Suitability of sands from different locations at Nsukka as backfill material for vibroflotation

Abstract

Soil stabilization using vibroflotation method requires material backfill for smooth operation of the process and effective densification. Backfill materials fill the voids created by the vibroflot and acceptable backfill is sand with less percentage of fines. This study assesses the suitability of Nsukka sand for backfill purpose in vibroflotation. Samples of Nsukka sand were tested in the laboratory for their physical, mechanical and electro-chemical properties. The suitability numbers (S_N) were determined and a linear regression analysis carried out to correlate the values of S_N with the properties of the sand. Tests results showed that Nsukka sand is “Good” backfill material for vibroflotation with a mean S_N of 15. The samples indicated narrow percentage of fines value of 0.34 - 4.81% and are generally classified as poorly graded sand (SP) with mean fineness modulus of 2.12. They have low salt content with electrical conductivity values between 1090 - 1950μS/cm and mean pH and chloride content values of 6.8 and 98.5ppm respectively. Dry compaction test reveals mean MDD value of 1809kg/m³ for standard Proctor compaction. Linear regression analysis reveals that S_N is dependent on D₁₀ and D₃₀. The efficiency of the model was tested with separate results and the differences between the actual and the predicted S_N were small and acceptable. This study concludes that Nsukka sand is a good material for vibroflotation densification.

Keywords: Backfill Material, Nsukka Sand, Regression Analysis, Suitability Number, Vibroflotation