Laboratory investigation and field evaluation of loess improvement using nanoclay - A sustainable material for construction

摘要

Loess soils are aeolian deposits of primarily silt sized soil particles, which are often lightly cemented. The wind-blown depositional process of loess formation yields a relatively loose soil structure that is particularly sensitive to changes in hydro-mechanical loading conditions, and the silt particles that comprise loess deposits are often easily eroded by water or wind. The main irrigation channels of Gonbad dam, located in northeastern Iran, are constructed on loess deposits and have experienced significant cracking and other forms of damage that can be attributed to subsidence and erosion of the loess soil. This study investigates the potential for effective loess stabilization using nanoclay, an engineered nanomaterial, both in the laboratory and in the field at the Gonbad dam irrigation channel site. To evaluate the effects of nanoclay stabilization, varying fractions of nanoclay ranging from 0.2% to 3% by mass were added to the natural loess soil. In the laboratory, representative specimens were prepared and subjected to a variety of tests, including Atterberg limits, standard Proctor compaction, unconfined compressive strength, unconsolidated undrained triaxial compression, wetting-induced collapse, and pinhole dispersivity. Results from the laboratory tests revealed that the addition of nanoclay altered the plasticity, strength, and stiffness behavior of the specimens. Also, the dispersivity and relative wetting-induced collapse behavior of the natural loess were impacted by the addition of nanoclay. In-situ investigation was performed at a selected section of the irrigation channel, to explore the effectiveness of nanoclay for improving the loess soil. Results of this pilot field study indicated that loess soils that had been stabilized with 2% nanoclay showed notable improvement. The field and laboratory obtained results were observed to be in general agreement. (C) 2017 Elsevier Ltd. All rights reserved.