Abstract:

Earthquakes are frequent in Northwest China, and the earthen sites in this region have been adversely affected by seismic activity for a long time. In order to study the dynamic characteristics of the earthen site soil treated by enzyme-induced calcium carbonate precipitation (EICP), earthen site soil samples with initial dry densities of 1.55, 1.65, and 1.75 g/cm³ were subjected to EICP treatment, and a control group without EICP treatment was set up. Dynamic triaxial tests under different confining pressures and vibration frequencies were carried out. The results show that under the same dynamic stress, the dynamic strain of the experimental group is smaller, the energy dissipation is less, and the damping ratio is smaller compared with the control group. After EICP treatment, the dynamic strain could be reduced with the increasing of the dry density, confining pressure, and vibration frequency but this effect diminishes in turn. The dynamic constitutive relation is in line with the Hardin model, and the influence of dry density, confining pressure, and vibration frequency on the model parameter a (dynamic elastic modulus) gradually decreases. Microstructure analysis show that after EICP treatment, calcium carbonate precipitates and adheres to the surface of soil particles, filling the pores, and cementing with the soil particles to form a dense structure, as a result, the strength of the soil structure is improved.

Key words: microbial mineralization, earthen ruins, dynamic constitutive relationship, dynamic modulus, damping ratio