Utilization of water turbidity meter devices in estimating the aggregate stability of artificially stabilized soils

Abstract

This study is designed to utilize portable turbidity meters, usually available in most water analysis laboratories, in developing of a quick Dispersion Ratio test (DR, %) as an index of soil stability. The work includes: first, the use of different stabilizers (Bitumen, Lime and Cement) in the preparation of artificially stabilized lead contaminated soils; second, the measurements of scouring depth (SD, in mm), critical shear stress (τc, pa) and erodibility coefficient (kd, cm3/kN.s) by using a "Mini" Jet Erosion Test; and finally, the comparison between dispersion ratio (DR, %) values of soils, as estimated by the portable turbidity meter and by the gravimetric method. The results showed that all stabilizers can markedly improve the stability of soil; either as (SD, τc, and kd) or as (DR, %) and cement was the best stabilizer. In general, good correlations were found between the turbidity (NTU) and suspended solids (mg/l) of the stabilized soils; (R= 0.99, 0.96 and 0.97) for bitumen, lime and cement respectively. The turbidity DR (%) appears to have a higher correlation with both lime (R= -0.98) and bitumen (R= -0.96) and in a lesser extent with cement (R= -0.87); because only 3% cement could sharply reduce DR(%) of the untreated soil from 7.03 to 2.54%, compared with 4.9 and 4.25% for lime and bitumen respectively. Moreover, the turbidity DR (%) seems to be highly correlated with the kd of soils (R= 0.99, 0.96 and 0.90 for cement, bitumen and lime, respectively) and cement was the best in the reduction of both kd and DR (%) even at 3%. It could be concluded that the turbidity DR (%) can be easily utilized to be as a successful index of soil stability. The turbidity method is quick, easy and cost effective and of results that are highly correlated with other erodibility parameters and this may suggest and recommend the use of the turbidity devices in estimating the stability of artificially stabilized soils and other similar soils.