Evaluation of Stability and Erosion Characteristics of Soil Embankment Slope Reinforced with Different Natural Additives

The top soil layer in an embankment slope is susceptible to erosion, and especially during rainfall it is highly vulnerable, offering the least resistance against erosion and loses strength drastically. The work reported herein summarizes an experimental study on the effects of blending rice husk (RH) and sawdust (SD) in clayey soil in mitigating erosion potential and increasing shear strength parameters of clayey soil used in earthen embankment. For this purpose, several different soil mixes were prepared with either RH or SD. The RH content was increased from 0 to 21% by weight in 3% increments, and SD content was increased from 0 to 7% in 1% increments. Unconfined compression and unconsolidated undrained (UU) triaxial tests were carried out on remolded soil samples mixed with varying RH and SD contents to measure the unconfined compressive strength (UCS) and shear strength parameters (c and ϕ). It was observed that with addition of 15% of RH, the UCS value increased from 121 to 287 kPa, whereas UCS increased from 121 to 407 kPa with 5% addition of SD. The UU triaxial test results revealed that the cohesion of improved soil increased by 2 times and 3 times and its ϕ improved by about 6° and 9° with addition of 15% RH and 5% SD, respectively. Both type of test results suggested that the maximum possible strength increase was achieved by 15% dosage of RH and 5% of SD. Further, soil erosion tests were also carried out using an erosion measuring laboratory setup. These test results also suggested the same dosages of RH and SD in the soil giving the least erosion of the improved soil. The soil erosion rate decreased from 32% in case of untreated soil to about 15% and 12% at optimum content of RH and SD, respectively. Based on this study, the use of SD may be preferred as compared with RH in mitigating soil erosion for its higher erosion resistance and strength characteristics.