Assesment of effect of polypropylylene fiber in shear modulus an‎d damping ratio of Chabahar carbonated san‎d

11/25/2026 12:00:00 AM

Given the extensive presence of carbonate soils in vital an‎d strategic regions of the Earth an‎d in Iran where the coastal belt soils of the Persian Gulf an‎d the Makran Sea are primarily composed of carbonate materials; there is an urgent need in these areas, especially in Chabahar, the only oceanic port considered a strategic defensive an‎d economic zone for the country, to construct refineries, oil platforms, ports, defense industries, an‎d more. In addition to the general weaknesses of carbonate soils, such as particle crushability, Chabahar carbonate san‎d falls into the category of poorly graded san‎d an‎d, if the particles are not cemented, will exhibit significant weakness against liquefaction. Therefore, under certain conditions, reliance on the mechanical properties of the soil alone is insufficient, an‎d soil improvement becomes necessary. Using polypropylene fibers in soil, which falls under the category of geosynthetics, is a simple, cost-effective, an‎d environmentally friendly method. This approach introduces tensile strength an‎d improves the soilʹs resistance to liquefaction an‎d its static strength. By incorporating polypropylene fibers into Chabahar carbonate san‎d, the shear modulus an‎d damping ratio of the soil; two crucial parameters in dynamic soil analysis can be altered. Consequently, due to the non-linear behavior of soil, the extent an‎d manner of changes in the shear modulus an‎d damping ratio of Chabahar carbonate san‎d must be investigated across a range of small to large strains. In this research, two sets of experiments were conducted: resonant column tests an‎d straincontrolled cyclic triaxial tests. These were performed at relative densities of 15%, 30%, an‎d 55%; effective confining pressures of 50, 100, an‎d 200 kPa; consolidation stress ratios of 1, 2, an‎d 3; loading frequencies of 0.1, 0.2, an‎d 0.5 Hz; an‎d polypropylene fiber contents of 0%, 0.5%, 1%, 1.5%, an‎d 2% by weight. According to the results, it was determined that the loading frequency within this range (0.1 to 0.5 Hz) does not significantly affect the shear modulus an‎d damping ratio of Chabahar carbonate san‎d. With an increase in the consolidation stress ratio, the shear modulus an‎d damping ratio of Chabahar carbonate san‎d increase. As the percentage of polypropylene fibers in the sample increases, the shear modulus decreases at smaller strains an‎d increases at larger strains. Furthermore, the effect of fiber presence is much more pronounced at small strains compared to medium an‎d large strains. At a relative density of 15%, increasing the fiber content from 0% to 2% leads to an increase in the damping ratio of the samples. When the relative density is increased to 30%, adding polypropylene fibers up to a certain percentage (approximately 1%) causes an increase in the damping ratio of the samples. Adding fibers from 1% to 2% results in a decrease in the damping ratio. Under semi-compact conditions, adding polypropylene fibers up to a certain percentage (approximately 0.5%) increases the damping ratio of the samples. Adding fibers from 0.5% to 2% reduces the damping ratio, to the extent that the damping ratio of the samples becomes even lower than that of unreinforced samples. At small strains, the presence of fibers at any percentage does not affect the damping ratio of the samples, an‎d the primary influence of fibers on the damping ratio is observed at medium an‎d large strains. Key words: Chabahar carbonated san‎d, cyclic triaxial apparatus, resonant column apparatus, shear modulus, damping ratio, polypropylene fiber

دستگاه سه محوري سيكليك , دستگاه ستون تشديد , مدول برشي , نسبت ميرايي , الياف پلي پروپيلن

cyclic triaxial apparatus , resonant column apparatus , shear modulus , damping ratio , polypropylene fiber

Hamidreza Janshekar

Dr. Aliakbar Heshmati Rafsanjani _ Dr.Hossein Salehzade