# Experimental Study on Creep Properties of Geogrid

**Abstract:** The creep of geogrid affects its application in engineering. In response to this problem, the creep test of wholesale fiberglass geogrid was carried out, and the creep strength reduction coefficient under different design years was obtained. The test results show that under the condition of low-stress ratio, the strain of fiberglass geogrid factory price increases with time, gradually becomes slower, and finally stabilizes. Under the condition of high-stress ratio, the strain of fiberglass geogrid for sale increases with time. Until the fracture; the greater the stress ratio of the specimen, the greater the strain generated during the same time; the strain value of the same size, the longer the strain ratio required, the higher the strain ratio required time Less; in the stress relaxation state of the high quality fiberglass geogrid, when the strain is kept constant, the load gradually decreases with time.

### introduction

In the process of using railway engineering, the fiberglass geogrid manufacturers are subjected to constant force for a long time in the soil or on the surface of the soil, which indicates that the actual application process is a long-term creep process. Whether the fiberglass geogrid factory price can work for a long time has a great relationship with its creep characteristics. Especially when the wholesale fiberglass geogrid is applied to the reinforcement of railway engineering, its creep performance is the most critical.

The factors affecting the creep of fiberglass geogrid manufacturers can be divided into external and internal factors. Internal factors mainly refer to the polymer type of material. The external factors mainly include sample size, humidity, load level, temperature, loading rate, and confinement constraints. The influence of temperature and load level on creep performance is the most obvious.

In this paper, the indoor long-term creep test of high quality fiberglass geogrid is carried out at different temperatures and different strain ratios. The characteristics of creep curve, load, and strain curve of fiberglass geogrid for sale are analyzed and compared, and the intensity-time equation is obtained. The allowable design strength of the sample under a certain design period is calculated, which provides scientific and accurate engineering design. Design parameters.

### 1. Test material

The EG90R uniaxially stretched plastic wholesale fiberglass geogrid was selected for indoor creep test. Five rib width and 1.5 m long grid were cut from the full-width unidirectional grid sample as the creep test specimen. The longitudinal ribs on both sides of the sample were cut with scissors. The sample had three complete ribs. The sample is shown in Figure 1. The basic mechanical properties of the grid samples are shown in Table 1.

### 2. Test method

In this section, the EG90R uniaxially stretched plastic high quality fiberglass geogrid is selected as the research object, and the indoor long-term creep test of the fiberglass geogrid for sale is carried out at different temperatures and different strain ratios. The test temperature, stress ratio, and creep load strength are shown in Table 2. The load is applied to the sample under a specified temperature environment, and the elongation of the sample is continuously recorded until the elongation of the sample exceeds 10% or the sample is broken, and the test is finished. The test is shown in Figure 2.

### 3. Test results and analysis

**3.1 Analysis of creep test results of the first 1000h geogrid**

For the fiberglass geogrid factory price EG90R under the condition of 20 °C temperature and different tension, the wholesale fiberglass geogrid strain obtained by the test changes with time within the first 1000h, and the curve is drawn as shown in Fig. 3.

It can be seen from Fig. 3 that at a temperature of 20 ° C, the grid samples exhibit substantially the same creep law when the stress ratio is less than 60%. Under the condition of low-stress ratio, the strain increases rapidly with time in the initial creep of fiberglass geogrid manufacturers, and the strain has a linear relationship with time. Then, the rate of increase in strain gradually decreases with time and finally stabilizes. Under high-stress ratio conditions, the strain of the fiberglass geogrid for sale increases rapidly with time. As the molecular chain inside the material is broken, the strain of the sample increases until the high quality fiberglass geogrid breaks.

At the same temperature, the larger the stress ratio of the sample, the greater the strain generated during the same time, but the two do not have a proportional relationship. At 20 ° C, when loaded at 1000 h, the strain produced by the grid samples at stress ratios of 40%, 45%, and 50% were 7.41%, 8.90%, and 10.90%, respectively. At a strain ratio of 60%, the sample was pulled off after being loaded for 229 hours.

**3.2 Isochronous creep of geogrid**

The curve drawn by the relationship between the strain and the strain ratio at a certain moment in the creep process of the wholesale fiberglass geogrid is called the isochronous creep curve, and the isochronous creep curve of the high quality fiberglass geogrid records that the sample is generated at a certain time. The relationship between strain, time and stress are three. Table 3 records the fiberglass geogrid factory price creep test data at different moments corresponding to different strain ratios at 20 °C, and plots the isochronous creep curves according to these experimental data.

It can be seen from Fig. 4 that the grid specimens having the same load value and having a higher load level require a shorter time, while the lower the load level takes a longer time. The curves in the figure are from top to bottom, and the times represented are 1000h, 800h, 600h, 400h, 200h, 100h, 50h, 10h, 1h, 30min. The strain-strain curves corresponding to each moment are gradually increasing as the strain increases with the strain ratio. However, the slopes of the curves corresponding to different moments are not the same. As the creep time increases, the slope of the isochronous creep curve increases. As the creep time increases, the influence of strain ratio on the strain of the fiberglass geogrid for sale becomes more and more. The bigger. To achieve the same magnitude of strain, the lower strain ratio takes longer and the higher strain requires less time.

**3.3 Stress relaxation of geogrid**

During the stress of the fiberglass geogrid manufacturers, when the strain value of the sample remains unchanged, the stress inside the sample gradually becomes smaller with time, and this phenomenon is usually called stress relaxation. Since the indoor relaxation test is difficult to operate and it is not easy to obtain satisfactory test results, the stress ratio-time relationship is used to indirectly reflect the stress relaxation characteristics of the grid test. The strain values of the wholesale fiberglass geogrid at 20 °C were selected to reach the typical strain values of 6%, 7%, 8%, 9%, and 10%. The stress relaxation data of the grid pattern were as shown in Table 4.

Taking the strain ratio as the ordinate and time as the abscissa, the corresponding creep time relationship curve of the high quality fiberglass geogrid sample when a certain strain is generated at different strain ratios is plotted, as shown in Fig. 5.

It can be seen from Fig. 5 that the strain ratio corresponding to the fiberglass geogrid for sale reaches different strains and gradually decreases with time. When the fiberglass geogrid manufacturers are in the stress relaxation state when the strain is kept constant, the load force gradually decreases with time, and the slope of the strain ratio-time curve gradually decreases.

**3.4 Geogrid long-term creep strength and reduction factor**

When the geogrid is applied in practical engineering, it is required to have sufficient strength under long-term stress conditions, and the rheology of the fiberglass geogrid factory price must be considered to ensure the safety of the project. Therefore, when setting the design strength of the fiberglass geogrid manufacturers, it is necessary to reduce the ultimate tensile strength.

In the engineering design, the failure strain of the fiberglass geogrid factory price is generally defined as 10%. Therefore, the data obtained from the creep test can be analyzed, and the load-time relationship curve when the geogrid reaches 10% strain is obtained, and the load time relationship is obtained. The long-term creep strength of the wholesale fiberglass geogrid and the creep reduction coefficient of the fiberglass geogrid factory price are calculated, and the long-term creep law of the fiberglass geogrid for sale is inferred.

Geogrids with different ambient temperatures and different strain ratios at 30 ° C, 40 ° C, and 50 ° C were tested according to the test conditions at 20 ° C. The time corresponding to the creep of 10% under different test conditions is listed in Table 5, and the data in Table 5 is taken as the logarithm of the bottom ten in Table 6. The logarithm of the tenth base for the different strain ratios is shown in Table 7.

Log10 (strain ratio) is the y-axis, Log10 (time required for the elongation to reach 10%) is the x-axis, and the relationship between load and time when the high quality fiberglass geogrid reaches 10% strain at different temperatures according to Tables 5 to 6 is plotted. , see Figure 6 ~ Figure 9.

It can be seen from the trend of the straight line in Fig. 6 to Fig. 9 that the long-term creep strength of the fiberglass geogrid manufacturers exhibits a decaying tendency with time. The higher the temperature, the faster the sample strength drops. The curve correlation coefficients of the test temperature at 20 ° C, 30 ° C, 40 ° C, and 50 ° C were divided into 0.9998, 0.9885, 0.9990, and 0.9977.

Substituting x=6.02 (ie 120 years) and x=5.72 (ie 60 years) into each regression equation, the creep limit strength of the wholesale fiberglass geogrid elongation not exceeding 10% is 35.80kN respectively at 20°C. /m, 36.63kN/m, the stress ratio is 38.92%, 39.82%, and the creep strength reduction factor is 2.57, 2.51. When the temperature is 30 °C, the creep ultimate strength of the fiberglass geogrid manufacturers elongation is less than 10%, which is 28.85kN/m and 29.53kN/m, respectively. The stress ratio is 31.36% and 32.10%, respectively. The creep strength reduction factor is 3.19, 3.11. When the temperature is 40 °C, the creep ultimate strength of the fiberglass geogrid for sale elongation is less than 10%, which is 28.59kN/m and 29.29kN/m, respectively. The stress ratio is 31.08% and 31.84%, respectively. The creep strength reduction factor is 3.22, 3.14.

When the temperature is 50 °C, the creep ultimate strength of the high quality fiberglass geogrid elongation is less than 10%, which is 26.96kN/m and 27.63kN/m, respectively. The stress ratio is 29.30% and 30.03%, respectively. The creep strength reduction factor is 3.41, 3.33.

### 4. Summary

Through the creep test of the high quality fiberglass geogrid, the following conclusions are obtained:

1 Under the condition of low-stress ratio, the fiberglass geogrid factory price strain increases with time, and then the increasing rate gradually becomes slower with time and finally stabilizes. Under high-stress ratio conditions, the strain of the geogrid increases with time until the wholesale fiberglass geogrid breaks.

2 At the same temperature, the greater the stress ratio of the specimen, the greater the strain generated during the same time.

3 To achieve the same magnitude of strain, the lower strain ratio takes longer and the higher strain requires less time.

4 When the fiberglass geogrid manufacturers are in the stress relaxation state, when the strain is kept constant, the load gradually decreases with time.

5 When the temperature is 20 °C, the creep strength reduction coefficient of fiberglass geogrid factory price 120 years and 60 years is 2.57, 2.51; when the temperature is 30 °C, the creep strength reduction coefficient of geogrid 120 years and 60 years is 3.19. , 3.11. When the temperature is 40 °C, the creep strength reduction coefficient of the fiberglass geogrid manufacturers for 120 years and 60 years is 3.22 and 3.14. When the temperature is 50 °C, the creep strength reduction coefficient of the fiberglass geogrid for sale at 120 and 60 years is 3.41 and 3.33.