**3. Procedure of the test**

The laboratory procedure is divided into three parts.

Part I: To start the test, it is necessary to take the measurements of the samples; for this reason the length, width, and thickness of the geocell must be taken.

Part II: The specimen is adjusted to the metal jaws, generating a total interaction between the geocell and the jaws (**Figure 1**), while **Figure 2** shows how the jaws should be placed on both the upper and lower halves to generate the desired load transfer.

**Figure 1.** *Adjustment of the sample to the clamp.*

**Figure 2.** *Placement of the sample to the upper and lower jaws.*

**141**

(**Figure 4**, left).

**Figure 4.**

**4. Results**

oven is subsequently closed.

exposed throughout the trial.

The following equation is the result:

*Analysis of the Creep and the Influence on the Modulus Improvement Factor (MIF) in Polyolefin...*

Part III: In this step, the samples are hoisted in the oven support, complementing the union of the jaw of the lower part of the sample to the stem (**Figure 3**). After this it is necessary to place the deformimeters in the base that supports the oven

*Deformimeters in the base of the oven (left) and placement of weights in the stems (right).*

Part IV: The hydraulic jack is placed in the lower part of the rods, generating a support so as not to exert preliminary efforts on the geocells, and then all the necessary weights are placed to reach the force required in the test (**Figure 4**, right). The

Part V: The oven is turned on at room temperature (21 ± 1°C), then the hydraulic jack is lowered by hanging the stems with the weights, and the first reading of the deformimeter is recorded, after which the steps with the pre-established times begun.

To obtain the time-temperature superposition data that is necessary in the production of the SIM assay graphs, it was necessary to create an accurate graph, where equivalences (see **Table 4**) are determined between temperature and time

An exponential behavior is observed in these correlations, where time depends on temperature (**Figure 5**). For this reason, an exponential regression shown on the same graph is generated, in order to determine the total time that the geocell was

*T* = 0.0005 ∗ *e*0,3289∗*t*° (2)

superimposed by every minute that elapsed in temperature; see [10].

*DOI: http://dx.doi.org/10.5772/intechopen.88518*

**Figure 3.** *Installation of the sample in the oven.*

*Analysis of the Creep and the Influence on the Modulus Improvement Factor (MIF) in Polyolefin... DOI: http://dx.doi.org/10.5772/intechopen.88518*

**Figure 4.** *Deformimeters in the base of the oven (left) and placement of weights in the stems (right).*

Part III: In this step, the samples are hoisted in the oven support, complementing the union of the jaw of the lower part of the sample to the stem (**Figure 3**). After this it is necessary to place the deformimeters in the base that supports the oven (**Figure 4**, left).

Part IV: The hydraulic jack is placed in the lower part of the rods, generating a support so as not to exert preliminary efforts on the geocells, and then all the necessary weights are placed to reach the force required in the test (**Figure 4**, right). The oven is subsequently closed.

Part V: The oven is turned on at room temperature (21 ± 1°C), then the hydraulic jack is lowered by hanging the stems with the weights, and the first reading of the deformimeter is recorded, after which the steps with the pre-established times begun.

### **4. Results**

*Geopolymers and Other Geosynthetics*

The laboratory procedure is divided into three parts.

Part I: To start the test, it is necessary to take the measurements of the samples;

Part II: The specimen is adjusted to the metal jaws, generating a total interaction between the geocell and the jaws (**Figure 1**), while **Figure 2** shows how the jaws should be placed on both the upper and lower halves to generate the desired load transfer.

for this reason the length, width, and thickness of the geocell must be taken.

**3. Procedure of the test**

**Figure 1.**

**Figure 2.**

*Adjustment of the sample to the clamp.*

*Placement of the sample to the upper and lower jaws.*

**140**

**Figure 3.**

*Installation of the sample in the oven.*

To obtain the time-temperature superposition data that is necessary in the production of the SIM assay graphs, it was necessary to create an accurate graph, where equivalences (see **Table 4**) are determined between temperature and time superimposed by every minute that elapsed in temperature; see [10].

An exponential behavior is observed in these correlations, where time depends on temperature (**Figure 5**). For this reason, an exponential regression shown on the same graph is generated, in order to determine the total time that the geocell was exposed throughout the trial.

The following equation is the result:

$$T = 0.00005 \* e^{0.3289 \* t^\*} \tag{2}$$


### **Table 4.**

*Equivalent times.*

**Figure 5.** *Time-temperature superposition.*

in which.

*T*: equivalent time in minutes per minute elapsed in temperature *t*°.

*t*°: temperature (°C).

The data for the time equivalent to the temperature were obtained based on the above equation, during the course of the different isothermal steps of the test. These equivalent times are shown in **Table 5**.

After the development of the different graphs made from the tests, it was possible to subtract and make a comparison between the materials that were used in each of the tests, in order to determine which behaved better in the long-term deformation. **Figure 6** shows the comparative graph of materials. A red line is again observed, which indicates 3% of the deformation, which generates a fault in the ground and the possible breakage of the pavement structure.

For the comparative graph of materials, the samples that had been exposed for a while were not considered, given that the other materials did not have this previous exposure and therefore leading to a possible erroneous comparison.

It is important to consider the effect that occurs in the geocells of Neoloy® from exposure to the environment (**Figure 7**), since these demonstrate the best behavior against long-term deformation [11–15].

Based on the previous results, it is important to make a new comparison in the Neoloy® Geocells, for its ultimate resistance to the wide strip test ISO 103192.

**143**

**Figure 6.**

*Comparison of samples tested.*

*Analysis of the Creep and the Influence on the Modulus Improvement Factor (MIF) in Polyolefin...*

**Step Time (min.) Accumulation of time (years)**

30 2.96E−05 60 5.91E−05 90 8.87E−05

167 0.33

167 3.63

167 36.72

122 310.89

Ambient 0 0

44°C 30 8.94E−03

51°C 30 0.46

58°C 15 4.94

65 °C 60 78.78

**Figure 8** shows the incidence of this property in the behavior to the long-term

Continuing with the analysis of the behavior of the polyolefin geocells in long-term deformation, a different behavior was observed among the materials of the HDPE samples, where the thickness determined in part the behavior that was observed throughout the tests. Because of this, the evolution of the specimens in

deformation and the affectation on the MIF.

*DOI: http://dx.doi.org/10.5772/intechopen.88518*

Increase to 44°C

Increase to 51°C

Increase to 58°C

Increase to 65°C

*Equivalent times for the SIM test.*

**Table 5.**

*Analysis of the Creep and the Influence on the Modulus Improvement Factor (MIF) in Polyolefin... DOI: http://dx.doi.org/10.5772/intechopen.88518*


#### **Table 5.**

*Geopolymers and Other Geosynthetics*

**142**

in which.

**Figure 5.**

**Table 4.** *Equivalent times.*

*t*°: temperature (°C).

*Time-temperature superposition.*

These equivalent times are shown in **Table 5**.

against long-term deformation [11–15].

ground and the possible breakage of the pavement structure.

exposure and therefore leading to a possible erroneous comparison.

*T*: equivalent time in minutes per minute elapsed in temperature *t*°.

**Temperature (°C) Equivalent time (min.)**

23 1 30 10 37 100 44 1000 51 10,000 58 100,000 65 1,000,000

The data for the time equivalent to the temperature were obtained based on the above equation, during the course of the different isothermal steps of the test.

After the development of the different graphs made from the tests, it was possible to subtract and make a comparison between the materials that were used in each of the tests, in order to determine which behaved better in the long-term deformation. **Figure 6** shows the comparative graph of materials. A red line is again observed, which indicates 3% of the deformation, which generates a fault in the

For the comparative graph of materials, the samples that had been exposed for a while were not considered, given that the other materials did not have this previous

It is important to consider the effect that occurs in the geocells of Neoloy® from exposure to the environment (**Figure 7**), since these demonstrate the best behavior

Based on the previous results, it is important to make a new comparison in the Neoloy® Geocells, for its ultimate resistance to the wide strip test ISO 103192.

*Equivalent times for the SIM test.*

**Figure 6.** *Comparison of samples tested.*

**Figure 8** shows the incidence of this property in the behavior to the long-term deformation and the affectation on the MIF.

Continuing with the analysis of the behavior of the polyolefin geocells in long-term deformation, a different behavior was observed among the materials of the HDPE samples, where the thickness determined in part the behavior that was observed throughout the tests. Because of this, the evolution of the specimens in

**Figure 7.** *Behavior according to environmental exposure time (Neoloy®).*

#### **Figure 8.**

*Behavior of Neoloy® geocells according to resistance of wide strip ISO 103192.*

terms of thickness is shown in **Figure 9**, revealing that the material with greater thickness presents a better response to this type of long-term stress.

As it is possible to extract from the different graphs in categories C and D composed of Neoloy® from Provider 3, an acceptable behavior was observed against the long-term deformation, this being the material that behaved better during the trials without reaching the 3% deformation failure in any of the two categories mentioned. Therefore, the geocells would have an MIF factor of high incidence in the module of the material to be confined, as shown in the Mohr circle (see **Figure 10**).

According to Han [16], the confinement creates an apparent cohesion considering the modification in the normal stresses caused to the granular material. This is

**145**

**Figure 9.**

**Figure 10.**

*Behavior HDPE geocells according to thickness.*

*Analysis of the Creep and the Influence on the Modulus Improvement Factor (MIF) in Polyolefin...*

only available if the material of the geocell resists the deformations produced by the stresses over the life of the project. Only the Neoloy® Geocells of categories C and

When comparing the categories of the Neoloy® material, the great importance of both the thickness of the material and the resistance to the wide strip is observed. The results show better behavior in the geocell that has a greater resistance and greater thickness, displaying a high creep behavior and consequently increasing the MIF, which is significant when designing structures with this geocell methodology. However, at the end of the tests, a rational time was determined to discharge the geocells. At this time an important behavior was observed in which the samples began to regenerate, decreasing the deformations that were at the end. The effect was established for the geocells that did not fail, showing an "elastic" behavior but

D of Provider 3 manage to comply with the limitation of the MIFs.

*Mohr circle of granular material with and without reinforcement [7].*

*DOI: http://dx.doi.org/10.5772/intechopen.88518*

*Analysis of the Creep and the Influence on the Modulus Improvement Factor (MIF) in Polyolefin... DOI: http://dx.doi.org/10.5772/intechopen.88518*

**Figure 9.** *Behavior HDPE geocells according to thickness.*

*Geopolymers and Other Geosynthetics*

**144**

**Figure 8.**

**Figure 7.**

*Behavior according to environmental exposure time (Neoloy®).*

terms of thickness is shown in **Figure 9**, revealing that the material with greater

As it is possible to extract from the different graphs in categories C and D composed of Neoloy® from Provider 3, an acceptable behavior was observed against the long-term deformation, this being the material that behaved better during the trials without reaching the 3% deformation failure in any of the two categories mentioned. Therefore, the geocells would have an MIF factor of high incidence in the module of the material to be confined, as shown in the Mohr circle (see **Figure 10**). According to Han [16], the confinement creates an apparent cohesion considering the modification in the normal stresses caused to the granular material. This is

thickness presents a better response to this type of long-term stress.

*Behavior of Neoloy® geocells according to resistance of wide strip ISO 103192.*

**Figure 10.** *Mohr circle of granular material with and without reinforcement [7].*

only available if the material of the geocell resists the deformations produced by the stresses over the life of the project. Only the Neoloy® Geocells of categories C and D of Provider 3 manage to comply with the limitation of the MIFs.

When comparing the categories of the Neoloy® material, the great importance of both the thickness of the material and the resistance to the wide strip is observed. The results show better behavior in the geocell that has a greater resistance and greater thickness, displaying a high creep behavior and consequently increasing the MIF, which is significant when designing structures with this geocell methodology.

However, at the end of the tests, a rational time was determined to discharge the geocells. At this time an important behavior was observed in which the samples began to regenerate, decreasing the deformations that were at the end. The effect was established for the geocells that did not fail, showing an "elastic" behavior but

also maintaining a degree of plastic deformation. Therefore, a linear viscoelastic behavior can be determined, in which there is an initial elastic deformation caused by the stresses generated upon it, followed by a time-dependent delayed deformation, known as material creep. There may be some permanent flow in the material, especially when high loads are applied.

When the unload is permitted to the material, within linear viscoelastic behavior, an inverse process begins, with a certain recovery at the moment, continued by a recovery along the time recovering fluence dependent on the time. The material may or may not reach the original dimensions. If permanent flow occurs in the charging process, there will be a residual deformation even when the load application is no longer allowed [17–19].
