Experimental Study on Mechanical Properties of Steel-Plastic Bidirectional Geogrid

Based on research into ordinary plastic geogrids, specially treated high-strength steel wires are fused with polyethylene (PE), and additives are added to create high-strength tensile strips. The surface is then roughened to produce a composite reinforced geotextile strip with excellent mechanical properties. These composite reinforced geotextile strips are arranged and woven at fixed intervals in both longitudinal and transverse directions, and their joints are welded using fusion welding technology to ultimately produce a steel-plastic bidirectional geogrid.
By changing the diameter and number of steel wire ropes, the tensile strength of the reinforcing strips is altered. This not only enhances the tensile strength and creep resistance of the geogrid but also extends its service life. It is suitable for most engineering construction projects, including coal mines, highways, railways, airports, well irrigation, and civil buildings.

During engineering design and construction, the mechanical performance evaluation indicators of the steel-plastic bidirectional geogrid vary depending on the load it bears. The mechanical properties of steel-plastic bidirectional geogrids mainly include tensile strength, friction test strength, pull-out test strength, and interaction with the fill material.

During engineering construction, the tensile performance of steel-plastic bidirectional geogrids varies due to different temperatures, loads, and fill material conditions. Therefore, tensile, deflection, and creep comparative tests were conducted on steel-plastic single- and bidirectional geogrids to study their mechanical properties.

Steel-plastic bidirectional geogrids are composite flexible materials, typically bearing loads from the external environment through tensile strength. Tensile strength is a key mechanical property indicator for geosynthetic materials. The main performance parameters of the four groups of steel-plastic bidirectional geogrids of the same specifications tested were: longitudinal and transverse tensile strengths much greater than 50 kN/m, longitudinal and transverse elongation rates not exceeding 13%, and tensile strength much greater than 35 kN/m at an elongation of 5%.
The results of the uniform tensile test of the steel-plastic bidirectional geogrid are shown in Figure 1. As shown in Figure 1, the stretching process of the four sets of steel-plastic gratings can be roughly divided into three stages: low load with large deformation stage, high load with small deformation stage, and fracture stage.

Steel-plastic bidirectional geogrids

During the initial loading phase of the test, i.e., the low-load, large-deformation stage, the tensile load was small, but the tensile deformation displacement was large, with all four groups of tests ultimately reaching approximately 19 mm.
In the second stage, i.e., the high-load, small-deformation stage, as the test load increased, the deformation displacement of the steel-plastic geogrid also gradually increased. As shown in Figure 1, the tensile curve showed a large increase, but within the same load difference, the displacement change in the second stage was smaller compared to the first stage, with the maximum tensile length of the first group being only 6 mm.
In the third stage, the fracture stage, after the test load exceeded 11 kN, all four groups of steel-plastic geogrids sequentially entered the fracture stage. During the fracture stage test, the steel wires in the geotextile strips inside the steel-plastic bidirectional geogrid began to break one by one, causing the tensile curve in Figure 1 to drop sharply, and the tensile strength of the steel-plastic bidirectional geogrid to rapidly decrease to 0.
In summary, the tensile strength of the steel-plastic bidirectional geogrid is affected by the steel wires in the geotextile strips; after the steel wires break, the tensile strength of the steel-plastic bidirectional geogrid rapidly decreases to 0.

Due to the high flexibility of the steel-plastic biaxial geogrid, its deflection cannot be directly measured. Therefore, the steel-plastic biaxial geogrid was modified by placing it within a concrete slab, and the deflection of the reinforced slab was then tested.
To ensure the reliability of the test data, six slabs were tested, considering all influencing factors.
Two types of concrete slabs were fabricated, one with a steel-plastic biaxial geogrid and the other with Q235 metal mesh. The concrete slab dimensions were 1000mm × 1000mm × 100mm. To ensure the reliability of the test data, three slabs of each type were fabricated. The deflection test results are shown in Figure 2.

Deflection Test

(1) The two identical steel-plastic biaxial geogrid cast-in-place slabs, GSW-1 and GSW-2, exhibited similar stress changes. From the initial application of the load to 10 seconds after the load was applied, the pressure that GSW-1 could withstand changed relatively slowly, increasing only to 1 kN, with almost no change in displacement. After 20 seconds of load application, the stress began to increase, the displacement increased, and cracks began to appear in the slab, leading to a decrease in stress. As the cracks widened, the geogrid in the slab began to function, and the stress increased again. When the load application time reached 45 seconds, the stress reached its maximum value of 34.1 kN, and the displacement also reached its maximum value of 44.2 mm. Both values stopped increasing, and the slab yielded.

(2) Due to the inclination of the slab, the stress on the slab was uneven, causing the stress in GSW-2 to increase rapidly after 10 seconds of compression, but no change in displacement occurred. When the applied load reached 40 seconds, cracks appeared in GSW-2, the stress began to decrease, and the displacement began to increase. As the cracks widened, the grid within the slab began to function, causing the stress to rise again to 27.5 kN. The grid within the slab then exhibited wire breakage, and the stress rapidly decreased.

Grid creep characteristics refer to the property of a grid deforming over time under constant external load.
Grids are mesh structures made from high-molecular polymers through a series of complex processes. Their creep performance directly affects the long-term stability of reinforced structures. The creep effect of reinforced structures leads to changes in the stress state, resulting in losses of overall building stability, excessive deformation, and other disasters. Therefore, the creep performance of the grid is crucial for maintaining the long-term stability of its tensile strength.
In practical engineering applications, under different temperatures and loads, the grid undergoes creep deformation, significantly weakening its reinforcing function and even causing the building to lose overall stability.
Figure 3 shows the creep curves of the steel-plastic bidirectional geogrid strain versus time under the same tensile force (50kN/m) and two different ambient temperatures of 20℃ and 40℃, obtained through experimental measurements.

Creep Test

As shown in Figure 3, when the ambient temperature is 20℃, it takes about 100 hours for the strain to reach 20%; when the ambient temperature is 40℃, it only takes about 0.5 hours for the strain to reach 20%. This indicates that temperature has a significant impact on the steel-plastic biaxial geogrid, and the strain value gradually increases with increasing temperature.

The steel-plastic biaxial geogrid has good resistance to structural deformation, node torsion failure, and deformation settlement. It has high flexibility and elasticity, and the nodes are not easily torn. It can withstand multi-directional loads and effectively distribute the load.
The tensile process of the steel-plastic biaxial geogrid includes three stages: low load with large deformation, high load with small deformation, and fracture. The strength of the steel-plastic biaxial geogrid increases with increasing tensile rate.
The deflection deformation of the cast-in-place concrete biaxial slab with steel-plastic biaxial geogrid is divided into three stages: linear elastic stage, nonlinear stage, and yield stage. In the linear elastic stage of a two-way concrete slab, deflection is positively correlated with load. With the appearance of cracks, the reinforced slab enters a nonlinear stage, its stiffness decreases, and the deflection deformation becomes nonlinearly related to the load; the concrete slab loses its load-bearing capacity in this stage. In the yielding stage, the steel-plastic grating exhibits wire pulling, with individual reinforcing bars breaking, and the grating yields.
The strain-time relationship from the grating creep test shows that temperature affects the grating's creep: at lower temperatures, the creep is smaller; at higher temperatures, the creep changes more significantly and increases more rapidly.

Work with an experienced manufacturer offering consistent quality, flexible customization, and global export support for your projects.

Get a Free Quote