Sediment Outflow under Simulated Rainfall Conditions with Varying Geotechnical Properties

Abstract

The vulnerability of soil toward erosion might be reduced by having a good vegetative cover over the soil surface, slope improvement, and improving soil properties so that it is not easily detached and transported. However, the establishment of proper vegetative cover is a long process because it takes time for seeds to germinate and attain maturity. As an alternative approach, if soil resistance was increased by increasing the shear strength of soil against erosive forces offered by eroding agents, the soil system would become capable of withstanding the detachment of its particles on the application of shear stress. To achieve the desired strength, jute fiber and guar gum were added (0.3%, 0.5%, and 0.7%) to a test plot of 1 m2 area which resulted in three different trays of three different strengths. The strength parameters were determined with the help of a triaxial test where unconsolidated undrained (UU) conditions were maintained throughout the experiment. The tray was maintained at different slopes (4%, 6%, 8%, 10%, and 12%) under a rainfall simulator of 1 m2 area that was capable of producing rainfall intensity of 12.8 and 17.5 cm/h. The sediment outflow for a particular tray at different rainfall intensity and the slope were collected and measured. The recorded observations revealed that the value of the shear strength of soil increased as a result of the applied treatments and the soil loss rate/sediment outflow rate decreased for every combination of land slope and rainfall intensity. In addition, it was found that for a particular value of cohesion and angle of internal friction, the runoff rate increased with rainfall intensity for every land slope and the sediment concentration and sediment outflow rate increased with rainfall intensity as well as land slope. The results of this study will be useful for measuring soil loss, sediment runoff, and sediment discharged from farmland taking into account the properties of rainfall, soil, and flow.