Compressibility of biocemented loose sands under constant rate of strain, loading, and pseudo K-triaxial conditions

The compressibility behavior of loose sands treated with Microbially Induced Carbonate Precipitation (MICP) is presented in this paper. The paper discusses the strain rate effects and evolution of at-rest earth pressure coefficient and elastic shear modulus during K0-loading. The soil samples were prepared in a triaxial cell in which a biological solution containing the ureolytic bacteria Sporosarcina pasteurii was injected and held under a small back pressure. Cementation treatments were injected following an alternated top and bottom sequence. The constant rate of strain, constant rate of loading, and pseudo K0-triaxial tests were performed at different strain and stress rates. On-specimen internal instrumentation consisting of a submersible load cell, three Hall Effect transducers, and vertical Bender Elements were used to control radial strains during K0-loading and measure small-strain shear modulus changes. Based on shear wave velocity measurements, the MICP-treated sand was lightly cemented and displayed soil-like behavior. The experimental results demonstrated a significant reduction in soil compressibility after MICP treatment. The material response was remarkably similar for every tested strain rate. The very small values of axial strains measured for the biotreated samples in relation to untreated control specimens for vertical effective stress levels below 200 kPa is evidence of the suitability of this treatment and shows its potential for use in field applications at relatively shallow depths.