Engineering benefits of replacing natural sand with manufactured sand in landfill construction
Engineering benefits of replacing natural sand with manufactured sand in landfill construction
Engineering benefits of replacing natural sand with manufactured sand in landfill construction
Translational sliding failures in landfills are often triggered by inadequate shear strength of interfaces in liners and covers. Geosynthetic Clay Liners (GCL) are used in different components of landfills to contain the leachate. GCLs are usually placed above a compacted sand subgrade to develop higher shear resistance. In the context of depleting natural sand resources, the present study explores the feasibility of replacing natural sand with manufactured sand (Msand) in landfill construction. Interface shear tests were performed on GCL in contact with river sand and Msand of similar gradation to evaluate the shear strength at different normal stresses and hydration conditions. It is found that Msand provides higher interface shear strength with GCL compared to river sand. Digital image analysis of tested specimens of GCL showed that variation in particle morphology of the two sands has direct influence on the microlevel interaction mechanisms governing the shear strength. Quantification of morphological parameters showed that Msand particles are angular and rough compared to natural sand particles, leading to higher particle interlocking. Hydration of the GCL reduced the interface shear strength, the effect being less in case of Msand. The study highlights that replacement of natural sand with Msand has added benefits.
Geosynthetic clay liners (GCL) are polymeric geocomposites that are used to contain environmentally harmful elements such as leachates in engineered landfills to prevent them from entering the ground and eventually contaminating the groundwater.
GCLs comprise of bentonite clay in combination with polymeric materials like geomembranes and geotextiles. Bentonite is either adhesively bonded to geomembrane or encapsulated between two geotextiles, which are needle punched or stitch-bonded.
GCLs are ideal replacement for conventional compacted clay liners (CCL) on account of their effective hydraulic properties, self- healing ability, cost effectiveness and easy installation benefits1,2,3. GCLs have several advantages over CCLs in terms of quality assurance, reduced thickness of layers, durability to freeze and thaw, easy accessibility and improved construction speed4,5. GCLs with woven or nonwoven geotextiles are commonly used to form interfaces with other geosynthetics and subgrade material. The placement of GCLs in liners and cover systems is shown in Fig. 1, in which GCLs are in contact with sand layers at various locations. The inhomogeneity in the lining and covers of landfills results in failures under normal stresses and shear stresses imposed by waste dumping and other special conditions like earthquakes. The primary cause of failure in the liners with GCLs is the translational sliding failure due to the insufficient shear strength at the GCL-sand interfaces, the chances being more in case of sloping grounds. Precise evaluation of interface shear strength of GCLs is required to control the sliding and other mechanical instabilities of landfills.
