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Geomechanics and Engineering
  Volume 22, Number 3, August10 2020, pages 227-236
DOI: https://doi.org/10.12989/gae.2020.22.3.227
 


Engineering properties of expansive soil treated with polypropylene fibers
Muhammad Ali, Mubashir Aziz, Muhammad Hamza and Muhammad Faizan Madni

 
Abstract
    Expansive soils are renowned for their swelling-shrinkage property and these volumetric changes resultantly cause huge damage to civil infrastructures. Likewise, subgrades consisting of expansive soils instigate serviceability failures in pavements across various regions of Pakistan and worldwide. This study presents the use of polypropylene fibers to improve the engineering properties of a local swelling soil. The moisture-density relationship, unconfined compressive strength (UCS) and elastic modulus (E50), California bearing ratio (CBR) and one-dimensional consolidation behavior of the soil treated with 0, 0.2, 0.4, 0.6 and 0.8% fibers have been investigated in this study. It is found that the maximum dry density of reinforced soil slightly decreased by 2.8% due to replacement of heavier soil particles by light-weight fibers and the optimum moisture content remained almost unaffected due to non-absorbent nature of the fibers. A significant improvement has been observed in UCS (an increase of 279%), E50 (an increase of 113.6%) and CBR value (an increase of 94.4% under unsoaked and an increase of 55.6% under soaked conditions) of the soil reinforced with 0.4% fibers, thereby providing a better quality subgrade for the construction of pavements on such soils. Free swell and swell pressure of the soil also significantly reduced (94.4% and 87.9%, respectively) with the addition of 0.8% fibers and eventually converting the medium swelling soil to a low swelling class. Similarly, the compression and rebound indices also reduced by 69.9% and 88%, respectively with fiber inclusion of 0.8%. From the experimental evaluations, it emerges that polypropylene fiber has great potential as a low cost and sustainable stabilizing material for widespread swelling soils.
 
Key Words
    swelling soils; polypropylene fiber; soil improvement; unconfined compressive strength; California bearing ratio; free swell; swell pressure; compressibility
 
Address
Muhammad Ali and Muhammad Hamza: Department of Technology, The University of Lahore, Lahore, Pakistan

Mubashir Aziz: Department of Civil Engineering, National University of Computer and Emerging Sciences, Lahore, Pakistan

Muhammad Faizan Madni: Department of Civil Engineering, The University of Lahore, Lahore, Pakistan
 

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