Effect of Creep on the Design and Construction of Soil Walls Reinforced with Geogrids and Geotextiles

Creep is a phenomenon that occurs in construction materials subjected to constant loads for long periods of time, resulting in deformations that can affect the structural integrity of buildings. In the field of civil engineering, the effect of creep in soil walls reinforced with geogrids and geotextiles is especially relevant and, in particular, is a fundamental aspect in the design and construction of these structures.

Reinforced soil walls are structures that use geogrids and geotextiles to improve the stability and resistance of the soil, being subjected to constant loads throughout the entire service period. These materials can experience creep under the influence of such loads, which can lead to a gradual increase in deformations and ultimately structural failure. The effect of creep in reinforced soil walls geogrids and geotextiles It is a critical factor that must be carefully considered in the design of these structures.

Creep in detail is the deformation of a material under the constant application of a tensile stress. Unlike elastic behavior, deformation does not occur suddenly under the application of tension or stress, but is the result of sustained stress over time. The stages of creep deformation are shown in Figure 1. Here “ε0” is the instantaneous deformation associated with the application of the initial stress. This is followed by primary creep deformation, which is essentially work hardening as the material adjusts to the applied stress. Secondary or steady-state creep is the most important and is the focus of most creep studies. Finally, tertiary creep increases exponentially with stress, usually due to specimen necking, and eventually leads to creep failure.

 

Figure 1. States of deformation due to creep or creep 

 

The geogrids and geotextiles, being polymeric materials, follow these same generalized trends. He creep on geosynthetics for reinforced soil walls It is a function of the polymer used, the production process, the service temperature and the load levels applied. Figure 2 shows data illustrating secondary and tertiary creep behavior at high and low stress levels for different polymers used in geosynthetics.

 

 

TO) Creep to 20% of the ultimate voltage	B) Creep to 60% of the ultimate voltage
Figure 2 – Generalized creep response of various types of polymers (den Hoedt, 1976).

 

 

 

To control this situation, a reduction factor must be applied that limits the tension or stress applied to the geosynthetics to control the level of deformations, thus guaranteeing the safety of the structure. 

In the context of the geogrids of reinforcement, there is an order of magnitude for the creep reduction factor for each type of polymer commonly used as follows:

 

 

 

Geogrids HDPE integral	2.60 to 2.70
Geogrids Woven or knitted PET	1.40 to 1.58
Geogrids of PET bars or strips	1.40 to 1.45

 

 

Taken from GSI White paper #29 Creep Strain Testing of Geosynthetics* 

 

The above values are used to calculate the available resistance Tallow according to Koerner 2012, applying the following equation.

 

Where 

TLTDS = long term design strength 

Tult = strength of the product as manufactured                                                                                                                                                                                                                              https://www.google.com

RFC.R. = creep reduction factor 

RFID = reduction factor due to installation change 

RFED = environmental degradation reduction factor 

 

Finally, it is indicated that a lower value of the creep reduction factor represents a more stable and efficient polymer for soil reinforcement in the construction of retaining walls in reinforced soil, high slope slopes and foundations on soft soils. 

Through proper material selection and careful design considerations, the impact of creep is controlled and the long-term stability and durability of these structures is ensured.