Characterization and finite element analysis of lime and polymer treated ultra-soft clay soils using the electrical resistivity and miniature penetrometer methods

Abstract

The characterization of ultra-soft soil behavior is one of the most difficult challenges since the water content in such soils is very high. Hence, nondestructive or special measurement is required. Therefore, the behavior of untreated and treated ultra-soft soil was characterized using both miniature penetrometer and electrical methods. The ultra-soft soil was prepared with 2 % to 10 % bentonite. The soil with 10 % bentonite was treated with 2 % to 10 % lime and with 1 % to 10 % polymer separately. The pH, CIGMAT miniature penetrometer, and electrical resistivity combined with the measured shear strength from the modified vane shear device were used to characterize the ultra-soft soils. The CIGMAT miniature penetrometer penetration varied linearly with the shear strength of the untreated and treated soft soils with 10 % bentonite. Relative electrical resistivity decreased by 246 % when the bentonite content was increased from 2 % to 10 % in the ultra-soft soil. The addition of 10 % of the lime to the ultra-soft soil with 10 % of bentonite content decreased the relative electrical resistivity by 171 %. The addition of 10 % of the polymer to the ultra-soft soil with 10 % of bentonite content reduced the relative electrical resistivity by 545 %. Power law, linear and hyperbolic models were used to predict the shear strength-electrical resistivity relationship for the untreated, lime-treated and polymer-treated ultra-soft soils respectively. The CIGMAT miniature penetrometer was modeled using 3-D axisymmetric finite element method, which predicted the penetration of CIGMAT penetrometer that agreed well with the experimental results of the ultra-soft soils.