Centrifuge model study on the performance of fiber reinforced clay-based landfill covers subjected to flexural distress

The influence of discrete and randomly distributed polyester (PET) fibers in improving the crack resistance and water-tightness of clay barriers was studied by conducting a series of centrifuge model tests at 40 gravities using a large beam centrifuge available at Indian Institute of Technology Bombay. Model clay barriers with and without fibers were subjected to flexural distress by inducing differential settlements using a settlement simulator. Two types of clay barriers were prepared by using two different types of soil, namely bentonite amended silty soil (Soil A) and kaolin clay-sand mixture (Soil B). Digital image cross-correlation (DIC) technique was used for analyzing the images captured by a digital photo camera and a charged couple device (CCD) camera, mounted along with the model. Unreinforced soil barriers (URSB) were found to lose their water-tightness and integrity at relatively lower distortion levels compared to identical fiber reinforced soil barriers (FRSB). Also, the performance of URSB and FRSB was found to be superior for Soil A compared to Soil B. The capability of PET fibers on preservation of existing unreinforced soil barriers was also demonstrated. The strain at crack initiation, εc, for FRSB is 2.90 and 2.36 times higher than identical URSB for Soil A and Soil B, respectively. Similarly, the strain at the onset of water breakthrough, εb, for FRSB is 2.14 and 2.79 times higher than identical URSB for Soil A and Soil B, respectively. There is a significant influence of fiber inclusion in retarding the crack initiation and water breakthrough at the onset of flexural distress for both the soil types. Thus, FRSB can withstand more distortion and strain while maintaining the integrity of the clay barrier. This observed behaviour of restraining cracks and improved performance of FRSB is primarily due to the reinforcement effect achieved due to soil-fiber interactions.