Geosynthetics application and soil reinforcement
Geosynthetics are being widely used as a cost-effective soil reinforcement solution. The use of geogrids to improve soil mechanical behavior has become increasingly common practice in geotechnical engineering applications, as it has unique advantages over other soil improvement techniques due to technical, economical, constructability, and sustainability aspects. Mechanical properties of geogrids are of great importance in designing with geogrids. This paper discusses the effect of strain rate of loading on the tensile strength pf polyester (PET) geogrids. This paper presents the results and analysis of laboratory constant strain rate (CSR) test conducted on polyester (PET) geogrids at strain rates varying from 0.10% to 20% strain per minute. Assessment of variation of geogrid stiffness with time (creep effect) and calibration factor between global to local strains was derived. Proper material characterization of geogrid is essential for numerical finite element modeling. The modeled behavior of reinforced structures is sensitive to the geogrid stiffness rather than the geogrid strength. The higher CSR results in an increase in the measured strength and secant modulus. The larger the ultimate strength, the higher the anticipated secant modulus. The calibration factor CF between global to local strains ranged from 2.08 to 1.99 was measured for the tested polyester geogrid specimens at a stain of 2%. This CF estimation for a strain of 2% is in agreement with comparable PET geogrid CF of 2.2, which was introduced by Allen et al. (2002).
This paper is a portion of wide-ranging research to better identify the behavior and material characterization of Geosynthetics reinforced structures using polyester (PET) geogrid. Constant Strain Rate CSR tests were carried out for the used PET geogrids at MD in accordance with ASTM D6637 using “the multi-rib geogrid test” to justify tensile ultimate strength, and Strain at the break; results are in good agreement with manufacturers' technical datasheet. Values for Secant modulus J at strain level 1% & 2% were derived from the tensile force- strain relationship results, which are necessary numerical FE molding. The influence of strain loading rate was assessed on the strength and stiffness of the different polyester specimens. We are focused on simulations that can be used to predict operational (working stress) under static conditions rather than incipient collapse. The main findings might be summarized as follows:
· The higher CSR reveals an increase of the measured secant modulus. The larger the ultimate strength, the higher the anticipated secant modulus.
· Calibration Factor CF between global to local strains ranged from 2.08 to 1.99 was introduced appropriately for the tested polyester geogrid specimens at the stain domain of 2%. This CF estimation for strain levels of 2% or less- based on the CSR test- is in worthy agreement with comparable PET geogrid CF of 2.2, which was introduced by Allen et al. (2002).
· To assess the long-term parameter and creep effect, a series of CRS tests were conducted for different strain rates of 20%, 10%/ min, 6% /min, 3%/min, 1%/min, and 0.05%/min. Outcome response is in good agreement with a consensus that for polyester (PET) geogrid, time-dependent stiffness reductions will be minimal (approximately 25-15% or less).
· The linear approximation of secant modulus (after creep consideration) is considerably accepted in the strain domain up to 2% which covers a wide scatter of Geosynthetics reinforced structures conditions under service loadings.