Analysis of Factors Affecting the Jumping of Bridgeheads by Flexible Trench of Geocells
Abstract: The finite element software ABAQUS is used to study the vertical displacement of the top of the embankment before and after reinforcement and the horizontal displacement of the foundation under the slope. The wholesale HDPE geocell modulus, packing parameters, flexible spacing of the slabs, the number of layers and the height of the embankment are analyzed. The effect on the displacement of the embankment. The results show that the HDPE geocell for sale flexible paving system can effectively reduce the uneven settlement of the transition between road and bridge, and when the elastic modulus of the high quality HDPE geocell is increased or the number of layers is increased, the effect of the bridgehead jumping will be significantly improved.
Keywords: flexible strap; bridgehead jump; numerical analysis; differential settlement;
The construction of roads on soft soils often leads to diseases caused by large deformations, and the differential settlement of foundations is the main cause of this disease. Especially in the transition section of roads and bridges, it is easy to cause the phenomenon of bridgehead jumping, which seriously affects the use of high-grade roads. Many engineering practices have shown that reinforcement in the embankment can improve the performance of the embankment and improve its stability. At present low price HDPE geocell, domestic and foreign scholars have conducted a series of studies on embankment reinforcement. Yang Lu and other  through the indoor small scale model experiment, the geogrid reinforced structure can effectively control the uneven settlement of the highway transition section. Wang Guangyue et al.  used the limit equilibrium method to analyze the stability of the geotechnical flexible slope protection under rainfall conditions. The calculation results show that the stability of the cell protection system depends on the cell soil moisture content, the rivet spacing, the cell slope length, and the edge. The slope angle increases and the influence is significant. Xie Yongli et al  through the field test, combined with finite element analysis, studied the mechanism of the uneven settlement of the geotechnical chamber. Yang Xiaohua et al [4–5] used finite element software to numerically analyze the shallow saturated yellow soil foundation and the railway weak bed in wholesale HDPE geocell, and combined with the actual engineering case, the HDPE geocell manufacturers can effectively restrain the lateral displacement and diffusion of weak foundation. Stress, to achieve the purpose of strengthening the foundation. Su Yonghua , Ma Guodong , Liu Zhu  and so on used the actual engineering to establish a finite element model, and analyzed its reinforcement mechanism, compared the influence of different reinforcement types on the stability of embankment, pointing out that the effect of HDPE geocell for sale is better than geotechnical The grille should be more prominent. Zhang Hongguang  and Yu Yonghua  carried out model experiments and numerical simulations on the geotechnical flexible slabs respectively. It was concluded that the flexible slab system can better eliminate the bridgehead jumper than the simple high quality HDPE geocell reinforced. The geotechnical flexible pavement is a new method for the treatment of post-filling soil. It is clear that it has a great significance for the optimization of the design and mechanism of the trip. With the maturity of finite element software at home and abroad and the development of material constitutive models, 3D numerical simulation technology can make a more reasonable analysis of different working conditions and boundary conditions. In this paper, the large-scale finite element ABAQUS is used to analyze the effects of wholesale HDPE geocell modulus, packing parameters, flexible lap spacing, a number of layers and embankment height on the embankment reinforcement effect.
1. Model and parameters
Referring to the actual project, consider that the embankment is symmetrical along the left and right low price HDPE geocell, taking half of the embankment as a calculation model. The top of the embankment is 14m wide, the embankment fill height is 6m, the slope is 1:1.5, and the calculated length is 30m. Below the embankment is a soft soil foundation with a depth of 15m, a calculated width of 43m, a calculated length of 30m, and a total of 4 geotechnical compartments on the back of the platform. The tops are double-layered and the floor height is 20cm. The calculation model is shown in Figure 1.
Figure 1 calculation model (unit: cm)
1.2 Material parameters
The embankment fill and foundation soil are modeled by the Mohr-Coulomb model provided by ABAQUS and are based on the ideal plastic Mohr-Coulomb yield criterion and the unrelated flow rule. The embankment filling parameters are elastic modulus 25 MPa, Poisson’s ratio 0.3, gravity 20 kN·m-3, cohesive force C=30 kPa, internal friction angle φ=30°. The foundation is soft clay, and its calculation parameters are elastic modulus 10 MPa, Poisson’s ratio 0.35, gravity 17 kN·m-3, cohesive force C=15 kPa, internal friction angle φ=10°. The wholesale HDPE geocell structural layer adopts a linear elastic model. The elastic modulus is twice that of the embankment, 50 MPa, the Poisson’s ratio is 0.15, and the gravity is 20 kN·m-3.
1.3 Boundary conditions and loads
For the gravity abutment, in the actual construction, the high quality HDPE geocell is anchored on the abutment and backfilled. Therefore, in the finite element analysis, the wholesale HDPE geocell is in contact with the abutment, and the displacement in the x, y, and z directions of the connection end is limited to zero. The specific boundary conditions of each part of the model are shown in Table 1. The self-heavy load of each structural layer is applied according to the weight of the given material, and the road load and the vehicle load are equivalent to a uniform load, and the value is 50 kPa.
Table 1 boundary conditions
2. Geocell granules
The HDPE geocell manufacturers flexible paving is composed of a multi-layer wholesale HDPE geocell composite with one end anchored to the abutment and the other end extending into the embankment for a certain length, and the distribution length of each geotechnical chamber is a gradient from the embankment to the bottom of the embankment. A wedge-type flexible reinforcement system.
2.1 Vertical displacement of the reinforced embankment
The vertical displacement curve of the central axis of the top surface of the embankment before and after reinforcement is shown in Fig. 2. It can be seen from Fig. 2 that when the embankment is not reinforced low price HDPE geocell, the vertical displacement of the top of the embankment near the abutment end is about 9 cm, and the longitudinal direction along the embankment is in a straight line trend. There is no transition between the road and the bridge, so it is easy to be on the road and bridge. The transition section forms a stepped settlement, which causes the bridgehead to jump. After the embankment is treated by reinforcement, the vertical displacement curve is parabolic in the treatment area of the bridge head. The uneven settlement of the transition section of the road and bridge can be smoothly transitioned in a long-range, and the maximum settlement value is lower than that of the unreinforced embankment. Compared with the rigid slab, the joint between the flexible slab treatment zone and the untreated zone does not cause a second jump phenomenon. This shows that the wholesale HDPE geocell flexible slab can effectively reduce the settlement of the top surface of the embankment and improve the phenomenon of bridgehead jumping caused by differential settlement.
Figure 2 Vertical displacement curve of the top surface of the embankment
2.2 Horizontal displacement of the foundation under the slope
The HDPE geocell manufacturers are used in the process of treating embankment filling and interacts with the filler to form a composite with strong stiffness and tensile strength. It also provides lateral restraint to the surrounding soil, which can effectively limit the lateral deformation of the foundation soil. Figure 3 shows the horizontal displacement curve of the foundation at 1m and 15m from the back of the abutment before and after reinforcement.
It can be seen from Fig. 3 that the horizontal displacement of the soil under the foot of the slope presents an arch shape that protrudes to the right. When the reinforcement is not reinforced, the maximum horizontal displacement is 28.9 mm. After the reinforcement, the top of the arch is significantly reduced. The maximum horizontal displacement of the body is 21.9mm, which indicates that the HDPE geocell for sale flexible slab can significantly reduce the horizontal displacement of the soft soil foundation. At the same time low price HDPE geocell, for the unreinforced embankment, the horizontal displacement curve of the foundation soil in the middle part of the embankment near the back of the platform is basically coincident, and after the reinforcement, the horizontal displacement of the foundation near the fixed end of the platform is significantly smaller than that in the middle of the embankment. The maximum horizontal displacement of the two at the foot of the slope differs by 8.2 mm. This is because one end of the high quality HDPE geocell is anchored to the abutment and rigidly connected with the abutment, which effectively limits the lateral displacement of the soil near the abutment and makes the soft soil The integrity of the foundation has been strengthened.
Figure 3 horizontal displacement curve of the slope
3. Analysis of factors affecting the behavior of geocells
3.1 Geocell Modulus
The geocell is regarded as a linear elastomer, and the tensile strength index of the wholesale HDPE geocell is characterized by elastic modulus. The elastic modulus of the HDPE geocell manufacturers was 45, 50, 60 and 75 MPa, respectively, and the simulation comparison analysis was carried out. The results are shown in Fig. 4. It can be seen from Fig. 4 that the elastic modulus can directly affect the vertical displacement of the embankment. The greater the elastic modulus of the high quality HDPE geocell, the greater the compressive capacity and the bending stiffness, and the constraints on the soil. The stronger the ability, the smaller the displacement of the top surface of the roadbed. However, this effect is only in the range of laying HDPE geocell for sale and has no significant effect beyond the length of the HDPE geocell manufacturers. The vertical displacement of the soil tends to be uniform.
Figure 4 Relationship between elastic modulus and vertical displacement
3.2 Filling parameters
Keep the other material parameters in the calculation model unchanged, take the deformation modulus E of the embankment fillers to 20, 25, 35 and 50 MPa respectively, and the high quality HDPE geocell modulus to take 2 times the modulus of the filler, and compare the four cases. The result is shown in Figure 5.
It can be seen from Fig. 5 that the change of the embankment packing modulus has a great influence on the vertical displacement of the embankment. As the modulus of the filler increases, the displacement of the embankment gradually decreases. Especially in the case of a small filler modulus low price HDPE geocell, this change has a greater impact. It can be seen that the difference between the two curves of E=20MPa and E=25MPa is more obvious than the difference between E=35MPa and E=50MPa. This also indicates that the influence of modulus on displacement is weaker than a certain range.
Figure 5 Relationship between fill modulus and vertical displacement
3.3 Flexible strap arrangement spacing
Keep the other conditions of the model unchanged, and set the flexible lap spacing to 1.4, 1.5, 1.6 and 1.8m, and simulate the four cases. The vertical displacement curve of the simulated subgrade is shown in Fig. 6. Show.
It can be seen from Fig. 6 that the spacing of the HDPE geocell for sale layout has an influence on the vertical displacement of the embankment. However, the impact is not singular. Compared with the far end of the bridge, the reduction of the arrangement spacing is more obvious for the settlement of the near abutment. In the range of 1 to 4 m from the abutment, the settlement value with a spacing of 1.4 m is smaller than the case where the spacing is 1.5, 1.6 and 1.8 m, and the maximum difference of settlement occurs at a distance of 2 m from the abutment. For the latter three kinds of arrangement spacing, although the settlement will increase with the increase of the arrangement spacing, the difference of the settlement curves is small HDPE geocell manufacturers, which indicates that the arrangement spacing only affects the settlement of the embankment within a certain range. It is recommended to arrange the spacing of the project to be about 1.5m.
Figure 6 arrangement spacing and vertical displacement relationship
3.4 Flexible slab layout layers
Under the condition that the remaining parameters are unchanged, the influence of the number of layers of flexible slabs on the embankment settlement is analyzed low price HDPE geocell. The simulation results show that the number of layers is 3 to 6 layers, and the vertical displacement curve of the top surface of the subgrade is shown in Fig. 7.
It can be seen from Fig. 7 that the number of layers of the flexible strap has a certain influence on the settlement. At the near abutment end, when the number of flexible slabs is 3 to 5, the settlement value decreases with the increase of the number of layers, but when 6 layers of flexible slabs are arranged HDPE geocell manufacturers, the settlement value is larger than the arrangement at the near abutment end. The 5th-floor case. At the far bridge end after 14m from the abutment, the effect of reducing the settlement of the embankment is more significant, which indicates that the increase of the number of layers makes the decrease of the settlement value gradually develop to a distant place.
Figure 7 layout layer and vertical displacement relationship
3.5 Embankment height
Keep the parameters of the model unchanged, and compare the heights of the embankments to 6, 8, 10 and 12m. The results are shown in Figure 8.
As can be seen from Figure 8, the change in the height of the embankment has a significant effect on the vertical displacement of the top of the embankment low price HDPE geocell. At the near abutment end, with the increase of the height of the embankment, the flexible grid of the HDPE geocell for sale can significantly reduce the vertical displacement of the embankment, and the vertical displacement of the embankment with a height of 12m is smaller than the displacement of the height of 6, 8 and 10m. The increase in the height of the embankment results in a greater increase in the vertical displacement. Although the flexible lap can reduce the settlement of the subgrade, it is gradually beyond the range of 14m from the back of the platform, and the influence of the laying of the high quality HDPE geocell is gradually weakened, which is not enough to offset the embankment. The increase in the vertical displacement of the foundation caused by the increase in height.
Figure 8 Relationship between height and vertical displacement of the embankment
In this paper, a large-scale finite element software ABAQUS is used to establish a three-dimensional model of the reinforced embankment and soft soil foundation for numerical analysis low price HDPE geocell, and the following conclusions are obtained.
(1) The HDPE geocell for sale flexible paving system can effectively digest the uneven settlement caused by the soft soil foundation, control and coordinate the settlement difference between the embankment and the abutment transition section, thus achieving the purpose of improving the bridgehead jumping.
(2) The high quality HDPE geocell is arranged in the embankment and forms a composite with the filler, which provides lateral restraint to the surrounding soil and reduces the horizontal displacement of the foundation soil.
(3) The greater the elastic modulus of the HDPE geocell manufacturers, the more obvious the restraining effect on the soil, and the smaller the vertical displacement. Therefore, in the actual engineering application, the material of the cell with large modulus and strong bending rigidity should be used as much as possible.
(4) Increasing the number of layers of flexible straps can effectively reduce the settlement of the foundation. However, when the HDPE geocell for sale are arranged below 5, the increase in the number of foundations has limited effect on the foundation reinforcement. It is recommended that the flexible slabs in the actual project should be arranged for more than 5 layers.