Effect of Creep and Temperature Cycling on Tharparkar Sand and Hope Geomembrane Interface Shear Strength

Abstract

In past thirty years, geosynthetic products have been used extensively in civil engineering applications due to their numerous advantages. The most common type of geosynthetics is geomembrane that is used primary as an impervious boundary for liquid and gasses. In district Tharparkar Pakistan where temperature rises to 50 C in summers, different international and national organization are constructing small scale reservoirs using HDPE geomembrane to counter drought affect by harvesting rainwater. The HDPE geomembrane used in construction of landfill and water reservoirs shows viscoelastic behavior to the applied loads and temperature over a period in the form of creep or stress relaxation. Effect of creep, cyclic loading and temperature are critical factors that should be evaluated carefully, because soil geomembrane interfaces usually from weak planes may cause failures. In this study, the 71 direct shear tests were carried out in in the laboratory by subjecting geomembrane samples under different temperature and sustained loading to evaluate the effect of creep, cyclic loading and temperature on Tharparkar sand and HDPE geomembrane. The results showed that the interface friction angle increases up to 5.5 % under sustained loading of 50 KPa for 7 days due to penetration of sand particles into the membrane, resulting in increase of contact surface area. In addition, friction angle decreases with the increase in number of loading and temperature cycles because cycled shearing effected the surface texture i.e., effecting polished surface of smooth HDPE geomembrane. This thesis presents the methods of test performed, results obtained, discussion of the results, findings and recommendation for the future studies.