Interface Shear Behavior between MICP-Treated Calcareous Sand and Steel

Abstract

Microbial-induced carbonate precipitation (MICP) is an innovative ground improvement technique that utilizes bacteria to induce calcium carbonate precipitation to cement soil particles. In this paper, the interface strength between calcareous sand and steel was improved using the MICP process. The interface shear behavior between MICP-treated calcareous sand and steel was investigated experimentally under different cementation levels and normal stresses. With the increase of CaCO3 content, the peak shear strength increased, accompanied by obvious volume dilation, and the corresponding shear displacement was reduced. The shear band thickness was suppressed greatly from 22.2d50 to 4.4d50, and the percentage interface slip increased from 77.8% to 95.7%. With the increase of normal stress, the thickness of shear band increased and then remained stable. Both the peak and mobilized strength at 5 mm increased. MICP products changed the interface morphology and led to shear dilation of the sand sample, especially for high cementation levels. However, if the normal stress is large enough, the raised edges on the interface will be cut off and obvious contraction in the local layer near the interface appears. MICP cementation was found to have a remarkable effect on improving the cohesion of the calcareous sand–steel interface according to the Coulomb criterion.