COMPARISON IN THE EROSION RATE OF STABILIZED SILTY SAND SOILS WITH CEMENT AND NANOCLAY

Internal erosion and scouring have always created many problems for earth dams. Since half of the world's earth dams damages result from internal erosion, this process has been recognized as the second reason for the fracture of these dams and has raised major concerns. Although there have been many proven methods to control this phenomenon for over 50 years, this problem has not yet been completely resolved. It includes different processes such as piping and suffusion. The study of these phenomena is an important topic in many different fields such as hydraulic and geotechnical engineering. One of the ways to alleviate this phenomenon is soil remediation, which requires adding different percentages of additives to the soil. Since these additives may damage the environment or cost a lot, we need to find optimum quantities that reduce cost and environmental problems. In this study two additive substances like cement and nanoclay were added to the soil and according to research, cement and nanoclay were not environmentally and economically suitable in large volumes, respectively. In the present study, low percentages of these materials were used and the Hole Erosion Test (HET) was run to control the phenomenon of internal erosion. Given that the soil used in this study was silty sand, we added 0.25, 0.5, 1, 2, and 3 percent cement and 0.5, 1 and 1.5 percent nanoclay to the soil and after passing the curing time (1, 7, 14, and 28 days), the soil was compressed by the compression hammer and tested. According to the results after 28 days, the erosion rate index increased more than threefold in 1.5% nanoclay and 1% cement compared to the control soil, which changed the soil group from relatively fast to very slow and leads to the reduction of erodibility. Moreover, at all the percentages and intervals, critical shear stress of soil samples with cement was higher than that of nanoclay.