**2. Methodology**

This research was based on the stepped isothermal method (SIM) which is standardized by ASTM D6992 [4, 5]. It was modified to prove the long-term deformation of the geocells and to learn the incidence that this property has when calculating the MIF, which is described as the relationship that exists between the module of a granular material confined with geocells and the same granular material without confinement, determined from Eq. (1) [6]. Basically, the adjustment on the test was based in terms of the width and length of the specimens, which depends on the type of geocell that is being analyzed. *MIF* = \_

$$\text{MIIF} = \frac{E\_{\text{reingforward}}}{E\_{\text{no-reingformed}}} \tag{1}$$

**137**

**Table 1.**

method

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

The SIM test determines the long-term deformation of polymers by time-temperature superposition, whose effect was modified for use in polyolefin geocells. This method, known as the "time-temperature superposition principle (PSTT)," establishes that material having a viscoelastic property (V) measured in a time interval coincides with the same measurement in greater times at a lower temperature. Because this method is clearly empirical, it is defined as a principle, because

With the aforementioned considerations, an increase in temperature according to Billmeyer [8], accelerates molecular and segmental movement, leading the system to equilibrium more quickly or "apparent equilibrium," accelerating all

To that extent, the modification proposal is based on systematically dividing the trial into five steps, in which the temperature will be increased with a specific duration for each step. In addition to applying a constant load throughout the trial of 4.4 kN/m, the temperatures reached for each step are 21 ± 1, 44, 51, and 65°C,

The first part of the test refers to the simulation of the load exerted on the geocell at the time of compaction of the filling material. It is possible to find a mean of time-temperature superposition according to [9], a temperature of 51°C and 1 hour of testing, equivalent to 100,000 hours of use (4166 days or

The load of 4.4 kN/m, to which the material is subjected throughout the test, replicates the force supported by the geocell in the granular subbase of a pavement structure. This necessitates implementation of a series of charges which will be

**Properties of the material Testing method Unit Values MARV** Polymer density ASTM D-1505 g/cm3 0.935–0.965

**Physical properties Testing method Unit Typical values** Nominal size of the expanded cell Measured mm 320 × 287 Nominal area of the expanded cell Measured cm2 460 Nominal size of the expanded panel Measured m 2,56 × 8,35 Nominal size of the expanded panel Measured m2 21,04

Resistance of the joints by ultrasound USAGE GL-86-19 N 1065 1420 2130 2840

% of perforations per unit area Measured % 12±2

method B

weight

ASTM D-5199 mm 1.1 ± 10%

ASTM D-5199 mm 1.52 ± 10%

(in)

ISO 10319 kN/m 25

kN/m 15

1.5% min

75(3) 100(4) 150(6) 200(8)

imposed through weights that will transmit this force to the geocells.

Black smoke content ASTM D-1603 %

Height of the cell Measured mm

Ultimate resistance to joints tension ISO 13426-1

Nominal thickness of the cell wall before

Nominal thickness of the cell wall after

Ultimate resistance to tension wide strip

*Properties of geocell type 1, Provider 1.*

not even theoretical concepts have been developed to sustain it [7].

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

viscoelastic processes.

respectively.

11 years).

texturing

texturing

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

The SIM test determines the long-term deformation of polymers by time-temperature superposition, whose effect was modified for use in polyolefin geocells. This method, known as the "time-temperature superposition principle (PSTT)," establishes that material having a viscoelastic property (V) measured in a time interval coincides with the same measurement in greater times at a lower temperature. Because this method is clearly empirical, it is defined as a principle, because not even theoretical concepts have been developed to sustain it [7].

With the aforementioned considerations, an increase in temperature according to Billmeyer [8], accelerates molecular and segmental movement, leading the system to equilibrium more quickly or "apparent equilibrium," accelerating all viscoelastic processes.

To that extent, the modification proposal is based on systematically dividing the trial into five steps, in which the temperature will be increased with a specific duration for each step. In addition to applying a constant load throughout the trial of 4.4 kN/m, the temperatures reached for each step are 21 ± 1, 44, 51, and 65°C, respectively.

The first part of the test refers to the simulation of the load exerted on the geocell at the time of compaction of the filling material. It is possible to find a mean of time-temperature superposition according to [9], a temperature of 51°C and 1 hour of testing, equivalent to 100,000 hours of use (4166 days or 11 years).

The load of 4.4 kN/m, to which the material is subjected throughout the test, replicates the force supported by the geocell in the granular subbase of a pavement structure. This necessitates implementation of a series of charges which will be imposed through weights that will transmit this force to the geocells.


#### **Table 1.**

*Properties of geocell type 1, Provider 1.*

*Geopolymers and Other Geosynthetics*

soils and under humid conditions.

during the design of the structure.

each one of them.

**2. Methodology**

geocells.

for use in various military applications [1]."

deconfinement in the geocell filling material [2, 3].

develop the cellular confinement system in the late 1970s, as a means to help build roads, runways, platforms, and others; all these solutions were made on very soft

The main large-scale use of this system of cellular confinement was during the Gulf War, in "Operation Desert Storm", where it transported heavy military material with speed and efficiency. For the purpose of mobilizing large troops, according to the company Geoceldas SA, the defense department of the United States "acquired 6.4 million square feet (600,000 square meters) of cellular geosynthetics

In terms of its implementation in design tasks, pavement structure with geocells uses a coefficient of increase for the modules of the materials (MIF), which depends on several factors. Among these is resistance to long-term deformation of the material that makes up the panel of geocells. This generates a mechanism of confinement, which creates an apparent cohesion of the material incorporated therein. If the geocells yield, it is susceptible to losing its properties and begins to deform causing a settlement in the pavement structure, in addition to providing a

Therefore, some consequences of deformation in the geocell are the reduction of the apparent cohesion in the filling material due to the loss of confinement, according to which there is a high decrease in the MIF coefficient taken into account

For these reasons, it is important to know the properties of the materials that are involved in the pavement structures and the veracity of the calculations that are made in the analyses. Therefore, when calculating the MIF, it is important to know the long-term deformation of material to give support and certainty in the analyses. Consequently, a modified test based on the SIM for geocells was developed. A test program was carried out using different samples of geocells, exposing results for

The definition of the MIF factor refers to the material modulus with reinforcement vs. the material without reinforcement. This value is obtained at the moment of designing a structure with geocell, applying five characteristics of the materialgeocell set, among which is the long-term deformation of geosynthetic. The MIF value depends on the analysis of the creep in the geocells, because if the material becomes deconfined, the increase of the modulus considered in the design will be reduced. For this reason, a safety factor is applied to the MIF, due to the creep in the

The samples were analyzed under load effects, which contemplate those generated at the level of the granular subbase layer of pavement, thus showing the feasibility of use in this layer and the possible behavior of these over its usable life.

This research was based on the stepped isothermal method (SIM) which is standardized by ASTM D6992 [4, 5]. It was modified to prove the long-term deformation of the geocells and to learn the incidence that this property has when calculating the MIF, which is described as the relationship that exists between the module of a granular material confined with geocells and the same granular material without confinement, determined from Eq. (1) [6]. Basically, the adjustment on the test was based in terms of the width and length of the specimens, which

> *Ereinforced Eno*<sup>−</sup>*reinforced*

(1)

depends on the type of geocell that is being analyzed. *MIF* = \_

**136**


#### **Table 2.**

*Properties of geocell type 2, Provider 2*


**139**

**2.1 Sampling**

*Geocell of types 3 and 4 properties, Provider 3.*

**Table 3.**

polymer composition.

are shown in **Table 2**.

shown in **Table 1**.

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

ASTM D-3895 ≥125

ASTM D-5885 ≥1250

ASTM D-5321 ≥0.84

Cells, joints, and perforations remained intact without evidence of plastic deformation at the end of the cyclic loading

All samples used came from polyolefin geocells available in the Colombian market. The sampling was conducted randomly from a bank of specimens supplied by the manufacturer. For the high-density polyethylene (HDPE) geocells, its polymer contents are not mentioned in this document, since it is known as high-density polyethylene in all the state of the art. While for the Neoloy® Geocell, no typology is obtained since its raw material is patented and there is no information about its

For the first type of HDPE polyolefin geocells from Provider 1, the properties are

For the second type of HDPE polyolefin geocells from Provider 2, the properties

For the third type of polyolefin geocell from Neoloy® of Provider 3, the proper-

ties shown in **Table 3** are available, for categories A, C, and D.

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

**Property Value**

Accelerated radial pressure test (TRI)

ISO 672 ASTM E2254 (DAM) −40°C >1150 −10°C >1050 +10°C >950 +30°C >750 +45°C >650 +60°C >550

ASTM D-6992 (SIM)

5 years <1.2 10 years <1.4 25 years <1.9 50 years <2.9

**Dimensions of the cells and panels**

Time of induction to oxidation (OIT at 200°C) (mpn.) (virgin material before any modification)

Resistance to ultraviolet degradation (HPOIT at 200°C) (min.)

Durability of the cell to longterm cyclical loads (pass)

Efficiency of the internal

Flexural module for each temperature (MPa)

friction angle

Reduction factor due to permanent deformation(creep) *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 3.**

*Geopolymers and Other Geosynthetics*

Resistance to environmental cracking

(ESCR)

**Dimensions of the cells and panels**

*Properties of geocell type 2, Provider 2*

**Table 2.**

**Categories of the geocell**

Ultimate resistance of the material (MPa)

Ultimate resistance (wide strip with perforations)

Coefficient of thermal expansion (ppm/°C) measuring range of −30°C to +30°C

**Property Value** Distance between ribs 445 mm (±2.5%) Height of the cells 150–200 mm (±5%) Dimensions of the open cell 340 × 290 mm (±3%)

Minimum values of resistance ISO 13426-1 method A:
