement stabilized macadam (32 cm)13000.32Cement-lime stabilized soil (16 cm)6000.32Soil foundation400.40


## 3.2. Three-Dimensional Road Model

Vehicle load is an important factor affecting road stability [23–27]. In order to carry out the research on the mechanical response of polymer grouting before and after repairing the longitudinal cracks of the expressway, a three-dimensional road mechanics calculation model as shown in Figure 5 was established in this paper. The width of the subgrade of the entire road model was 20 m, the filling height of the roadside slopes on both sides was 3 m, the slope ratio was 1 : 1.5, the left and right edges of the model were 10 m away from the slope foot, and the total height of the model was 13 m. In the model, the width of longitudinal cracks was set to 10 cm, and a void area of 1 m × 0.1 m was set between the new subgrade filling soil foundation and the cement-lime stabilized soil sub-base. The boundary conditions of the model: the left and right boundaries of the model were set with position constraints in the X and Z directions, the bottom of the model was set with displacement constraints in the three directions of X, Y, and Z, and the traffic load acts on the junction of the old and new subgrades.Figure 5
Mechanical response model.


## 4. Calculation Results and Analysis

### 4.1. Distribution Law of Displacement and Settlement of Road Surface

Under the condition of 100 kN driving load cyclic action of 1.0 × 104 times, the change rule of road surface settlement and displacement before and after polymer grouting repair is shown in Figure 6. It can be seen from Figure 6 that with the increase of the distance from the load center, the displacement and settlement of the road surface gradually decrease. In addition, after the polymer grouting repair, the displacement and settlement of the entire road surface were significantly reduced. Before the polymer grouting repair, at the load action position, the maximum displacement and settlement of the left subgrade was 21 mm, and the maximum displacement and settlement of the new subgrade on the right was 32 mm. After polymer grouting repair, the maximum displacement and settlement of the left subgrade was 17 mm, which was 19% less than that before polymer grouting; the maximum displacement and settlement of the right subgrade was only 10 mm, which was higher than 69% reduction before grouting.Figure 6
Distribution law of surface displacement and settlement.The following will analyze the reasons for the above phenomena: there were longitudinal cracks at the junction of the old and new subgrades, and there was a void area between the new subgrade filling soil base and the cement-lime stabilized soil sub-base. When the traffic load acts on the joint, with the increase of the number of loads, the new subgrade has a large amount of displacement and settlement due to the existence of voiding diseases. After the polymer grouting repair, the diseases in the void area of the new subgrade were repaired, and the cracks at the junction of the old and new subgrades were repaired. Therefore, the displacement and settlement of the new subgrade were significantly reduced. In addition, the polymer grouting material will produce adhesive force with the roadbed materials on both sides while filling the crack area. When the traffic load acts, the critical surface between the polymer grouting material and the roadbed material on both sides will generate upward shear force, thereby reducing the displacement and settlement of the road surface.


### 4.2. Distribution Law of Dynamic Stress Peak Value of Road Surface

The dynamic stress peak distribution law of the road surface after polymer grouting repair is shown in Figure7. It can be seen from Figure 7 that the maximum value of the dynamic stress peak value of the old and new subgrade road surfaces was located at the load action position, and with the increase of the distance from the load action position, the dynamic stress peak value gradually decreases, and the dynamic stress peaks of the old and new subgrades show an M-shaped distribution as a whole with the change of the load action position distance. After the polymer grouting repair, the dynamic stress peak value of the old and new subgrade road surfaces has decreased. The stress peak value of the old subgrade surface was reduced from 50 kPa to 45 kPa, a reduction of 10%; the new subgrade surface stress peak value was reduced from 42 kPa to 35 kPa, a reduction of 17%. The percentage of peak value reduction of dynamic stress on road surface before and after grouting is shown in Table 3. The calculation results show that the polymer grouting filling can enhance the bearing capacity of the roadbed. In addition, the internal stress generated by the new subgrade structure was smaller, and the bearing capacity was higher than that of the old subgrade.Figure 7
Peak value distribution of dynamic stress on road surface.Table 3
Percentage reduction of peak dynamic stress of road surface before and after grouting.
Old subgrade (kPa)New subgrade (kPa)Percentage reduction (%)Before polymer grouting504210After polymer grouting453517


### 4.3. Distribution Law of Dynamic Stress with Depth

The variation law of dynamic stress with depth at the loading position of old and new subgrades is shown in Figures8 and 9. It can be seen from Figures 8 and 9 that under the same axial load, the dynamic stress gradually decreases with the increase of the subgrade depth. At the same depth, the dynamic stress increases with the increase of the axle load, and the increase gradually decreases with the increase of the depth. The comparative analysis of Figures 8 and 9 shows that after the polymer grouting repair, the dynamic stress of the new subgrade was significantly smaller than that of the old subgrade. In addition, when the depth is in the range of 0.5 m to 1.0 m, the dynamic stress attenuation degree of the new subgrade was significantly lower than that of other depths. The above calculation results show that the dynamic stress gradually attenuates with the increase of the subgrade depth. After the polymer grouting material fills the void area, under the action of the vehicle axle load, it will change the transmission law of the original stress, resulting in the phenomenon of stress concentration.Figure 8
Variation of dynamic stress of old subgrade with depth.Figure 9
Variation of dynamic stress of new subgrade with depth.


### 4.4. Variation Law of Interlayer Stress Response

Under different axial loads, the maximum tensile stress and tensile strain of the upper interface of the void area before and after polymer grouting repair are shown in Figure10. It can be seen from Figure 10 that before the polymer grouting filling, with the increase of the axial load, the interfacial tensile stress on the void area increases from 0.46 MPa to 0.68 MPa. After polymer grouting filling, the interfacial tensile stress in the void area increased from 0.21 MPa to 0.33 MPa. Under the same axial load level, the tensile stress and tensile strain after polymer grouting filling were significantly lower than those before grouting filling.Figure 10
Variation law of interlayer stress response in void area.The following will analyze the reasons for the above phenomena: before the polymer grouting repair, in the process of downward transfer of the axial load stress, due to the existence of the void area, the transmitted stress produces a large lateral component on the interface of the void area, which causes the generation of tensile strain. With the increase of the axial load, the transverse component generated by the interface on the void area will also gradually increase, so the tensile stress and tensile strain will gradually increase with the increase of the axial load. After the polymer grouting repair, the critical surface formed between the polymer grouting material and the base material has a certain shear strength, which reduces the interlayer tensile stress and tensile strain and improves the bearing capacity of the roadbed.


## 4.1. Distribution Law of Displacement and Settlement of Road Surface

Under the condition of 100 kN driving load cyclic action of 1.0 × 104 times, the change rule of road surface settlement and displacement before and after polymer grouting repair is shown in Figure 6. It can be seen from Figure 6 that with the increase of the distance from the load center, the displacement and settlement of the road surface gradually decrease. In addition, after the polymer grouting repair, the displacement and settlement of the entire road surface were significantly reduced. Before the polymer grouting repair, at the load action position, the maximum displacement and settlement of the left subgrade was 21 mm, and the maximum displacement and settlement of the new subgrade on the right was 32 mm. After polymer grouting repair, the maximum displacement and settlement of the left subgrade was 17 mm, which was 19% less than that before polymer grouting; the maximum displacement and settlement of the right subgrade was only 10 mm, which was higher than 69% reduction before grouting.Figure 6
Distribution law of surface displacement and settlement.The following will analyze the reasons for the above phenomena: there were longitudinal cracks at the junction of the old and new subgrades, and there was a void area between the new subgrade filling soil base and the cement-lime stabilized soil sub-base. When the traffic load acts on the joint, with the increase of the number of loads, the new subgrade has a large amount of displacement and settlement due to the existence of voiding diseases. After the polymer grouting repair, the diseases in the void area of the new subgrade were repaired, and the cracks at the junction of the old and new subgrades were repaired. Therefore, the displacement and settlement of the new subgrade were significantly reduced. In addition, the polymer grouting material will produce adhesive force with the roadbed materials on both sides while filling the crack area. When the traffic load acts, the critical surface between the polymer grouting material and the roadbed material on both sides will generate upward shear force, thereby reducing the displacement and settlement of the road surface.


## 4.2. Distribution Law of Dynamic Stress Peak Value of Road Surface

The dynamic stress peak distribution law of the road surface after polymer grouting repair is shown in Figure7. It can be seen from Figure 7 that the maximum value of the dynamic stress peak value of the old and new subgrade road surfaces was located at the load action position, and with the increase of the distance from the load action position, the dynamic stress peak value gradually decreases, and the dynamic stress peaks of the old and new subgrades show an M-shaped distribution as a whole with the change of the load action position distance. After the polymer grouting repair, the dynamic stress peak value of the old and new subgrade road surfaces has decreased. The stress peak value of the old subgrade surface was reduced from 50 kPa to 45 kPa, a reduction of 10%; the new subgrade surface stress peak value was reduced from 42 kPa to 35 kPa, a reduction of 17%. The percentage of peak value reduction of dynamic stress on road surface before and after grouting is shown in Table 3. The calculation results show that the polymer grouting filling can enhance the bearing capacity of the roadbed. In addition, the internal stress generated by the new subgrade structure was smaller, and the bearing capacity was higher than that of the old subgrade.Figure 7
Peak value distribution of dynamic stress on road surface.Table 3
Percentage reduction of peak dynamic stress of road surface before and after grouting.
Old subgrade (kPa)New subgrade (kPa)Percentage reduction (%)Before polymer grouting504210After polymer grouting453517


## 4.3. Distribution Law of Dynamic Stress with Depth

The variation law of dynamic stress with depth at the loading position of old and new subgrades is shown in Figures8 and 9. It can be seen from Figures 8 and 9 that under the same axial load, the dynamic stress gradually decreases with the increase of the subgrade depth. At the same depth, the dynamic stress increases with the increase of the axle load, and the increase gradually decreases with the increase of the depth. The comparative analysis of Figures 8 and 9 shows that after the polymer grouting repair, the dynamic stress of the new subgrade was significantly smaller than that of the old subgrade. In addition, when the depth is in the range of 0.5 m to 1.0 m, the dynamic stress attenuation degree of the new subgrade was significantly lower than that of other depths. The above calculation results show that the dynamic stress gradually attenuates with the increase of the subgrade depth. After the polymer grouting material fills the void area, under the action of the vehicle axle load, it will change the transmission law of the original stress, resulting in the phenomenon of stress concentration.Figure 8
Variation of dynamic stress of old subgrade with depth.Figure 9
Variation of dynamic stress of new subgrade with depth.


## 4.4. Variation Law of Interlayer Stress Response

Under different axial loads, the maximum tensile stress and tensile strain of the upper interface of the void area before and after polymer grouting repair are shown in Figure10. It can be seen from Figure 10 that before the polymer grouting filling, with the increase of the axial load, the interfacial tensile stress on the void area increases from 0.46 MPa to 0.68 MPa. After polymer grouting filling, the interfacial tensile stress in the void area increased from 0.21 MPa to 0.33 MPa. Under the same axial load level, the tensile stress and tensile strain after polymer grouting filling were significantly lower than those before grouting filling.Figure 10
Variation law of interlayer stress response in void area.The following will analyze the reasons for the above phenomena: before the polymer grouting repair, in the process of downward transfer of the axial load stress, due to the existence of the void area, the transmitted stress produces a large lateral component on the interface of the void area, which causes the generation of tensile strain. With the increase of the axial load, the transverse component generated by the interface on the void area will also gradually increase, so the tensile stress and tensile strain will gradually increase with the increase of the axial load. After the polymer grouting repair, the critical surface formed between the polymer grouting material and the base material has a certain shear strength, which reduces the interlayer tensile stress and tensile strain and improves the bearing capacity of the roadbed.


## 5. Conclusions

(1)
With the increase of the number of loads, the displacement and settlement of the new subgrade is obviously larger than that of the old subgrade due to void damage. After the polymer grouting repair, the shear force was generated between the polymer grouting material and the subgrade materials on both sides, so that the cracks in the void area and the joint of the new subgrade can be repaired, so as to reduce the displacement and settlement of the road surface.(2)
The maximum value of the dynamic stress peak value of the new and old subgrade road surface was located at the load action position, and with the increase of the distance from the load action position, the dynamic stress peak value gradually decreases, and the overallM-shaped distribution. After the polymer grouting repair, the dynamic stress peak value of the old and new subgrade road surfaces has decreased.(3)
Under the same axial load, the dynamic stress gradually decreases with the increase of the subgrade depth. At the same depth, the dynamic stress increases with the increase of the axle load, and the increase gradually decreases with the increase of the depth. After the polymer grouting repair, the original stress transmission law is changed, so that the dynamic stress of the new subgrade is significantly smaller than that of the old subgrade. After the polymer grouting repair, the critical surface formed between the polymer grouting material and the base material has a certain shear strength, which reduces the interlayer tensile stress and tensile strain and improves the bearing capacity of the roadbed.



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*Source: 5760674-2022-04-29.xml*